6 research outputs found

    Measurement of the Ratio of Branching Fractions B (B ¯ 0 →d∗+τ- ν ¯ τ) / B (B ¯ 0 →d∗+μ- ν ¯ μ)

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    he branching fraction ratio R(D∗)≡B(B¯0→D∗+τ-ν¯τ)/B(B¯0→D∗+μ-ν¯μ) is measured using a sample of proton-proton collision data corresponding to 3.0fb-1 of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode τ-→μ-ν¯μντ. The semitauonic decay is sensitive to contributions from non-standard-model particles that preferentially couple to the third generation of fermions, in particular, Higgs-like charged scalars. A multidimensional fit to kinematic distributions of the candidate B¯0 decays gives R(D∗)=0.336±0.027(stat)±0.030(syst). This result, which is the first measurement of this quantity at a hadron collider, is 2.1 standard deviations larger than the value expected from lepton universality in the standard model

    Observation of J /ψp Resonances Consistent with Pentaquark States in Λb0 →j /ψK-p Decays

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    Observations of exotic structures in the J/ψp channel, which we refer to as charmonium-pentaquark states, in Λb0→J/ψK-p decays are presented. The data sample corresponds to an integrated luminosity of 3fb-1 acquired with the LHCb detector from 7 and 8 TeV pp collisions. An amplitude analysis of the three-body final state reproduces the two-body mass and angular distributions. To obtain a satisfactory fit of the structures seen in the J/ψp mass spectrum, it is necessary to include two Breit-Wigner amplitudes that each describe a resonant state. The significance of each of these resonances is more than 9 standard deviations. One has a mass of 4380±8±29MeV and a width of 205±18±86MeV, while the second is narrower, with a mass of 4449.8±1.7±2.5MeV and a width of 39±5±19MeV. The preferred JP assignments are of opposite parity, with one state having spin 3/2 and the other 5/2

    Measurement of matter–antimatter differences in beauty baryon decays

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    Differences in the behaviour of matter and antimatter have been observed in K and B meson decays, but not yet in any baryon decay. Such differences are associated with the non-invariance of fundamental interactions under the combined charge-conjugation and parity transformations, known as CP violation. Here, using data from the LHCb experiment at the Large Hadron Collider, we search for CP-violating asymmetries in the decay angle distributions of Lambda(0)(b) baryons decaying to p pi(-) pi(+) pi(-) and p pi(-) K+K- final states. These four-body hadronic decays are a promising place to search for sources of CP violation both within and beyond the standard model of particle physics. We find evidence for CP violation in Lambda(0)(b) to p pi(-) pi(+) pi(-) decays with a statistical significance corresponding to 3.3 standard deviations including systematic uncertainties. This represents the first evidence for CP violation in the baryon sector

    Elective Cancer Surgery in COVID-19–Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study

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