Skip to main content

Multiplicity dependence of two-particle azimuthal correlations in pp collisions at the LHC

Abstract

We present the measurements of particle pair yields per trigger particle obtained from di-hadron azimuthal correlations in pp collisions at \( \sqrt{s} \) = 0.9, 2.76, and 7 TeV recorded with the ALICE detector. The yields are studied as a function of the charged particle multiplicity. Taken together with the single particle yields the pair yields provide information about parton fragmentation at low transverse momenta, as well as on the contribution of multiple parton interactions to particle production. Data are compared to calculations using the PYTHIA6, PYTHIA8, and PHOJET event generators.

References

  1. [1]

    R.P. Feynman, Very high-energy collisions of hadrons, Phys. Rev. Lett. 23 (1969) 1415 [INSPIRE].

    ADS  Article  Google Scholar 

  2. [2]

    Z. Koba, H.B. Nielsen and P. Olesen, Scaling of multiplicity distributions in high-energy hadron collisions, Nucl. Phys. B 40 (1972) 317 [INSPIRE].

    ADS  Article  Google Scholar 

  3. [3]

    UA5 collaboration, G. Alner et al., Scaling violations in multiplicity distributions at 200 GeV and 900 GeV, Phys. Lett. B 167 (1986) 476 [INSPIRE].

    ADS  Article  Google Scholar 

  4. [4]

    I. Dremin and V. Nechitailo, Soft multiple parton interactions as seen in multiplicity distributions at Tevatron and LHC, Phys. Rev. D 84 (2011) 034026 [arXiv:1106.4959] [INSPIRE].

    ADS  Google Scholar 

  5. [5]

    I. Dremin and J. Gary, Hadron multiplicities, Phys. Rept. 349 (2001) 301 [hep-ph/0004215] [INSPIRE].

    ADS  Article  MATH  Google Scholar 

  6. [6]

    J.F. Große-Oetringhaus and K. Reygers, Charged-particle multiplicity in proton-proton collisions, J. Phys. G 37 (2010) 083001 [arXiv:0912.0023] [INSPIRE].

    ADS  Article  Google Scholar 

  7. [7]

    T. Sjöstrand and M. van Zijl, A multiple interaction model for the event structure in hadron collisions, Phys. Rev. D 36 (1987) 2019 [INSPIRE].

    ADS  Google Scholar 

  8. [8]

    M. Bahr, J.M. Butterworth and M.H. Seymour, The underlying event and the total cross section from Tevatron to the LHC, JHEP 01 (2009) 065 [arXiv:0806.2949] [INSPIRE].

    ADS  Article  Google Scholar 

  9. [9]

    X.-N. Wang, Studying mini-jets via the p T dependence of the two particle correlation in Azimuthal angle ϕ, Phys. Rev. D 47 (1993) 2754 [hep-ph/9306215] [INSPIRE].

    ADS  Google Scholar 

  10. [10]

    CDF collaboration, D. Acosta et al., Soft and hard interactions in \( p\overline{p} \) collisions at \( \sqrt{s} \) = 1800GeV and 630GeV,Phys. Rev. D 65 (2002) 072005 [INSPIRE].

    ADS  Google Scholar 

  11. [11]

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

    ADS  Article  Google Scholar 

  12. [12]

    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].

    ADS  Article  MATH  Google Scholar 

  13. [13]

    R. Engel, J. Ranft and S. Roesler, Hard diffraction in hadron hadron interactions and in photoproduction, Phys. Rev. D 52 (1995) 1459 [hep-ph/9502319] [INSPIRE].

    ADS  Google Scholar 

  14. [14]

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

    ADS  Article  Google Scholar 

  15. [15]

    J.C. Collins and D.E. Soper, The theorems of perturbative QCD, Ann. Rev. Nucl. Part. Sci. 37 (1987) 383 [INSPIRE].

    ADS  Article  Google Scholar 

  16. [16]

    P.Z. Skands, Tuning Monte Carlo generators: the Perugia tunes, Phys. Rev. D 82 (2010) 074018 [arXiv:1005.3457] [INSPIRE].

    ADS  Google Scholar 

  17. [17]

    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].

    ADS  Google Scholar 

  18. [18]

    ALICE collaboration, Transverse sphericity of primary charged particles in minimum bias proton-proton collisions at \( \sqrt{s} \) = 0.9, 2.76 and 7 TeV, Eur. Phys. J. C 72 (2012) 2124 [arXiv:1205.3963] [INSPIRE].

    ADS  Google Scholar 

  19. [19]

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

  20. [20]

    R. Corke and T. Sjöstrand, Interleaved parton showers and tuning prospects, JHEP 03 (2011) 032 [arXiv:1011.1759] [INSPIRE].

    ADS  Article  Google Scholar 

  21. [21]

    R. Brun, F. Carminati and S. Giani, GEANT detector description and simulation tool, CERN Internal Note CERN-W5013 (1994).

  22. [22]

    GEANT4 collaboration, S. Agostinelli et al., GEANT4: a simulation toolkit, Nucl. Instrum. Meth. A 506 (2003) 250 [INSPIRE].

    ADS  Article  Google Scholar 

  23. [23]

    J. Allison et al., Geant4 developments and applications, IEEE Trans. Nucl. Sci. 53 (2006) 270 [INSPIRE].

    ADS  Article  Google Scholar 

  24. [24]

    ALICE collaboration, First proton-proton collisions at the LHC as observed with the ALICE detector: Measurement of the charged particle pseudorapidity density at \( \sqrt{s} \) = 900 GeV, Eur. Phys. J. C 65 (2010) 111 [arXiv:0911.5430] [INSPIRE].

    ADS  Google Scholar 

  25. [25]

    ALICE collaboration, Production of pions, kaons and protons in pp collisions at \( \sqrt{s} \) = 900GeV with ALICE at the LHC, Eur. Phys. J. C 71 (2011) 1655 [arXiv:1101.4110] [INSPIRE].

    ADS  Google Scholar 

  26. [26]

    ALICE collaboration, Strange particle production in proton-proton collisions at \( \sqrt{s} \) = 0.9TeV with ALICE at the LHC, Eur. Phys. J. C 71 (2011) 1594 [arXiv:1012.3257] [INSPIRE].

    ADS  Google Scholar 

  27. [27]

    ALICE collaboration, Transverse momentum spectra of charged particles in proton-proton collisions at \( \sqrt{s} \) = 900 GeV with ALICE at the LHC, Phys. Lett. B 693 (2010) 53 [arXiv:1007.0719] [INSPIRE].

    ADS  Google Scholar 

  28. [28]

    E. Sicking, Multiplicity dependence of two-particle angular correlations in proton-proton collisions measured with ALICE at the LHC, PhD Thesis, University of Münster, Münster Germany (2012), CERN-THESIS-2012-210.

  29. [29]

    ALICE collaboration, Suppression of charged particle production at large transverse momentum in central Pb-Pb collisions at \( \sqrt{{{s_{NN }}}} \) = 2.76 TeV, Phys. Lett. B 696 (2011) 30 [arXiv:1012.1004] [INSPIRE].

    ADS  Google Scholar 

  30. [30]

    CMS collaboration, Strange particle production in pp collisions at \( \sqrt{s} \) = 0.9 and 7 TeV, JHEP 05 (2011) 064 [arXiv:1102.4282] [INSPIRE].

    Google Scholar 

Download references

Author information

Affiliations

Authors