Conveners
Parallel: A1 - Jets and High-PT Hadrons I
- Carlos Albert Salgado Lopez (Universidade de Santiago de Compostela (ES))
Parallel: B1 - Jets and High-PT Hadrons II
- Peter Martin Jacobs (Lawrence Berkeley National Lab. (US))
Parallel: C1 - Jets and High-PT Hadrons III
- Andreas Morsch (CERN)
Parallel: D1 - Jets and High-PT Hadrons IV
- Leticia Cunqueiro Mendez (Oak Ridge National Laboratory - (US))
Parallel: E1 - Jets and High-PT Hadrons V
- Yen-Jie Lee (Massachusetts Inst. of Technology (US))
Parallel: F1 - Jets and High-PT Hadrons VII
- Helen Caines (Yale University (US))
Parallel: G1 - Jets and High-PT Hadrons IX
- Christine Nattrass (University of Tennessee (US))
Parallel: H1 - Jets and High-PT Hadrons XI
- Gunther Roland (Massachusetts Inst. of Technology (US))
Description
P2
High energy partons are known to lose energy when passing through the hot and dense medium produced in heavy-ion collision. This results in a modification to the transverse momentum distributions of both charged hadrons and jets. It has been previously shown in Pb+Pb collisions at $\sqrt{s_{NN}} = 2.76$~TeV that parton energy loss within the Quark Gluon Plasma results in significant...
The STAR Collaboration at RHIC reports the measurements of both charged and fully-reconstructed inclusive jet production in central (0-10\%) and peripheral (60-80\%) Au+Au collisions at $\sqrt{s_{\scriptsize{\textrm{NN}}}}$ = 200 GeV. The charged jet analysis utilizes a dataset corresponding to 70 $\mu\mathrm{b}^{-1}$ recorded in 2011, while the new fully-reconstructed jet analysis utilizes a...
We study the fragmentation of an energetic jet propagating through a
dense quark-gluon plasma within perturbative QCD. We use a recently developed factorisation scheme (and the associated Monte-Carlo generator), in which the standard vacuum-like parton branchings are factorised in time from the medium-induced emissions triggered by multiple soft scattering in the medium. Besides the...
New measurements of jet quenching observables at RHIC and at the LHC, such as jet substructure observables, demand an increased precision in the theory calculations describing medium-induced radiation of gluons. Closed expressions for the gluon spectrum including a full resummation of multiple scatterings have been known for the past 20 years, but have only been evaluated in specific limits...
Partons are colored probes that interact with the quark-gluon plasma (QGP). By studying jets, the observable final state product of partons, we can improve our understanding of the interaction mechanism between partons and the QGP. Jet nuclear modification factor (RAA) is a simple yet profound observable that measures the amount of suppression with respect to a reference of proton-proton...
We present the semi-inclusive distribution of charged jets recoiling from a trigger hadron in pp and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV. This technique provides a precise data-driven subtraction of the large uncorrelated background contaminating the measurement. It uniquely enables the exploration of medium-induced modification of jet production and acoplanarity over a...
Heavy ion collisions at high energies can be used as an interesting way to recreate and study the medium of the quark-gluon plasma (QGP). We particularly investigate the jets produced in hard binary collisions and their interactions with a tentative medium. These jets were obtained numerically from the Monte-Carlo simulations of hard collisions using the KATIE-framework [1], where...
We present a study of the impact of the expansion of deconfined medium on single-gluon emission spectra and the jet suppression factor ($Q_{AA}$) within the BDMPS-Z formalism. These quantities are calculated for three types of media (static medium, exponentially decaying medium and Bjorken expanding medium). The distribution of medium-induced gluons and the jet $Q_{AA}$ are calculated using...
The evolution of QCD jets under the influence of a dense colored medium leads to the non trivial modification of the emission spectrum. In the multiple soft scattering regime, for sufficiently large mediums, soft and wide angle emissions can be resummed, at large number of colors, since the emissions become independent up to $\tau_{br}/L$ corrections. Similarly to DGLAP evolution, such...
We study the nuclear modification for the dijet cross section in eA deeply inelastic scattering (DIS) process. This nuclear modification comes from multiple scattering of final state parton in a large nucleus, including medium induced radiation. This extra modification to dijet cross section depends on transverse momentum dependent (TMD) quark-gluon correlation function, which can be...
