A test of lepton universality, performed by measuring the ratio of the branching fractions of the B ⁰ → K ^*0 μ ⁺ μ ⁻ and B ⁰ → K ^*0 e ⁺ e ⁻ decays, \( {R}_{K^{*0}} \), is presented. The K ^*0 meson is reconstructed in the final state K ⁺ π ⁻, which is required to have an invariant mass within 100 MeV/c ² of the known K ^*(892)⁰ mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of about 3 fb⁻¹, collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The ratio is measured in two regions of the dilepton invariant mass squared, q ², to be $$ {R}_{K^{*0}}=\left\{\begin{array}{l}{0.66_{-}^{+}}_{0.07}^{0.11}\left(\mathrm{stat}\right)\pm 0.03\left(\mathrm{syst}\right)\kern1em \mathrm{f}\mathrm{o}\mathrm{r}\kern1em 0.045<{q}^2<1.1\kern0.5em {\mathrm{GeV}}^2/{c}^4,\hfill \\ {}{0.69_{-}^{+}}_{0.07}^{0.11}\left(\mathrm{stat}\right)\pm 0.05\left(\mathrm{syst}\right)\kern1em \mathrm{f}\mathrm{o}\mathrm{r}\kern1em 1.1<{q}^2<6.0\kern0.5em {\mathrm{GeV}}^2/{c}^4.\hfill \end{array}\right. $$ The corresponding 95.4% confidence level intervals are [0.52, 0.89] and [0.53, 0.94]. The results, which represent the most precise measurements of \( {R}_{K^{*0}} \) to date, are compatible with the Standard Model expectations at the level of 2.1–2.3 and 2.4–2.5 standard deviations in the two q ² regions, respectively. Open image in new window

A highly significant structure is observed in the ${\mathrm{\Lambda }}_c^{+}{K}^{-}{\pi }^{+}{\pi }^{+}$ mass spectrum, where the ${\mathrm{\Lambda }}_c^{+}$ baryon is reconstructed in the decay mode $p{K}^{-}{\pi }^{+}$. The structure is consistent with originating from a weakly decaying particle, identified as the doubly charmed baryon ${\mathrm{\Xi }}_{cc}^{++}$. The difference between the masses of the ${\mathrm{\Xi }}_{cc}^{++}$ and ${\mathrm{\Lambda }}_c^{+}$ states is measured to be $1334.94\pm 0.72(\text{stat.})\pm 0.27(\text{syst}\mathrm{.})\mathrm{MeV}/c^2$, and the ${\mathrm{\Xi }}_{cc}^{++}$ mass is then determined to be $3621.40\pm 0.72(\text{stat.})\pm 0.27(\text{syst}\mathrm{.})\pm 0.14({\mathrm{\Lambda }}_c^{+})\mathrm{MeV}/c^2$, where the last uncertainty is due to the limited knowledge of the ${\mathrm{\Lambda }}_c^{+}$ mass. The state is observed in a sample of proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $1.7{\mathrm{fb}}^{-1}$, and confirmed in an additional sample of data collected at 8 TeV.

Combined measurements of Higgs boson production cross sections and branching fractions are presented. The combination is based on the analyses of the Higgs boson decay modes $H\to \gamma \gamma$, $Z{Z}^{*}$, $W{W}^{*}$, $\tau \tau$, $b\overline{b}$, $\mu \mu$, searches for decays into invisible final states, and on measurements of off-shell Higgs boson production. Up to $79.8{\mathrm{fb}}^{-1}$ of proton–proton collision data collected at $\sqrt{s}=13\mathrm{TeV}$ with the ATLAS detector are used. Results are presented for the gluon–gluon fusion and vector-boson fusion processes, and for associated production with vector bosons or top-quarks. The global signal strength is determined to be $\mu =1.11_{-0.08}^{+0.09}$. The combined measurement yields an observed (expected) significance for the vector-boson fusion production process of $6.5\sigma$ ($5.3\sigma$). Measurements in kinematic regions defined within the simplified template cross section framework are also shown. The results are interpreted in terms of modifiers applied to the Standard Model couplings of the Higgs boson to other particles, and are used to set exclusion limits on parameters in two-Higgs-doublet models and in the simplified minimal supersymmetric Standard Model. No significant deviations from Standard Model predictions are observed.