Medium response in JEWEL and its impact on jet shape observables in heavy ion collisions

Elayavalli, R. Kunnawalkam; Zapp, Korinna

doi:10.1007/jhep07(2017)141

Cited by 119 publications

(98 citation statements)

References 49 publications

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“…The enhancement at large ξ jet and ξ γ T , together with the suppression at lower values, indicates that the showers of partons that emerge from the medium contain more lower-energy particles in PbPb collisions. These particles can originate directly from high energy partons that lose energy, as well as from the medium response, the recoil of the medium as the parton traverses through [34,53,54]. The enhancements and suppressions of the fragmentation patterns measured using a photon to estimate the initial parton energy (ξ γ T ) are observed to be more pronounced than the ones measured using detector level jet energy (ξ jet ).…”

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confidence: 98%

Observation of Medium-Induced Modifications of Jet Fragmentation in Pb-Pb Collisions at sNN=5.02 TeV Using Isolated Photon-Tagged Jets

Sirunyan¹,

Tumasyan²,

Adam³

et al. 2018

Phys. Rev. Lett.

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Measurements of fragmentation functions for jets associated with an isolated photon are presented for the first time in pp and PbPb collisions. The analysis uses data collected with the CMS detector at the CERN LHC at a nucleon-nucleon center-ofmass energy of 5.02 TeV. Fragmentation functions are obtained for jets with p jet T > 30 GeV/c in events containing an isolated photon with p γ T > 60 GeV/c, using charged tracks with transverse momentum p trk T > 1 GeV/c in a cone around the jet axis. The association with an isolated photon constrains the initial p T and azimuthal angle of the parton whose shower produced the jet. For central PbPb collisions, modifications of the jet fragmentation functions are observed when compared to those measured in pp collisions, while no significant differences are found in the 50% most peripheral collisions. Jets in central PbPb events show an excess (depletion) of low (high) p T particles, with a transition around 3 GeV/c. This measurement shows for the first time the in-medium shower modifications of partons (quark dominated) with well defined initial kinematics. It constitutes a new well-controlled reference for testing theoretical models of the parton passage through the QGP. the pseudorapidity coverage up to |η| = 5.2. In the case of PbPb events, the HF signals are used to determine the degree of overlap ("centrality") of the two colliding Pb nuclei [21] and the event-by-event azimuthal angle of maximum particle density ("event plane") [35]. A more detailed description of the CMS detector can be found in Ref. [36].The event samples are selected online with a dedicated photon trigger requiring one photon with p γ T > 40 GeV/c [29], and are subjected to offline requirements to remove non-collision events [29,37]. For jets and photons, the reconstruction algorithms, analysis selections, and corrections for the energy scale and resolution are the same as in Ref. [29]. For the analysis of PbPb collisions, the event centrality is defined as the fraction of the total inelastic hadronic cross section, starting at 0% for the most central collisions, and is evaluated as percentiles of the distribution of the energy deposited in the HF calorimeters [21]. Results are presented in four centrality intervals, ranging from a central 0-10% (i.e., the 10% of the events having the largest overlap area of the two nuclei [38]), to a peripheral 50-100% (the one closest to a pp-like environment) intervals.The photon candidates are restricted to the barrel region of the ECAL, |η γ | < 1.44, and are required to have p γ T > 60 GeV/c. Electron contamination and anomalous signals caused by the interaction of heavily ionizing particles with the silicon avalanche photodiodes used for the ECAL readout are removed [39]. Background from ECAL showers induced by hadrons are rejected using the ratio of HCAL over ECAL energy inside a cone of radius ∆R = √ (∆η) 2 + (∆φ) 2 = 0.15 around the photon candidate [39,40]. Background contributions from fragmentation and decay photons are rejected by imposing isolation ...

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confidence: 98%

Observation of Medium-Induced Modifications of Jet Fragmentation in Pb-Pb Collisions at sNN=5.02 TeV Using Isolated Photon-Tagged Jets

Sirunyan¹,

Tumasyan²,

Adam³

et al. 2018

Phys. Rev. Lett.

