Refine
Year of publication
Document Type
- Preprint (788)
- Article (579)
- Conference Proceeding (7)
- Book (1)
Has Fulltext
- yes (1375)
Is part of the Bibliography
- no (1375)
Keywords
- Heavy Ion Experiments (21)
- Hadron-Hadron Scattering (14)
- Hadron-Hadron scattering (experiments) (11)
- LHC (10)
- Heavy-ion collision (6)
- Jets (6)
- ALICE experiment (4)
- Collective Flow (4)
- Heavy Ions (4)
- Heavy Quark Production (4)
- QCD (4)
- Quark-Gluon Plasma (4)
- ALICE (3)
- Branching fraction (3)
- COVID-19 (3)
- Jets and Jet Substructure (3)
- e +-e − Experiments (3)
- glioblastoma (3)
- pp collisions (3)
- Accelerators & Beams (2)
- Atomic, Molecular & Optical (2)
- Beauty production (2)
- Charm physics (2)
- Clinical decision support systems (2)
- Computer-assisted diagnosis (2)
- Depression (2)
- Epilepsy (2)
- Experimental nuclear physics (2)
- Experimental particle physics (2)
- Heavy-ion collisions (2)
- Lepton-Nucleon Scattering (experiments) (2)
- Liver transplantation (2)
- Monte Carlo (2)
- Particle Correlations and Fluctuations (2)
- Particle and Resonance Production (2)
- Particle and resonance production (2)
- Particle correlations and fluctuations (2)
- Pb–Pb collisions (2)
- Quality of life (2)
- Quark Gluon Plasma (2)
- Quarkonium (2)
- Rare diseases (2)
- Relativistic heavy-ion collisions (2)
- SARS-CoV-2 (2)
- Seizure (2)
- Single electrons (2)
- Systematic Uncertainty (2)
- Time Projection Chamber (2)
- acute myeloid leukemia (2)
- artificial intelligence (2)
- drug discovery (2)
- glioma (2)
- 2-deoxy-d-glucose (1)
- 2019-nCoV (1)
- 900 GeV (1)
- ACLF (1)
- AKI (1)
- ALICE LHC (1)
- ALICE detector (1)
- ATP (1)
- Accelerators & storage rings (1)
- Agoraphobia (1)
- Analysis and statistical methods (1)
- Anti-nuclei (1)
- Anti-seizure medication (1)
- Antiretroviral therapy (1)
- Antiretrovirals (1)
- Atomic & molecular beams (1)
- BCOR (1)
- BCORL1 (1)
- BESIII (1)
- BRAF (1)
- BRAF V600E (1)
- Balance function (1)
- Beam loss (1)
- Behavior (1)
- Biomarkers (1)
- Boosted Jets (1)
- Branching fractions (1)
- CAKUT (1)
- CLIF-C ACLF score (1)
- CLIF-C ACLF-R score (1)
- COMT (1)
- CTLA-4 (1)
- Calorimeters (1)
- Cardiac surgery (1)
- Centrality Class (1)
- Centrality Selection (1)
- Charge correlations (1)
- Charge-transfer collisions (1)
- Charged-particle density (1)
- Chemotherapy (1)
- Child abuse (1)
- Chronic depression (1)
- Circular accelerators (1)
- Cirrhosis (1)
- Clinical Trials and Observations (1)
- Clinical genetics (1)
- Cognitive behavioral therapy (1)
- Collective Flow, (1)
- Comorbidity (1)
- Comparison with QCD (1)
- Costs (1)
- Data processing methods (1)
- Decision making (1)
- Devic disease (1)
- Devic syndrome (1)
- EGFR (1)
- EP300 (1)
- EWSR1 (1)
- Electron-pion identification (1)
- Electronic transitions (1)
- Electroweak Interaction (1)
- Electroweak interaction (1)
- Elliptic flow (1)
- Everolimus (1)
- Evidence-based guidelines (1)
- Extended donor criteria (1)
- FOXO1 (1)
- Femtoscopy (1)
- Fibre/foam sandwich radiator (1)
- Gene fusion (1)
- General practice (1)
- Germany (1)
- Global positioning system (1)
- Goal-oriented care (1)
- Graft function (1)
- Graft survival (1)
- HBT (1)
- HIV (1)
- HIV-1 (1)
- HL7 FHIR (1)
- Hadron production (1)
- Hadron-Hadron Scattering Heavy (1)
- Hadron-hadron interactions (1)
- Hard Scattering (1)
- Heavy Ion Experiment (1)
