Refine
Year of publication
Document Type
- Preprint (784)
- Article (664)
- Conference Proceeding (4)
- Working Paper (3)
- Part of Periodical (2)
- Review (2)
- Part of a Book (1)
- Report (1)
Has Fulltext
- yes (1461)
Keywords
- Heavy Ion Experiments (21)
- Hadron-Hadron Scattering (13)
- Hadron-Hadron scattering (experiments) (12)
- LHC (9)
- SARS-CoV-2 (7)
- Heavy-ion collision (6)
- Jets (6)
- Heavy-ion collisions (5)
- ALICE experiment (4)
- COVID19-NMR (4)
- Collective Flow (4)
- Quark-Gluon Plasma (4)
- conduct disorder (4)
- prostate cancer (4)
- sex differences (4)
- ALICE (3)
- COVID-19 (3)
- Diffraction (3)
- Heavy Ions (3)
- Heavy Quark Production (3)
- Jets and Jet Substructure (3)
- Relativistic heavy-ion collisions (3)
- Solution NMR spectroscopy (3)
- callous-unemotional traits (3)
- infection (3)
- inflammation (3)
- liver transplantation (3)
- neurodegeneration (3)
- pp collisions (3)
- risk factors (3)
- survival (3)
- 5′-UTR (2)
- Accelerators & Beams (2)
- Atmospheric chemistry (2)
- Atomic, Molecular & Optical (2)
- Ausländer, Rose (2)
- Beam Energy Scan (2)
- Beauty production (2)
- Bone density (2)
- Bukowina (2)
- Celan, Paul (2)
- Charm physics (2)
- Chiral Magnetic Effect (2)
- Collectivity (2)
- Conduct disorder (2)
- Correlation (2)
- Cryptic species (2)
- Diagnosis (2)
- Elastic scattering (2)
- Elliptic flow (2)
- Experimental nuclear physics (2)
- Experimental particle physics (2)
- Genetics (2)
- Germany (2)
- HCMV (2)
- HOD (2)
- Heavy-Ion Collision (2)
- Holmes tremor (2)
- Lepton-Nucleon Scattering (experiments) (2)
- NMR spectroscopy (2)
- Osteoporosis (2)
- Particle Correlations and Fluctuations (2)
- Particle and resonance production (2)
- Particle correlations and fluctuations (2)
- Pb–Pb collisions (2)
- Psychiatric disorders (2)
- Quark Gluon Plasma (2)
- Quarkonium (2)
- Shear viscosity (2)
- Single electrons (2)
- antisocial behavior (2)
- cabozantinib (2)
- cancer (2)
- cerebellum (2)
- cirrhosis (2)
- epidemiology (2)
- liver (2)
- palatal tremor (2)
- psychiatric comorbidity (2)
- resistant cell lines (2)
- squamous cell carcinoma (2)
- systematic biopsy (2)
- 3D electron diffraction (1)
- 5'-UTR (1)
- 5_SL4 (1)
- 900 GeV (1)
- ABCB1 (1)
- ACLF (1)
- ADHD (1)
- ALICE detector (1)
- ALK-rearranged NSCLC (1)
- ASCT (1)
- Accelerators & storage rings (1)
- Acute myeloid leukemia (1)
- Adhesion (1)
- Africa (1)
- Age determination by skeleton (1)
- Algorithms (1)
- Alternating Phase Focusing (1)
- American crocodile (1)
- Analysis and statistical methods (1)
- Anfang (1)
- Animal wings (1)
- Anti-kaon–nucleon physics (1)
- Anti-nuclei (1)
- Arc protein (1)
- Artificial intelligence (1)
- Atmospheric science (1)
- Atomic & molecular beams (1)
- Awareness campaign (1)
- B-slope (1)
- BMI (1)
- BPH (1)
- BPO (1)
- Bartonella grahamii (1)
- Bartonella henselae (1)
- Bartonella schoenbuchensis (1)
- Beam dynamics simulation (1)
- Beam energy scan (1)
- Beam loss (1)
- Biochemistry and chemical biology (1)
- Biogeochemistry (1)
- Biological markers (1)
- Blood (1)
- Bloodstream infections (1)
- Blowflies (1)
- Bone diseases, Metabolic (1)
- Boosted Jets (1)
- Brain (1)
- Brain tumor (1)
- C-reactive protein (1)
- CAKUT (1)
- CDK inhibitor (1)
- CHIP (1)
- CMS (1)
- CNS toxicity (1)
- CRPC (1)
- CT dual-energy computed tomography (1)
- CVD biomarker (1)
- Calliphoridae (1)
- Callous-unemotional traits (1)
- Calorimeters (1)
- Cancer check up (1)
- Carbapenem-resistente Gram-negative Bakterien (CRGN) (1)
- Carbapenemasen (1)
- Carbon cycle (1)
- Cardiovascular magnetic resonance (1)
- Cell membranes (1)
- Centrality Class (1)
- Centrality Selection (1)
- Charge fluctuations (1)
- Charge-transfer collisions (1)
- Charged-particle multiplicity (1)
- Charm quark spatial diffusion coefficient (1)
- Chemicals of emerging concern (1)
- Chemistry (1)
- Chemokine CCL2 (1)
- Chemokines (1)
- Chiral magnetic effect (1)
- Chocó rainforest (1)
- Chromatin and Epigenetics (1)
- Circular accelerators (1)
- Cirrhosis (1)
- Climate change (1)
- Climate-change impacts (1)
- Clinical genetics (1)
- Clinical variation (1)
- Coalescence (1)
- Cochlear implantation (1)
- Cochliopidae (1)
- Coevolution (1)
- Cold nuclear matter effects (1)
- Collective Flow, (1)
- Comparative genomics (1)
- Comparison with QCD (1)
- Cone-beam computed tomography (1)
- Conformational trapping (1)
- Continuous wave (1)
- Counterparty Credit Limits (1)
- Counterparty Risk (1)
- Course (1)
- Covid19-nmr (1)
- Critical point (1)
- Crocodylus acutus (1)
- DFT+MBD calculations (1)
- DNA damage response (1)
- Data processing methods (1)
- Data sharing (1)
- Death rates (1)
- Deuteron production (1)
- Devic disease (1)
- Devic syndrome (1)
- Di-hadron correlations (1)
- Diabetes (1)
- Diabetes mellitus (1)
- Direct reactions (1)
- Doderer, Heimito von (1)
- Dorsolateral prefrontal cortex (1)
- Dual-energy computed tomography (1)
- D’Amico classification (1)
- E. colo (1)
- ERK3 (1)
- EWSR1 (1)
- Ecosystem ecology (1)
- Ecotoxicology (1)
- Ecuador (1)
- Elderly (1)
- Electric stimulation (1)
- Electron-pion identification (1)
- Electronic transitions (1)
- Electroweak interaction (1)
- Emotion processing (1)
- Emotion regulation (1)
- Energy system design (1)
- England (1)
- Environmental quality (1)
- Epidemiological data (1)
- Everolimus (1)
- Evolution (1)
- Facial nerve (1)
- FemNAT-CD (1)
- Female adolescents (1)
- Femtoscopy (1)
- Fibre/foam sandwich radiator (1)
- Forensic entomology (1)
- Forensics (1)
- Forest ecology (1)
- Forward physics (1)
- Frailty (1)
- Franzobel (1)
- Fungi (1)
- Gene Regulation (1)
- Gene expression profiling (1)
- Gene fusion (1)
- General practitioners (1)
- German people (1)
- Gleason score (1)
- Gram negative bacteria (1)
- Groomed jet radius (1)
- Guanine nucleotide exchange factors (1)
- Guanosine triphosphatase (1)
- HBT (1)
- HOLEP (1)
- Hadron production (1)
- Hadron-Hadron Scattering Heavy (1)
- Hadron-hadron interactions (1)
- Hadronization (1)
- Hard Scattering (1)
- Health care workers (1)
- Heavy Ion Experiment (1)
- Heavy flavor production (1)
- Heavy flavour production (1)
- Heavy ion (1)
- Heavy ion collisions (1)
- Heavy ions (1)
- Heavy-flavor decay electron (1)
- Heavy-flavour decay muons (1)
- Heavy-flavour production (1)
- Hematopoietic stem cell transplantation (1)
- Hepatitis C virus (1)
- Herpes Simplex Virus Type 1 (HSV-1) (1)
- High-throughput screening (1)
- Higher moments (1)
- Hispanic people (1)
- Hyperons (1)
- Hypertension (1)
- IFN (1)
- IPSS (1)
- Image processing (computer-assisted) (1)
- Immune system (1)
- Immunogenetics (1)
- Immunology (1)
- In vitro selection (1)
- Inclusive spectra (1)
- Inflammation (1)
- Insula (1)
- Intensity interferometry (1)
- Intensive care units (1)
- Interference fragmentation function (1)
- Invariant Mass Distribution (1)
- Ionisation energy loss (1)
- Islam (1)
- Ixodes ricinus (1)
- J/ψ suppression (1)
- Jet Physics (1)
- Jet Substructure (1)
- Jet substructure (1)
- Kaonic nuclei (1)
- Kidney transplantation (1)
- Kiefernwald (1)
- Klaus (1)
- Klopstock, Friedrich Gottlieb (1)
- LVSPE (1)
- Large-scale integration of renewable power generation (1)
- Laurencia caspica (1)
- Laurencia crustiformans (1)
- Laurencia flexilis (1)
- Lectotype (1)
- Lektüre (1)
- Levelized cost of electricity (1)
- Library screening (1)
- Linear accelerator (1)
- Literatur (1)
- Litter (1)
- Liver diseases (1)
- Liver transplantation (1)
- Low & intermediate-energy accelerators (1)