Jets recoiling from a direct photon are seen as a relatively clean probe, due to the more tightly constrained initial hard scattering kinematics compared to di-jet measurements. In this talk, we will present semi-inclusive measurements of jets recoiling from direct-photon and $\pi^0$ triggers in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV, both their yield and the transverse momentum...
In addition to the previously reported inclusive jet spectra and nuclear
modification factors in $d$+Au, and Cu+Au collisions at $\sqrt{s_{NN}}$ =
200 GeV at mid-rapidity, measurements of jets in p+A and jet substructure in
p+p and Cu+Au have also been performed in PHENIX. Jets are reconstructed
from charged particle tracks and electromagnetic calorimeter clusters with
the anti-kT...
The collective effects in high-multiplicity proton-proton, proton-nucleon and nucleon-nucleon collisions have not yet been attributed to a common mechanism. Within the Lund string model of partons, the interaction force between strings (aka. string shoving) could be responsible for such effects. So far, this aspect has only been present for pp in the existing PYTHIA8 framework, but after the...
Measurements of the jet spectra and nuclear modification factors for inclusive charged jets and inclusive full jets (containing both charged and neutral constituents) in Pb-Pb and pp collisions at $\sqrt{s_{NN}} = 5.02$ TeV recorded with the ALICE detector will be shown. These measurements use a novel machine learning based background correction [1] which reduces residual fluctuations. The...
Recently, jet substructure observables have been widely used in the study of jets. Some observables are sensitive to the wide angle soft particles within the jet, for example, the Lund plane distribution with different jet radii and soft drop parameters. As the jet loses energy and momentum during its evolution inside the quark-gluon plasma (QGP), the “lost" energy and momentum is deposited in...
We investigate the medium induced fragmentation of jets in a high-temperature QCD plasma. Based on an effective kinetic theory of QCD, we study the non-equilibrium evolution of the jet shower and the chemical equilibration of jet fragments in the medium. By including radiative emissions as well as the elastic interactions evolution, our approach extends all the way from the jet energy scale...
Jet quenching has become a fundamental tool to study
the hot QCD matter produced in heavy ion collisions. While
important theoretical and experimental advances have been made in the last two decades, the extraction of the medium properties
and the comparison with finite temperature QCD is still particularly worrisome.
In this work we show that improvements in the calculation of the...
High energy partons has been a useful tool to study the hot and dense matter produced in heavy-ion collisions. To this end, it has been shown that is important to incorporate the most realistic description of the Quark Gluon Plasma using relativistic hydrodynamics in order to study many properties at high pT. Therefore, in this work we couple a modified JEWEL code to event-by-event...
Measurement of jet structure in heavy-ion collisions allows studying properties of the hot and dense QCD medium created in these collisions and the mechanism of the jet quenching. This talk presents the latest ATLAS measurements of the internal structure of jets to better constrain the modifications of the parton showering process. A new measurement of how the suppression of large-radius jets...
We report new jet substructure measurements in Pb-Pb and pp collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ALICE detector. For the first time, fully corrected measurements of the groomed jet momentum fraction, $z_g$, the groomed jet radius, $\theta_g \equiv R_g/R$, and the number of Soft Drop splittings, $n_{\mathrm{SD}}$, will be shown in Pb-Pb collisions, along with their ratio to...
Jet substructure represents a cornerstone in the on-going endeavor to pinpoint the effect of a hot, thermal medium, namely the QGP, on QCD dynamics. In this talk, based on [1], I will present a new set of jet substructure observables and an associated grooming technique, dubbed "dynamical grooming". This procedure is rooted on identifying the hardest splitting in an angular ordered shower and...
With our coupled jet-fluid model [1, 2, 3], we study the nuclear modifications of full jets and jet structures for single inclusive jets and $\gamma$-jets in Pb+Pb collisions at $5.02$ ATeV and $2.76$ ATeV. The in-medium evolution of full jet shower is described by a set of coupled transport equations including the effects of collisional energy loss, transverse momentum broadening and...
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 - with a...
Due to recent advances in jet finding techniques and larger data samples, measurements of inclusive or recoil jets with large resolution parameters are now experimentally accessible via semi-inclusive hadron-jet or machine learning techniques, the latter of which enables the measurement of charged jet spectra down to low jet transverse momentum for jet resolution parameters up to $R=0.6$. By...
The angular dependence of jet suppression encodes key information about the process of energy and momentum hydrodynamization, and for this reason can be used to greatly improve our understanding of fundamental aspects of the jet/QGP interaction. In this work we study jet suppression from small to very large radius, for low and very high energy jets at the LHC and RHIC. We use the hybrid...
