[en] The ${\Lambda }_b^0\to {\Lambda }_c^{+}{K}^{+}{K}^{-}{\pi }^{-}$ decay is observed for the first time using a data sample of proton-proton collisions at centre-of-mass energies of $\sqrt{s}=7$ and $8\text{TeV}$ collected by the LHCb detector, corresponding to an integrated luminosity of $3\mathrm{f}{\mathrm{b}}^{-\mathrm{1}}$. The ratio of branching fractions between the ${\Lambda }_b^0\to {\Lambda }_c^{+}{K}^{+}{K}^{-}{\pi }^{-}$ and the ${\Lambda }_b^0\to {\Lambda }_c^{+}{D}_s^{-}$ decays is measured to be$\frac{\mathcal{B}({\Lambda }_b^0\to {\Lambda }_c^{+}{K}^{+}{K}^{-}{\pi }^{-})}{\mathcal{B}({\Lambda }_b^0\to {\Lambda }_c^{+}{D}_s^{-})}=(9.26\pm 0.29\pm 0.46\pm 0.26)\times {10}^{-2},$ where the first uncertainty is statistical, the second systematic and the third is due to the knowledge of the $D_s^{-}\to K^{+}{K}^{-}{\pi }^{-}$ branching fraction. No structure on the invariant mass distribution of the ${\Lambda }_c^{+}{K}^{+}$ system is found, consistent with no open-charm pentaquark signature.

[en] Using a data sample corresponding to an integrated luminosity of 2.0 fb${}^{\text{â<!-- ?? -->}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}1}$, collected by the LHCb experiment, the production of the η${}_c$(1S) state in proton–proton collisions at a centre-of-mass energy of $\sqrt{s}$=13 TeV is studied in the rapidity range 2.0T<14.0 GeV. The cross-section for prompt production of η${}_c$(1S) mesons relative to that of the J/ψ meson is measured using the p$\stackrel{¯<!--\; ??\; -->}{p}$ decay mode and is found to be σ${}_{{\mathrm{\eta <!--\; ??\; -->}}_c(1S)}$/σ${}_{J/\mathrm{\psi <!--\; ??\; -->}}$=1.69±0.15±0.10±0.18. The quoted uncertainties are, in order, statistical, systematic and due to uncertainties on the branching fractions of the J/ψ→p$\stackrel{¯<!--\; ??\; -->}{p}$ and η${}_c$→p$\stackrel{¯<!--\; ??\; -->}{p}$ decays. The prompt η${}_c$(1S) production cross-section is determined to be σ${}_{{\mathrm{\eta <!--\; ??\; -->}}_c(1S)}$=1.26±0.11±0.08±0.14μb, where the last uncertainty includes that on the J/ψ meson cross-section. The ratio of the branching fractions of b-hadron decays to the η${}_c$(1S) and J/ψ states is measured to be B${}_{b\text{â<!-- ?? -->}\text{†<!-- ??? -->}\text{’<!-- ??? -->}{\mathrm{\eta <!--\; ??\; -->}}_{c}X}$/B${}_{b\text{â<!-- ?? -->}\text{†<!-- ??? -->}\text{’<!-- ??? -->}J/\mathrm{\psi <!--\; ??\; -->}X}$=0.48±0.03±0.03±0.05, where the last uncertainty is due to those on the branching fractions of the J/ψ→p$\stackrel{¯<!--\; ??\; -->}{p}$ and η${}_c$→p$\stackrel{¯<!--\; ??\; -->}{p}$ decays. The difference between the J/ψ and η${}_c$(1S) masses is also determined to be 113.0±0.7±0.1 MeV, which is the most precise single measurement of this quantity to date.

