Refine
Year of publication
Document Type
- Article (15913)
- Part of Periodical (2728)
- Working Paper (2352)
- Preprint (2121)
- Doctoral Thesis (2066)
- Book (1736)
- Part of a Book (1071)
- Conference Proceeding (752)
- Report (471)
- Review (165)
Language
- English (29540) (remove)
Has Fulltext
- yes (29540) (remove)
Keywords
- taxonomy (744)
- new species (445)
- morphology (174)
- Deutschland (142)
- Syntax (125)
- Englisch (120)
- distribution (117)
- biodiversity (101)
- inflammation (100)
- Deutsch (98)
Institute
- Medizin (5383)
- Physik (3877)
- Wirtschaftswissenschaften (1915)
- Frankfurt Institute for Advanced Studies (FIAS) (1764)
- Biowissenschaften (1558)
- Center for Financial Studies (CFS) (1492)
- Informatik (1403)
- Biochemie und Chemie (1090)
- Sustainable Architecture for Finance in Europe (SAFE) (1069)
- House of Finance (HoF) (707)
Atomic nuclei are self-organized, many-body quantum systems bound by strong nuclear forces within femtometer-scale space. These complex systems manifest a diverse set of shapes~, traditionally explored via non-invasive spectroscopic techniques at low energies. Their instantaneous shapes, obscured by long-timescale quantum fluctuations, are considered not directly observable at low energy. We introduce a complementary method, collective flow assisted nuclear shape imaging, to image the nuclear global shape by colliding them at ultrarelativistic speeds and analyzing the collective response of outgoing debris. This technique captures a collision-specific snapshot of the spatial matter distribution in the nuclei, which, through the hydrodynamic expansion, leaves imprints on the particle momentum distribution patterns observed in detectors. We benchmark this method in collisions of ground state Uranium-238 nuclei, known for its elongated, axial-symmetric shape. Our findings, while confirming an overall deformation broadly consistent with prior low-energy experiments, also indicate a small deviation from axial symmetry in the nuclear ground state. This approach marks a new way of imaging nuclei, especially those with uncertain shape characteristics, and refines initial conditions in high-energy nuclear collisions. It tackles the important issue of nuclear structure evolution across various energy scales.
Flow coefficients (v2 and v3) are measured in high-multiplicity p+Au, d+Au, and 3He+Au collisions at a center-of-mass energy of √sNN = 200 GeV using the STAR detector. The measurements are conducted using two-particle correlations with a pseudorapidity requirement of |η|< 0.9 and a pair gap of |Δη|>1.0. The primary focus of this paper is on the analysis procedures and methods employed, especially the subtraction of non-flow contributions. Four well-established non-flow subtraction methods are applied to determine vn, and their validity is verified using the HIJING event generator. The vn values are compared across the three collision systems at similar multiplicities, which allows for cancellation of final state effects and isolation of the impact of the initial geometry. While the v2 values display differences among these collision systems, the v3 values are largely similar, consistent with the expectations of subnucleon fluctuations in the initial geometry. The ordering of vn differs quantitatively from previous measurements obtained using two-particle correlations with a larger rapidity gap; this difference could be partially attributed to the effects of flow decorrelations in the rapidity direction.
We report a measurement of exclusive J/ψ photoproduction in Au+Au ultra-peripheral collisions at sNN−−−√=200 GeV using the STAR detector. For the first time, i) the rapidity correlation between J/ψ photoproduction and neutron emission from nuclear breakups has been experimentally measured; ii) nuclear suppression factors are measured for both the coherent and incoherent J/ψ production. At photon-nucleon center-of-mass energy of 25.0 GeV, the coherent and incoherent J/ψ cross sections of Au nuclei are found to be 71±10% and 36±7%, respectively, of that of free protons. The stronger suppression observed in the incoherent production provides a new experimental handle to study the initial-state parton density in heavy nuclei. Data are compared with theoretical models quantitatively.
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 measurement of exclusive J/ψ photoproduction in Au+Au ultra-peripheral collisions at sNN−−−√=200 GeV using the STAR detector. For the first time, i) the rapidity correlation between J/ψ photoproduction and neutron emission from nuclear breakups has been experimentally measured; ii) nuclear suppression factors are measured for both the coherent and incoherent J/ψ production. At photon-nucleon center-of-mass energy of 25.0 GeV, the coherent and incoherent J/ψ cross sections of Au nuclei are found to be 71±10% and 36±7%, respectively, of that of free protons. The stronger suppression observed in the incoherent production provides a new experimental handle to study the initial-state parton density in heavy nuclei. Data are compared with theoretical models quantitatively.
