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| CMS-HIN-16-020 ; CERN-EP-2018-011 | ||
| Jet properties in PbPb and pp collisions at $\sqrt{\smash[b]{s_{\mathrm{NN}}}} = $ 5.02 TeV | ||
| CMS Collaboration | ||
| 28 February 2018 | ||
| JHEP 05 (2018) 006 | ||
| Abstract: Modifications of the properties of jets in PbPb collisions, relative to those in pp collisions, are studied at a nucleon-nucleon center-of-mass energy of $\sqrt{\smash[b]{s_{\mathrm{NN}}}} = $ 5.02 TeV via correlations of charged particles with the jet axis in relative pseudorapidity ($\Delta \eta$), relative azimuth ($\Delta \phi$), and relative angular distance from the jet axis ${\Delta \mathrm{r}} = \sqrt{\smash[b]{(\Delta\eta)^{2}+(\Delta\phi)^{2}}}$. This analysis uses data collected with the CMS detector at the LHC, corresponding to integrated luminosities of 404 $\mu$b$^{-1}$ and 27.4 pb$^{-1}$ for PbPb and pp collisions, respectively. Charged particle number densities, jet fragmentation functions, and jet shapes are presented as a function of PbPb collision centrality and charged-particle track transverse momentum, providing a differential description of jet modifications due to interactions with the quark-gluon plasma. | ||
| Links: e-print arXiv:1803.00042 [nucl-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; | ||
| Figures & Tables | Summary | Additional Figures | References | CMS Publications |
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| Figures | |
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Figure 1:
The distribution of jet-correlated charged-particle tracks with $ | \Delta \phi | < $ 1.0 as a function of $\Delta \eta $ in pp (top left) and PbPb (middle row) collisions. The PbPb results are shown for different centrality regions. The bottom row shows the difference between the PbPb and pp data. The intervals in $ {p_{\mathrm {T}}^{\text {trk}}} $ are indicated by the stacked histograms. The inclusive points (0.7 $ < {p_{\mathrm {T}}^{\text {trk}}} < $ 20 GeV) are shown by open white circles. The grey bands surrounding these points show the total systematic uncertainties. |
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Figure 2:
The distribution of jet-correlated charged-particle tracks with $ | \Delta \eta | < $ 1.0 as a function of $\Delta \phi $ in pp (top left) and PbPb (middle row) collisions. The PbPb results are shown for different centrality regions. The bottom row shows the difference between the PbPb and pp data. The intervals in $ {p_{\mathrm {T}}^{\text {trk}}} $ are indicated by the stacked histograms. The inclusive points (0.7 $ < {p_{\mathrm {T}}^{\text {trk}}} < $ 20 GeV) are shown by open white circles. The grey bands surrounding these points show the total systematic uncertainties. |
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Figure 3:
The distribution of jet-correlated charged-particle tracks as a function of $ {\Delta \mathrm {r}} $ in pp (top left) and PbPb (middle row) collisions. The PbPb results are shown for different centrality regions. The bottom row shows the difference between the PbPb and pp data. The intervals in $ {p_{\mathrm {T}}^{\text {trk}}} $ are indicated by the stacked histograms. The inclusive points (0.7 $ < {p_{\mathrm {T}}^{\text {trk}}} < $ 20 GeV) are shown by open white circles. The grey bands surrounding these points show the total systematic uncertainties. |
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Figure 4:
The distribution of jet-correlated charged-particle tracks with $ {\Delta \mathrm {r}} < $ 1 (top row) as a function of $ {p_{\mathrm {T}}^{\text {trk}}} $ in PbPb and pp collisions. The PbPb results are shown for different centrality regions. Statistical uncertainties are shown by the vertical error bars and systematic uncertainties by the shaded boxes. The corresponding results for the difference between the PbPb and pp data are shown in the bottom row, with the analogous difference observed at 2.76 TeV [13]. |
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Figure 5:
The radial jet momentum distribution $ {\mathrm {P}(\Delta \mathrm {r})} $ of jets in pp (top left) and PbPb (middle row) collisions. The PbPb results are shown for different centrality regions. The bottom row shows the ratio between PbPb and pp data for the indicated intervals of $ {p_{\mathrm {T}}^{\text {trk}}} $. The shaded bands show the total systematic uncertainties. |
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Figure 6:
The jet shape $\rho ({\Delta \mathrm {r}})$ in pp (top left) and PbPb (middle row) collisions. The PbPb results are shown for different centrality regions. The bottom row shows the ratio between the PbPb and pp data for the inclusive range 0.7 $ < {p_{\mathrm {T}}^{\text {trk}}} < $ 300 GeV. The shaded band in the ratio plots shows the total systematic uncertainty. |
| Tables | |
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Table 1:
Systematic uncertainties in percentage for the measurements of the jet-track correlations in PbPb and pp events. The PbPb results are given in intervals of centrality. Where an uncertainty range is given, the upper edge of the range corresponds to the bin with the smallest $ {p_{\mathrm {T}}^{\text {trk}}} $ values. |
| Summary |
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In this paper, measurements are presented of the modifications to charged-particle track yields and jet shapes in PbPb collisions with respect to pp collisions using data collected with the CMS detector at the LHC at a nucleon-nucleon center-of-mass energy of $\sqrt{\smash[b]{s_{\mathrm{NN}}}} = $ 5.02 TeV. The correlations of charged particles having transverse momentum ${p_{\mathrm{T}}}trk > $ 0.7 GeV and pseudorapidity $ | {\eta} | < $ 2.4 with the jet axis of jets having ${p_{\mathrm{T}}} > $ 120 GeV and $ | {\eta} | < $ 1.6 are studied. Charged particle yields associated with jets are shown as a function of relative angular distance ${\Delta \mathrm{r}} = \sqrt{\smash[b]{(\Delta\eta)^{2}+(\Delta\phi)^{2}}}$ from the jet axis, as well as individually in $\Delta\eta$ and $\Delta\phi$. In these studies, a strong enhancement of tracks with ${p_{\mathrm{T}}}trk < $ 3 GeV, extending to large angles, is found in PbPb collisions with respect to pp collisions. This low $ {p_{\mathrm{T}}} $ excess remains correlated with the jet axis, but the distribution is broader in PbPb than that observed in the corresponding $ {p_{\mathrm{T}}} $ bin of pp collisions, which could indicate additional in-medium gluon radiation and/or a medium backreaction, i.e., a wake-like response of the QGP to the propagating parton. For PbPb events with centrality 0-10%, the correlated yield is increased relative to pp collisions at low $ {p_{\mathrm{T}}} $ by up to a factor of two. In addition to these charged-particle yields, we examine the jet transverse momentum profile ${\mathrm{P}(\Delta\mathrm{r})} $ and the jet shape $\rho({\Delta \mathrm{r}} )$ variables, defined using the distribution of charged-particle tracks in annular rings around the jet axis, with each particle weighted by its $ {p_{\mathrm{T}}}^{\text{trk}} $ value. A redistribution of energy from small to large angles from the jet axis is observed for PbPb relative to pp events, with the most pronounced effect seen for central collisions. The energy flow within the jet is modified by shifting the momentum away from the jet axis out to large relative angular distances such that in central PbPb collisions, the ratio of the jet shapes in PbPb to pp collisions approaches a value of two. These measurements provide a comprehensive picture of the modifications of the parton shower evolution and the quark-gluon plasma response to the propagating jets in 5 TeV PbPb collisions. |
| Additional Figures | |
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Additional Figure 1:
The ratio of the radial jet momentum distribution $ {\mathrm {P}(\Delta \mathrm {r})} $ of jets between PbPb and pp collisions for the indicated intervals of ${p_{\mathrm {T}}^{\text {trk}}}$ shown for the 0-10% (most central) bin. The shaded bands show the total systematic uncertainties. |
| 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 | 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 |
| 3 | 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 |
| 4 | 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 |
| 5 | 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 |
| 6 | 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 |
| 7 | 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 |
| 8 | 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 |
| 9 | ATLAS Collaboration | Measurement of inclusive jet charged-particle fragmentation functions in Pb+Pb collisions at $ \sqrt{\smash[b]{s_{\mathrm{NN}}}}= $ 2.76 TeV with the ATLAS detector | PLB 739 (2014) 320 | 1406.2979 |
| 10 | 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 |
| 11 | M. Cacciari, G. P. Salam, and G. Soyez | FastJet user manual | EPJC 72 (2012) 1896 | 1111.6097 |
