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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Observation of the B-s(0) -> eta 'eta ' Decay. Phys. Rev. Lett., 115(5), 051801–9pp.
Abstract: The first observation of the B-s(0) -> eta'eta' decay is reported. The study is based on a sample of proton-proton collisions corresponding to 3.0 fb(-1) of integrated luminosity collected with the LHCb detector. The significance of the signal is 6.4 standard deviations. The branching fraction is measured to be [3.31 +/- 0.64(stat) +/- 0.28(syst) +/- 0.12(norm)] x 10(-5), where the third uncertainty comes from the B-+/- -> eta'K-+/- branching fraction that is used as a normalization. In addition, the charge asymmetries of B-+/- -> eta'K-+/- and B-+/- -> phi K-+/-, which are control channels, are measured to be (-0.2 +/- 1.3)% and (+1.7 +/- 1.3)%, respectively. All results are consistent with theoretical expectations.
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Ayala, C., & Mikhailov, S. V. (2015). How to perform a QCD analysis of DIS in analytic perturbation theory. Phys. Rev. D, 92(1), 014028–11pp.
Abstract: We apply (fractional) analytic perturbation theory (FAPT) to the QCD analysis of the nonsinglet nucleon structure function F-2(x, Q(2)) in deep inelastic scattering up to the next leading order and compare the results with ones obtained within the standard perturbation QCD. Based on a popular parametrization of the corresponding parton distribution we perform the analysis within the Jacobi polynomial formalism and under the control of the numerical inverse Mellin transform. To reveal the main features of the FAPT two-loop approach, we consider a wide range of momentum transfer from high Q(2) similar to 100 GeV2 to low Q(2) similar to 0.3 GeV2 where the approach still works.
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Geng, L. S., Ren, X. L., Zhou, Y., Chen, H. X., & Oset, E. (2015). S-wave KK* interactions in a finite volume and the f(1)(1285). Phys. Rev. D, 92(1), 014029–9pp.
Abstract: Lattice QCD simulations provide a promising way to disentangle different interpretations of hadronic resonances, which might be of particular relevance to understand the nature of the so-called XYZ particles. Recent studies have shown that in addition to the well-established naive quark model picture, the axial-vector meson f(1)(1285) can also be understood as a dynamically generated state built upon the KK* interaction. In this work, we calculate the energy levels of the KK* system in the f(1)(1285) channel in finite volume using the chiral unitary approach. We propose to calculate the loop function in the dimensional regularization scheme, which is equivalent to the hybrid approach adopted in previous studies. We also study the inverse problem of extracting the bound state information from synthetic lattice QCD data and comment on the difference between our approach and the Luscher method.
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Navarra, F. S., Nielsen, M., Oset, E., & Sekihara, T. (2015). Testing the molecular nature of D-s0*(2317) and D-0*(2400) in semileptonic B-s and B decays. Phys. Rev. D, 92(1), 014031–14pp.
Abstract: We study the semileptonic B-s and B decays into the D-s0*(2317) and D-0*(2400) resonances, respectively. With the help of a chiral unitarity model in coupled channels we compute the ratio of the decay widths of both processes. Using current values of the width for the (B) over bar (0) -> D-0*(2400)(+)(v) over bar (l)l(-) we make predictions for the rate of the (B) over bar (0)(s) -> D-s0*(2317)(+)(v) over bar (l)l(-) decay and for the DK invariant mass distribution in the (B) over bar (0)(s) -> DK (v) over bar (l)l(-) decay.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fernandez Martinez, P., et al. (2015). Search for long-lived, weakly interacting particles that decay to displaced hadronic jets in proton-proton collisions at root s=8 TeV with the ATLAS detector. Phys. Rev. D, 92(1), 012010–28pp.
Abstract: A search for the decay of neutral, weakly interacting, long-lived particles using data collected by the ATLAS detector at the LHC is presented. This analysis uses the full data set recorded in 2012: 20.3 fb(-1) of proton-proton collision data at root s = 8 TeV. The search employs techniques for reconstructing decay vertices of long-lived particles decaying to jets in the inner tracking detector and muon spectrometer. Signal events require at least two reconstructed vertices. No significant excess of events over the expected background is found, and limits as a function of proper lifetime are reported for the decay of the Higgs boson and other scalar bosons to long-lived particles and for Hidden Valley Z' and Stealth SUSY benchmark models. The first search results for displaced decays in Z' and Stealth SUSY models are presented. The upper bounds of the excluded proper lifetimes are the most stringent to date.
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