Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2610.19680

Probing the production mechanisms of virtual photons at RHIC

STAR Collaboration
View original source ↗Read source document ↗Export metadata ↓

Abstract

We report the measurement of direct virtual photon ($γ^*_\text{dir} \rightarrow e^+e^-$) in four Au+Au collision energies at $\sqrt{s_\text{NN}}$ = 14.6--54.4 GeV. The $γ^*_\text{dir}$ yields scale with charged-particle multiplicity ($(dN_{\mathrm{ch}}/dη)^α$) as $α=1.43 \pm 0.04 \text{(stat.)} \pm 0.03\text{(sys.)}$, independent of collision energies and centralities, exceeding hadronic expectations and indicating notable contribution from QGP phase. At $\sqrt{s_{\rm NN}}=$ 54.4 GeV, the direct virtual photon mass distributions are further studied over $0.1 < M_{ee} < 1.1$ GeV/$c^2$, and are found to evolve from exponential to power-law form with increasing $p_\text{T}$, signaling a shift from "blackbody" radiation to emission governed by Kroll-Wada formalism.

Explore related subjects

nucl-ex

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

STAR Collaboration. 2026-10-14. Probing the production mechanisms of virtual photons at RHIC. https://arxiv.org/abs/2610.19680

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Experimental Review on Bulk Properties and Light/Strange Hadron Production in Heavy-Ion Collisions

This proceedings article reviews recent experimental results on bulk properties and light/strange hadron production in heavy-ion collisions, presented at the Strangeness in Quark Matter 2026 conference. The discussion covers the QCD phase diagram, extraction of the temperature-dependent speed of sound, radial flow fluctuations probed by $v_0(p_T)$, anisotropic flow in small collision systems, strange hadron yields across system sizes, nuclear modification factors, and collectivity signatures at high baryon density. Results from the STAR, CMS, ALICE, ATLAS, PHENIX, NA61/SHINE, and HADES collaborations are synthesized to highlight recent progress in understanding the properties of the Quark-Gluon Plasma and the nature of the QCD phase transition.

nucl-ex↗
arXiv2026

Physics with Radioactive Ion Beams at the Nuclear Science Laboratory

The University of Notre Dame is home to a rich history of nuclear science efforts, including some of the earliest developments in the production and creation of radioactive ion beams (RIBs). The resulting TwinSol facility stands as the longest continuously-operating RIB facility in the United States, and has enabled a wide range of experimental efforts in nuclear structure, astrophysics and fundamental symmetries through in-flight RIBs one to two nucleons from stability. A recent upgrade to TwinSol via a third solenoid constituted the founding of the TriSol facility, which provides cleaner, better-focused RIBs to downstream experiments. In this paper, we present a summary of RIB science at the Nuclear Science Laboratory (NSL) with both TwinSol and TriSol and discuss recent upgrades and future experimental plans at the facilities.

nucl-ex↗
arXiv2026

$^{16}$O(p,$γ$)$^{17}$F Reaction and the C and O Isotopic Ratios in Red Giant Branch Stars

The $^{16}$O/$^{17}$O isotopic ratio is a widely used tracer of nucleosynthesis and mixing processes in red giant stars. Its value depends on the rates of the proton-capture reactions responsible for the production and destruction of $^{16}$O and $^{17}$O among which the $^{16}$O(p,$γ$)$^{17}$F reaction plays a central role, as it involves both isotopes. This work reports on a new measurement of the $^{16}$O(p,$γ$)$^{17}$F cross section carried out at the Laboratory for Underground Nuclear Astrophysics (LUNA) over a center-of-mass energy range of 200 - 380 keV, a region previously unexplored by experimental studies. Two complementary techniques were employed: prompt gamma-ray detection and activation. The results obtained with the two techniques are consistent within experimental uncertainties. From the measured cross sections and existing literature data, we evaluate a new thermonuclear reaction rate, which is then used to demonstrate how simultaneous measurements of stellar carbon and oxygen isotopic ratios constrain the initial mass and the extent of the mixing events in red giant branch stars. In particular, we demonstrate how the $^{12}$C/$^{13}$C abundance ratio is primarily sensitive to the temperature T$_{\textrm{max}}$ attained during mixing, whereas the $^{16}$O/$^{17}$O abundance ratio is highly sensitive to the initial stellar mass M$_i$. Therefore, simultaneous measurements of these isotopic ratios can disentangle and place stringent constraints on M$_i$ and T$_{\textrm{max}}$, and the remaining uncertainty is now dominated by stellar abundance measurements rather than nuclear-physics inputs.

nucl-ex↗