Advertisement

Journal of High Energy Physics

, 2019:273 | Cite as

Deciphering the 𝓏g distribution in ultrarelativistic heavy ion collisions

  • P. Caucal
  • E. Iancu
  • G. SoyezEmail author
Open Access
Regular Article - Theoretical Physics
  • 22 Downloads

Abstract

Within perturbative QCD, we develop a new picture for the parton shower generated by a jet propagating through a dense quark-gluon plasma. This picture combines in a simple, factorised, way multiple medium-induced parton branchings and standard vacuum-like emissions, with the phase-space for the latter constrained by the presence of the medium. We implement this picture as a Monte Carlo generator that we use to study two phenomenologically important observables: the jet nuclear modification factor RAA and the 𝓏g distribution reflecting the jet substructure. In both cases, the outcome of our Monte Carlo simulations is in good agreement with the LHC measurements. We provide basic analytic calculations that help explaining the main features observed in the data. We find that the energy loss by the jet is increasing with the jet transverse momentum, due to a rise in the number of partonic sources via vacuum-like emissions. This is a key element in our description of both RAA and the 𝓏g distribution. For the latter, we identify two main nuclear effects: incoherent jet energy loss and hard medium-induced emissions. As the jet transverse momentum increases, we predict a qualitative change in the ratio between the 𝓏g distributions in PbPb and pp collisions: from increasing at small 𝓏g, this ratio becomes essentially flat, or even slightly decreasing.

