Tue·Dec 28, 2021Tuesday·December 28, 2021

1. 01*

   Studying the mechanisms for strange particle production with ALICE at LHC

   Meenakshi Sharma (for the ALICE Collaboration)🇮🇳

   The main goal of the ALICE experiment is to study the physics of strongly interacting matter, focusing on the properties of the quark-gluon plasma (QGP). The relative production of strange hadrons with respect to non-strange hadrons in heavy-ion collisions was historically considered as one of the signatures of QGP formation. However, the latest results in proton-proton (pp) and proton-lead (p-Pb) collisions have revealed an increasing trend in the yield ratio of strange hadrons to pions with the charged-particle multiplicity in the event, showing a smooth evolution across different collision systems and energies. We present the new studies which are performed with the aim of better understanding the production mechanisms for strange particles and hence the strangeness enhancement phenomenon in small collision systems. In one of the recent studies, the very forward energy transported by beam remnants (spectators) and detected by the Zero Degree Calorimeters (ZDC) is used to classify events. The contribution of the effective energy and the particle multiplicity on strangeness production is studied using a multi-differential approach in order to disentangle initial and final state effects. In the second study, the origin of strangeness enhancement with multiplicity in pp has been further investigated by separating the contribution of soft and hard processes, such as jets, to strange hadron production. Techniques involving full jet reconstruction or two-particle correlations have been exploited. The results indicate that the increased relative strangeness production emerges from the growth of the underlying event, being disconnected from initial state properties, and suggest that soft (out-of-jets) processes are the dominant contribution to strange hadron production.

   nucl-exhep-exRev.Mex.Fis.Suppl.(2022)·1 citation
2. 02*

   Effects of variation of the fine structure constant $\alpha$ and quark mass $m_q$ in Mössbauer nuclear transitions

   Pavel Fadeev🇩🇪 · Julian C. Berengut🇦🇺 · Victor V. Flambaum🇦🇺

   High accuracy measurements in Mössbauer transitions open up the possibility to use them in the search for temporal and spatial variation of the fine-structure constant $\alpha$, quark mass $m_q$, and dark matter field which may lead to the variation of $\alpha$ and $m_q$. We calculate the sensitivity of nuclear transitions to variation of $\alpha$ and $m_q$. Mössbauer transitions have high sensitivity to variation of quark mass $m_q$ and the strong interaction scale ${\Lambda }_{QCD}$, to which atomic optical clocks are not sensitive. The enhancement factors $K$, defined by $\frac{\delta f}{f}=K_{\alpha }\frac{\delta \alpha }{\alpha }$ and $\frac{\delta f}{f}=K_q\frac{\delta m_q}{m_q}$ where $f$ is the transition energy, may be large in some transitions. The 8~eV nuclear clock transition in ${}^{229}$Th ($K_q\approx 10^4$) and 76~eV transition in ${}^{235}$U ($K_{\alpha }\approx K_q\approx 10^3$) may be investigated using laser spectroscopy methods.

   ↳ nucl-thhep-phnucl-exphysics.atom-phPRC(2022)·11 citations
3. 03*

   Analysis of identified particle transverse momentum spectra produced in pp, p--Pb and Pb--Pb collisions at the LHC using Tsallis--Pareto-type function

   Pei-Pin Yang🇨🇳 · Mai-Ying Duan🇨🇳 · Fu-Hu Liu🇨🇳 · Raghunath Sahoo🇮🇳

   In the framework of a multi-source thermal model at the partonic-level, we have analyzed transverse momentum spectra of hadrons measured by the ALICE Collaboration in proton-proton ($pp$ or $p$-$p$) collisions at the center-of-mass energy of $\sqrt{s}=7$ and 13 TeV, proton-lead ($p$-Pb) collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV, and lead-lead (Pb-Pb) collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV. For meson(baryon), the contributions of two(three) constituent quarks are considered, in which each quark contributes to hadron transverse momentum to obey the revised phenomenological Tsallis transverse momentum distribution for the Maxwell-Boltzmann particles (the TP-like function in short) with isotropic random azimuthal angle. Three main parameters, namely, the revised index $a_0$, effective temperature $T$, and entropy-related index $n$ are obtained, which show the same tendency for small and large systems with respect to the centrality (or multiplicity) of events, rest mass of hadrons, and constituent mass of quarks.

   ↳ hep-phhep-exnucl-exnucl-thSymmetry(2022)·13 citations
4. 04*

   Effects of the momentum dependence of nuclear symmetry potential on pion observables in Sn + Sn collisions at 270 MeV/nucleon

   Gao-Feng Wei🇨🇳 · Xin Huang · Qi-Jun Zhi🇨🇳 · Ai-Jun Dong · Chang-Gen Peng · Zheng-Wen Long🇨🇳

   Within a transport model, we study effects of the momentum dependence of nuclear symmetry potential on pion observables in central Sn + Sn collisions at 270 MeV/nucleon. To this end, a quantity $U_{sym}^{\infty }({\rho }_0)$, i.e., the value of nuclear symmetry potential at the saturation density ${\rho }_0$ and infinitely large nucleon momentum, is used to characterise the momentum dependence of nuclear symmetry potential. It is shown that with a certain $L$ (i.e., slope of nuclear symmetry energy at ${\rho }_0$) the characteristic parameter $U_{sym}^{\infty }({\rho }_0)$ of symmetry potential affects significantly the production of ${\pi }^{-}$ and ${\pi }^{+}$ as well as their pion ratios. Moreover, through comparing the charged pion yields, pion ratios as well the spectral pion ratios of theoretical simulations for the reactions ${}^{108}$Sn + ${}^{112}$Sn and ${}^{132}$Sn + ${}^{124}$Sn with the corresponding data in S$\pi$RIT experiments, we find that our results favor a constraint on $U_{sym}^{\infty }({\rho }_0)$, i.e., $-160_{-9}^{+18}$~MeV, and the $L$ is also suggested within a range, i.e., $62.7<L<93.1$~MeV. In addition, it is shown that the pion observable of ${}^{197}$Au + ${}^{197}$Au collisions at 400~MeV/nucleon also supports the extracted value for $U_{sym}^{\infty }({\rho }_0)$.

   ↳ nucl-thnucl-exNucl.Sci.Tech.(2022)·11 citations
5. 05*

   Inferring nuclear structure from heavy isobar collisions using Trajectum

   Govert Nijs🇺🇸 · Wilke van der Schee🇨🇭

   Nuclei with equal number of baryons but varying proton number (isobars) have many commonalities, but differ in both electric charge and nuclear structure. Relativistic collisions of such isobars provide unique opportunities to study the variation of the magnetic field, provided the nuclear structure is well understood. In this Letter we simulate collisions using several state-of-the-art parametrizations of the ${}_{40}^{96}$Zr and ${}_{44}^{96}$Ru isobars and show that a comparison with the exciting STAR measurement arXiv:2109.00131 of ultrarelativistic collisions can uniquely identify the structure of both isobars. This not only provides an urgently needed understanding of the structure of the Zirconium and Ruthenium isobars, but also paves the way for more detailed studies of nuclear structure using relativistic heavy ion collisions.

   ↳ nucl-thhep-phnucl-exSciPost Phys.(2023)·58 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.