Lattanzi, M., Lineros, R. A., & Taoso, M. (2014). Connecting neutrino physics with dark matter. New J. Phys., 16, 125012–19pp.
Abstract: The origin of neutrino masses and the nature of dark matter are two in most pressing open questions in modern astro-particle physics. We consider here the possibility that these two problems are related, and review some theoretical scenarios which offer common solutions. A simple possibility is that the dark matter particle emerges in minimal realizations of the seesaw mechanism, as in the majoron and sterile neutrino scenarios. We present the theoretical motivation for both models and discuss their phenomenology, confronting the predictions of these scenarios with cosmological and astrophysical observations. Finally, we discuss the possibility that the stability of dark matter originates from a flavor symmetry of the leptonic sector. We review a proposal based on an A(4) flavor symmetry.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Martinez-Vidal, F., et al. (2024). Study of the rare decay J/ψ → μ+μ-μ+μ-. J. High Energy Phys., 12(12), 062–25pp.
Abstract: The rare electromagnetic J/psi -> mu(+)mu(-)mu(+)mu(-) decay is observed with a significance greatly exceeding the discovery threshold, using proton-proton collision data collected by the LHCb experiment during 2016-2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb(-1). The rate of this decay is measured relative to that of the J/psi -> mu(+)mu(-) mode. Using the QED model for the four-muon decay in the efficiency estimation, its branching fraction is determined to be B(J/psi -> mu(+)mu(-)mu(+)mu(-)) = (1.13 +/- 0.10 +/- 0.05 +/- 0.01) x 10(-6), where the uncertainties are statistical, systematic and due to the uncertainty on the branching fraction of the J/psi -> mu(+)mu(-) decay.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Martinez-Vidal, F., et al. (2024). Analysis of Λ0b →pK- μ+ μ- decays. J. High Energy Phys., 12(12), 147–33pp.
Abstract: The differential branching fraction and angular coefficients of Lambda(0)(b) -> pK(-) mu(+) mu(-)decays are measured in bins of the dimuon mass squared and dihadron mass. The analysis is performed using a data set corresponding to 9 fb(-1) of integrated luminosity collected with the LHCb detector between 2011 and 2018. The data are consistent with receiving contributions from a mixture of. resonances with different spin-parity quantum numbers. The angular coefficients show a pattern of vector-axial vector interference that is a characteristic of the type of flavour-changing neutral-current transition relevant for these decays.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2020). Strong constraints on the b -> s gamma photon polarisation from B-0 -> K(*0)e(+)e(-) decays. J. High Energy Phys., 12(12), 081–25pp.
Abstract: An angular analysis of the B-0 -> K*(0)e(+)e(-) decay is performed using a data sample corresponding to an integrated luminosity of 9 fb(-1) of pp collisions collected with the LHCb experiment. The analysis is conducted in the very low dielectron mass squared (q(2)) interval between 0.0008 and 0.257 GeV2, where the rate is dominated by the B-0 -> K*(0)gamma transition with a virtual photon. The fraction of longitudinal polarisation of the K*(0) meson, F-L, is measured to be F-L = (4.4 +/- 2.6 +/- 1.4)%, where the first uncertainty is statistical and the second systematic. The A(T)(Re) observable, which is related to the lepton forward-backward asymmetry, is measured to be A(T)(Re) = -0.06 +/- 0.08 +/- 0.02. The A(T)((2)) and A(T)(Im) transverse asymmetries, which are sensitive to the virtual photon polarisation, are found to be A(T)((2)) = 0.11 +/- 0.10 +/- 0.02 and A(T)(Im) = 0.02 +/- 0.10 +/- 0.01. The results are consistent with Standard Model predictions and provide the world's best constraint on the b -> s gamma photon polarisation.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2020). Test of lepton universality with Lambda(0)(b) -> pK(-) l(+)l(-). J. High Energy Phys., 05(5), 40–27pp.
Abstract: The ratio of branching fractions of the decays -> pK(-)mu(+)mu(-),RpK-1}, is measured for the first time using proton-proton collision data corresponding to an integrated luminosity of 4.7 fb(-1) recorded with the LHCb experiment at center-of-mass energies of 7, 8 and 13 TeV. In the dilepton mass-squared range 0.1 < q(2)< 6.0 GeV2/c(4) and the pK(-) mass range m(pK(-)) < 2600 MeV/c(2), the ratio of branching fractions is measured to be RpK-1=1.17-0.16+0.18 +/- 0.0$$ {R}{pK}<^>{-1}={1.17}{-0.16}<^>{+0.18}\pm 0.07 $$\end{document}, where the first uncertainty is statistical and the second systematic. This is the first test of lepton universality with b baryons and the first observation of the decay -> pK(-)e(+)e(-).
