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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). Evidence for the two-body charmless baryonic decay B+ -> p(Lambda)over-bar. J. High Energy Phys., 04(4), 162–18pp.
Abstract: A search for the rare two-body charmless baryonic decay B+ -> p (Lambda) over bar is performed with pp collision data, corresponding to an integrated luminosity of 3 fb(-1), collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. An excess of B+ -> p (Lambda) over bar candidates with respect to background expectations is seen with a statistical significance of 4.1 standard deviations, and constitutes the first evidence for this decay. The branching fraction, measured using the B+ -> K-S(0)pi(+) decay for normalisation, is B(B+ -> p (Lambda) over bar) = (2.4(-0.8)(+)(+1.0) +/- 0.3) x 10(-7), where the first uncertainty is statistical and the second systematic.
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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). Observation of the decay B-s(0) -> eta(c)phi and evidence for B-s(0) -> eta(c)pi(+)pi(-). J. High Energy Phys., 07(7), 021–33pp.
Abstract: A study of B-s(0) -> eta(c)phi and B-s(0) -> eta(c)pi(+)pi(-) decays is performed using pp collision data corresponding to an integrated luminosity of 3.0 fb(-1), collected with the LHCb detector in Run 1 of the LHC. The observation of the decay B-s(0) -> eta(c)phi is reported, where the eta(c) meson is reconstructed in the p (p) over bar, K+K-pi(+)pi(-), pi(+)pi(-)pi(+)pi-and K+K-K+K-decay modes and the phi(1020) in the K+K-decay mode. The decay B-s(0) -> J/psi phi is used as a normalisation channel. Evidence is also reported for the decay B-s(0) -> eta(c)pi(+)pi(-), where the eta(c) meson is reconstructed in the p (p) over bar decay mode, using the decay B-s(0) -> J/psi phi pi(+)pi-as a normalisation channel. The measured branching fractions are B(B-s(0) -> eta(c)phi) = (5 : 01 +/- 0 : 53 +/- 0 : 27 +/- 0 : 63) x 10(-4), B(B-s(0) -> eta(c)pi(+)pi(-)) = (1 : 76 +/- 0 : 59 +/- 0 : 12 +/- 0 : 29) x 10(-4), where in each case the fi rst uncertainty is statistical, the second systematic and the third uncertainty is due to the limited knowledge of the external branching fractions.
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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). Updated branching fraction measurements of B-(s)(0) -> K(S)(0)h(+)h'(-) decays. J. High Energy Phys., 11(11), 027–42pp.
Abstract: The charmless three-body decays B-(s)(0) -> K(S)(0)h(+)h '(-) (where h((')) – pi, K) are analysed using a sample of pp collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 3 fb(-1). The branching fractions are measured relative to that of the B-0 -> K-S(0) pi(+)pi(-) decay, and are determined to be: B(B-0 -> (KSK +/-)-K-0 pi(-/+))/B(B-0 -> K-S(0)pi(+)pi(-) = 0.123 +/- 0.009 (stat) +/- 0.015 (syst), B(B-0 -> (KSK+K-)-K-0)/B(B-0 -> K-S(0)pi(+)pi(-) = 0.549 +/- 0.018 (stat) +/- 0.033 (syst), B(B-S(0) -> K-S(0) pi(+)pi(-))/B(B-0 -> K-S(0)pi(+)pi(-)) = 0.191 +/- 0.027 (stat) +/- 0.031 (syst) +/- 0.011 (f(s)/f(d)), B(B-0 -> (KSK +/-)-K-0 pi(-/+))/B(B-0 -> K-S(0)pi(+)pi(-) = 1.70 +/- 0.07 (stat) +/- 0.11 (syst) +/- 0.10 (f(s)/f(d)), B(B-0 -> (KSK+K-)-K-0)/B(B-0 -> K-S(0)pi(+)pi(-) is an element of [0.008 – 0.051] at 90% confidence level, where f(s)/f(d) represents the ratio of hadronisation fractions of the B-s(0) and B-0 mesons.
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NEXT Collaboration(Renner, J. et al), Benlloch-Rodriguez, J., Botas, A., Ferrario, P., Gomez-Cadenas, J. J., Alvarez, V., et al. (2017). Background rejection in NEXT using deep neural networks. J. Instrum., 12, T01004–21pp.
Abstract: We investigate the potential of using deep learning techniques to reject background events in searches for neutrinoless double beta decay with high pressure xenon time projection chambers capable of detailed track reconstruction. The differences in the topological signatures of background and signal events can be learned by deep neural networks via training over many thousands of events. These networks can then be used to classify further events as signal or background, providing an additional background rejection factor at an acceptable loss of efficiency. The networks trained in this study performed better than previous methods developed based on the use of the same topological signatures by a factor of 1.2 to 1.6, and there is potential for further improvement.
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Beltran Jimenez, J., Heisenberg, L., Olmo, G. J., & Rubiera-Garcia, D. (2017). On gravitational waves in Born-Infeld inspired non-singular cosmologies. J. Cosmol. Astropart. Phys., 10(10), 029–23pp.
Abstract: We study the evolution of gravitational waves for non-singular cosmological solutions within the framework of Born-Infeld inspired gravity theories, with special emphasis on the Eddington-inspired Born-Infeld theory. We review the existence of two types of non-singular cosmologies, namely bouncing and asymptotically Minkowski solutions, from a perspective that makes their features more apparent. We study in detail the propagation of gravitational waves near these non-singular solutions and carefully discuss the origin and severity of the instabilities and strong coupling problems that appear. We also investigate the role of the adiabatic sound speed of the matter sector in the regularisation of the gravitational waves evolution. We extend our analysis to more general Born-Infeld inspired theories where analogous solutions are found. As a general conclusion, we obtain that the bouncing solutions are generally more prone to instabilities, while the asymptotically Minkowski solutions can be rendered stable, making them appealing models for the early universe.
