Mon·Sep 4, 2023Monday·September 4, 2023

1. 01*

   Semi-inclusive direct photon+jet and ${\pi }^0$+jet correlations measured in $p+p$ and central Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV

   The STAR Collaboration

   The STAR experiment at RHIC reports new measurements of jet quenching based on the semi-inclusive distribution of charged-particle jets recoiling from direct photon (${\gamma }_{\mathrm{dir}}$) and neutral pion (${\pi }^0$) triggers in pp and central Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV, for triggers in the range $9<E_{\mathrm{T}}^{\mathrm{trig}}<20$ GeV. The datasets have integrated luminosities of 3.9${\mathrm{nb}}^{-1}$ for Au+Au and 23${\mathrm{pb}}^{-1}$ for pp collisions. Jets are reconstructed using the anti-$k_{\mathrm{T}}$ algorithm with resolution parameters $R$=0.2 and 0.5. The large uncorrelated jet background in central Au+Au collisions is corrected using a mixed-event approach, which enables precise charged-particle jet measurements at low transverse momentum $p_{\mathrm{T},\mathrm{jet}}^{\mathrm{ch}}$ and large $R$. Recoil-jet distributions are reported in the range $p_{\mathrm{T},\mathrm{jet}}^{\mathrm{ch}}<25$ \gev. Comparison of the distributions measured in pp and Au+Au collisions reveals strong medium-induced jet yield suppression for $R=0.2$, with markedly less suppression for $R=0.5$. Comparison is also made to theoretical models incorporating jet quenching. These data provide new insight into the mechanisms underlying jet quenching and the angular dependence of medium-induced jet-energy transport, and provide new constraints on modelling such effects.

   nucl-exhep-exhep-phnucl-thPRC(2025)·21 citations
2. 02*

   Measurement of in-medium jet modification using direct photon+jet and ${\pi }^0$+jet correlations in $p+p$ and central Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV

   STAR Collaboration

   The STAR Collaboration presents measurements of the semi-inclusive distribution of charged-particle jets recoiling from energetic direct-photon (${\gamma }_{\mathrm{dir}}$) and neutral-pion (${\pi }^0$) triggers in p+p and central Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ GeV over a broad kinematic range, for jet resolution parameters $R$=0.2 and 0.5. Medium-induced jet yield suppression is observed to be larger for $R$=0.2 than for 0.5, reflecting the angular range of jet energy redistribution due to quenching. The predictions of model calculations incorporating jet quenching are not fully consistent with the observations. These results provide new insight into the physical origins of jet quenching.

   nucl-exhep-exhep-phnucl-thPRL(2025)·21 citations
3. 03*

   Development of wide range photon detection system for muonic X-ray spectroscopy

   R. Mizuno🇯🇵 · M. Niikura🇯🇵 · T.Y. Saito🇯🇵 · T. Matsuzaki🇯🇵 · H. Sakurai🇯🇵 · A. Amato🇨🇭 · S. Asari · S. Biswas · I. Chiu🇹🇼 · L. Gerchow · Z. Guguchia · G. Janka🇨🇭 and 7 other authors

   We have developed a photon detection system for muonic X-ray spectroscopy. The detector system consists of high-purity germanium detectors with BGO Compton suppressors. The signals from the detectors are readout with a digital acquisition system. The absolute energy accuracy, energy and timing resolutions, photo-peak efficiency, the performance of the Compton suppressor, and high count rate durability are studied with standard $\gamma$-ray sources and in-beam experiment using ${}^{27}\mathrm{Al}(p,\gamma ){}^{28}\mathrm{Si}$ resonance reaction. The detection system was demonstrated at Paul Scherrer Institute. A calibration method for a photon detector at a muon facility using muonic X-rays of ${}^{197}$Au and ${}^{209}$Bi is proposed.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2024)·8 citations
4. 04*

   Dilepton polarization as a signature of plasma anisotropy

   Maurice Coquet🇫🇷 · Xiaojian Du🇪🇸 · Jean-Yves Ollitrault🇫🇷 · Soeren Schlichting🇩🇪 · Michael Winn🇫🇷

   We propose the angular distribution of lepton pairs produced in ultrarelativistic heavy-ion collisions as a probe of thermalization of the quark-gluon plasma. We focus on dileptons with invariant masses large enough that they are produced through quark-antiquark annihilation in the early stages of the collision. The angular distribution of the lepton in the rest frame of the pair then reflects the angular distribution of quark momenta. At early times, the transverse pressure of the quark-gluon plasma is larger than its longitudinal pressure as a result of the fast longitudinal expansion, which results in an oblate lepton distribution. By contrast, direct (Drell-Yan) production by quarks and antiquarks from incoming nuclei, whose momenta are essentially longitudinal, results in a prolate distribution. As the invariant mass increases, Drell-Yan gradually becomes the dominant source of dilepton production, and the lepton distribution evolves from oblate to prolate. The invariant mass at which the transition occurs is highly sensitive to the equilibration time of the quark-gluon plasma or, equivalently, the shear viscosity over entropy ratio $\eta /s$ in the early stages of the collision.

   ↳ nucl-thhep-exhep-phnucl-exPRL(2024)·27 citations
5. 05*

   Bayesian location of the QCD critical point from a holographic perspective

   Mauricio Hippert🇺🇸 · Joaquin Grefa🇺🇸 · T. Andrew Manning🇺🇸 · Jorge Noronha🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸 · Israel Portillo Vazquez🇺🇸 · Claudia Ratti🇺🇸 · Romulo Rougemont🇧🇷 · Michael Trujillo🇺🇸

   A fundamental question in QCD is the existence of a phase transition at large doping of quarks over antiquarks. We present the first prediction of a QCD critical point (CP) from a Bayesian analysis constrained by first principle results at zero doping. We employ the gauge/gravity duality to map QCD onto a theory of dual black holes. Predictions for the CP location in different realizations of the model overlap at one sigma. Even if many prior samples do not include a CP, one is found in nearly 100\% of posterior samples, indicating a strong preference for a CP.

   ↳ nucl-thhep-phhep-thnucl-exPRD(2024)·121 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.