Tue·Sep 8, 2020Tuesday·September 8, 2020

1. 01*

   Evidence for top quark production in nucleus-nucleus collisions

   Georgios Konstantinos Krintiras (on behalf of the CMS Collaboration)🇺🇸

   Using $1.7\pm 0.1\mathrm{n}{\mathrm{b}}^{-1}$ of lead-lead ($A=208$) collision data recorded by the CMS experiment at a nucleon-nucleon center-of-mass energy of 5.02 TeV, we report evidence of top quark pair ($\mathrm{t}\bar{\mathrm{t}}$) production. The $\mathrm{t}\bar{\mathrm{t}}$ cross section (${\sigma }_{\mathrm{t}\bar{\mathrm{t}}}$) is extracted from likelihood fits to a multivariate discriminator using lepton kinematic variables in dilepton final states and two methods. One method relies on the leptonic information alone, and the second one exploits, in addition, the presence of bottom quarks. The measured ${\sigma }_{\mathrm{t}\bar{\mathrm{t}}}$ is $2.54_{-0.74}^{+0.84}$ and $2.03_{-0.64}^{+0.71}\mu \mathrm{b}$ in the two cases, respectively, consistent with predictions from perturbative quantum chromodynamics. We demonstrate, for the first time, that top quark decay products (leptonically decaying W bosons and bottom quarks) can be identified, irrespective of any possible final-state interactions with the quark-gluon plasma.

   nucl-exPoS(2021)·0 citations
2. 02*

   Investigation of the elliptic flow fluctuations of the identified particles using the A Multi-Phase Transport model

   Niseem Magdy🇺🇸 · Xu Sun🇺🇸 · Zhenyu Ye🇺🇸 · Olga Evdokimov🇺🇸 · Roy A. Lacey🇺🇸

   A Multi-Phase Transport (AMPT) model is used to study the elliptic flow fluctuations of identified particles using participant and spectator event planes. The elliptic flow measured using the first order spectator event plane is expected to give the elliptic flow relative to the true reaction plane which suppresses the flow fluctuations. However, the elliptic flow measured using the second-order participant plane is expected to capture the elliptic flow fluctuations. Our study shows that the first order spectator event plane could be used to study the elliptic flow fluctuations of the identified particles in the AMPT model. The elliptic flow fluctuations magnitude shows weak particle species dependence and transverse momentum dependence. Such observation will have important implications for understanding the source of the elliptic flow fluctuations.

   nucl-exnucl-thUniverse(2020)·17 citations
3. 03*

   Measurements of heavy-flavor jets with ALICE at the LHC

   Ashik Ikbal Sheikh (for the ALICE Collaboration)🇮🇳

   Heavy quarks created in ultra-relativistic heavy-ion collisions are mostly produced in hard QCD processes during the early stages of the reaction. They interact with the hot and cold nuclear matter throughout the evolution of the medium via semi-hard and soft processes such as energy loss via gluon radiations and collisions. Nuclear modification of heavy flavors in p-A systems provides insight into cold nuclear matter effects such as (anti)shadowing and $k_T$-broadening, and serves as a baseline for A-A studies. In addition to that the fully reconstructed heavy-flavor jets provide additional information on the flavor (or mass) dependence of fragmentation, color charge effects as well as insight into the contribution of late gluon splitting. In this contribution, we present the measurements of $b$-jet production in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV and $c$-jet production in pp, p-Pb and Pb-Pb collisions measured by the ALICE experiment at the LHC. The measurements of the nuclear modification factors for $c$-jet in p-Pb and Pb-Pb collisions are also presented. The experimental measurements are compared with the results from Monte Carlo event generators (PYTHIA 6, PYTHIA 8 and Herwig 7) and the NLO pQCD calculations (POWHEG+PYTHIA6). We find good agreement of the measurements with the results from Monte Carlo event generators and from NLO pQCD calculations.

   nucl-exhep-phnucl-thNucl.Part.Phys.Proc.(2020)·3 citations
4. 04*

   Measurements of ${}^{nat}Pb(p,xn){}^{201-207}Bi$, ${}^{204}Pb(p,1-4n){}^{201-204}Bi$ and ${}^{206}Pb(p,3n){}^{204}Bi$ cross-sections at astrophysical energies ($E_p\le 30MeV$)

   P V Guillaumon🇮🇹 · I D Goldman🇮🇱 · V R Vanin · H Barcellos de Oliveira

   Cross-sections for ${}^{nat}Pb(p,xn){}^{201-207}Bi$, ${}^{204}Pb(p,1-4n){}^{201-204}Bi$ and ${}^{206}Pb(p,3n){}^{204}Bi$ reactions have been determined in the astrophysical energy range $20-30MeV$. The analysis were performed by $\gamma$-spectroscopy associated with half-lives measurements. The results were compared with previously experimental data, when available, and with theoretical calculations performed using TALYS code. We report a possible new $\gamma$ transition from ${}^{204m}Pb$ and other theoretical discrepancies, probably due overestimation of the Coulomb barrier and neutron binding energy. Also reported are new determinations of the energies and intensities of the $\gamma$'s emitted in the decays of ${}^{205,206}Bi$. We discuss possible implications for the r/rp-processes in neutrino-driven wind in supernovae and neutron stars mergers.

