Morales, A. I. et al. (2017). Type II shell evolution in A=70 isobars from the N >= 40 island of inversion. Phys. Lett. B, 765, 328–333.
Abstract: The level structures of Co-70 and Ni-70, populated from the Chi decay of Fe-70, have been investigated using beta-delayed gamma-ray spectroscopy following in-flight fission of a U-238 beam. The experimental results are compared to Monte-Carlo Shell-Model calculations including the pf + g(9/2) + d(5/2) orbitals. The strong population of a (1(+)) state at 274 keV in Co-70 is at variance with the expected excitation energy of 1 MeV from near spherical single-particle estimates. This observation indicates a dominance of prolate deformed intruder configurations in the low-lying levels, which coexist with the normal near spherical states. It is shown that the 13 decay of the neutron-rich A = 70 isobars from the new island of inversion to the Z = 28 closed-shell regime progresses in accordance with a newly reported type of shell evolution, the so-called Type II, which involves many particle-hole excitations across energy gaps.
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Fonseca, R. M., & Hirsch, M. (2017). Gauge vectors and double beta decay. Phys. Rev. D, 95(3), 035033–14pp.
Abstract: We discuss contributions to neutrinoless double beta (0 nu beta beta) decay involving vector bosons. The starting point is a list of all possible vector representations that may contribute to 0 nu beta beta decay via d = 9 or d = 11 operators at tree level. We then identify gauge groups which contain these vectors in the adjoint representation. Even though the complete list of vector fields that can contribute to 0 nu beta beta up to d = 11 is large (a total of 46 vectors), only a few of them can be gauge bosons of phenomenologically realistic groups. These latter cases are discussed in some more detail, and lower (upper) limits on gauge boson masses (mixing angles) are derived from the absence of 0 nu beta beta decay.
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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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Valencia, E. et al, Tain, J. L., Algora, A., Agramunt, J., Estevez, E., Jordan, M. D., et al. (2017). Total absorption gamma-ray spectroscopy of the beta-delayed neutron emitters Br-87, Br-88, and Rb-94. Phys. Rev. C, 95(2), 024320–18pp.
Abstract: We investigate the decay of Br-87,Br-88 and Rb-94 using total absorption gamma-ray spectroscopy. These important fission products are beta-delayed neutron emitters. Our data show considerable beta gamma intensity, so far unobserved in high-resolution gamma-ray spectroscopy, from states at high excitation energy. We also find significant differences with the beta intensity that can be deduced from existing measurements of the beta spectrum. We evaluate the impact of the present data on reactor decay heat using summation calculations. Although the effect is relatively small it helps to reduce the discrepancy between calculations and integral measurements of the photon component for U-235 fission at cooling times in the range 1-100 s. We also use summation calculations to evaluate the impact of present data on reactor antineutrino spectra. We find a significant effect at antineutrino energies in the range of 5 to 9 MeV. In addition, we observe an unexpected strong probability for. emission from neutron unbound states populated in the daughter nucleus. The. branching is compared to Hauser-Feshbach calculations, which allow one to explain the large value for bromine isotopes as due to nuclear structure. However the branching for Rb-94, although much smaller, hints of the need to increase the radiative width gamma by one order of magnitude. This increase in gamma would lead to a similar increase in the calculated (n, gamma) cross section for this very neutron-rich nucleus with a potential impact on r process abundance calculations.
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Debastiani, V. R., Aceti, F., Liang, W. H., & Oset, E. (2017). Revising the f(1)(1420) resonance. Phys. Rev. D, 95(3), 034015–10pp.
Abstract: We have studied the production and decay of the f(1) (1285) into pi a(0)(980) and K* (K) over bar as a function of the mass of the resonance and find a shoulder around 1400 MeV, tied to a triangle singularity, for the pi a(0)(980) mode, and a peak around 1420 MeV with about 60 MeV width for the K* (K) over bar mode. Both of these features agree with the experimental information on which the f(1)(1420) resonance is based. In addition, we find that if the f(1)(1420) is a genuine resonance, coupling mostly to K* (K) over bar as seen experimentally, one finds unavoidably about a 20% fraction for pi a(0)(980) decay of this resonance, in drastic contradiction with all experiments. Altogether, we conclude that the f(1)(1420) is not a genuine resonance, but the manifestation of the pi a(0)(980) and K* (K) over bar decay modes of the f(1)(1285) at higher energies than the nominal one.
