Azimuthal anisotropy of direct photons in Au+Au collisions at βsNN=200GeV
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73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Engineering topics
Fan, W.
Publications and source records attributed to Fan, W..
Hard jet substructure in a multistage approach
We present predictions and postdictions for a wide variety of hard jet-substructure observables using a multistage model within the framework. The details of the multistage model and the various parameter choices are described in []. A novel feature of this model is the presence of two stages of jet modification: a high-virtuality phase [modeled using the modular all twist transverse-scattering elastic-drag and radiation model ()], where modified coherence effects diminish medium-induced radiation, and a lower virtuality phase [modeled using the linear Boltzmann transport model ()], where parton splits are fully resolved by the medium as they endure multiple scattering induced energy loss. Energy-loss calculations are carried out on event-by-event viscous fluid dynamic backgrounds constrained by experimental data. The uniform and consistent descriptions of multiple experimental observables demonstrate the essential role of modified coherence effects and the multistage modeling of jet evolution. Using the best choice of parameters from [], and with no further tuning, we present calculations for the medium modified jet fragmentation function, the groomed jet momentum fraction z g and angular separation r g distributions, as well as the nuclear modification factor of groomed jets. These calculations provide accurate descriptions of published data from experiments at the Large Hadron Collider. Furthermore, we provide predictions from the multistage model for future measurements at the BNL Relativistic Heavy Ion Collider. Published by the American Physical Society 2024
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
New metric improving Bayesian calibration of a multistage approach studying hadron and inclusive jet suppression
We study parton energy-momentum exchange with the quark gluon plasma (QGP) within a multistage approach composed of in-medium Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution at high virtuality, and (linearized) Boltzmann transport formalism at lower virtuality. This multistage simulation is then calibrated in comparison with high- p T charged hadrons, D mesons, and the inclusive jet nuclear modification factors, using Bayesian model-to-data comparison, to extract the virtuality-dependent transverse momentum broadening transport coefficient q Μ . To facilitate this undertaking, we develop a quantitative metric for validating the Bayesian workflow, which is used to analyze the sensitivity of various model parameters to individual observables. The usefulness of this new metric in improving Bayesian model emulation is shown to be highly beneficial for future such analyses. Published by the American Physical Society 2024
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Identified charged-hadron production in π+Al, 3 He + Au, and Cu + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and in U + U collisions at $\sqrt{s_{NN}}$ = 193 GeV
The PHENIX experiment has performed a systematic study of identified charged-hadron (π Β± , πΎ Β± , π, $\bar{π}$) production at midrapidity in π + Al, 3 He + Au, and Cu + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and U + U collisions at $\sqrt{s_{NN}}$ = 193 GeV. Identified charged-hadron invariant transverse-momentum (π π ) and transverse-mass (π π ) spectra are presented and interpreted in terms of radially expanding thermalized systems. The particle ratios of πΎ/π and π/π have been measured in different centrality ranges of large (Cu + Au and U + U) and small (π + Al and 3 He + Au) collision systems. The values of πΎ/π ratios measured in all considered collision systems were found to be consistent with those measured in π+π collisions. However, the values of π/π ratios measured in large collision systems reach the values of β0.6, which is a factor of β2 larger than in π + π collisions. These results can be qualitatively understood in terms of the baryon enhancement expected from hadronization by recombination. Identified charged-hadron nuclear-modification factors (π π΄β’π΅ ) are also presented. Enhancement of proton π π΄β’π΅ values over meson π π΄β’π΅ values was observed in central 3 He + Au, Cu + Au, and U + U collisions. Finally, the proton π π΄β’π΅ values measured in the π + Al collision system were found to be consistent with π π΄β’π΅ values of π, π Β± , πΎ Β± , and π 0 mesons, which may indicate that the size of the system produced in π + Al collisions is too small for recombination to cause a noticeable increase in proton production.