- Low energy QCD (1)
- Low-dose ionizing radiation (1)
- Luciferase (1)
- MAPK6 (1)
- MN1 (1)
- MOLLI (1)
- MYC (1)
- Macrodomain (1)
- Market Design (1)
- Material budget (1)
- Mayröcker, Friederike (1)
- Medical history (1)
- Meldepflicht (1)
- Membrane protein (1)
- Methicillin-resistant Staphylococcus aureus (1)
- Methode (1)
- Microplastics (1)
- Micropollutants (1)
- Mid-rapidity (1)
- Minimum Bias (1)
- Mixture risk assessment (1)
- Molecular modelling (1)
- Monitoring (1)
- Monte Carlo (1)
- Morphometry (1)
- Multi-Parton Interactions (1)
- Multi-strange baryons (1)
- Multi-wire proportional drift chamber (1)
- Multiple parton interactions (1)
- Multivariate analysis (1)
- N-myc (1)
- NCAM (1)
- NMO-IgG (1)
- NOTCH (1)
- Nanobody (1)
- Net-charge correlations (1)
- Net-charge fluctuations (1)
- Neural network (1)
- Neuroepithelial (1)
- Neuromyelitis optica (1)
- Neurooncology (1)
- Neutropenia (1)
- Nietzsche, Friedrich (1)
- Nivolumab (1)
- Non-structural protein (1)
- Nonlinear beam dynamics (1)
- Non–small-cell lung cancer (1)
- Nuclear Physics (1)
- Nuclear modification factor (1)
- Nuclear reactions (1)
- Nuclear structure & decays (1)
- Nucleon induced nuclear reactions (1)
- Nucleus (1)
- OR time (1)
- Observational study (1)
- Ohelopapa (1)
- Oldest-old (1)
- Optimal mix of wind and solar PV (1)
- Osmundea (1)
- Osteoporotic fractures (1)
- Otorhinolaryngological (1)
- Outcome (1)
- Overall survival (1)
- PATZ1 (1)
- PD-L1 (1)
- PSA (1)
- PSA screening (1)
- PSA-Screening (1)
- PTDM (1)
- PYTHIA (1)
- Pandemic (1)
- Partial wave analysis (1)
- Particle and Resonance Production (1)
- Pb–Pb (1)
- Pediatric (1)
- Pediatric neuroimaging (1)
- Performance of High Energy Physics Detectors (1)
- Peucedano-Pinetum (1)
- Phage display (1)
- Phantoms (imaging) (1)
- Phosphorylation (1)
- Photon counting (1)
- Phylogenetic analysis (1)
- Phylogenetics (1)
- Phylogeny (1)
- Pigment Green 7 (1)
- Pinus sylvestris (1)
- Plant symbiosis (1)
- Plastics (1)
- Poetik (1)
- Poetologie (1)
- Polarization (1)
- Polymers (1)
- Post-transplant (1)
- Preventive medicine (1)
- Price Formation (1)
- Production Cross Section (1)
- Properties of Hadrons (1)
- Prostata-specific antigen (1)
- Prostataspezifisches Antigen (1)
- Prostatic neoplasms (1)
- Protein drugability (1)
- Proton (1)
- Proton-proton collisions (1)
- Proton–proton (1)
- Proton–proton collisions (1)
- Prävention (1)
- Pulmonary hypertension (1)
- Pyroleae (1)
- QCD (1)
- QGP (1)
- QSARs (1)
- Quark Deconfinement (1)
- Quark Production (1)
- RHIC (1)
- RNA (1)
- RNA genome (1)
- RNASolution-state NMR (1)
- Radiation detectors (1)
- Rapidity Range (1)
- Real-world data (1)
- Relativistic heavy ion physics (1)
- Renewable power generation (1)
- Resolution Parameter (1)
- Retrospective studies (1)
- Review (1)
- Ribosome display (1)
- Rietveld refinement (1)
- Risk drivers (1)
- River pollution (1)
- Rosenkranz, Moses (1)
- SAVI (1)
- SL1 (1)
- SL5b (1)
- SL5b + c (1)
- SL5c (1)
- SLC20A1 (1)
- SPSS (1)
- STAR (1)
- STING (1)
- Schmatz, Ferdinand (1)
- Schreiben (1)
- Schöpfung <Motiv> (1)
- Sequence alignment (1)
- Sex differences (1)
- Shell model (1)
- Single muons (1)
- Small molecules (1)
- SoftDrop (1)
- Solution NMR-spectroscopy (1)
- Speciesidentification (1)
- Spectroscopic factors & electromagnetic moments (1)
- Splitting function (1)
- Stenotrophomonas maltophilia (1)
- Strangeness (1)
- Structural biology and molecular biophysics (1)
- Surface waters (1)
- Systematic Uncertainty (1)
- Systemic Risk (1)
- T1 mapping (1)
- TLR7 (1)
- TLR8 (1)
- TOR inhibitor (1)
- TP53 mutation status (1)
- TR (1)
- Target screening (1)
- Target validation (1)
- Tateidae (1)
- Thermal model (1)
- Time Projection Chamber (1)
- Tomography (x-ray computed) (1)
- Tools and ressources (1)
- Tracking (1)
- Tradition (1)
- Transition radiation detector (1)
- Transverse momentum (1)
- Transversity (1)
- Treatment (1)
- Trigger (1)
- Tyumen (1)
- USP28 (1)
- Ungeheuer (1)
- Vector Boson Production (1)
- Vesicles (1)
- Vorsorgeuntersuchung (1)
- Voxel-based morphometry (1)
- Waldgesellschaft (1)
- Water framework directive (1)
- Welt <Motiv> (1)
- Werner (1)
- Westsibirisches Tiefland (1)
- Wiener, Oswald (1)
- Wissenschaft (1)
- Xenon-based gas mixture (1)
- aboveground biomass (1)
- accessory proteins (1)
- acute decompensation (1)
- acute-on-chronic liver failure (1)
- adolescence (1)
- aesthetics (1)
- age (1)
- aging (1)
- agonists (1)
- allocation (1)
- alteplase (1)
- amygdalin (1)
- antibiotic treatment (1)
- antimicrobial stewardship (1)
- aquaporin-4 (AQP4) antibody (1)
- artificial feeding (1)
- atypical MAPK kinase (1)
- autologous stem cell transplantation (1)
- biliary stricture (1)
- biodiversity (1)
- biogeographic legaciese (1)
- biopsy naïve (1)
- bladder exstrophy-epispadias complex (1)
- blood loss (1)
- bortezomib (1)
- brain structure (1)
- brainstem (1)
- c-MET (1)
- cabazitaxel (1)
- carbapenem resistance (1)
- carbapenem-resistant Gram-negative bacteria (CRGN) (1)
- carbapenemases (1)
- castration resistance (1)
- catheter (1)
- cell proliferation regulating inhibitor of protein phosphatase 2A (1)
- cell-free protein synthesis (1)
- cerebellar mutism (1)
- cerebrospinal fluid (1)
- chemotherapy (1)
- child (1)
- children and adolescents (1)
- chronosequence (1)
- classification (1)
- clinical features (1)
- clinical immunology (1)
- cloacal malformation (1)
- clonal dominance (1)
- clonal hematopoiesis (1)
- cognitive fluency (1)
- community violence exposure (1)
- complementary/alternative medicine (CAM) (1)
- complication (1)
- complications (1)
- computed tomography (1)
- connectivity (1)
- consensus (1)
- continuous rotation (1)
- copper phthalocyanine (1)
- corneas (1)
- covalent inhibitors (1)
- cytotoxic T cells (1)
- dE/dx (1)
- death rates (1)
- deferred treatment (1)
- delayed treatment (1)
- dendritic spines (1)
- depression (1)
- deswelling (1)
- detector (1)
- diffusion tensor imaging (DTI) (1)
- docetaxel (1)
- drug resistance (1)
- ectosomes (1)
- electron crystallography (1)
- emotion (1)
- endovascular thrombectomy (1)
- energy-dispersive x-ray spectroscopy (1)
- enterobacter infections; pseudomonas aeruginosa; epidemiology (1)
- epidermal growth factor receptor (1)
- epididymitis (1)
- epilepsy (1)
- exosomes (1)
- experimental results (1)
- extracellular vesicles (1)
- fMRI (1)
- females (1)
- forest classification (1)
- forest functional similarity (1)
- fourth (1)
- fragment screening (1)
- freshwater snails (1)
- functional genetics (1)
- fusion biopsy (1)
- gadolinium enhancing lesion (1)
- germ cell tumors (1)
- global change (1)
- graft (1)
- guidelines (1)
- habitat destruction (1)
- healthcare systems (1)
- heavy ion experiments (1)
- heavy-ion collisions (1)
- hematopoietic stem cells (1)
- hematopoietic stress (1)
- hemiboreal forest (1)
- hepatic encephalopathy (1)
- histological outcomes (1)
- histology (1)
- holotype (1)
- hotspot loci (1)
- immunosuppression (1)
- infection control (1)
- inpatient hospital admissions (1)
- integrins (1)
- interscalene brachial plexus block (1)
- intrinsically disordered region (1)
- inverse stage migration (1)
- keratoplasty (1)
- kidney (1)
- kidney formation (1)
- kinase inhibitors (1)
- land use (1)
- leukemia (1)
- local anesthetic (1)
- lockdown (1)
- longitudinally extensive transverse myelitis (1)
- loss (1)
- lymphocytes (1)
- magnetic resonance imaging (1)
- mandatory reporting system (1)