- Heavy flavor production (1)
- Heavy flavour production (1)
- Heavy ions (1)
- Heavy-Ion Collision (1)
- Heavy-flavour decay muons (1)
- Heavy-flavour production (1)
- Heavy-ion detectors (1)
- Hepatitis C virus (1)
- Imaging genetics (1)
- Inclusive spectra (1)
- Intensity interferometry (1)
- Interview (1)
- Invariant Mass Distribution (1)
- Ionisation energy loss (1)
- Jet Physics (1)
- Jet Substructure (1)
- KCGS (1)
- KDIGO (1)
- Large Hadron Collider (1)
- Large detector systems for particle and astroparticle physics (1)
- Lemperle (1)
- Liver diseases (1)
- Low & intermediate-energy accelerators (1)
- Lung Cancer (1)
- MR-proADM (1)
- MR-spectroscopy (1)
- Marginal grafts (1)
- Material budget (1)
- Mental health and psychiatry (1)
- Mid-rapidity (1)
- Minimum Bias (1)
- Molecular medicine (1)
- Mortality (1)
- Multi-Parton Interactions (1)
- Multi-strange baryons (1)
- Multi-wire proportional drift chamber (1)
- Multimorbidity (1)
- Myeloid Neoplasia (1)
- NMO-IgG (1)
- NPSR1 (1)
- Neural network (1)
- Neuroepithelial tumor (1)
- Neuromyelitis optica (1)
- Non-small cell lung cancer (1)
- Nuclear Physics (1)
- Nuclear modification factor (1)
- Organ rinse (1)
- Organ shortage (1)
- PD-1 (1)
- PLAGL1 (1)
- PXA (1)
- PYTHIA (1)
- Panic disorder (1)
- Patient care planning (1)
- Patient preference (1)
- Patient-centered care (1)
- Pb–Pb (1)
- Performance of High Energy Physics Detectors (1)
- Photon counting (1)
- Polarization (1)
- Post-traumatic stress disorder (1)
- Primary care (1)
- Production Cross Section (1)
- Prognosis (1)
- Properties of Hadrons (1)
- Proteins (1)
- Proton–proton (1)
- Psoriasis vulgaris (1)
- Psychiatric disorders (1)
- Psychodynamic psychotherapy (1)
- Psychological and psychosocial issues (1)
- Qualitative research (1)
- Quark Deconfinement (1)
- Quark Production (1)
- Quark gluon plasma (1)
- ROS1 (1)
- Radiation detectors (1)
- Rapidity Range (1)
- Relativistic heavy ion physics (1)
- Resolution Parameter (1)
- Rhabdomyoma (1)
- SLC20A1 (1)
- SOFA (1)
- Semi-leptonic decays (1)
- Sepsis (1)
- Septic shock (1)
- Single muons (1)
- Supratentorial (1)
- TR (1)
- Tacrolimus (1)
- Tracking (1)
- Transition radiation detector (1)
- Transverse Momentum (1)
- Transverse momentum (1)
- Treatment (1)
- Trigger (1)
- Usability (1)
- Vector Boson Production (1)
- Westphal-Paradigm (1)
- Wide rapidity coverage (1)
- Xenon-based gas mixture (1)
- acute-on-chronic liver failure (1)
- advanced melanoma (1)
- age (1)
- amino acid PET (1)
- anti-angiogenic therapy (1)
- antibiotic therapy (1)
- antihelix shaping (1)
- antisynthetase antibodies (1)
- antisynthetase syndrome (1)
- antiviral (1)
- antiviral therapy (1)
- aprotinin (1)
- aquaporin-4 (AQP4) antibody (1)
- arthritis (1)
- atypical EGFR mutations (1)
- benfooxythiamine (1)
- bile acids (1)
- bladder exstrophy-epispadias complex (1)
- cardiac arrest (1)
- case study (1)
- cerebrospinal fluid (1)
- chemogenomic set (1)
- children and adolescents (1)
- chronic kidney disease (1)
- cirrhosis (1)
- clinical features (1)
- clinical trials (1)
- cloacal malformation (1)
- community-acquired pneumonia (1)
- complete response (1)
- cytarabine dose (1)
- dE/dx (1)
- dabrafenib (1)
- data sharing (1)
- detector (1)
- diet (1)
- discontinuation (1)
- disease progression (1)
- druggable genome (1)
- elderly (1)
- epidemiology (1)
- ethical trade-off (1)
