12 research outputs found
The JETSCAPE framework
The JETSCAPE simulation framework is an overarching computational envelope
for developing complete event generators for heavy-ion collisions. It allows
for modular incorporation of a wide variety of existing and future software
that simulates different aspects of a heavy-ion collision. The default JETSCAPE
package contains both the framework, and an entire set of indigenous and third
party routines that can be used to directly compare with experimental data. In
this article, we outline the algorithmic design of the JETSCAPE framework,
define the interfaces and describe the default modules required to carry out
full simulations of heavy-ion collisions within this package. We begin with a
description of the various physics elements required to simulate an entire
event in a heavy-ion collision, and distribute these within a flowchart
representing the event generator and statistical routines for comparison with
data. This is followed by a description of the abstract class structure, with
associated members and functions required for this flowchart to work. We then
define the interface that will be required for external users of JETSCAPE to
incorporate their code within this framework and to modify existing elements
within the default distribution. We conclude with a discussion of some of the
physics output for both - and - collisions from the default
distribution, and an outlook towards future releases. In the appendix, we
discuss various architectures on which this code can be run and outline our
benchmarks on similar hardware.Comment: 93 pages, 13 figure
Multistage Monte-Carlo simulation of jet modification in a static medium
The modification of hard jets in an extended static medium held at a fixed
temperature is studied using three different Monte-Carlo event generators (LBT,
MATTER, MARTINI). Each event generator contains a different set of assumptions
regarding the energy and virtuality of the partons within a jet versus the
energy scale of the medium, and hence, applies to a different epoch in the
space-time history of the jet evolution. For the first time, modeling is
developed where a jet may sequentially transition from one generator to the
next, on a parton-by-parton level, providing a detailed simulation of the
space-time evolution of medium modified jets over a much broader dynamic range
than has been attempted previously in a single calculation. Comparisons are
carried out for different observables sensitive to jet quenching, including the
parton fragmentation function and the azimuthal distribution of jet energy
around the jet axis. The effect of varying the boundary between different
generators is studied and a theoretically motivated criterion for the location
of this boundary is proposed. The importance of such an approach with coupled
generators to the modeling of jet quenching is discussed.Comment: 10 pages, 4 figure
Multi-stage jet evolution through QGP using the JETSCAPE framework: inclusive jets, correlations and leading hadrons
The JETSCAPE Collaboration has recently announced the first release of the
JETSCAPE package that provides a modular, flexible, and extensible Monte Carlo
event generator. This innovative framework makes it possible to perform a
comprehensive study of multi-stage high-energy jet evolution in the Quark-Gluon
Plasma. In this work, we illustrate the performance of the event generator for
different algorithmic approaches to jet energy loss, and reproduce the
measurements of several jet and hadron observables as well as correlations
between the hard and soft sector. We also carry out direct comparisons between
different approaches to energy loss to study their sensitivity to those
observables
Jet substructure modification in a QGP from a multi-scale description of jet evolution with JETSCAPE
The modification of jet substructure in relativistic heavy-ion collisions is
studied using JETSCAPE, a publicly available software package containing a
framework for Monte Carlo event generators. Multi-stage jet evolution in
JETSCAPE provides an integrated description of jet quenching by combining
multiple models, with each becoming active at a different stage of the parton
shower evolution. Jet substructure modification due to different aspects of jet
quenching is studied using jet shape and jet fragmentation observables. Various
combinations of jet energy loss models are exploed, with medium background
provided by (2 + 1)-D VISHNU with TRENTo+freestreaming initial conditions.
Results reported here are from simulations performed within JETSCAPE framework.Comment: 4 pages, 3 figures, Proceedings of Hard Probes 2018, 30 September-5
October, Aix-Les-Bains, Franc
First results from Hybrid Hadronization in small and large systems
"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 a variety of systems from to collisions. It takes
systems of partons and their color flow information, for example from a Monte
Carlo parton shower generator, as input. In addition, if for collisions a
thermal background medium is provided, the package allows sampling thermal
partons that contribute to hadronization. Hybrid Hadronization is available for
use as a standalone code and is also part of JETSCAPE since the 2.0 release. In
these proceedings we review the physics concepts underlying Hybrid
Hadronization and demonstrate how users can use the code with various parton
shower Monte Carlos. We present calculations of hadron chemistry and
fragmentation functions in small and large systems when Hybrid Hadronization is
combined with parton shower Monte Carlos MATTER and LBT. In particular, we
discuss observable effects of the recombination of shower partons with thermal
partons.Comment: 4 pages, 3 figures, Proceedings of Hard Probes 2020, 1-6 June 2020,
Austin, Texas; Updated Author lis
Determining the jet transport coefficient of the quark-gluon plasma using Bayesian parameter estimation
We present a new determination of , the jet transport coefficient of
the quark-gluon plasma. Using the JETSCAPE framework, we use Bayesian parameter
estimation to constrain the dependence of on the jet energy,
virtuality, and medium temperature from experimental measurements of inclusive
hadron suppression in Au-Au collisions at RHIC and Pb-Pb collisions at the LHC.
