|
LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Measurement of CP violation and constraints on the CKM angle gamma in B-+/- -> DK +/- with D -> K-s(0)pi(+)pi(-) decays. Nucl. Phys. B, 888, 169–193.
Abstract: A model-dependent amplitude analysis of B-+/- -> DK +/- with D -> K-s(0)pi(+)pi(-) decays is performed using proton proton collision data, corresponding to an integrated luminosity of 1 fb(-1), recorded by LHCb at a centre-of-mass energy of 7 TeV in 2011. Values of the CP violation observables x +/- and y +/-, which are sensitive to the CKM angle gamma, are measured to be x- = +0.027 +/- 0.0441(-0.008)(+0.010) +/- 0.001, y- = +0.013 +/- 0.0481(-0.007)(+0.009) +/- 0.003, x+ = -0.084 +/- 0.045 +/- 0.009 +/- 0.005, y+ = -0.032 +/- 0.048(-0.009)(+0.010) +/- 0.008, where the first uncertainty is statistical, the second systematic and the third arises from the uncertainty of the D -> K-S(0)pi(+)pi(-) amplitude model. The value of gamma is determined to be (84(-42)(+49))degrees including all sources of uncertainty. Neutral D meson mixing is found to have negligible effect.
|
|
|
ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., Fiorini, L., et al. (2014). Measurement of the total cross section from elastic scattering in pp collisions at root s=7 TeV with the ATLAS detector. Nucl. Phys. B, 889, 486–548.
Abstract: A measurement of the total pp cross section at the LHC at root s = 7 TeV is presented. In a special run with high-beta* beam optics, an integrated luminosity of 80 μb(-1) was accumulated in order to measure the differential elastic cross section as a function of the Mandelstam momentum transfer variable t. The measurement is performed with the ALFA sub-detector of ATLAS. Using a fit to the differential elastic cross section in the vertical bar t vertical bar range from 0.01 GeV2 to 0.1 GeV2 to extrapolate to vertical bar t vertical bar --> 0, the total cross section, sigma(tot)(pp --> X), is measured via the optical theorem to be: sigma(tot)(pp --> X) = 95.35 +/- 0.38 (stat.) +/- 1.25 (exp.) +/- 0.37 (extr.) mb, where the first error is statistical, the second accounts for all experimental systematic uncertainties and the last is related to uncertainties in the extrapolation to vertical bar t vertical bar --> 0. In addition, the slope of the elastic cross section at small vertical bar t vertical bar is determined to be B = 19.73 +/- 0.14 (stat.) +/- 0.26 (syst.) GeV-2.
|
|
|
n_TOF Collaboration(Lederer, C. et al.), Giubrone, G., & Tain, J. L. (2014). Ni-62(n,gamma) and Ni-63(n,gamma) cross sections measured at the n_TOF facility at CERN. Phys. Rev. C, 89(2), 025810–11pp.
Abstract: The cross section of the Ni-62(n,gamma) reaction was measured with the time-of-flight technique at the neutron time-of-flight facility nTOF at CERN. Capture kernels of 42 resonances were analyzed up to 200 keV neutron energy and Maxwellian averaged cross sections (MACS) from kT = 5-100 keV were calculated. With a total uncertainty of 4.5%, the stellar cross section is in excellent agreement with the the KADoNiS compilation at kT = 30 keV, while being systematically lower up to a factor of 1.6 at higher stellar temperatures. The cross section of the Ni-63(n,gamma) reaction was measured for the first time at nTOF. We determined unresolved cross sections from 10 to 270 keV with a systematic uncertainty of 17%. These results provide fundamental constraints on s-process production of heavier species, especially the production of Cu in massive stars, which serve as the dominant source of Cu in the solar system.
|
|
|
Xie, J. J., Wang, E., & Nieves, J. (2014). Re-analysis of the A(1520) photoproduction reaction. Phys. Rev. C, 89(1), 015203–10pp.
Abstract: Based on previous studies that support the important role of the N*(2120)D-13 resonance in the gamma p -> K+ A(1520) reaction, we make a re-analysis of this A(1520) photoproduction reaction taking into account the recent CLAS differential cross-section data. In addition to the contact, t-channel (K) over bar exchange, s-channel nucleon pole, and N*(2120) [previously called N*(2080)] resonance contributions, which have been considered in previous works, we also study the u-channel A(1115) hyperon pole term. The latter mechanism has always been ignored in all theoretical analysis, which has mostly relied on the very forward K+ angular LEPS data. It is shown that when the contributions from the N*(2120) resonance and the A(1115) hyperon are taken into account, both the new CLAS and the previous LEPS data can be simultaneously described. We also show that the contribution from the u-channel A(1115) pole term produces an enhancement for large K+ angles, and it becomes more and more relevant as the photon energy increases, being essential to describe the CLAS differential cross sections at backward angles. Furthermore, we find that the new CLAS data also favor the existence of the N*(2120) resonance and that these measurements can be used to further constrain its properties.
|
|
|
Wang, E., Alvarez-Ruso, L., & Nieves, J. (2014). Photon emission in neutral-current interactions at intermediate energies. Phys. Rev. C, 89(1), 015503–21pp.
Abstract: Neutral-current photon emission reactions with nucleons and nuclei are studied. These processes are important backgrounds for nu(mu) -> nu(e) ((nu) over bar (mu) -> (nu) over bar (e)) appearance oscillation experiments where electromagnetic showers instigated by electrons (positrons) and photons are not distinguishable. At intermediate energies, these reactions are dominated by the weak excitation of the Delta(1232) resonance and its subsequent decay into N gamma. There are also nonresonant contributions that, close to threshold, are fully determined by the effective chiral Lagrangian of strong interactions. In addition, we have also included mechanisms mediated by nucleon excitations (N*) from the second resonance region above the Delta(1232). From these states, the contribution of the D-13 N*(1520) turns out to be sizable for (anti) neutrino energies above 1.5 GeV. We have extended the model to nuclear targets taking into account Pauli blocking, Fermi motion, and the in-medium Delta resonance broadening. We present our predictions for both the incoherent and coherent channels, showing the relevance of the nuclear corrections. We also discuss the target mass dependence of the cross sections. This study is important to reduce systematic effects in neutrino oscillation experiments.
|
|