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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. (2017). Study of b(b)over-bar correlations in high energy proton-proton collisions. J. High Energy Phys., 11(11), 030–28pp.
Abstract: Kinematic correlations for pairs of beauty hadrons, produced in high energy proton-proton collisions, are studied. The data sample used was collected with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV and corresponds to an integrated luminosity of 3 fb(-1). The measurement is performed using inclusive b -> J/psi X decays in the rapidity range 2 < y(J/psi) < 4.5. The observed correlations are in good agreement with theoretical predictions.
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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). Measurements of prompt charm production cross-sections in pp collisions at root s=5TeV. J. High Energy Phys., 06(6), 147–41pp.
Abstract: Production cross-sections of prompt charm mesons are measured using data from pp collisions at the LHC at a centre-of-mass energy of 5TeV. The data sample corresponds to an integrated luminosity of 8 : 60 +/- 0 : 33 pb(-1) collected by the LHCb experiment. The production cross-sections of D-0, D+, D-s(+), and D*(+) mesons are measured in bins of charm meson transverse momentum, p(T), and rapidity, y. They cover the rapidity range 2 : 0 < y < 4 : 5 and transverse momentum ranges 0 < p(T) < 10 GeV/c for D-0 and D+ and 1 < p(T) < 10 GeV/c for D-s(+) and D*(+) mesons. The inclusive cross- sections for the four mesons, including charge-conjugate states, within the range of 1 < p(T) < 8 GeV/c are determined to be sigma (pp -> D-0 X) – 1004 +/- 3 +/- 54 μb; sigma ( pp -> D+ X) = 402 +/- 2 +/- 30 μb; sigma ( pp -> Ds+X) = 170 +/- 4 +/- 16 μb; sigma ( pp -> D*(+) X) = 421 +/- 5 +/- 36 μb; where the uncertainties are statistical and systematic, respectively.
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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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Ayala, C., Cvetic, G., & Kogerler, R. (2017). Lattice-motivated holomorphic nearly perturbative QCD. J. Phys. G, 44(7), 075001–30pp.
Abstract: Newer lattice results indicate that, in the Landau gauge at low spacelike momenta, the gluon propagator and the ghost dressing function are finite non-zero. This leads to a definition of the QCD running coupling, in a specific scheme, that goes to zero at low spacelike momenta. We construct a running coupling which fulfills these conditions, and at the same time reproduces to a high precision the perturbative behavior at high momenta. The coupling is constructed in such a way that it reflects qualitatively correctly the holomorphic (analytic) behavior of spacelike observables in the complex plane of the squared momenta, as dictated by the general principles of quantum field theories. Further, we require the coupling to reproduce correctly the nonstrange semihadronic decay rate of tau lepton which is the best measured low-momentum QCD observable with small higher-twist effects. Subsequent application of the Borel sum rules to the V + A spectral functions of tau lepton decays, as measured by OPAL Collaboration, determines the values of the gluon condensate and of the V + A six-dimensional condensate, and reproduces the data to a significantly higher precision than the usual (MS) over bar running coupling.
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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). Study of the D(0)p amplitude in Lambda(0)(b) -> D(0)p pi(-) decays. J. High Energy Phys., 05(5), 030–43pp.
Abstract: An amplitude analysis of the decay Lambda(0)(b) -> D(0)p pi(-) is performed in the part of the phase space containing resonances in the D(0)p channel. The study is based on a data sample corresponding to an integrated luminosity of 3.0 fb(-1) of pp collisions recorded by the LHCb experiment. The spectrum of excited Lambda(+)(c) states that decay into D(0)p is studied. The masses, widths and quantum numbers of the Lambda(c)(2880)(+) and Lambda(c) (2940)(+) resonances are measured. The constraints on the spin and parity for the Lambda(c)(2940)(+) state are obtained for the first time. A near-threshold enhancement in the D(0)p amplitude is investigated and found to be consistent with a new resonance, denoted the Lambda(c) (2860)(+), of spin 3/2 and positive parity.
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