BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2017). Search for Invisible Decays of a Dark Photon Produced in e(+)e(-) Collisions at BABAR. Phys. Rev. Lett., 119(13), 131804–7pp.
Abstract: We search for single-photon events in 53 fb(-1) of e(+)e(-) collision data collected with the BABAR detector at the PEP-II B-Factory. We look for events with a single high-energy photon and a large missing momentum and energy, consistent with production of a spin-1 particle A' through the process e(+)e(-) -> gamma A'; A' -> invisible. Such particles, referred to as “dark photons,” are motivated by theories applying a U(1) gauge symmetry to dark matter. We find no evidence for such processes and set 90% confidence level upper limits on the coupling strength of A' to e(+)e(-) in the mass range m(A') <= 8 GeV. In particular, our limits exclude the values of the A' coupling suggested by the dark-photon interpretation of the muon (g – 2)(mu) anomaly, as well as a broad range of parameters for the dark-sector models.
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Barenboim, G., & Park, W. I. (2017). Impact of CP-violation on neutrino lepton number asymmetries revisited. Phys. Lett. B, 765, 371–376.
Abstract: We revisit the effect of the (Dirac) CP-violating phase on neutrino lepton number asymmetries in both mass- and flavor-basis. We found that, even if there are sizable effects on muon- and tau-neutrino asymmetries, the effect on the asymmetry of electron-neutrinos is at most similar to the upper bound set by BBN for initial neutrino degeneracy parameters smaller than order unity. We also found that, for the asymmetries in mass-basis, the changes caused by CP-violation is of sub-% level which is unlikely to be accessible neither in the current nor in the forthcoming experiments.
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Garcilazo, H., Valcarce, A., & Vijande, J. (2017). Stable bound states of N's, Lambda's and Xi's. Rev. Mex. Fis., 63(5), 411–422.
Abstract: We review our recent work about the stability of strange few-body systems containing N's, Lambda's, and Xi's. We make use of local central Yukawa-type Malfliet-Tjon interactions reproducing the low-energy parameters and phase shifts of the nucleon-nucleon system and the latest updates of the hyperon-nucleon and hyperon-hyperon ESCO8c Nijmegen potentials. We solve the three-and four-body bound-state problems by means of Faddeev equations and a generalized Gaussian variational method, respectively. The hypertriton, Lambda np(I)J(P) = (1/2)1/2(+), is bound by 144 keV; the recently discussed Lambda nn (I)J(P) = (1/2)1/2(+) system is unbound, as well as the Lambda Lambda nn (I)J(P) = (1)0(+) system, being just above threshold. Our results indicate that the Xi NN, Xi Xi N and Xi Xi NN systems with maximal isospin might be bound.
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FLAG Working Group(Aoki, S. et al), & Della Morte, M. (2017). Review of lattice results concerning low-energy particle physics. Eur. Phys. J. C, 77(2), 112–228pp.
Abstract: We review lattice results related to pion, kaon, D- and B-meson physics with the aim of making them easily accessible to the particle-physics community. More specifically, we report on the determination of the light-quark masses, the form factor f(+)(0), arising in the semileptonic K -> pi transition at zero momentum transfer, as well as the decay constant ratio fK / f pi and its consequences for the CKM matrix elements V-us and V-ud. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of SU(2) L x SU(2) R and SU(3) L x SU(3) R Chiral Perturbation Theory. We review the determination of the B-K parameter of neutral kaon mixing as well as the additional four B parameters that arise in theories of physics beyond the StandardModel. The latter quantities are an addition compared to the previous review. For the heavy-quark sector, we provide results for m(c) and m(b) (also new compared to the previous review), as well as those for D- and B-meson-decay constants, form factors, and mixing parameters. These are the heavy-quark quantities most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. Finally, we review the status of lattice determinations of the strong coupling constant alpha(s).
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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). First Observation of a Baryonic B-s(0) Decay. Phys. Rev. Lett., 119(4), 041802–10pp.
Abstract: We report the first observation of a baryonic B-s(0) decay, B-s(0). p (Lambda) over barK(-), using proton-proton collision data recorded by the LHCb experiment at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb(-1). The branching fraction is measured to be B(B-s(0) -> p (Lambda) over bar K-)+ B(B-s(0) -> p (Lambda) over bar K+) [5.46 +/- 0.61 +/- 0.57 +/- 0.50(B) +/- 0.32(f(s)/(d))] x 10(-6), where the first uncertainty is statistical and the second systematic, the third uncertainty accounts for the experimental uncertainty on the branching fraction of the B-0 -> p (Lambda) over bar pi(-) decay used for normalization, and the fourth uncertainty relates to the knowledge of the ratio of b-quark hadronization probabilities f(s)/f(d).
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