- experimental results (1)
- explainable AI (1)
- fMRI (1)
- fasting (1)
- functional genetics (1)
- germ cell tumors (1)
- health information interoperability (1)
- healthcare (1)
- healthcare systems (1)
- heavy ion experiments (1)
- histology (1)
- hospital admission (1)
- imaging (1)
- immune checkpoint blockade (1)
- infections: pneumonia, TB, viral (1)
- inpatient hospital admissions (1)
- interstitial lung disease (1)
- ketogenic (1)
- ketone body (1)
- kidney formation (1)
- kinase inhibitor (1)
- leptomeningeal disease (1)
- liver cirrhosis (1)
- liver metastasis (1)
- lockdown (1)
- longitudinally extensive transverse myelitis (1)
- loss-of-function (1)
- mTOR inhibitor (1)
- macrophage polarization (1)
- magnetic resonance imaging (1)
- male (1)
- mechanical ventilation (1)
- medical informatics initiative (1)
- microbiome (1)
- molecular methods (1)
- mortality (1)
- myositis (1)
- nocardia (1)
- nocardiosis (1)
- non-small-cell lung cancer (1)
- observational cohort study (1)
- otoplasty (1)
- ovary (1)
- oxythiamine (1)
- pandemic (1)
- pentose phosphate pathway (1)
- periodontitis (1)
- phenotypic screening (1)
- pleomorphic xanthoastrocytoma (1)
- portal hypertension (1)
- prospective study (1)
- protein kinase (1)
- protruding ear (1)
- pulmonary failure (1)
- pulmonary nocardiosis (1)
- quark gluon plasma (1)
- recurrent optic neuritis (1)
- respiratory failure (1)
- risk factors (1)
- risk stratification (1)
- second-line immunotherapy (1)
- severe acute respiratory syndrome coronavirus (1)
- severe acute respiratory syndrome coronavirus 2 (1)
- sex (1)
- small molecules (1)
- spectra (1)
- survival (1)
- targeted therapy (1)
- testis (1)
- therapy resistance (1)
- treatment resistance (1)
- treatment-related changes (1)
- trials registry (1)
- trust (1)
- trustworthy AI (1)
- tumor angiogenesis (1)
- tumor progression (1)
- understudied kinase (1)
- university hospitals (1)
- urinary tract development (1)
- uveal melanoma (1)
- vasodilation (1)
- ventral otoplasty (1)
- viral pathogens (1)
- x-ray techniques (1)
- zebrafish development (1)
- Λ+c baryon (1)
- √sN N = 2.76 TeV (1)
Institute
- Physik (1294)
- Frankfurt Institute for Advanced Studies (FIAS) (1058)
- Informatik (1023)
- Medizin (64)
- Geowissenschaften (10)
- Informatik und Mathematik (3)
- Biodiversität und Klima Forschungszentrum (BiK-F) (2)
- ELEMENTS (2)
- Geographie (2)
- Hochschulrechenzentrum (2)
The production cross section of prompt Λ+c charmed baryons was measured with the ALICE detector at the LHC at midrapidity in proton-proton (pp) and proton-lead (p-Pb) collisions at a centre-of-mass energy per nucleon pair of sNN−−−√=5.02 TeV. The Λ+c and Λ¯¯¯¯−c baryons were reconstructed in the hadronic decay channels Λ+c→pK−π+ and Λ+c→pK0S and respective charge conjugates. The measured differential cross sections as a function of transverse momentum (pT) and the pT-integrated Λ+c production cross section in pp and in p-Pb collisions are presented. The Λ+c nuclear modification factor (RpPb), calculated from the cross sections in pp and in p-Pb collisions, is presented and compared with the RpPb of D mesons. The Λ+c/D0 ratio is also presented and compared with the light-flavour baryon-to-meson ratios p/π and Λ/K0S, and measurements from other LHC experiments. The results are compared to predictions from model calculations and Monte Carlo event generators.
