Wed·Apr 6, 2022Wednesday·April 6, 2022

1. 01*

   Parton energy loss at LHC tests for a strongly coupled medium

   Sourendu Gupta🇮🇳 · Rishi Sharma🇮🇳

   We construct a measure of transverse momentum loss of jets in nuclear collisions at LHC directly using measurements of jet cross sections in PbPb and pp collisions. The proposal is shown to be equivalent to R_AA and is equally straightforward to construct. Using data from the ATLAS collaboration at two different collision energies, we show that the proposed measure has small statistical uncertainties. We argue that systematic errors can be easily improved over our estimates by the experimental collaboration to such an extent that it directly probes whether the jet-medium interaction is due to a strongly interacting medium or a weakly interacting plasma. We argue that the current data may marginally favour a strongly interacting medium. On the other hand, assuming that the medium is weakly interacting, we are able to provide estimates of the jet quenching parameter qhat which are in rough agreement with previously reported estimates.

   ↳ hep-phhep-exnucl-exnucl-th0 citations
2. 02*

   Octupole correlations in collective excitations of neutron-rich $N\approx 56$ nuclei

   Kosuke Nomura🇭🇷

   Octupole correlations in the low-energy collective states of neutron-rich nuclei with the neutron number $N\approx 56$ are studied within the interacting boson model (IBM) that is based on the nuclear density functional theory. The constrained self-consistent mean-field (SCMF) calculations using a universal energy density functional and a pairing interaction provide the potential energy surfaces in terms of the axially-symmetric quadrupole and octupole deformations for the even-even nuclei ${}^{86-94}$Se, ${}^{88-96}$Kr, ${}^{90-98}$Sr, ${}^{92-100}$Zr, and ${}^{94-102}$Mo. The SCMF energy surface is then mapped onto the energy expectation value of a version of the IBM in the boson condensate state, which consists of the neutron and proton monopole $s$, quadrupole $d$, and octupole $f$ bosons. This procedure determines the strength parameters of the IBM Hamiltonian, which is used to compute relevant spectroscopic properties. At the SCMF level, no octupole deformed ground state is obtained, while the energy surface is generally soft in the octupole deformation at $N\approx 56$. The predicted negative-parity yrast bands with the bandhead state $3_1^{-}$ weakly depend on $N$ and become lowest in energy at $N=56$ in each of the considered isotopic chains. The model further predicts finite electric octupole transition rates between the lowest negative- and the positive-parity ground-state bands.

   ↳ nucl-thnucl-exPRC(2022)·16 citations
3. 03*

   Local and global polarization of $\Lambda$ hyperons across RHIC-BES energies: the roles of spin hall effect, initial condition and baryon diffusion

   Xiang-Yu Wu🇨🇳 · Cong Yi🇨🇳 · Guang-You Qin🇨🇳 · Shi Pu🇨🇳

   We perform a systematic study on the local and global spin polarization of $\Lambda$ and $\overline{\Lambda }$ hyperons in relativistic heavy-ion collisions at beam energy scan energies via the (3+1)-dimensional CLVisc hydrodynamics model with AMPT and SMASH initial conditions. Following the quantum kinetic theory, we decompose the polarization vector as the parts induced by thermal vorticity, shear tensor and the spin Hall effect (SHE). We find that the polarization induced by SHE and the total polarization strongly depends on the initial conditions. At $7.7$GeV, SHE gives a sizeable contribution and even flips the sign of the local polarization along the beam direction for AMPT initial condition, which is not observed for SMASH initial condition. Meanwhile, the local polarization along the out-of-plane direction induced by SHE with AMPT initial condition does not always increase with decreasing collision energies. Next, we find that the polarization along the beam direction is sensitive to the baryon diffusion coefficient, but the local polarization along the out-of-plane direction is not. Our results for the global polarization of $\Lambda$ and $\overline{\Lambda }$ agree well with the STAR data. Interestingly, the global polarization of $\overline{\Lambda }$ is not always larger than that of $\Lambda$ due to various competing effects. Our findings are helpful for understanding the polarization phenomenon and the detailed structure of quark-gluon plasma in relativistic heavy-ion collisions.

