Tue·Aug 3, 2021Tuesday·August 3, 2021

1. 01*

   Global $\Lambda$-hyperon polarization in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=3$ GeV

   M. S. Abdallah · B. E. Aboona · J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · I. Aggarwal · M. M. Aggarwal · Z. Ahammed · I. Alekseev · D. M. Anderson and 385 other authors

   Global hyperon polarization, ${\overline{P}}_{\mathrm{H}}$, in Au+Au collisions over a large range of collision energy, $\sqrt{s_{\mathrm{NN}}}$, was recently measured and successfully reproduced by hydrodynamic and transport models with intense fluid vorticity of the quark-gluon plasma. While naïve extrapolation of data trends suggests a large ${\overline{P}}_{\mathrm{H}}$ as the collision energy is reduced, the behavior of ${\overline{P}}_{\mathrm{H}}$ at small $\sqrt{s_{\mathrm{NN}}}<7.7$ GeV is unknown. Operating the STAR experiment in fixed-target mode, we measured the polarization of $\Lambda$ hyperons along the direction of global angular momentum in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=3$ GeV. The observation of substantial polarization of $4.91\pm 0.81(stat.)\pm 0.15(syst.)$% in these collisions may require a reexamination of the viscosity of any fluid created in the collision, of the thermalization timescale of rotational modes, and of hadronic mechanisms to produce global polarization.

   nucl-exPRC(2021)·162 citations
2. 02*

   Role of ambient humidity underestimated in research on correlation between radioactive decay rates and space weather

   Stefaan Pommé · Krzysztof Pelczar🇵🇱

   In recent work, Milian-Sanchez et al. observed fluctuations in radioactive decay rate measurement series, and after excluding environmental influences (measured indoors) as root causes, they looked for possible correlations with astrophysical variables. In spite of the authors efforts to investigate possible influences of environmental parameters (such as ambient temperature, pressure and humidity) on the detectors stability, it turns out that the influence of ambient humidity on the instrumentation has been underestimated.

   nucl-exastro-ph.IMSci.Rep.(2022)·4 citations
3. 03*

   Measurement of Transverse Spin Dependent Azimuthal Correlations of Charged Pion(s) in $p^{\uparrow }p$ Collisions at $\sqrt{s}=200$ GeV at STAR

   Babu R. Pokhrel🇺🇸

   At the leading twist, the transversity distribution function, $h_1^q(x)$, where $x$ is the longitudinal momentum fraction of the proton carried by quark $q$, encodes the transverse spin structure of the nucleon. Extraction of it is difficult because of its chiral-odd nature. In transversely polarized proton-proton collisions ($p^{\uparrow }p$), $h_1^q(x)$ can be coupled with another chiral-odd partner, a spin-dependent fragmentation function (FF). The resulting asymmetries in hadron(s) azimuthal correlations directly probe $h_1^q(x)$. We report the measurement of correlation asymmetries for charged pion(s) in $p^{\uparrow }p$, through the Collins and the Interference FF channel.

   nucl-exSciPost Phys.Proc.(2022)·1 citation
4. 04*

   Recent Heavy-Flavor Results from STAR

   Guannan Xie (for the STAR Collaboration)🇺🇸

   In these proceedings, we report on the production of various open heavy-flavor hadrons and quarkonia in Au+Au collisions at sNN = 200GeV from the STAR experiment.

   nucl-exhep-exSpringer Proc.Phys.(2020)·0 citations
5. 05*

   Disappearance of partonic collectivity in $\sqrt{s_{NN}}$ = 3 GeV Au+Au collisions at RHIC

   STAR Collaboration: M. S. Abdallah · B. E. Aboona · J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · I. Aggarwal · M. M. Aggarwal · Z. Ahammed · I. Alekseev · D. M. Anderson and 385 other authors

   We report on the measurements of directed flow $v_1$ and elliptic flow $v_2$ for hadrons (${\pi }^{\pm }$, $K^{\pm }$, $K_S^0$, $p$, $\varphi$, $\Lambda$ and ${\Xi }^{-}$) from Au+Au collisions at $\sqrt{s_{NN}}$ = 3\,GeV and $v_2$ for (${\pi }^{\pm }$, $K^{\pm }$, $p$ and $\overline{p}$) at 27 and 54.4\,GeV with the STAR experiment. While at the two higher energy midcentral collisions the number-of-constituent-quark (NCQ) scaling holds, at 3\,GeV the $v_2$ at midrapidity is negative for all hadrons and the NCQ scaling is absent. In addition, the $v_1$ slopes at midrapidity for almost all observed hadrons are found to be positive, implying dominant repulsive baryonic interactions. The features of negative $v_2$ and positive $v_1$ slope at 3\,GeV can be reproduced with a baryonic mean-field in transport model calculations. These results imply that the medium in such collisions is likely characterized by baryonic interactions.

   nucl-exhep-exPLB(2022)·136 citations
6. 06*

   Probing Strangeness Canonical Ensemble with $K^{-}$, $\varphi (1020)$ and ${\Xi }^{-}$ Production in Au+Au Collisions at $\sqrt{s_{\mathrm{NN}}}=3\mathrm{GeV}$

   STAR Collaboration: M. S. Abdallah · B. E. Aboona · J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · I. Aggarwal · M. M. Aggarwal · Z. Ahammed · I. Alekseev · D. M. Anderson and 386 other authors