Keywords

Heavy Ion Phenomenology Jets 

Notes

Open Access

This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited

References

  1. [1]
    Y. Mehtar-Tani, J.G. Milhano and K. Tywoniuk, Jet physics in heavy-ion collisions, Int. J. Mod. Phys.A 28 (2013) 1340013 [arXiv:1302.2579] [INSPIRE].
  2. [2]
    J.-P. Blaizot and Y. Mehtar-Tani, Jet structure in heavy ion collisions, Int. J. Mod. Phys.E 24 (2015) 1530012 [arXiv:1503.05958] [INSPIRE].
  3. [3]
    G.-Y. Qin and X.-N. Wang, Jet quenching in high-energy heavy-ion collisions, Int. J. Mod. Phys.E 24 (2015) 1530014 [arXiv:1511.00790] [INSPIRE].
  4. [4]
    H.A. Andrews et al., Novel tools and observables for jet physics in heavy-ion collisions, arXiv:1808.03689 [INSPIRE].
  5. [5]
    A.J. Larkoski, S. Marzani and J. Thaler, Sudakov safety in perturbative QCD, Phys. Rev.D 91 (2015) 111501 [arXiv:1502.01719] [INSPIRE].
  6. [6]
    A.J. Larkoski, S. Marzani, G. Soyez and J. Thaler, Soft drop, JHEP05 (2014) 146 [arXiv:1402.2657] [INSPIRE].
  7. [7]
    CMS collaboration, Measurement of the splitting function in pp and Pb-Pb collisions at \( \sqrt{{}^s\mathrm{NN}} \) = 5.02 TeV, Phys. Rev. Lett.120 (2018) 142302 [arXiv:1708.09429] [INSPIRE].
  8. [8]
    ALICE collaboration, Exploration of jet substructure using iterative declustering in pp and Pb-Pb collisions at LHC energies, arXiv:1905.02512 [INSPIRE].
  9. [9]
    Y.-T. Chien and I. Vitev, Probing the hardest branching within jets in heavy-ion collisions, Phys. Rev. Lett.119 (2017) 112301 [arXiv:1608.07283] [INSPIRE].
  10. [10]
    Y. Mehtar-Tani and K. Tywoniuk, Groomed jets in heavy-ion collisions: sensitivity to medium-induced bremsstrahlung, JHEP04 (2017) 125 [arXiv:1610.08930] [INSPIRE].
  11. [11]
    N.-B. Chang, S. Cao and G.-Y. Qin, Probing medium-induced jet splitting and energy loss in heavy-ion collisions, Phys. Lett.B 781 (2018) 423 [arXiv:1707.03767] [INSPIRE].
  12. [12]
    G. Milhano, U.A. Wiedemann and K.C. Zapp, Sensitivity of jet substructure to jet-induced medium response, Phys. Lett.B 779 (2018) 409 [arXiv:1707.04142] [INSPIRE].
  13. [13]
    Y.L. Dokshitzer, G.D. Leder, S. Moretti and B.R. Webber, Better jet clustering algorithms, JHEP08 (1997) 001 [hep-ph/9707323] [INSPIRE].
  14. [14]
    M. Wobisch and T. Wengler, Hadronization corrections to jet cross-sections in deep inelastic scattering, in the proceedings of the Monte Carlo generators for HERA physics, April 27–30, Hamburg, Germany (1998), hep-ph/9907280 [INSPIRE].
  15. [15]
    Y.L. Dokshitzer, V.A. Khoze, A.H. Mueller and S.I. Troian, Basics of perturbative QCD, Ed. Frontieres, Gif-sur-Yvette France (1991).Google Scholar
  16. [16]
    R. Baier et al., Radiative energy loss of high-energy quarks and gluons in a finite volume quark-gluon plasma, Nucl. Phys.B 483 (1997) 291 [hep-ph/9607355] [INSPIRE].
  17. [17]
    R. Baier et al., Radiative energy loss and p Tbroadening of high-energy partons in nuclei, Nucl. Phys.B 484 (1997) 265 [hep-ph/9608322] [INSPIRE].
  18. [18]
    B.G. Zakharov, Fully quantum treatment of the Landau-Pomeranchuk-Migdal effect in QED and QCD, JETP Lett.63 (1996) 952 [hep-ph/9607440] [INSPIRE].
  19. [19]
    B.G. Zakharov, Radiative energy loss of high-energy quarks in finite size nuclear matter and quark-gluon plasma, JETP Lett.65 (1997) 615 [hep-ph/9704255] [INSPIRE].
  20. [20]
    R. Baier, Y.L. Dokshitzer, A.H. Mueller and D. Schiff, Medium induced radiative energy loss: equivalence between the BDMPS and Zakharov formalisms, Nucl. Phys.B 531 (1998) 403 [hep-ph/9804212] [INSPIRE].
  21. [21]
    Y. Mehtar-Tani, C.A. Salgado and K. Tywoniuk, Anti-angular ordering of gluon radiation in QCD media, Phys. Rev. Lett.106 (2011) 122002 [arXiv:1009.2965] [INSPIRE].
  22. [22]
    Y. Mehtar-Tani, C.A. Salgado and K. Tywoniuk, Jets in QCD media: from color coherence to decoherence, Phys. Lett.B 707 (2012) 156 [arXiv:1102.4317] [INSPIRE].
  23. [23]
    J. Casalderrey-Solana and E. Iancu, Interference effects in medium-induced gluon radiation, JHEP08 (2011) 015 [arXiv:1105.1760] [INSPIRE].
  24. [24]
    J.-P. Blaizot, F. Dominguez, E. Iancu and Y. Mehtar-Tani, Medium-induced gluon branching, JHEP01 (2013) 143 [arXiv:1209.4585] [INSPIRE].
