Mon·Nov 1, 2021Monday·November 1, 2021

1. 01*

   Measurements of sub-jet fragmentation with ALICE

   James Mulligan (for the ALICE Collaboration)🇺🇸

   High-energy jets offer rich opportunities to study quantum chromodynamics, from investigating the limits of perturbative calculability to constraining the emergent properties of the quark-gluon plasma (QGP). In these proceedings, we present new measurements of the fragmentation properties of jets. We report distributions of the sub-jet momentum fraction $z_r$ measured in pp and Pb-Pb collisions with ALICE at the Large Hadron Collider. These measurements serve as input to test the universality of jet fragmentation in the QGP, and offer a path to elucidate jet quenching effects in the large-$z$ region.

   nucl-exhep-exSciPost Phys.Proc.(2022)·1 citation
2. 02*

   Measurements of $\varphi$ meson and ${\Xi }^{-}$ hyperon production in Au+Au collisions at $\sqrt{s_{NN}}$ = 3 GeV from STAR experiment

   Yingjie Zhou (for the STAR Collaboration)🇨🇳

   In this proceedings, we present our first measurements of $\varphi$ meson and ${\Xi }^{-}$ hyperon production in Au+Au collisions at $\sqrt{s_{NN}}$ = 3 GeV. Various models including thermal and transport model calculations are compared to data, these results imply that the matter produced in the 3 GeV Au+Au collisions is considerably different from that at higher energies.

   nucl-exSciPost Phys.Proc.(2022)·1 citation
3. 03*

   Measurement of Compton scattering at MAMI for the extraction of the electric and magnetic polarizabilities of the proton

   A2 Collaboration: E. Mornacchi (1) · P.P. Martel (1 and 2) · S. Abt (3) · P. Achenbach (1) · P. Adlarson (1) · F. Afzal (4) · Z. Ahmed (5) · J.R.M. Annand (6) · H.J. Arends (1) · M. Bashkanov (7) · R. Beck (4) · M. Biroth (1) and 53 other authors

   A precise measurement of the differential cross-sections $d\sigma /d\Omega$ and the linearly polarized photon beam asymmetry ${\Sigma }_3$ for Compton scattering on the proton below pion threshold has been performed with a tagged photon beam and almost $4\pi$ detector at the Mainz Microtron. The incident photons were produced by the recently upgraded Glasgow-Mainz photon tagging facility and impinged on a cryogenic liquid hydrogen target, with the scattered photons detected in the Crystal Ball/TAPS set-up. Using the highest statistics Compton scattering data ever measured on the proton along with two effective field theories (both covariant baryon and heavy-baryon) and one fixed-$t$ dispersion relation model, constraining the fits with the Baldin sum rule, we have obtained the proton electric and magnetic polarizabilities with unprecedented precision: \begin{align*} &{}\alpha_{E1} = 10.99 \pm 0.16 \pm 0.47 \pm 0.17 \pm 0.34 &{}\beta_{M1} = 3.14 \pm 0.21 \pm 0.24 \pm 0.20 \pm 0.35 \end{align*} in units of $10^{-4}$\,fm${}^3$ where the errors are statistical, systematic, spin polarizability dependent and model dependent.

   nucl-exnucl-thPRL(2022)·22 citations
4. 04*

   Exploring jet fragmentation using two-particle correlations with $\Lambda$ and K${}_{\mathrm{S}}^0$

   Lucia Anna Tarasovičová (for the ALICE Collaboration)🇩🇪

   Complementary to jet reconstruction, two-particle correlations in $\Delta \eta$ and $\Delta \phi$ are used to study jets, in particular their particle composition. While in Pb--Pb collisions this is done to characterize the quark--gluon plasma, pp and p--Pb collisions serve as a reference and are of interest on their own for their input into the understanding of particle production mechanisms. Recent ALICE results on the production of strange particles in small systems (pp and p--Pb collisions) reveal the possibility of having similar strange hadron production mechanisms in all collision systems. We present here a study of two-particle correlations triggered with strange hadrons (${\mathrm{K}}_{\mathrm{S}}^0$, $\Lambda$, $\overline{\Lambda }$) in pp collisions at 13 TeV and 5.02 TeV and in the most central Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$= 5.02 TeV. The dependence of the per-trigger yields of primary charged hadrons on the transverse momenta of the trigger and associated particles, as well as on the event multiplicity, will be presented for both the near-side and away-side regions. Moreover, the ratios of these yields to the yields extracted from inclusive hadron-hadron correlations and the nuclear modification factor $I_{AA}$ will be discussed. The results are compared among the three hadron species. In addition, a comparison to different Monte Carlo generators is presented, which allows us to better understand strangeness production in jets.

   nucl-exhep-exPoS(2022)·0 citations
5. 05*

   Measurement of the jet-particle $v_2$ in p--Pb and Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV with ALICE at the LHC

   Siyu Tang (for the ALICE Collaboration)🇨🇳

   The elliptic flow of jet particles at midrapidity ($|\eta |$ < 0.8) is measured for the first time in p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV and extended down to lower $p_{\mathrm{T}}$ in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV. The jet particles are extracted with the two-particle correlation method using a two-dimensional fit, and their $v_2$ is calculated with the novel three-particle correlation technique. The $v_2$ of jet particles is found positive in high-multiplicity p--Pb collisions and exhibits no dependence on $p_{\mathrm{T}}$ within uncertainties. Comparisons with the jet-particle $v_2$ in Pb--Pb collisions and the inclusive charged-particle $v_2$ in both collision systems are also discussed, aiming to bring new insights into the understanding of the origin of the high-$p_{\mathrm{T}}$ azimuthal anisotropy observed in small collision systems.

   nucl-exhep-exPoS(2022)·1 citation
6. 06*

   CME search at STAR

   Yu Hu (for the STAR Collaboration)🇨🇳

   The hot and dense medium produced in relativistic heavy-ion collisions has been conjectured to be accompanied by an axial charge asymmetry that may lead to a separation of electric charges in the direction of the extremely strong magnetic field, also known as the Chiral Magnetic Effect (CME). The measurement of azimuthal correlator ($\Delta \gamma$) with respect to the spectator plane, gives us an opportunity to measure the possible CME fraction beyond the flow background. Preliminary results using this approach with combined Au+Au collisions at $\sqrt{s_{NN}}=$ 200 GeV and U+U at $\sqrt{s_{NN}}=$ 193 GeV show $f_{CME}$ at $(8\pm 4\pm 8)$ $\%$. Meanwhile, the observability of CME has been conjectured to be dependent on $\sqrt{s_{NN}}$ due to changes in the lifetime of the magnetic field, the strengths of CME signal and non-CME background. At lower energies, the Event Plane Detector (EPD) installed in the year 2018 provides a unique capability for CME search. The background scenario test at Au+Au $\sqrt{s_{NN}}=$ 27 GeV by using $\Delta \gamma$ with respect to TPC and the new installed EPD shows a consistency with no-CME scenario in the current statistics. The method of the ongoing isobar blind analysis, and the latest sensitivity check with the event-by-event AVFD model on the different observables between Ru+Ru and Zr+Zr are also briefly discussed.

   nucl-exhep-phnucl-thEPJ Web Conf.(2022)·5 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.