Medium-evolved fragmentation functions

Armesto, N.; Cunqueiro, L.; Salgado, Carlos A.; Wang, Xiang

doi:10.1088/1126-6708/2008/02/048

Cited by 72 publications

(101 citation statements)

References 52 publications

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“…For inclusive hadron production in heavy-ion collisions [5,9,13,14], the medium-induced modification and evolution of fragmentation functions have been calculated in several frameworks, showing good agreement with data ( [46,47] and references therein). Suppression of inclusive hadron production in heavy-ion collisions has been used to determine the jet transport parameterq [2].…”

Section: Jhep09(2015)170mentioning

confidence: 85%

Measurement of jet quenching with semi-inclusive hadron-jet distributions in central Pb-Pb collisions at s N N = 2.76 $$ \sqrt{s_{\mathrm{NN}}}=2.76 $$ TeV

Adam¹,

Adamová²,

Aggarwal³

et al. 2015

J. High Energ. Phys.

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Abstract:We report the measurement of a new observable of jet quenching in central Pb-Pb collisions at √ s NN = 2.76 TeV, based on the semi-inclusive rate of charged jets recoiling from a high transverse momentum (high-p T ) charged hadron trigger. Jets are measured using collinear-safe jet reconstruction with infrared cutoff for jet constituents of 0.15 GeV, for jet resolution parameters R = 0.2, 0.4 and 0.5. Underlying event background is corrected at the event-ensemble level, without imposing bias on the jet population. Recoil jet spectra are reported in the range 20 < p ch T,jet < 100 GeV. Reference distributions for pp collisions at √ s = 2.76 TeV are calculated using Monte Carlo and NLO pQCD methods, which are validated by comparing with measurements in pp collisions at √ s = 7 TeV. The recoil jet yield in central Pb-Pb collisions is found to be suppressed relative to that in pp collisions. No significant medium-induced broadening of the intra-jet energy profile is observed within 0.5 radians relative to the recoil jet axis. The angular distribution of the recoil jet yield relative to the trigger axis is found to be similar in central Pb-Pb and pp collisions, with no significant medium-induced acoplanarity observed. Large-angle jet deflection, which may provide a direct probe of the nature of the quasi-particles in hot QCD matter, is explored. [17][18][19][20] and enhancement in the rate of energy-imbalanced back-to-back di-jet pairs [21,22] have also been observed in nuclear collisions. A measurement of event-averaged missing p T suggests that the radiated energy induced by the interaction of an energetic parton with the medium is carried to a significant extent by soft particles at large angles relative to the jet axis [23].The measurement of reconstructed jets over a wide range in jet energy and jet resolution parameter (R) is required for comprehensive understanding of jet quenching in heavy-ion collisions. Such measurements are challenging, however, due to the presence of complex, uncorrelated background to the jet signal, and the need to minimize biases in the selected jet population imposed by background suppression techniques. Multiple, complementary measurement approaches, differing both in instrumentation and in analysis algorithm, are therefore important to elucidate the physics of jet quenching using reconstructed jets.In this article we present a new approach to the measurement of jet quenching, based on the semi-inclusive distribution of charged jets recoiling from a high-p T charged hadron trigger ("h-jet" coincidence) in central (0-10%) Pb-Pb collisions at √ s NN = 2.76 TeV. Jets are reconstructed using charged particle tracks with the k T [24] and anti-k T algorithms [25], with infrared cutoff for tracks p T,const > 0.15 GeV/c. Uncorrelated background to the recoil jet signal is corrected solely at the level of ensemble-averaged distributions, without eventby-event discrimination of jet signal from background, using a technique that exploits the phenomenology of jet production in QCD. The...