- marker (1)
- mechanical recanalization (1)
- medical informatics initiative (1)
- medical risk factors (1)
- medulloblastoma (1)
- medulloblastoma resection (1)
- memory consolidation (1)
- metabolic syndromes (1)
- metastatic prostate cancer (1)
- meter (1)
- microdeletions (1)
- microkeratome (1)
- microparticles (1)
- microvesicles (1)
- minimal information requirements (1)
- mortality (1)
- mortality risk (1)
- mtDNA (1)
- multi-drug resistance (1)
- multidrug resistance (1)
- multidrug-resistant Gram-negative bacteria (MRGN) (1)
- multiple sclerosis (1)
- multiresistente Gram-negativen Stäbchenbakterien (MRGN) (1)
- natural history collection (1)
- neuroblastoma (1)
- neurocritical care (1)
- neurodevelopmental (1)
- neurological outcome (1)
- neurosurgery (1)
- neurotropic virus (1)
- neurovascular bundle preservation (1)
- new combination (1)
- newly diagnosed glioblastoma (1)
- nitro-fatty acids (1)
- nivolumab (1)
- non-small cell lung cancer (1)
- nonstructural proteins (1)
- nymphs (1)
- oncomodulation (1)
- ovary (1)
- p+p collisions (1)
- p73 (1)
- palmitoylation (1)
- pancreatic cancer (1)
- pandemic (1)
- penile cancer (1)
- peri-implantitis (1)
- perioperative outcome (1)
- phylogenetic community distance (1)
- pneumocystis (1)
- poetry (1)
- portal hypertension (1)
- portosystemic shunt (1)
- posterior fossa masses (1)
- ppK − (1)
- proactive aggression (1)
- prognosis (1)
- prostate carcinoma cells (1)
- prostate volume (1)
- pseudomonas aeruginosa (1)
- quantum electrodynamics test (1)
- quark gluon plasma (1)
- radical prostatecomy (1)
- radical prostatectomy (1)
- radiotherapy (1)
- re-transplantation (1)
- reactive aggression (1)
- reactive oxygen species (1)
- reassembly (1)
- recurrent cholangitis (1)
- recurrent optic neuritis (1)
- renal transplantation (1)
- repeat biopsy (1)
- repeated (1)
- reproducibility (1)
- resilience (1)
- resistance (1)
- rhyme (1)
- rigor (1)
- risk factor progression (1)
- risk score (1)
- sepsis (1)
- sequential ALK-inhibitor therapy (1)
- sex (1)
- short-course antibiotic therapy (1)
- somatic mutations (1)
- spectra (1)
- spontaneous portosystemic shunt (1)
- standardization (1)
- storage rings (1)
- strong Coulomb field (1)
- structural proteins (1)
- suprapubic catheter (1)
- surface-based morphometry (1)
- surgical margin (1)
- targeted biopsy (1)
- targeted therapy (1)
- temozolomide (1)
- testis (1)
- third (1)
- thrombolysis (1)
- tivantinib (1)
- toxic hemisphere syndrome (1)
- tractography (1)
- transmission (1)
- transovarial transmission (1)
- transplantation (1)
- transrectal prostate biopsy (1)
- transstadial transmission (1)
- transurethral catheter (1)
- trees (1)
- tropical forests (1)
- tumor dissemination (1)
- university hospitals (1)
- unmethylated MGMT (1)
- urinary tract development (1)
- vector (1)
- waiting time (1)
- whole-genome sequencing (1)
- wild fire (1)
- x-ray techniques (1)
- zebrafish development (1)
- Öffentlichkeit (1)
- Übersetzung (1)
- ΔNp63 (1)
- Υ suppression (1)
- √sN N = 2.76 TeV (1)
Institute
- Physik (1161)
- Frankfurt Institute for Advanced Studies (FIAS) (1088)
- Informatik (951)
- Medizin (107)
- Geowissenschaften (20)
- Biowissenschaften (12)
- Institut für Ökologie, Evolution und Diversität (10)
- Biochemie und Chemie (9)
- Biochemie, Chemie und Pharmazie (8)
- Ernst Strüngmann Institut (8)
We present the first inclusive measurements of the invariant and SoftDrop jet mass in proton-proton collisions at s√=200 GeV at STAR. The measurements are fully corrected for detector effects, and reported differentially in both the jet transverse momentum and jet radius parameter. We compare the measurements to established leading-order Monte Carlo event generators and find that STAR-tuned PYTHIA-6 reproduces the data, while LHC tunes of PYTHIA-8 and HERWIG-7 do not agree with the data, providing further constraints on parameter tuning. Finally, we observe that SoftDrop grooming, for which the contribution of wide-angle non-perturbative radiation is suppressed, shifts the jet mass distributions into closer agreement with the partonic jet mass as determined by both PYTHIA-8 and a next-to-leading-logarithmic accuracy perturbative QCD calculation. These measurements complement recent LHC measurements in a different kinematic region, as well as establish a baseline for future jet mass measurements in heavy-ion collisions at RHIC.
We report a systematic measurement of cumulants, Cn, for net-proton, proton and antiproton, and correlation functions, κn, for proton and antiproton multiplicity distributions up to the fourth order in Au+Au collisions at sNN−−−√ = 7.7, 11.5, 14.5, 19.6, 27, 39, 54.4, 62.4 and 200 GeV. The Cn and κn are presented as a function of collision energy, centrality and kinematic acceptance in rapidity, y, and transverse momentum, pT. The data were taken during the first phase of the Beam Energy Scan (BES) program (2010 -- 2017) at the Relativistic Heavy Ion Collider (RHIC) facility. The measurements are carried out at midrapidity (|y|< 0.5) and transverse momentum 0.4 < pT < 2.0 GeV/c, using the STAR detector at RHIC. We observe a non-monotonic energy dependence (sNN−−−√ = 7.7 -- 62.4 GeV) of the net-proton C4/C2 with the significance of 3.1σ for the 0-5\% central Au+Au collisions. This is consistent with the expectations of critical fluctuations in a QCD-inspired model. Thermal and transport model calculations show a monotonic variation with sNN−−−√. For the multiparticle correlation functions, we observe significant negative values for a two-particle correlation function, κ2, of protons and antiprotons, which are mainly due to the effects of baryon number conservation. Furthermore, it is found that the four-particle correlation function, κ4, of protons plays a role in determining the energy dependence of proton C4/C1 below 19.6 GeV, which cannot be solely understood by the negative values of κ2 for protons.
We report a systematic measurement of cumulants, Cn, for net-proton, proton and antiproton multiplicity distributions, and correlation functions, κn, for proton and antiproton multiplicity distributions up to the fourth order in Au+Au collisions at sNN−−−√ = 7.7, 11.5, 14.5, 19.6, 27, 39, 54.4, 62.4 and 200 GeV. The Cn and κn are presented as a function of collision energy, centrality and kinematic acceptance in rapidity, y, and transverse momentum, pT. The data were taken during the first phase of the Beam Energy Scan (BES) program (2010 -- 2017) at the BNL Relativistic Heavy Ion Collider (RHIC) facility. The measurements are carried out at midrapidity (|y|< 0.5) and transverse momentum 0.4 < pT < 2.0 GeV/c, using the STAR detector at RHIC. We observe a non-monotonic energy dependence (sNN−−−√ = 7.7 -- 62.4 GeV) of the net-proton C4/C2 with the significance of 3.1σ for the 0-5\% central Au+Au collisions. This is consistent with the expectations of critical fluctuations in a QCD-inspired model. Thermal and transport model calculations show a monotonic variation with sNN−−−√. For the multiparticle correlation functions, we observe significant negative values for a two-particle correlation function, κ2, of protons and antiprotons, which are mainly due to the effects of baryon number conservation. Furthermore, it is found that the four-particle correlation function, κ4, of protons plays a role in determining the energy dependence of proton C4/C1 below 19.6 GeV, which cannot be understood by the effect of baryon number conservation.