The production cross section of prompt Λ+c charm baryons was measured with the ALICE detector at the LHC at midrapidity in proton-proton (pp) and proton-lead (p-Pb) collisions at a centre-of-mass energy per nucleon pair of sNN−−−√=5.02 TeV. The Λ+c and Λ¯¯¯¯−c baryons were reconstructed in the hadronic decay channels Λ+c→pK−π+ and Λ+c→pK0S and respective charge conjugates. The measured differential cross sections as a function of transverse momentum (pT) and the pT-integrated Λ+c production cross section in pp and in p-Pb collisions are presented. The Λ+c nuclear modification factor (RpPb), calculated from the cross sections in pp and in p-Pb collisions, is presented and compared with the RpPb of D mesons. The Λ+c/D0 ratio is also presented and compared with the light-flavour baryon-to-meson ratios p/π and Λ/K0S, and measurements from other LHC experiments. The results are compared to predictions from model calculations and Monte Carlo event generators.
Jet fragmentation transverse momentum distributions in pp and p–Pb collisions at √s, √sNN = 5.02 TeV
(2021)
Jet fragmentation transverse momentum (jT) distributions are measured in proton-proton (pp) and proton-lead (p-Pb) collisions at sNN−−−√ = 5.02 TeV with the ALICE experiment at the LHC. Jets are reconstructed with the ALICE tracking detectors and electromagnetic calorimeter using the anti-kT algorithm with resolution parameter R=0.4 in the pseudorapidity range |η|<0.25. The jT values are calculated for charged particles inside a fixed cone with a radius R=0.4 around the reconstructed jet axis. The measured jT distributions are compared with a variety of parton-shower models. Herwig and PYTHIA 8 based models describe the data well for the higher jT region, while they underestimate the lower jT region. The jT distributions are further characterised by fitting them with a function composed of an inverse gamma function for higher jT values (called the "wide component"), related to the perturbative component of the fragmentation process, and with a Gaussian for lower jT values (called the "narrow component"), predominantly connected to the hadronisation process. The width of the Gaussian has only a weak dependence on jet transverse momentum, while that of the inverse gamma function increases with increasing jet transverse momentum. For the narrow component, the measured trends are successfully described by all models except for Herwig. For the wide component, Herwig and PYTHIA 8 based models slightly underestimate the data for the higher jet transverse momentum region. These measurements set constraints on models of jet fragmentation and hadronisation.
The cross section for coherent photonuclear production of J/ψ is presented as a function of the electromagnetic dissociation (EMD) of Pb. The measurement is performed with the ALICE detector in ultra-peripheral Pb-Pb collisions at a centre-of-mass energy per nucleon pair of sNN−−−√=5.02 TeV. Cross sections are presented in five different J/ψ rapidity ranges within |y|<4, with the J/ψ reconstructed via its dilepton decay channels. In some events the J/ψ is not accompanied by EMD, while other events do produce neutrons from EMD at beam rapidities either in one or the other beam direction, or in both. The cross sections in a given rapidity range and for different configurations of neutrons from EMD allow for the extraction of the energy dependence of this process in the range 17<WγPb,n<920 GeV, where WγPb,n is the centre-of-mass energy per nucleon of the γPb system. This range corresponds to a Bjorken-x interval spanning about three orders of magnitude: 1.1×10−5<x<3.3×10−2. In addition to the ultra-peripheral and photonuclear cross sections, the nuclear suppression factor is obtained. These measurements point to a strong depletion of the gluon distribution in Pb nuclei over a broad, previously unexplored, energy range. These results, together with previous ALICE measurements, provide unprecedented information to probe quantum chromodynamics at high energies.
The first measurements of the production of muons and electrons from heavy-flavour hadron decays in Xe-Xe collisions at sNN−−−√ = 5.44 TeV, using the ALICE detector at the LHC, are reported. The measurement of the nuclear modification factor RAA is performed as a function of transverse momentum pT in several centrality classes at forward rapidity (2.5<y<4) and midrapidity (|y|<0.8) for muons and electrons from heavy-flavour hadron decays, respectively. A suppression by a factor up to about 2.5 compared to the binary-scaled pp reference is observed in central collisions at both central and forward rapidities. The RAA of muons from heavy-flavour hadron decays is compared to previous measurements in Pb-Pb collisions at sNN−−−√ = 5.02 TeV. When the nuclear modification factors are compared in the centrality classes 0-10% for Xe-Xe collisions and 10-20% for Pb-Pb collisions, which have similar charged-particle multiplicity density, a similar suppression, with RAA∼0.4 in the pT interval 4<pT<8 GeV/c, is observed. The comparison of the measured RAA values in the two collision systems brings new insights on the properties of the quark-gluon plasma by investigating the system-size and path-length dependence of medium-induced parton energy loss. The results of muons and electrons from heavy-flavour hadron decays provide new constraints to model calculations.
