Skip to main content

Jet fragmentation transverse momentum measurements from di-hadron correlations in \( \sqrt{\mathrm{s}}=7 \) TeV pp and \( \sqrt{s_{\mathrm{NN}}}=5.02 \) TeV p–Pb collisions

A preprint version of the article is available at arXiv.


The transverse structure of jets was studied via jet fragmentation transverse momentum (jT) distributions, obtained using two-particle correlations in proton-proton and proton-lead collisions, measured with the ALICE experiment at the LHC. The highest transverse momentum particle in each event is used as the trigger particle and the region 3 < pTt < 15GeV/c is explored in this study. The measured distributions show a clear narrow Gaussian component and a wide non-Gaussian one. Based on Pythia simulations, the narrow component can be related to non-perturbative hadronization and the wide component to quantum chromodynamical splitting. The width of the narrow component shows a weak dependence on the transverse momentum of the trigger particle, in agreement with the expectation of universality of the hadronization process. On the other hand, the width of the wide component shows a rising trend suggesting increased branching for higher transverse momentum. The results obtained in pp collisions at \( \sqrt{s}=7 \) TeV and in p–Pb collisions at \( \sqrt{s_{\mathrm{NN}}}=5.02 \) TeV are compatible within uncertainties and hence no significant cold nuclear matter effects are observed. The results are compared to previous measurements from CCOR and PHENIX as well as to Pythia 8 and Herwig 7 simulations.


  1. Y.L. Dokshitzer, V.A. Khoze, A.H. Müller and S.I. Troian, Basics of Perturbative QCD, Editions Frontiéres, Gif-sur-Yvette France (1991).

  2. T. Sjöstrand, S. Mrenna and P.Z. Skands, A Brief Introduction to PYTHIA 8.1, Comput. Phys. Commun. 178 (2008) 852 [arXiv:0710.3820] [INSPIRE].

  3. M. Bahr et al., HERWIG++ Physics and Manual, Eur. Phys. J. C 58 (2008) 639 [arXiv:0803.0883] [INSPIRE].

    ADS  Article  Google Scholar 

  4. J. Bellm et al., HERWIG 7.0/HERWIG++ 3.0 release note, Eur. Phys. J. C 76 (2016) 196 [arXiv:1512.01178] [INSPIRE].

  5. CERN-Columbia-Oxford-Rockefeller and CCOR collaborations, A Measurement of the Transverse Momenta of Partons and of Jet Fragmentation as a Function of \( \sqrt{s} \) in pp Collisions, Phys. Lett. B 97 (1980) 163 [INSPIRE].

  6. PHENIX collaboration, Jet properties from dihadron correlations in p + p collisions at \( \sqrt{s}=200 \) GeV, Phys. Rev. D 74 (2006) 072002 [hep-ex/0605039] [INSPIRE].

  7. PHENIX collaboration, Jet structure from dihadron correlations in d + Au collisions at \( {\sqrt{s}}_{\mathrm{NN}}=200 \) GeV, Phys. Rev. C 73 (2006) 054903 [nucl-ex/0510021] [INSPIRE].

  8. CDF collaboration, Measurement of the k T Distribution of Particles in Jets Produced in \( p\overline{p} \) Collisions at \( \sqrt{s}=1.96 \) TeV, Phys. Rev. Lett. 102 (2009) 232002 [arXiv:0811.2820] [INSPIRE].

  9. ATLAS collaboration, Measurement of Jets and Jet Suppression in \( \sqrt{s_{\mathrm{NN}}}=2.76 \) TeV Lead-Lead Collisions with the ATLAS detector at the LHC, J. Phys. G 38 (2011) 124085 [arXiv:1108.5191] [INSPIRE].

  10. A. Buckley et al., General-purpose event generators for LHC physics, Phys. Rept. 504 (2011) 145 [arXiv:1101.2599] [INSPIRE].

    ADS  Article  Google Scholar 

  11. R. Baier, Y.L. Dokshitzer, A.H. Mueller, S. Peigne and D. Schiff, Radiative energy loss and p T broadening of high-energy partons in nuclei, Nucl. Phys. B 484 (1997) 265 [hep-ph/9608322] [INSPIRE].

  12. L.D. McLerran and R. Venugopalan, Computing quark and gluon distribution functions for very large nuclei, Phys. Rev. D 49 (1994) 2233 [hep-ph/9309289] [INSPIRE].

  13. K.J. Eskola, H. Paukkunen and C.A. Salgado, EPS09: A New Generation of NLO and LO Nuclear Parton Distribution Functions, JHEP 04 (2009) 065 [arXiv:0902.4154] [INSPIRE].

    ADS  Article  Google Scholar 

  14. T. Renk, Jet correlationsopportunities and pitfalls, Nucl. Phys. A 932 (2014) 334 [arXiv:1404.0793] [INSPIRE].

    ADS  Article  Google Scholar 

  15. T. Renk and K.J. Eskola, Hard dihadron correlations in heavy-ion collisions at RHIC and LHC, Phys. Rev. C 84 (2011) 054913 [arXiv:1106.1740] [INSPIRE].

