Albert Puig Navarro

The production fractions of ${\overline{B}}_s^0$ and ${\mathrm{\Lambda }}_b^0$ hadrons, normalized to the sum of $B^{-}$ and ${\overline{B}}^0$ fractions, are measured in 13 TeV $pp$ collisions using data collected by the LHCb experiment, corresponding to an integrated luminosity of $1.67{\mathrm{fb}}^{-1}$. These ratios, averaged over the $b$ hadron transverse momenta from 4 to 25 GeV and pseudorapidity from 2 to 5, are $0.122\pm 0.006$ for ${\overline{B}}_s^0$, and $0.259\pm 0.018$ for ${\mathrm{\Lambda }}_b^0$, where the uncertainties arise from both statistical and systematic sources. The ${\mathrm{\Lambda }}_b^0$ ratio depends strongly on transverse momentum, while the ${\overline{B}}_s^0$ ratio shows a mild dependence. Neither ratio shows variations with pseudorapidity. The measurements are made using semileptonic decays to minimize theoretical uncertainties. In addition, the ratio of $D^{+}$ to $D^0$ mesons produced in the sum of ${\overline{B}}^0$ and $B^{-}$ semileptonic decays is determined as $0.359\pm 0.006\pm 0.009$, where the uncertainties are statistical and systematic.

A method is proposed to measure the photon polarisation parameter $$\lambda _{\gamma }$$ in $${{b}} \!\rightarrow {s} {\gamma } $$ transitions using an amp

The first untagged decay-time-integrated amplitude analysis of B _s ⁰ → K _S ⁰ K ^± π ^∓ decays is performed using a sample corresponding to 3.0 fb⁻¹ of pp collision data recorded with the LHCb detector during 2011 and 2012. The data are described with an amplitude model that contains contributions from the intermediate resonances K ^*(892)^0,+, K ₂ ^* (1430)^0,+ and K ₀ ^* (1430)^0,+, and their charge conjugates. Measurements of the branching fractions of the decay modes B _s ⁰ → K ^*(892)^± K ^∓ and $$ {B}_s^0\to \overset{\left(\hbox{---} \right)}{K^{*}}{(892)}^0\overset{\left(\hbox{---} \right)}{K^0} $$ B s 0 → K * — 892 0 K 0 — are in agreement with, and more precise than, previous results. The decays B _s ⁰ → K ₀ ^* (1430)^± K ^∓ and $$ {B}_s^0\to \overset{\left(\hbox{---} \right)}{K_0^{*}}{(1430)}^0\overset{\left(\hbox{---} \right)}{K^0} $$ B s 0 → K 0 * — 1430 0 K 0 — are observed for the first time, each with significance over 10 standard deviations.

We report a measurement of the mass difference between neutral charm-meson eigenstates using a novel approach that enhances sensitivity to this parameter. We use $2.3\times {10}^6$ $D^0\to K_{\mathit{S}}^0{\pi }^{+}{\pi }^{-}$ decays reconstructed in proton-proton collisions collected by the LHCb experiment in 2011 and 2012. Allowing for $CP$ violation in mixing and in the interference between mixing and decay, we measure the $CP$-averaged normalized mass difference $x_{CP}=[2.7\pm 1.6(\text{stat})\pm 0.4(\text{syst})]\times {10}^{-3}$ and the $CP$-violating parameter $\mathrm{\Delta }x=[-0.53\pm 0.70(\text{stat})\pm 0.22(\text{syst})]\times {10}^{-3}$. The results are consistent with $CP$ symmetry. These determinations are the most precise from a single experiment and, combined with current world-average results, yield the first evidence that the masses of the neutral charm-meson eigenstates differ.