   ↳ hep-phnucl-exnucl-thPRC(2022)·78 citations
4. 04*

   Constraints from $\Lambda$ hypernuclei on the $\Lambda NN$ content of the $\Lambda$-nucleus potential

   E. Friedman🇮🇱 · A. Gal🇮🇱

   A depth of $D_{\Lambda }\approx -28$ MeV for the $\Lambda$-nucleus potential was confirmed in 1988 by studying $\Lambda$ binding energies deduced from $({\pi }^{+},K^{+})$ spectra measured across the periodic table. Modern two-body hyperon-nucleon interaction models require additional interaction terms, most likely $\Lambda NN$ three-body terms, to reproduce $D_{\Lambda }$. In this work we apply a suitably constructed $\Lambda$-nucleus density dependent optical potential to binding energy calculations of observed $1s_{\Lambda }$ and $1p_{\Lambda }$ states in the mass range $12\le A\le 208$. The resulting $\Lambda NN$ contribution to $D_{\Lambda }$, about 14 MeV repulsion at symmetric nuclear matter density ${\rho }_0=0.17$ fm${}^{-3}$, makes $D_{\Lambda }$ increasingly repulsive at $\rho \gtrsim 3{\rho }_0$, leading possibly to little or no $\Lambda$ hyperon content of neutron-star matter. This suggests in some models a stiff equation of state that may support two solar-mass neutron stars.

   ↳ nucl-thhep-phnucl-exPLB(2023)·38 citations
5. 05*

   Pattern of Global Spin Alignment of $\varphi$ and $K^{\ast 0}$ mesons in Heavy-Ion Collisions

   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 · A. Aitbaev · I. Alekseev and 380 other authors

   Notwithstanding decades of progress since Yukawa first developed a description of the force between nucleons in terms of meson exchange, a full understanding of the strong interaction remains a major challenge in modern science. One remaining difficulty arises from the non-perturbative nature of the strong force, which leads to the phenomenon of quark confinement at distances on the order of the size of the proton. Here we show that in relativistic heavy-ion collisions, where quarks and gluons are set free over an extended volume, two species of produced vector (spin-1) mesons, namely $\varphi$ and $K^{\ast 0}$, emerge with a surprising pattern of global spin alignment. In particular, the global spin alignment for $\varphi$ is unexpectedly large, while that for $K^{\ast 0}$ is consistent with zero. The observed spin-alignment pattern and magnitude for the $\varphi$ cannot be explained by conventional mechanisms, while a model with a connection to strong force fields, i.e. an effective proxy description within the Standard Model and Quantum Chromodynamics, accommodates the current data. This connection, if fully established, will open a potential new avenue for studying the behaviour of strong force fields.

   ↳ hep-phnucl-exNature(2023)·230 citations
6. 06*

   Splitting of elliptic flow in a tilted fireball

   Tribhuban Parida🇮🇳 · Sandeep Chatterjee🇮🇳

   The splitting of elliptic flow measured in different regions of the momentum space of produced hadrons has been recently studied in transport models and proposed as a sensitive probe of the angular momentum carried by the fireball produced in a relativistic heavy ion collision. The initial state angular momentum also gives rise to rapidity odd directed flow which has been measured. We consider a relativistic hydrodynamic framework with the initial matter distribution suitably calibrated to describe the observed directed flow and apply it to study the spilt in the elliptic flow. Our study suggests that the split in the elliptic flow is mostly driven by directed and triangular flows and may be used to constrain models of initial state rapidity distribution of matter in the fireball.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2022)·11 citations
7. 07*

   Probing the nuclear deformation with three-particle asymmetric cumulant in RHIC isobar runs

   Shujun Zhao🇨🇳 · Hao-jie Xu🇨🇳 · Yu-Xin Liu🇨🇳 · Huichao Song🇨🇳

   ${}_{44}^{96}$Ru+${}_{44}^{96}$Ru and ${}_{40}^{96}$Zr+${}_{40}^{96}$Zr collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV provide unique opportunities to study the geometry and fluctuations raised from the deformation of the colliding nuclei. Using iEBE-VISHNU hybrid model, we predict ${\mathrm{ac}}_2\{3\}$ ratios between these two collision systems and demonstrate that the ratios of ${\mathrm{ac}}_2\{3\}$, as well as the ratios of the involving flow harmonics and event-plane correlations, are sensitive to quadrupole and octupole deformations, which could provide strong constrains on the shape differences between ${}^{96}$Ru and ${}^{96}$Zr. We also study the nonlinear response coefficients ${\chi }_{4,22}$, which show insensitivity to the deformation effect.

   ↳ nucl-thnucl-exPLB(2023)·35 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.