Mon·Apr 14, 2025Monday·April 14, 2025

1. 01*

   RHIC Program, Its Origin and Early Results

   Wit Busza · John W. Harris🇺🇸 · Shoji Nagamiya🇯🇵

   At the Brookhaven National Laboratory, experimental efforts with heavy-ion accelerators started at the AGS synchrotron in 1984 and then at the Relativistic Heavy Ion Collider (RHIC) in 1991. This chapter of a future book describes how several scientific collaborations were established and how features of the quark-gluon plasma were revealed from the four RHIC experiments during the first five years of RHIC operation.

   nucl-ex3 citations
2. 02*

   Search for jet quenching with dijets from high-multiplicity pPb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 8.16 TeV

   CMS Collaboration

   The first measurement of the dijet transverse momentum balance $x_j$ in proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of $\sqrt{s_{\mathrm{NN}}}$ = 8.16 TeV is presented. The $x_j$ observable, defined as the ratio of the subleading over leading jet transverse momentum in a dijet pair, is used to search for jet quenching effects. The data, corresponding to an integrated luminosity of 174.6 nb${}^{-1}$, were collected with the CMS detector in 2016. The $x_j$ distributions and their average values are studied as functions of the charged-particle multiplicity of the events and for various dijet rapidity selections. The latter enables probing hard scattering of partons carrying distinct nucleon momentum fractions $x$ in the proton- and lead-going directions. The former, aided by the high-multiplicity triggers, allows probing for potential jet quenching effects in high-multiplicity events (with up to 400 charged particles), for which collective phenomena consistent with quark-gluon plasma (QGP) droplet formation were previously observed. The ratios of $x_j$ distributions for high- to low-multiplicity events are used to quantify the possible medium effects. These ratios are consistent with simulations of the hard-scattering process that do not include QGP production. These measurements set an upper limit on medium-induced energy loss of the subleading jet of 1.26% of its transverse momentum at the 90% confidence level in high multiplicity pPb events.

   nucl-exhep-exJHEP(2025)·15 citations
3. 03*

   Kaon and Pion Fragmentation Functions

   Hui-Yu Xing🇨🇳 · Wen-Hao Bian🇨🇳 · Zhu-Fang Cui🇨🇳 · Craig D. Roberts🇨🇳

   The Drell-Levy-Yan relation is employed to obtain pion and kaon elementary fragmentation functions (EFFs) from the hadron-scale parton distribution functions (DFs) of these mesons. Two different DF sets are used: that calculated using a symmetry-preserving treatment of a vector $\times$ vector contact interaction (SCI) and the other expressing results obtained using continuum Schwinger function methods (CSMs). Thus determined, the EFFs serve as driving terms in a coupled set of hadron cascade equations, whose solution yields the complete array of hadron-scale fragmentation functions (FFs) for pion and kaon production in high energy reactions. After evolution to scales typical of experiments, the SCI and CSM FF predictions are seen to be in semiquantitative agreement. Importantly, they conform with a range of physical expectations for FF behaviour on the endpoint domains $z\simeq 0,1$, e.g., nonsinglet FFs vanish at $z=0$ and singlet FFs diverge faster than $1/z$. Predictions for hadron multiplicities in jets are also delivered. They reveal SU$(3)$ symmetry breaking in the charged-kaon/neutral-kaon multiplicity ratio, whose size diminishes with increasing reaction energy, and show that, with increasing energy, the pion/kaon ratio in $e^{+}{e}^{-}\to hX$ diminishes to a value that is independent of hadron masses.

   ↳ hep-phhep-exhep-latnucl-ex+1EPJC(2025)·18 citations
4. 04*

   Can the strong interactions between hadrons be determined using femtoscopy?

   Evgeny Epelbaum🇩🇪 · Sven Heihoff🇩🇪 · Ulf-G. Meißner🇩🇪 · Alexander Tscherwon🇩🇪

   In the last decades, femtoscopic measurements from heavy-ion collisions have become a popular tool to investigate the strong interactions between hadrons. The key observables measured in such experiments are the two-hadron momentum correlations, which depend on the production mechanism of hadron pairs and the final-state interactions. Given the complexity of ultra-relativistic collision experiments, the source term describing the production mechanism can only be modeled phenomenologically based on numerous assumptions. The commonly employed approach for analyzing femtoscopic data relies on the Koonin-Pratt formula, which relates the measured correlation functions with the relative wave function of an outgoing hadron pair and a source term that is assumed to be universal. Here, we critically examine this universality assumption and show that for strongly interacting particles such as nucleons, the interpretation of femtoscopic measurements suffers from a potentially large intrinsic uncertainty. We also comment on the ongoing efforts to explore three-body interactions using this experimental technique.

   ↳ nucl-thhep-exhep-lathep-ph+1PRL(2026)·27 citations
5. 05*

   The Early History of the Quark-Gluon Plasma

   W. Busza · W.A. Zajc🇺🇸

   We present the historical antecedents to the field of relativistic heavy ion physics, beginning with early attempts to model the strong interaction and ending with the endorsement of a relativistic heavy ion collider in the 1983 U.S. Long-Range Plan for Nuclear Science. Particular attention is paid to two major themes: 1) A program to study high density states of nuclear matter emerging from the 1974 Bear Mountain conference and 2) Efforts to understand the predictions of QCD for matter at high densities and/or temperatures.

   ↳ nucl-thhep-phnucl-ex3 citations
6. 06*

   The PUMA offline ion source beamline

   Moritz Schlaich🇩🇪 · Paul Fischer🇩🇪 · Paul Florian Giesel🇩🇪 · Clara Klink🇩🇪 · Alexandre Obertelli🇩🇪 · Lutz Schweikhard🇩🇪 · Frank Wienholtz🇩🇪

   The antiProton Unstable Matter Annihilation experiment (PUMA) at CERN aims to study the nucleonic composition in the matter density tail of stable and radioactive nuclei using low-energy antiprotons. Since there is no facility in which both low-energy antiprotons and radioactive nuclei can be produced, the experimental realization with exotic nuclei requires the transportation of the antiprotons from the Extra Low ENergy Antiproton (ELENA) facility to the nearby located Isotope mass Separator On-Line DEvice (ISOLDE). For tests and first applications of the proposed experimental technique to stable isotopes at ELENA, a dedicated offline ion source beamline was developed that will provide isotopically pure, cooled and bunched ion beams with intensities of more than $10^4$ ions per bunch while maintaining a vacuum of better than $5\times 10^{-10}$ mbar at the handover point. This offline ion source beamline is characterized and its capabilities are demonstrated using the example of stable krypton isotopes.

   ↳ physics.acc-phnucl-exNucl.Instrum.Meth.A(2025)·3 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.