Thu·May 18, 2023Thursday·May 18, 2023

1. 01*

   $\Delta$-baryon axialvector and pseudoscalar form factors, and associated PCAC relations

   Pei-Lin Yin🇨🇳 · Chen Chen🇨🇳 · Christian S. Fischer🇩🇪 · Craig D. Roberts🇨🇳

   A quark+diquark Faddeev equation treatment of the baryon bound state problem in Poincaré-invariant quantum field theory is used to deliver parameter-free predictions for all six $\Delta$-baryon elastic weak form factors. Amongst the results, it is worth highlighting that there are two distinct classes of such $\Delta$-baryon form factors, $(g_1,g_3,G_{\pi \Delta \Delta })$, $(h_1,h_3,H_{\pi \Delta \Delta })$, the functions within each of which are separately linked via partial conservation of axial current (PCAC) and Goldberger-Treiman (GT) relations. Respectively within each class, the listed form factors possess qualitatively the same structural features as the nucleon axial, induced pseudoscalar, and pion-nucleon coupling form factors. For instance, the $\Delta$-baryon $g_1$ axial form factor can reliably be approximated by a dipole function, characterised by an axial charge $g_A^{{\Delta }^{+}}=0.71(9)$ and mass-scale $m_A^{\Delta }=0.95(2)m_{\Delta }$. Moreover, the two distinct $\Delta$-baryon PCAC form factor relations are satisfied to a high degree of accuracy on a large range of $Q^2$; the associated GT relations present good approximations only on $Q^2/m_{\Delta }^2\simeq 0$; and pion pole dominance approximations are reliable within both classes. There are two $\pi \Delta \Delta$ couplings: $g_{\pi \Delta \Delta }=10.46(1.88)$; $h_{\pi \Delta \Delta }=35.73(3.75)$; and the associated form factors are soft. Such couplings commonly arise in phenomenology, which may therefore benefit from our analyses. A flavour decomposition of the axial charges reveals that quarks carry $71$\% of the $\Delta$-baryon spin. The analogous result for the proton is $\approx 65$\%.

   ↳ hep-phhep-exhep-latnucl-ex+1EPJA(2023)·8 citations
2. 02*

   Machine learning study to identify collective flow in small and large colliding systems

   Shuang Guo🇨🇳 · Han-Sheng Wang🇨🇳 · Kai Zhou🇩🇪 · Guo-Liang Ma🇨🇳

   Collective flow has been found to be similar between small colliding systems ($p$ $+$ $p$ and $p$ $+$ A collisions) and large colliding systems (peripheral A $+$ A collisions) at the CERN Large Hadron Collider. In order to study the differences of collective flow between small and large colliding systems, we employ a point cloud network to identify $p$ $+$ Pb collisions and peripheral Pb $+$ Pb collisions at $\sqrt{s_{NN}}=$ 5.02 TeV generated from a multiphase transport model (AMPT). After removing the discrepancies in the pseudorapidity distribution and the $p_{\mathrm{T}}$ spectra, we capture the discrepancy in collective flow. Although the verification accuracy of our PCN is limited due to similar event-by-event distributions of elliptic and triangular flow, we demonstrate that collective flow between $p$ $+$ Pb collisions and peripheral Pb $+$ Pb collisions becomes more distinct with increasing final hadron multiplicity and parton scattering cross section. This study not only highlights the potential of PCN techniques in advancing the understanding of collective flow in varying colliding systems, but more importantly lays the groundwork for the future PCN-related research.

   ↳ nucl-thhep-phnucl-exPRC(2024)·10 citations
3. 03*

   Studies on the hadronization of charm and beauty quarks

   Mattia Faggin (on behalf of ALICE Collaboration)🇮🇹

   In this contribution, the latest results on hadronization studies of charm and beauty quarks obtained with the data collected with the ALICE experiment at the LHC are presented. Measurements of prompt and non-prompt charm-hadron production in pp, p-Pb and Pb-Pb are shown. The results are also compared with theoretical models that consider different implementations of the heavy-quark hadronization across collision systems.

   ↳ hep-exnucl-ex1 citation
4. 04*

   Measurement of transverse single-spin asymmetries for dijet production in polarized proton-proton collisions at $\sqrt{\mathbf{s}}$ = 200 $\mathrm{GeV}$

   STAR Collaboration

   We report a new measurement of transverse single-spin asymmetries for dijet production in collisions of polarized protons at $\sqrt{s}$ = 200 $\mathrm{GeV}$. Correlations between the proton spin and the transverse momenta of its partons, each perpendicular to the proton momentum direction, are probed at high $Q^2$ $\approx$160 ${\mathrm{GeV}}^2$. Evidence for nonzero Sivers effects is measured for the first time in dijets from proton-proton collisions, but only when the jets are sorted by their net charge, which enhances the otherwise canceling opposite-sign $u$- or $d$-quark contributions to separate data samples. The resulting asymmetries are compared to recent theoretical calculations. Separately, the associated Sivers observable $⟨k_T⟩$, the average parton transverse momentum, is extracted using a simple kinematics approach which further enables a determination of the individual partonic contributions to the observed asymmetries.

   ↳ hep-exnucl-exPRD(2026)·6 citations
5. 05*

   Baryon diffusion coefficient of the strongly interacting medium

   Tribhuban Parida🇮🇳 · Sandeep Chatterjee🇮🇳

   We propose that the transverse momentum ($p_T$) differential splitting of directed flow ($\Delta v_1$) between proton and anti-proton can serve as a sensitive observable to extract the baryon diffusion coefficient (${\kappa }_B$) of the hot and dense strongly interacting matter produced in relativistic heavy ion collisions. We use relativistic dissipative hydrodynamics framework with Glauber model based initial condition for the energy as well as baryon deposition that is calibrated to capture the rapidity dependence of charged particle multiplicity, net proton yield as well as the elusive $v_1$ splitting between proton and anti-proton. We employ the commonly used kinetic theory motivated ansatz: ${\kappa }_B=C_B\frac{n_B}{T}\left(\frac{1}{3}\text{coth}\left(\frac{{\mu }_B}{T}\right)-\frac{n_{B}T}{ϵ+P}\right)$ where $n_B$, $ϵ$, $P$, $T$ and ${\mu }_B$ are baryon number density, energy density, pressure, temperature and baryon chemical potential respectively while $C_B$ is an arbitrary constant which is largely unknown for the Quantum Chromodynamics (QCD) medium. We find that the variation of $\Delta v_1$ with $p_T$ is strongly influenced by the choice of $C_B$. Further, we find that the recent STAR measurement of the centrality dependence of the rapidity slope of $\Delta v_1$ prefers $0.5<C_B<1.5$.

   ↳ nucl-thhep-exhep-phnucl-ex8 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.