Collection of all abstracts from JetCorr for QM22

1) 
Submitter : Derek Andreson (TAMU)
Title: Measurements of jet suppression and shape modification with semi-inclusive $\gamma_{\text{dir}}$+jet and $\pi^{0}$+jet distributions in $pp$ and central Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV by STAR
Abstract: This talk reports measurements by STAR of the semi-inclusive distribution of charged-particle jets recoiling from direct photon ($\gamma_{\text{dir}}$+jet) and neutral pion ($\pi^{0)$+jet) triggers in $pp$ (25 pb$^{-1}$) and central Au+Au collisions (13 nb$^{-1}$) at $\sqrt{s_{NN}} = 200$ GeV.  The triggers have transverse energy between 9 and 20 GeV.  Jets are reconstructed using the anti-$k_{\text{T}}$ algorithm with resolution parameters $R = 0.2$ and 0.5.  Yield suppression due to jet quenching is measured by comparing distributions for the same triggers in $pp$ and central Au+Au collisions.  Recoil jet populations recoiling from $\gamma_{\text{dir}}$ and $\pi^{0 }$ triggers are expected to differ in their quark vs. gluon content and in-medium path-length distributions, and thus comparison of suppression between $\gamma_{\text{dir}}$+jet and $\pi^{0}$+jet elucidates the dependence of jet quenching on these factors.  The in-medium broadening of jets and the dependence of jet quenching on $R$ due to the medium response are measured by comparing recoil jet distributions with the two resolution parameters.  Comparisons are made to pQCD calculations and to theoretical models incorporating jet quenching.

2)
Submitter : Nihar Sahoo (SDU)
Title: Search for large-angle jet deflection using semi-inclusive γ+jet and h+jet correlations in p+p and Au+Au collisions at √sNN =200 GeV with STAR

Abstract: The measurement of jet deflection in the QGP promises to provide unique and incisive insight into the physics of jet quenching and the quasi-particle nature of the QGP. However, observation of large jet deflection requires the measurement of low pT jets, which is challenging in the high-background environment of heavy ion collisions. The semi-inclusive approach to coincidence measurements, with data-driven background mitigation, is the only established analysis technique that can carry out such measurements with the necessary high systematic precision. In this talk, the STAR experiment at RHIC reports the first measurement of semi-inclusive γ+jet and π0+jet azimuthal correlations in proton+proton and central Au+Au collisions at sNN=200 GeV. Charged-particle recoil jets are reconstructed using the anti-kT algorithm with R=0.2 and 0.5, and uncorrelated recoil jet yield is corrected using the Mixed Event approach. Azimuthal distributions are reported for recoil jets with pT,jet >5 GeV/c. The azimuthal distributions in p+p collisions are compared to NLO pQCD calculations including Sudakov broadening. The distributions in p+p and Au+Au collisions are also compared to theoretical model calculations incorporating jet quenching.

pdf: https://drupal.star.bnl.gov/STAR/system/files/QM2022_Abstract_Nihar.pdf

3)
Submitter : Tong Liu (Yale)
Title: Investigation of system size dependence of high pT hadron yield modification in nucleus-nucleus collisions with the STAR detector
Abstract: High transverse momentum (pT) partons are produced in the initial stages of high energy nucleus-nucleus collisions, and can be used as an excellent probe of both
initial-stage and final-stage phys. Especially, when a Quark-Gluon Plasma (QGP) is created, the partons will lose energy to this medium via collisional and radiative
processes. One common proxy to these effects is the invariant yield of high pT particles, where effects of different mechanisms can be reflected via its modification relative to p+p collisions. Though previous studies focus more on energy dependence of the modification, we here present results that target its sensitivity to the size of the collision system. We will present analysis using two datasets collected with the STAR detector: the large isobar (Ru+Ru & Zr+Zr) dataset collected in 2018 with 3.1 billion events per species, as well as the p+Au dataset collected in 2015, both with √sNN = 200 GeV. We will present the differential measurement on high momentum particles, and progress towards the nuclear modification factor. These two datasets combined will provide a large coverage of number of participants ( ⟨Npart⟩ ) from a few to a couple hundred, and give us an unique opportunity to explore how properties of hard scattering productions vary with system size. Combining with existing Au+Au measurements, we discuss a possible search for the critical system size above which QGP production is turned on. We will also further explore effects of different overlap geometry where ( ⟨Npart⟩ ) of Au+Au and isobar collisions overlap.

