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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2024). Measurement of J/ψ-pair production in pp collisions at √s=13 TeV and study of gluon transverse-momentum dependent PDFs. J. High Energy Phys., 03(3), 088–40pp.
Abstract: The production cross-section of J/psi pairs in proton-proton collisions at a centre-of-mass energy of root s = 13TeV is measured using a data sample corresponding to an integrated luminosity of 4.2 fb(-1) collected by the LHCb experiment. The measurement is performed with both J/psi mesons in the transverse momentum range 0 < p(T) < 14 GeV/c and rapidity range 2.0 < y < 4.5. The cross-section of this process is measured to be 16.36 +/- 0.28 (stat) +/- 0.88 (syst) nb. The contributions from single-parton scattering and double-parton scattering are separated based on the dependence of the cross-section on the absolute rapidity difference Delta y between the two J/psi mesons. The effective cross-section of double-parton scattering is measured to be sigma(eff) = 13.1 +/- 1.8 (stat) +/- 2.3 (syst) mb. The distribution of the azimuthal angle phi(CS) of one of the J/psi mesons in the Collins-Soper frame and the p(T)-spectrum of the J/psi pairs are also measured for the study of the gluon transverse-momentum dependent distributions inside protons. The extracted values of < cos4 phi(CS)> and < cos2 phi(CS)> are consistent with zero, but the presence of azimuthal asymmetry at a few percent level is allowed.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Measurement of the chi(b) (3 P) mass and of the relative rate of chi(b1) (1 P) and chi(b2) (1 P) production. J. High Energy Phys., 10(10), 088–22pp.
Abstract: The production of chi(b) mesons in proton-proton collisions is studied using a data sample collected by the LHCb detector, at centre-of-mass energies of root s = 7 and 8 TeV and corresponding to an integrated luminosity of 3.0 fb(-1). The chi(b) mesons are identified through their decays to Upsilon(1 S)gamma and Upsilon(2 S)gamma using photons that converted to e(+)e (-) pairs in the detector. The relative prompt production rate of chi(b1)(1 P) and chi(b2)(1 P) mesons is measured as a function of the Upsilon(1 S) transverse momentum in the chi(b) rapidity range 2.0 < y < 4.5. A precise measurement of the chi(b) (3 P) mass is also performed. Assuming a mass splitting between the chi(b1)(3 P) and the chi(b2)(3 P) states of 10.5 MeV/c(2), the measured mass of the chi(b1)(3 P) meson is m (chi(b1)(3 P)) = 10515.7(-3.9)(+2.2)(stat)(-2.1)(+1.5)(syst) MeV/c(2).
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2017). Measurement of the J/psi pair production cross-section in pp collisions at root s=13 TeV. J. High Energy Phys., 06(6), 047–38pp.
Abstract: The production cross-section of J/psi pairs is measured using a data sample of pp collisions collected by the LHCb experiment at a centre-of-mass energy of root s = 13TeV, corresponding to an integrated luminosity of 279 +/- 11 pb(-1). The measurement is performed for J/psi mesons with a transverse momentum of less than 10 GeV/c in the rapidity range 2.0 < y < 4.5. The production cross-section is measured to be 15.2 +/- 1.0 +/- 0.9 nb. The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the J/psi pair are measured and compared to theoretical predictions.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2018). Measurement of Upsilon production in pp collisions at root s=13 TeV. J. High Energy Phys., 07(7), 134–27pp.
Abstract: The production cross-sections of Upsilon(1S), Upsilon(2S) and Upsilon(3S) mesons in proton-proton collisions at root s = 13 TeV are measured with a data sample corresponding to an integrated luminosity of 277 +/- 11 pb(-1) recorded by the LHCb experiment in 2015. The Upsilon mesons are reconstructed in the decay mode Upsilon -> mu(+)mu(-). The differential production cross-sections times the dimuon branching fractions are measured as a function of the Upsilon transverse momentum, p(T) , and rapidity, y, over the range 0 < p(T) < 30 GeV/c and 2.0 < y < 4.5. The ratios of the cross-sections with respect to the LHCb measurement at root s = 8 TeV are also determined. The measurements are compared with theoretical predictions based on NRQCD.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Measurement of Υ production in pp collisions at √s=5 TeV. J. High Energy Phys., 07(7), 069–33pp.
Abstract: The production cross-sections of Υ mesons, namely Υ(1S), Υ(2S) and Υ(3S), in pp collisions at root s = 5TeV are measured with a data sample corresponding to an integrated luminosity of 9.13 +/- 0.18 pb(-1) collected by the LHCb detector. The Υ mesons are reconstructed in the decay mode Υ -> mu(+)mu(-). Double differential cross-sections times branching fractions, as functions of the transverse momentum p(T) and the rapidity y of the Υ mesons, are measured in the range pT < 20 GeV/ c and 2.0 < y < 4.5. The results integrated over these pT and y ranges are sigma((sic)(1S)) x B((sic)(1S) -> mu(+) mu(-)) = 2101 +/- 33 +/- 83 pb, sigma((sic)(2S)) x B((sic)(2S) -> mu(+) mu(-)) = 526 +/- 20 +/- 21 pb, sigma((sic)(3S)) x B((sic)(3S) -> mu(+) mu(-)) = 242 +/- 16 +/- 10 pb, where the first uncertainties are statistical and the second are systematic. The ratios of cross-sections between measurements of two different (sic) states and between measurements at different centre-of-mass energies are determined. The nuclear modification factor of (sic)(1S) at root s = 5TeV is updated as well using the directly measured cross-section results from this analysis.
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