BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2013). Measurement of the D*(2010)(+) natural linewidth and the D*(2010)(+)-D-0 mass difference. Phys. Rev. D, 88(5), 052003–20pp.
Abstract: We measure the mass difference, Delta m(0), between the D*(2010)(+) and the D-0 and the natural linewidth, Gamma, of the transition D*(2010)(+) -> D-0 pi(+). The data were recorded with the BABAR detector at center-of-mass energies at and near the Upsilon(4S) resonance, and correspond to an integrated luminosity of approximately 477 fb(-1). The D-0 is reconstructed in the decay modes D-0 -> K-pi(+) and D-0 -> K-pi(+)pi(-)pi(+). For the decay mode D-0 -> K-pi(+) we obtain Gamma = (83.4 +/- 1.7 +/- 1.5) keV and Delta m(0) = (145425.6 +/- 0.6 +/- 1.8) keV, where the quoted errors are statistical and systematic, respectively. For the D-0 -> K-pi(+)pi(-)pi(+) mode we obtain Gamma = (83.2 +/- 1.5 +/- 2.6) keV and Delta m(0) = (145426.6 +/- 0.5 +/- 2.0) keV. The combined measurements yield Gamma = (83.3 +/- 1.2 +/- 1.4) keV and Delta m(0) = (145425.9 +/- 0.4 +/- 1.7) keV; the width is a factor of approximately 12 times more precise than the previous value, while the mass difference is a factor of approximately 6 times more precise.
|
ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2013). Measurement of the distributions of event-by-event flow harmonics in lead-lead collisions at root s(NN)=2.76 TeV with the ATLAS detector at the LHC. J. High Energy Phys., 11(11), 183–57pp.
Abstract: The distributions of event-by-event harmonic flow coefficients v (n) for n = 2- 4 are measured in = 2.76 TeV Pb + Pb collisions using the ATLAS detector at the LHC. The measurements are performed using charged particles with transverse momentum p (T) > 0.5 GeV and in the pseudorapidity range |eta| < 2.5 in a dataset of approximately 7 μb(-1) recorded in 2010. The shapes of the v (n) distributions suggest that the associated flow vectors are described by a two-dimensional Gaussian function in central collisions for v (2) and over most of the measured centrality range for v (3) and v (4). Significant deviations from this function are observed for v (2) in mid-central and peripheral collisions, and a small deviation is observed for v (3) in mid-central collisions. In order to be sensitive to these deviations, it is shown that the commonly used multi-particle cumulants, involving four particles or more, need to be measured with a precision better than a few percent. The v (n) distributions are also measured independently for charged particles with 0.5 < p (T) < 1 GeV and p (T) > 1 GeV. When these distributions are rescaled to the same mean values, the adjusted shapes are found to be nearly the same for these two p (T) ranges. The v (n) distributions are compared with the eccentricity distributions from two models for the initial collision geometry: a Glauber model and a model that includes corrections to the initial geometry due to gluon saturation effects. Both models fail to describe the experimental data consistently over most of the measured centrality range.
|
BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2013). Measurement of the e(+)e(-) -> p(p)over-bar cross section in the energy range from 3.0 to 6.5 GeV. Phys. Rev. D, 88(7), 072009–12pp.
Abstract: The e(+)e(-) -> p (p) over bar cross section and the proton magnetic form factor have been measured in the center-of-mass energy range from 3.0 to 6.5 GeV using the initial-state radiation technique with an undetected photon. This is the first measurement of the form factor at energies higher than 4.5 GeV. The analysis is based on 469 fb-1 of integrated luminosity collected with the BABAR detector at the PEP-II collider at e(+)e(-) center-of-mass energies near 10.6 GeV. The branching fractions for the decays J/psi -> p (p) over bar and psi(2S) -> p (p) over bar have also been measured.
|
LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Measurement of the effective B-S(0) -> J/psi K-S(0) lifetime. Nucl. Phys. B, 873(2), 275–292.
Abstract: This paper reports the first measurement of the effective B-S(0) -> J/psi K-S(0) lifetime and an updated measurement of its time-integrated branching fraction. Both measurements are performed with a data sample, corresponding to an integrated luminosity of 1.0 fb(-1) of pp collisions, recorded by the LHCb experiment in 2011 at a centre-of-mass energy of 7 TeV. The results are: tau(eff)(J/psi KS0) = 1.75 +/- 0.12 (stat) +/- 0.07 (syst) ps and B(B-S(0) -> J/psi K-S(0)) = (1.97 +/- 0.23) x 10(-5). For the latter measurement, the uncertainty includes both statistical and systematic sources.
|
ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2013). Measurement of the flavour composition of dijet events in pp collisions at root s=7 TeV with the ATLAS detector. Eur. Phys. J. C, 73(2), 2301–30pp.
Abstract: This paper describes a measurement of the flavour composition of dijet events produced in pp collisions at root s = 7 TeV using the ATLAS detector. The measurement uses the full 2010 data sample, corresponding to an integrated luminosity of 39 pb(-1). Six possible combinations of light, charm and bottom jets are identified in the dijet events, where the jet flavour is defined by the presence of bottom, charm or solely light flavour hadrons in the jet. Kinematic variables, based on the properties of displaced decay vertices and optimised for jet flavour identification, are used in a multidimensional template fit to measure the fractions of these dijet flavour states as functions of the leading jet transverse momentum in the range 40 GeV to 500 GeV and jet rapidity vertical bar y vertical bar < 2.1. The fit results agree with the predictions of leading-and next-to-leading-order calculations, with the exception of the dijet fraction composed of bottom and light flavour jets, which is underestimated by all models at large transverse jet momenta. The ability to identify jets containing two b-hadrons, originating from e. g. gluon splitting, is demonstrated. The difference between bottom jet production rates in leading and subleading jets is consistent with the next-to-leading-order predictions.
|