4)
Submitter : Monika Robotkova (NPI)
Title: Experimental measurements of the parton shower in p+p collisions at RHIC 
Abstract: Jets are collimated sprays of hadrons and serve as an experimental tool for studying the dynamics of quarks and gluons described by perturbative quantum  chromodynamics. Differential measurements of jet structure enable a systematic exploration of the parton shower evolution and aid in isolating specific jet topologies. The SoftDrop grooming technique utilizes the angular ordered Cambridge/Aachen reclustering tree and provides a correspondence between the experimental observables such as the shared momentum fraction (zg ), groomed radius (Rg ) and the QCD splitting functions in pp collisions. We present the first fully corrected multi-differential measurements of correlation between jet sub-structure observables zg vs. Rg at the first split for jets of varying momenta and radii at RHIC energies. To study the evolution we present the splitting observables zg and Rg  for the first, second and third splits as we travel along the jet shower for various jet and initiator prong momenta. As these splittings follow a natural time evolution axis, we introduce the formation time (τf [fm/c]) at the first splits and compare it to the formation time of the two highest energy charged particles in the jet. By comparing the different formation times across the splittings, we qualitatively explore the transition between perturbative (pQCD) and non-perturbative (npQCD) physics including hadronization within the the parton fragmentation. We compare our measurements to the various Monte Carlo models and discuss the impact of variations in parton shower (perturbative) and hadronization/underlying-event (non-perturbative) modeling on sub-structure measurements.

5)
Submitter: Gabriel Dale-Gau (UIC)
Title: Baryon to Meson Ratios in Au+Au collisions at sqrts-nn = 200 GeV 
Abstract: Experimental measurements at RHIC and LHC show strongly enhanced relative baryon to meson production at intermediate transverse momenta in high-energy nuclear collisions compared to pp baseline. This enhancement is attributed to QGP phenomena: strong hydrodynamic flow and contributions from parton recombination to particle production. Jet probes have been used successfully to gain further insights into QGP properties, with substantial modifications to jet yields and internal structures seen across multiple measurements. Despite apparent medium-induced changes to jet fragmentation patterns, LHC results indicate that in-jet particle production is significantly different from that of the QGP bulk. We present the first in-cone baryon to meson ratios associated with fully reconstructed jets from 200 GeV AuAu collisions using the STAR detector at RHIC. The observed proton to pion ratio related in charged particle jets is found to be substantially below previously reported inclusive event ratios, indicating little influence of possible shower-thermal recombination to jet parton hadronization.

6)
Submitter: Isaac Mooney (WSU)
Title: Jet substructure in p+p and p+Au collisions at sqrts-nn = 200 GeV at STAR 
Abstract: In order to attribute the partonic energy loss within jets (jet quenching) observed in A+A collisions to the traversal of partons through the hot QCD medium, it is necessary to examine cold nuclear matter (CNM) effects on the corresponding jets. Such examination has historically been done using p+A collisions. In this talk, we present fully corrected measurements of jet substructure and SoftDrop groomed jet substructure in p+A collisions at STAR at sNN = 200 GeV as a function of the event activity (EA) to increase or decrease the magnitude of CNM effects. EA is determined in backward (Au-going) rapidity (3.3 < |η| < 5.0) by the STAR Beam-Beam Counter detector to minimize auto-correlation effects of jet measurements at mid-rapidity. Finally, we compare the results in p+A collisions to fully corrected corresponding measurements in p+p collisions and current vacuum Monte Carlo models, as well as a heavy-ion Monte Carlo model given by PYTHIA-8 Angantyr, to isolate these CNM effects in anticipation of an upcoming jet mass measurement in A+A collisions.

7)
Submitter : Diptanil Roy (RU) and Matthew Kelsey (WSU)
Title: An Investigation of Charm Quark Jet Spectra and Shape Modifications in Au+Au Collisions at sqrts-nn = 200 GeV 
Abstract: Partons (quarks/gluons) interact strongly with the QGP, and hence have their energy and shower structure modified compared to those in vacuum, e.g., those produced in proton-proton collisions. Theoretical calculations also predict that radiative energy loss, which is the dominant mode of energy loss for gluons and light quarks in the QGP, is suppressed for  heavy quarks (such as charm and bottom) at low transverse momenta (pT). A measurement of the D0(cu ̄) meson radial profile in jets from the CMS experiment hints at a low pT modification in the medium at LHC energies, that is qualitatively different from that of the light flavor hadrons. The precise tracking by the Heavy Flavor Tracker detector in the STAR experiment at RHIC enables a low background and high statistics sample of D0 mesons, especially at low pT, making STAR ideal for similar measurements. We will report the first measurements of the D0-meson tagged pT,jet spectra and D0 meson radial profile in anti-kT jets from Au+Au collisions at √sNN = 200 GeV at RHIC, collected by the STAR experiment in 2014, and comparisons to PYTHIA-8 predictions at √s = 200 GeV. We will also report the nuclear modification factor RCP for these D0-meson tagged jets. Such measurements are expected to shed light on parton flavor and mass dependencies of jet quenching, and constrain theoretical models.