We report high-precision measurements of the longitudinal double-spin asymmetry, 𝐴𝐿𝐿, for midrapidity inclusive jet and dijet production in polarized 𝑝𝑝 collisions at a center-of-mass energy of √𝑠=200 GeV. The new inclusive jet data are sensitive to the gluon helicity distribution, Δ𝑔(𝑥,𝑄2), for gluon momentum fractions in the range from 𝑥≃0.05 to 𝑥≃0.5, while the new dijet data provide further constraints on the 𝑥 dependence of Δ𝑔(𝑥,𝑄2). The results are in good agreement with previous measurements at √𝑠=200 GeV and with recent theoretical evaluations of prior world data. Our new results have better precision and thus strengthen the evidence that Δ𝑔(𝑥,𝑄2) is positive for 𝑥>0.05.
We report precision measurements of hypernuclei 3ΛH and 4ΛH lifetimes obtained from Au+Au collisions at \snn = 3.0\,GeV and 7.2\,GeV collected by the STAR experiment at RHIC, and the first measurement of 3ΛH and 4ΛH mid-rapidity yields in Au+Au collisions at \snn = 3.0\,GeV. The lifetimes are measured to be 221±15(stat.)±19(syst.)\,ps for 3ΛH and 218±6(stat.)±13(syst.)\,ps for 4ΛH. The pT-integrated yields of 3ΛH and 4ΛH are presented in different centrality and rapidity intervals. It is observed that the shape of the rapidity distribution of 4ΛH is different for 0--10\% and 10--50\% centrality collisions. Thermal model calculations, using the canonical ensemble for strangeness, describes the 3ΛH yield well, while underestimating the 4ΛH yield. Transport models, combining baryonic mean-field and coalescence (JAM) or utilizing dynamical cluster formation via baryonic interactions (PHQMD) for light nuclei and hypernuclei production, approximately describe the measured 3ΛH and 4ΛH yields.
We report precision measurements of hypernuclei 3ΛH and 4ΛH lifetimes obtained from Au+Au collisions at \snn = 3.0\,GeV and 7.2\,GeV collected by the STAR experiment at RHIC, and the first measurement of 3ΛH and 4ΛH mid-rapidity yields in Au+Au collisions at \snn = 3.0\,GeV. 3ΛH and 4ΛH, being the two simplest bound states composed of hyperons and nucleons, are cornerstones in the field of hypernuclear physics. Their lifetimes are measured to be 221±15(stat.)±19(syst.)\,ps for 3ΛH and 218±6(stat.)±13(syst.)\,ps for 4ΛH. The pT-integrated yields of 3ΛH and 4ΛH are presented in different centrality and rapidity intervals. It is observed that the shape of the rapidity distribution of 4ΛH is different for 0--10\% and 10--50\% centrality collisions. Thermal model calculations, using the canonical ensemble for strangeness, describes the 3ΛH yield well, while underestimating the 4ΛH yield. Transport models, combining baryonic mean-field and coalescence (JAM) or utilizing dynamical cluster formation via baryonic interactions (PHQMD) for light nuclei and hypernuclei production, approximately describe the measured 3ΛH and 4ΛH yields. Our measurements provide means to precisely assess our understanding of the fundamental baryonic interactions with strange quarks, which can impact our understanding of more complicated systems involving hyperons, such as the interior of neutron stars or exotic hypernuclei.
We report precision measurements of hypernuclei 3ΛH and 4ΛH lifetimes obtained from Au+Au collisions at \snn = 3.0\,GeV and 7.2\,GeV collected by the STAR experiment at RHIC, and the first measurement of 3ΛH and 4ΛH mid-rapidity yields in Au+Au collisions at \snn = 3.0\,GeV. 3ΛH and 4ΛH, being the two simplest bound states composed of hyperons and nucleons, are cornerstones in the field of hypernuclear physics. Their lifetimes are measured to be 221±15(stat.)±19(syst.)\,ps for 3ΛH and 218±6(stat.)±13(syst.)\,ps for 4ΛH. The pT-integrated yields of 3ΛH and 4ΛH are presented in different centrality and rapidity intervals. It is observed that the shape of the rapidity distribution of 4ΛH is different for 0--10\% and 10--50\% centrality collisions. Thermal model calculations, using the canonical ensemble for strangeness, describes the 3ΛH yield well, while underestimating the 4ΛH yield. Transport models, combining baryonic mean-field and coalescence (JAM) or utilizing dynamical cluster formation via baryonic interactions (PHQMD) for light nuclei and hypernuclei production, approximately describe the measured 3ΛH and 4ΛH yields. Our measurements provide means to precisely assess our understanding of the fundamental baryonic interactions with strange quarks, which can impact our understanding of more complicated systems involving hyperons, such as the interior of neutron stars or exotic hypernuclei.
The STAR collaboration presents jet substructure measurements related to both the momentum fraction and the opening angle within jets in p+p and Au+Au collisions at sNN−−−√=200 GeV. The substructure observables include SoftDrop groomed momentum fraction (zg), groomed jet radius (Rg), and subjet momentum fraction ((zSJ)) and opening angle ((θSJ)). The latter observable is introduced for the first time. Fully corrected subjet measurements are presented for p+p collisions and are compared to leading order Monte Carlo models. The subjet θSJ distributions reflect the jets leading opening angle and are utilized as a proxy for the resolution scale of the medium in Au+Au collisions. We compare data from Au+Au collisions to those from p+p which are embedded in minimum-bias Au+Au events in order to include the effects of detector smearing and the heavy-ion collision underlying event. The subjet observables are shown to be more robust to the background than zg and (Rg).
We observe no significant modifications of the subjet observables within the two highest-energy, back-to-back jets, resulting in a distribution of opening angles and the splittings that are vacuum-like. We also report measurements of the differential di-jet momentum imbalance (AJ) for jets of varying θg. We find no qualitative differences in energy loss signatures for varying angular scales in the range 0.1<θSJ<0.3, leading to the possible interpretation that energy loss in this population of high momentum di-jet pairs, is due to soft medium-induced gluon radiation from a single color-charge as it traverses the medium.
The STAR collaboration presents jet substructure measurements related to both the momentum fraction and the opening angle within jets in \pp and \AuAu collisions at \sqrtsn =200 GeV. The substructure observables include SoftDrop groomed momentum fraction (\zg), groomed jet radius (\rg), and subjet momentum fraction (\zsj) and opening angle (\tsj). The latter observable is introduced for the first time. Fully corrected subjet measurements are presented for \pp collisions and are compared to leading order Monte Carlo models. The subjet \tsj~distributions reflect the jets leading opening angle and are utilized as a proxy for the resolution scale of the medium in \AuAu collisions. We compare data from \AuAu collisions to those from \pp which are embedded in minimum-bias \AuAu events in order to include the effects of detector smearing and the heavy-ion collision underlying event. The subjet observables are shown to be more robust to the background than \zg~and \rg.
We observe no significant modifications of the subjet observables within the two highest-energy, back-to-back jets, resulting in a distribution of opening angles and the splittings that are vacuum-like. We also report measurements of the differential di-jet momentum imbalance (AJ) for jets of varying \tsj. We find no qualitative differences in energy loss signatures for varying angular scales in the range 0.1< \tsj <0.3, leading to the possible interpretation that energy loss in this population of high momentum di-jet pairs, is due to soft medium-induced gluon radiation from a single color-charge as it traverses the medium.
Density fluctuations near the QCD critical point can be probed via an intermittency analysis in relativistic heavy-ion collisions. We report the first measurement of intermittency in Au+Au collisions at sNN−−−√ = 7.7-200 GeV measured by the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The scaled factorial moments of identified charged hadrons are analyzed at mid-rapidity and within the transverse momentum phase space. We observe a power-law behavior of scaled factorial moments in Au+Au collisions and a decrease in the extracted scaling exponent (ν) from peripheral to central collisions. The ν is consistent with a constant for different collisions energies in the mid-central (10-40\%) collisions. Moreover, the ν in the 0-5\% most central Au+Au collisions exhibits a non-monotonic energy dependence that reaches a possible minimum around sNN−−−√ = 27 GeV. The physics implications on the QCD phase structure are discussed.
The longitudinal and transverse spin transfers to Λ (Λ¯¯¯¯) hyperons in polarized proton-proton collisions are expected to be sensitive to the helicity and transversity distributions, respectively, of (anti-)strange quarks in the proton, and to the corresponding polarized fragmentation functions. We report improved measurements of the longitudinal spin transfer coefficient, DLL, and the transverse spin transfer coefficient, DTT, to Λ and Λ¯¯¯¯ in polarized proton-proton collisions at s√ = 200 GeV by the STAR experiment at RHIC. The data set includes longitudinally polarized proton-proton collisions with an integrated luminosity of 52 pb−1, and transversely polarized proton-proton collisions with a similar integrated luminosity. Both data sets have about twice the statistics of previous results and cover a kinematic range of |ηΛ(Λ¯¯¯¯)| < 1.2 and transverse momentum pT,Λ(Λ¯¯¯¯) up to 8 GeV/c. We also report the first measurements of the hyperon spin transfer coefficients DLL and DTT as a function of the fractional jet momentum z carried by the hyperon, which can provide more direct constraints on the polarized fragmentation functions.