   We report the first multi-differential measurements of strange hadrons of $K^{-}$, $\varphi$ and ${\Xi }^{-}$ yields as well as the ratios of $\varphi /K^{-}$ and $\varphi /{\Xi }^{-}$ in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=3\mathrm{GeV}$ with the STAR experiment fixed target configuration at RHIC. The $\varphi$ mesons and ${\Xi }^{-}$ hyperons are measured through hadronic decay channels, $\varphi \to K^{+}{K}^{-}$ and ${\Xi }^{-}\to \Lambda {\pi }^{-}$. Collision centrality and rapidity dependence of the transverse momentum spectra for these strange hadrons are presented. The $4\pi$ yields and ratios are compared to thermal model and hadronic transport model predictions. At this collision energy, thermal model with grand canonical ensemble (GCE) under-predicts the $\varphi /K^{-}$ and $\varphi /{\Xi }^{-}$ ratios while the result of canonical ensemble (CE) calculations reproduce $\varphi /K^{-}$, with the correlation length $r_c\sim 2.7$\,fm, and $\varphi /{\Xi }^{-}$, $r_c\sim 4.2$\,fm, for the 0-10\% central collisions. Hadronic transport models including high mass resonance decays could also describe the ratios. While thermal calculations with GCE work well for strangeness production in high energy collisions, the change to CE at $3\mathrm{GeV}$ implies a rather different medium property at high baryon density.

   nucl-exhep-exPLB(2022)·48 citations
7. 07*

   Odd-even staggering and shell effects of charge radii for nuclei with even $Z$ from $36$ to $38$ and from $52$ to $62$

   Rong An · Xiang Jiang · Li-Gang Cao · Feng-Shou Zhang🇨🇳

   A unified theoretical model reproducing charge radii of known atomic nuclei plays an essential role in making extrapolations for unknown nuclei. Recently developed new ansatz which phenomenologically takes into account the neutron-proton short-range correlations ($np$-SRCs) can describe the discontinuity properties and odd-even staggering (OES) effect of charge radii along isotopic chains remarkably well. In this work, we further review the modified root-mean-square (rms) charge radii formula in the framework of relativistic mean field (RMF) theory. The charge radii are calculated along various isotopic chains that include the nuclei featuring the $N=50$ and $82$ magic shells. Our results suggest that RMF with and without considering a correction term give an almost similar trend of nuclear size for some isotopic chains with open proton shell, especially the abrupt increases across the strong neutron closed shells and the OES behaviors. This reflects that the $np$-SRCs have almost no influence for some nuclei due to the strong coupling between different levels around Fermi surface. The weakening OES behavior of nuclear charge radii is observed generally at completely filled neutron shells and this may be proposed as a signature of magic indicator.

   ↳ nucl-thnucl-exPRC(2022)·24 citations
8. 08*

   Unfolding the effects of final-state interactions and quantum statistics in two-particle angular correlations

   Łukasz Kamil Graczykowski🇵🇱 · Małgorzata Anna Janik🇵🇱

   Angular correlations of identified particles measured in ultrarelativistic proton-proton (pp) and heavy-ion collisions exhibit a number of features which depend on the collision system and particle type under consideration. Those features are produced by mechanisms, such as (mini)jets, elliptic flow, resonance decays, and conservation laws. In addition, of particular importance are those related to the quantum statistics (QS) and final-state interactions (FSIs). In this paper we show how to unfold the QS and FSI contributions in angular correlation functions by employing a Monte Carlo approach and using momentum correlations (femtoscopy), focusing on pp reactions. We validate the proposed method with PYTHIA 8 Monte Carlo simulations of pp collisions at $\sqrt{s}=13$ TeV coupled to calculations of QS and FSI effects with the Lednický and Lyuboshitz formalism and provide predictions for the unfolded effects. In particular, we show how those effects modify the shape of the angular correlation function with emphasis on pions and protons. Most importantly, specific structures observed in the near-side region for both baryon-baryon and baryon-antibaryon pairs, originating from the strong interaction, are unveiled with the proposed method.

   ↳ nucl-thnucl-exPRC(2021)·13 citations
9. 09*

   Recent results on Central Exclusive Production with the STAR detector

   Rafal Sikora (for the STAR Collaboration)🇵🇱

   We present results on the Central Exclusive Production of charged particle pairs $h^{+}{h}^{-}$ ($h=\pi ,K,p$), $pp\to p^{\prime }+h^{+}{h}^{-}+p^{\prime }$, obtained with the STAR experiment at RHIC in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=200$ GeV. All final-state particles were reconstructed, including forward-scattered protons detected in the Roman Pot system. As a result, the Double Pomeron Exchange (DPE) events were selected and the non-exclusive backgrounds were efficiently rejected. Differential fiducial cross sections were measured as functions of observables related to the central hadronic final state and to the forward-scattered protons. The measured cross sections were compared to phenomenological model predictions based on the DPE. We also present preliminary results on the measurement of the same physics process at higher collision energy $\sqrt{s}=510$ GeV. The data demonstrate features similar to those observed at $\sqrt{s}=200$ GeV.

   ↳ hep-exnucl-exSciPost Phys.Proc.(2022)·0 citations
10. 10*

    Measurements of $W$ and $Z/{\gamma }^{\ast }$ cross sections and their ratios in $pp$ collisions at STAR

    Jae Nam (for the STAR collaboration)🇺🇸

    While the unpolarized parton distribution functions of the valence quarks ($d$ and $u$) are well determined from DIS experiments, the sea quark counterparts, $\bar{d}$ and $\bar{u}$, are much less constrained, in particular, near the valence region. Measurements of $W^{+}/W^{-}$ production ratio in $pp$ collider experiments, such as the STAR experiment at RHIC, can probe the $\bar{d}/\bar{u}$ ratio at a large $Q^2$ set by the $W$ mass. These proceedings will discuss recent results of $W$ and $Z$ cross-section measurements using the STAR $pp$ collision data at a center-of-mass energy of $\sqrt{s}=500/510\mathrm{GeV}$ collected in 2011, 2012, 2013 and 2017.

    ↳ hep-exnucl-exSciPost Phys.Proc.(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.