ϒ production and nuclear modification at forward rapidity in Pb–Pb collisions at √sNN = 5.02 TeV
(2021)
The production of Υ mesons in Pb-Pb collisions at a centre-of-mass energy per nucleon pair sNN−−−√ = 5 TeV is measured with the muon spectrometer of the ALICE detector at the LHC. The yields as well as the nuclear modification factors are determined in the forward rapidity region 2.5<y<4.0, as a function of rapidity, transverse momentum and collision centrality. The results show that the production of the Υ(1S) meson is suppressed by a factor of about three with respect to the production in proton-proton collisions. For the first time, a significant signal for the Υ(2S) meson is observed at forward rapidity, indicating a suppression stronger by about a factor 2-3 with respect to the ground state. The measurements are compared with transport, hydrodynamic, comover and statistical hadronisation model calculations.
In ultraperipheral collisions (UPCs) of relativistic nuclei without overlap of nuclear densities, the two nuclei are excited by the Lorentz-contracted Coulomb fields of their collision partners. In these UPCs, the typical nuclear excitation energy is below a few tens of MeV, and a small number of nucleons are emitted in electromagnetic dissociation (EMD) of primary nuclei, in contrast to complete nuclear fragmentation in hadronic interactions. The cross sections of emission of given numbers of neutrons in UPCs of 208Pb nuclei at sNN−−−√=5.02 TeV were measured with the neutron zero degree calorimeters (ZDCs) of the ALICE detector at the LHC, exploiting a similar technique to that used in previous studies performed at sNN−−−√=2.76 TeV. In addition, the cross sections for the exclusive emission of one, two, three, four, and five forward neutrons in the EMD, not accompanied by the emission of forward protons, and thus mostly corresponding to the production of 207,206,205,204,203Pb, respectively, were measured for the first time. The predictions from the available models describe the measured cross sections well. These cross sections can be used for evaluating the impact of secondary nuclei on the LHC components, in particular, on superconducting magnets, and also provide useful input for the design of the Future Circular Collider (FCC-hh).
Deuteron production in high-energy collisions is sensitive to the space-time evolution of the collision system, and is typically described by a coalescence mechanism. For the first time, we present results on jet-associated deuteron production in \pp\ collisions at s√=13 TeV, providing an opportunity to test the established picture for deuteron production in events with a hard scattering. Using a trigger particle with high transverse-momentum (pT>5 GeV/c) as a proxy for the presence of a jet at midrapidity, we observe a measurable population of deuterons being produced around the jet proxy. The associated deuteron yield measured in a narrow angular range around the trigger particle differs by 2.4-4.8 standard deviations from the uncorrelated background. The data are described by PYTHIA model calculations featuring baryon coalescence.
The production cross section of prompt Λ+c charmed baryons was measured with the ALICE detector at the LHC at midrapidity in proton-proton (pp) and proton-lead (p-Pb) collisions at a centre-of-mass energy per nucleon pair of sNN−−−√=5.02 TeV. The Λ+c and Λ¯¯¯¯−c baryons were reconstructed in the hadronic decay channels Λ+c→pK−π+ and Λ+c→pK0S and respective charge conjugates. The measured differential cross sections as a function of transverse momentum (pT) and the pT-integrated Λ+c production cross section in pp and in p-Pb collisions are presented. The Λ+c nuclear modification factor (RpPb), calculated from the cross sections in pp and in p-Pb collisions, is presented and compared with the RpPb of D mesons. The Λ+c/D0 ratio is also presented and compared with the light-flavour baryon-to-meson ratios p/π and Λ/K0S, and measurements from other LHC experiments. The results are compared to predictions from model calculations and Monte Carlo event generators.
