Observation of Two New Excited Ξb0 States Decaying to Λb0 K-π+

Two narrow resonant states are observed in the Λb0K-π+ mass spectrum using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 6 fb-1. The minimal quark content of the Λb0K-π+ system indicates that these are excited Ξb0 baryons. The masses of the Ξb(6327)0 and Ξb(6333)0 states are m[Ξb(6327)0]=6327.28-0.21+0.23±0.12±0.24 and m[Ξb(6333)0]=6332.69-0.18+0.17±0.03±0.22 MeV, respectively, with a mass splitting of Δm=5.41-0.27+0.26±0.12 MeV, where the uncertainties are statistical, systematic, and due to the Λb0 mass measurement. The measured natural widths of these states are consistent with zero, with upper limits of Γ[Ξb(6327)0]<2.20(2.56) and Γ[Ξb(6333)0]<1.60(1.92) MeV at a 90% (95%) credibility level. The significance of the two-peak hypothesis is larger than nine (five) Gaussian standard deviations compared to the no-peak (one-peak) hypothesis. The masses, widths, and resonant structure of the new states are in good agreement with the expectations for a doublet of 1D Ξb0 resonances

Highlights from the LHCb experiment

We report recent results by the LHCb collaboration in heavy-ion collisions in collider and fixed-target mode at the LHC. A large variety of measurements show the potential of LHCb in nuclear collisions

Erratum to: Measurement of ψ(2S) meson production in pp collisions at √s = 7TeV (vol 72, 2100, 2012)

This erratum corrects measurements of the prompt and secondary (from-b) psi (2S) production cross-sections in the forward region in pp collisions at root s = 7TeV. The original measurements were performed using data collected with the LHCb detector in 2010 and were published in the original article. Corrected results for prompt psi(2S) and psi(2S)from-b in the kinematic range pT(psi(2S)) < 16GeV/c and 2.0 < y(psi(2S)) < 4.5 are where the last uncertainty on the prompt cross-section is due to the unknown psi(2S) polarization. With the corrected psi (2S)-from-b cross-section the inclusive branching fraction is updated by B(b ->psi(2S) X) = (3.08 +/- 0.07(stat) +/- 0.36(syst) +/- 0.27(B)) x 10(-3)

Amplitude analysis of the B0 (s)! K0K0 decays and measurement of the branching fraction of the B0! K0K0 decay

The B→ K∗ 0K¯ ∗ 0 and Bs0→K∗0K¯∗0 decays are studied using proton-proton collision data corresponding to an integrated luminosity of 3 fb−1. An untagged and timeintegrated amplitude analysis of B(s)0 → (K+π−)(K−π+) decays in two-body invariant mass regions of 150 MeV/c2 around the K∗0 mass is performed. A stronger longitudinal polarisation fraction in the B→ K∗ 0K¯ ∗ 0 decay, fL = 0.724 ± 0.051 (stat) ± 0.016 (syst), is observed as compared to fL = 0.240 ± 0.031 (stat) ± 0.025 (syst) in the Bs0→K∗0K¯∗0 decay. The ratio of branching fractions of the two decays is measured and used to determine ℬ(B0→K∗0K¯∗0)=(8.0±0.9(stat)±0.4(syst))×10−7.[Figure not available: see fulltext.

Amplitude analysis of B-s(0) -> K-S(0) K-+/-pi(-/+) decays

The first untagged decay-time-integrated amplitude analysis of Bs0 → KS0K±π∓ decays is performed using a sample corresponding to 3.0 fb−1 of pp collision data recorded with the LHCb detector during 2011 and 2012. The data are described with an amplitude model that contains contributions from the intermediate resonances K*(892)0,+, K2*(1430)0,+ and K0*(1430)0,+, and their charge conjugates. Measurements of the branching fractions of the decay modes Bs0 → K*(892)±K∓ and Bs0→K*(—)(892)0K0(—) are in agreement with, and more precise than, previous results. The decays Bs0 → K0*(1430)±K∓ and Bs0→K0*(—)(1430)0K0(—) are observed for the first time, each with significance over 10 standard deviations

Direct photon production at LHCb

At small Bjorken-x, the large gluon number density in the nucleon leads to gluon recombination competing with gluon splitting, which could result in saturation of the gluon PDF. This gluon saturation has yet to be conclusively observed. Direct photon production provides sensitivity to gluon densities in protons and nuclei, and the forward acceptance of LHCb detector allows for measurements of this process at low Bjorken-x, providing an ideal probe of saturation effects. Progress towards the measurement of forward direct photon production using the LHCb detector is presented