LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Search for KS(L)0 → μ+ μ- μ+ μ- decays at LHCb. Phys. Rev. D, 108(3), L031102–12pp.
Abstract: A search for K-S(L)(0) -> mu(+) mu(-) mu(+) mu(-) decays is performed using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.1 fb(-1). No evidence for signal is found. The 90% confidence level upper limits are the first set for both decays and are B(K-S(0)) -> mu(+) mu(-) mu(+) mu(-)) < 5.1 x 10(-12) and B(K-L(0))-> mu(+) mu(-) mu(+) mu(-)) < 2.3 x 10(-9).
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Search for Higgs-like bosons decaying into long-lived exotic particles. Eur. Phys. J. C, 76(12), 664–15pp.
Abstract: A search is presented for massive long-lived particles, in the 20-60 GeV/c(2) mass range with lifetimes between 5 and 100 ps. The dataset used corresponds to 0.62 fb(-1) of proton-proton collision data collected by the LHCb detector at root s = 7 TeV. The particles are assumed to be pair-produced by the decay of a Higgs-like boson with mass between 80 and 140 GeV/c(2). No excess above the background expectation is observed and limits are set on the production cross-section as a function of the long-lived particle mass and lifetime and of the Higgs-like boson mass.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Search for Hidden-Sector Bosons in B-0 -> K*(0)mu(+)mu(-) Decays. Phys. Rev. Lett., 115(16), 161802–10pp.
Abstract: A search is presented for hidden-sector bosons, chi, produced in the decay B-0 -> K*(892)(0)chi, with K*(892)(0) -> K+pi(-) and chi -> mu(+)mu(-). The search is performed using pp-collision data corresponding to 3.0 fb(-1) collected with the LHCb detector. No significant signal is observed in the accessible mass range 214 <= m(chi) <= 4350 MeV, and upper limits are placed on the branching fraction product B(B-0 -> K*(892)(0)chi) X B(chi -> mu(+)mu(-)) as a function of the mass and lifetime of the chi boson. These limits are of the order of 10(-9) for chi lifetimes less than 100 ps over most of the m(chi) range, and place the most stringent constraints to date on many theories that predict the existence of additional low-mass bosons.
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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 heavy neutral leptons in W plus . μplus μ+/- jet decays. Eur. Phys. J. C, 81(3), 248–15pp.
Abstract: A search is performed for heavy neutrinos in the decay of a W boson into two muons and a jet. The data set corresponds to an integrated luminosity of approximately 3.0 fb-1 of proton-proton collision data at centre-of-mass energies of 7 and 8 TeV collected with the LHCb experiment. Both same-sign and opposite-signmuons in the final state are considered. Data are found to be consistent with the expected background. Upper limits on the coupling of a heavy neutrino with the Standard Model neutrino are set at 95% confidence level in the heavy-neutrino mass range from 5 to 50GeV/c2. These are of the order of 10(-3) for lepton-number-conserving decays and of the order of 10(-4) for lepton-number-violating heavy-neutrino decays.
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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). Search for excited B-c(+) states. J. High Energy Phys., 01(1), 138–18pp.
Abstract: A search is performed in the invariant mass spectrum of the B-c(+)pi(+) pi(-) system for the excited B-c(+) states B-c (2(1)S(0)) + and B-c(2(3)S(1)) + using a data sample of p p collisions collected by the LHCb experiment at the centre- of- mass energy of root s = 8TeV, corresponding to an integrated luminosity of 2 fb(-1). No evidence is seen for either state. Upper limits on the ratios of the production cross- sections of the Bc (2(1)S(0)) + and B-c(2(3)S(1)) + states times the branching fractions of Bc (2(1)S(0))(+) -> B-c(+)pi(+) pi(-) and B-c (2(3) S-1)(+) -> B-c*(+)pi(+) pi(-) over the production cross- section of the B-c(+) state are given as a function of their masses. They are found to be between 0.02 and 0.14 at 95% con fi dence level for B-c (2(1)S(0)) + and B-c (2(3)S(1)) + in the mass ranges [6830; 6890] MeV/c(2) and [6795; 6890] MeV/c(2), respectively.
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