  25. [25]
    J.-P. Blaizot, F. Dominguez, E. Iancu and Y. Mehtar-Tani, Probabilistic picture for medium-induced jet evolution, JHEP06 (2014) 075 [arXiv:1311.5823] [INSPIRE].
  26. [26]
    L. Apolinário, N. Armesto, J.G. Milhano and C.A. Salgado, Medium-induced gluon radiation and colour decoherence beyond the soft approximation, JHEP02 (2015) 119 [arXiv:1407.0599] [INSPIRE].
  27. [27]
    P. Caucal, E. Iancu, A.H. Mueller and G. Soyez, Vacuum-like jet fragmentation in a dense QCD medium, Phys. Rev. Lett.120 (2018) 232001 [arXiv:1801.09703] [INSPIRE].
  28. [28]
    J.-P. Blaizot, E. Iancu and Y. Mehtar-Tani, Medium-induced QCD cascade: democratic branching and wave turbulence, Phys. Rev. Lett.111 (2013) 052001 [arXiv:1301.6102] [INSPIRE].
  29. [29]
    L. Fister and E. Iancu, Medium-induced jet evolution: wave turbulence and energy loss, JHEP03 (2015) 082 [arXiv:1409.2010] [INSPIRE].
  30. [30]
    ATLAS collaboration, Measurement of the nuclear modification factor for inclusive jets in Pb+Pb collisions at \( \sqrt{{}^s\mathrm{NN}} \) = 5.02 TeV with the ATLAS detector, Phys. Lett.B 790 (2019) 108 [arXiv:1805.05635] [INSPIRE].
  31. [31]
    STAR collaboration, Measurement of the shared momentum fraction 𝓏gusing jet reconstruction in p+p and Au+Au collisions with STAR, Nucl. Part. Phys. Proc.289-290 (2017) 137 [arXiv:1703.10933] [INSPIRE].
  32. [32]
    T. Liou, A.H. Mueller and B. Wu, Radiative p -broadening of high-energy quarks and gluons in QCD matter, Nucl. Phys.A 916 (2013) 102 [arXiv:1304.7677] [INSPIRE].
  33. [33]
    J.-P. Blaizot and Y. Mehtar-Tani, Renormalization of the jet-quenching parameter, Nucl. Phys.A 929 (2014) 202 [arXiv:1403.2323] [INSPIRE].
  34. [34]
    E. Iancu, The non-linear evolution of jet quenching, JHEP10 (2014) 095 [arXiv:1403.1996] [INSPIRE].
  35. [35]
    Y. Mehtar-Tani, C.A. Salgado and K. Tywoniuk, The radiation pattern of a QCD antenna in a dilute medium, JHEP04 (2012) 064 [arXiv:1112.5031] [INSPIRE].
  36. [36]
    Y. Mehtar-Tani and K. Tywoniuk, Radiative energy loss of neighboring subjets, Nucl. Phys.A 979 (2018) 165 [arXiv:1706.06047] [INSPIRE].
  37. [37]
    P. Arnold and S. Iqbal, The LPM effect in sequential bremsstrahlung, JHEP04 (2015) 070 [Erratum ibid.09 (2016) 072] [arXiv:1501.04964] [INSPIRE].
  38. [38]
    P. Arnold, H.-C. Chang and S. Iqbal, The LPM effect in sequential bremsstrahlung 2: factorization, JHEP09 (2016) 078 [arXiv:1605.07624] [INSPIRE].
  39. [39]
    U.A. Wiedemann, Gluon radiation off hard quarks in a nuclear environment: Opacity expansion, Nucl. Phys.B 588 (2000) 303 [hep-ph/0005129] [INSPIRE].
  40. [40]
    U.A. Wiedemann, Jet quenching versus jet enhancement: A Quantitative study of the BDMPS-Z gluon radiation spectrum, Nucl. Phys.A 690 (2001) 731 [hep-ph/0008241] [INSPIRE].
  41. [41]
    P.B. Arnold, G.D. Moore and L.G. Yaffe, Photon emission from ultrarelativistic plasmas, JHEP11 (2001) 057 [hep-ph/0109064] [INSPIRE].
  42. [42]
    P.B. Arnold, G.D. Moore and L.G. Yaffe, Photon emission from quark gluon plasma: Complete leading order results, JHEP12 (2001) 009 [hep-ph/0111107] [INSPIRE].
  43. [43]
    P.B. Arnold, G.D. Moore and L.G. Yaffe, Photon and gluon emission in relativistic plasmas, JHEP06 (2002) 030 [hep-ph/0204343] [INSPIRE].
  44. [44]
    Y. Mehtar-Tani and S. Schlichting, Universal quark to gluon ratio in medium-induced parton cascade, JHEP09 (2018) 144 [arXiv:1807.06181] [INSPIRE].
  45. [45]
    E. Iancu and B. Wu, Thermalization of mini-jets in a quark-gluon plasma, JHEP10 (2015) 155 [arXiv:1506.07871] [INSPIRE].
  46. [46]
    J.-P. Blaizot, Y. Mehtar-Tani and M.A.C. Torres, Angular structure of the in-medium QCD cascade, Phys. Rev. Lett.114 (2015) 222002 [arXiv:1407.0326] [INSPIRE].
  47. [47]
    J.-P. Blaizot, L. Fister and Y. Mehtar-Tani, Angular distribution of medium-induced QCD cascades, Nucl. Phys.A 940 (2015) 67 [arXiv:1409.6202] [INSPIRE].
  48. [48]
    M.A. Escobedo and E. Iancu, Event-by-event fluctuations in the medium-induced jet evolution, JHEP05 (2016) 008 [arXiv:1601.03629] [INSPIRE].
  49. [49]
    M.A. Escobedo and E. Iancu, Multi-particle correlations and KNO scaling in the medium-induced jet evolution, JHEP12 (2016) 104 [arXiv:1609.06104] [INSPIRE].
