Measurement of the upsilon(1S) production cross-section in pp collisions at root s = 7 TeV
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KünyeAad, G, Abbott, B., Abdallah, J., Abdelalim, A.A., Abdesselam, A., Abdinov, O. ... ATLAS Collaboration. (2011). Measurement of the upsilon(1S) production cross-section in pp collisions at root s = 7 TeV. Physics Letters B, 705 (1-2), pp. 9-27. http://dx.doi.org/10.1016/j.physletb.2011.09.092.
A measurement of the cross-section for Upsilon(1S) -> mu(+)mu(-) production in proton-proton collisions at centre of mass energy of 7 TeV is presented. The cross-section is measured as a function of the gamma(1S) transverse momentum in two bins of rapidity, vertical bar y(gamma(1S))vertical bar < 1.2 and 1.2 < vertical bar y(gamma(1S))vertical bar < 2.4. The measurement requires that both muons have transverse momentum p(T)(mu) > 4 GeV and pseuclorapidity vertical bar eta(mu)vertical bar < 2.5 in order to reduce theoretical uncertainties on the acceptance, which depend on the poorly known polarisation. The results are based on an integrated luminosity of 1.13 pb(-1), collected with the ATLAS detector at the Large Hadron Collider. The cross-section measurement is compared to theoretical predictions: it agrees to within a factor of two with a prediction based on the NRQCD model including colour-singlet and colour-octet matrix elements as implemented in PYTHIA while it disagrees by up to a factor of ten with the next-to-leading order prediction based on the colour-singlet model.