Measurements of exclusive J/ψ, ψ(2s), and electron-positron (e+e−) pair photoproduction in Au+Au ultra-peripheral collisions are reported by the STAR experiment at √sNN=200 GeV. We report several first measurements at the Relativistic Heavy-Ion Collider, which are i) J/ψ photoproduction with large momentum transfer up to 2.2 (GeV/c)2, ii) coherent J/ψ photoproduction associated with neutron emissions from nuclear breakup, iii) the rapidity dependence of incoherent J/ψ photoproduction, iv) the ψ(2s) photoproduction cross section at mid-rapidity, and v) e+e− pair photoproduction up to high invariant mass of 6 GeV/c2. For measurement ii), the coherent J/ψ total cross section of γ∗+Au→J/ψ+Au as a function of the center-of-mass energy Wγ∗N has been obtained without photon energy ambiguities. The data are quantitatively compared with the Monte Carlo models STARlight, Sartre, BeAGLE, and theoretical calculations of gluon saturation with color glass condensate, nuclear shadowing with leading twist approximation, Quantum Electrodynamics, and the Next-to-Leading Order perturbative QCD. At the photon-nucleon center-of-mass energy of 25.0 GeV, the coherent and incoherent J/ψ cross sections of Au nuclei are found to be 71±10% and 36±7%, respectively, of that of free protons. These data provide an important experimental constraint for nuclear parton distribution functions and a unique opportunity to advance the understanding of the nuclear modification effect at the top RHIC energy.
Production of protons and light nuclei in Au+Au collisions at √sNN = 3 GeV with the STAR detector
(2023)
We report the systematic measurement of protons and light nuclei production in Au+Au collisions at √sNN = 3 GeV by the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The transverse momentum (pT) spectra of protons (p), deuterons (d), tritons (t), 3He, and 4He are measured from mid-rapidity to target rapidity for different collision centralities. We present the rapidity and centrality dependence of particle yields (dN/dy), average transverse momentum (⟨pT⟩), yield ratios (d/p, t/p,3He/p, 4He/p), as well as the coalescence parameters (B2, B3). The 4π yields for various particles are determined by utilizing the measured rapidity distributions, dN/dy. Furthermore, we present the energy, centrality, and rapidity dependence of the compound yield ratios (Np×Nt/N2d) and compare them with various model calculations. The physics implications of those results on the production mechanism of light nuclei and on QCD phase structure are discussed.
We report on the charged-particle multiplicity dependence of net-proton cumulant ratios up to sixth order from √s = 200 GeV p+p collisions at the Relativistic Heavy Ion Collider (RHIC). The measured ratios C4/C2, C5/C1, and C6/C2 decrease with increased charged-particle multiplicity and rapidity acceptance. Neither the Skellam baselines nor PYTHIA8 calculations account for the observed multiplicity dependence. In addition, the ratios C5/C1 and C6/C2 approach negative values in the highest-multiplicity events. The negative ratios in the most central p+p collisions at 200 GeV, similar to those observed in central Au+Au 200 GeV collisions, imply the formation of thermalized QCD matter.
Jet-hadron correlations with respect to the event plane in √sNN = 200 GeV Au+Au collisions in STAR
(2023)
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.
We report the first measurements of cumulants, up to 4th order, of deuteron number distributions and proton-deuteron correlations in Au+Au collisions recorded by the STAR experiment in phase-I of Beam Energy Scan (BES-I) program at the Relativistic Heavy Ion Collider (RHIC). Deuteron cumulants, their ratios, and proton-deuteron mixed cumulants are presented for different collision centralities covering a range of center of mass energy per nucleon pair sNN−−−√ = 7.7 to 200 GeV. It is found that the cumulant ratios at lower collision energies favor a canonical ensemble over a grand canonical ensemble in thermal models. An anti-correlation between proton and deuteron multiplicity is observed across all collision energies and centralities, consistent with the expectation from global baryon number conservation. The UrQMD model coupled with a phase-space coalescence mechanism qualitatively reproduces the collision-energy dependence of cumulant ratios and proton-deuteron correlations.