Jet quenching in heavy ion collisions and in particular the sub-structure of quenched jets are promising tools for investigating the microscopic processes underlying jet quenching and the background ...medium's response to energy and momentum depositions. A quantitative understanding of the data can, however, be complicated by the presence of initial state radiation in reconstructed jets. Using an extended version of Jewel the effect of initial state radiation on different jet observables is studied in proton-proton and heavy ion collisions. It is shown that, depending on the observable and the jet radius, the initial state contributions can be sizable. Some general insights into when sizable effects can be expected also emerges.
JEWEL 2.0.0: directions for use Zapp, Korinna
The European physical journal. C, Particles and fields,
02/2014, Volume:
74, Issue:
2
Journal Article
Peer reviewed
Open access
In this publication the first official release of the
Jewel 2.0.0
code The first version
Jewel 1
(Zapp et al. in Eur Phys J C 60:617,
2009
) could only treat elastic scattering explicitly and the ...code was never published, The code can be downloaded from the official
Jewel
homepage
http://jewel.hepforge.org
is presented.
Jewel
is a Monte Carlo event generator simulating QCD jet evolution in heavy-ion collisions. It treats the interplay of QCD radiation and re-scattering in a medium with fully microscopic dynamics in a consistent perturbative framework with minimal assumptions. After a qualitative introduction into the physics of
Jewel
detailed information about the practical aspects of using the code is given. The code is available from the official
Jewel
homepage
http://jewel.hepforge.org
.
In this publication the performance of the Monte Carlo event generator Jewel in non-central heavy-ion collisions is investigated. Jewel is a consistent perturbative framework for jet evolution in the ...presence of a dense medium. It yields a satisfactory description of a variety of jet observables in central collisions at the LHC, although so far with a simplistic model of the medium. Here, it is demonstrated that also jet measurements in non-central collisions, and in particular the dependence of the jet suppression on the angle relative to the reaction plane, are reproduced by the same model.
Time reclustering for jet quenching studies Apolinário, Liliana; Cordeiro, André; Zapp, Korinna
The European physical journal. C, Particles and fields,
06/2021, Volume:
81, Issue:
6
Journal Article
Peer reviewed
Open access
The physics program of ultra-relativistic heavy-ion collisions at the Large Hadron Collider (LHC) and Relativistic Heavy-Ion Collider (RHIC) has brought a unique insight into the hot and dense QCD ...matter created in such collisions, the Quark-Gluon Plasma (QGP). Jet quenching, a collection of medium-induced modifications of the jets’ internal structure that occur through their development in dense QCD matter, has a unique potential to assess the time structure of the produced medium. In this work, we perform an exploratory study to identify jet reclustering tools that can potentiate future QGP tomographic measurements with jets at current energies. Our results show that by using the inverse of formation time to obtain the jet clustering history, one can identify more accurately the time structure of QCD emissions inside jets, even in the presence of jet quenching.
A perturbative framework for jet quenching Zapp, Korinna C.; Krauss, Frank; Wiedemann, Urs A.
The journal of high energy physics,
03/2013, Volume:
2013, Issue:
3
Journal Article
Peer reviewed
Open access
A
bstract
We present a conceptually new framework for describing jet evolution in the dense medium produced in ultra-relativistic nucleus-nucleus collisions using perturbative QCD and its ...implementation into the Monte Carlo event generator Jewel. The rescattering of hard partons in the medium is modelled by infrared continued pQCD matrix elements supplemented with parton showers. The latter approximate higher order real-emission matrix elements and thus generate medium-induced gluon emissions. The interplay between different emissions is governed by their formation times. The destructive interference between subsequent scattering processes, the non-Abelian version of the Landau-Pomeranchuk-Migdal effect, is also taken into account. In this way the complete radiation pattern is consistently treated in a uniform way. Results obtained within this minimal and theoretically well constrained framework are compared with a variety of experimental data susceptible to jet-quenching effects at both RHIC and the LHC. Overall, a good agreement between data and simulation is found. This new framework also allows to identify and quantify the dominant uncertainties in the simulation, and we show some relevant examples for this.