| 12 | 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 |
| 13 | CMS Collaboration | Correlations between jets and charged particles in PbPb and pp collisions at $ \sqrt{\smash[b]{s_{\mathrm{NN}}}} = $ 2.76 TeV | JHEP 02 (2016) 156 | CMS-HIN-14-016 1601.00079 |
| 14 | CMS Collaboration | Decomposing transverse momentum balance contributions for quenched jets in PbPb collisions at $ \sqrt{\smash[b]{s_{\mathrm{NN}}}}= $ 2.76 TeV | JHEP 11 (2016) 055 | CMS-HIN-15-011 1609.02466 |
| 15 | L. Apolinario, N. Armesto, and L. Cunqueiro | An analysis of the influence of background subtraction and quenching on jet observables in heavy-ion collisions | JHEP 02 (2013) 022 | 1211.1161 |
| 16 | A. Ayala, I. Dominguez, J. Jalilian-Marian, and M. E. Tejeda-Yeomans | Jet asymmetry and momentum imbalance from $ 2 \to 2 $ and $ 2 \to 3 $ partonic processes in relativistic heavy-ion collisions | PRC 92 (2015) 044902 | 1503.06889 |
| 17 | J.-P. Blaizot, Y. Mehtar-Tani, and M. A. C. Torres | Angular structure of the in-medium QCD cascade | PRL 114 (2015) 222002 | 1407.0326 |
| 18 | M. A. Escobedo and E. Iancu | Event-by-event fluctuations in the medium-induced jet evolution | JHEP 05 (2016) 008 | 1601.03629 |
| 19 | J. Casalderrey-Solana et al. | Angular structure of jet quenching within a hybrid strong/weak coupling model | JHEP 03 (2017) 135 | 1609.05842 |
| 20 | JET Collaboration | Extracting the jet transport coefficient from jet quenching in high-energy heavy-ion collisions | PRC 90 (2014) 014909 | 1312.5003 |
| 21 | CMS Collaboration | Determination of jet energy calibration and transverse momentum resolution in CMS | JINST 6 (2011) P11002 | CMS-JME-10-011 1107.4277 |
| 22 | 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 |
| 23 | CMS Collaboration | The CMS experiment at the CERN LHC | JINST 3 (2008) S08004 | CMS-00-001 |
| 24 | M. Cacciari, G. P. Salam, and G. Soyez | The anti-$ {k_{\mathrm{T}}} $ jet clustering algorithm | JHEP 04 (2008) 063 | 0802.1189 |
| 25 | CMS Collaboration | Dependence on pseudorapidity and centrality of charged hadron production in PbPb collisions at a nucleon-nucleon centre-of-mass energy of 2.76 TeV | JHEP 08 (2011) 141 | CMS-HIN-10-001 1107.4800 |
| 26 | T. Sjostrand, S. Mrenna, and P. Skands | PYTHIA 6.4 physics and manual | JHEP 05 (2006) 026 | hep-ph/0603175 |
| 27 | R. Field | Early LHC underlying event data---findings and surprises | in Hadron collider physics. Proceedings, 22nd Conference, HCP 2010, Toronto, Canada 2010 | 1010.3558 |
| 28 | GEANT4 Collaboration | GEANT4---a simulation toolkit | NIMA 506 (2003) 250 | |
| 29 | 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 |
| 30 | 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 | |
| 31 | 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 |
| 32 | CMS Collaboration | Charged particle nuclear modification factors in PbPb and pPb collisions at $ \sqrt{\smash[b]{s_{\mathrm{NN}}}} = $ 5.02 TeV | JHEP 04 (2016) 039 | CMS-HIN-15-015 1611.01664 |
| 33 | CMS Collaboration | Observation of long-range, near-side angular correlations in proton-proton collisions at the LHC | JHEP 09 (2010) 091 | CMS-QCD-10-002 1009.4122 |
| 34 | CMS Collaboration | Long-range and short-range dihadron angular correlations in central PbPb collisions at a nucleon-nucleon center of mass energy of 2.76 TeV | JHEP 07 (2011) 076 | CMS-HIN-11-001 1105.2438 |
| 35 | CMS Collaboration | Observation of long-range, near-side angular correlations in pPb collisions at the LHC. | PLB 718 (2013) 795 | CMS-HIN-12-015 1210.5482 |
| 36 | CMS Collaboration | Multiplicity and transverse momentum dependence of two- and four-particle correlations in pPb and PbPb collisions | PLB 724 (2013) 213 | CMS-HIN-13-002 1305.0609 |
| 37 | CMS Collaboration | Measurement of jet fragmentation into charged particles in pp and PbPb collisions at $ \sqrt{\smash[b]{s_{\mathrm{NN}}}}= $ 2.76 TeV | JHEP 10 (2012) 087 | CMS-HIN-11-004 1205.5872 |
| 38 | G.-Y. Q. Yasuki Tachibana, Ning-Bo Chang | Full jet in quark-gluon plasma with hydrodynamic medium response | PRC 95 (2017) 044909 | 1701.07951 |
| 39 | I. Vitev, S. Wicks, and B. W. Zhang | A theory of jet shapes and cross sections: from hadrons to nuclei | JHEP 93 (2008) 0811 | 0810.2807 |
| 40 | Y.-T. Chien and I. Vitev | Towards the understanding of jet shapes and cross sections in heavy ion collisions using soft-collinear effective field theory | JHEP 05 (2016) 023 | 1509.07257 |
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