These results are based on a multi-stage theoretical approach to in-medium jet
evolution with the MATTER and LBT jet quenching models. The functional
dependence of on jet energy, virtuality, and medium temperature is
based on a perturbative picture of in-medium scattering, with components
reflecting the different regimes of applicability of MATTER and LBT. The
correlation of experimental systematic uncertainties is accounted for in the
parameter extraction. These results provide state-of-the-art constraints on
and lay the groundwork to extract additional properties of the
quark-gluon plasma from jet measurements in heavy-ion collisions.Comment: contribution to the 2021 QCD session of the 55th Recontres de Morion
Photon-jet correlations in p-p and Pb-Pb collisions using JETSCAPE framework
It is now well established that jet modification is a multistage effect;
hence a single model alone cannot describe all facets of jet modification. The
JETSCAPE framework is a multistage framework that uses several modules to
simulate different stages of jet propagation through the QGP medium. These
simulations require a set of parameters to ensure a smooth transition between
stages. We fine tune these parameters to successfully describe a variety of
observables, such as the nuclear modification factors of leading hadrons and
jets, jet shape, and jet fragmentation function. Photons can be produced in the
hard scattering or as radiation from quarks inside jets. In this work, we study
photon-jet transverse momentum imbalance and azimuthal correlation for both
and collision systems. All the photons produced in each event,
including the photons from hard scattering, radiation from the parton shower,
and radiation from hadronization are considered with an isolation cut to
directly compare with experimental data. The simulations are conducted using
the same set of tuned parameters as used for the jet analysis. No new
parameters are introduced or tuned. We demonstrate a significantly improved
agreement with photons from collisions compared to prior efforts. This
work provides an independent, parameter free verification of the multistage
evolution framework.Comment: 4 pages, 7 figure
Hydrodynamic response to jets with a source based on causal diffusion
We study the medium response to jet evolution in the quark-gluon plasma
within the JETSCAPE framework. Recoil partons' medium response in the weakly
coupled description is implemented in the multi-stage jet energy-loss model in
the framework. As a further extension, the hydrodynamic description is
rearranged to include in-medium jet transport based on a strong-coupling
picture. To interface hydrodynamics with jet energy-loss models, the
hydrodynamic source term is modeled by a causal formulation employing the
relativistic diffusion equation. The jet shape and fragmentation function are
studied via realistic simulations with weakly coupled recoils. We also
demonstrate modifications in the medium caused by the hydrodynamic response.Comment: 4 pages, 2 figures, contribution to the Quark Matter 2019 proceeding
Jet quenching in a multi-stage Monte Carlo approach
We present a jet quenching model within a unified multi-stage framework and
demonstrate for the first time a simultaneous description of leading hadrons,
inclusive jets, and elliptic flow observables which spans multiple centralities
and collision energies. This highlights one of the major successes of the
JETSCAPE framework in providing a tool for setting up an effective parton
evolution that includes a high-virtuality radiation dominated energy loss phase
(MATTER), followed by a low-virtuality scattering dominated (LBT) energy loss
phase. Measurements of jet and charged-hadron set strong constraints
on the jet quenching model. Jet-medium response is also included through a
weakly-coupled transport description.Comment: 4 pages, 4 figures, contribution to the Quark Matter 2019 proceeding
Probing the multi-scale dynamical interaction between heavy quarks and the QGP using JETSCAPE
The dynamics of shower development for a jet traveling through the QGP
involves a variety of scales, one of them being the heavy quark mass. Even
though the mass of the heavy quarks plays a subdominant role during the high
virtuality portion of the jet evolution, it does affect longitudinal drag and
diffusion, stimulating additional radiation from heavy quarks. These emissions
partially compensate the reduction in radiation from the dead cone effect. In
the lower virtuality part of the shower, when the mass is comparable to the
transverse momenta of the partons, scattering and radiation processes off heavy
quarks differ from those off light quarks. All these factors result in a
different nuclear modification factor for heavy versus light flavors and thus
for heavy-flavor tagged jets.
In this study, the heavy quark shower evolution and the fluid dynamical
medium are modeled on an event by event basis using the JETSCAPE Framework. We
present a multi-stage calculation that explores the differences between various
heavy quark energy-loss mechanisms within a realistically expanding quark-gluon
plasma (QGP). Inside the QGP, the highly virtual and energetic portion of the
shower is modeled using the MATTER generator, while the LBT generator models
the showers induced by energetic and close-to-on-shell heavy quarks.
Energy-momentum exchange with the medium, essential for the study of jet
modification, proceeds using a weak coupling recoil approach. The JETSCAPE
framework allows for transitions, on the level of individual partons, from one
energy-loss prescription to the other depending on the parton's energy and
virtuality and the local density. This allows us to explore the effect and
interplay between the different regimes of energy loss on the propagation and
radiation from hard heavy quarks in a dense medium