Fri·May 1, 2020Friday·May 1, 2020

1. 01*

   Studies of Quark and Gluon Contributions to Jets using Jet Charge Measurements in pp and PbPb Collisions

   Dhanush Anil Hangal (on behalf of the CMS Collaboration)🇺🇸

   Jet charge, defined as the momentum-weighted sum of the electric charges of particles inside a jet is sensitive to the electric charge of the initiating parton and can be used to study the color charge dependence of the parton energy loss in the QGP. In this paper, the first measurements of jet charge in heavy-ion collisions are presented using lead-lead (PbPb) collision data and compared to results from proton-proton (pp) data at the same collision energy. The measurements are unfolded for detector and background effects and are studied differentially in $p_{\mathrm{T}}$ and additionally as a function of collision centrality in PbPb collisions. We also present a template fitting technique for estimating the fractions of quark- and gluon-initiated jets in pp and PbPb collisions based on Monte Carlo templates. This analysis uses pp and PbPb collision data collected by the CMS experiment at $\sqrt{{\mathrm{s}}_{\mathrm{NN}}}=5.02$ TeV.

   nucl-exhep-exNPA(2021)·1 citation
2. 02*

   Beam-Normal Single Spin Asymmetry in Elastic Electron Scattering off ${}^{28}$Si and ${}^{90}$Zr

   A.Esser · M.Thiel · P.Achenbach · K.Aulenbacher · S.Aulenbacher · S.Baunack · D.Bosnar · S.Caiazza · M.Christmann · M.Dehn · M.O.Distler · L.Doria and 21 other authors

   We report on a new measurement of the beam-normal single spin asymmetry $A_{\mathrm{n}}$ in the elastic scattering of 570 MeV transversely polarized electrons off ${}^{28}$Si and ${}^{90}$Zr at $Q^2=0.04{\mathrm{GeV}}^2/c^2$. The studied kinematics allow for a comprehensive comparison with former results on ${}^{12}$C. No significant mass dependence of the beam-normal single spin asymmetry is observed in the mass regime from ${}^{12}$C to ${}^{90}$Zr.

   nucl-exPLB(2020)·14 citations
3. 03*

   Classification of Equation of State in Relativistic Heavy-Ion Collisions Using Deep Learning

   Yu. Kvasiuk🇳🇴 · E. Zabrodin🇳🇴 · L. Bravina🇳🇴 · I. Didur🇺🇦 · M. Frolov🇺🇦

   Convolutional Neural Nets, which is a powerful method of Deep Learning, is applied to classify equation of state of heavy-ion collision event generated within the UrQMD model. Event-by-event transverse momentum and azimuthal angle distributions of protons are used to train a classifier. An overall accuracy of classification of 98\% is reached for Au+Au events at $\sqrt{s_{NN}}=11$ GeV. Performance of classifiers, trained on events at different colliding energies, is investigated. Obtained results indicate extensive possibilities of application of Deep Learning methods to other problems in physics of heavy-ion collisions.

   ↳ nucl-thcs.LGhep-phnucl-exJHEP(2020)·12 citations
4. 04*

   Constraining the quadrupole deformation of atomic nuclei with relativistic nuclear collisions

   Giuliano Giacalone🇫🇷

   Preliminary data by the STAR collaboration at the BNL Relativistic Heavy Ion Collider shows that the elliptic flow, $v_2$, and the average transverse momentum, $⟨p_t⟩$, of final-state hadrons produced in high-multiplicity ${}^{238}$U+${}^{238}$U collisions are negatively correlated. This observation brings experimental evidence of a significant prolate deformation, $\beta \approx 0.3$, in the colliding ${}^{238}$U nuclei. I show that a quantitative description of this new phenomenon can be achieved within the hydrodynamic framework of heavy-ion collisions, and that thus such kind of data in the context of high-energy nuclear experiments can help constrain the quadrupole deformation of the colliding species.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2020)·74 citations
5. 05*

   Determining $B(E1)$ distributions of weakly bound nuclei from breakup cross sections using Continuum Discretized Coupled Channels calculations. Application to ${}^{11}$Be

   A.M. Moro🇪🇸 · J.A. Lay🇪🇸 · J.Gómez-Camacho🇪🇸

   A novel method to extract the $B(E1)$ strength of a weakly bound nucleus from experimental Coulomb dissociation data is proposed. The method makes use of continuum discretized coupled channels (CDCC) calculations, in which both nuclear and Coulomb forces are taken into account to all orders. This is a crucial advantage with respect to the standard procedure based on the Equivalent Photon Method (EPM) which does not properly take into account nuclear distortion, higher order coupling effects, or Coulomb-nuclear interference terms. The procedure is applied to the ${}^{11}$Be nucleus using two sets of available experimental data at different energies, for which seemingly incompatible $B(E1)$ have been reported using the EPM. We show that the present procedure gives consistent $B(E1)$ strengths, thus solving the aforementioned long-standing discrepancy between the two measurements.

