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| CMS-PAS-HIN-18-018 | ||
| Study of quark- and gluon-like jet fractions using jet charge in PbPb and pp collisions at 5.02 TeV | ||
| CMS Collaboration | ||
| November 2019 | ||
| Abstract: The momentum-weighted sum of the electric charges of particles inside a jet, known as jet charge, is sensitive to the charge of the particle initiating the parton shower. This note presents jet charge distributions in 5.0 TeV PbPb and pp collisions recorded by the CMS detector at the LHC. These data correspond to integrated luminosities of 404 $\mu$b$^{-1}$ and 27.4 pb$^{-1}$ for PbPb and pp collisions, respectively. The measurements are unfolded to account for detector and background effects. Leveraging the jet charge's sensitivity to fundamental differences in the electric charges of quarks and gluons, a template-fitting method is proposed to estimate the quark- and gluon-like jet fractions of an inclusive jet sample. Using the jet charge distributions from simulated events as templates, the quark and gluon jet fractions are extracted from data. The modification of these jet fractions is examined by comparing PbPb and pp data as a function of collision centrality. This measurement tests the color charge dependence of jet energy loss due to interactions with the quark-gluon plasma. | ||
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CDS record (PDF) ;
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These preliminary results are superseded in this paper, JHEP 07 (2020) 115. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
(Top) Unfolded jet charge measurements shown for inclusive jets in data along with the extracted fractions of up and down quark jets, gluon jets, and the heavy and antiquark jets (collectively grouped as "other flavors"). The systematic uncertainties on the distributions are shown in shaded regions around the measurements. The jet charge measurements shown here are for $\kappa = $ 0.5 and a minimum track ${p_{\mathrm {T}}}$ of 1 GeV. (Bottom) Ratio of the jet charge measurements to the results of template fits. |
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Figure 2:
The standard deviation of the jet charge distributions with different track $ {p_{\mathrm {T}}} $ cuts and $\kappa $ values for pp collisions and in the various event centrality bins for PbPb collisions compared with PYTHIA + HYDJET. |
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Figure 3:
Fitting results for the extraction of gluon-like jet fractions in pp and PbPb data shown for different minimum track $ {p_{\mathrm {T}}} $ values and for different event centrality bins in PbPb. The systematic uncertainties are shown by shaded regions and the statistical uncertainties are shown by vertical bars. |
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Figure 4:
Fitting results for the extraction of gluon-like jet fractions in pp and PbPb data shown for $\kappa $ values of 0.3, 0.5 and 0.7 in different event centrality bins in PbPb. The markers for track $ {p_{\mathrm {T}}} > $ 1 GeV and track $ {p_{\mathrm {T}}} > $ 2 GeV have been separated horizontally for clarity. The systematic uncertainties are shown by shaded regions and the statistical uncertainties are shown by vertical bars. |
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Figure 5:
(Top) Unfolded jet charge measurements shown for inclusive jets in data along with the extracted fractions of up and down quark jets, gluon jets, and the heavy and antiquark jets (collectively grouped as "other flavors"). The systematic uncertainties on the distributions are shown in shaded regions around the measurements. The jet charge measurements shown here are for $\kappa = $ 0.5 and a minimum track ${p_{\mathrm {T}}}$ of 2 GeV, 4 GeV and 5 GeV. (Bottom) Ratio of the jet charge measurements to the results of template fits. |
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Figure 5-a:
(Top) Unfolded jet charge measurements shown for inclusive jets in data along with the extracted fractions of up and down quark jets, gluon jets, and the heavy and antiquark jets (collectively grouped as "other flavors"). The systematic uncertainties on the distributions are shown in shaded regions around the measurements. The jet charge measurements shown here are for $\kappa = $ 0.5 and a minimum track ${p_{\mathrm {T}}}$ of 2 GeV. (Bottom) Ratio of the jet charge measurements to the results of template fits. |
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Figure 5-b:
(Top) Unfolded jet charge measurements shown for inclusive jets in data along with the extracted fractions of up and down quark jets, gluon jets, and the heavy and antiquark jets (collectively grouped as "other flavors"). The systematic uncertainties on the distributions are shown in shaded regions around the measurements. The jet charge measurements shown here are for $\kappa = $ 0.5 and a minimum track ${p_{\mathrm {T}}}$ of 4 GeV. (Bottom) Ratio of the jet charge measurements to the results of template fits. |
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Figure 5-c:
(Top) Unfolded jet charge measurements shown for inclusive jets in data along with the extracted fractions of up and down quark jets, gluon jets, and the heavy and antiquark jets (collectively grouped as "other flavors"). The systematic uncertainties on the distributions are shown in shaded regions around the measurements. The jet charge measurements shown here are for $\kappa = $ 0.5 and a minimum track ${p_{\mathrm {T}}}$ of 5 GeV. (Bottom) Ratio of the jet charge measurements to the results of template fits. |
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Figure 6:
(Top) Unfolded jet charge measurements shown for inclusive jets in data along with the extracted fractions of up and down quark jets, gluon jets, and the heavy and antiquark jets (collectively grouped as "other flavors"). The systematic uncertainties on the distributions are shown in shaded regions around the measurements. The jet charge measurements shown here are for $\kappa = $ 0.3, $\kappa = $ 0.5 and $\kappa = $ 0.7 and a minimum track ${p_{\mathrm {T}}}$ of 1 GeV. (Bottom) Ratio of the jet charge measurements to the results of template fits. |
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Figure 6-a:
(Top) Unfolded jet charge measurements shown for inclusive jets in data along with the extracted fractions of up and down quark jets, gluon jets, and the heavy and antiquark jets (collectively grouped as "other flavors"). The systematic uncertainties on the distributions are shown in shaded regions around the measurements. The jet charge measurements shown here are for $\kappa = $ 0.3 and a minimum track ${p_{\mathrm {T}}}$ of 1 GeV. (Bottom) Ratio of the jet charge measurements to the results of template fits. |
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Figure 6-b:
(Top) Unfolded jet charge measurements shown for inclusive jets in data along with the extracted fractions of up and down quark jets, gluon jets, and the heavy and antiquark jets (collectively grouped as "other flavors"). The systematic uncertainties on the distributions are shown in shaded regions around the measurements. The jet charge measurements shown here are for $\kappa = $ 0.5 and a minimum track ${p_{\mathrm {T}}}$ of 1 GeV. (Bottom) Ratio of the jet charge measurements to the results of template fits. |
png pdf |
Figure 6-c:
(Top) Unfolded jet charge measurements shown for inclusive jets in data along with the extracted fractions of up and down quark jets, gluon jets, and the heavy and antiquark jets (collectively grouped as "other flavors"). The systematic uncertainties on the distributions are shown in shaded regions around the measurements. The jet charge measurements shown here are for $\kappa = $ 0.7 and a minimum track ${p_{\mathrm {T}}}$ of 1 GeV. (Bottom) Ratio of the jet charge measurements to the results of template fits. |
png pdf |
Figure 7:
(Top) Unfolded jet charge measurements shown for inclusive jets in data along with the extracted fractions of up and down quark jets, gluon jets, and the heavy and antiquark jets (collectively grouped as "other flavors"). The systematic uncertainties on the distributions are shown in shaded regions around the measurements. The jet charge measurements shown here are for $\kappa = $ 0.3, $\kappa = $ 0.5 and $\kappa = $ 0.7 and a minimum track ${p_{\mathrm {T}}}$ of 2 GeV. (Bottom) Ratio of the jet charge measurements to the results of template fits. |
png pdf |
Figure 7-a:
(Top) Unfolded jet charge measurements shown for inclusive jets in data along with the extracted fractions of up and down quark jets, gluon jets, and the heavy and antiquark jets (collectively grouped as "other flavors"). The systematic uncertainties on the distributions are shown in shaded regions around the measurements. The jet charge measurements shown here are for $\kappa = $ 0.3 and a minimum track ${p_{\mathrm {T}}}$ of 2 GeV. (Bottom) Ratio of the jet charge measurements to the results of template fits. |
png pdf |
Figure 7-b:
(Top) Unfolded jet charge measurements shown for inclusive jets in data along with the extracted fractions of up and down quark jets, gluon jets, and the heavy and antiquark jets (collectively grouped as "other flavors"). The systematic uncertainties on the distributions are shown in shaded regions around the measurements. The jet charge measurements shown here are for $\kappa = $ 0.5 and a minimum track ${p_{\mathrm {T}}}$ of 2 GeV. (Bottom) Ratio of the jet charge measurements to the results of template fits. |
png pdf |
Figure 7-c:
(Top) Unfolded jet charge measurements shown for inclusive jets in data along with the extracted fractions of up and down quark jets, gluon jets, and the heavy and antiquark jets (collectively grouped as "other flavors"). The systematic uncertainties on the distributions are shown in shaded regions around the measurements. The jet charge measurements shown here are for $\kappa = $ 0.7 and a minimum track ${p_{\mathrm {T}}}$ of 2 GeV. (Bottom) Ratio of the jet charge measurements to the results of template fits. |
| Tables | |
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Table 1:
Relative systematic uncertainties in percentage for the measurements of gluon-like jet fractions in PbPb and pp events. The PbPb results are given in intervals of centrality. When an uncertainty range is given, the range of the values are the maximum variation in the relative fractions for different selections of $\kappa $ and track $ {p_{\mathrm {T}}} $ threshold values. |
| Summary |
| The first measurements of jet charge in PbPb collisions using data collected with the CMS detector at a nucleon-nucleon center-of-mass energy of ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV are presented. Measurements in pp collisions at the same energy are also reported. The unfolded jet charge distributions, measured using the jet constituents with transverse momentum ${p_{\mathrm{T}}} > $ 1 GeV for jets having ${p_{\mathrm{T}}} > $ 120 GeV and $|\eta| < $ 1.5, are presented. The width of the jet charge distributions for pp collisions and in different event centrality bins for PbPb collisions are shown to be independent of collision centrality and are in good agreement with measurements from PYTHIA and PYTHIA+ HYDJET. The jet charge distributions for quark- and gluon-initiated jets from PYTHIA and PYTHIA+ HYDJET are used as fitting templates to estimate the respective contributions in the measured jet samples. The gluon-like jet fractions extracted from these template fits are found to be similar between pp and all studied PbPb centrality ranges. No evidence is seen for a significant decrease in gluon prevalence due to jet quenching in PbPb collisions in the sample of inclusive jets with ${p_{\mathrm{T}}} > $ 120 GeV, contrary to expectations of some jet quenching models. |
| References | ||||
| 1 | J. D. Bjorken | Energy loss of energetic partons in QGP: possible extinction of high $ {p_{\mathrm{T}}} $ jets in hadron-hadron collisions | FERMILAB-PUB-82-059-THY | |
