LHCb

Abstract:

A bstract The first search for the rare radiative decay $$ {\Xi}_b^{-} $$ Ξ b − → Ξ − γ is performed using data collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb − 1 . The $$ {\Xi}_b^{-} $$ Ξ b − → Ξ − J/ψ channel is used as normalization. No $$ {\Xi}_b^{-} $$ Ξ b − → Ξ − γ signal is found and an upper limit of $$ \mathcal{B} $$ B ( $$ {\Xi}_b^{-} $$ Ξ b − → Ξ − γ ) < 1 . 3 × 10 − 4 at 95% confidence level is obtained.

Abstract:

A bstract Using proton-proton collision data, corresponding to an integrated luminosity of 9 fb − 1 collected with the LHCb detector, seven decay modes of the $$ {\mathrm{B}}_{\mathrm{c}}^{+} $$ Bc+ meson into a J / ψ or ψ(2S) meson and three charged hadrons, kaons or pions, are studied. The decays $$ {\mathrm{B}}_{\mathrm{c}}^{+} $$ Bc+ → (ψ(2S) → J / ψπ + π − )π + , $$ {\mathrm{B}}_{\mathrm{c}}^{+} $$ Bc+ → ψ(2S)π + π − π + , $$ {\mathrm{B}}_{\mathrm{c}}^{+} $$ Bc+ → J / ψK + π − π + and $$ {\mathrm{B}}_{\mathrm{c}}^{+} $$ Bc+ → J / ψK + K − K + are observed for the first time, and evidence for the $$ {\mathrm{B}}_{\mathrm{c}}^{+} $$ Bc+ → ψ(2S)K + K − π + , decay is found, where J / ψ and ψ(2S) mesons are reconstructed in their dimuon decay modes. The ratios of branching fractions between the different $$ {\mathrm{B}}_{\mathrm{c}}^{+} $$ Bc+ decays are reported as well as the fractions of the decays proceeding via intermediate resonances. The results largely support the factorisation approach used for a theoretical description of the studied decays.

Abstract:

A bstract The W boson mass is measured using proton-proton collision data at $$ \sqrt{s} $$ s = 13 TeV corresponding to an integrated luminosity of 1.7 fb − 1 recorded during 2016 by the LHCb experiment. With a simultaneous fit of the muon q/p T distribution of a sample of W → μν decays and the ϕ * distribution of a sample of Z → μμ decays the W boson mass is determined to be $$ {m}_w=80354\pm {23}_{\mathrm{stat}}\pm {10}_{\mathrm{exp}}\pm {17}_{\mathrm{theory}}\pm {9}_{\mathrm{PDF}}\mathrm{MeV}, $$ mw=80354±23stat±10exp±17theory±9PDFMeV, where uncertainties correspond to contributions from statistical, experimental systematic, theoretical and parton distribution function sources. This is an average of results based on three recent global parton distribution function sets. The measurement agrees well with the prediction of the global electroweak fit and with previous measurements.