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Nonprompt direct-photon production in Au + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV
The measurement of the direct-photon spectrum from Au + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV is presented by the PHENIX Collaboration using the external-photon-conversion technique for 0%β93% central collisions in a transverse-momentum (π π ) range of 0.8β10 GeV/π. An excess of direct photons, above prompt-photon production from hard-scattering processes, is observed for π π < 6 GeV/π. Nonprompt direct photons are measured by subtracting the prompt component, which is estimated as π coll -scaled direct photons from π + π collisions at 200 GeV, from the direct-photon spectrum. Results are obtained for 0.8 < π π < 6.0 GeV/π and suggest that the spectrum has an increasing inverse slope from β0.2 to 0.4 GeV/π with increasing π π , which indicates a possible sensitivity of the measurement to photons from earlier stages of the evolution of the collision. In addition, like the direct-photon production, the π π -integrated nonprompt direct-photon yields also follow a power-law scaling behavior as a function of collision-system size. Finally, the exponent, πΌ, for the nonprompt component is found to be consistent with 1.1 with no apparent π π dependence.
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Charm- and bottom-quark production in Au+Au collisions at $$ \sqrt{{\textrm{s}}_{\textrm{NN}}} $$=200 GeV
Here, the invariant yield of electrons from open-heavy-flavor decays for 1 < p T < 8 GeV/c at midrapidity |y| < 0.35 in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV has been measured by the PHENIX experiment at the Relativistic Heavy Ion Collider. A displaced-vertex analysis with the PHENIX silicon-vertex detector enables extraction of the fraction of charm and bottom hadron decays and unfolding of the invariant yield of parent charm and bottom hadrons. The nuclear-modification factors RAA for electrons from charm and bottom hadron decays and heavy-flavor hadrons show both a centrality and a quark-mass dependence, indicating suppression in the quark-gluon plasma produced in these collisions that is medium sized and quark-mass dependent.
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Transverse single-spin asymmetry of charged hadrons at forward and backward rapidity in polarized p + p , p + Al , and p + Au collisions at s N N = 200 GeV
Not Available
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Erratum: LΓ©vy-stable two-pion Bose-Einstein correlations in s N N = 200 GeV Au + Au collisions [Phys. Rev. C 97 , 064911 (2018)]
We previously published in 2018 a detailed measurement recorded in 2010 for Au+Au collisions at $\sqrt{^SNN}$ = 200 GeV of charged two-pion correlation functions in 0%-30% centrality. We found the data to be well described by Bose-Einstein correlation functions stemming from L$\acute{e}$vy-stable source distributions. Using a fine transverse momentum binning, we extracted the correlation strength parameter Ξ», the L$\acute{e}$vy index of stability Ξ± and the L$\acute{e}$vy length scale parameter R as a function of average transverse mass of the pair m T .
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Measurement of Direct-Photon Cross Section and Double-Helicity Asymmetry at s = 510 GeV in p β + p β Collisions
Not Available
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Transverse single-spin asymmetry of midrapidity Ο 0 and Ξ· mesons in p + Au and p + Al collisions at s N N = 200 GeV
Not Available
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Improving constraints on gluon spin-momentum correlations in transversely polarized protons via midrapidity open-heavy-flavor electrons in p β + p collisions at s = 200 GeV
Not Available
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Inclusive jet and hadron suppression in a multistage approach
We present a new study of jet interactions in the quark-gluon plasma created in high-energy heavy-ion collisions, using a multistage event generator within the jetscape framework. We focus on medium-induced modifications in the rate of inclusive jets and high transverse momentum (high-p T ) hadrons. Scattering-induced jet energy loss is calculated in two stages: a high virtuality stage based on the matter model, in which scattering of highly virtual partons modifies the vacuum radiation pattern, and a second stage at lower jet virtuality based on the LBT model, in which leading partons gain and lose virtuality by scattering and radiation. Coherence effects that reduce the medium-induced emission rate in the matter phase are also included. The TRENTO model is used for initial conditions, and the (2 + 1)dimensional VISHNU model is used for viscous hydrodynamic evolution. Jet interactions with the medium are modeled via 2-to-2 scattering with Debye screened potentials, in which the recoiling partons are tracked, hadronized, and included in the jet clustering. Holes left in the medium are also tracked and subtracted to conserve transverse momentum. Calculations of the nuclear modification factor (R AA ) for inclusive jets and high-p T hadrons are compared to experimental measurements at the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC). Within this framework, we find that with one extra parameter which codifies the transition between stages of jet modificationβalong with the typical parameters such as the coupling in the medium, the start and stop criteria, etc.βwe can describe these data at all energies for central and semicentral collisions without a rescaling of the jet transport coefficient q.
