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Cirigliano, V., Falkowski, A., Gonzalez-Alonso, M., & Rodriguez-Sanchez, A. (2019). Hadronic tau Decays as New Physics Probes in the LHC Era. Phys. Rev. Lett., 122(22), 221801–7pp.
Abstract: We analyze the sensitivity of hadronic tau decays to nonstandard interactions within the model-independent framework of the standard model effective field theory. Both exclusive and inclusive decays are studied, using the latest lattice data and QCD dispersion relations. We show that there are enough theoretically clean channels to disentangle all the effective couplings contributing to these decays, with the tau -> pi pi nu(tau) channel representing an unexpected powerful new physics probe. We find that the ratios of nonstandard couplings to the Fermi constant are bound at the subpercent level. These bounds are complementary to the ones from electroweak precision observables and pp -> tau nu(tau) measurements at the LHC. The combination of tau decay and LHC data puts tighter constraints on lepton universality violation in the gauge boson-lepton vertex corrections.
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Celis, A., Cirigliano, V., & Passemar, E. (2014). Model-discriminating power of lepton flavor violating tau decays. Phys. Rev. D, 89(9), 095014–14pp.
Abstract: Within an effective field theory framework, we discuss the possibility to discriminate among different operators that contribute to lepton flavor violating (LFV) tau decays. Correlations among decay rates in different channels are shown to provide a basic handle to unravel the origin of LFV in these processes. More information about the underlying dynamics responsible for LFV can be gathered from differential distributions in three-body decays like tau -> μpi pi or tau -> 3 mu: these are considered in some detail. We incorporate in our analysis recent developments in the determination of the hadronic form factors for tau -> μpi pi. Future prospects for the observation of LFV tau decays and its interpretation are also discussed.
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Bhattacharya, T., Cirigliano, V., Cohen, S. D., Filipuzzi, A., Gonzalez-Alonso, M., Graesser, M. L., et al. (2012). Probing novel scalar and tensor interactions from (ultra)cold neutrons to the LHC. Phys. Rev. D, 85(5), 054512–29pp.
Abstract: Scalar and tensor interactions were once competitors to the now well-established V – A structure of the standard model weak interactions. We revisit these interactions and survey constraints from low-energy probes (neutron, nuclear, and pion decays) as well as collider searches. Currently, the most stringent limit on scalar and tensor interactions arise from 0(+) -> 0(+) nuclear decays and the radiative pion decay pi -> e nu gamma, respectively. For the future, we find that upcoming neutron beta decay and LHC measurements will compete in setting the most stringent bounds. For neutron beta decay, we demonstrate the importance of lattice computations of the neutron-to-proton matrix elements to setting limits on these interactions, and provide the first lattice estimate of the scalar charge and a new average of existing results for the tensor charge. Data taken at the LHC is currently probing these interactions at the 10(-2) level (relative to the standard weak interactions), with the potential to reach the less than or similar to 10(-3) level. We show that, with some theoretical assumptions, the discovery of a charged spin-0 resonance decaying to an electron and missing energy implies a lower limit on the strength of scalar interactions probed at low energy.
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Celis, A., Cirigliano, V., & Passemar, E. (2014). Lepton flavor violation in the Higgs sector and the role of hadronic tau-lepton decays. Phys. Rev. D, 89(1), 013008–19pp.
Abstract: It has been pointed out recently that current low-energy constraints still allow for sizable flavor-changing decay rates of the 125 GeV boson into leptons, h -> tau l (l = e, mu). In this work we discuss the role of hadronic tau-lepton decays in probing lepton flavor violating couplings in the Higgs sector. At low energy, the effective Higgs coupling to gluons induced by heavy quarks contributes to hadronic tau decays, establishing a direct connection with the relevant process at the LHC, pp(gg) -> h -> tau l. Semileptonic transitions like tau -> l pi pi are sensitive to flavor-changing scalar couplings, while decays such as tau -> l eta((l)) probe pseudoscalar couplings, thus providing a useful low-energy handle to disentangle possible Higgs flavor violating signals at the LHC. As part of our analysis, we provide an appropriate description of all the relevant hadronic matrix elements needed to describe Higgs mediated tau -> pi pi transitions, improving over previous treatments in the literature.
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Antonelli, M., Cirigliano, V., Isidori, G., Mescia, F., Moulson, M., Neufeld, H., et al. (2010). An evaluation of |Vus| and precise tests of the Standard Model from world data on leptonic and semileptonic kaon decays. Eur. Phys. J. C, 69(3-4), 399–424.
Abstract: We present a global analysis of leptonic and semileptonic kaon decay data, including all recent results published by the BNL-E865, KLOE, KTeV, ISTRA+ and NA48 experiments. This analysis, in conjunction with precise lattice calculations of the hadronic matrix elements now available, leads to a very precise determination of broken vertical bar V-us broken vertical bar and allows us to perform several stringent tests of the Standard Model.
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