The first measurement of the coherent photoproduction of ρ0 vector mesons in ultra-peripheral Xe-Xe collisions at sNN−−−√=5.44 TeV is presented. This result, together with previous HERA γp data and γ-Pb measurements from ALICE, describes the atomic number (A) dependence of this process, which is particularly sensitive to nuclear shadowing effects and to the approach to the black-disc limit of QCD at a semi-hard scale. The cross section of the Xe+Xe→ρ0+Xe+Xe process, measured at midrapidity through the decay channel ρ0→π+π−, is found to be dσ/dy=131.5±5.6(stat.)+17.5−16.9(syst.) mb. The ratio of the continuum to resonant contributions for the production of pion pairs is also measured. In addition, the fraction of events accompanied by electromagnetic dissociation of either one or both colliding nuclei is reported. The dependence on A of cross section for the coherent ρ0 photoproduction at a centre-of-mass energy per nucleon of the γA system of WγA,n=65 GeV is found to be consistent with a power-law behaviour σ(γA→ρ0A)∝Aα with a slope α=0.96±0.02(syst.). This slope signals important shadowing effects, but it is still far from the behaviour expected in the black-disc limit.
The first measurement of the coherent photoproduction of ρ0 vector mesons in ultra-peripheral Xe-Xe collisions at sNN−−−√=5.44 TeV is presented. This result, together with previous γp and γ-Pb measurements, describes the atomic number (A) dependence of this process, which is particularly sensitive to nuclear shadowing effects and to the approach to the black-disc limit of QCD at a semi-hard scale. The cross section of the Xe+Xe→ρ0+Xe+Xe process, measured at midrapidity through the decay channel ρ0→π+π−, is found to be dσ/dy=131.5±5.6(stat.)+17.5−16.9(syst.) mb. The ratio of the continuum to resonant contributions for the production of pion pairs is also measured. In addition, the fraction of events accompanied by electromagnetic dissociation of either one or both colliding nuclei is reported. The dependence on A of cross section for the coherent ρ0 photoproduction at a centre-of-mass energy per nucleon of the γA system of WγA,n=65 GeV is found to be consistent with a power-law behaviour σ(γA→ρ0A)∝Aα with a slope α=0.96±0.02(syst.). This slope signals important shadowing effects, but it is still far from the behaviour expected in the black-disc limit.
The production of K∗(892)0 and ϕ(1020) mesons in proton-proton (pp) and lead-lead (Pb-Pb) collisions at sNN−−−√=5.02 TeV has been measured using the ALICE detector at the Large Hadron Collider (LHC). The transverse momentum (pT) distributions of K∗(892)0 and ϕ(1020) mesons have been measured at midrapidity (|y|<0.5) up to pT=20 GeV/c in inelastic pp collisions and for several Pb-Pb collision centralities. The collision centrality and collision energy dependence of the average transverse momenta agree with the radial flow scenario observed with stable hadrons, showing that the effect is stronger for more central collisions and higher collision energies. The K∗0/K ratio is found to be suppressed in Pb-Pb collisions relative to pp collisions: this indicates a loss of the measured K∗(892)0 signal due to rescattering of its decay products in the hadronic phase. In contrast, for the longer-lived ϕ(1020) mesons, no such suppression is observed. The nuclear modification factors (RAA) of K∗(892)0 and ϕ(1020) mesons are calculated using pp reference spectra at the same collision energy. In central Pb-Pb collisions for pT>8 GeV/c, the RAA values of K∗(892)0 and ϕ(1020) are below unity and observed to be similar to those of pions, kaons, and (anti)protons. The RAA values at high pT (>~8 GeV/c) for K∗(892)0 and ϕ(1020) mesons are in agreement within uncertainties for sNN−−−√=5.02 and 2.76 TeV.
