In the Standard Model of particle physics, the strength of the couplings of the $b$ quark to the $u$ and $c$ quarks, $|V_{ub}|$ and $|V_{cb}|$, are governed by the coupling of the quarks to the Higgs boson. Using data from the LHCb experiment at the
Large Hadron Collider, the probability for the $Lambda^0_b$ baryon to decay into the $p mu^- overline{ u}_mu$ final state relative to the $Lambda^+_c mu^- overline{ u}_mu$ final state is measured. Combined with theoretical calculations of the strong interaction and a previously measured value of $|V_{cb}|$, the first $|V_{ub}|$ measurement to use a baryonic decay is performed. This measurement is consistent with previous determinations of $|V_{ub}|$ using $B$ meson decays to specific final states and confirms the existing incompatibility with those using an inclusive sample of final states.
We have constructed MOCASSIN photoionization plus dust radiative transfer models for the Crab Nebula core-collapse supernova (CCSN) remnant, using either smooth or clumped mass distributions, in order to determine the chemical composition and masses
of the nebular gas and dust. We computed models for several different geometries suggested for the nebular matter distribution but found that the observed gas and dust spectra are relatively insensitive to these geometries, being determined mainly by the spectrum of the pulsar wind nebula which ionizes and heats the nebula. Smooth distribution models are ruled out since they require 16-49 Msun of gas to fit the integrated optical nebular line fluxes, whereas our clumped models re quire 7.0 Msun of gas. A global gas-phase C/O ratio of 1.65 by number is derived, along with a He/H number ratio of 1.85, neither of which can be matched by current CCSN yield predictions. A carbonaceous dust composition is favoured by the observed gas-phase C/O ratio: amorphous carbon clumped model fits to the Crabs Herschel and Spitzer infrared spectral energy distribution imply the presence of 0.18-0.27 Msun of dust, corresponding to a gas to dust mass ratio of 26-39. Mixed dust chemistry models can also be accommodated, comprising 0.11-0.13 Msun of amorphous carbon and 0.39-0.47 Msun of silicates. Power-law grain size distributions with mass distributions that are weighted towards the largest grain radii are derived, favouring their longer-term survival when they eventually interact with the interstellar medium. The total mass of gas plus dust in the Crab Nebula is 7.2 +/- 0.5 Msun, consistent with a progenitor star mass of 9 Msun.
The angular distributions of the rare decays $B^+ to K^+mu^+mu^-$ and $B^0 to K^0_{rmscriptscriptstyle S}mu^+mu^-$ are studied with data corresponding to 3$~$fb$^{-1}$ of integrated luminosity, collected in proton-proton collisions at 7 and 8$~$TeV c
entre-of-mass energies with the LHCb detector. The angular distribution is described by two parameters, $F_{rm H}$ and the forward-backward asymmetry of the dimuon system $A_{rm FB}$, which are determined in bins of the dimuon mass squared. The parameter $F_{rm H}$ is a measure of the contribution from (pseudo)scalar and tensor amplitudes to the decay width. The measurements of $A_{rm FB}$ and $F_{rm H}$ reported here are the most precise to date and are compatible with predictions from the Standard Model.
The isospin asymmetries of $B to Kmu^+mu^-$ and $B to K^{*}mu^+mu^-$ decays and the partial branching fractions of the $B^0 to K^0mu^+mu^-$, $B^+ to K^+mu^+mu^-$ and $B^+ to K^{*+}mu^+mu^-$ 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, while individually consistent, all favour lower values than their respective Standard Model predictions.
A broad peaking structure is observed in the dimuon spectrum of $B^+ to K^+ mu^+mu^-$ decays in the kinematic region where the kaon has a low recoil against the dimuon system. The structure is consistent with interference between the $B^+ to K^+ mu^+
mu^-$ decay and a resonance and has a statistical significance exceeding six standard deviations. The mean and width of the resonance are measured to be $4191^{+9}_{-8}mathrm{,Mekern -0.1em V/}c^2$ and $65^{+22}_{-16}mathrm{,Mekern -0.1em V/}c^2$, respectively, where the uncertainties include statistical and systematic contributions. These measurements are compatible with the properties of the $psi(4160)$ meson. First observations of both the decay $B^+ to psi(4160) K^+$ and the subsequent decay $psi(4160) to mu^+mu^-$ are reported. The resonant decay and the interference contribution make up 20,% of the yield in the low recoil region, which is larger than theoretical estimates.