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Low-$p_T$ direct-photon production in Au + Au collisions at $\sqrt{s_{NN}}$ = 39 and 62.4 GeV
Here, the measurement of direct photons from Au + Au collisions at $\sqrt{s_{NN}}$ = 39 and 62.4 GeV in the transverse-momentum range 0.4 < $p_T$ < 3 Gev/c is presented by the PHENIX collaboration at the BNLRelativistic Heavy Ion Collider. A significant direct-photon yield is observed in both collision systems. A universal scaling is observed when the direct-photon $p_T$ spectra for different center-of-mass energies and for different centrality selections at $\sqrt{s_{NN}}$ = 62.4 GeV is scaled with $(dN_{\text{ch}}/dΞ·)^Ξ±$ for Ξ± = 1.21 Β± 0.04. This scaling also holds true for direct-photon spectra from Au + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV measured earlier by PHENIX, as well as the spectra from Pb + Pb at $\sqrt{s_{NN}}$ = 2760 GeV published by ALICE. The scaling power Ξ± seems to be independent of $p_T$, center of mass energy, and collision centrality. The spectra from different collision energies have a similar shape up to $p_T$ of 2 Gev/c. The spectra have a local inverse slope $T_{\text{eff}}$ increasing with $p_T$ of 0.174 Β± 0.018 Gev/c in the range 0.4 < $p_T$ < 1.3 Gev/c and increasing to 0.289 Β± 0.024 Gev/c for 0.9 < $p_T$ < 2.1 Gev/c. The observed similarity of low-$p_T$ direct-photon production from $\sqrt{s_{NN}}$ = 39 to 2760 GeV suggests a common source of direct photons for the different collision energies and event centrality selections, and suggests a comparable space-time evolution of direct-photon emission.
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Measurements of second-harmonic Fourier coefficients from azimuthal anisotropies in p + p , p + Au , d + Au , and He 3 + Au collisions at s N N = 200 GeV
Recently, the PHENIX Collaboration has published second- and third-harmonic Fourier coefficients v 2 and v 3 for midrapidity (|Ξ·|< 0.35 ) charged hadrons in 0%β5% central p+Au, d+Au, and 3 He+Au collisions at $\sqrt{s_{NN}}$= 200 GeV, utilizing three sets of two-particle correlations for two detector combinations with different pseudorapidity acceptance [Acharya et al., Phys. Rev. C 105, 024901 (2022)]. Here, this paper extends these measurements of v 2 to all centralities in p+Au, d+Au, and 3 He+Au collisions, as well as p+p collisions, as a function of transverse momentum (p T ) and event multiplicity. The kinematic dependence of v 2 is quantified as the ratio R of v 2 between the two detector combinations as a function of event multiplicity for 0.5 < p T <1 and 2 T < 2.5 GeV/c. A multiphase-transport (AMPT) model can reproduce the observed v 2 in most-central to midcentral d Au and 3 He+Au collisions. However, the AMPT model systematically overestimates the measurements in p+p, p+Au, and peripheral d+Au and 3 He+Au collisions, indicating a higher nonflow contribution in the AMPT model than in the experimental data. The AMPT model fails to describe the observed R for 0.5 < p T < 1 GeV/c , but there is qualitative agreement with the measurements for 2 < p T < 2.5 GeV/c.
