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., ...Daha Fazla

PHYSICAL REVIEW LETTERS, cilt.110, 2013 (SCI İndekslerine Giren Dergi) identifier identifier identifier

Özet

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