Measurement of the Upsilon(1S), Upsilon(2S), and Upsilon(3S) Polarizations in pp Collisions at root s 7 TeV

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Chatrchyan S., Khachatryan V., Sirunyan A. M., Tumasyan A., Adam W., Aguilo E., ...More

PHYSICAL REVIEW LETTERS, vol.110, no.8, 2013 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 110 Issue: 8
  • Publication Date: 2013
  • Doi Number: 10.1103/physrevlett.110.081802
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Dokuz Eylül University Affiliated: Yes


The polarizations of the Upsilon(1S), Upsilon(2S), and Upsilon(3S) mesons are measured in proton-proton collisions at root s = 7 TeV, using a data sample of Upsilon(nS) -> mu(+)mu(-) decays collected by the CMS experiment, corresponding to an integrated luminosity of 4.9 fb(-1). The dimuon decay angular distributions are analyzed in three different polarization frames. The polarization parameters lambda(theta), lambda(phi), and lambda(theta phi), as well as the frame-invariant quantity (lambda) over tilde, are presented as a function of the Upsilon(nS) transverse momentum between 10 and 50 GeV, in the rapidity ranges vertical bar y vertical bar < 0: 6 and 0: 6 < vertical bar y vertical bar < 1.2. No evidence of large transverse or longitudinal polarizations is seen in the explored kinematic region. DOI: 10.1103/PhysRevLett.110.081802