The longitudinal and transverse spin transfers to Λ (Λ¯¯¯¯) hyperons in polarized proton-proton collisions are expected to be sensitive to the helicity and transversity distributions, respectively, of (anti-)strange quarks in the proton, and to the corresponding polarized fragmentation functions. We report improved measurements of the longitudinal spin transfer coefficient, DLL, and the transverse spin transfer coefficient, DTT, to Λ and Λ¯¯¯¯ in polarized proton-proton collisions at s√ = 200 GeV by the STAR experiment at RHIC. The data set includes longitudinally polarized proton-proton collisions with an integrated luminosity of 52 pb−1, and transversely polarized proton-proton collisions with a similar integrated luminosity. Both data sets have about twice the statistics of previous results and cover a kinematic range of |ηΛ(Λ¯¯¯¯)| < 1.2 and transverse momentum pT,Λ(Λ¯¯¯¯) up to 8 GeV/c. We also report the first measurements of the hyperon spin transfer coefficients DLL and DTT as a function of the fractional jet momentum z carried by the hyperon, which can provide more direct constraints on the
The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process β-decay chains. These nuclei are attributed to the p and rp process.
For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections.
The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes.
Measurement of cold nuclear matter effects for inclusive J/ψ in p+Au collisions at √sNN = 200 GeV
(2022)
Measurement by the STAR experiment at RHIC of the cold nuclear matter (CNM) effects experienced by inclusive J/ψ at mid-rapidity in 0-100% p+Au collisions at √sNN = 200 GeV is presented. Such effects are quantified utilizing the nuclear modification factor, RpAu, obtained by taking a ratio of J/ψ yield in p+Au collisions to that in p+p collisions scaled by the number of binary nucleon-nucleon collisions. The differential J/ψ yield in both p+p and p+Au collisions is measured through the dimuon decay channel, taking advantage of the trigger capability provided by the Muon Telescope Detector in the RHIC 2015 run. Consequently, the J/ψ RpAu is derived within the transverse momentum (pT) range of 0 to 10 GeV/c. A suppression of approximately 30% is observed for pT < 2 GeV/c, while J/ψ RpAu becomes compatible with unity for pT greater than 3 GeV/c, indicating the J/ψ yield is minimally affected by the CNM effects at high pT. Comparison to a similar measurement from 0-20% central Au+Au collisions reveals that the observed strong J/ψ suppression above 3 GeV/c is mostly due to the hot medium effects, providing strong evidence for the formation of the quark-gluon plasma in these collisions. Several model calculations show qualitative agreement with the measured J/ψ RpAu, while their agreement with the J/ψ yields in p+p and p+Au collisions is worse.
A decisive experimental test of the Chiral Magnetic Effect (CME) is considered one of the major scientific goals at the Relativistic Heavy-Ion Collider (RHIC) towards understanding the nontrivial topological fluctuations of the Quantum Chromodynamics vacuum. In heavy-ion collisions, the CME is expected to result in a charge separation phenomenon across the reaction plane, whose strength could be strongly energy dependent. The previous CME searches have been focused on top RHIC energy collisions. In this Letter, we present a low energy search for the CME in Au+Au collisions at sNN−−−√=27 GeV. We measure elliptic flow scaled charge-dependent correlators relative to the event planes that are defined at both mid-rapidity |η|<1.0 and at forward rapidity 2.1<|η|<5.1. We compare the results based on the directed flow plane (Ψ1) at forward rapidity and the elliptic flow plane (Ψ2) at both central and forward rapidity. The CME scenario is expected to result in a larger correlation relative to Ψ1 than to Ψ2, while a flow driven background scenario would lead to a consistent result for both event planes. In 10-50\% centrality, results using three different event planes are found to be consistent within experimental uncertainties, suggesting a flow driven background scenario dominating the measurement. We obtain an upper limit on the deviation from a flow driven background scenario at the 95\% confidence level. This work opens up a possible road map towards future CME search with the high statistics data from the RHIC Beam Energy Scan Phase-II.
A decisive experimental test of the Chiral Magnetic Effect (CME) is considered one of the major scientific goals at the Relativistic Heavy-Ion Collider (RHIC) towards understanding the nontrivial topological fluctuations of the Quantum Chromodynamics vacuum. In heavy-ion collisions, the CME is expected to result in a charge separation phenomenon across the reaction plane, whose strength could be strongly energy dependent. The previous CME searches have been focused on top RHIC energy collisions. In this Letter, we present a low energy search for the CME in Au+Au collisions at sNN−−−√=27 GeV. We measure elliptic flow scaled charge-dependent correlators relative to the event planes that are defined at both mid-rapidity |η|<1.0 and at forward rapidity 2.1<|η|<5.1. We compare the results based on the directed flow plane (Ψ1) at forward rapidity and the elliptic flow plane (Ψ2) at both central and forward rapidity. The CME scenario is expected to result in a larger correlation relative to Ψ1 than to Ψ2, while a flow driven background scenario would lead to a consistent result for both event planes. In 10-50\% centrality, results using three different event planes are found to be consistent within experimental uncertainties, suggesting a flow driven background scenario dominating the measurement. We obtain an upper limit on the deviation from a flow driven background scenario at the 95\% confidence level. This work opens up a possible road map towards future CME search with the high statistics data from the RHIC Beam Energy Scan Phase-II.
We report the beam energy and collision centrality dependence of fifth and sixth order cumulants (C5, C6) and factorial cumulants (κ5, κ6) of net-proton and proton distributions, from sNN−−−−√=3−200 GeV Au+Au collisions at RHIC. The net-proton cumulant ratios generally follow the hierarchy expected from QCD thermodynamics, except for the case of collisions at sNN−−−−√ = 3 GeV. C6/C2 for 0-40\% centrality collisions is increasingly negative with decreasing sNN−−−−√, while it is positive for the lowest sNN−−−−√ studied. These observed negative signs are consistent with QCD calculations (at baryon chemical potential, μB≤ 110 MeV) that include a crossover quark-hadron transition. In addition, for sNN−−−−√≥ 11.5 GeV, the measured proton κn, within uncertainties, does not support the two-component shape of proton distributions that would be expected from a first-order phase transition. Taken in combination, the hyper-order proton number fluctuations suggest that the structure of QCD matter at high baryon density, μB∼750 MeV (sNN−−−−√ = 3 GeV) is starkly different from those at vanishing μB∼20MeV (sNN−−−−√ = 200 GeV and higher).
We report on measurements of sequential Υ suppression in Au+Au collisions at sNN−−−√ = 200 GeV with the STAR detector at the Relativistic Heavy Ion Collider (RHIC) through both the dielectron and dimuon decay channels. In the 0-60% centrality class, the nuclear modification factors (RAA), which quantify the level of yield suppression in heavy-ion collisions compared to p+p collisions, for Υ(1S) and Υ(2S) are 0.40±0.03 (stat.)±0.03 (sys.)±0.09 (norm.) and 0.26±0.08 (stat.)±0.02 (sys.)±0.06 (norm.), respectively, while the upper limit of the Υ(3S) RAA is 0.17 at a 95% confidence level. This provides experimental evidence that the Υ(3S) is significantly more suppressed than the Υ(1S) at RHIC. The level of suppression for Υ(1S) is comparable to that observed at the much higher collision energy at the Large Hadron Collider. These results point to the creation of a medium at RHIC whose temperature is sufficiently high to strongly suppress excited Υ states.
We report new STAR measurements of the single-spin asymmetries 𝐴𝐿 for 𝑊+ and 𝑊− bosons produced in polarized proton-proton collisions at √𝑠=510 GeV as a function of the decay-positron and decay-electron pseudorapidity. The data were obtained in 2013 and correspond to an integrated luminosity of 250 pb−1. The results are combined with previous results obtained with 86 pb−1. A comparison with theoretical expectations based on polarized lepton-nucleon deep-inelastic scattering and prior polarized proton-proton data suggests a difference between the ¯𝑢 and ¯𝑑 quark helicity distributions for 0.05<𝑥<0.25. In addition, we report new results for the double-spin asymmetries 𝐴𝐿𝐿 for 𝑊±, as well as 𝐴𝐿 for 𝑍/𝛾* production and subsequent decay into electron-positron pairs.
