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Arbelaez, C., Helo, J. C., & Hirsch, M. (2019). Long-lived heavy particles in neutrino mass models. Phys. Rev. D, 100(5), 055001–15pp.
Abstract: All extensions of the standard model that generate Majorana neutrino masses at the electroweak scale introduce some heavy mediators, either fermions and/or scalars, weakly coupled to leptons. Here, by “heavy,” we mean implicitly the mass range between a few 100 GeV up to, say, roughly 2 TeV, such that these particles can be searched for at the LHC. We study decay widths of these mediators for several different tree-level neutrino mass models. The models we consider range from the simplest d = 5 seesaw up to d = 11 neutrino mass models. For each of the models, we identify the most interesting parts of the parameter space, where the heavy mediator fields are particularly long lived and can decay with experimentally measurable decay lengths. One has to distinguish two different scenarios, depending on whether fermions or scalars are the lighter of the heavy particles. For fermions, we find that the decay lengths correlate with the inverse of the overall neutrino mass scale. Thus, since no lower limit on the lightest neutrino mass exists, nearly arbitrarily long decay lengths can be obtained for the case in which fermions are the lighter of the heavy particles. For charged scalars, on the other hand, there exists a maximum value for the decay length in these models. This maximum value depends on the model and on the electric charge of the scalar under consideration but can at most be of the order of a few millimeters. Interestingly, independent of the model, this maximum occurs always in a region of parameter space, where leptonic and gauge boson final states have similar branching ratios, i.e., where the observation of lepton number-violating final states from scalar decays is possible.
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Dercks, D., Dreiner, H. K., Hirsch, M., & Wang, Z. S. (2019). Long-lived fermions at AL3X. Phys. Rev. D, 99(5), 055020–10pp.
Abstract: Recently Gligorov et al. [V. V. Gligorov et al., Phys. Rev. D 99, 015023 (2019)] proposed to build a cylindrical detector named AL3X close to the ALICE experiment at interaction point (IP) 2 of the LHC, aiming for discovery of long-lived particles (LLPs) during Run 5 of the HL-LHC. We investigate the potential sensitivity reach of this detector in the parameter space of different new-physics models with long-lived fermions namely heavy neutral leptons (HNLs) and light supersymmetric neutralinos, which have both not previously been studied in this context. Our results show that the AL3X reach can be complementary or superior to that of other proposed detectors such as CODEX-b, FASER, MATHUSLA and SHiP.
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Davesne, D., Pastore, A., & Navarro, J. (2019). Linear response theory in asymmetric nuclear matter for Skyrme functionals including spin-orbit and tensor terms. II. Charge exchange. Phys. Rev. C, 100(6), 064301–10pp.
Abstract: We present the formalism of linear response theory both at zero and finite temperature in the case of asymmetric nuclear matter excited by an isospin flip probe. The particle-hole interaction is derived from a general Skyrme functional that includes spin-orbit and tensor terms. Response functions are obtained by solving a closed algebraic system of equations. Spin strength functions are analyzed for typical values of density, momentum transfer, asymmetry, and temperature. We evaluate the role of statistical errors related to the uncertainties of the coupling constants of the Skyrme functional and thus determine the confidence interval of the resulting response function.
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Yu, Q. X., Liang, W. H., Bayar, M., & Oset, E. (2019). Line shape and D-(*())(D)over-bar(()*()) probabilities of psi(3770) from the e(+) e(-) -> D(D)over-bar reaction. Phys. Rev. D, 99(7), 076002–17pp.
Abstract: We have performed a calculation of the D (D) over bar, D (D) over bar*, D*(D) over bar, D*(D) over bar* components in the wave function of the psi(3770). For this we make use of the P-3(0) model to find the coupling of psi(3770) to these components, that with an elaborate angular momentum algebra can be obtained with only one parameter. Then we use data for the e(+)e(-) -> D (D) over bar reaction, from where we determine a form factor needed in the theoretical framework, as well as other parameters needed to evaluate the meson-meson self-energy of the psi(3770). Once this is done we determine the Z probability to still have a vector core and the probability to have the different meson components. We find Z about 80%-85%, and the individual meson-meson components are rather small, providing new empirical information to support the largely q (q) over bar component of vector mesons, and the psi(3770) in particular. A discussion is done of the meaning of the terms obtained for the case of the open channels where the concept of probability cannot be strictly used.
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Ellis, J., Mavromatos, N. E., Sakharov, A. S., & Sarkisyan-Grinbaum, E. K. (2019). Limits on neutrino Lorentz violation from multimessenger observations of TXS 0506+056. Phys. Lett. B, 789, 352–355.
Abstract: The observation by the IceCube Collaboration of a high-energy (E greater than or similar to 200 TeV) neutrino from the direction of the blazar TXS 0506+056 and the coincident observations of enhanced gamma-ray emissions from the same object by MAGIC and other experiments can be used to set stringent constraints on Lorentz violation in the propagation of neutrinos that is linear in the neutrino energy: Delta v = -E/M-1, where Delta v is the deviation from the velocity of light, and M-1 is an unknown high energy scale to be constrained by experiment. Allowing for a difference in neutrino and photon propagation times of similar to 10 days, we find that M-1 greater than or similar to 3 x 10(16) GeV. This improves on previous limits on linear Lorentz violation in neutrino propagation by many orders of magnitude, and the same is true for quadratic Lorentz violation.
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