|
|
ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fernandez Martinez, P., Ferrer, A., et al. (2015). Evidence of W gamma gamma Production in pp Collisions at root s=8 TeV and Limits on Anomalous Quartic Gauge Couplings with the ATLAS Detector. Phys. Rev. Lett., 115(3), 031802–18pp.
Abstract: This Letter reports evidence of triple gauge boson production pp -> W(l nu)gamma gamma + X, which is accessible for the first time with the 8 TeV LHC data set. The fiducial cross section for this process is measured in a data sample corresponding to an integrated luminosity of 20.3 fb(-1), collected by the ATLAS detector in 2012. Events are selected using the W boson decay to e nu or μnu as well as requiring two isolated photons. The measured cross section is used to set limits on anomalous quartic gauge couplings in the high diphoton mass region.
|
|
|
|
LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Dalitz plot analysis of B-0 -> (D)over-bar(0)pi(+)pi(-) decays. Phys. Rev. D, 92(3), 032002–40pp.
Abstract: The resonant substructures of B-0 --> (D) over bar (0)pi(+)pi(-) decays are studied with the Dalitz plot technique. In this study a data sample corresponding to an integrated luminosity of 3.0 fb(-1) of pp collisions collected by the LHCb detector is used. The branching fraction of the B-0 --> (D) over bar (0)pi(+)pi(-) decay in the region m((D) over bar (0)pi(+/-)) > 2.1 GeV/c(2) is measured to be (8.46 +/- 0.14 +/- 0.29 +/- 0.40) x 10(-4), where the first uncertainty is statistical, the second is systematic and the last arises from the normalization channel B-0 --> D*(2010)(-)pi(+). The pi(+)pi(-) S-wave components are modeled with the isobar and K-matrix formalisms. Results of the Dalitz plot analyses using both models are presented. A resonant structure at m((D) over bar (0)pi(-)) approximate to 2.8 GeV/c(2) is confirmed and its spin-parity is determined for the first time as J(P) = 3(-). The branching fraction, mass and width of this structure are determined together with those of the D-0*(2400)(-) and D-2*(2460)(-) resonances. The branching fractions of other B-0 --> (D) over bar (0)h(0) decay components with h(0) --> pi(+)pi(-) also reported. Many of these branching fraction measurements are the most precise to date. The first observation of the decays B0 --> (D) over bar (0)f(0)(500), B-0 --> (D) over bar (0)f(0)(980), B-0 --> (D) over bar (0)rho(1450), B-0 --> D-3(*)(2760)(-)pi(+) and the first evidence of B-0 --> (D) over bar (0)f(0)(2020) are presented.
|
|
|
|
Deppisch, F. F., Harz, J., Huang, W. C., Hirsch, M., & Pas, H. (2015). Falsifying high-scale baryogenesis with neutrinoless double beta decay and lepton flavor violation. Phys. Rev. D, 92(3), 036005–6pp.
Abstract: Interactions that manifest themselves as lepton number violating processes at low energies in combination with sphaleron transitions typically erase any preexisting baryon asymmetry of the Universe. In this article, we discuss the constraints obtained from an observation of neutrinoless double beta decay in this context. If a new physics mechanism of neutrinoless double beta decay other than the standard light neutrino exchange is observed, typical scenarios of high-scale baryogenesis will be excluded unless the baryon asymmetry is stabilized via some new mechanism. We also sketch how this conclusion can be extended beyond the first lepton generation by incorporating lepton flavor violating processes.
|
|
|
|
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 type-III seesaw heavy leptons in pp collisions at root s=8 TeV with the ATLAS detector. Phys. Rev. D, 92(3), 032001–20pp.
Abstract: A search for the pair production of heavy leptons (N-0, L-+/-) predicted by the type-III seesaw theory formulated to explain the origin of small neutrino masses is presented. The decay channels N-0 -> W(+/-)l(+/-) (l = e, mu, tau) and L-+/- -> W(+/-)v (v = v(e), v(mu), v(tau)) are considered. The analysis is performed using the final state that contains two leptons (electrons or muons), two jets from a hadronically decaying W boson and large missing transverse momentum. The data used in the measurement correspond to an integrated luminosity of 20.3 fb(-1) of pp collisions at root s = 8 TeV collected by the ATLAS detector at the LHC. No evidence of heavy lepton pair production is observed. Heavy leptons with masses below 325-540 GeV are excluded at the 95% confidence level, depending on the theoretical scenario considered.
|
|
|
|
Garzon, E. J., & Xie, J. J. (2015). Effects of a Nc(c)over-bar* resonance with hidden charm in the pi(-)p -> D-Sigma(+)(c) reaction near threshold. Phys. Rev. C, 92(3), 035201–4pp.
Abstract: We study the effect of a hidden charm nuclear excited state N-c (c) over bar* in the pi(-)p -> D-Sigma(+)(c) reaction near threshold using an effective Lagrangian approach. We calculate the background contribution of the t and u channels by the D*(0) vector meson exchange and Sigma(++)(c) intermediate state, respectively. We show that the consideration of a N-c (c) over bar* resonance provides an enhancement of the total cross section close to the reaction threshold. We also evaluate the differential cross section for different energies and we study the angle dependence. It is expected that our model calculations will be tested in future experiments.
|
|