8)
Submitter : Diptanil Roy (RU) and Matthew Kelsey (WSU)
Title: Measurements of D0-tagged jet spectra and radial profiles in Au+Au collisions from STAR
Abstract: Measurements of hard probes such as jets and heavy flavor hadrons are essential to study the microscopic properties of the Quark-Gluon Plasma. In particular, due to their large intrinsic mass, measurements involving heavy flavor quarks are important to understand the parton mass effects of jet quenching. With the Heavy Flavor Tracker at STAR, the opportunity to use fully reconstructed D mesons to tag a clean and large sample of charm jets is enabled as combinatorial backgrounds can be removed by requiring a secondary D meson decay vertex. In this poster we present the details of the first measurements of D0-tagged jet spectra and radial profiles in Au+Au collisions at √s = 200 GeV, where we introduce a new method of simultaneously subtracting the residual D0-jet combinatorial background and applying efficiencies corrections using the sPlot method. We also explore a method to correct for detector inefficiencies and the underlying event without simulating the full heavy-ion event. We additionally show the central-to-peripheral nuclear modification factors RCP as a function of D0-jet transverse momentum. Finally, we compare our data to measurements from the Large Hadron Collider, and PYTHIA 8 simulations and various heavy quark transport models.

9)
Submitter : Raghav Kunnawalkam Elayavalli (Yale/BNL)
Title: Exploring jet topological dependence on parton energy loss in Au+Au collisions at sqrts=200 GeV at RHIC 
Abstract: Jets are algorithmic proxies of hard scattered quarks/gluons that are created in collisions of high energy particles. The last few years has seen an explosion of jet substructure results from all experiments derived from exploiting clustering algorithms. Jet quenching via parton energy loss in heavy ion collisions is an established technique for exploring the quark-gluon plasma’s transport properties. Since jets are multi-scale objects, there is a need to characterize the different methods of  medium interaction leading to energy loss for jets of varying shower topologies. In this talk, we tag specific jet populations based on jet substructure observables such as the opening angle and the jet splitting formation time calculated using the leading and subleading subjets and charged particles within the jet. These observables are shown to be experimentally robust to the heavy ion underlying event. With the large 2014 Au+Au data sample at $\sqrt{s_{NN}} = 200$ GeV collected in STAR, we measure the specially tagged jet populations within central collisions and compare the recoil jet momenta to study the transition between coherent or decoherent model of energy loss at a particular medium resolution length. Such measurements point towards isolating differences in energy loss signature for the first time via the formation times, translating to a path length and opening angle, translating to a resolution scale in the medium. 

10)
Submitter : Veronica Verkwest (WSU) and David Stewart (Yale/WSU)
Title: Correlations of mid-rapidity underlying event activity with jet kinematics and Au-going event activity in high-$p_\mathrm{T}$ jet events in $\sqrt{s_\mathrm{NN}}=\unit[200]{GeV}$  $p$+Au collisions at STAR. 

Abstract: Proton-gold collisions at $\sqrt{s_{\mathrm{NN}}}=\unit[200]{GeV}$ at STAR confirm significant correlations between high-transverse momentum ($p_{\mathrm{T}}$) parton scatterings and event activity (EA) measured at high-backward (Au-going) rapidity. These findings are in qualitative agreement with the observation by ATLAS that the centrality dependence of jet nuclear modification factors in $p$+Pb collisions appears to be a function of $x_\mathrm{p}$ (the longitudinal momentum fraction of the leading parton in the originating proton).  Within precision of measurements, the correlations at STAR are found to not result from jet quenching in a Quark Gluon Plamsa; as such, they provide an opportunity to probe the early initial stages of the collisions and/or long-range cold nuclear matter (CNM) effects. Accordingly, we present measurements of mid-rapidity underlying event (UE), and their trends relative to EA and jet kinematics ($p_\mathrm{T}$ and pseudorapidity) in high-$p_\mathrm{T}$ jet events. 

11)
Submitter : Robert Licenik (NPI)
Title: Measurement of the inclusive production of fully-reconstructed jets in Au+Au collisions at sqrts-nn = 200 GeV by the STAR experiment 
Abstract: The STAR Collaboration at RHIC reports the first measurement of the incluive distribution of fully-reconstructed jets in in central (0-10%) and peripheral (60-80%) Au+Au collisions at √sNN = 200 GeV. The dataset, with integrated luminosity 5.2 nb−1, was recorded during the 2014 RHIC Au+Au run utilizing trigger based on a high-ET cluster in the Barrel Electromagnetic Calorimeter (BEMC). Jets are reconstructed from charged-particle tracks and neutral energy clusters using the anti-kT algorithm with R = 0.2, 0.3 and 0.4. The large jet background yield in heavy ion collisions is suppressed by requiring a high-pT leading charged track or neutral BEMC cluster in accepted jet candidates. The bias imposed by this requirement is assessed, and the pT-region in which the bias is negligible is identified. Inclusive jet distributions are reported for pjet > 10 GeV/c. Yield suppression, which arises from medium-induced partonic energy loss, is observed for central Au+Au collisions relative to both peripheral Au+Au collisions and a vacuum reference measured in p+p collisions. Medium-induced jet broadening is measured using the R-dependence of jet yields. The results are compared to other jet measurements at RHIC and the LHC, and to theoretical calculations.

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