Conveners
Jet modifications and high-pT hadrons: I
- Xin-Nian Wang (Central China Normal University (China)) / Lawrence Berkeley Na)
Jet modifications and high-pT hadrons: II
- Carlos Albert Salgado Lopez (Universidade de Santiago de Compostela (ES))
Jet modifications and high-pT hadrons: III
- Gunther Roland (MIT)
Jet modifications and high-pT hadrons: IV
- Leticia Cunqueiro Mendez (Oak Ridge National Laboratory - (US))
Jet modifications and high-pT hadrons: V
- Julia Velkovska (Vanderbilt University (US))
We report recent ALICE results on primary charged particle and neutral meson production in pp (2.76, 5.02, 7 and 8 TeV), p-Pb (5.02 TeV), Pb-Pb (2.76 and 5.02 TeV) and Xe-Xe (5.44 TeV) collisions. The transverse momentum ($p_{\rm T}$) spectra of charged hadrons used in the analysis were measured in the kinematic range of $0.15 < p_{\rm T} < 50$ GeV/$c$ and $ |\eta|< 0.8$. The charged hadron...
The spectra of charged particles in XeXe and PbPb collisions at $\sqrt{s_{NN}} = 5.44$ TeV and $\sqrt{s_{NN}} = 5.02$ TeV, respectively, are presented in six ranges of collision centrality. The PbPb nuclear modification factor is constructed with a measured pp reference, and the XeXe nuclear modification factor is formed with an extrapolated pp reference. Both are found to be heavily...
The measurement of charge particle production in heavy ion collisions, when compared with $pp$ data, provides insight into the properties of the hot and dense quark-gluon plasma. The ATLAS detector at the LHC recorded 0.49 nb$^{-1}$ of Pb+Pb collisions, 25 nb$^{-1}$ of $p$+Pb collisions and 4.2 pb$^{-1}$ of $pp$ collisions, all at the center-of-mass energy $\sqrt{s_{NN}}=\sqrt{s}=5.02$ TeV....
Recent measurements of hadron and jet RAA at very high energies provide in combination crucial new input to our understanding of jet quenching. The increased precision of these observables has shown how hadrons and jets with comparable energies are suppressed differently. This is natural, since triggering on a high energy hadron constitutes selecting an unusual jet whose fragmentation pattern...
We present charged particle spectra at midrapidity measured in lead-lead collisions at a center-of-mass energy per nucleon pair of 5.02 TeV with ALICE, in twenty centrality classes ranging from most central (0-5%) to very peripheral (95-100%) collisions. At high transverse momentum ($8 < p_{\rm T} <30$ GeV/$c$), the average nuclear modification factor ($R_{\rm AA}$) is found to increase from...
The measurement of D-meson production in jets can provide important insights into the interactions of heavy-flavour quarks with the quark-gluon plasma created in heavy ion collisions. In particular, the role of gluon splitting processes in the production of heavy flavour, which is fundamental for a complete understanding of the quenching mechanisms for both light and heavy quarks, can be...
Heavy quarks (charm and beauty) are produced in hard parton scatterings in the early stages of hadronic collisions. Therefore, they are ideal probes to investigate the properties of the Quark-Gluon Plasma (QGP) produced in ultra-relativistic heavy-ion collisions. The study of angular correlations between heavy-flavour particles and charged particles allows us to characterize the heavy-quark...
The nuclear modification of groomed jet splitting in relativistic heavy-ion collisions at RHIC and the LHC energies is studied [1] based on the higher twist formalism. Assuming coherent energy loss for the two splitted subjets, a non-monotonic jet energy dependence is found for the nuclear modification of jet splitting function: strongest modification at intermediate jet energies whereas...
Hard splittings in the evolution of a jet may be modified by the presence of a dense strongly interacting medium. Grooming procedures can be used to isolate such hard components of a jet and allows one to focus on the two subjets resulting from a sufficiently hard partonic splitting. The modification of these splittings in medium could highlight the role of jet induced medium response as well...
Nearly collinear pairs of partons are sensitive to potential novel coherence effects in the parton energy loss process, which can be observed through measurements of jet substructure. This analysis presents a new measurement of jets containing a gluon that splits into a heavy quark pair, i.e., a heavy-quark antenna. Such jets are identified by analyzing the groomed substructure of double...
Correlations of electroweak probes, jets, and charged particles are a powerful tool to study medium modifications of the parton shower. One can impose constraints on jet quenching mechanisms in heavy ion collisions by measuring jet substructure observables, such as fragmentation functions or jet momentum density profiles. Tagging jets with an associated photon helps to constrain the associated...
As a colorless probe, direct photons balance the $p_T$ of the away-side jet at
leading order. Direct photon-hadron correlations are thus an excellent probe for
nuclear structure and QCD effects, including parton energy loss in the
Quark-Gluon Plasma.
PHENIX has measured $\pi^0$ and direct photon-triggered two-particle azimuthal
correlations in a variety of collision systems ranging from...
Events containing a high transverse momentum ($p_\mathrm{T}$) prompt photon offer a useful tool to study the dynamics of the hot, dense medium produced in heavy ion collisions. Because photons do not carry color charge, they are unaffected by the medium, and thus provide information about the momentum, direction, and flavor (quark or gluon) of the associated hard-scattered parton before it...