   ↳ nucl-thnucl-exPLB(2020)·18 citations
6. 06*

   QCD Hidden-Color Hexa-diquark in the Central Core of Nuclei

   Jennifer Rittenhouse West🇺🇸 · Stanley J. Brodsky🇺🇸 · Guy F. de Teramond🇨🇷 · Alfred S. Goldhaber🇺🇸 · Ivan Schmidt🇨🇱

   Hidden-color configurations are a key prediction of QCD with important physical consequences. In this work we examine a QCD color-singlet configuration in nuclei formed by combining six scalar $[ud]$ diquarks in a strongly bound $\mathrm{SU}(3{)}_{\mathrm{C}}$ channel. The resulting hexadiquark state is a charge-2, spin-0, baryon number-4, isospin-0, color-singlet state. It contributes to alpha clustering in light nuclei and to the additional binding energy not saturated by ordinary nuclear forces in \he as well as the alpha-nuclei sequence of interest for nuclear astrophysics. We show that the strongly bound combination of six scalar isospin-0 $[ud]$ diquarks within the nuclear wave function - relative to free nucleons - provides a natural explanation of the EMC effect measured by the CLAS collaboration's comparison of nuclear parton distribution function ratios for a large range of nuclei. These experiments confirmed that the EMC effect; i.e., the distortion of quark distributions within nuclei, is dominantly identified with the dynamics of neutron-proton (``isophobic'') short-range correlations within the nuclear wave function rather than proton-proton or neutron-neutron correlations.

   ↳ hep-phnucl-exnucl-thNPA(2021)·20 citations
7. 07*

   Quantifying alpha clustering in light nuclei from binding energies

   K. Fossez🇺🇸

   What is the origin of nuclear clustering and how does it emerge from the nuclear interaction? While there is ample experimental evidence for this phenomenon, its theoretical characterization directly from nucleons as degrees of freedom remains a challenge, making it difficult to improve nuclear forces using clustering observables. In this work, a simple ratio of energies based on effective scale arguments is proposed to assess the quality of nuclear forces on alpha clustering (${}^4\text{He}$) in bound and narrow ground-state nuclei. The proposed clustering ratio is parameter-free and correctly identify basic alpha clustering features in light nuclei. It is found that in nuclei ranging from ${}^6\text{Li}$ to ${}^{14}\text{C}$, state-of-the-art \textit{ab initio} nuclear forces underestimate the degree of alpha clustering in key nuclei such as ${}^8\text{Be}$ and ${}^{12}\text{C}$. Stringent constraints on binding energies are then provided by back-propagating 10\% relative uncertainties on the experimental clustering ratios using a parallel Markov chain Monte Carlo algorithm. It is demonstrated that the binding energies of the nuclei ${}^{6,7}$Li, ${}^7$Be, ${}^{10,11}$B, and ${}^{11}$C need to be obtained within tens of keV precision by nuclear forces to ensure a proper reproduction of basic alpha clustering features in light nuclei. This study provides a new and practical path to guide future optimizations of nuclear forces with a potential impact for medium-mass nuclei.

   ↳ nucl-thnucl-ex1 citation
8. 08*

   Setup commissioning for an improved measurement of the D(p,gamma)3He cross section at Big Bang Nucleosynthesis energies

   V. Mossa🇮🇹 · K. Stöckel🇩🇪 · F. Cavanna🇮🇹 · F. Ferraro🇮🇹 · M. Aliotta🇬🇧 · F. Barile🇮🇹 · D. Bemmerer🇩🇪 · A. Best🇮🇹 · A. Boeltzig🇮🇹 · C. Broggini🇮🇹 · C.G. Bruno🇬🇧 · A. Caciolli🇮🇹 and 35 other authors

   Among the reactions involved in the production and destruction of deuterium during Big Bang Nucleosynthesis, the deuterium-burning D(p,gamma)3He reaction has the largest uncertainty and limits the precision of theoretical estimates of primordial deuterium abundance. Here we report the results of a careful commissioning of the experimental setup used to measure the cross-section of the D(p,gamma)3He reaction at the Laboratory for Underground Nuclear Astrophysics of the Gran Sasso Laboratory (Italy). The commissioning was aimed at minimising all sources of systematic uncertainty in the measured cross sections. The overall systematic error achieved (< 3 %) will enable improved predictions of BBN deuterium abundance.

   ↳ physics.ins-detastro-ph.COnucl-exEPJA(2020)·34 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.