Transverse spin transfer to Λ and ¯Λ hyperons in polarized proton-proton collisions at √𝑠=200 GeV
(2018)
The transverse spin transfer from polarized protons to Λ and Λ¯ hyperons is expected to provide sensitivity to the transversity distribution of the nucleon and to the transversely polarized fragmentation functions. We report the first measurement of the transverse spin transfer to Λ and Λ¯ along the polarization direction of the fragmenting quark, DTT, in transversely polarized proton-proton collisions at s√=200GeV with the STAR detector at RHIC. The data correspond to an integrated luminosity of 18pb−1 and cover the pseudorapidity range |η|<1.2 and transverse momenta pT up to 8GeV/c. The dependence on pT and η are presented. The DTT results are found to be comparable with a model prediction, and are also consistent with zero within uncertainties.
We report a new measurement of the production of electrons from open heavy-flavor hadron decays (HFEs) at mid-rapidity (|y| < 0.7) in Au+Au collisions at √sNN = 200 GeV. Invariant yields of HFEs are measured for the transverse momentum range of 3.5 < pT < 9 GeV/c in various configurations of the collision geometry. The HFE yields in head-on Au+Au collisions are suppressed by approximately a factor of 2 compared to that in p + p collisions scaled by the average number of binary collisions, indicating strong interactions between heavy quarks and the hot and dense medium created in heavy-ion collisions. Comparison of these results with models provides additional tests of theoretical calculations of heavy quark energy loss in the quark-gluon plasma.
Elliptic flow of heavy-flavor decay electrons in Au+Au collisions at √sNN = 27 and 54.4 GeV at RHIC
(2023)
We report on new measurements of elliptic flow (v2) of electrons from heavy-flavor hadron decays at mid-rapidity (|y|<0.8) in Au+Au collisions at sNN−−−√ = 27 and 54.4 GeV from the STAR experiment. Heavy-flavor decay electrons (eHF) in Au+Au collisions at sNN−−−√ = 54.4 GeV exhibit a non-zero v2 in the transverse momentum (pT) region of pT< 2 GeV/c with the magnitude comparable to that at sNN−−−√=200 GeV. The measured eHF v2 at 54.4 GeV is also consistent with the expectation of their parent charm hadron v2 following number-of-constituent-quark scaling as other light and strange flavor hadrons at this energy. These suggest that charm quarks gain significant collectivity through the evolution of the QCD medium and may reach local thermal equilibrium in Au+Au collisions at sNN−−−√=54.4 GeV. The measured eHF v2 in Au+Au collisions at sNN−−−√= 27 GeV is consistent with zero within large uncertainties. The energy dependence of v2 for different flavor particles (π,ϕ,D0/eHF) shows an indication of quark mass hierarchy in reaching thermalization in high-energy nuclear collisions.
We report a new measurement of the production of electrons from open heavy-flavor hadron decays (HFEs) at mid-rapidity (|y|< 0.7) in Au+Au collisions at sNN−−−√=200 GeV. Invariant yields of HFEs are measured for the transverse momentum range of 3.5<pT<9 GeV/c in various configurations of the collision geometry. The HFE yields in head-on Au+Au collisions are suppressed by approximately a factor of 2 compared to that in p+p collisions scaled by the average number of binary collisions, indicating strong interactions between heavy quarks and the hot and dense medium created in heavy-ion collisions. Comparison of these results with models provides additional tests of theoretical calculations of heavy quark energy loss in the quark-gluon plasma.
We report a new measurement of the production of electrons from open heavy-flavor hadron decays (HFEs) at mid-rapidity (|y|< 0.7) in Au+Au collisions at sNN−−−√=200 GeV. Invariant yields of HFEs are measured for the transverse momentum range of 3.5<pT<9 GeV/c in various configurations of the collision geometry. The HFE yields in head-on Au+Au collisions are suppressed by approximately a factor of 2 compared to that in p+p collisions scaled by the average number of binary collisions, indicating strong interactions between heavy quarks and the hot and dense medium created in heavy-ion collisions. Comparison of these results with models provides additional tests of theoretical calculations of heavy quark energy loss in the quark-gluon plasma.
We report on the measurements of directed flow v1 and elliptic flow v2 for hadrons (π±, K ±, K0 S , p, φ, Λ and ) from Au+Au collisions at √sN N = 3 GeV and v2 for (π±, K ±, p and p) at 27 and 54.4 GeV with the STAR experiment. While at the two higher energy midcentral collisions the numberof-constituent-quark (NCQ) scaling holds, at 3 GeV the v2 at midrapidity is negative for all hadrons and the NCQ scaling is absent. In addition, the v1 slopes at midrapidity for almost all observed hadrons are found to be positive, implying dominant repulsive baryonic interactions. The features of negative v2 and positive v1 slope at 3 GeV can be reproduced with a baryonic mean-field in transport model calculations. These results imply that the medium in such collisions is likely characterized by baryonic interactions.
Density fluctuations near the QCD critical point can be probed via an intermittency analysis in relativistic heavy-ion collisions. We report the first measurement of intermittency in Au+Au collisions at √sNN = 7.7-200 GeV measured by the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The scaled factorial moments of identified charged hadrons are analyzed at mid-rapidity and within the transverse momentum phase space. We observe a power-law behavior of scaled factorial moments in Au+Au collisions and a decrease in the extracted scaling exponent (ν) from peripheral to central collisions. The ν is consistent with a constant for different collisions energies in the mid-central (10-40%) collisions. Moreover, the ν in the 0-5% most central Au+Au collisions exhibits a non-monotonic energy dependence that reaches a minimum around √sNN = 27 GeV. The physics implications on the QCD phase structure are discussed.
We report on the measurement of the Central Exclusive Production of charged particle pairs h+h− (h = π, K, p) with the STAR detector at RHIC in proton-proton collisions at √s = 200 GeV. The charged particle pairs produced in the reaction pp → p′ + h+h− + p′ are reconstructed from the tracks in the central detector and identified using the specific energy loss and the time of flight method, while the forward-scattered protons are measured in the Roman Pot system. Exclusivity of the event is guaranteed by requiring the transverse momentum balance of all four final-state particles. Differential cross sections are measured as functions of observables related to the central hadronic final state and to the forward-scattered protons. They are measured in a fiducial region corresponding to the acceptance of the STAR detector and determined by the central particles’ transverse momenta and pseudorapidities as well as by the forward-scattered protons’ momenta. This fiducial region roughly corresponds to the square of the four-momentum transfers at the proton vertices in the range 0.04 GeV2 < −t1, −t2 < 0.2 GeV2, invariant masses of the charged particle pairs up to a few GeV and pseudorapidities of the centrally-produced hadrons in the range |η| < 0.7. The measured cross sections are compared to phenomenological predictions based on the Double Pomeron Exchange (DPE) model. Structures observed in the mass spectra of π+π− and K+K− pairs are consistent with the DPE model, while angular distributions of pions suggest a dominant spin-0 contribution to π+π− production. For π+π− production, the fiducial cross section is extrapolated to the Lorentz-invariant region, which allows decomposition of the invariant mass spectrum into continuum and resonant contributions. The extrapolated cross section is well described by the continuum production and at least three resonances, the f0(980), f2(1270) and f0(1500), with a possible small contribution from the f0(1370). Fits to the extrapolated differential cross section as a function of t1 and t2 enable extraction of the exponential slope parameters in several bins of the invariant mass of π+π− pairs. These parameters are sensitive to the size of the interaction region.
The STAR Collaboration reports measurements of the transverse single-spin asymmetry (TSSA) of inclusive 𝜋0 at center-of-mass energies (√𝑠) of 200 GeV and 500 GeV in transversely polarized proton-proton collisions in the pseudo-rapidity region 2.7 to 4.0. The results at the two different energies show a continuous increase of the TSSA with Feynman-𝑥, and, when compared to previous measurements, no dependence on √𝑠 from 19.4 GeV to 500 GeV is found. To investigate the underlying physics leading to this large TSSA, different topologies have been studied. 𝜋0 with no nearby particles tend to have a higher TSSA than inclusive 𝜋0. The TSSA for inclusive electromagnetic jets, sensitive to the Sivers effect in the initial state, is substantially smaller, but shows the same behavior as the inclusive 𝜋0 asymmetry as a function of Feynman-𝑥. To investigate final-state effects, the Collins asymmetry of 𝜋0 inside electromagnetic jets has been measured. The Collins asymmetry is analyzed for its dependence on the 𝜋0 momentum transverse to the jet thrust axis and its dependence on the fraction of jet energy carried by the 𝜋0. The asymmetry was found to be small in each case for both center-of-mass energies. All the measurements are compared to QCD-based theoretical calculations for transverse-momentum-dependent parton distribution functions and fragmentation functions. Some discrepancies are found, which indicates new mechanisms might be involved.
We report the first multi-differential measurements of strange hadrons of K −, φ and − yields as well as the ratios of φ/K − and φ/− in Au+Au collisions at √sNN = 3 GeV with the STAR experiment fixed target configuration at RHIC. The φ mesons and − hyperons are measured through hadronic decay channels, φ → K + K − and Ξ− → Λπ−. Collision centrality and rapidity dependence of the transverse momentum spectra for these strange hadrons are presented. The 4π yields and ratios are compared to thermal model and hadronic transport model predictions. At this collision energy, thermal model with grand canonical ensemble (GCE) under-predicts the φ/K − and φ/− ratios while the result of canonical ensemble (CE) calculations reproduce φ/K −, with the correlation length rc ∼ 2.7 fm, and φ/−, rc ∼ 4.2 fm, for the 0-10% central collisions. Hadronic transport models including high mass resonance decays could also describe the ratios. While thermal calculations with GCE work well for strangeness production in high energy collisions, the change to CE at 3 GeV implies a rather different medium property at high baryon density.
