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Arbelaez, C., Cepedello, R., Helo, J. C., Hirsch, M., & Kovalenko, S. (2022). How many 1-loop neutrino mass models are there? J. High Energy Phys., 08(8), 023–29pp.
Abstract: It is well-known that at tree-level the d = 5 Weinberg operator can be generated in exactly three different ways, the famous seesaw models. In this paper we study the related question of how many phenomenologically consistent 1-loop models one can construct at d=5. First, we discuss that there are two possible classes of 1-loop neutrino mass models, that allow avoiding stable charged relics: (i) models with dark matter candidates and (ii) models with “exits”. Here, we define “exits” as particles that can decay into standard model fields. Considering 1-loop models with new scalars and fermions, we find in the dark matter class a total of (115+203) models, while in the exit class we find (38+368) models. Here, 115 is the number of DM models, which require a stabilizing symmetry, while 203 is the number of models which contain a dark matter candidate, which maybe accidentally stable. In the exit class the 38 refers to models, for which one (or two) of the internal particles in the loop is a SM field, while the 368 models contain only fields beyond the SM (BSM) in the neutrino mass diagram. We then study the RGE evolution of the gauge couplings in all our 1-loop models. Many of the models in our list lead to Landau poles in some gauge coupling at rather low energies and there is exactly one model which unifies the gauge couplings at energies above 10(15) GeV in a numerically acceptable way.
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Portillo-Sanchez, D., Escribano, P., & Vicente, A. (2023). Ultraviolet extensions of the Scotogenic model. J. High Energy Phys., 08(8), 023–35pp.
Abstract: The Scotogenic model is a popular scenario that induces radiative Majorana neutrino masses and includes a weakly-interacting dark matter candidate. We classify all possible ultraviolet extensions of the Scotogenic model in which (i) the dark DOUBLE-STRUCK CAPITAL Z(2) parity emerges at low energies after the spontaneous breaking of a global U(1)(L) lepton number symmetry, and (ii) the low-energy effective theory contains a naturally small lepton number breaking parameter, suppressed by the mass of a heavy mediator integrated out at tree-level. We find 50 such models and discuss two of them in detail to illustrate our setup. We also discuss some general aspects of the phenomenology of the models in our classification, exploring possible lepton flavor violating signals, collider signatures and implications for dark matter. The phenomenological prospects of these scenarios are very rich due to the presence of additional scalar states, including a massless Goldstone boson.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2014). Search for strong production of supersymmetric particles in final states with missing transverse momentum and at least three b-jets at root s=8 TeV proton-proton collisions with the ATLAS detector. J. High Energy Phys., 10(10), 024–53pp.
Abstract: This paper reports the results of a search for strong production of supersymmetric particles in 20.1 fb(-1) of proton-proton collisions at a centre-of-mass energy of 8 TeV using the ATLAS detector at the LHC. The search is performed separately in events with either zero or at least one high-p (T) lepton (electron or muon), large missing transverse momentum, high jet multiplicity and at least three jets identified as originated from the fragmentation of a b-quark. No excess is observed with respect to the Standard Model predictions. The results are interpreted in the context of several supersymmetric models involving gluinos and scalar top and bottom quarks, as well as a mSUGRA/CMSSM model. Gluino masses up to 1340 GeV are excluded, depending on the model, significantly extending the previous ATLAS limits.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Study of eta-eta ' mixing from measurement of B-(s)(0) -> J/psi eta((')) decay rates. J. High Energy Phys., 01(1), 024–24pp.
Abstract: A study of B and B-s(0) meson decays into J/psi eta and J/psi eta' final states is performed using a data set of proton-proton collisions at centre-of-mass energies of 7 and 8 TeV, collected by the LCHb experiment and corresponding to 3.0 fb(-1) of integrated luminosity. The decay B-0 -> J/psi eta' is observed for the first time. The following ratios of branching fractions are measured: B(B-0 -> J psi eta')/B(B-s(0) -> J psi eta') = (2.28 +/- 0.65 (stat) +/- 0.010 (syst) +/- 0.13 (f(s)/f(d)) x 10(-2) , B(B-0 -> J psi eta')/B(B-s(0) -> J psi eta') = (1.85 +/- 0.65 (stat) +/- 0.09 (syst) +/- 0.11 (f(s)/f(d)) x 10(-2) where the third uncertainty is related to the present knowledge of f(s)/f(d), the ratio between the probabilities for a b quark to form a B-s(0) or a B-0 meson. The branching fraction ratios are used to determine the parameters of eta-eta' meson mixing. In addition, the first evidence for the decay B-s(0) -> psi(2S)' is reported, and the relative branching fraction is measured, B(B-s(0) -> psi(2S)eta')/B(B-s(0) -> J psi eta') = (38.7 +/- 9.0 (stat) +/- 1.3 (syst) +/- 0.9(B)) x 10(-2), where the third uncertainty is due to the limited knowledge of the branching fractions of J/psi and psi(2S) mesons.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Precise measurements of the properties of the B-1(5721)(0,+) and B-2*(5747)(0,+) states and observation of B-+,B-0 pi(-,+) mass structures. J. High Energy Phys., 04(4), 024–27pp.
Abstract: Invariant mass distributions of B (+) pi (-) and B (0) pi (+) combinations are investigated in order to study excited B mesons. The analysis is based on a data sample corresponding to 3.0 fb(-1) of pp collision data, recorded by the LHCb detector at centre-of-mass energies of 7 and 8 TeV. Precise measurements of the masses and widths of the B (1)(5721)(0,+) and B (2)(5747)(0,+) states are reported. Clear enhancements, particularly prominent at high pion transverse momentum, are seen over background in the mass range 5850-6000 MeV in both B (+) pi (-) and B (0) pi (+) combinations. The structures are consistent with the presence of four excited B mesons, labelled B (J) (5840)(0,+) and B (J) (5960)(0,+), whose masses and widths are obtained under different hypotheses for their quantum numbers.
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