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“…This simultaneous description is even more challenging if the jet mass is also considered. Figure 3: Jet Radial profile as given by Coupled Jet-Fluid [12] (upper, left), Hybrid [15] (upper, right), MARTINI [9] (lower, left) and JEWEL [7] (lower, right). The CMS data [32] are also represented as circles in each plot.…”

Section: Monte Carlo Results -Data Comparisonmentioning

confidence: 99%

Jets in QCD matter: Monte Carlo approaches

Apolinário¹

2019

Proceedings of International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions — PoS(HardProbes20

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Monte Carlo approaches are a powerful tool in collider physics as they allow to make theory-data comparison on complex multi-particle observables, otherwise difficult for perturbative calculations. In heavy-ion collisions, there is a multitude of Monte Carlo approaches that try to address jet quenching phenomena, name given to the collection of medium-induced modifications that high momentum particles and jets undergo when traversing the hot and dense medium that is produced in such collisions. These models are being continuous developed alongside the theoretical efforts to understand and accurately describe experimental results provided by both RHIC and the LHC. In this manuscript, it is given a general overview about the fundamental building blocks that these tools have to address to describe jets in heavy-ion collisions. It follows a comparison on the latest results provided by some of the jet quenching Monte Carlo models to jet and intra-jet observables. A final outlook is presented at the end of the manuscript.

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“…[26][27][28][29]. In the case of a Monte Carlo calculation in which hard two-to-two scattering is already included, for example those done within JEWEL [30][31][32][33][34][35], MARTINI [36] or LBT [37][38][39], our results can be used in a different way, namely as a benchmark against which to compare for the purpose of identifying observable consequences of large-angle scattering. The other way in which the results of our calculation will be of value is as a qualitative guide to experimentalists with which to assess how large the effects of interest may turn out to be, namely as a qualitative guide to what the probability is that a parton with a given energy in a jet could scatter by an angle θ.…”

Section: Contentsmentioning

confidence: 99%

“…There are many extant measurements of the modification of jet shape observables in heavy ion collisions [18,19,21,23,25,[41][42][43][44][45], and many theorists have made efforts to turn these measurements into constraints on transverse momentum broadening, for example see Refs. [28,35,37,[46][47][48][49][50], but there are two significant confounding effects that obscure transverse momentum broadening [28]. The first effect is that the energy and momentum "lost" by the jet becomes a wake in the plasma which then in turn becomes soft particles spread over a large range of angles around the jet direction, carrying momentum in the jet direction.…”

Section: Contentsmentioning

confidence: 99%

Molière scattering in quark-gluon plasma: finding point-like scatterers in a liquid

DʼEramo

Rajagopal

Yin

2019

J. High Energ. Phys.

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By finding rare (but not exponentially rare) large-angle deflections of partons within a jet produced in a heavy ion collision, or of such a jet itself, experimentalists can find the weakly coupled short-distance quark and gluon particles (scatterers) within the strongly coupled liquid quark-gluon plasma (QGP) produced in heavy ion collisions. This is the closest one can come to probing QGP via a scattering experiment and hence is the best available path toward learning how a strongly coupled liquid emerges from an asymptotically free gauge theory. The short-distance, particulate, structure of liquid QGP can be revealed in events in which a jet parton resolves, and scatters off, a parton from the droplet of QGP. The probability for picking up significant transverse momentum via a single scattering was calculated previously, but only in the limit of infinite parton energy which means zero angle scattering. Here, we provide a leading order perturbative QCD calculation of the Molière scattering probability for incident partons with finite energy, scattering at a large angle. We set up a thought experiment in which an incident parton with a finite energy scatters off a parton constituent within a "brick" of QGP, which we treat as if it were weakly coupled, as appropriate for scattering with large momentum transfer, and compute the probability for a parton to show up at a nonzero angle with some energy. We include all relevant channels, including those in which the parton that shows up at a large angle was kicked out of the medium as well as the Rutherford-like channel in which what is seen is the scattered incident parton. The results that we obtain will serve as inputs to future jet Monte Carlo calculations and can provide qualitative guidance for how to use future precise, high statistics, suitably differential measurements of jet modification in heavy ion collisions to find the scatterers within the QGP liquid.

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Medium response in JEWEL and its impact on jet shape observables in heavy ion collisions

Cited by 119 publications

References 49 publications

Observation of Medium-Induced Modifications of Jet Fragmentation in Pb-Pb Collisions at sNN=5.02 TeV Using Isolated Photon-Tagged Jets

Observation of Medium-Induced Modifications of Jet Fragmentation in Pb-Pb Collisions at sNN=5.02 TeV Using Isolated Photon-Tagged Jets

Jets in QCD matter: Monte Carlo approaches

Molière scattering in quark-gluon plasma: finding point-like scatterers in a liquid

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