Elliptic flow of heavy-flavor decay electrons in Au+Au collisions at √sNN = 27 and 54.4 GeV at RHIC
(2023)
We report on new measurements of elliptic flow (v2) of electrons from heavy-flavor hadron decays at mid-rapidity (|y|<0.8) in Au+Au collisions at sNN−−−√ = 27 and 54.4 GeV from the STAR experiment. Heavy-flavor decay electrons (eHF) in Au+Au collisions at sNN−−−√ = 54.4 GeV exhibit a non-zero v2 in the transverse momentum (pT) region of pT< 2 GeV/c with the magnitude comparable to that at sNN−−−√=200 GeV. The measured eHF v2 at 54.4 GeV is also consistent with the expectation of their parent charm hadron v2 following number-of-constituent-quark scaling as other light and strange flavor hadrons at this energy. These suggest that charm quarks gain significant collectivity through the evolution of the QCD medium and may reach local thermal equilibrium in Au+Au collisions at sNN−−−√=54.4 GeV. The measured eHF v2 in Au+Au collisions at sNN−−−√= 27 GeV is consistent with zero within large uncertainties. The energy dependence of v2 for different flavor particles (π,ϕ,D0/eHF) shows an indication of quark mass hierarchy in reaching thermalization in high-energy nuclear collisions.
We report the measurement of K∗0 meson at midrapidity (|y|< 1.0) in Au+Au collisions at sNN−−−√~=~7.7, 11.5, 14.5, 19.6, 27 and 39 GeV collected by the STAR experiment during the RHIC beam energy scan (BES) program. The transverse momentum spectra, yield, and average transverse momentum of K∗0 are presented as functions of collision centrality and beam energy. The K∗0/K yield ratios are presented for different collision centrality intervals and beam energies. The K∗0/K ratio in heavy-ion collisions are observed to be smaller than that in small system collisions (e+e and p+p). The K∗0/K ratio follows a similar centrality dependence to that observed in previous RHIC and LHC measurements. The data favor the scenario of the dominance of hadronic re-scattering over regeneration for K∗0 production in the hadronic phase of the medium.
We report a measurement of cumulants and correlation functions of event-by-event proton multiplicity distributions from fixed-target Au+Au collisions at sNN−−−√ = 3 GeV measured by the STAR experiment. Protons are identified within the rapidity (y) and transverse momentum (pT) region −0.9<y<0 and 0.4<pT<2.0 GeV/c in the center-of-mass frame. A systematic analysis of the proton cumulants and correlation functions up to sixth-order as well as the corresponding ratios as a function of the collision centrality, pT, and y are presented. The effect of pileup and initial volume fluctuations on these observables and the respective corrections are discussed in detail. The results are compared to calculations from the hadronic transport UrQMD model as well as a hydrodynamic model. In the most central 5\% collisions, the value of proton cumulant ratio C4/C2 is negative, drastically different from the values observed in Au+Au collisions at higher energies. Compared to model calculations including Lattice QCD, a hadronic transport model, and a hydrodynamic model, the strong suppression in the ratio of C4/C2 at 3 GeV Au+Au collisions indicates an energy regime dominated by hadronic interactions.
A decisive experimental test of the Chiral Magnetic Effect (CME) is considered one of the major scientific goals at the Relativistic Heavy-Ion Collider (RHIC) towards understanding the nontrivial topological fluctuations of the Quantum Chromodynamics vacuum. In heavy-ion collisions, the CME is expected to result in a charge separation phenomenon across the reaction plane, whose strength could be strongly energy dependent. The previous CME searches have been focused on top RHIC energy collisions. In this Letter, we present a low energy search for the CME in Au+Au collisions at sNN−−−√=27 GeV. We measure elliptic flow scaled charge-dependent correlators relative to the event planes that are defined at both mid-rapidity |η|<1.0 and at forward rapidity 2.1<|η|<5.1. We compare the results based on the directed flow plane (Ψ1) at forward rapidity and the elliptic flow plane (Ψ2) at both central and forward rapidity. The CME scenario is expected to result in a larger correlation relative to Ψ1 than to Ψ2, while a flow driven background scenario would lead to a consistent result for both event planes. In 10-50\% centrality, results using three different event planes are found to be consistent within experimental uncertainties, suggesting a flow driven background scenario dominating the measurement. We obtain an upper limit on the deviation from a flow driven background scenario at the 95\% confidence level. This work opens up a possible road map towards future CME search with the high statistics data from the RHIC Beam Energy Scan Phase-II.
Azimuthal anisotropy measurement of (multi-)strange hadrons in Au+Au collisions at √sNN = 54.4 GeV
(2023)
Azimuthal anisotropy of produced particles is one of the most important observables used to access the collective properties of the expanding medium created in relativistic heavy-ion collisions. In this paper, we present second (v2) and third (v3) order azimuthal anisotropies of K0S, ϕ, Λ, Ξ and Ω at mid-rapidity (|y|<1) in Au+Au collisions at sNN−−−√ = 54.4 GeV measured by the STAR detector. The v2 and v3 are measured as a function of transverse momentum and centrality. Their energy dependence is also studied. v3 is found to be more sensitive to the change in the center-of-mass energy than v2. Scaling by constituent quark number is found to hold for v2 within 10%. This observation could be evidence for the development of partonic collectivity in 54.4 GeV Au+Au collisions. Differences in v2 and v3 between baryons and anti-baryons are presented, and ratios of v3/v3/22 are studied and motivated by hydrodynamical calculations. The ratio of v2 of ϕ mesons to that of anti-protons (v2(ϕ)/v2(p¯)) shows centrality dependence at low transverse momentum, presumably resulting from the larger effects from hadronic interactions on anti-proton v2.
Measurements of mass and Λ binding energy of 4ΛH and 4ΛHe in Au+Au collisions at sNN−−−√=3 GeV are presented, with an aim to address the charge symmetry breaking (CSB) problem in hypernuclei systems with atomic number A = 4. The Λ binding energies are measured to be 2.22±0.06(stat.)±0.14(syst.) MeV and 2.38±0.13(stat.)±0.12(syst.) MeV for 4ΛH and 4ΛHe, respectively. The measured Λ binding-energy difference is 0.16±0.14(stat.)±0.10(syst.) MeV for ground states. Combined with the γ-ray transition energies, the binding-energy difference for excited states is −0.16±0.14(stat.)±0.10(syst.) MeV, which is negative and comparable to the value of the ground states within uncertainties. These new measurements on the Λ binding-energy difference in A = 4 hypernuclei systems are consistent with the theoretical calculations that result in ΔB4Λ(1+exc)≈−ΔB4Λ(0+g.s.)<0 and present a new method for the study of CSB effect using relativistic heavy-ion collisions.
Measurements of mass and Λ binding energy of 4ΛH and 4ΛHe in Au+Au collisions at sNN−−−√=3 GeV are presented, with an aim to address the charge symmetry breaking (CSB) problem in hypernuclei systems with atomic number A = 4. The Λ binding energies are measured to be 2.22±0.06(stat.)±0.14(syst.) MeV and 2.38±0.13(stat.)±0.12(syst.) MeV for 4ΛH and 4ΛHe, respectively. The measured Λ binding-energy difference is 0.16±0.14(stat.)±0.10(syst.) MeV for ground states. Combined with the γ-ray transition energies, the binding-energy difference for excited states is −0.16±0.14(stat.)±0.10(syst.) MeV, which is negative and comparable to the value of the ground states within uncertainties. These new measurements on the Λ binding-energy difference in A = 4 hypernuclei systems are consistent with the theoretical calculations that result in ΔB4Λ(1+exc)≈−ΔB4Λ(0+g.s.)<0 and present a new method for the study of CSB effect using relativistic heavy-ion collisions.
Measurement of inclusive J/ψ polarization in p + p collisions at √s=200 GeV by the STAR experiment
(2020)
We report on new measurements of inclusive 𝐽/𝜓 polarization at midrapidity in 𝑝+𝑝 collisions at √𝑠=200 GeV by the STAR experiment at the Relativistic Heavy Ion Collider. The polarization parameters, 𝜆𝜃, 𝜆𝜙, and 𝜆𝜃𝜙, are measured as a function of transverse momentum (𝑝T) in both the helicity and Collins-Soper (CS) reference frames within 𝑝T<10 GeV/𝑐. Except for 𝜆𝜃 in the CS frame at the highest measured 𝑝T, all three polarization parameters are consistent with 0 in both reference frames without any strong 𝑝T dependence. Several model calculations are compared with data, and the one using the Color Glass Condensate effective field theory coupled with nonrelativistic QCD gives the best overall description of the experimental results, even though other models cannot be ruled out due to experimental uncertainties.