| 2 | J. C.-S. . C. A. Salgado | Introductory lectures on jet quenching in heavy ion collisions | in Theoretical physics. Proceedings, 47th Cracow School, Zakopane, Poland, June 14-22, 2007, p. 3661 2007 | 0712.3443 |
| 3 | A. Majumder and M. Van Leeuwen | The Theory and Phenomenology of Perturbative QCD Based Jet Quenching | Prog. Part. NP 66 (2011) 41 | 1002.2206 |
| 4 | STAR Collaboration | Direct observation of dijets in central Au+Au collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 200 GeV | PRL 97 (2006) 162301 | nucl-ex/0604018 |
| 5 | ATLAS Collaboration | Observation of a centrality-dependent dijet asymmetry in Lead-Lead collisions at $ {{\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = 2.76 TeV} $ with the ATLAS detector at the LHC | PRL 105 (2010) 252303 | 1011.6182 |
| 6 | CMS Collaboration | Observation and studies of jet quenching in PbPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 2.76 TeV | PRC 84 (2011) 024906 | CMS-HIN-10-004 1102.1957 |
| 7 | CMS Collaboration | Jet momentum dependence of jet quenching in PbPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}}= $ 2.76 TeV | PLB 712 (2012) 176 | CMS-HIN-11-013 1202.5022 |
| 8 | ALICE Collaboration | Measurement of jet suppression in central Pb-Pb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 2.76 TeV | PLB 746 (2015) 1 | 1502.01689 |
| 9 | PHENIX Collaboration | Transverse momentum and centrality dependence of dihadron correlations in Au+Au collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 200 GeV: Jet-quenching and the response of partonic matter | PRC 77 (2008) 011901 | 0705.3238 |
| 10 | CMS Collaboration | Jet properties in PbPb and pp collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV | JHEP 06 (2018) 124151 | CMS-HIN-16-020 1803.00042 |
| 11 | M. Spousta and B. Cole | Interpreting single jet measurements in Pb+Pb collisions at the LHC | EPJC 76 (2016), no. 2, 50 | |
| 12 | ALICE Collaboration | Exploration of jet substructure using iterative declustering in pp and Pb-Pb collisions at LHC energies | Submitted to PRLett | 1905.02512 |
| 13 | R. D. Field and R. P. Feynman | A parametrization of the properties of quark jets | NPB. 136 (1978) 76 | |
| 14 | Fermilab--Serpukhov--Moscow--Michigan Collaboration | Net charge in deep inelastic antineutrino-nucleon scattering | PLB 91 (1980) 311 | |
| 15 | Fermilab--Serpukhov--Moscow--Michigan Collaboration | Quark jets from antineutrino interactions (I). net charge and factorization in the quark jets | NPB 184 (1981) 13 | |
| 16 | Aachen--Bonn--CERN--Munich--Oxford Collaboration | Multiplicity distributions in neutrino-hydrogen interactions | NPB 181 (1981) 385 | |
| 17 | Aachen--Bonn--CERN--Munich--Oxford Collaboration | Charge properties of the hadronic system in $ \nu p $ and $ \overline{\nu}p $ interactions | PLB 112 (1982) 88 | |
| 18 | European Muon Collaboration | Quark charge retention in final state hadrons from deep inelastic muon scattering | PLB 144 (1984) 302 | |
| 19 | Amsterdam--Bologna--Padua--Pisa--Saclay--Turin Collaboration | Charged hadron multiplicities in high-energy $ \overline{\nu}_{\mu} n $ and $ \overline{\nu}_{\mu} p $ interactions | Z. Phys. C 11 (1982) 283, .[Erratum: \DOI10.1007/BF01571828] | |
| 20 | R. Erickson et al. | Charge retention in deep-inelastic electroproduction | PRL 42 (1979) 822, .[Erratum: \DOI10.1103/PhysRevLett.42.1246] | |
| 21 | W. J. Waalewijn | Calculating the charge of a jet | PRD 86 (2012) 094030 | 1209.3019 |
| 22 | S.-Y. Chen, B.-W. Zhang, and E.-K. Wang | Jet charge in high energy nuclear collisions | 1908.01518 | |
| 23 | H. T. Li and I. Vitev | Jet charge modification in dense QCD matter | 1908.06979 | |
| 24 | D. Krohn, M. D. Schwartz, T. Lin, and W. J. Waalewijn | Jet charge at the LHC | PRL 110 (2013) 212001 | 1209.2421 |
| 25 | CMS Collaboration | Measurement of jet fragmentation in PbPb and pp collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}}= $ 2.76 TeV | PRC 90 (2014) 024908 | CMS-HIN-12-013 1406.0932 |