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2021). Searches for 25 rare and forbidden decays of D+ and Ds+ mesons. J. High Energy Phys., 06(6), 044–24pp.
Abstract: A search is performed for rare and forbidden charm decays of the form D+-> hl+l -/+, where h(+/-) is a pion or kaon and l((')+/-) is an electron or muon. The measurements are performed using proton-proton collision data, corresponding to an integrated luminosity of 1.6 fb(-1), collected by the LHCb experiment in 2016. No evidence is observed for the 25 decay modes that are investigated and 90 % confidence level limits on the branching fractions are set between 1.4 x 10(-8) and 6.4 x 10(-6). In most cases, these results represent an improvement on existing limits by one to two orders of magnitude.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2018). First measurement of the CP-violating phase phi(dd)(s) in B-s(0) -> (K+pi(-))(K-pi(+)) decays. J. High Energy Phys., 03(3), 140–32pp.
Abstract: A flavour-tagged decay-time-dependent amplitude analysis of B-s(0) -> (K+pi(-))(K-pi(+)) decays is presented in the K-+/-pi(-/+) mass range from 750 to 1600 MeV/c(2). The analysis uses pp collision data collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb(-1). Several quasi-two-body decay modes are considered, corresponding to K-+/-pi(-/+) combinations with spin 0, 1 and 2, which are dominated by the K-0(*)(800)(0) and K-0(*)(1430)(0), the K*(892)(0) and the K-2(*)(1430)(0) resonances, respectively. The longitudinal polarisation fraction for the B-s(0) -> K-*(892)(0) (K*) over bar (892)(0) decay is measured as f(L) = 0.208 +/- 0.032 +/- 0.046, where the first uncertainty is statistical and the second is systematic. The first measurement of the mixing-induced CP-violating phase in phi(d (d) over bar)(s), in b -> d (s) over bars transitions is performed, yielding a value of phi(d (d) over bar)(s)= -0.10 +/- 0.13 (stat) +/- 0.14 (syst) rad.
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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). Observation of the suppressed decay Lambda(0)(b) -> p pi(-) mu(+) mu(-). J. High Energy Phys., 04(4), 029–16pp.
Abstract: The suppressed decay Lambda(0)(b) -> p pi(-) mu(+) mu(-), excluding the J/psi and psi(2S) -> mu(+) mu(-) resonances, is observed for the first time with a significance of 5.5 standard deviations. The analysis is performed with proton- proton collision data corresponding to an integrated luminosity of 3 fb(-1) collected with the LHCb experiment. The Lambda(0)(b) -> p pi(-) mu(+) mu(-) branching fraction is measured relative to the Lambda(0)(b) -> J/psi (-> mu(+) mu(-)) p pi(-) branching fraction giving B (Lambda(0)(b) -> p pi(-) mu(+) mu(-))/B(Lambda(0)(b) -> J/psi (-> mu(+) mu(-)) p pi(-)) = 0.044 +/- 0.012 +/- 0.007, where the first uncertainty is statistical and the second is systematic. This is the first observation of a b -> d transition in a baryonic 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 decays of neutral beauty mesons into four muons. J. High Energy Phys., 03(3), 001–19pp.
Abstract: A search for the non-resonant decays B-s(0) -> mu(+) mu(-) mu(+)mu(-) and B-0 -> mu(+) mu(-) mu(+) mu(-) is presented. The measurement is performed using the full Run 1 data set collected in proton-proton collisions by the LHCb experiment at the LHC. The data correspond to integrated luminosities of 1 and 2 fb(-1) collected at centre-of-mass energies of 7 and 8 TeV, respectively. No signal is observed and upper limits on the branching fractions of the non-resonant decays at 95% confidence level are determined to be B(B-s(0) -> mu(+) mu(-) mu(+)mu(-)) < 2.5 x 10(-9) B(B-0 -> mu(+) mu(-) mu(+) mu(-)) < 6.9 x 10(-10)
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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Search for the rare decay B-0 -> J/psi phi. Chin. Phys. C, 45(4), 043001–14pp.
Abstract: A search for the rare decay B-0 -> J/psi phi, is performed using pp collision data collected with the LHCb detector at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb(-1). No significant signal of the decay is observed and an upper limit of 1.1 x 10(-7) at 90% confidence level is set on the branching fraction.
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