Partons traversing the strongly interacting medium produced in heavy-ion collisions are expected to lose energy depending on their color charge and mass. We measure the nuclear modification factors for charm- and bottom-decay electrons, defined as the ratio of yields, scaled by the number of binary nucleon-nucleon collisions, in sNN−−−√ = 200 GeV Au+Au collisions to p+p collisions (RAA), or in central to peripheral Au+Au collisions (RCP). We find the bottom-decay electron RAA and RCP to be significantly higher than that of charm-decay electrons. Model calculations including mass-dependent parton energy loss in a strongly coupled medium are consistent with the measured data. These observations provide clear evidence of mass ordering of charm and bottom quark energy loss when traversing through the strongly coupled medium created in heavy-ion collisions.
Partons traversing the strongly interacting medium produced in heavy-ion collisions are expected to lose energy depending on their color charge and mass. We measure the nuclear modification factors for charm- and bottom-decay electrons, defined as the ratio of yields, scaled by the number of binary nucleon-nucleon collisions, in sNN−−−√ = 200 GeV Au+Au collisions to p+p collisions (RAA), or in central to peripheral Au+Au collisions (RCP). We find the bottom-decay electron RAA and RCP to be significantly higher than that of charm-decay electrons. Model calculations including mass-dependent parton energy loss in a strongly coupled medium are consistent with the measured data. These observations provide clear evidence of mass ordering of charm and bottom quark energy loss when traversing through the strongly coupled medium created in heavy-ion collisions.
Partons traversing the strongly interacting medium produced in heavy-ion collisions are expected to lose energy depending on their color charge and mass. We measure the nuclear modification factors for charm- and bottom-decay electrons, defined as the ratio of yields, scaled by the number of binary nucleon-nucleon collisions, in sNN−−−√ = 200 GeV Au+Au collisions to p+p collisions (RAA), or in central to peripheral Au+Au collisions (RCP). We find the bottom-decay electron RAA and RCP to be significantly higher than that of charm-decay electrons. Model calculations including mass-dependent parton energy loss in a strongly coupled medium are consistent with the measured data. These observations provide clear evidence of mass ordering of charm and bottom quark energy loss when traversing through the strongly coupled medium created in heavy-ion collisions.
Partons traversing the strongly interacting medium produced in heavy-ion collisions are expected to lose energy depending on their color charge and mass. We measure the nuclear modification factors for charm- and bottom-decay electrons, defined as the ratio of yields, scaled by the number of binary nucleon-nucleon collisions, in sNN−−−√ = 200 GeV Au+Au collisions to p+p collisions (RAA), or in central to peripheral Au+Au collisions (RCP). We find the bottom-decay electron RAA and RCP to be significantly higher than that of charm-decay electrons. Model calculations including mass-dependent parton energy loss in a strongly coupled medium are consistent with the measured data. These observations provide clear evidence of mass ordering of charm and bottom quark energy loss when traversing through the strongly coupled medium created in heavy-ion collisions.
Partons traversing the strongly interacting medium produced in heavy-ion collisions are expected to lose energy depending on their color charge and mass. We measure the nuclear modification factors for charm- and bottom-decay electrons, defined as the ratio of yields, scaled by the number of binary nucleon-nucleon collisions, in sNN−−−√ = 200 GeV Au+Au collisions to p+p collisions (RAA), or in central to peripheral Au+Au collisions (RCP). We find the bottom-decay electron RAA and RCP to be significantly higher than that of charm-decay electrons. Model calculations including mass-dependent parton energy loss in a strongly coupled medium are consistent with the measured data. These observations provide clear evidence of mass ordering of charm and bottom quark energy loss when traversing through the strongly coupled medium created in heavy-ion collisions.
We report results on an elastic cross section measurement in proton-proton collisions at a center-of-mass energy s√=510 GeV, obtained with the Roman Pot setup of the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The elastic differential cross section is measured in the four-momentum transfer squared range 0.23≤−t≤0.67 GeV2. We find that a constant slope B does not fit the data in the aforementioned t range, and we obtain a much better fit using a second-order polynomial for B(t). The t dependence of B is determined using six subintervals of t in the STAR measured t range, and is in good agreement with the phenomenological models. The measured elastic differential cross section dσ/dt agrees well with the results obtained at s√=546~GeV for proton--antiproton collisions by the UA4 experiment. We also determine that the integrated elastic cross section within the STAR t-range is σfidel=462.1±0.9(stat.)±1.1(syst.)±11.6(scale) μb.
We report results on an elastic cross section measurement in proton-proton collisions at a center-of-mass energy s√=510 GeV, obtained with the Roman Pot setup of the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The elastic differential cross section is measured in the four-momentum transfer squared range 0.23≤−t≤0.67 GeV2. We find that a constant slope B does not fit the data in the aforementioned t range, and we obtain a much better fit using a second-order polynomial for B(t). The t dependence of B is determined using six subintervals of t in the STAR measured t range, and is in good agreement with the phenomenological models. The measured elastic differential cross section dσ/dt agrees well with the results obtained at s√=546 GeV for proton--antiproton collisions by the UA4 experiment. We also determine that the integrated elastic cross section within the STAR t-range is σfidel=462.1±0.9(stat.)±1.1(syst.)±11.6(scale) μb.
We report results on an elastic cross section measurement in proton-proton collisions at a center-of-mass energy s√=510 GeV, obtained with the Roman Pot setup of the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The elastic differential cross section is measured in the four-momentum transfer squared range 0.23≤−t≤0.67 GeV2. We find that a constant slope B does not fit the data in the aforementioned t range, and we obtain a much better fit using a second-order polynomial for B(t). The t dependence of B is determined using six subintervals of t in the STAR measured t range, and is in good agreement with the phenomenological models. The measured elastic differential cross section dσ/dt agrees well with the results obtained at s√=546 GeV for proton--antiproton collisions by the UA4 experiment. We also determine that the integrated elastic cross section within the STAR t-range is σfidel=462.1±0.9(stat.)±1.1(syst.)±11.6(scale) μb.
We measure triangular flow relative to the reaction plane at 3 GeV center-of-mass energy in Au+Au collisions at the BNL Relativistic Heavy Ion Collider. A significant v3 signal for protons is observed, which increases for higher rapidity, higher transverse momentum, and more peripheral collisions. The triangular flow is essentially rapidity-odd with a slope at mid-rapidity, dv3/dy|(y=0), opposite in sign compared to the slope for directed flow. No significant v3 signal is observed for charged pions and kaons. Comparisons with models suggest that a mean field potential is required to describe these results, and that the triangular shape of the participant nucleons is the result of stopping and nuclear geometry.
Jet-hadron correlations with respect to the event plane in √sNN = 200 GeV Au+Au collisions in STAR
(2024)
Angular distributions of charged particles relative to jet axes are studied in sNN−−−√ = 200 GeV Au+Au collisions as a function of the jet orientation with respect to the event plane. This differential study tests the expected path-length dependence of energy loss experienced by a hard-scattered parton as it traverses the hot and dense medium formed in heavy-ion collisions. A second-order event plane is used in the analysis as an experimental estimate of the reaction plane formed by the collision impact parameter and the beam direction. Charged-particle jets with 15<pT,jet< 20 and 20<pT,jet< 40 GeV/c were reconstructed with the anti-kT algorithm with radius parameter setting of (R=0.4) in the 20-50\% centrality bin to maximize the initial-state eccentricity of the interaction region. The reaction plane fit method is implemented to remove the flow-modulated background with better precision than prior methods. Yields and widths of jet-associated charged-hadron distributions are extracted in three angular bins between the jet axis and the event plane. The event-plane (EP) dependence is further quantified by ratios of the associated yields in different EP bins. No dependence on orientation of the jet axis with respect to the event plane is seen within the uncertainties in the kinematic regime studied. This finding is consistent with a similar experimental observation by ALICE in sNN−−−√ = 2.76 TeV Pb+Pb collision data.
The differential cross section for 𝑍0 production, measured as a function of the boson’s transverse momentum (𝑝T), provides important constraints on the evolution of the transverse momentum dependent parton distribution functions (TMDs). The transverse single spin asymmetry (TSSA) of the 𝑍0 is sensitive to one of the polarized TMDs, the Sivers function, which is predicted to have the opposite sign in 𝑝 + 𝑝 → 𝑊 ∕𝑍 + 𝑋 from that which enters in semi-inclusive deep inelastic scattering. In this Letter, the STAR Collaboration reports the first measurement of the 𝑍0∕𝛾∗ differential cross section as a function of its 𝑝T in 𝑝+𝑝 collisions at a center-of-mass energy of 510 GeV, together with the 𝑍0∕𝛾∗ total cross section. We also report the measurement of 𝑍0∕𝛾∗ TSSA in transversely polarized 𝑝+𝑝 collisions at 510 GeV.