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Ren, X. L., Alvarez-Ruso, L., Geng, L. S., Ledwig, T., Meng, J., & Vicente Vacas, M. J. (2017). Consistency between SU(3) and SU(2) covariant baryon chiral perturbation theory for the nucleon mass. Phys. Lett. B, 766, 325–333.
Abstract: Treating the strange quark mass as a heavy scale compared to the light quark mass, we perform a matching of the nucleon mass in the SU(3) sector to the two-flavor case in covariant baryon chiral perturbation theory. The validity of the 19low-energy constants appearing in the octet baryon masses up to next-to-next-to-next-to-leading order[1] is supported by comparing the effective parameters (the combinations of the 19couplings) with the corresponding low-energy constants in the SU(2) sector[2]. In addition, it is shown that the dependence of the effective parameters and the pion-nucleon sigma term on the strange quark mass is relatively weak around its physical value, thus providing support to the assumption made in Ref.[2] that the SU(2) baryon chiral perturbation theory can be applied to study n(f) = 2 + 1lattice QCD simulations as long as the strange quark mass is close to its physical value.
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Gutsche, T., Hiller Blin, A. N., Kovalenko, S., Kuleshov, S., Lyubovitskij, V. E., & Vicente Vacas, M. J. (2017). CP-violating decays of the pseudoscalars eta and eta' and their connection to the electric dipole moment of the neutron. Phys. Rev. D, 95(3), 036022–9pp.
Abstract: Using the present upper bound on the neutron electric dipole moment, we give an estimate for the upper limit of the CP-violating couplings of the eta(eta') to the nucleon. Using this result, we then derive constraints on the CP-violating eta(eta')pi pi couplings, which define the two-pion CP-violating decays of the eta and eta' mesons. Our results are relevant for the running and planned measurements of rare decays of the. eta and eta' mesons by the GlueX Collaboration at JLab and the LHCb Collaboration at CERN.
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Rinaldi, M., & Ceccopieri, F. A. (2017). Relativistic effects in model calculations of double parton distribution functions. Phys. Rev. D, 95(3), 034040–9pp.
Abstract: In this paper we consider double-parton distribution functions (dPDFs), which are the main nonperturbative ingredients appearing in the double-parton scattering cross section formula in hadronic collisions. By using recent calculation of dPDFs by means of constituent quark models within the so-called light-front approach, we investigate the role of relativistic effects on dPDFs. We find, in particular, that the so-called Melosh operators, which allow us to properly convert the LF spin into the canonical one and incorporate a proper treatment of boosts, produce sizeable effects on dPDFs. We discuss specific partonic correlations induced by these operators in the transverse plane which are relevant to the proton structure, and we study under which conditions these results are stable against variations in the choice of the proton wave function.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Search for dark matter in association with a Higgs boson decaying to b-quarks in pp collisions at root s=13 TeV with the ATLAS detector. Phys. Lett. B, 765, 11–31.
Abstract: A search for dark matter pair production in association with a Higgs boson decaying to a pair of bottom quarks is presented, using 3.2 fb(-1) of pp collisions at a centre-of-mass energy of 13 TeV collected by the ATLAS detector at the LHC. The decay of the Higgs boson is reconstructed as a high-momentum b (b) over bar system with either a pair of small-radius jets, or a single large-radius jet with substructure. The observed data are found to be consistent with the expected backgrounds. Results are interpreted using a simplified model with a gauge boson mediating the interaction between dark matter and the Standard Model as well as a two-Higgs-doublet model containing an additional Z' boson which decays to a Standard Model Higgs boson and a new pseudoscalar Higgs boson, the latter decaying into a pair of dark matter particles.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Search for new resonances decaying to a W or Z boson and a Higgs boson in the l(+)l(-)b(b)over-bar, l nu b(b)over-bar, and nu(nu)over-barb(b)over-bar channels with pp collisions at root s=13 TeV with the ATLAS detector. Phys. Lett. B, 765, 32–52.
Abstract: A search is presented for new resonances decaying to a W or Z boson and a Higgs boson in the l(+)l(-)b (b) over bar, l nu b (b) over bar, and nu(nu) over barb (b) over bar channels in pp collisions at root s = 13 TeV with the ATLAS detector at the Large Hadron Collider using a total integrated luminosity of 3.2 fb(-1). The search is conducted by looking for a localized excess in the WH/ZH invariant or transverse mass distribution. No significant excess is observed, and the results are interpreted in terms of constraints on a simplified model based on a phenomenological Lagrangian of heavy vector triplets.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Measurement of W boson angular distributions in events with high transverse momentum jets at root s=8 TeV using the ATLAS detector. Phys. Lett. B, 765, 132–153.
Abstract: The W boson angular distribution in events with high transverse momentum jets is measured using data collected by the ATLAS experiment from proton-proton collisions at a centre-of-mass energy root s = 8 TeV at the Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb(-1). The focus is on the contributions to W + jets processes from real W emission, which is achieved by studying events where a muon is observed close to a high transverse momentum jet. At small angular separations, these contributions are expected to be large. Various theoretical models of this process are compared to the data in terms of the absolute cross-section and the angular distributions of the muon from the leptonic W decay.
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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). Search for the suppressed decays B+ -> K+K+pi(-) and B+ -> pi(+)pi K-+(-). Phys. Lett. B, 765, 307–316.
Abstract: A search is made for the highly-suppressed B meson decays B+ -> K+K+pi(-) and B+ -> pi(+)pi K-+(-) using a data sample corresponding to an integrated luminosity of 3.0 fb(-1) collected by the LHCb experiment in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. No evidence is found for the decays, and upper limits at 90% confidence level are determined to be B(B+ -> K+K+pi(-))< 1.1 x 10(-8) and B(B+ -> pi(+)pi K-+(-)) < 4.6 x 10(-8).
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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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