Nuclear Theory·nucl-th

Friday·August 21, 2020

9 papers—5 primary·4 cross-listed

06
[Submitted on 19 Aug 2020] (cross-list from hep-ph)
Data-driven quark and gluon jet modification in heavy-ion collisions
Jasmine Brewer🇺🇸 · Jesse Thaler🇺🇸 · Andrew P. Turner🇺🇸
Whether quark- and gluon-initiated jets are modified differently by the quark-gluon plasma produced in heavy-ion collisions is a long-standing question that has thus far eluded a definitive experimental answer. A crucial complication for quark-gluon discrimination in both proton-proton and heavy-ion collisions is that all measurements necessarily average over the (unknown) quark-gluon composition of a jet sample. In the heavy-ion context, the simultaneous modification of both the fractions and substructure of quark and gluon jets by the quark-gluon plasma further obscures the interpretation. Here, we demonstrate a fully data-driven method for separating quark and gluon contributions to jet observables using a statistical technique called topic modeling. Assuming that jet distributions are a mixture of underlying "quark-like" and "gluon-like" distributions, we show how to extract quark and gluon jet fractions and constituent multiplicity distributions as a function of the jet transverse momentum. This proof-of-concept study is based on proton-proton and heavy-ion collision events from the Monte Carlo event generator Jewel with statistics accessible in Run 4 of the Large Hadron Collider. These results suggest the potential for an experimental determination of quark and gluon jet modifications.
Comments:
7 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2008.08596 [pdf]
PRC(2021)·31 citations
07
[Submitted on 20 Aug 2020] (cross-list from nucl-ex)
Measurement of $γ$ +jet and $π^{0}$ +jet in central Au+Au collisions at $s_{NN}$ = 200 GeV with the STAR experiment
Nihar Ranjan Sahoo (for the STAR Collaboration)🇨🇳
We present the semi-inclusive measurement of charged jets recoiling from direct-photon and $π^{0}$ triggers in central Au+Au collisions at $s_{NN}$ = 200 GeV, using a dataset with integrated luminosity 13 $n b^{- 1}$ recorded by the STAR experiment in 2014. The photon and $π^{0}$ triggers are selected within transverse energy ( $E_{T}^{trig}$ ) between 9 GeV and 20 GeV. Charged jets are reconstructed with the anti- $k_{T}$ algorithm with resolution parameters R = 0.2 and 0.5. A Mixed-Event technique developed previously by STAR is used to correct the recoil jet yield for uncorrelated background, enabling recoil jet measurements over a broad $p_{T, jet}$ range. We report fully corrected charged-jet yields recoiling from direct-photon and $π^{0}$ triggers for the above two jet radii and also discuss the jet R dependence of in-medium parton energy loss at the top RHIC energy.
Comments:
5 pages, 4 figures, Hard Probes 2020
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2008.08789 [pdf]
PoS(2021)·7 citations
08
[Submitted on 20 Aug 2020] (cross-list from hep-ph)
Constraints on new physics from an improved calculation of parity violation in $^{133}$ Cs
B. K. Sahoo🇮🇳 · B. P. Das🇯🇵
We report the result of our calculation of the nuclear spin-independent parity violating electric dipole transition amplitude ( $E 1_{P V}$ ) for the $6 s^{2} S_{1/2} - 7 s^{2} S_{1/2}$ transition in $^{133}$ Cs to an accuracy of 0.3\% using a variant of the perturbed relativistic coupled-cluster theory. In the present work, we treat the contributions of both the low-lying and high-lying excited states to the above mentioned amplitude on the same footing, thereby overcoming the limitations of previous high accuracy relativistic coupled cluster calculations. We obtain an accurate value for the vector polarizability ( $β$ ) for the above transition and by combining it with the results from our present calculation of $E 1_{P V}$ and the latest measurement of $I m (E 1_{P V} / β)$ , we extract the nuclear weak charge ( $Q_{W}$ ); and analyze its deviation from its value in the Standard Model (SM) in order to constrain certain scenarios of new physics beyond the SM.
Comments:
14 pages, 10 tables and 1 figure
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph); Computational Physics (physics.comp-ph)
arXiv:
2008.08941 [pdf]
8 citations
09
[Submitted on 20 Aug 2020] (cross-list from nucl-ex)
Measurement of the Generalized Polarizabilities of the Proton at Intermediate $Q^{2}$
H.Fonvieille (1) · J. Beričič (2) · L. Correa (1)(3) · M. Benali (1) · P. Achenbach (3) · C. Ayerbe Gayoso (3) · J.C. Bernauer (4)(5) · A. Blomberg (6) · R. Böhm (3) · D. Bosnar (7) · L. Debenjak (2) · A. Denig (3) and 27 other authors
Background: Generalized polarizabilities (GPs) are important observables to describe the nucleon structure, and measurements of these observables are still scarce. Purpose: This paper presents details of a virtual Compton scattering (VCS) experiment, performed at the A1 setup at the Mainz Microtron by studying the $e p \to e p γ$ reaction. The article focuses on selected aspects of the analysis. Method: The experiment extracted the $P_{LL} - P_{T T} / ϵ$ and $P_{L T}$ structure functions, as well as the electric and magnetic GPs of the proton, at three new values of the four-momentum transfer squared $Q^{2}$ : 0.10, 0.20 and 0.45 GeV $^{2}$ . Results: We emphasize the importance of the calibration of experimental parameters. The behavior of the measured $e p \to e p γ$ cross section is presented and compared to the theory. A detailed investigation of the polarizability fits reveals part of their complexity, in connection with the higher-order terms of the low-energy expansion. Conclusions: The presented aspects are elements which contribute to minimize the systematic uncertainties and improve the precision of the physics results.
Comments:
16 pages, 15 figures, Version 4, regular article to appear in Phys.Rev.C, more final version of some figures
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2008.08958 [pdf]
PRC(2021)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE

Data-driven quark and gluon jet modification in heavy-ion collisions

Measurement of γ+jet and π0+jet in central Au+Au collisions at sNN​​ = 200 GeV with the STAR experiment

Constraints on new physics from an improved calculation of parity violation in 133Cs

Measurement of the Generalized Polarizabilities of the Proton at Intermediate Q2

Affiliations

Measurement of $γ$ +jet and $π^{0}$ +jet in central Au+Au collisions at $s_{NN}$ = 200 GeV with the STAR experiment

Constraints on new physics from an improved calculation of parity violation in $^{133}$ Cs

Measurement of the Generalized Polarizabilities of the Proton at Intermediate $Q^{2}$