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Measurement of Ο-meson production in Cu + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and U + U collisions at $\sqrt{s_{NN}}$ = 193 GeV
The PHENIX experiment reports systematic measurements at the Relativistic Heavy Ion Collider of Ο-meson production in asymmetric Cu + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and in U + U collisions at $\sqrt{s_{NN}}$ = 193 GeV. Measurements were performed via the Ο β K + K β decay channel at midrapidity |Ξ·| < 0.35. Features of Ο- meson production measured in Cu + Cu, Cu + Au, Au + Au, and U + U collisions were found to not depend on the collision geometry, which was expected because the yields are averaged over the azimuthal angle and follow the expected scaling with nuclear-overlap size. The elliptic flow of the Ο meson in Cu + Au, Au + Au, and U + U collisions scales with second-order-participant eccentricity and the length scale of the nuclear-overlap region (estimated with the number of participating nucleons). At moderate $p_T$ , Ο-meson production measured in Cu + Au and U + U collisions is consistent with coalescence-model predictions, whereas at high $p_T$ the production is in agreement with expectations for in-medium energy loss of parent partons prior to their fragmentation. Finally, the elliptic flow for Ο mesons measured in Cu + Au and U + U collisions is well described by a (2+1)-dimensional viscous-hydrodynamic model with specific-shear viscosity Ξ·/s = 1/4Ο.
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Role of bulk viscosity in deuteron production in ultrarelativistic nuclear collisions
Not Available
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Ο meson production in Ο + Al, Ο + Au, d + Au , and 3 He + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV
We report small nuclear collisions are mainly sensitive to cold-nuclear-matter effects; however, the collective behavior observed in these collisions shows a hint of hot-nuclear-matter effects. The identified-particle spectra, especially the Ο mesons which contain strange and antistrange quarks and have a relatively small hadronic-interaction cross section, are a good tool to study these effects. The PHENIX experiment has measured Ο mesons in a specific set of small collision systems p+Al, p+Au, and 3 He+Au, as well as d+Au at $\sqrt{s_{NN}}$=200 GeV. The transverse-momentum spectra and nuclear-modification factors are presented and compared to theoretical-model predictions. The comparisons with different calculations suggest that quark-gluon plasma may be formed in these small collision systems at $\sqrt{s_{NN}}$=200 GeV. However, the volume and the lifetime of the produced medium may be insufficient for observing strangeness-enhancement and jet-quenching effects. The comparison with calculations suggests that the main production mechanisms of Ο mesons at midrapidity may be different in p+Al versus p/d/ 3 He+Au collisions at $\sqrt{s_{NN}}$=200 GeV. While thermal quark recombination seems to dominate in p/d/ 3 He+Au collisions, fragmentation seems to be the main production mechanism in p+Al collisions.
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Measurement of Ο ( 2 S ) nuclear modification at backward and forward rapidity in p + p , p + Al , and p + Au collisions at s N N = 200 GeV
Suppression of the J/Ο nuclear-modification factor has been seen as a trademark signature of final-state effects in large collision systems for decades. In small systems, the nuclear modification was attributed to cold-nuclear-matter effects until the observation of strong differential suppression of the Ο(2S) state in p+A and d+A collisions suggested the presence of final-state effects. Results of J/Ο and Ο(2S) measurements in the dimuon decay channel are presented here for p+p, p+Al, and p+Au collision systems at $\sqrt{^{S}NN}$ = 200 GeV. The results are predominantly shown in the form of the nuclear-modification factor, R pA , the ratio of the Ο(2S) invariant yield per nucleon-nucleon collision in collisions of proton on target nucleus to that in p+p collisions. Finally, measurements of the J/Ο and Ο(2S) nuclear-modification factor are compared with shadowing and transport-model predictions, as well as to complementary measurements at Large-Hadron-Collider energies.
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