Babichev, E., & Fabbri, A. (2014). Stability analysis of black holes in massive gravity: A unified treatment. Phys. Rev. D, 89(8), 081502–5pp.
Abstract: We consider the analytic solutions of massive (bi) gravity which can be written in a simple form using advanced Eddington-Finkelstein coordinates. We analyze the stability of these solutions against radial perturbations. First we recover the previously obtained result on the instability of the bidiagonal bi-Schwarzschild solutions. In the nonbidiagonal case (which contains, in particular, the Schwarzschild solution with Minkowski fiducial metric), we show that generically there are physical spherically symmetric perturbations, but no unstable modes.
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Hernandez, E., Nieves, J., & Valverde, M. (2010). Coherent pion production off nuclei at T2K and MiniBooNE energies revisited. Phys. Rev. D, 82(7), 077303–4pp.
Abstract: As a result of a new improved fit to old bubble chamber data of the dominant axial C-5(A) nucleon-to-delta form factor, and due to the relevance of this form factor for neutrino induced coherent pion production, we reevaluate our model predictions in [Phys. Rev. D 79, 013002 ( 2009)] for different observables of the latter reaction. Central values for the total cross sections increase by 20%-30%, while differential cross sections do not change their shape appreciably. Furthermore, we also compute the uncertainties on total, differential, and flux-averaged cross sections induced by the errors in the determination of C-5(A). Our new results turn out to be compatible within about 1 sigma with the former ones. Finally, we stress the existing tension between the recent experimental determination of the sigma(CCcoh pi(+))/sigma(NCcoh pi(0)) ratio by the SciBooNE Collaboration and the theoretical predictions.
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King, S. F., Molina Sedgwick, S., Parke, S. J., & Prouse, N. W. (2020). Effects of matter density profiles on neutrino oscillations for T2HK and T2HKK. Phys. Rev. D, 101(7), 076019–16pp.
Abstract: This paper explores the effects of changes in matter density profiles on neutrino oscillation probabilities, and whether these could potentially be seen by the future Hyper-Kamiokande long-baseline oscillation experiment (T2HK). The analysis is extended to include the possibility of having an additional detector in Korea (T2HKK). In both cases, we find that these effects will be immeasurable, as the magnitudes of the changes in the oscillation probabilities induced in all density profile scenarios considered here remain smaller than the estimated experimental sensitivity to the oscillation probabilities of each experiment, for both appearance and disappearance channels. Therefore, we conclude that using a constant density profile is sufficient for both the T2HK and T2HKK experiments.
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Feijoo, A., Magas, V. K., Ramos, A., & Oset, E. (2015). Lambda(b) -> J/psi K Xi decay and the higher order chiral terms of the meson baryon interaction. Phys. Rev. D, 92(7), 076015–10pp.
Abstract: We study the weak decay of the Lambda(b) into J/psi K Xi. and J/psi eta Lambda states, and relate these processes to the Lambda(b) -> J/psi(K) over barN decay mode. The elementary weak transition at the quark level proceeds via the creation of a J/psi meson and an excited sud system with I = 0, which upon hadronization leads to (K) over barN or eta Lambda pairs. These states undergo final-state interaction in coupled channels and produce a final meson-baryon pair. The K. state only occurs via rescattering, hence making the Lambda(b) -> J/psi K Xi process very sensitive to the details of the meson-baryon interaction in strangeness S = -1 and isospin I = 0. We show that the corresponding invariant mass distribution is dominated by the next-to-leading-order terms of the chiral interaction. The I = 0 selectivity of this decay, and its large sensitivity to the higher-order terms, makes its measurement very useful and complementary to the K- p -> K Xi cross section data. The rates of the Lambda(b) -> J/psi K Xi and Lambda(b) -> J/psi eta Lambda invariant mass distributions are sizable compared to those of the Lambda(b) -> J/psi(K) over barN decay, which is measured experimentally, and thus, we provide arguments for an experimental determination of these decay modes that will help us understand better the chiral dynamics at higher energies.
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Kirpichnikov, D. V., Sieber, H., Molina Bueno, L., Crivelli, P., & Kirsanov, M. M. (2021). Probing hidden sectors with a muon beam: Total and differential cross sections for vector boson production in muon bremsstrahlung. Phys. Rev. D, 104(7), 076012–13pp.