| 26 | CMS Collaboration | Long-range and short-range dihadron angular correlations in central PbPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 2.76 TeV | JHEP 11 (2011), no. 7, 76 | CMS-HIN-11-001 1105.2438 |
| 27 | CMS Collaboration | Decomposing transverse momentum balance contributions for quenched jets in PbPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 2.76 TeV | JHEP 16 (2016), no. 11, 55 | CMS-HIN-15-011 1609.02466 |
| 28 | CMS Collaboration | Correlations between jets and charged particles in PbPb and pp collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 2.76 TeV | JHEP 16 (2016), no. 2, 156 | CMS-HIN-14-016 1601.00079 |
| 29 | CMS Collaboration | Determination of jet energy calibration and transverse momentum resolution in CMS | JINST 6 (2011) P11002 | CMS-JME-10-011 1107.4277 |
| 30 | CMS Collaboration | Description and performance of track and primary-vertex reconstruction with the CMS tracker | JINST 9 (2014) P10009 | CMS-TRK-11-001 1405.6569 |
| 31 | CMS Collaboration | The CMS experiment at the CERN LHC | JINST 3 (2008) S08004 | CMS-00-001 |
| 32 | M. Cacciari, G. P. Salam, and G. Soyez | The anti-$ {k_{\mathrm{T}}} $ jet clustering algorithm | JHEP 04 (2008) 063 | 0802.1189 |
| 33 | CMS Collaboration | The CMS trigger system | JINST 12 (2017), no. 01, P01020 | CMS-TRG-12-001 1609.02366 |
| 34 | CMS Collaboration | Charged particle nuclear modification factors in PbPb and pPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV | JHEP 04 (2017) 039 | CMS-HIN-15-015 1611.01664 |
| 35 | T. Sjostrand, S. Mrenna, and P. Skands | PYTHIA 6.4 physics and manual | JHEP 05 (2006) 026 | hep-ph/0603175 |
| 36 | R. Field | Early LHC underlying event data---findings and surprises | in Hadron collider physics. Proceedings, 22nd Conference, HCP 2010, Toronto, Canada 2010 | 1010.3558 |
| 37 | I. P. Lokhtin and A. M. Snigirev | A model of jet quenching in ultrarelativistic heavy ion collisions and high-$ p_{\rm T} $ hadron spectra at RHIC | EPJC 45 (2006) 211 | hep-ph/0506189 |
| 38 | GEANT4 Collaboration | GEANT4---a simulation toolkit | NIMA 506 (2003) 250 | |
| 39 | M. Cacciari, G. P. Salam, and G. Soyez | FastJet user manual | EPJC 72 (2012) 1896 | 1111.6097 |
| 40 | M. Cacciari and G. P. Salam | Pileup subtraction using jet areas | PLB 659 (2008) 119 | 0707.1378 |
| 41 | O. Kodolova, I. Vardanian, A. Nikitenko, and A. Oulianov | The performance of the jet identification and reconstruction in heavy ions collisions with CMS detector | EPJC 50 (2007) 117 | |
| 42 | CMS Collaboration | Study of high-$ p_{\rm T} $ charged particle suppression in PbPb compared to pp collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 2.76 TeV | EPJC 72 (2012) 1945 | CMS-HIN-10-005 1202.2554 |
| 43 | CMS Collaboration | Modification of jet shapes in PbPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 2.76 TeV | PLB 730 (2014) 243 | CMS-HIN-12-002 1310.0878 |
| 44 | CMS Collaboration | Particle-flow reconstruction and global event description with the CMS detector | Journal of Instrumentation 12 (oct, 2017) P10003 | |
| 45 | G. D'Agostini | A multidimensional unfolding method based on Bayes' theorem | NIMA 362 (1995) 487 | |
| 46 | W. H. Richardson | Bayesian-based iterative method of image restoration | Opt. Soc. Am. 62 (1972) 55 | |
| 47 | L. B. Lucy | An iterative technique for the rectification of observed distributions | Astron. J. 79 (1974) 745 | |
| 48 | T. Adye | Unfolding algorithms and tests using RooUnfold | in Proceedings of the PHYSTAT 2011 Workshop, CERN, Geneva, Switzerland, January 2011, CERN-2011-006, p. 313 2011 | 1105.1160 |
| 49 | CMS Collaboration | Measurement of transverse momentum relative to dijet systems in PbPb and pp collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 2.76 TeV | JHEP 01 (2016) 6 | CMS-HIN-14-010 1509.09029 |
| 50 | CMS Collaboration | Determination of jet energy calibration and transverse momentum resolution in CMS | Journal of Instrumentation 06 (2011) P11002 | |
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