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AGATA Collaboration(Clement, E. et al), Domingo-Pardo, C., Gadea, A., Perez-Vidal, R. M., & Civera, J. V. (2017). Conceptual design of the AGATA 1 pi array at GANIL. Nucl. Instrum. Methods Phys. Res. A, 855, 1–12.
Abstract: The Advanced GAmma Tracking Array (AGATA) has been installed at the GANIL facility, Caen-France. This setup exploits the stable and radioactive heavy-ions beams delivered by the cyclotron accelerator complex of GANIL. Additionally, it benefits from a large palette of ancillary detectors and spectrometers to address in-beam gamma-ray spectroscopy of exotic nuclei. The set-up has been designed to couple AGATA with a magnetic spectrometer, charged-particle and neutron detectors, scintillators for the detection of high-energy gamma rays and other devices such as a plunger to measure nuclear lifetimes. In this paper, the design and the mechanical characteristics of the set-up are described. Based on simulations, expected performances of the AGATA l pi array are presented.
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ANTARES Collaboration(Albert, A. et al), Barrios-Marti, J., Hernandez-Rey, J. J., Illuminati, G., Lotze, M., Tönnis, C., et al. (2017). Search for high-energy neutrinos from bright GRBs with ANTARES. Mon. Not. Roy. Astron. Soc., 469(1), 906–915.
Abstract: Gamma-ray bursts are thought to be sites of hadronic acceleration, thus neutrinos are expected from the decay of charged particles, produced in p gamma interactions. The methods and results of a search for muon neutrinos in the data of the ANTARES neutrino telescope from four bright GRBs (GRB 080916C, GRB 110918A, GRB 130427A and GRB 130505A) observed between 2008 and 2013 are presented. Two scenarios of the fireball model have been investigated: the internal shock scenario, leading to the production of neutrinos with energies mainly above 100 TeV, and the photospheric scenario, characterized by a low-energy component in neutrino spectra due to the assumption of neutrino production closer to the central engine. Since no neutrino events have been detected in temporal and spatial coincidence with these bursts, upper limits at 90 per cent confidence level on the expected neutrino fluxes are derived. The non-detection allows for directly constraining the bulk Lorentz factor of the jet Gamma and the baryon loading f(p).
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Camarero, D., de Azcarraga, J. A., & Izquierdo, J. M. (2017). Bosonic D=11 supergravity from a generalized Chern-Simons action. Nucl. Phys. B, 923, 633–652.
Abstract: It is shown that the action of the bosonic sector of D= 11supergravity may be obtained by means of a suitable scaling of the originally dimensionless fields of a generalized Chern-Simons action. This follows from the eleven-form CS-potential of the most general linear combination of closed, gauge invariant twelve-forms involving the sp(32)-valued two-form curvatures supplemented by a three-form field. In this construction, the role of the skewsymmetric four-index auxiliary function needed for the first order formulation of D= 11supergravity is played by the gauge field associated with the five Lorentz indices generator of the bosonic sp(32) subalgebra of osp(1|32).
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Wang, E., Xie, J. J., Liang, W. H., Guo, F. K., & Oset, E. (2017). Role of a triangle singularity in the gamma p -> K+Lambda (1405) reaction. Phys. Rev. C, 95(1), 015205–9pp.
Abstract: We show the effects of a triangle singularity mechanism for the gamma p -> K+Lambda(1405) reaction. The mechanism has a N-* resonance around 2030 MeV, which decays into K*Sigma. The K-* decays to K+ pi, and the pi Sigma merge to form the Lambda (1405). This mechanism produces a peak around root s = 2110 MeV, and has its largest contribution around cos theta= 0. The addition of this mechanism to other conventional ones leads to a good reproduction of d sigma/dcos theta and the integrated cross section around this energy, providing a solution to a problem encountered in previous theoretical models.
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Ilner, A., Cabrera, D., Markert, C., & Bratkovskaya, E. (2017). K* vector meson resonance dynamics in heavy-ion collisions. Phys. Rev. C, 95(1), 014903–15pp.
Abstract: We study the strange vector meson (K*, (K) over bar*) dynamics in relativistic heavy-ion collisions based on the microscopic parton-hadron-string dynamics (PHSD) transport approach which incorporates partonic and hadronic degrees of freedom, a phase transition from hadronic to partonic matter-quark-gluon-plasma (QGP)-and a dynamical hadronization of quarks and antiquarks as well as final hadronic interactions. We investigate the role of in-medium effects on the K*, (K) over bar* meson dynamics by employing Breit-Wigner spectral functions for the K* with self-energies obtained from a self-consistent coupled-channelG-matrix approach. Furthermore, we confront the PHSD calculations with experimental data for p + p, Cu + Cu, and Au + Au collisions at energies up to root s(NN) = 200 GeV. Our analysis shows that, at relativistic energies, most of the final K* (observed experimentally) are produced during the late hadronic phase, dominantly by the K + pi -> K* channel, such that the fraction of the K* from the QGP is small and can hardly be reconstructed from the final observables. The influence of the in-medium effects on the K* dynamics at energies typical of the BNL Relativistic Heavy Ion Collider is rather modest due to their dominant production at low baryon densities (but high meson densities); however, it increases with decreasing beam energy. Moreover, we find that the additional cut on the invariant-mass region of the K* further influences the shape and the height of the final spectra. This imposes severe constraints on the interpretation of the experimental results.
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