   nucl-exnucl-th0 citations
5. 05*

   Recent progress in multiple chiral doublet bands

   Shou-Yu Wang

   The recent progress of multiple chiral doublet bands (M$\chi$D) is reviewed for both experimental and theoretical sides. In particular, the experimental findings, theoretical predictions, selection rule for electromagnetic transitions, M$\chi$D with octupole correlations and some related topics are highlighted. Based on these discussions, it is of highly scientific interest to search for the more M$\chi$D as well as the possible chiral wobblers, chirality-parity quartet and chirality-pseudospin triplet (or quartet) bands in nuclear system.

   nucl-exCPC(2020)·19 citations
6. 06*

   A Proposed Forward Silicon Tracker for the Future Electron-Ion Collider and Associated Physics Studies

   Cheuk-Ping Wong🇺🇸 · Xuan Li🇺🇸 · Melynda Brooks🇺🇸 · Matthew J. Durham🇺🇸 · Ming Xiong Liu🇺🇸 · Astrid Morreale🇺🇸 · Cesar da Silva🇺🇸 · Walter E. Sondheim🇺🇸

   The future Electron-Ion Collider (EIC) will explore several fundamental questions in a broad Bjorken-x ($x_{BJ}$) and $Q^2$ phase space. Heavy flavor and jet products are ideal probes to precisely study the tomography of nucleon/nuclei structure, help solve the proton spin puzzle and understand the hadronizaton processes in vacuum or in the QCD medium. Due to the asymmetric collisions at the EIC, most of the final state hadrons are produced in the nucleon/nuclei beam going (forward) direction. A silicon vertex/tracking is critical to precisely measure these forward hadrons at the EIC. Details of different conceptual designs of the proposed Forward Silicon Tracker (FST) and the relevant detector performance are presented in this technical note. The associated heavy flavor and jet studies with the evaluated FST performance are discussed as well.

   nucl-exhep-ex10 citations
7. 07*

   Light meson nuclear modification factor in p-Pb collisions over an unprecedented $p_{\mathrm{T}}$ range with ALICE

   Nicolas Schmidt🇺🇸

   Light neutral meson differential invariant cross section and nuclear modification factor measurements have been carried out with the ALICE detector at the CERN LHC in pp collisions at $\sqrt{s}=8$ TeV and p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=8.16$ TeV. The analysis combines results from several partially independent reconstruction techniques where the ${\pi }^0$ and $\eta$ meson decay photons were detected with the electromagnetic calorimeter, EMCal, the photon spectrometer, PHOS, or via reconstruction of $e^{+}{e}^{-}$ pairs from conversions in the ALICE detector material using the central tracking system. The neutral pion measurement reaching a $p_{\mathrm{T}}$ of 200 GeV/$c$ poses as the highest measured identified particle spectrum to date while the $\eta$ meson is measured to an unprecedented $p_{\mathrm{T}}$ of 50 GeV/$c$. The spectra are found to be generally overestimated by NLO pQCD calculations. The nuclear modification factors of both mesons exhibit a suppression for $p_{\mathrm{T}}<10$ GeV/$c$ which is stronger compared to previous measurements at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV and consistent with CGC and cold nuclear matter energy loss calculations. For $p_{\mathrm{T}}>10$ GeV/$c$, $R_{\mathrm{pPb}}$ is consistent with unity and theory predictions.

   nucl-exPoS(2021)·0 citations
8. 08*

   The alternating-parity bands of \element{236,238}{U} and \element{238,240}{Pu} in a particle-number conserving method based on cranked shell model

   Xiao-Tao He🇨🇳 · Yu-Chun Li

   The particle-number conserving (PNC) method in the framework of cranked shell model (CSM) is developed to deal with the reflection-asymmetric nuclear system by applying the $S_x$ symmetry. Based on an octupole-deformed Nilsson potential, the alternating-parity bands in \element{236,238}{U} and \element{238,240}{Pu} are investigated. The experimental kinematic moments of inertia (MoI) and the angular momentum alignments of all studied bands are reproduced well in the PNC-CSM calculations. The striking difference of rotational behaviors between U and Pu isotopes can be linked to the strength of octupole correlations. The upbendings of the alternating-parity bands in\element{236,238}{U} are due to the alignments of pairs of nucleons occupying $\nu g_{9/2}$, $\pi f_{7/2}$ orbitals and $\nu j_{15/2}$, $\pi i_{13/2}$ high-$j$ intruder orbitals. Particularly, the interference terms of nucleon occupying the octupole-correlation pairs of ${\nu }^2{j}_{15/2}{g}_{9/2}$ and of ${\pi }^2{i}_{13/2}{f}_{7/2}$ give a very important contribution to the suddenly gained alignments.

   ↳ nucl-thnucl-exPRC(2020)·13 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.