Studies of fully-reconstructed jets in heavy-ion collisions aim at extracting thermodynamical and transport properties of hot and dense QCD matter. Recently, a plethora of new jet substructure ...observables have been theoretically and experimentally developed that provide novel precise insights on the modifications of the parton radiation pattern induced by a QCD medium. This report, summarizing the main lines of discussion at the 5th Heavy Ion Jet Workshop and CERN TH institute 'Novel tools and observables for jet physics in heavy-ion collisions' in 2017, presents a first attempt at outlining a strategy for isolating and identifying the relevant physical processes that are responsible for the observed medium-induced jet modifications. These studies combine theory insights, based on the Lund parton splitting map, with sophisticated jet reconstruction techniques, including grooming and background subtraction algorithms.
Interactions of hard partons in the Quark Gluon Plasma (QGP) created with relativistic heavy ion collisions lead to characteristic modifications of the internal structure of reconstructed jets. A ...large part of the observed jet sub-structure modifications stem from the QGP’s response to energy and momentum deposited by hard partons. Good control over medium response in theoretical calculations is thus instrumental to a quantitative understanding of medium modified (quenched) jets in heavy ion collisions. We present an improved way of handling the medium response in the jet quenching model
Jewel
and present results for a variety of jet sub-structure observables. The new recoil handling is more versatile and robust than the old scheme, giving a better control over many observables and, in particular, greatly improves the description of the jet mass.
Exploring the time axis within medium-modified jets Apolinario, Liliana; Guerrero-Rodríguez, Pablo; Zapp, Korinna
The European physical journal. C, Particles and fields,
6/7, Volume:
84, Issue:
7
Journal Article
Peer reviewed
Open access
In this manuscript, we illustrate how to use the newly proposed
τ
re-clustering algorithm to select jets with different degrees of quenching without biasing their initial transverse momentum ...spectrum. Our study is based on Z+jet simulated events using the JEWEL Monte Carlo event generator to account for jet quenching effects. We apply the
τ
re-clustering algorithm to extract a proxy for a time axis (formation time) within the evolving medium. This information allows us to label jets according to their fragmentation pattern and select populations with enhanced sensitivity to quenching effects. Our results illustrate the potential of jets as precision tools for QGP tomography. Further, we show that the discussed method minimizes the biases stemming from
p
T
-,
Δ
R
- or mass-based jet selection.
We introduce the parton cascade
Alpaca
, which evolves parton ensembles corresponding to single events according to the effective kinetic theory of QCD at high temperature formulated by Arnold, Moore ...and Yaffe by explicitly simulating elastic scattering, splitting and merging. By taking the ensemble average over many events the phase space density (as evolved by the Boltzmann equation) is recovered, but the parton cascade can go beyond the evolution of the mean because it can be turned into a complete event generator that produces fully exclusive final states including fluctuations and correlations. The parton cascade does not require the phase space density as input (except for the initial condition at the starting time). Rather, effective masses and temperature, which are functions of time and are defined as integrals over expressions involving the distribution function, are estimated in each event from just the parton ensemble of that event. We validate the framework by showing that ensembles sampled from a thermal distribution stay in thermal equilibrium even after running the simulation for a long time. This is a non-trivial result, because it requires all parts of the simulation to intertwine correctly.
Jet quenching in heavy ion collisions is expected to be accompanied by recoil effects, but unambiguous signals for the induced medium response have been difficult to identify so far. Here, we argue ...that modern jet substructure measurements can improve this situation qualitatively since they are sensitive to the momentum distribution inside the jet. We show that the groomed subjet shared momentum fraction zg, and the girth of leading and subleading subjets signal recoil effects with dependencies that are absent in a recoilless baseline. We find that recoil effects can explain most of the medium modifications to the zg distribution observed in data. Furthermore, for jets passing the Soft Drop Condition, recoil effects induce in the differential distribution of subjet separation ΔR12 a characteristic increase with ΔR12, and they introduce a characteristic enhancement of the girth of the subleading subjet with decreasing zg. We explain why these qualitatively novel features, that we establish in Jewel+Pythia simulations, reflect generic physical properties of recoil effects that should therefore be searched for as telltale signatures of jet-induced medium response.
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