BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2020). Search for a Dark Leptophilic Scalar in e(+) e(-) Collisions. Phys. Rev. Lett., 125(18), 181801–8pp.
Abstract: Many scenarios of physics beyond the standard model predict the existence of new gauge singlets, which might be substantially lighter than the weak scale. The experimental constraints on additional scalars with masses in the MeV to GeV range could be significantly weakened if they interact predominantly with leptons rather than quarks. At an e(+) e(-) collider, such a leptophilic scalar (phi(L)) would be produced predominantly through radiation from a tau lepton. We report herein a search for e(+) e(- )-> tau(+) tau(-)phi(L), phi(L)-> l(+) l(-) (l = e, mu) using data collected by the BABAR experiment at SLAC. No significant signal is observed, and we set limits on the phi(L) coupling to leptons in the range 0.04 < m phi(L) < 7.0 GeV. These bounds significantly improve upon the current constraints, excluding almost entirely the parameter space favored by the observed discrepancy in the muon anomalous magnetic moment below 4 GeV at 90% confidence level.
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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). Observation of Enhanced Double Parton Scattering in Proton-Lead Collisions at root s(NN)=8.16 TeV. Phys. Rev. Lett., 125(21), 212001–13pp.
Abstract: A study of prompt charm-hadron pair production in proton-lead collisions at root s(NN) = 8.16 TeV is performed using data corresponding to an integrated luminosity of about 30 nb(-1), collected with the LHCb experiment. Production cross sections for different pairs of charm hadrons are measured and kinematic correlations between the two charm hadrons are investigated. This is the first measurement of associated production of two charm hadrons in proton-lead collisions. The results confirm the predicted enhancement of double parton scattering production in proton-lead collisions compared to the single parton scattering production.
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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). 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.
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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). 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).
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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.
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