The field of jet quenching studies is witnessing an interesting development marked by the appearance of jet sub-structure observables. I give my personal view on this class of observables and comment ...on how they are connected to thermalisation.
Exploring the time axis within medium-modified jets Apolinario, Liliana; Guerrero-Rodríguez, Pablo; Zapp, Korinna
The European physical journal. C, Particles and fields,
07/2024, Letnik:
84, Številka:
7
Journal Article
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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.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The di-jet asymmetry—the measure of the momentum imbalance in a di-jet system—is a key jet quenching observable. Using the event generator
Jewel
we show that the di-jet asymmetry is dominated by ...fluctuations both in proton–proton and in heavy-ion collisions. We discuss how in proton–proton collisions the asymmetry is generated through recoil and out-of-cone radiation. In heavy-ion collisions two additional sources can contribute to the asymmetry, namely energy loss fluctuations and differences in path length. The latter is shown to be a sub-leading effect. We discuss the implications of our results for the interpretation of this observable.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Hydrodynamics and jets in dialogue Floerchinger, Stefan; Zapp, Korinna C.
European physical journal. C, Particles and fields,
12/2014, Letnik:
74, Številka:
12
Journal Article
Recenzirano
Odprti dostop
Energy and momentum loss of jets in heavy ion collisions can affect the fluid dynamic evolution of the medium. We determine realistic event-by-event averages and correlation functions of the local ...energy-momentum transfer from hard particles to the soft sector using the jet-quenching Monte-Carlo code
Jewel
combined with a hydrodynamic model for the background. The expectation values for source terms due to jets in a typical (minimum-bias) event affect the fluid dynamic evolution mainly by their momentum transfer. This leads to a small increase in flow. The presence of hard jets in the event constitutes only a minor correction.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
By combining the jet quenching Monte Carlo Jewel with a realistic hydrodynamic model for the background we investigate the sensitivity of jet observables to details of the medium model and quantify ...the influence of the energy and momentum lost by jets on the background evolution. On the level of event averaged source terms the effects are small and are caused mainly by the momentum transfer.
Monte Carlo (MC) simulations are the standard tool for describing jet-like multi-particle final states. To apply them to the simulation of medium-modified jets in heavy ion collisions, a ...probabilistic implementation of medium-induced quantum interference effects is needed. Here, we analyze in detail how the quantum interference effects included in the Baier-Dokshitzer-Mueller-Peigné-Schiff–Zakharov (BDMPS-Z) formalism of medium-induced gluon radiation can be implemented in a quantitatively controlled, local probabilistic parton cascade. The resulting MC algorithm is formulated in terms of elastic and inelastic mean free paths, and it is by construction insensitive to the IR and UV divergences of the total elastic and inelastic cross sections that serve as its basic building blocks in the incoherent limit. Interference effects are implemented by reweighting gluon production histories as a function of the number of scattering centers that act within the gluon formation time. Unlike existing implementations based on gluon formation time, we find generic arguments for why a quantitative implementation of quantum interference cannot amount to a mere dead-time requirement for subsequent gluon production. We validate the proposed MC algorithm by comparing MC simulations with parametric dependencies and analytical results of the BDMPS-Z formalism. In particular, we show that the MC algorithm interpolates correctly between analytically known limiting cases for totally coherent and incoherent gluon production, and that it accounts quantitatively for the medium-induced gluon energy distribution
ω
d
I
/d
ω
and the resulting average parton energy loss. We also verify that the MC algorithm implements the transverse momentum broadening of the BDMPS-Z formalism. We finally discuss why the proposed MC algorithm provides a suitable starting point for going beyond the approximations of the BDMPS-Z formalism.
It is widely accepted that a phenomenologically viable theory of jet quenching for heavy ion collisions requires the understanding of medium-induced parton energy loss beyond the limit of eikonal ...kinematics formulated by Baier–Dokshitzer–Mueller–Peigné–Schiff and Zakharov (BDMPS-Z). Here, we supplement a recently developed exact Monte Carlo implementation of the BDMPS-Z formalism with elementary physical requirements including exact energy-momentum conservation, a refined formulation of jet-medium interactions and a treatment of all parton branchings on the same footing. We document the changes induced by these physical requirements and we describe their kinematic origin.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Processes in which a jet recoils against an electroweak boson complement studies of jet quenching in heavy ion collisions at the LHC. As the boson does not interact strongly it escapes the dense ...medium unmodified and thus provides a more direct access to the hard scattering kinematics than can be obtained in di-jet events. First measurements of jet modification in these processes are now available from the LHC experiments and will improve greatly with better statistics in the future. We present an extension of
Jewel
to boson–jet processes.
Jewel
is a dynamical framework for jet evolution in a dense background based on perturbative QCD that is in agreement with a large variety of jet observables. We also obtain a good description of the CMS and ATLAS data for
γ
+jet and
Z
+jet processes at 2.76 and 5.02 TeV.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Extending the use of Monte Carlo (MC) event generators to jets in nuclear collisions requires a probabilistic implementation of the non-abelian LPM effect. We demonstrate that a local, probabilistic ...MC implementation based on the concept of formation times can account fully for the LPM-effect. The main features of the analytically known eikonal and collinear approximation can be reproduced, but we show how going beyond this approximation can lead to qualitatively different results.
We show that partons traversing a quark–gluon plasma can lose substantial amounts of energy also by scatterings, and not only through medium-induced radiation as mainly considered previously. Results ...from Monte Carlo simulations of soft interactions of partons, emerging from a hard scattering, through multiple elastic scatterings on gluons in an expanding relativistic plasma show a sizeable jet quenching which can account for a substantial part of the effect observed in RHIC data.
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