A unified description of jet evolution through deconfined QCD matter remains one of the challenging problems in the area of heavy-ion physics. To gain a comprehensive understanding of the properties of the QGP, we need an energy-loss model that effectively captures the physics of multi-scale jet quenching and provides a simultaneous description of a wide variety of integrated and differential...
Quantifying the nuclear modification due to multiple scatterings between jet and nuclear medium can provide a solid baseline for the identification of the medium fundamental property, which can be partly encoded in the nonperturbative jet transport coefficient ($\hat q$). In this work, we perform the first global extraction of the $\hat q$ for cold nuclear matter within the framework of the...
It is believed that the properties of quark-gluon plasma (QGP) can be studied through measurements of the jet quenching phenomenon. More specifically, detailed studies of the jet substructure may reveal the microscopic properties of the QGP.
Recently the modification of groomed jet observables was studied in heavy-ion collisions [1][2]. In addition, the Lund radiation plane was introduced...
Jet quenching is a possible consequence of the formation of a quark-gluon plasma (QGP) in collision systems, but to date no significant jet quenching has been observed in small systems. In this talk, the ALICE Collaboration reports results of a novel approach to jet-quenching measurements in high-multiplicity pp collisions at √𝑠=13 TeV, searching for the broadening of the acoplanarity...
“Hybrid Hadronization” is a new Monte Carlo package to hadronize systems of partons. It smoothly combines quark recombination applicable when distances between partons in phase space are small, and string fragmentation appropriate for dilute parton systems, following the picture outlined by Han et al. [PRC 93, 045207 (2016)]. Hybrid Hadronization integrates with PYTHIA 8 and can be applied to...
In ultra-relativistic heavy-ion collisions, partons with intermediate energy (5-10) GeV excite ripples as they travel through the Quark-Gluon Plasma (QGP).
These ripples' effect on particle production phenomenology is not very well studied.
In this work, we extend our previous work \cite{Ryu:2018ckh} and present study using a state-of-the-art hybrid framework that consists of the IP-Glasma...
Away from the strictly soft and collinear limit of QCD radiation the choice of evolution scale in a parton shower algorithm is ambiguous and several options have been implemented in existing Monte Carlo event generators for proton-proton collisions [1]. However, the resulting space-time evolution could result in subtle differences depending on the particular choice. In this work we quantify...
Electroweak bosons can be used to constrain the kinematics, as well as the flavor, of the recoiling parton, before its interaction with the quark-gluon plasma. While photons are more abundant, they suffer from larger systematic uncertainties, particularly at low transverse momentum ($p_\mathrm{T}$), from the background photons from neutral meson decays. Tagging with Z bosons is a complementary...
Transverse momentum broadening and energy loss of a propagating parton are dictated by the space-time profile of the jet transport coefficient $\hat q$ in dense QCD medium. Spatial gradient of $\hat q$ perpendicular to the propagation direction can lead to a drift and asymmetry in parton transverse momentum distribution. Such an asymmetry depends on both the spatial position along the...
Jet anisotropy can provide insight into the path-length dependence of jet quenching and closely relate to the bulk anisotropy in high energy heavy-ion collisions. We show a weak dependence of colliding energy and jet $p_{T}$ for inclusive jet anisotropy $v^{2}_{jet}$ at different centrality classes within the linear Boltzmann jet transport model coupled with the dynamic evolution of the QGP...
Jets can be used to study in-medium modifications of the parton shower and the energy loss mechanisms in heavy-ion collisions. Several recent works have alluded to a modification in the fractions of quark and gluon jets in QGP due to color-charge dependent quenching. The jet charge is defined as the momentum-weighted sum of charges of particles inside a jet. The sensitivity of jet charge to...
Measurements of hard-scattered partons produced in conjunction with a high-pT photon or Z boson offer a discerning way to study the quark gluon plasma (QGP) created in ultrarelativistic nucleus-nucleus collisions. The high-pT boson tags the initial energy, direction, and flavor of the opposing parton or partons before they begin to shower and propagate through the QGP, offering a valuable...
The modification of jet substructure in heavy-ion collisions compared to that in the vacuum reference is one of the main features of jet quenching. Such modification has been observed at LHC kinematics with various observables, such as jet fragmentation and jet shapes. In this talk, we report measurements of the differential jet shape and semi-inclusive jet fragmentation functions in Au+Au...
