A structure is observed in the Formula omitted 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 Formula omitted. The structure is interpreted as the result of overlapping excited Formula omitted 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 Formula omitted, are determined to be m1=6063.5±1.2(stat)±0.8(syst)Me,GAMMA1=26±4(stat)±4(syst)Me,m2=6114±3(stat)±5(syst)Me,GAMMA2=66±18(stat)±21(syst)Me.Alternative values assuming a decay through Formula omitted, with a missing photon from the Formula omitted decay, which are shifted by approximately 45 Formula omittedV, 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 Formula omitted state is determined to be Formula omitted.
A branching fraction measurement of the Formula omitted decay is presented using proton-proton collision data collected with the LHCb experiment, corresponding to an integrated luminosity of Formula ...omitted. The branching fraction is found to be Formula omitted Formula omitted, where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the Formula omitted, Formula omitted and Formula omitted branching fractions. This is the most precise single measurement of this quantity to date. As this decay proceeds through a single amplitude involving a Formula omitted charged-current transition, the result provides information on non-factorisable strong interaction effects and the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element Formula omitted. Additionally, the collision energy dependence of the hadronisation-fraction ratio Formula omitted is measured through Formula omitted and Formula omitted decays.
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 Formula omitted of proton-proton ...collision data at centre-of-mass energies of 7 and Formula omitted 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 Formula omitted confidence level in the heavy-neutrino mass range from 5 to Formula omitted. These are of the order of Formula omitted for lepton-number-conserving decays and of the order of Formula omitted for lepton-number-violating heavy-neutrino decays.
Long-lived particles decaying to Formula omitted, with masses between 7 and Formula omitted and lifetimes between 2 and Formula omitted, are searched for by looking at displaced vertices containing ...electrons and muons of opposite charges. The search is performed using Formula omitted of Formula omitted Formula omitted collisions collected with the LHCb detector at a centre-of-mass energy of Formula omitted. 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 Formula omitted, and the charged current production from an on-shell Formula omitted 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.
A search is performed for massive long-lived particles (LLPs) decaying semileptonically into a muon and two quarks. Two kinds of LLP production processes were considered. In the first, a Higgs-like ...boson with mass from 30 to 200 Formula omitted is produced by gluon fusion and decays into two LLPs. The analysis covers LLP mass values from 10 Formula omitted up to about one half the Higgs-like boson mass. The second LLP production mode is directly from quark interactions, with LLP masses from 10 to 90 Formula omitted. The LLP lifetimes considered range from 5 to 200 ps. This study uses LHCb data collected from proton-proton collisions at Formula omitted, corresponding to an integrated luminosity of 5.4 Formula omitted. No evidence of these long-lived states has been observed, and upper limits on the production cross-section times branching ratio have been set for each model considered.
A first search for Formula omitted violation in the Cabibbo-suppressed Formula omitted 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 Formula omitted, and collected by the LHCb experiment at centre-of-mass energies of 7 and Formula omitted. The data are consistent with the hypothesis of no Formula omitted violation.
Using a data sample corresponding to an integrated luminosity of 2.0 Formula omitted, collected by the LHCb experiment, the production of the Formula omitted state in proton-proton collisions at a ...centre-of-mass energy of Formula omitted Formula omitted is studied in the rapidity range Formula omitted and in the transverse momentum range Formula omitted. The cross-section for prompt production of Formula omitted mesons relative to that of the Formula omitted meson is measured using the Formula omitted Formula omitted decay mode and is found to be Formula omitted. The quoted uncertainties are, in order, statistical, systematic and due to uncertainties on the branching fractions of the Formula omitted and Formula omitted decays. The prompt Formula omitted production cross-section is determined to be Formula omitted, where the last uncertainty includes that on the Formula omitted meson cross-section. The ratio of the branching fractions of Formula omitted-hadron decays to the Formula omitted and Formula omitted states is measured to be Formula omitted, where the last uncertainty is due to those on the branching fractions of the Formula omitted and Formula omitted decays. The difference between the Formula omitted and Formula omitted masses is also determined to be Formula omitted, which is the most precise single measurement of this quantity to date.
The decay-time-dependent Formula omitted asymmetry in Formula omitted decays is measured using proton-proton collision data, corresponding to an integrated luminosity of Formula omitted, collected ...with the LHCb detector at a centre-of-mass energy of Formula omitted in 2015 and 2016. Using a sample of approximately 117 000 signal decays with an invariant Formula omitted mass in the vicinity of the Formula omitted resonance, the Formula omitted-violating phase Formula omitted is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the Formula omitted- Formula omitted system, Formula omitted. The difference of the average Formula omitted and Formula omitted meson decay widths, Formula omitted, is determined using in addition a sample of Formula omitted decays. The values obtained are Formula omitted, Formula omitted and Formula omitted, 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 Formula omitted decays obtained using the same dataset as this analysis, and with previous independent LHCb results.
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