Azimuthal anisotropy of direct photons in Au+Au collisions at βsNN=200GeV
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73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Engineering topics
Bai, M.
Publications and source records attributed to Bai, M..
Erratum: Centrality-Dependent Modification of Jet-Production Rates in Deuteron-Gold Collisions at $\sqrt{π _{πβ’π}}$ = 200 GeV [Phys. Rev. Lett. 116, 122301 (2016)]
We previously reported jet-production rates in π + π and π + Au collisions at $\sqrt{π _{πβ’π}}$ = 200 GeV recorded in 2008 with the PHENIX detector at the Relativistic Heavy Ion Collider. Subsequently, we found that electronic noise in the electromagnetic calorimeter was not completely removed by the tower-timing cuts used in the analysis. We have conducted an independent re-analysis of the data that eliminated noisy towers by removing them completely from the analysis. These cuts remove any contributions from instrumental noise, but reduce the overall acceptance for electromagnetic clusters by β16% and hence the overall statistical power of the data. Finally, this re-analysis found that instrumental noise in the electromagnetic calorimeter led to an artificial increase in the jet yield for both the π + π and π + Au collisions.
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Jet modification via π 0 -hadron correlations in Au + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV
High-momentum two-particle correlations are a useful tool for studying jet-quenching effects in the quark-gluon plasma. Angular correlations between neutral-pion triggers and charged hadrons with transverse momenta in the range 4β12 GeV/π and 0.5β7 GeV/π, respectively, have been measured by the PHENIX experiment in 2014 for Au + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. Suppression is observed in the yield of high-momentum jet fragments opposite the trigger particle, which indicates jet suppression stemming from in-medium partonic energy loss, while enhancement is observed for low-momentum particles. The ratio and differences between the yield in Au + Au collisions and π + π collisions, πΌ π΄β’π΄ and Ξ π΄β’π΄ , as a function of the trigger-hadron azimuthal separation, Ξβ’π, are measured for the first time at the BNL Relativistic Heavy Ion Collider. Finally, these results better quantify how the yield of low-π π associated hadrons is enhanced at wide angle, which is crucial for studying energy loss as well as medium-response effects.
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
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
Fundamental understanding of magnetic vortex dynamics on superconducting qubits for quantum computing
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDSβ
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
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
Ultimate Limit of Future Colliders
With seven operational colliders in the world and two under construction, the international particle physics community not only actively explores options for the next facilities for detailed studies of the Higgs/electroweak physics and beyond-the-LHC energy frontier, but also seeks a clear picture of the limits of the colliding beams method. In this paper, we try to consolidate various recent efforts in identifying physics limits of colliders in conjunction with societal sustainability, and share our thoughts about the perspective of reaching the ultimate collider that is at the quantum limit.
43 PARTICLE ACCELERATORSβ
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
Systematic study of nuclear effects in p + Al , p + Au , d + Au , and He 3 + Au collisions at s N N = 200 GeV using Ο 0 production
The PHENIX Collaboration presents a systematic study of inclusive Ο 0 production from p + p , p + Al , p + Au , d + Au , and He 3 + Au collisions at s N N = 200 GeV . Measurements were performed with different centrality selections as well as the total inelastic, 0β100%, selection for all collision systems. For 0β100% collisions, the nuclear-modification factors, R x A , are consistent with unity for p T above 8 GeV / c , but exhibit an enhancement in peripheral collisions and a suppression in central collisions. The enhancement and suppression characteristics are similar for all systems for the same centrality class. It is shown that for high- p T - Ο 0 production, the nucleons in the d and He 3 interact mostly independently with the Au nucleus and that the counterintuitive centrality dependence is likely due to a physical correlation between multiplicity and the presence of a hard scattering process. These observations disfavor models where parton energy loss has a significant contribution to nuclear modifications in small systems. Nuclear modifications at lower p T resemble the Cronin effectβan increase followed by a peak in central or inelastic collisions and a plateau in peripheral collisions. The peak height has a characteristic ordering by system size as p + Au > d + Au > He 3 + Au > p + Al . For collisions with Au ions, current calculations based on initial-state cold nuclear matter effects result in the opposite order, suggesting the presence of other contributions to nuclear modifications, in particular at lower p T .
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Strategies in Education, Outreach, and Inclusion to Enhance the US Workforce in Accelerator Science and Engineering
We summarize the community-based consensus for improvements concerning education, public outreach, and inclusion in Accelerator Science and Engineering that will enhance the workforce in the USA. The improvements identified reflect the product of discussions held within the 2021-2022 Snowmass community planning process by topical group AF1: Beam Physics and Accelerator Education within the Accelerator Frontier. Although the Snowmass process centers on high-energy physics, this document outlines required improvements for the entire U.S. accelerator science and engineering enterprise because education of those entering and in the field, outreach to the public, and inclusion are inextricably linked.
43 PARTICLE ACCELERATORSβ
Kinematic dependence of azimuthal anisotropies in p + Au , d + Au , and He 3 + Au at s N N = 200 GeV
Not Available
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ
Production of $Ο^0$ and $\eta$ mesons in $\mathrm{U+U}$ collisions at $\sqrt {s_{NN}} = 192$ $\mathrm {GeV}$
The PHENIX experiment at the Relativistic Heavy Ion Collider measured $Ο^0$ and $\eta$ mesons at midrapidity in $\mathrm{U+U}$ collisions at $\sqrt {s_{NN}} = 192$ $\mathrm {GeV}$ in a wide transverse momentum range. Measurements were performed in the $Ο^0(Ξ·) β Ξ³Ξ³$ decay modes. A strong suppression of $Ο^0$ and $\eta$ meson production at high transverse momentum was observed in central $\mathrm{U+U}$ collisions relative to binary scaled p + p results. Yields of $Ο^0$ and $\eta$ mesons measured in $\mathrm{U+U}$ collisions show similar suppression pattern to those measured in Au + Au collisions at $\sqrt {s_{NN}} = 200$ $\mathrm {GeV}$ for similar numbers of participant nucleons. The $Ξ·/Ο^0$ ratios do not show dependence on centrality or transverse momentum and are consistent with previously measured values in hadron-hadron, hadron-nucleus, nucleus-nucleus, and $e^+e^-$ collisions.
73 NUCLEAR PHYSICS AND RADIATION PHYSICSβ