[en] A branching fraction measurement of the B${}^0$ → D${}_s^{+}$π${}^{-<!--\; ???\; -->}$ decay is presented using proton-proton collision data collected with the LHCb experiment, corresponding to an integrated luminosity of 5.0 fb${}^{-<!--\; ???\; -->1}$. The branching fraction is found to be B(B${}^0$ → D${}_s^{+}$π${}^{-<!--\; ???\; -->}$) = (19.4 ± 1.8 ± 1.3 ± 1.2) × 10${}^{-<!--\; ???\; -->6}$, where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the B${}^0$ → D${}^{-<!--\; ???\; -->}$π${}^{+}$, D${}_s^{+}$ → K${}^{+}$K${}^{-<!--\; ???\; -->}$π${}^{+}$ and D${}^{-<!--\; ???\; -->}$ → K${}^{+}$π${}^{-<!--\; ???\; -->}$π${}^{-<!--\; ???\; -->}$ branching fractions. This is the most precise single measurement of this quantity to date. As this decay proceeds through a single amplitude involving a b → u charged-current transition, the result provides information on non-factorisable strong interaction effects and the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element V${}_{ub}$. Additionally, the collision energy dependence of the hadronisation-fraction ratio $f_s$/$f_d$ is measured through ${\stackrel{¯<!--\; ??\; -->}{B}}_s^0$ → D${}_s^{+}$π${}^{-<!--\; ???\; -->}$ and B${}^0$ → D${}^{-<!--\; ???\; -->}$π${}^{+}$ decays.

[en] Long-lived particles decaying to $e^{\pm <!--\; ??\; -->}$µ${}^{\mp <!--\; ???\; -->}$ν, with masses between 7 and 50 GeV/c${}^2$ and lifetimes between 2 and 50 ps, are searched for by looking at displaced vertices containing electrons and muons of opposite charges. The search is performed using 5.4 fb${}^{-<!--\; ???\; -->1}$ of p p collisions collected with the LHCb detector at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV. Three mechanisms of production of long-lived particles are considered: the direct pair production from quark interactions, the pair production from the decay of a Standard-Model-like Higgs boson with a mass of 125 GeV/c${}^2$, and the charged current production from an on-shell W boson with an additional lepton. No evidence of these long-lived states is obtained and upper limits on the production cross-section times branching fraction are set on the different production modes.

[en] A first search for CP violation in the Cabibbo-suppressed Ξ${}_c^{+}$→pK${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}$π${}^{+}$ decay is performed using both a binned and an unbinned model-independent technique in the Dalitz plot. The studies are based on a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb${}^{\text{â<!-- ?? -->}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}1}$, and collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The data are consistent with the hypothesis of no CP violation.

[en] The decay-time-dependent CP asymmetry in B${}_s^0$→J/ψK${}^{+}$K${}^{-<!--\; ???\; -->}$ decays is measured using proton–proton collision data, corresponding to an integrated luminosity of 1.9fb${}^{\text{â<!-- ?? -->}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}1}$, collected with the LHCb detector at a centre-of-mass energy of 13TeV in 2015 and 2016. Using a sample of approximately 117 000 signal decays with an invariant K${}^{+}$K${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}$ mass in the vicinity of the ϕ(1020) resonance, the CP-violating phase ϕ${}_s$ is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the B${}_s^0$-$\stackrel{¯<!--\; ??\; -->}{B}$${}_s^0$ system, ΔΓ${}_s$. The difference of the average B${}_s^0$ and B${}^0$ meson decay widths, Γ${}_s$−Γ${}_d$, is determined using in addition a sample of B${}^0$→J/ψK${}^{+}$π${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}$ decays. The values obtained are ϕ${}_s$=−0.083±0.041±0.006rad, ΔΓ${}_s$=0.077±0.008±0.003ps−1 and Γ${}_s$−Γ${}_d$=−0.0041±0.0024±0.0015ps${}^{-<!--\; ???\; -->1}$, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements of these quantities to date and are consistent with expectations based on the Standard Model and with a previous LHCb analysis of this decay using data recorded at centre-of-mass energies 7 and 8 TeV. Finally, the results are combined with recent results from B${}_s^0$→J/ψπ${}^{+}$π${}^{-<!--\; ???\; -->}$ decays obtained using the same dataset as this analysis, and with previous independent LHCb results.

[en] A search is performed for heavy neutrinos in the decay of a W boson into two muons and a jet. The data set corresponds to an integrated luminosity of approximately 3.0 fb${}^{-<!--\; ???\; -->1}$ of proton-proton collision data at centre-of-mass energies of 7 and 8 TeV collected with the LHCb experiment. Both same-sign and opposite-sign muons in the final state are considered. Data are found to be consistent with the expected background. Upper limits on the coupling of a heavy neutrino with the Standard Model neutrino are set at 95 % confidence level in the heavy-neutrino mass range from 5 to 50 GeV/c${}^2$. These are of the order of 10${}^{-<!--\; ???\; -->3}$ for lepton-number-conserving decays and of the order of 10${}^{-<!--\; ???\; -->4}$ for lepton-number-violating heavy-neutrino decays.