In quantum scattering processes between two particles, aspects characterizing the strong and Coulomb forces can be observed in kinematic distributions of the particle pairs. The sensitivity to the interaction potential reaches a maximum at low relative momentum and vanishing distance between the two particles. Ultrarelativistic heavy-ion collisions at the LHC provide an abundant source of many hadron species and can be employed as a measurement method of scattering parameters that is complementary to scattering experiments. This study confirms that momentum correlations of particles produced in Pb-Pb collisions at the LHC provide an accurate measurement of kaon-proton scattering parameters at low relative momentum, allowing precise access to the K−p→K−p process. This work also validates the femtoscopic measurement in ultrarelativistic heavy-ion collisions as an alternative to scattering experiments and a complementary tool to the study of exotic atoms with comparable precision. In this work, the first femtoscopic measurement of momentum correlations of K−p (K+p¯¯¯) and K+p(K−p¯¯¯) pairs in Pb-Pb collisions at centre-of-mass energy per nucleon pair of sNN−−−√=5.02 TeV registered by the ALICE experiment is reported. The components of the K−p complex scattering length are extracted and found to be Rf0=−0.91± 0.03(stat)+0.17−0.03(syst) and If0=0.92± 0.05(stat)+0.12−0.33(syst). The results are compared with chiral effective field theory predictions as well as with existing data from dedicated scattering and exotic kaonic atom experiments.
Production of pions, kaons, (anti-)protons and φ mesons in Xe–Xe collisions at √sNN = 5.44 TeV
(2021)
The first measurement of the production of pions, kaons, (anti-)protons and ϕ mesons at midrapidity in Xe-Xe collisions at sNN−−−√=5.44 TeV is presented. Transverse momentum (pT) spectra and pT-integrated yields are extracted in several centrality intervals bridging from p-Pb to mid-central Pb-Pb collisions in terms of final-state multiplicity. The study of Xe-Xe and Pb-Pb collisions allows systems at similar charged-particle multiplicities but with different initial geometrical eccentricities to be investigated. A detailed comparison of the spectral shapes in the two systems reveals an opposite behaviour for radial and elliptic flow. In particular, this study shows that the radial flow does not depend on the colliding system when compared at similar charged-particle multiplicity. In terms of hadron chemistry, the previously observed smooth evolution of particle ratios with multiplicity from small to large collision systems is also found to hold in Xe-Xe. In addition, our results confirm that two remarkable features of particle production at LHC energies are also valid in the collision of medium-sized nuclei: the lower proton-to-pion ratio with respect to the thermal model expectations and the increase of the ϕ-to-pion ratio with increasing final-state multiplicity.
Production of pions, kaons, (anti-)protons and φ mesons in Xe–Xe collisions at √sNN = 5.44 TeV
(2021)
The first measurement of the production of pions, kaons, (anti-)protons and ϕ mesons at midrapidity in Xe-Xe collisions at sNN−−−√=5.44 TeV is presented. Transverse momentum (pT) spectra and pT-integrated yields are extracted in several centrality intervals bridging from p-Pb to mid-central Pb-Pb collisions in terms of final-state multiplicity. The study of Xe-Xe and Pb-Pb collisions allows systems at similar charged-particle multiplicities but with different initial geometrical eccentricities to be investigated. A detailed comparison of the spectral shapes in the two systems reveals an opposite behaviour for radial and elliptic flow. In particular, this study shows that the radial flow does not depend on the colliding system when compared at similar charged-particle multiplicity. In terms of hadron chemistry, the previously observed smooth evolution of particle ratios with multiplicity from small to large collision systems is also found to hold in Xe-Xe. In addition, our results confirm that two remarkable features of particle production at LHC energies are also valid in the collision of medium-sized nuclei: the lower proton-to-pion ratio with respect to the thermal model expectations and the increase of the ϕ-to-pion ratio with increasing final-state multiplicity.
The first measurements of the production of muons and electrons from heavy-flavour hadron decays in Xe-Xe collisions at sNN−−−√ = 5.44 TeV, using the ALICE detector at the LHC, are reported. The measurement of the nuclear modification factor RAA is performed as a function of transverse momentum pT in several centrality classes at forward rapidity (2.5<y<4) and midrapidity (|y|<0.8) for muons and electrons from heavy-flavour hadron decays, respectively. A suppression by a factor up to about 2.5 compared to the binary-scaled pp reference is observed in central collisions at both central and forward rapidities. The RAA of muons from heavy-flavour hadron decays is compared to previous measurements in Pb-Pb collisions at sNN−−−√ = 5.02 TeV. A similar suppression, with RAA∼0.4 in the pT interval 4<pT<8 GeV/c, is observed in Pb-Pb and Xe-Xe collisions when the nuclear modification factors are compared in event classes with similar charged-particle multiplicity density. The comparison of the measured RAA values in the two collision systems brings new insights on the properties of the quark-gluon plasma by investigating the system-size and path-length dependence of medium-induced parton energy loss. The results of muons and electrons from heavy-flavour hadron decays provide new constraints to model calculations.
