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An analysis of the influence of background subtraction and quenching on jet observables in heavy-ion collisions
High Energy Physics - Phenomenology · Submitted 6 Nov 2012
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim The average background level and fluctuations affect both single inclusive spectra and dijet asymmetries, although differently for different subtraction setups.
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The abstract, sentence by sentence
Subtraction of the large background in reconstruction is a key ingredient in jet studies in high-energy heavy-ion collisions at RHIC and the LHC. Here we address the question to which extent the most commonly used subtraction techniques are able to eliminate the effects of the background on the most commonly discussed observables at present: single inclusive jet distributions, dijet asymmetry and azimuthal distributions. We consider two different background subtraction methods, an area-based one implemented through the FastJet pack- age and a pedestal subtraction method, that resemble the ones used by the experimental collaborations at the LHC. We also analyze different ways of defining the optimal parame- ters in the second method. We use a toy model that easily allows variations of the background characteristics: average background level and fluctuations and azimuthal structure, but cross- checks are also done with a Monte Carlo simulator. Furthermore, we consider the influence of quenching using Q-PYTHIA on the dijet observables with the different background subtrac- tion methods and, additionally, we examine the missing momentum of particles. The average background level and fluctuations affect both single inclusive spectra and dijet asymmetries, although differently for different subtraction setups. A large azimuthal modulation of the background has a visible effect on the azimuthal dijet distributions. Quenching, as imple- mented in Q-PYTHIA, substantially affects the dijet asymmetry but little the azimuthal dijet distributions. Besides, the missing momentum characteristics observed in the experiment are qualitatively reproduced by Q-PYTHIA.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | Subtraction of the large background in reconstruction is a key ingredient in jet studies in high-energy heavy-ion collisions at RHIC and the LHC. | background 1.00 | 0.05 | 0.03 | asserted 1.00 |
| s1 | Here we address the question to which extent the most commonly used subtraction techniques are able to eliminate the effects of the background on the most commonly discussed observables at present: single inclusive jet distributions, dijet asymmetry and azimuthal distributions. | contribution 0.83 | 0.37 | 0.04 | unclear 0.81 |
| s2 | We consider two different background subtraction methods, an area-based one implemented through the FastJet pack- age and a pedestal subtraction method, that resemble the ones used by the experimental collaborations at the LHC. | method 0.97 | 0.81 | 0.03 | asserted 0.96 |
| s3 | We also analyze different ways of defining the optimal parame- ters in the second method. | method 0.94 | 0.92 | 0.02 | asserted 0.60 |
| s4 | We use a toy model that easily allows variations of the background characteristics: average background level and fluctuations and azimuthal structure, but cross- checks are also done with a Monte Carlo simulator. | method 1.00 | 0.93 | 0.02 | asserted 0.98 |
| s5 | Furthermore, we consider the influence of quenching using Q-PYTHIA on the dijet observables with the different background subtrac- tion methods and, additionally, we examine the missing momentum of particles. | contribution 0.58 | 0.92 | 0.04 | asserted 0.83 |
| s6 | The average background level and fluctuations affect both single inclusive spectra and dijet asymmetries, although differently for different subtraction setups. | result 1.00 | 0.92 | 0.21 | asserted 1.00 |
| s7 | A large azimuthal modulation of the background has a visible effect on the azimuthal dijet distributions. | result 1.00 | 0.88 | 0.10 | asserted 0.99 |
| s8 | Quenching, as imple- mented in Q-PYTHIA, substantially affects the dijet asymmetry but little the azimuthal dijet distributions. | result 1.00 | 0.89 | 0.21 | asserted 1.00 |
| s9 | Besides, the missing momentum characteristics observed in the experiment are qualitatively reproduced by Q-PYTHIA. | result 0.97 | 0.84 | 0.08 | asserted 0.93 |
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The paper
Original abstract
Subtraction of the large background in reconstruction is a key ingredient in jet studies in high-energy heavy-ion collisions at RHIC and the LHC. Here we address the question to which extent the most commonly used subtraction techniques are able to eliminate the effects of the background on the most commonly discussed observables at present: single inclusive jet distributions, dijet asymmetry and azimuthal distributions. We consider two different background subtraction methods, an area-based one implemented through the FastJet pack- age and a pedestal subtraction method, that resemble the ones used by the experimental collaborations at the LHC. We also analyze different ways of defining the optimal parame- ters in the second method. We use a toy model that easily allows variations of the background characteristics: average background level and fluctuations and azimuthal structure, but cross- checks are also done with a Monte Carlo simulator. Furthermore, we consider the influence of quenching using Q-PYTHIA on the dijet observables with the different background subtrac- tion methods and, additionally, we examine the missing momentum of particles. The average background level and fluctuations affect both single inclusive spectra and dijet asymmetries, although differently for different subtraction setups. A large azimuthal modulation of the background has a visible effect on the azimuthal dijet distributions. Quenching, as imple- mented in Q-PYTHIA, substantially affects the dijet asymmetry but little the azimuthal dijet distributions. Besides, the missing momentum characteristics observed in the experiment are qualitatively reproduced by Q-PYTHIA.
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References
How the literature uses it
20 arXiv papers cite this in 22 sentences
Papers citing it · 13 sentences without a confident label
Cites it as background 9 papers
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As the running of heavy-ion programs at the LHC with its unprecedented colliding energies, the study of parton energy loss has been extended to medium modifications of many jet observables [ref] .
