Tue·Sep 22, 2020Tuesday·September 22, 2020

1. 01*

   Pseudorapidity distributions of charged particles as a function of mid and forward rapidity mutiplicities in pp collisions at $\sqrt{s}$ = 5.02, 7 and 13 TeV

   ALICE Collaboration

   The multiplicity dependence of the pseudorapidity density of charged particles in proton-proton (pp) collisions at centre-of-mass energies $\sqrt{s}$ = 5.02, 7 and 13 TeV measured by ALICE is reported. The analysis relies on track segments measured in the midrapidity range ($|\eta |<1.5$). Results are presented for inelastic events having at least one charged particle produced in the pseudorapidity interval $|\eta |<1$ (${\mathrm{INEL}}_{>0}$). The multiplicity dependence of the pseudorapidy density of charged particles is measured with mid and forward rapidity multiplicity estimators, the latter being less affected by autocorrelations. A detailed comparison with predictions from the PYTHIA 8 and EPOS LHC event generators is also presented. Both generators provide a good description of the data.

   nucl-exhep-exEPJC(2021)·84 citations
2. 02*

   Studying Short-Range Correlations with Real Photon Beams at GlueX

   O. Hen · M. Patsyuk · E. Piasetzky · A. Schmidt · A. Somov · H. Szumila-Vance · L. B. Weinstein · D. Dutta · H. Gao · M. Amaryan · A. Ashkenazi · A. Beck and 50 other authors

   The past few years has seen tremendous progress in our understanding of short-range correlated (SRC) pairing of nucleons within nuclei, much of it coming from electron scattering experiments leading to the break-up of an SRC pair. The interpretation of these experiments rests on assumptions about the mechanism of the reaction. These assumptions can be directly tested by studying SRC pairs using alternate probes, such as real photons. We propose a 30-day experiment using the Hall D photon beam, nuclear targets, and the GlueX detector in its standard configuration to study short-range correlations with photon-induced reactions. Several different reaction channels are possible, and we project sensitivity in most channels to equal or exceed the 6 GeV-era SRC experiments from Halls A and B. The proposed experiment will therefore decisively test the phenomena of np dominance, the short-distance NN interaction, and reaction theory, while also providing new insight into bound nucleon structure and the onset of color transparency.

   nucl-ex10 citations
3. 03*

   Comment on "A sensitivity study of the primary correlators used to characterize chiral-magnetically-driven charge separation'' by Magdy, Nie, Ma, and Lacey

   Yicheng Feng🇺🇸 · Fuqiang Wang🇺🇸 · Jie Zhao🇺🇸

   This note points out an apparent error in the publication Phys.~Lett.~B {\bf 809} (2020) 135771 by Magdy, Nie, Ma, and Lacey.

   nucl-exnucl-th1 citation
4. 04*

   Coupled-channel treatment of ${}^7\mathrm{Li}(n,\gamma {)}^8\mathrm{Li}$ in effective field theory

   Renato Higa🇧🇷 · Pradeepa Premarathna🇺🇸 · Gautam Rupak🇺🇸

   The E1 contribution to the capture reaction ${}^7\mathrm{Li}(n,\gamma {)}^8\mathrm{Li}$ is calculated at low energies. We employ a coupled-channel formalism to account for the ${}^7{\mathrm{Li}}^{\star }$ excited core contribution. We develop a halo effective field theory power counting where capture in the spin $S=2$ channel is enhanced over the $S=1$ channel. A next-to-leading order calculation is presented where the excited core contribution is shown to affect only the overall normalization of the cross section. The momentum dependence of the capture cross section, as a consequence, is the same in a theory with or without the excited ${}^7{\mathrm{Li}}^{\star }$ degree of freedom at this order of the calculation. The kinematical signature of the ${}^7{\mathrm{Li}}^{\star }$ core is negligible at momenta below 1 MeV and significant only beyond the $3^{+}$ resonance energy, though still compatible with a next-to-next-to-leading order correction. We compare our formalism with a previous halo effective field theory calculation [Zhang, Nollett, and Phillips, Phys. Rev. C 89, 024613 (2014)] that also treated the ${}^7{\mathrm{Li}}^{\star }$ core as an explicit degree of freedom. Our formal expressions and analysis disagree with this earlier work in several aspects.

   ↳ nucl-thastro-ph.SRnucl-exEPJA(2021)·7 citations
5. 05*

   Collectivity in large and small systems formed in ultrarelativistic collisions

   Rajeev S Bhalerao🇮🇳

   Collective flow of the final-state hadrons observed in ultrarelativistic heavy-ion collisions or even in smaller systems formed in high-multiplicity pp and p/d/${}^3$He-nucleus collisions is one of the most important diagnostic tools to probe the initial state of the system and to shed light on the properties of the short-lived, strongly-interacting many-body state formed in these collisions. Limited, in the initial years, to the study of mainly the directed and elliptic flows -- the first two Fourier harmonics of the single-particle azimuthal distribution -- this field has evolved in recent years into a much richer area of activity. This includes not only higher Fourier harmonics and multiparticle cumulants, but also a variety of other related observables, such as the ridge seen in two-particle correlations, flow decorrelation, symmetric cumulants and event-plane correlators which measure correlations between the magnitudes or phases of the complex flows in different harmonics, coefficients that measure the nonlinear hydrodynamic response, statistical properties, such as the non-Gaussianity of the flow fluctuations, etc. We present a Tutorial Review of the modern flow picture and the various aspects of the collectivity -- an emergent phenomenon in quantum chromodynamics.

   ↳ nucl-thhep-phnucl-exEur.Phys.J.ST(2021)·19 citations
6. 06*

   Charge-dependent flow as evidence of strong electromagnetic fields in heavy-ion collisions

   Andrea Dubla🇩🇪 · Umut Gürsoy🇳🇱 · Raimond Snellings🇳🇱

   The extremely large electromagnetic fields generated in heavy-ion collisions provide access to novel observables that are expected to constrain various key transport properties of the quark-gluon plasma and could help solve one of the outstanding puzzles in QCD: the strong CP problem. In this review we present a brief overview of the theoretical and experimental characterization of these electromagnetic fields. After reviewing the current state, emphasising one of the observables -- the charge-dependent flow -- we discuss the various discrepancies between the measurements and theoretical predictions. Finally, to help resolve the discrepancies, we suggest new measurements and theoretical ideas.

   ↳ hep-phhep-exhep-thnucl-exMod.Phys.Lett.A(2020)·36 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.