LHCb

Abstract:

A measurement of the shape of the differential decay rate and the associated Isgur-Wise function for the decay Λ0b→Λ+cμ−¯νμ is reported, using data corresponding to 3  fb^−1 collected with the LHCb detector in proton-proton collisions. The Λ+cμ−¯νμ(+anything) final states are reconstructed through the detection of a muon and a Λ+c baryon decaying into pK−π+, and the decays Λ0b→Λ+cπ+π−μ−νμ¯ are used to determine contributions from Λ0b→Λ*+cμ−ν¯ μ decays. The measured dependence of the differential decay rate upon the squared four-momentum transfer between the heavy baryons, q2, is compared with expectations from heavy-quark effective theory and from unquenched lattice QCD predictions.

Abstract:

© 2017 CERN, for the LHCb Collaboration. The decays χc1→J/ψμ+μ- and χc2→J/ψμ+μ- are observed and used to study the resonance parameters of the χc1 and χc2 mesons. The masses of these states are measured to be m(χc1)=3510.71±0.04(stat)±0.09(syst) MeV and m(χc2)=3556.10±0.06(stat)±0.11(syst) MeV, where the knowledge of the momentum scale for charged particles dominates the systematic uncertainty. The momentum-scale uncertainties largely cancel in the mass difference m(χc2)-m(χc1)=45.39±0.07(stat)±0.03(syst) MeV. The natural width of the χc2 meson is measured to be Γ(χc2)=2.10±0.20(stat)±0.02(syst) MeV. These results are in good agreement with and have comparable precision to the current world averages.

Abstract:

A measurement is presented of decay-time-dependent CP violation in the decays B 0 → J/ψ K S 0 and B 0 → ψ(2S)K S 0 , where the J/ψ is reconstructed from two electrons and the ψ(2S) from two muons. The analysis uses a sample of pp collision data recorded with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb −1 . The CP -violation observables are measured to beC(B0→J/ψKS0)=0.12±0.07±0.02,S(B0→J/ψKS0)=0.83±0.08±0.01,C(B0→ψ(2S)KS0)=−0.05±0.10±0.01,S(B0→ψ(2S)KS0)=0.84±0.10±0.01,where C describes CP violation in the direct decay, and S describes CP violation in the interference between the amplitudes for the direct decay and for the decay after B 0 − B¯ 0 oscillation. The first uncertainties are statistical and the second are systematic. The two sets of results are compatible with the previous LHCb measurement using B 0 → J/ψ K S 0 decays, where the J/ψ meson was reconstructed from two muons. The averages of all three sets of LHCb results areC(B0→[cc¯]KS0)=−0.017±0.029,S(B0→[cc¯] KS0)=0.760±0.034,under the assumption that higher-order contributions to the decay amplitudes are negligible. The uncertainties include statistical and systematic contributions.[Figure not available: see fulltext.].

Abstract:

Measurements of CP observables in B± → DK*± decays are presented, where D denotes a superposition of D0 and D0 meson states. Decays of the D meson to K- Π+, K-K+, Π-Π+, K- Π+ Π- Π+ and Π- Π+ Π- Π+ are used and the K*± meson is reconstructed in the K0 S± Π final state. This analysis uses a data sample of pp collisions collected with the LHCb experiment, corresponding to integrated luminosities of 1 fb-1, 2 fb-1 and 1.8 fb-1 at centre-of-mass energies p s = 7TeV, 8TeV and 13TeV, respectively. The sensitivity of the results to the CKM angle is discussed.