Mon·Apr 10, 2023Monday·April 10, 2023

1. 01*

   Observation of the electromagnetic field effect via charge-dependent directed flow in heavy-ion collisions at the Relativistic Heavy Ion Collider

   STAR Collaboration: M. I. Abdulhamid🇪🇬 · B. E. Aboona🇺🇸 · J. Adam🇨🇿 · J. R. Adams🇺🇸 · G. Agakishiev🇷🇺 · I. Aggarwal🇮🇳 · M. M. Aggarwal🇮🇳 · Z. Ahammed🇮🇳 · A. Aitbaev🇷🇺 · I. Alekseev🇷🇺 · E. Alpatov🇷🇺 · A. Aparin🇷🇺 and 343 other authors

   The deconfined quark-gluon plasma (QGP) created in relativistic heavy-ion collisions enables the exploration of the fundamental properties of matter under extreme conditions. Non-central collisions can produce strong magnetic fields on the order of $10^{18}$ Gauss, which offers a probe into the electrical conductivity of the QGP. In particular, quarks and anti-quarks carry opposite charges and receive contrary electromagnetic forces that alter their momenta. This phenomenon can be manifested in the collective motion of final-state particles, specifically in the rapidity-odd directed flow, denoted as $v_1(\mathsf{y})$. Here we present the charge-dependent measurements of $d{v}_1/d\mathsf{y}$ near midrapidities for ${\pi }^{\pm }$, $K^{\pm }$, and $p(\bar{p})$ in Au+Au and isobar (${}_{44}^{96}$Ru+${}_{44}^{96}$Ru and ${}_{40}^{96}$Zr+${}_{40}^{96}$Zr) collisions at $\sqrt{s_{\mathrm{NN}}}=$ 200 GeV, and in Au+Au collisions at 27 GeV, recorded by the STAR detector at the Relativistic Heavy Ion Collider. The combined dependence of the $v_1$ signal on collision system, particle species, and collision centrality can be qualitatively and semi-quantitatively understood as several effects on constituent quarks. While the results in central events can be explained by the $u$ and $d$ quarks transported from initial-state nuclei, those in peripheral events reveal the impacts of the electromagnetic field on the QGP. Our data put valuable constraints on the electrical conductivity of the QGP in theoretical calculations.

   nucl-exhep-exPRX(2024)·87 citations
2. 02*

   Fundamental Symmetries, Neutrons, and Neutrinos (FSNN): Whitepaper for the 2023 NSAC Long Range Plan

   B. Acharya🇺🇸 · C. Adams🇺🇸 · A.A. Aleksandrova🇺🇸 · K. Alfonso🇺🇸 · P. An🇺🇸 · S. Baeßler🇺🇸 · A.B. Balantekin🇺🇸 · P.S. Barbeau🇺🇸 · F. Bellini🇮🇹 · V. Bellini🇮🇹 · R.S. Beminiwattha🇺🇸 · J.C. Bernauer🇺🇸 and 167 other authors

   This whitepaper presents the research priorities decided on by attendees of the 2022 Town Meeting for Fundamental Symmetries, Neutrons and Neutrinos, which took place December 13-15, 2022 in Chapel Hill, NC, as part of the Nuclear Science Advisory Committee (NSAC) 2023 Long Range Planning process. A total of 275 scientists registered for the meeting. The whitepaper makes a number of explicit recommendations and justifies them in detail.

   nucl-exnucl-th18 citations
3. 03*

   Prospects for GPDs extraction with Double DVCS

   K. Deja🇵🇱 · V. Martinez-Fernandez🇵🇱 · B. Pire🇫🇷 · P. Sznajder🇵🇱 · J. Wagner🇵🇱

   Double deeply virtual Compton scattering (DDVCS) is the process where an electron scatters off a nucleon and produces a lepton pair. The main advantage of this process in contrast with deeply virtual and timelike Compton scatterings (DVCS and TCS) is the possibility of directly measuring GPDs for $x\ne \pm \xi$ at leading order in ${\alpha }_s$ (LO). We present a new calculation of the DDVCS amplitude based on the methods developed by R. Kleiss and W. J. Stirling in the 1980s. These techniques produce expressions for amplitudes that are perfectly suited for implementation in numerical simulations. Via the PARTONS software, the correctness of this new formulation has been tested by comparing the DVCS and TCS limits of DDVCS with independent calculations of DVCS and TCS.

   ↳ hep-phhep-exnucl-exnucl-thActa Phys.Polon.Supp.(2023)·5 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.