Measurements of the production of muons from heavy-flavour hadron decays in Pb−Pb collisions at sNN−−−√ = 5.02 and 2.76 TeV using the ALICE detector at the LHC are reported. The nuclear modification factor RAA at sNN−−−√ = 5.02 TeV is measured at forward rapidity (2.5<y<4) as a function of transverse momentum pT in central, semi-central, and peripheral collisions over a wide pT interval, 3<pT<20 GeV/c, in which a significant contribution of muons from beauty-hadron decays is expected at high pT. With a significantly improved precision compared to the measurements at lower collision energy, the RAA shows an increase of the suppression of the yields of muons from heavy-flavour hadron decays with increasing centrality. A suppression by a factor of about three is observed in the 10% most central collisions. The RAA at sNN−−−√ = 5.02 is similar to that reported at 2.76 TeV in a broader pT interval and with an improved accuracy with respect to previously published measurements. The precise RAA results have the potential to distinguish between model predictions implementing different mechanisms of parton energy loss in the high-density medium formed in heavy-ion collisions. The results place stringent constraints on the relative energy loss between charm and beauty quarks.
Λ+c production and baryon-to-meson ratios in pp and p–Pb collisions at √sNN = 5.02 TeV at the LHC
(2021)
The prompt production of the charm baryon Λ+c and the Λ+c/D0 production ratios were measured at midrapidity with the ALICE detector in pp and p-Pb collisions at sNN−−−√=5.02TeV. These new measurements show a clear decrease of the Λ+c/D0 ratio with increasing transverse momentum (pT) in both collision systems in the range 2<pT<12 GeV/c, exhibiting similarities with the light-flavour baryon-to-meson ratios p/π and Λ/K0S. At low pT, predictions that include additional colour-reconnection mechanisms beyond the leading-colour approximation; assume the existence of additional higher-mass charm-baryon states; or include hadronisation via coalescence can describe the data, while predictions driven by charm-quark fragmentation processes measured in e+e− and e−p collisions significantly underestimate the data. The results presented in this letter provide significant evidence that the established assumption of universality (colliding-system independence) of parton-to-hadron fragmentation is not sufficient to describe charm-baryon production in hadronic collisions at LHC energies.
Λ+c production and baryon-to-meson ratios in pp and p–Pb collisions at √sNN = 5.02 TeV at the LHC
(2021)
The prompt production of the charm baryon Λ+c and the Λ+c/D0 production ratios were measured at midrapidity with the ALICE detector in pp and p-Pb collisions at sNN−−−√=5.02TeV. These new measurements show a clear decrease of the Λ+c/D0 ratio with increasing transverse momentum (pT) in both collision systems in the range 2<pT<12 GeV/c, exhibiting similarities with the light-flavour baryon-to-meson ratios p/π and Λ/K0S. At low pT, predictions that include additional colour-reconnection mechanisms beyond the leading-colour approximation; assume the existence of additional higher-mass charm-baryon states; or include hadronisation via coalescence can describe the data, while predictions driven by charm-quark fragmentation processes measured in e+e− and e−p collisions significantly underestimate the data. The results presented in this letter provide significant evidence that the established assumption of universality (colliding-system independence) of parton-to-hadron fragmentation is not sufficient to describe charm-baryon production in hadronic collisions at LHC energies.
ϒ production and nuclear modification at forward rapidity in Pb–Pb collisions at √sNN = 5.02 TeV
(2020)
The production of Υ mesons in Pb-Pb collisions at a centre-of-mass energy per nucleon pair sNN−−−√ = 5 TeV is measured with the muon spectrometer of ALICE at the LHC. The yields as well as the nuclear modification factors are determined in the forward rapidity region 2.5<y<4.0, as a function of rapidity, transverse momentum and collision centrality. The results show that the production of Υ(1S) is suppressed by a factor of about three with respect to the production in proton-proton collisions. For the first time, a significant Υ(2S) signal is observed at forward rapidity, indicating a suppression stronger by about a factor 2-3 with respect to the ground state. The measurements are compared with transport, hydrodynamic, comover and statistical hadronisation model calculations.