Ilisie, V., & Pich, A. (2014). Low-mass fermiophobic charged Higgs phenomenology in two-Higgs-doublet models. J. High Energy Phys., 09(9), 089–32pp.
Abstract: After the recent discovery of a Higgs-like boson, the possibility of an enlarged scalar sector arises as a natural question. Experimental searches for charged scalars have been already performed with negative results. We analyze the phenomenology associated with a fermiophobic charged Higgs (it does not couple to fermions at tree level), in two-Higgs-doublet models. All present experimental bounds are evaded trivially in this case, and one needs to consider other decay and production channels. We study the associated production of a charged Higgs with either a W or a neutral scalar boson, and the relevant decays for a light fermiophobic charged Higgs. The interesting features of this scenario should result encouraging for the LHC collaborations to perform searches for such a particle.
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Binosi, D., Ibañez, D., & Papavassiliou, J. (2014). Nonperturbative study of the four gluon vertex. J. High Energy Phys., 09(9), 059–32pp.
Abstract: In this paper we study the nonperturbative structure of the SU(3) four-gluon vertex in the Landau gauge, concentrating on contributions quadratic in the metric. We employ an approximation scheme where “one-loop” diagrams are computed using fully dressed gluon and ghost propagators, and tree-level vertices. When a suitable kinematical configuration depending on a single momentum scale p is chosen, only two structures emerge: the tree-level four-gluon vertex, and a tensor orthogonal to it. A detailed numerical analysis reveals that the form factor associated with this latter tensor displays a change of sign (zero-crossing) in the deep infrared, and finally diverges logarithmically. The origin of this characteristic behavior is proven to be entirely due to the masslessness of the ghost propagators forming the corresponding ghost-loop diagram, in close analogy to a similar effect established for the three-gluon vertex. However, in the case at hand, and under the approximations employed, this particular divergence does not affect the form factor proportional to the tree-level tensor, which remains finite in the entire range of momenta, and deviates moderately from its naive tree-level value. It turns out that the kinematic configuration chosen is ideal for carrying out lattice simulations, because it eliminates from the connected Green's function all one-particle reducible contributions, projecting out the genuine one-particle irreducible vertex. Motivated by this possibility, we discuss in detail how a hypothetical lattice measurement of this quantity would compare to the results presented here, and the potential interference from an additional tensorial structure, allowed by Bose symmetry, but not encountered within our scheme.
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Gonzalez, P. (2014). Generalized screened potential model. J. Phys. G, 41(9), 095001–12pp.
Abstract: A new non relativistic quark model to calculate the spectrum of heavy quark mesons is developed. The model is based on an interquark potential interaction that implicitly incorporates screening effects from meson-meson configurations. An analysis of the bottomonium spectrum shows the appearance of extra states as compared to conventional non screened potential models.
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Ruiz-Femenia, P. (2014). First estimate of the NNLO nonresonant corrections to top-antitop threshold production at lepton colliders. Phys. Rev. D, 89(9), 097501–4pp.
Abstract: We compute the dominant term in the expansion in rho = 1 – M-w/m(t) of the unknown next-to-next-to-leading order nonresonant contributions to the e+ e(-) -> W+ W- b (b) over bar total cross section at energies close to the top-antitop threshold. Our analytic result disagrees with a previous calculation by other authors [A. A. Penin and J. H. Piclum, J. High Energy Phys. 01 (2012) 034]. We show that our determination has the correct infrared structure needed to cancel the divergences proportional to the top width arising in the resonant production of the same final state, and we point to a missing contribution in the computation of Penin and Piclum to explain the discrepancy.
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Simpson, G. S. et al, & Montaner-Piza, A. (2014). Yrast 6(+) Seniority Isomers of Sn-136,Sn-138. Phys. Rev. Lett., 113(13), 132502–6pp.
Abstract: Delayed gamma-ray cascades, originating from the decay of (6(+)) isomeric states, in the very neutron-rich, semimagic isotopes Sn-136,Sn-138 have been observed following the projectile fission of a U-238 beam at RIBF, RIKEN. The wave functions of these isomeric states are proposed to be predominantly a fully aligned pair of f(7/2) neutrons. Shell-model calculations, performed using a realistic effective interaction, reproduce well the energies of the excited states of these nuclei and the measured transition rates, with the exception of the B(E2; 6(+) -> 4(+)) rate of Sn-136, which deviates from a simple seniority scheme. Empirically reducing the nu f(7/2)(2) orbit matrix elements produces a 4(1)(+) state with almost equal seniority 2 and 4 components, correctly reproducing the experimental B(E2; 6(+) -> 4(+)) rate of Sn-136. These data provide a key benchmark for shell-model interactions far from stability.
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