Thu·Aug 29, 2024Thursday·August 29, 2024

1. 01*

   Tracking the baryon number with nuclear collisions

   STAR Collaboration

   Baryon quantum number is believed to be conserved since baryogenesis in the early Universe. While fractionally charged valence quarks are understood conventionally to each carry a baryon number of 1/3, the baryon junction, a non-perturbative Y-shaped topology of neutral gluons, has also been proposed as an alternative entity tracing the baryon number. Neither scenario has been verified experimentally. The STAR Collaboration reports measurements at mid-rapidity of baryon number ($\mathbf{B}$) over the electric charge number difference ($\mathbf{\Delta }\mathbf{Q}$) in isobar nuclear collisions, and the net-proton yield along rapidity in photonuclear collisions. A larger $\mathbf{B}/\Delta \mathbf{Q}$ ratio and less asymmetric net-proton yield are observed than predicted from models assigning baryon number to valence quarks. These findings, corroborated by previous measurements in Au+Au collisions, disfavor the valence quark picture.

   nucl-exhep-exScience(2026)·21 citations
2. 02*

   Production and in-medium modification of $\varphi$ mesons in proton-nucleus reactions from a transport approach

   Philipp Gubler🇯🇵 · Masaya Ichikawa🇯🇵 · Taesoo Song🇩🇪 · Elena Bratkovskaya🇩🇪

   Production and in-medium modification of hidden strange $\varphi$ mesons are studied in proton-nucleus reactions - p+C, p+Cu and p+Pb - at 12 GeV/c, partially measured by the KEK E325 collaboration via the dilepton decay mode. This work is based on the off-shell microscopic Parton-Hadron-String Dynamics (PHSD) transport approach, which provides the dynamical description of strongly interacting hadronic and partonic degrees of freedom in dense matter, and especially makes it possible to simulate in-medium off-shell dynamics of the $\varphi$ meson in the reactions studied. Different in-medium scenarios for the modification of the $\varphi$ meson spectral function in nuclear matter are investigated: i) dropping pole mass, ii) collisional broadening and iii) simultaneous dropping pole mass and collisional broadening. Even though the $\varphi$ meson production in p+A reactions occurs only at densities around or below normal nuclear matter density ${\rho }_0$, we find visible modifications of the generated dilepton spectra for the in-medium scenarios compared to the vacuum distribution.

   ↳ hep-phhep-exnucl-exnucl-thPRC(2025)·14 citations
3. 03*

   Electron Scattering at the Intensity Frontier with SoLID

   Zein-Eddine Meziani🇺🇸

   The Solenoidal Large Intensity Device (SoLID) is a large acceptance spectrometer capable of operating at the luminosity frontier. It is proposed to fully exploit the scientific potential of the continuous electron beam accelerator facility (CEBAF) 12 GeV energy upgrade at Jefferson Lab. Its conceptual design is mature, having passed multiple reviews and been validated by a successful pre-R\&D phase. The envisioned scientific program consists of three avenues of research, namely the 3D momentum imaging of the structure of the nucleon, the origin of the proton mass through the gluonic gravitational form factors (GFFs), and the search of physics beyond the standard model of particle physics. These avenues are complemented by a growing supplemental list of run group experiments that address a variety of important topics.

   ↳ physics.ins-dethep-exhep-phnucl-exPoS(2025)·1 citation

* 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.