Multijet topology in high-energy nuclear collisions: jet broadening · Introduction · 0.83
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In recent years, the experimental reconstruction of full jets with a given cone size defined as $R=√((Δϕ)^2 + (Δη)^2)$ from large fluctuating background became available in relativistic heavy-ion experiments [ref] , which has stimulated intensive theoretical interest in the study of full jets and their nuclear modification in high-energy nuclear collisions [ref] .
Full jet evolution in quark-gluon plasma and nuclear modification of jet production and jet shape in Pb+Pb collisions at 2.76 ATeV at the LHC · Introduction · 0.80
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The measurements of abundant jet observables in ultra-relativistic heavy-ion collisions have encouraged and stimulated many theoretical studies which aim to understand various details of the interaction between full jets and the QGP medium [ref] .
Nuclear modification of jet shape for inclusive jets and $\gamma$-jets at the LHC energies · Introduction · 0.87
What it cites · 64 sentences without a confident label
Uses the method or tool of 10 papers
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The fluctuations are computed through the 1-$σ$ dispersion (below the median) from the distribution of the ratio $p_T^rec/A^rec$ for all $k_t$ clusters, see [ref] for details.
Jet Reconstruction in Heavy Ion Collisions · Jet Reconstruction · 0.96
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The fluctuations are computed through the 1-$σ$ dispersion (below the median) from the distribution of the ratio $p_T^rec/A^rec$ for all $k_t$ clusters, see [ref] for details.
Pileup subtraction using jet areas · Jet Reconstruction · 0.96
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We use two background subtraction methods: an area-based background subtraction [ref] through FastJet [ref] ; and a pedestal subtraction that attempts to mimic the method used by CMS [ref] .
Observation and studies of jet quenching in PbPb collisions at nucleon-nucleon center-of-mass energy = 2.76 TeV · Introduction · 1.00
Uses data or values from 10 papers
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E.g. the convolution of a steeply falling perturbative jet spectrum with the fluctuations measured by ALICE [ref] in central PbPb collisions using a cut of $p_Tmin = 0.15$ GeV, leads to an enhancement of the jet yield of a factor $∼10$ even for high $E_T> 60$ GeV.
Measurement of event background fluctuations for charged particle jet reconstruction in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV · Background energy and event-by-event fluctuations · 0.98
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In this way we attempt to mimic the $0÷10$ % centrality class [ref] in the experimental analyses [ref] .
Studies of jet quenching using isolated-photon + jet correlations in PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV · Toy model for the background · 0.89
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In this way we attempt to mimic the $0÷10$ % centrality class [ref] in the experimental analyses [ref] .
Observation of a Centrality-Dependent Dijet Asymmetry in Lead-Lead Collisions at sqrt(S(NN))= 2.76 TeV with the ATLAS Detector at the LHC · Toy model for the background · 0.89
Compares with 8 papers
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The increase of $q̂$ induces momentum imbalance: for $q̂=8$ GeV$^2$/fm, the $A_J$ distribution is in qualtitative agreement with experimental data (the agreement seems better when considering the difference between the CMS Monte Carlo and CMS data [ref] ).On the other hand, in spite of the shower being degraded in energy so that a significant $A_J$ is induced by quenching, the azimuthal dijet correlation is not very strongly modified, in apparent conflict with the generic link between energy loss and broadening [ref] .
Jet quenching · Asymmetry · 0.98
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The increase of $q̂$ induces momentum imbalance: for $q̂=8$ GeV$^2$/fm, the $A_J$ distribution is in qualtitative agreement with experimental data (the agreement seems better when considering the difference between the CMS Monte Carlo and CMS data [ref] ).On the other hand, in spite of the shower being degraded in energy so that a significant $A_J$ is induced by quenching, the azimuthal dijet correlation is not very strongly modified, in apparent conflict with the generic link between energy loss and broadening [ref] .
Jet Quenching in Heavy Ion Collisions · Asymmetry · 0.98
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The increase of $q̂$ induces momentum imbalance: for $q̂=8$ GeV$^2$/fm, the $A_J$ distribution is in qualtitative agreement with experimental data (the agreement seems better when considering the difference between the CMS Monte Carlo and CMS data [ref] ).On the other hand, in spite of the shower being degraded in energy so that a significant $A_J$ is induced by quenching, the azimuthal dijet correlation is not very strongly modified, in apparent conflict with the generic link between energy loss and broadening [ref] .
The theory and phenomenology of perturbative QCD based jet quenching · Asymmetry · 0.98
Cites as support 1 paper
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Indeed, it has been noted in [ref] that the fluctuations in a single-event background may affect the dijet energy imbalance and thus the extraction of medium properties and the characterization of the energy loss mechanism.
Fluctuations and asymmetric jet events in PbPb collisions at the LHC · Introduction · 0.99
Cites as background 6 papers
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The effect of background fluctuations on jet observables has extensively been discussed in [ref] .
Fluctuations and asymmetric jet events in PbPb collisions at the LHC · Background energy and event-by-event fluctuations · 0.95
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On the other hand, jet studies in hadronic collisions demand a procedure in order to separate jet constituents from the background of soft particles not coming from the shower of a hard parton, see [ref] and refs. therein.
Towards Jetography · Introduction · 0.83
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Among the different hard probes, the suppression of energetic particles and of jet-like correlations generically called jet quenching, see [ref] for recent reviews, lies among the most prominent ones.
Jet quenching · Introduction · 1.00
Discussion
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