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 $5/2$.

In response to the 2013 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) study was launched, as an international collaboration hosted by CERN. This study...

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 narrow pentaquark state, $P_c(4312{)}^{+}$, decaying to $J/\psi p$, is discovered with a statistical significance of $7.3\sigma$ in a data sample of ${\mathrm{\Lambda }}_b^0\to J/\psi p{K}^{-}$ decays, which is an order of magnitude larger than that previously analyzed by the LHCb Collaboration. The $P_c(4450{)}^{+}$ pentaquark structure formerly reported by LHCb is confirmed and observed to consist of two narrow overlapping peaks, $P_c(4440{)}^{+}$ and $P_c(4457{)}^{+}$, where the statistical significance of this two-peak interpretation is $5.4\sigma$. The proximity of the ${\mathrm{\Sigma }}_c^{+}{\overline{D}}^0$ and ${\mathrm{\Sigma }}_c^{+}{\overline{D}}^{*0}$ thresholds to the observed narrow peaks suggests that they play an important role in the dynamics of these states.

In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by...