    ADS  Google Scholar 

  16. ALICE collaboration, The ALICE experiment at the CERN LHC, 2008 JINST 3 S08002 [INSPIRE].

  17. ALICE collaboration, Performance of the ALICE Experiment at the CERN LHC, Int. J. Mod. Phys. A 29 (2014) 1430044 [arXiv:1402.4476] [INSPIRE].

  18. ALICE collaboration, Alignment of the ALICE Inner Tracking System with cosmic-ray tracks, 2010 JINST 5 P03003 [arXiv:1001.0502] [INSPIRE].

  19. J. Alme et al., The ALICE TPC, a large 3-dimensional tracking device with fast readout for ultra-high multiplicity events, Nucl. Instrum. Meth. A 622 (2010) 316 [arXiv:1001.1950] [INSPIRE].

    ADS  Article  Google Scholar 

  20. ALICE collaboration, Measurement of Event Background Fluctuations for Charged Particle Jet Reconstruction in Pb–Pb collisions at \( \sqrt{s_{\mathrm{NN}}}=2.76 \) TeV, JHEP 03 (2012) 053 [arXiv:1201.2423] [INSPIRE].

  21. ALICE collaboration, ALICE technical design report on forward detectors: FMD, T0 and V0, CERN-LHCC-2004-025 (2004) [INSPIRE].

  22. ALICE collaboration, Underlying Event measurements in pp collisions at \( \sqrt{s} \) = 0.9 and 7 TeV with the ALICE experiment at the LHC, JHEP 07 (2012) 116 [arXiv:1112.2082] [INSPIRE].

  23. ALICE collaboration, Long-range angular correlations on the near and away side in p–Pb collisions at \( \sqrt{s_{\mathrm{NN}}}=5.02 \) TeV, Phys. Lett. B 719 (2013) 29 [arXiv:1212.2001] [INSPIRE].

  24. T. Sjöstrand et al., An Introduction to PYTHIA 8.2, Comput. Phys. Commun. 191 (2015) 159 [arXiv:1410.3012] [INSPIRE].

  25. T. Sjöstrand, S. Mrenna and P.Z. Skands, PYTHIA 6.4 Physics and Manual, JHEP 05 (2006) 026 [hep-ph/0603175] [INSPIRE].

  26. S. Roesler, R. Engel and J. Ranft, The Monte Carlo event generator DPMJET-III, in proceedings of the International Conference on Advanced Monte Carlo for Radiation Physics, Particle Transport Simulation and Applications (MC 2000), Lisbon, Portugal, 23–26 October 2000, A. Kling, F.J.C. Baräo, M. Nakagawa, L. Távora and P. Vaz eds., Springer (2001), pp. 1033–1038 [hep-ph/0012252] [INSPIRE] and online at

  27. R. Brun et al., GEANT Detector Description and Simulation Tool, CERN-W5013 (1994) [INSPIRE].

  28. T. Sjöstrand and P.Z. Skands, Transverse-momentum-ordered showers and interleaved multiple interactions, Eur. Phys. J. C 39 (2005) 129 [hep-ph/0408302] [INSPIRE].

  29. B. Andersson, G. Gustafson, G. Ingelman and T. Sjöstrand, Parton Fragmentation and String Dynamics, Phys. Rept. 97 (1983) 31 [INSPIRE].

    ADS  Article  Google Scholar 

  30. ALICE collaboration, Energy Dependence of the Transverse Momentum Distributions of Charged Particles in pp Collisions Measured by ALICE, Eur. Phys. J. C 73 (2013) 2662 [arXiv:1307.1093] [INSPIRE].

  31. ALICE collaboration, Transverse momentum dependence of inclusive primary charged-particle production in p–Pb collisions at \( \sqrt{s_{\mathrm{NN}}}=5.02 \) TeV, Eur. Phys. J. C 74 (2014) 3054 [arXiv:1405.2737] [INSPIRE].

  32. R. Corke and T. Sjöstrand, Interleaved Parton Showers and Tuning Prospects, JHEP 03 (2011) 032 [arXiv:1011.1759] [INSPIRE].

    ADS  Article  Google Scholar 

  33. P. Skands, S. Carrazza and J. Rojo, Tuning PYTHIA 8.1: the Monash 2013 Tune, Eur. Phys. J. C 74 (2014) 3024 [arXiv:1404.5630] [INSPIRE].

  34. C.A. Salgado and U.A. Wiedemann, Medium modification of jet shapes and jet multiplicities, Phys. Rev. Lett. 93 (2004) 042301 [hep-ph/0310079] [INSPIRE].

  35. 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].

    ADS  Article  Google Scholar 

  36. Y.-T. Chien and I. Vitev, Towards the understanding of jet shapes and cross sections in heavy ion collisions using soft-collinear effective theory, JHEP 05 (2016) 023 [arXiv:1509.07257] [INSPIRE].

    ADS  Article  Google Scholar 

Download references

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.

Author information