  50. [50]
    R. Baier, A.H. Mueller, D. Schiff and D.T. Son, ‘Bottom up’ thermalization in heavy ion collisions, Phys. Lett.B 502 (2001) 51 [hep-ph/0009237] [INSPIRE].
  51. [51]
    M. Cacciari, G.P. Salam and G. Soyez, FastJet user manual, Eur. Phys. J.C 72 (2012) 1896 [arXiv:1111.6097] [INSPIRE].
  52. [52]
    M. Cacciari, G.P. Salam and G. Soyez, The anti-k tjet clustering algorithm, JHEP04 (2008) 063 [arXiv:0802.1189] [INSPIRE].
  53. [53]
    F.A. Dreyer, G.P. Salam and G. Soyez, The Lund jet plane, JHEP12 (2018) 064 [arXiv:1807.04758] [INSPIRE].
  54. [54]
    M. Dasgupta, A. Fregoso, S. Marzani and G.P. Salam, Towards an understanding of jet substructure, JHEP09 (2013) 029 [arXiv:1307.0007] [INSPIRE].
  55. [55]
    M. Cacciari, G.P. Salam and G. Soyez, The catchment area of jets, JHEP04 (2008) 005 [arXiv:0802.1188] [INSPIRE].
  56. [56]
    J. Casalderrey-Solana, Y. Mehtar-Tani, C.A. Salgado and K. Tywoniuk, New picture of jet quenching dictated by color coherence, Phys. Lett.B 725 (2013) 357 [arXiv:1210.7765] [INSPIRE].
  57. [57]
    C. Frye, A.J. Larkoski, J. Thaler and K. Zhou, Casimir meets Poisson: improved quark/gluon discrimination with counting observables, JHEP09 (2017) 083 [arXiv:1704.06266] [INSPIRE].
  58. [58]
    R. Baier, Y.L. Dokshitzer, A.H. Mueller and D. Schiff, Radiative energy loss of high-energy partons traversing an expanding QCD plasma, Phys. Rev.C 58 (1998) 1706 [hep-ph/9803473] [INSPIRE].
  59. [59]
    B.G. Zakharov, Quark energy loss in an expanding quark gluon plasma, in the proceedings of QCD and high energy hadronic interactions, 33rdRencontres de Moriond, March 21–28, Les Arcs, France (1998), hep-ph/9807396 [INSPIRE].
  60. [60]
    P.B. Arnold, Simple formula for high-energy gluon Bremsstrahlung in a finite, expanding medium, Phys. Rev.D 79 (2009) 065025 [arXiv:0808.2767] [INSPIRE].
  61. [61]
    E. Iancu, P. Taels and B. Wu, Jet quenching parameter in an expanding QCD plasma, Phys. Lett.B 786 (2018) 288 [arXiv:1806.07177] [INSPIRE].
  62. [62]
    CMS collaboration, Modification of jet shapes in PbPb collisions at \( \sqrt{{}^s\mathrm{NN}} \) = 2.76 TeV, Phys. Lett.B 730 (2014) 243 [arXiv:1310.0878] [INSPIRE].
  63. [63]
    ATLAS collaboration, Observation of a centrality-dependent dijet asymmetry in lead-lead collisions at \( \sqrt{{}^s\mathrm{NN}} \) = 2.77 TeV with the ATLAS detector at the LHC, Phys. Rev. Lett.105 (2010) 252303 [arXiv:1011.6182] [INSPIRE].
  64. [64]
    CMS collaboration, Observation and studies of jet quenching in PbPb collisions at nucleon-nucleon center-of-mass energy = 2.76 TeV, Phys. Rev.C 84 (2011) 024906 [arXiv:1102.1957] [INSPIRE].
  65. [65]
    CMS collaboration, Correlations between jets and charged particles in PbPb and pp collisions at \( \sqrt{{}^s\mathrm{NN}} \) = 2.76 TeV, JHEP02 (2016) 156 [arXiv:1601.00079] [INSPIRE].
  66. [66]
    K. Kutak, W. P-laczek and R. Straka, Solutions of evolution equations for medium-induced QCD cascades, Eur. Phys. J.C 79 (2019) 317 [arXiv:1811.06390] [INSPIRE].
  67. [67]
    A. Kurkela and Y. Zhu, Isotropization and hydrodynamization in weakly coupled heavy-ion collisions, Phys. Rev. Lett.115 (2015) 182301 [arXiv:1506.06647] [INSPIRE].
  68. [68]
    JETSCAPE collaboration, Multistage Monte-Carlo simulation of jet modification in a static medium, Phys. Rev.C 96 (2017) 024909 [arXiv:1705.00050] [INSPIRE].
  69. [69]
    J.H. Putschke et al., The JETSCAPE framework, arXiv:1903.07706 [INSPIRE].
  70. [70]
    B. Schenke, C. Gale and S. Jeon, MARTINI: an event generator for relativistic heavy-ion collisions, Phys. Rev.C 80 (2009) 054913 [arXiv:0909.2037] [INSPIRE].
  71. [71]
    K.C. Zapp, J. Stachel and U.A. Wiedemann, A local Monte Carlo framework for coherent QCD parton energy loss, JHEP07 (2011) 118 [arXiv:1103.6252] [INSPIRE].
  72. [72]
    K.C. Zapp, F. Krauss and U.A. Wiedemann, A perturbative framework for jet quenching, JHEP03 (2013) 080 [arXiv:1212.1599] [INSPIRE].

Copyright information

© The Author(s) 2019

Authors and Affiliations

  1. 1.Institut de Physique ThéoriqueUniversité Paris-SaclayGif-sur-YvetteFrance

Personalised recommendations