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Nys, J., Mathieu, V., Fernandez-Ramirez, C., Hiller Blin, A. N., Jackura, A., Mikhasenko, M., et al. (2017). Finite-energy sum rules in eta photoproduction off a nucleon. Phys. Rev. D, 95(3), 034014–20pp.
Abstract: The reaction gamma N -> eta N is studied in the high-energy regime (with photon lab energies E gamma(lab) > 4 GeV) using information from the resonance region through the use of finite-energy sum rules. We illustrate how analyticity allows one to map the t dependence of the unknown Regge residue functions. We provide predictions for the energy dependence of the beam asymmetry at high energies.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Search for lepton-flavour-violating decays of the Higgs and Z bosons with the ATLAS detector. Eur. Phys. J. C, 77(2), 70–31pp.
Abstract: Direct searches for lepton flavour violation in decays of the Higgs and Z bosons with the ATLAS detector at the LHC are presented. The following three decays are considered: H -> e tau, H -> μtau, and Z -> μtau. The searches are based on the data sample of proton-proton collisions collected by the ATLAS detector corresponding to an integrated luminosity of 20.3 fb(-1) at a centre-of-mass energy of root s = 8 TeV. No significant excess is observed, and upper limits on the lepton-flavour-violating branching ratios are set at the 95% confidence level: Br(H -> e tau) < 1.04%, Br(H -> μtau) < 1.43%, and Br(Z -> μtau) < 1.69 x 10(-5).
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ANTARES Collaboration(Adrian-Martinez, S. et al), Baret, B., Barrios-Marti, J., Hernandez-Rey, J. J., Sanchez-Losa, A., Tönnis, C., et al. (2017). Stacked search for time shifted high energy neutrinos from gamma ray bursts with the ANTARES neutrino telescope. Eur. Phys. J. C, 77(1), 20–10pp.
Abstract: A search for high-energy neutrino emission correlated with gamma-ray bursts outside the electromagnetic prompt-emission time window is presented. Using a stacking approach of the time delays between reported gammaray burst alerts and spatially coincident muon-neutrino signatures, data from the Antares neutrino telescope recorded between 2007 and 2012 are analysed. One year of public data from the IceCube detector between 2008 and 2009 have been also investigated. The respective timing profiles are scanned for statistically significant accumulations within 40 days of the Gamma Ray Burst, as expected from Lorentz Invariance Violation effects and some astrophysical models. No significant excess over the expected accidental coincidence rate could be found in either of the two data sets. The average strength of the neutrino signal is found to be fainter than one detectable neutrino signal per hundred gamma-ray bursts in the Antares data at 90% confidence level.
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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). Measurement of forward t(t)over-bar, W + b(b)over-bar and W+ c(c)over-bar production in ppc ollisions at root s=8 TeV. Phys. Lett. B, 767, 110–120.
Abstract: The production of t (t) over bar, W + b (b) over bar and W+ c (c) over bar is studied in the forward region of proton-proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98 +/- 0.02 fb(-1). The Wbosons are reconstructed in the decays W -> lv, where l denotes muon or electron, while the b and cquarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions.
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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). Measurement of CP asymmetry in D-0 -> K- K+ decays. Phys. Lett. B, 767, 177–187.
Abstract: A measurement of the time-integrated CP asymmetry in the Cabibbo-suppressed decay D-0 -> K- K+ is performed using pp collision data, corresponding to an integrated luminosity of 3 fb(-1), collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The flavour of the charm meson at production is determined from the charge of the pion in D*(+) -> D-0 pi(+) and D*(-) -> (D) over bar (0)pi(-) decays. The time-integrated CP asymmetry A(CP)(K- K+) is obtained assuming negligible CP violation in charm mixing and in Cabibbo-favoured D-0 -> K- pi(+), D+ -> K- pi(+) pi(+) and D+ -> (K) over bar (0)pi(+) decays used as calibration channels. It is found to be A(CP)(K- K+) = (0.14 +/- 0.15 (stat) +/- 0.10 (syst))%. A combination of this result with previous LHCb measurements yields A(CP)(K- K+) = (0.04 +/- 0.12 (stat) +/- 0.10 (syst))%, A(CP)(pi(-) pi(+)) = (0.07 +/- 0.14 (stat) +/- 0.11 (syst))%. These are the most precise measurements from a single experiment. The result for ACP(K- K+) is the most precise determination of a time-integrated CPasymmetry in the charm sector to date, and neither measurement shows evidence of CP asymmetry.
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