Fri·Sep 9, 2022Friday·September 9, 2022

1. 01*

   Search for the Chiral Magnetic Effect in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=27$ GeV with the STAR forward Event Plane Detectors

   STAR Collaboration: B. E. Aboona🇺🇸 · J. Adam🇨🇿 · L. Adamczyk🇵🇱 · J. R. Adams🇺🇸 · I. Aggarwal🇮🇳 · M. M. Aggarwal🇮🇳 · Z. Ahammed🇮🇳 · D. M. Anderson🇺🇸 · E. C. Aschenauer🇺🇸 · J. Atchison🇺🇸 · V. Bairathi🇨🇱 · W. Baker🇺🇸 and 359 other authors

   A decisive experimental test of the Chiral Magnetic Effect (CME) is considered one of the major scientific goals at the Relativistic Heavy-Ion Collider (RHIC) towards understanding the nontrivial topological fluctuations of the Quantum Chromodynamics vacuum. In heavy-ion collisions, the CME is expected to result in a charge separation phenomenon across the reaction plane, whose strength could be strongly energy dependent. The previous CME searches have been focused on top RHIC energy collisions. In this Letter, we present a low energy search for the CME in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=27$ GeV. We measure elliptic flow scaled charge-dependent correlators relative to the event planes that are defined at both mid-rapidity $|\eta |<1.0$ and at forward rapidity $2.1<|\eta |<5.1$. We compare the results based on the directed flow plane (${\Psi }_1$) at forward rapidity and the elliptic flow plane (${\Psi }_2$) at both central and forward rapidity. The CME scenario is expected to result in a larger correlation relative to ${\Psi }_1$ than to ${\Psi }_2$, while a flow driven background scenario would lead to a consistent result for both event planes. In 10-50\% centrality, results using three different event planes are found to be consistent within experimental uncertainties, suggesting a flow driven background scenario dominating the measurement. We obtain an upper limit on the deviation from a flow driven background scenario at the 95\% confidence level. This work opens up a possible road map towards future CME search with the high statistics data from the RHIC Beam Energy Scan Phase-II.

   nucl-exhep-phnucl-thPLB(2023)·29 citations
2. 02*

   Exploring the neutron skin by hyperon-antihyperon production in antiproton-nucleus interactions

   Martin Christiansen🇩🇪 · Falk Schupp🇩🇪 · Patrick Achenbach🇩🇪 · Michael Bölting🇩🇪 · Josef Pochodzalla🇩🇪 · Marcell Steinen🇩🇪

   In this work we propose a new method to measure the evolution of the neutron skin thickness between different isotopes. We consider antiproton-nucleus interactions close to the production threshold of $\Lambda \overline{\Lambda }$ and $\Sigma \overline{\Lambda }$ pairs. At low energies, $\Lambda \overline{\Lambda }$ pairs are produced in p + p collisions, while $\Sigma \overline{\Lambda }$ pairs can only be produced in p + n interactions. Measuring these cross sections provides information on the neutron skin thickness

   nucl-exnucl-thEPJ Web Conf.(2022)·2 citations
3. 03*

   T-odd Leading-Twist Quark TMDs at Small $x$

   Yuri V. Kovchegov🇺🇸 · M. Gabriel Santiago🇺🇸

   We study the small-$x$ asymptotics of the flavor non-singlet T-odd leading-twist quark transverse momentum dependent parton distributions (TMDs), the Sivers and Boer-Mulders functions. While the leading eikonal small-$x$ asymptotics of the quark Sivers function is given by the spin-dependent odderon, we are interested in revisiting the sub-eikonal correction considered by us earlier. We first simplify the expressions for both TMDs at small Bjorken $x$ and then construct small-$x$ evolution equations for the resulting operators in the large-$N_c$ limit, with $N_c$ the number of quark colors. For both TMDs, the evolution equations resum all powers of the double-logarithmic parameter ${\alpha }_s{\ln }^2(1/x)$, where ${\alpha }_s$ is the strong coupling constant, which is assumed to be small. Solving these evolution equations numerically (for the Sivers function) and analytically (for the Boer-Mulders function) we arrive at the following leading small-$x$ asymptotics of these TMDs at large $N_c$: \begin{align} f_{1 \: T}^{\perp \: NS} (x \ll 1 ,k_T^2) & = C_O (x, k_T^2) \, \frac{1}{x} + C_1 (x, k_T^2) \, \left( \frac{1}{x} \right)^{3.4 \, \sqrt{\frac{\alpha_s \, N_c}{4 \pi}}} , \notag \\ h_1^{\perp \, \textrm{NS}} (x \ll 1, k_T^2) & = C (x, k_T^2) \left( \frac{1}{x} \right)^{-1}. \notag \end{align} The functions $C_O(x,k_T^2)$, $C_1(x,k_T^2)$, and $C(x,k_T^2)$ can be readily obtained in our formalism: they are mildly $x$-dependent and do not strongly affect the power-of-$x$ asymptotics shown above. The function $C_O$, along with the $1/x$ factor, arises from the odderon exchange. For the sub-eikonal contribution to the quark Sivers function (the term with $C_1$), our result shown above supersedes the one obtained in our previous work due to the new contributions identified recently.

   ↳ hep-phhep-exnucl-exnucl-thJHEP(2022)·42 citations
4. 04*

   Spin polarization measurements in relativistic heavy-ion collisions

   Debojit Sarkar🇺🇸

   The hot and dense matter formed in relativistic heavy-ion collisions at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) is termed quark-gluon plasma (QGP). The evolution of the medium is characterized by non-trivial velocity and vorticity fields, resulting in the polarization of the produced particles. The spin polarization, being sensitive to the hydrothermal (flow velocity and temperature) gradients, is unique compared to conventional observables that are sensitive to the hydrothermal fields only. Hence, the recent measurements of global and local hyperon spin polarization and vector meson spin alignment by the LHC and STAR collaborations provide a unique opportunity to probe the QGP substructure with finer details.

   ↳ hep-exhep-phnucl-exnucl-th+1Acta Phys.Polon.Supp.(2023)·0 citations
5. 05*

   Random statistical analysis of transverse momentum spectra of strange particles and dependence of related parameters on centrality in high energy collisions at the LHC

   Xu-Hong Zhang🇨🇳 · Fu-Hu Liu🇨🇳 · Khusniddin K. Olimov🇺🇿 · Airton Deppman🇧🇷

   We have studied the transverse momentum ($p_T$) spectra of the final-state strange particles, including $K^{\pm }$, $\varphi$, $\Xi$, and $\Omega$, produced in high energy lead-lead (Pb-Pb), proton-lead ($p$-Pb), xenon-xenon (Xe-Xe) collisions at the Large Hadron Collider (LHC). Taking into account the contribution of multi-quark composition, whose probability density distribution is described by the modified Tsallis-Pareto-type function, we simulate the $p_T$ spectra of the final-state strange particles by a Monte Carlo method, which is shown to be in good agreement with the experimental data in most the cases. The kinetic freeze-out parameters are obtained. The present method provides a new tool for studying the spectra of various particles produced in high energy collisions, reflecting more realistically the collision process, which is of great significance to study the formation and properties of the produced particles.

   ↳ hep-phhep-exnucl-exnucl-thAdv.High Energy Phys.(2022)·2 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.