Differential measurements of jet substructure and partonic energy loss in Au$+$Au collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV

Abstract

The STAR collaboration presents jet substructure measurements related to both the momentum fraction and the opening angle within jets in \pp and \AuAu collisions at \sqrtsn $=200$ GeV. The substructure observables include SoftDrop groomed momentum fraction (\zg), groomed jet radius (\rg), and subjet momentum fraction (\zsj) and opening angle (\tsj). The latter observable is introduced for the first time. Fully corrected subjet measurements are presented for \pp collisions and are compared to leading order Monte Carlo models. The subjet \tsj~distributions reflect the jets leading opening angle and are utilized as a proxy for the resolution scale of the medium in \AuAu collisions. We compare data from \AuAu collisions to those from \pp which are embedded in minimum-bias \AuAu events in order to include the effects of detector smearing and the heavy-ion collision underlying event. The subjet observables are shown to be more robust to the background than \zg~and \rg. We observe no significant modifications of the subjet observables within the two highest-energy, back-to-back jets, resulting in a distribution of opening angles and the splittings that are vacuum-like. We also report measurements of the differential di-jet momentum imbalance ($A_{\mathrm{J}}$) for jets of varying \tsj. We find no qualitative differences in energy loss signatures for varying angular scales in the range $0.1<$ \tsj $<0.3$, leading to the possible interpretation that energy loss in this population of high momentum di-jet pairs, is due to soft medium-induced gluon radiation from a single color-charge as it traverses the medium.

17 pages, 11 figures, 1 Appendix. Published version

References in corpus (23)

• PYTHIA 6.4 Physics and Manual
• An Introduction to PYTHIA 8.2
• Herwig++ Physics and Manual
• Measurements of the Nuclear Modification Factor for Jets in Pb+Pb Collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV with the ATLAS Detector
• Measurement of jet fragmentation in PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV
• Sudakov Safety in Perturbative QCD
• Measurement of jet suppression in central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV
• Measurement of inclusive jet charged-particle fragmentation functions in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV with the ATLAS detector
• Jet quenching and medium response in high-energy heavy-ion collisions: a review
• Measurement of jet fragmentation into charged particles in pp and PbPb collisions at sqrt(s[NN]) = 2.76 TeV
• Jets in Hadron-Hadron Collisions
• Sensitivity of jet substructure to jet-induced medium response
• Particle-level pileup subtraction for jets and jet shapes
• Medium-induced gluon radiation with full resummation of multiple scatterings for realistic parton-medium interactions
• Measurement of inclusive charged-particle jet production in Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV
• Cone size dependence of jet suppression in heavy-ion collisions
• Decomposing transverse momentum balance contributions for quenched jets in PbPb collisions at sqrt(s[NN]) = 2.76 TeV
• A local Monte Carlo framework for coherent QCD parton energy loss
• Measurement of Groomed Jet Substructure Observables in \pp Collisions at $\sqrt{s}=200$ GeV with STAR
• Time reclustering for jet quenching studies
• Identifying groomed jet splittings in heavy-ion collisions
• A Theoretical Assessment of Jet-Hadron Correlations
• Dynamical grooming meets LHC data

Cited by in corpus (12)

• Dynamically groomed jet radius in heavy-ion collisions
• Measurement of substructure-dependent jet suppression in Pb+Pb collisions at 5.02 TeV with the ATLAS detector
• Medium Response and Jet-Hadron Correlations in Relativistic Heavy-Ion Collisions
• Predictions for the sPHENIX physics program
• Jet radius and momentum splitting fraction with dynamical grooming in heavy-ion collisions
• Measurement of groomed event shape observables in deep-inelastic electron-proton scattering at HERA
• Multiplicity dependence of charged-particle intra-jet properties in pp collisions at $\sqrt{s}$ = 13 TeV
• Measurement of inclusive jet cross section and substructure in $p$$+$$p$ collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV
• D${}^0$-meson-tagged jet axes difference in proton-proton collisions at $\sqrt{\text{s}}=5.02$ TeV
• Deep Image Reconstruction for Background Subtraction in Heavy-Ion Collisions
• Generalized angularities and differential jet shapes measurements from STAR at $\sqrt{s}=$ 200 GeV
• Jet substructure of light and heavy flavor jets at RHIC