BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2020). Precision Measurement of the Ratio B(gamma(3S) -> tau(+)tau(-))/B(gamma(3S) -> mu(+)mu(-)). Phys. Rev. Lett., 125(24), 241801–7pp.
Abstract: We report on a precision measurement of the ratio R-tau mu(gamma(3s)) = B(gamma(3S) -> tau(+)tau(-))/B(tau(gamma(3S) ->mu(+)mu(-)) using data collected with the BABAR detector at the SLAC PEP-II e(+)e(-) collider. The measurement is based on a 28 fb(-1) data sample collected at a center-of-mass energy of 10.355 GeV corresponding to a sample of 122 million gamma(35) mesons. The ratio is measured to be R-tau mu(gamma(3s)) = 0.966 +/- 0.008(stat) +/- 0.014(syst) and is in agreement with the standard model prediction of 0.9948 within 2 standard deviations. The uncertainty in R-tau mu(gamma(3s)) is almost an order of magnitude smaller than the only previous measurement.
|
LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2020). Model-Independent Study of Structure in B+ -> D+D-K+ Decays. Phys. Rev. Lett., 125(24), 242001–10pp.
Abstract: The only anticipated resonant contributions to B+ -> D+D-K+ decays are charmonium states in the D+D- channel. A model-independent analysis, using LHCb proton-proton collision data taken at centerof-mass energies of root s = 7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb(-1), is carried out to test this hypothesis. The description of the data assuming that resonances only manifest in decays to the D+D- pair is shown to be incomplete. This constitutes evidence for a new contribution to the decay, potentially one or more new charm-strange resonances in the D-K+ channel with masses around 2.9 GeV/c(2).
|
LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2020). Constraints on the K-S(0) -> mu(+) mu(-) Branching Fraction. Phys. Rev. Lett., 125(23), 231801–10pp.
Abstract: A search for the decay K-S(0) -> mu(+) mu(-) is performed using proton-proton collision data, corresponding to an integrated luminosity of 5.6 fb(-1) and collected with the LHCb experiment during 2016, 2017, and 2018 at a center-of-mass energy of 13 TeV. The observed signal yield is consistent with zero, yielding an upper limit of B(K-S(0) -> mu(+) mu(-)) < 2.2 x 10(-10) at 90% C.L.. The limit reduces to B(K-S(0) -> mu(+) mu(-)) < 2.1 x 10(-10) at 90% C.L. once combined with the result from data taken in 2011 and 2012.
|
ATLAS Collaboration(Aad, G. et al), Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Castillo, F. L., Castillo Gimenez, V., et al. (2020). Search for Higgs Boson Decays into a Z Boson and a Light Hadronically Decaying Resonance Using 13 TeV pp Collision Data from the ATLAS Detector. Phys. Rev. Lett., 125(22), 221802–22pp.
Abstract: A search for Higgs boson decays into a Z boson and a light resonance in two-lepton plus jet events is performed, using a pp collision dataset with an integrated luminosity of 139 fb(-1) collected at root s = 13 TeV by the ATLAS experiment at the CERN LHC. The resonance considered is a light boson with a mass below 4 GeV from a possible extended scalar sector or a charmonium state. Multivariate discriminants are used for the event selection and for evaluating the mass of the light resonance. No excess of events above the expected background is found. Observed (expected) 95% confidence-level upper limits are set on the Riggs boson production cross section times branching fraction to a Z boson and the signal resonance, with values in the range 17-340 pb (16(-5)(+6)-320(-90)(+130) pb) for the different light spin-0 boson mass and branching fraction hypotheses, and with values of 110 and 100 pb (100(-30)(+40) and 100(-30)(+40) pb) for the eta(c) and J/psi hypotheses, respectively.
|
Caputo, A., Liu, H. W., Mishra-Sharma, S., & Ruderman, J. T. (2020). Dark Photon Oscillations in Our Inhomogeneous Universe. Phys. Rev. Lett., 125(22), 221303–8pp.
Abstract: A dark photon kinetically mixing with the ordinary photon represents one of the simplest viable extensions to the standard model, and would induce oscillations with observable imprints on cosmology. Oscillations are resonantly enhanced if the dark photon mass equals the ordinary photon plasma mass, which tracks the free electron number density. Previous studies have assumed a homogeneous Universe; in this Letter, we introduce for the first time an analytic formalism for treating resonant oscillations in the presence of inhomogeneities of the photon plasma mass. We apply our formalism to determine constraints from cosmic microwave background photons oscillating into dark photons, and from heating of the primordial plasma due to dark photon dark matter converting into low-energy photons. Including the effect of inhomogeneities demonstrates that prior homogeneous constraints are not conservative, and simultaneously extends current experimental limits into a vast new parameter space.
|
