Observations of exotic structures in the $J/\psi p$ channel, which we refer to as charmonium-pentaquark states, in ${\mathrm{\Lambda }}_b^0\to J/\psi K^{-}p$ decays are presented. The data sample corresponds to an integrated luminosity of $3{\mathrm{fb}}^{-1}$ 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 $J/\psi p$ 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 $4380\pm 8\pm 29\mathrm{MeV}$ and a width of $205\pm 18\pm 86\mathrm{MeV}$, while the second is narrower, with a mass of $4449.8\pm 1.7\pm 2.5\mathrm{MeV}$ and a width of $39\pm 5\pm 19\mathrm{MeV}$. The preferred $J^P$ assignments are of opposite parity, with one state having spin $3/2$ and the other $5/2$.

A measurement of the ratio of the branching fractions of the $B^{+}\to K^{+}{\mu }^{+}{\mu }^{-}$ and $B^{+}\to K^{+}{e}^{+}{e}^{-}$ decays is presented using proton-proton collision data, corresponding to an integrated luminosity of $3.0{\mathrm{fb}}^{-1}$, recorded with the LHCb experiment at center-of-mass energies of 7 and 8 TeV. The value of the ratio of branching fractions for the dilepton invariant mass squared range $1<q^2<6{\mathrm{GeV}}^2/c^4$ is measured to be $0.745_{-0.074}^{+0.090}(\text{stat})\pm 0.036(\text{syst})$. This value is the most precise measurement of the ratio of branching fractions to date and is compatible with the standard model prediction within 2.6 standard deviations.

The isospin asymmetries of B → Kμ ⁺ μ ⁻ and B → K ^* μ ⁺ μ ⁻ decays and the partial branching fractions of the B ⁰ → K ⁰ μ ⁺ μ ⁻, B ⁺ → K ⁺ μ ⁺ μ ⁻ and B ⁺ → K ^*+ μ ⁺ μ ⁻ decays are measured as functions of the dimuon mass squared, q ². The data used correspond to an integrated luminosity of 3 fb⁻¹ from proton-proton collisions collected with the LHCb detector at centre-of-mass energies of 7 TeV and 8 TeV in 2011 and 2012, respectively. The isospin asymmetries are both consistent with the Standard Model expectations. The three measured branching fractions favour lower values than their respective theoretical predictions, however they are all individually consistent with the Standard Model. Open image in new window

We present a measurement of form-factor-independent angular observables in the decay $B^0\to K^{*}(892{)}^0{\mu }^{+}{\mu }^{-}$. The analysis is based on a data sample corresponding to an integrated luminosity of $1.0{\mathrm{fb}}^{-1}$, collected by the LHCb experiment in $pp$ collisions at a center-of-mass energy of 7 TeV. Four observables are measured in six bins of the dimuon invariant mass squared $q^2$ in the range $0.1<q^2<19.0{\mathrm{GeV}}^2/c^4$. Agreement with recent theoretical predictions of the standard model is found for 23 of the 24 measurements. A local discrepancy, corresponding to 3.7 Gaussian standard deviations is observed in one $q^2$ bin for one of the observables. Considering the 24 measurements as independent, the probability to observe such a discrepancy, or larger, in one is 0.5%.

We have observed a narrow state near $2.32\mathrm{G}\mathrm{e}\mathrm{V}/c^2$ in the inclusive $D_s^{+}{\pi }^0$ invariant mass distribution from $e^{+}{e}^{-}$ annihilation data at energies near 10.6 GeV. The observed width is consistent with the experimental resolution. The small intrinsic width and the quantum numbers of the final state indicate that the decay violates isospin conservation. The state has natural spin-parity and the low mass suggests a $J^P=0^{+}$ assignment. The data sample corresponds to an integrated luminosity of $91{\mathrm{f}\mathrm{b}}^{-1}$ recorded by the BABAR detector at the SLAC PEP-II asymmetric-energy $e^{+}{e}^{-}$ storage ring.