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Section: Jhep09(2015)170mentioning

confidence: 85%

Measurement of jet quenching with semi-inclusive hadron-jet distributions in central Pb-Pb collisions at s N N = 2.76 $$ \sqrt{s_{\mathrm{NN}}}=2.76 $$ TeV

Adam¹,

Adamová²,

Aggarwal³

et al. 2015

J. High Energ. Phys.

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“…The evolution of such a parton radiation and splitting process leads to a characteristic shape of the fragmentation function [18]. Theoretical models of jet quenching predict an effective change of the shape of the fragmentation function due to the change of the parton radiation pattern in the medium [19][20][21][22]. Experimentally, fragmentation functions are constructed by correlating the reconstructed jet momentum with the momenta of charged particles projected onto the jet axis.…”

Section: Introductionmentioning

confidence: 99%

Measurement of jet fragmentation into charged particles in pp and PbPb collisions at $ \sqrt{{{s_{\mathrm{NN}}}}} = 2.76 $ TeV

Chatrchyan¹,

Khachatryan²,

Sirunyan³

et al. 2012

J. High Energ. Phys.

122

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Jet fragmentation in pp and PbPb collisions at a centre-of-mass energy of 2.76 TeV per nucleon pair was studied using data collected with the CMS detector at the LHC. Fragmentation functions are constructed using charged-particle tracks with transverse momenta p T > 4 GeV/c for dijet events with a leading jet of p T > 100 GeV/c. The fragmentation functions in PbPb events are compared to those in pp data as a function of collision centrality, as well as dijet-p T imbalance. Special emphasis is placed on the most central PbPb events including dijets with unbalanced momentum, indicative of energy loss of the hard scattered parent partons. The fragmentation patterns for both the leading and subleading jets in PbPb collisions agree with those seen in pp data at 2.76 TeV. The results provide evidence that, despite the large parton energy loss observed in PbPb collisions, the partition of the remaining momentum within the jet cone into high-p T particles is not strongly modified in comparison to that observed for jets in vacuum.

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“…Resummation of medium induced gluon bremsstrahlung in terms of a Monte Carlo simulation of parton shower has been carried out [34,35] within the framework of opacity expansion for induced gluon bremsstrahlung [4], which is equivalent to solving the mDGLAP evolution equations. The mDGLAP evolution equations as derived in the higher-twist approach [6,7] have also been recently studied numerically [36] for modified fragmentation function in DIS off nuclear targets as this work is being completed.…”

Section: Introductionmentioning

confidence: 99%

Multiple parton scattering in nuclei: Modified Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution for fragmentation functions

Deng

Wang

2010

Phys. Rev. C

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Within the framework of generalized factorization of higher-twist contributions to semi-inclusive cross section of deeply inelastic scattering off a large nucleus, multiple parton scattering leads to an effective medium-modified fragmentation function and the corresponding medium-modified DGLAP evolution equations. We extend the study to include gluon multiple scattering and induced quarkantiquark production via gluon fusion . We numerically solve these medium-modified DGLAP (mDGLAP) evolution equations and study the scale (Q 2 ), energy (E), length (L) and jet transport parameter (q) dependence of the modified fragmentation functions for a jet propagating in a uniform medium with finite length (a "brick" problem). We also discuss the concept of parton energy loss within such mDGLAP evolution equations and its connection to the modified fragmentation functions. With a realistic Wood-Saxon nuclear geometry, we calculate the modified fragmentation functions and compare to experimental data of DIS off large nuclei. The extracted jet transport parameter at the center of a large nucleus is found to beq0 = 0.024 ± 0.008 GeV 2 /fm.

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Medium-evolved fragmentation functions

Cited by 72 publications

References 52 publications

Measurement of jet quenching with semi-inclusive hadron-jet distributions in central Pb-Pb collisions at s N N = 2.76 $$ \sqrt{s_{\mathrm{NN}}}=2.76 $$ TeV

Measurement of jet quenching with semi-inclusive hadron-jet distributions in central Pb-Pb collisions at s N N = 2.76 $$ \sqrt{s_{\mathrm{NN}}}=2.76 $$ TeV

Measurement of jet fragmentation into charged particles in pp and PbPb collisions at $ \sqrt{{{s_{\mathrm{NN}}}}} = 2.76 $ TeV

Multiple parton scattering in nuclei: Modified Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution for fragmentation functions

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