Raman spectra of the Markovka chondrite (H4)

Raman spectroscopy and scanning electron microscopy methods were used to study the fragment of the Markovka (H4 chondrite) meteorite. A characteristic set of silicate minerals (olivine and pyroxene), oxides and hydroxides (maghemite and goethite), troilite, and carbonates (aragonite) was determined. The structural features revealed by Raman spectroscopy allow us to draw important conclusions on thermal history of the parent body including both the temperature experienced by the rock on the parent body and their cooling rate as well as the constraints on the size of the parent body and the Mg composition of the assumed fluid

Evidence of a J/ψΛJ/\psi\Lambda structure and observation of excited Ξ−\Xi^- states in the Ξb−→J/ψΛK−\Xi^-_b \to J/\psi\Lambda K^- decay

First evidence of a structure in the $J/\psi{\Lambda}$ invariant mass distribution is obtained from an amplitude analysis of $\Xi_b^-{\rightarrow}J/\psi{\Lambda}K^-$ decays. The observed structure is consistent with being due to a charmonium pentaquark with strangeness with a significance of $3.1\sigma$ including systematic uncertainties and look-elsewhere effect. Its mass and width are determined to be $4458.8\pm2.9^{+4.7}_{-1.1}$ MeV and $17.3\pm6.5^{+8.0}_{-5.7}$ MeV, respectively, where the quoted uncertainties are statistical and systematic. The structure is also consistent with being due to two resonances. In addition, the narrow excited $\Xi^-$ states, $\Xi(1690)^-$ and $\Xi(1820)^-$, are seen for the first time in a $\Xi^-_b$ decay, and their masses and widths are measured with improved precision. The analysis is performed using $pp$ collision data corresponding to a total integrated luminosity of 9 fb$^{-1}$, collected with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV

Search for long-lived particles decaying to e±μ∓νe^\pm \mu^\mp \nu

International audienceLong-lived particles decaying to ${e ^\pm } {\mu ^\mp } {\nu }$, with masses between 7 and $50 \,\text {GeV/}c^2$ and lifetimes between 2 and $50 \,\text {ps}$, are searched for by looking at displaced vertices containing electrons and muons of opposite charges. The search is performed using $5.4 \,\text {fb} ^{-1}$ of $p p$ collisions collected with the LHCb detector at a centre-of-mass energy of $\sqrt{s} = 13 \,\text {TeV}$. 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 $125 \,\text {GeV/}c^2$, 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

Observation of Multiplicity Dependent Prompt χc1(3872)\chi_{c1}(3872) and ψ(2S)\psi(2S) Production in pppp Collisions

The production of $χ_{c1}$(3872) and $ψ$(2S) hadrons is studied as a function of charged particle multiplicity in pp collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 2 fb-1. For both states, the fraction that is produced promptly at the collision vertex is found to decrease as charged particle multiplicity increases. The ratio of $χ_{c1}$(3872) to $ψ$(2S) cross sections for promptly produced particles is also found to decrease with multiplicity, while no significant dependence on multiplicity is observed for the equivalent ratio of particles produced away from the collision vertex in b-hadron decays. This behavior is consistent with a calculation that models the $χ_{c1}$(3872) structure as a compact tetraquark. Comparisons with model calculations and implications for the binding energy of the $χ_{c1}$(3872) state are discussed

First observation of the decay Λb0→ηc(1S)pK−\Lambda_b^0 \to \eta_c(1S) p K^-

International audienceThe decay Λb0→ηc(1S)pK- is observed for the first time using a data sample of proton-proton collisions, corresponding to an integrated luminosity of 5.5  fb-1, collected with the LHCb experiment at a center-of-mass energy of 13 TeV. The branching fraction of the decay is measured, using the Λb0→J/ψpK- decay as a normalization mode, to be B(Λb0→ηc(1S)pK-)=(1.06±0.16±0.06-0.19+0.22)×10-4, where the quoted uncertainties are statistical, systematic and due to external inputs, respectively. A study of the ηc(1S)p mass spectrum is performed to search for the Pc(4312)+ pentaquark state. No evidence is observed and an upper limit of B(Λb0→Pc(4312)+K-)×B(Pc(4312)+→ηc(1S)p)B(Λb0→ηc(1S)pK-)<0.24 is obtained at the 95% confidence level

Measurement of CP Violation in the Decay B+→K+π0B^{+} \rightarrow K^{+} \pi^{0}

International audienceA measurement of CP violation in the decay B+→K+π0 is reported using data corresponding to an integrated luminosity of 5.4  fb-1 collected with the LHCb experiment at a center-of-mass energy of s=13  TeV. The CP asymmetry is measured to be 0.025±0.015±0.006±0.003, where the uncertainties are statistical, systematic, and due to an external input. This is the most precise measurement of this quantity. It confirms and significantly enhances the observed anomalous difference between the direct CP asymmetries of the B+→K+π- and B+→K+π0 decays, known as the Kπ puzzle

Observation of a new Ξb0\Xi_b^0 state

International audienceUsing a proton-proton collision data sample collected by the LHCb experiment, corresponding to an integrated luminosity of 8.5  fb-1, the observation of a new excited Ξb0 resonance decaying to the Ξb-π+ final state is presented. The state, referred to as Ξb(6227)0, has a measured mass and natural width of m(Ξb(6227)0)=6227.1-1.5+1.4±0.5  MeV and Γ(Ξb(6227)0)=18.6-4.1+5.0±1.4  MeV, where the uncertainties are statistical and systematic. The production rate of the Ξb(6227)0 state relative to that of the Ξb- baryon in the kinematic region 2<η<5 and pT<30  GeV is measured to be fΞb(6227)0fΞb-B(Ξb(6227)0→Ξb-π+)=0.045±0.008±0.004, where B(Ξb(6227)0→Ξb-π+) is the branching fraction of the decay, and fΞb(6227)0 and fΞb- represent fragmentation fractions. Improved measurements of the mass and natural width of the previously observed Ξb(6227)- state, along with the mass of the Ξb- baryon, are also reported. Both measurements are significantly more precise than, and consistent with, previously reported values