Abstract: Vector bosons, such as dark photon A' or Z', can couple to muons and be produced in the bremsstrahlung reaction mu(-) + N -> mu(-) + N + A'(Z'). Their possible subsequent invisible decay can be detected in fixed target experiments through missing energy/momentum signature. In such experiments, not only is the energy transfer to A'(Z') important but also the recoil muon angle psi μ0. In this paper, we derive the total and the double differential cross sections involved in this process using the phase space Weizsacker-Williams and improved Weizsacker-Williams approximations, as well as using exact-tree-level calculations. As an example, we compare the derived cross sections and resulting signal yields in the NA64 μexperiment that uses a 160 GeV muon beam at the CERN Super Proton Synchrotron accelerator. We also discuss its impact on the NA64 μexpected sensitivity to explore the (g – 2)(mu) anomaly favored region with a Z' boson considering 10(12) muons accumulated on target.
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Chachamis, G., Hentschinski, M., Madrigal Martinez, J. D., & Sabio Vera, A. (2013). Next-to-leading order corrections to the gluon-induced forward jet vertex from the high energy effective action. Phys. Rev. D, 87(7), 076009–11pp.
Abstract: We determine both real and virtual next-to-leading order corrections to the gluon-induced forward jet vertex from the high energy effective action proposed by Lipatov. For these calculations we employ the same regularization and subtraction formalism developed in our previous work on the quark-initiated vertex. We find agreement with previous results in the literature.
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Lami, A., Portoles, J., & Roig, P. (2016). Lepton flavor violation in hadronic decays of the tau lepton in the simplest little Higgs model. Phys. Rev. D, 93(7), 076008–14pp.
Abstract: We study lepton flavor violating hadron decays of the tau lepton within the simplest little Higgs model. Namely we consider tau -> mu(P, V, PP) where P and V are short for a pseudoscalar and a vector meson. We find that, in the most positive scenarios, branching ratios for these processes are predicted to be, at least, four orders of magnitude smaller than present experimental bounds.
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Guevara, A., Lopez Castro, G., & Roig, P. (2022). Improved description of dilepton production in tau(-) -> nu(tau)P(- )decays. Phys. Rev. D, 105(7), 076007–15pp.
Abstract: Recently, the Belle Collaboration reported the first measurements of the tau(-) -> nu(tau)pi(-) e(+) e(-) branching fraction and the spectrum of the pion-dielectron system. In an analysis previous to Belle's results, we evaluated this branching fraction which turned out to be compatible with that reported by Belle, although with a large uncertainty. This is the motivation to seek for improvement on our previous evaluation of tau(-) -> nu(tau)pi(-) l(+) l(-) decays (l = e, mu). In this paper we improve our calculation of the WP-gamma* vertex by including flavor-symmetry breaking effects in the framework of the resonance chiral theory. We impose QCD short-distance behavior to constrain most parameters and data on the pi(-) e(+) e(-) spectrum reported by the Belle Collaboration to fix the remaining free ones. As a result, improved predictions for the branching ratios and hadronic/leptonic spectra are reported, which are in good agreement with observations. Analogous calculations for the strangeness-changing tau(-) -> nu(tau) K- l(+) l(-) transitions are reported for the first time. Albeit one expects the m(pi mu+ mu- )spectrum to be measured in Belle-II and the observables with l = e can be improved, it is rather unlikely that the K channels can be measured due to the suppression factor vertical bar V-ud/V-us vertical bar(2) = 0.05.
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Hidalgo-Duque, C., Nieves, J., & Pavon Valderrama, M. (2013). Light flavor and heavy quark spin symmetry in heavy meson molecules. Phys. Rev. D, 87(7), 076006–14pp.
Abstract: We propose an effective field theory incorporating light SU(3)-flavor and heavy quark spin symmetry to describe charmed meson-antimeson bound states. At lowest order the effective field theory entails a remarkable simplification: it only involves contact range interactions among the heavy meson and antimeson fields. We show that the isospin violating decays of the X(3872) can be used to constrain the interaction between the D and a (D) over bar* mesons in the isovector channel. As a consequence, we can rule out the existence of an isovector partner of the X(3872). If we additionally assume that the X(3915) and Y(4140) are D*(D) over bar* and D*(s)(D) over bar*(s) molecular states, we can determine the full spectrum of molecular states with isospin I = 0, 1/2 and 1.
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Braaten, E., Bruschini, R., He, L. P., Ingles, K., & Jiang, J. (2023). Evolution of charm-meson ratios in an expanding hadron gas. Phys. Rev. D, 107(7), 076006–6pp.
Abstract: We study the time evolution of the numbers of charm mesons after the kinetic freeze-out of the hadron gas produced by a central heavy-ion collision. The pi D* -> pi D* reaction rates have t-channel singularities that give contributions inversely proportional to the thermal width of the D. The ratio of the D0 and D+ production rates can differ significantly from those predicted using the measured D* branching fractions.
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