[en] A structure is observed in the B${}^{\pm <!--\; ??\; -->}$K${}^{\mp <!--\; ???\; -->}$ mass spectrum in a sample of proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a total integrated luminosity of 9 fb${}^{-<!--\; ???\; -->1}$ . The structure is interpreted as the result of overlapping excited B${}_s^0$ states. With high significance, a two-peak hypothesis provides a better description of the data than a single resonance. Under this hypothesis the masses and widths of the two states, assuming they decay directly to B${}^{\pm <!--\; ??\; -->}$K${}^{\mp <!--\; ???\; -->}$ , are determined to be m${}_1$ = 6063.5 ± 1.2 (stat) ± 0.8 (syst) MeV, ${\mathrm{\Gamma <!--\; ??\; -->}}_1$ = 26 ± 4 (stat) ± 4 (syst) MeV, m${}_2$ = 6114 ± 3 (stat) ± 5 (syst) MeV, ${\mathrm{\Gamma <!--\; ??\; -->}}_2$ = 66 ± 18 (stat) ± 21 (syst) MeV. Alternative values assuming a decay through B${}^{\ast <!--\; ???\; -->\pm <!--\; ??\; -->}$K${}^{\mp <!--\; ???\; -->}$ , with a missing photon from the B${}^{\ast <!--\; ???\; -->\pm <!--\; ??\; -->}$ → B${}^{\pm <!--\; ??\; -->}$γ decay, which are shifted by approximately 45 Me V, are also determined. The possibility of a single state decaying in both channels is also considered. The ratio of the total production cross-section times branching fraction of the new states relative to the previously observed B${}_{s2}^{\ast <!--\; ???\; -->0}$ state is determined to be 0.87 ± 0.15 (stat) ± 0.19 (syst).

[en] A flavour-tagged time-dependent angular analysis of B${}_s^0$ → J/$\mathrm{\psi <!--\; ??\; -->}\mathrm{\varphi <!--\; ??\; -->}$ decays is presented where the J/$\mathrm{\psi <!--\; ??\; -->}$ meson is reconstructed through its decay to an $e^{+}{e}^{-<!--\; ???\; -->}$ pair. The analysis uses a sample of pp collision data recorded with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV , corresponding to an integrated luminosity of 3 fb${}^{-<!--\; ???\; -->1}$. The CP-violating phase and lifetime parameters of the B${}_s^0$ system are measured to be ${\mathrm{\varphi <!--\; ??\; -->}}_s$ = 0.00±0.28±0.07 rad, $\mathrm{\Delta <!--\; ??\; -->}{\mathrm{\Gamma <!--\; ??\; -->}}_s$ = 0.115±0.045±0.011 ps${}^{-<!--\; ???\; -->1}$ and ${\mathrm{\Gamma <!--\; ??\; -->}}_s$ = 0.608±0.018±0.012 ps${}^{-<!--\; ???\; -->1}$ where the first uncertainty is statistical and the second systematic. This is the first time that CP-violating parameters are measured in the B${}_s^0$ → J/$\mathrm{\psi <!--\; ??\; -->}\mathrm{\varphi <!--\; ??\; -->}$ decay with an $e^{+}{e}^{-<!--\; ???\; -->}$ pair in the final state. The results are consistent with previous measurements in other channels and with the Standard Model predictions.

[en] The most likely path formalism (MLP) is widely established as the most statistically precise method for proton path reconstruction in proton computed tomography. However, while this method accounts for small-angle multiple coulomb scattering (MCS) and energy loss, inelastic nuclear interactions play an influential role in a significant number of proton paths. By applying cuts based on energy and direction, tracks influenced by nuclear interactions are largely discarded from the MLP analysis. In this work we propose a new method to estimate the proton paths based on a deep neural network (DNN). Through this approach, estimates of proton paths equivalent to MLP predictions have been achieved in the case where only MCS occurs, together with an increased accuracy when nuclear interactions are present. Moreover, our tests indicate that the DNN algorithm can be considerably faster than the MLP algorithm. (paper)