Wed·Nov 28, 2018Wednesday·November 28, 2018

1. 01*

   Quarkonium production in Pb--Pb and Xe--Xe collisions with ALICE at the LHC

   Markus K. Koehler (on behalf of the ALICE Collaboration)🇩🇪

   Quarkonium production is an excellent probe to investigate the properties of the hot and dense medium, which can be created in heavy-ion collisions. The production and hadronisation of heavy quarks are well separated in the space-time evolution of a collision and provide a wealth of information of the underlying QCD dynamics from the dense to the eventually dilute system. We report on the latest results from ALICE at the LHC on quarkonium production in heavy-ion collisions at mid- and forward rapidity. The nuclear modification factor as a function of centrality, transverse momentum, and rapidity is presented for charmonium and bottomonium states in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$~TeV. In addition, results on the nuclear modification factor of J/$\psi$ in Xe--Xe collisions at $\sqrt{s_{\mathrm{NN}}}=5.44$~TeV are presented. Experimental results are compared with available phenomenological calculations.

   nucl-exPoS(2018)·2 citations
2. 02*

   Hadron yields and fluctuations at the CERN Super Proton Synchrotron: system size dependence from Pb+Pb to p+p collisions

   A. Motornenko🇩🇪 · V.V. Begun🇵🇱 · V. Vovchenko🇩🇪 · M.I. Gorenstein🇺🇦 · H. Stoecker🇩🇪

   The kaon to pion ratio $K^{+}/{\pi }^{+}$ and the scaled variance ${\omega }^{-}$ for fluctuations of negatively charged particles are studied within the statistical hadron resonance gas (HRG) model and the Ultra relativistic Quantum Molecular Dynamics (UrQMD) transport model. The calculations are done for p+p, Be+Be, Ar+Sc, and Pb+Pb collisions at the CERN Super Proton Synchrotron energy range to reveal the system size dependence of hadron production. For the HRG calculations the canonical ensemble is imposed for all conserved charges. In the UrQMD simulations the centrality selection in nucleus-nucleus collisions is done by calculating the forward energy $E_{\mathrm{F}}$ deposited in the Projectile Spectator Detector, and the acceptance maps of the NA61/SHINE detectors are used. A comparison of the HRG and UrQMD results with the data of the NA61/SHINE Collaboration is done. To understand a difference of the event-by-event fluctuations in p+p and heavy ion collisions the centrality selection procedure in the sample of all inelastic p+p events is proposed and analyzed within the UrQMD simulations.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2019)·21 citations
3. 03*

   Weak interference between the 1${}^{-}$ states in the vicinity of $\alpha$-particle threshold of ${}^{16}$O

   M. Katsuma

   The subthreshold 1${}_1^{-}$ state at an excitation energy $E_x=7.12$ MeV in ${}^{16}$O has been believed to enhance the $S$-factor of ${}^{12}$C($\alpha$,$\gamma$)${}^{16}$O. The enhancement seems to originate from strong interference between 1${}_1^{-}$ and 1${}_2^{-}$ ($E_x\approx 9.6$ MeV) in the vicinity of the $\alpha$-particle threshold. However, weak interference between them and a resulting small $E$1 $S$-factor are exemplified with $R$-matrix theory. Including a higher-order correction of the resonance parameters, the present example appears to reproduce the experimental data consistently. It would therefore be possible that the $E$1 $S$-factor is reduced at low energies.

   ↳ nucl-thastro-ph.SRnucl-exSpringer Proc.Phys.(2019)·1 citation
4. 04*

   First results on ${\mathrm{K}}^{\ast }(892{)}^{\pm }$ resonance production in pp collisions with ALICE at the LHC

   Kunal Garg🇮🇹

   The study of strange hadronic resonances in pp collisions contributes to the study of strangeness production in small systems. Measurements in pp collisions constitute a reference for the study in larger colliding systems and provide constraints for tuning QCD-inspired event generators. Since the lifetimes of short-lived resonances such as ${\mathrm{K}}^{\ast }(892{)}^{\pm }$ ($\tau \sim 4$ fm/\textit{c}) are comparable with the lifetime of the fireball produced in heavy-ion collisions, regeneration and rescattering effects can modify the measured yield, especially at low transverse momentum. The first results for the ${\mathrm{K}}^{\ast }(892{)}^{\pm }$ resonance obtained in inelastic pp collisions at $\sqrt{\text{s}}=$ 5.02, 8, and 13 TeV will be shown. The ${\mathrm{K}}^{\ast }(892{)}^{\pm }$ has been measured at mid-rapidity via its hadronic decay channel ${\mathrm{K}}^{\ast }(892{)}^{\pm }\to {\mathrm{K}}_{\mathrm{S}}^0+{\pi }^{\pm }$, with the ALICE detector. In particular, the transverse momentum ($p_{\mathrm{T}}$) spectrum, integrated yields, $⟨p_{\mathrm{T}}⟩$ and ratio to stable hadrons will be presented. The ${\mathrm{K}}^{\ast }(892{)}^{\pm }$ results are compared with ${\mathrm{K}}^{\ast }(892{)}^0$ measurements and with commonly-used Monte Carlo models. Measurements at 13 TeV are in addition a baseline for comparison with pp measurements at other LHC energies.

   ↳ hep-exnucl-exPoS(2018)·1 citation
5. 05*

   Detecting Cherenkov Light From 1-2 MeV Electrons in Linear Alkylbenzene

   Julieta Gruszko🇺🇸 · Brian Naranjo🇺🇸 · Byron Daniel🇺🇸 · Andrey Elagin🇺🇸 · Diana Gooding🇺🇸 · Chris Grant🇺🇸 · Jonathan Ouellet🇺🇸 · Lindley Winslow🇺🇸

   The FlatDot detector has been used to demonstrate the separation of Cherenkov and scintillation light for 1 to 2MeV electrons in linear alkylbenzene (LAB). With an average PMT transit time spread (TTS) of 200ps, the early light in each event is clearly dominated by the Cherenkov signal, which on average comprises $86_{-3}^{+2}\%$ of the light collected in the first 4.1ns of each event. The spatial distributions of the Cherenkov and scintillation light are found to match those predicted in Monte Carlo simulations. This is a key step towards demonstrating direction reconstruction of $\beta$ decays, a technique that could reduce ${}^8$B solar neutrino backgrounds for neutrinoless double-beta decay experiments in liquid scintillator.

   ↳ physics.ins-detnucl-exJINST(2019)·32 citations
6. 06*

   Studies Of The Polarization Of Gamma Photons Originating From The Decay of Positronium Atoms

   Sushil K. Sharma🇮🇳 · Nikodem Krawczyk🇵🇱 · Juhi Raj (for the J-PET collaboration)🇵🇱

   The precise measurements of the Compton scatterings of photons originating from the decay of positronium atoms can reveal information about their polarizations. J-PET detector is constructed of 192 plastic scintillators and is unique to study the scattering correlations of the annihilation photons with an angular precision of several degrees. In this work, we present the first experimental evidence showing the feasibility of measuring the photons relative polarization using the J-PET detector.

   ↳ physics.ins-detnucl-exAIP Conf.Proc.(2019)·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.