Thu·Jul 28, 2022Thursday·July 28, 2022

1. 01*

   Charmonium production as a function of charged-particle multiplicity in pp and p--Pb collisions with ALICE at the LHC

   Theraa Tork (for the ALICE collaboration)🇫🇷

   Heavy quarkonium production is an excellent tool to test both perturbative and non-perturbative QCD, as perturbative QCD can describe the heavy quark production process, while the formation of the quarkonium bound state involves non-perturbative aspects. In ultrarelativistic heavy-ion collisions, a deconfined state of QCD matter, made of free quarks and gluons, called quark-gluon plasma (QGP) is expected to be formed. To probe such an environment, the study of quarkonium production is an important tool as the heavy quarks are produced during the initial stage of the collision and experience the entire medium evolution. Surprisingly, in small colliding systems as pp and p--Pb, QGP-like behaviours are observed when selecting high multiplicity events. The physics interpretation of these behaviours remains unclear. However, multiparton interaction is one of the main promising scenarios to explain such observation. Studies of charmonium yields as a function of the event charged-particle pseudorapidity density in pp and p--Pb collision allow one to probe multiple parton interactions in an indirect way. These proceedings present the measurements of quarkonium yields normalised to their average values as a function of the charged-particle multiplicity in pp collisions at $\sqrt{s}$ = 13 TeV and in p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 8.16 TeV, performed by the ALICE experiment at the LHC. The corresponding results for the $\psi (2S)$-to-J/$\psi$ ratios as a function of charged-particle multiplicity are also shown. In addition, J/$\psi$ pair production measurement in pp collisions at $\sqrt{s}$ = 13 TeV is discussed.

   nucl-exhep-ex0 citations
2. 02*

   An enhancement of formation of unstable ${}^8$Be nucleus with the growth of $\alpha$-particle multiplicity in fragmentation of relativistic nuclei

   A.A. Zaitsev🇷🇺 · P.I. Zarubin · N.G. Peresadko

   In this paper, the correlation between the formation of the unstable ${}^8$Be nucleus and accompanying $\alpha$ particles in the fragmentation of relativistic ${}^{16}$O, ${}^{22}$Ne, ${}^{28}$Si, and ${}^{197}$Au nuclei in a nuclear track emulsion is investigated. The ${}^8$Be decays are identified in a wide energy range by invariant masses calculated from 2$\alpha$-pair opening angles. The adopted approximations are verified by data on fragmentation of ${}^{16}$O nuclei in a hydrogen bubble chamber in a magnetic field. An increase in the ${}^8$Be contribution to the dissociation with the growth of $\alpha$-particle multiplicity is found.

   nucl-exPhys.Atom.Nucl.(2021)·3 citations
3. 03*

   Resonant behavior of the $pp\to \{pp{\}}_s{\pi }^0$ reaction at the energy $\sqrt{s}$ = 2.65 GeV

   Dmitry Tsirkov · Bota Baimurzinova · Vladimir I. Komarov · Anatoly V. Kulikov · Ainur Kunsafina · Vladimir S. Kurbatov · Zhanibek Kurmanalyiev · Yury N. Uzikov

   We report on measurements of the differential cross section $d\sigma /d\Omega$ in the energy region of $\sqrt{s}$ = 2.5-2.9 GeV of the reaction $pp\to \{pp{\}}_s{\pi }^0$ where $\{pp{\}}_s$ is a ${}^1{S}_0$ proton pair. The experiment has been performed with the ANKE spectrometer at COSY-Jülich. The data reveal a peak in the energy dependence of the forward $\{pp{\}}_s$ differential cross section at the energy $\sqrt{s}$ = 2.65 GeV with the width $\Gamma$ = 0.26 GeV, and also the cross section slope changes its sign in the region of the observed peak. This is an indication for the excitation of a new $D(2650)$ resonant state, that may be a dibaryon resonance system consisting of two excited baryons $\Delta (1232)$ and $N^{\ast }(1440)$.

   nucl-exPRC(2023)·3 citations
4. 04*

   Bayesian Inference of the Specific Shear and Bulk Viscosities of the Quark-Gluon Plasma at Crossover from $\varphi$ and $\Omega$ Observables

   Zhidong Yang🇨🇳 · Lie-Wen Chen🇨🇳

   Due to their weak final state interactions, the $\varphi$ meson and $\Omega$ baryon provide unique probes of the properties of the quark-gluon plasma (QGP) formed in relativistic heavy-ion collisions. Using the quark recombination model with the quark phase-space information parameterized in a viscous blastwave, we study the transverse-momentum spectra and elliptic flows of $\varphi$ and $\Omega$ in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV and Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV. The viscous blastwave includes non-equilibrium deformations of thermal distributions due to shear and bulk stresses and thus carries information on the specific shear viscosity $\eta /s$ and the specific bulk viscosity $\zeta /s$ of the QGP. We perform a model-to-data comparison with Bayesian inference and simultaneously obtain $\eta /s=(2.08_{-1.09}^{+1.10})/4\pi$ and $\zeta /s=0.06_{-0.04}^{+0.04}$ at $90\%$ C.L. for the baryon-free QGP at crossover temperature of about $160$ MeV. Our work provides a novel approach to simultaneously determine the $\eta /s$ and $\zeta /s$ of the QGP at hadronization.

   ↳ nucl-thhep-phnucl-exPRC(2023)·16 citations
5. 05*

   Mass spectrometric investigations into 3D printed parts to assess radiopurity as ultralow background materials for rare event physics detectors

   Amanda D. French🇺🇸 · Sonia Alcantar Anguiano🇺🇸 · Mary Bliss🇺🇸 · Josef Christ🇺🇸 · Maria Laura di Vacri🇺🇸 · Rebecca Erikson🇺🇸 · Khadouja Harouaka🇺🇸 · Eric W. Hoppe🇺🇸 · Jay W. Grate🇺🇸 · Isaac J. Arnquist🇺🇸

   New data are reported for polyvinylidene fluoride (PVDF), polyphenylene sulfide (PPS), and two forms of polyetherimide (PEI, branded ULTEM 1010 and 9085). Data for starting filaments and both simple and complex printed parts are reported. PVDF filaments and simple printed beads, were found to have values of approximately 30 and 50 ppt for Th-232 and U-238, respectively, while a more complex spring clip part had slightly elevated Th-232 levels of 65 ppt, with U-238 remaining at 50 ppt. PPS filament was found to have concentrations of 270 and 710 ppt for Th-232 and U-238, respectively, and were not chosen to be printed as those levels were already higher than other material options. ULTEM 1010 filaments and printed complex spring clip parts were found to have concentrations of around 5 and 7 ppt for Th-232 and U-238, respectively, illustrating no significant contamination from the printing process. ULTEM 9085 filaments were found to have concentrations of around 9 and 5 ppt for Th-232 and U-238, respectively, while the printed complex spring clip part was found to have slightly elevated concentrations of 25 and 7 ppt for Th-232 and U-238, respectively. These results were all obtained using a novel dry ashing method in crucibles constructed of ultralow background electroformed copper or, when applicable, microwave-assisted wet ashing digestion. Samples and process blanks were spiked with Th-229 and U-233 as internal standards prior to dry/wet ashing and determinations were made by inductively coupled plasma mass spectrometry (ICP-MS). In order to maintain high radiopurity levels, pre-cleaning the filaments before printing and post-cleaning the parts is recommended, although the printing process itself has shown to contribute very minute amounts of radiocontaminants.

   ↳ physics.ins-dethep-exnucl-exNucl.Instrum.Meth.A(2023)·0 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.