Gauge boson tagged jet production has long be regarded as a "golden channel" to study the jet quenching effect. Recently, the back-to-back azimuthal alignment $\Delta\phi_{jZ}$, $p_T$ asymmetry $x_{jZ}$ distribution and its mean value, as well as the average number of jet partners per Z boson $R_{jZ}$ of Z associated jet production have been reported in both pp and Pb-Pb collisions by CMS....
Measurements of isolated prompt photon and massive electroweak (W and Z) boson production in different collision systems are of great interest to understanding the partonic structure of heavy nuclei, and serve as a constraint on the initial state in larger collision systems. These channels are sensitive to a variety of effects such as the modification of the parton densities in nuclei in...
Recent STAR's jet physics results in heavy-ion collisions will be reported in this talk. Coincidence measurements of semi-inclusive jets recoiling from high-$p_T$ hadrons or direct photons will be presented to offer constraints on path length and flavor dependence of energy loss. Di-jets selected with a constituent cut of 2 GeV/$c$ showed significant transverse momentum imbalance which could...
A high energy parton is known to lose energy when passing through the hot and dense medium produced in heavy ion collisions. This results in the modification of jet yields and fragmentation patterns. The latest measurements of the nuclear modification factor, $R_{AA}$, for $R=0.4$ jets in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV with the ATLAS detector at the LHC are...
The Jet Energy-loss Tomography with a Statistically and Computationally Advanced Program Envelope (JETSCAPE) Collaboration is developing an innovative modular event generator to be used by the wider community. In this talk we highlight the performance of the year-1 release of the JETSCAPE software, which consists of an overall framework program, and of several physics modules. The framework...
Inclusive jet spectra in PbPb and pp collisions at 5.02 TeV are measured in data collected by the CMS detector at the LHC during Run 2 in 2015. The measurement is performed for jet transverse momentum greater than 200 GeV/c and a pseudorapidity window of $|\eta|<2$. The jet nuclear modification factor is extracted for various collision centrality selections to study the impact of jet quenching...
We introduce a novel jet quenching study approach by the classification of quark-initiated jets and gluon-initiated jets in proton-proton and heavy ion collisions using modern machine learning techniques. We train a deep convolutional neutral network on jet images. The classification performance is compared with the multivariate analysis of several physically-constructed jet observables...
Highly energetic jets produced in ultra-relativistic nuclear collisions are considered to be direct probes to study the properties of the hot and dense QCD matter created in these collisions. The measurement of the fragmentation functions of jets into charged particles in Pb+Pb collisions is sensitive to the strength and mechanism of jet quenching. In this talk, we present the latest...
It is well known that the multiple interactions of a hard probe with a dense quark-gluon plasma result in the "medium-induced" radiation of soft gluons, responsible e.g. for jet energy loss. Such an emission can be computed using the BDMPS-Z formalism, which has recently been generalised to include multiple medium-induced emissions. To get a complete picture of the evolution of a jet in a...
Dijet azimuthal acoplanarity is dominated by vacuum pQCD radiation always associated with hard jet production. Jet-medium interactions broaden the vacuum Sudakov azimuthal angle distributions. In the Gaussian approximation (A.H.Mueller et al 2016) the broadening rms $\Delta\phi_{G} \sim \sqrt{<\hat{q}(T,E) L>}/E$ depends only on the jet path $L$ averaged transport coefficient $\hat{q}$. We...
We present recent results on measurements of jet substructures using grooming techniques with pp and PbPb data collected with the CMS detector at a center-of-mass energy of 5.02 TeV per nucleon pair. Jet grooming techniques are used to focus on the hard structure of the jet by extracting the two subjets corresponding to the hardest parton splitting. This allows to study the properties of...
The striking suppression and modification patterns that are observed in jet observables measured in heavy-ion collisions, with respect to the proton-proton baseline, have the potential to constrain the spatio-temporal branching process of energetic partons in a dense QCD medium. The mechanism of jet energy loss in a deconfined medium is intricately associated with medium resolution of jet...
A consistent description of high pT particle suppression ($R_{AA}$) and azimuthal anisotropy $v_2$ has been a puzzle in the study of jet quenching, pointing to some non-perturbative native of jet transport. Event-by-event single inclusive jet suppression and azimuthal anisotropy are studied within the Linear Boltzmann Transport (LBT) model for jet propagation in QGP medium from 3+1D...
Jets, defined as collimated sprays of particles originating from initial hard scattered partons, serve as well calibrated probes of the Quark-Gluon Plasma formed in high-energy nuclear collisions. Their production cross section and geometrical profile in elementary pp collisions is precisely calculable within the framework of perturbative QCD (pQCD). Hence, any modification of its production...
In this talk, we present the MARTINI study of the modification of jet shapes in quark-gluon plasma. The focus of this study is the effect of medium response on the jet shape function in PbPb collisions at $\sqrt{s}$ = 2.76 and 5.02TeV. As a jet parton propagates, the medium must respond to the energy and momentum
deposited by the jet parton. The medium response thus re-distributes the lost...
