Measurement of Upsilon production in pp collisions at \sqrt{s} = 7 TeV

The production of Upsilon(1S), Upsilon(2S) and Upsilon(3S) mesons in proton-proton collisions at the centre-of-mass energy of sqrt(s)=7 TeV is studied with the LHCb detector. The analysis is based on a data sample of 25 pb-1 collected at the Large Hadron Collider. The Upsilon mesons are reconstructed in the decay mode Upsilon -> mu+ mu- and the signal yields are extracted from a fit to the mu+ mu- invariant mass distributions. The differential production cross-sections times dimuon branching fractions are measured as a function of the Upsilon transverse momentum pT and rapidity y, over the range pT < 15 GeV/c and 2.0 < y < 4.5. The cross-sections times branching fractions, integrated over these kinematic ranges, are measured to be sigma(pp -> Upsilon(1S) X) x B(Upsilon(1S)->mu+ mu-) = 2.29 {\pm} 0.01 {\pm} 0.10 -0.37 +0.19 nb, sigma(pp -> Upsilon(2S) X) x B(Upsilon(2S)->mu+ mu-) = 0.562 {\pm} 0.007 {\pm} 0.023 -0.092 +0.048 nb, sigma(pp -> Upsilon(3S) X) x B(Upsilon(3S)->mu+ mu-) = 0.283 {\pm} 0.005 {\pm} 0.012 -0.048 +0.025 nb, where the first uncertainty is statistical, the second systematic and the third is due to the unknown polarisation of the three Upsilon states.Comment: 22 pages, 7 figure

Theoretical study of the gas-phase thermolysis reaction of 3,6-dimethyl-1,2,4,5-tetroxane. Methyl and axial-equatorial substitution effects

Organic peroxides are interesting compounds with a broad range of properties from antimalarial and antimicrobial activities to explosive character. In this work the gas-phase thermolysis reaction mechanism of the 3,6-dimethyl-1,2,4,5-tetroxane (DMT) is studied by DFT calculations, considering axial–axial, axial–equatorial, and equatorial–equatorial position isomers. The critical points of the singlet (S) and triplet (T) potential energy surfaces (PES) are calculated. Three mechanisms are considered: i) S-concerted, ii) S-stepwise, and iii) T-stepwise. The first intermediate of the reaction through S-stepwise-PES is a diradical open structure, o, yielding, as products, two molecules of acetaldehyde and one of O in the S state. The S-stepwise-mechanism gives exothermic reaction energies (Er) in the three position isomers. The S-concerted mechanism yields very high activation energies (Ea) in comparison with those of the S-stepwise mechanism. In the T-stepwise mechanism, a triplet open structure (T-o) is first considered, yielding an Er 12 kcal mol more exothermic than that of the S-mechanisms. The S-o and T-o are similar in structure and energies; therefore, a crossing from the S- to T-PES is produced at the o intermediate as a consequence of a spin–orbit coupling. The highest Ea is the first step after o intermediate, and thus it is considered the rate limiting step. Therefore, the Er at the T-PES is more in agreement with the Er of the exothermic experimental diperoxide products. Ea, Er, and O···O distances are studied as a function of the number of methyl groups and the position isomerization.The authors thank the “Centro de Supercomputación de Galicia” (CESGA), and “Centro de Servicios de Informática y Redes de Comunicaciones (CSIRC), Universidad de Granada” (Spain) for providing the computing time. The authors are thankful to “Secretaría General de Ciencia y Técnica de la UNNE (Argentina)”. This work was supported by Spanish MCINN and European FEDER grants FIS2016-77692-C2-2P, PCIN-2017-098 and by the regional agency “Junta de Andalucía” for the RNM-264, -363 and -1897 PAI-grants

Measurement of relative branching fractions of B decays to psi(2S) and J/psi mesons

The relative rates of B-meson decays into J/psi and psi(2S) mesons are measured for the three decay modes in pp collisions recorded with the LHCb detector. The ratios of branching fractions (B) are measured to be B(B+ -> psi(2S)K+)/B(B+ -> J/psi K+) = 0.594 +/- 0.006(stat) +/- 0.016(syst) +/- 0.015(R-psi), B(B-0 -> psi(2S)K*(0))/B(B-0 -> J/psi K*(0)) = 0.476 +/- 0.014(stat) +/- 0.010(syst) +/- 0.012(R-psi), B(B-s(0) -> psi(2S)phi)/B(B-s(0) -> J/psi phi) = 0.489 +/- 0.026(stat) +/- 0.021(syst) +/- 0.012(R-psi), where the third uncertainty is from the ratio of the psi(2S) and J/psi branching fractions to mu(+)mu(-). RI Galli, Domenico/A-1606-2012; Sarti, Alessio/I-2833-2012; Petrolini, Alessandro/H-3782-2011; Carbone, Angelo/C-8289-2012; de Paula, Leandro/I-9278-2012; manca, giulia/I-9264-2012; Patrignani, Claudia/C-5223-2009; Marconi, Umberto/J-2263-2012; de Simone, Patrizia/J-3549-2012; Cardini, Alessandro/J-5736-2012; Teodorescu, Eliza/K-3044-201

Observation of Excited Lambda(0)(b) Baryons

Using pp collision data corresponding to 1.0 fb-1 integrated luminosity collected by the LHCb detector, two narrow states are observed in the Lambda0b pi+ pi- spectrum with masses 5911.97+-0.12(stat)+-0.02(syst)+- 0.66(Lambda0b mass) MeV/c2 and 5919.77+-0.08(stat)+-0.02(syst)+-0.66(Lambda0b mass) MeV/c2. The significances of the observations are 5.2 and 10.2 standard deviations, respectively. These states are interpreted as the orbitally excited Lambda0b baryons, Lambda*0b(5912) and Lambda*0b(5920)