Central Exclusive Production at LHCb

The search for central exclusive production of muon pairs is performed using the LHCb data acquired on 2011 ($\sqrt{s} = 7$ TeV) and 2012 ($\sqrt{s} = 8$ TeV). Preliminary measurements of cross section using these samples are showed and a first comparison with theoretical previews is presented

Synchrotron tests of 3D Medipix2 and TimePix X-ray detectors

In this article we report on the use micro-focus synchrotron X-ray radiation and pion beams to compare the detection efficiencies and charge sharing properties of novel 3D detectors to that of the current planar technology. Detector substrates are bump-bonded to the Medipx2 and Timepix chips. 55¿m square pixel maps of the detection efficiencies have been produced using X-ray and MIP beams. For X-rays, a drop of 3-4% detection efficiency over the pixel area was found due to the central electrode. The corner electrodes show no degradation in efficiency compared to that of the planar device. For MIPs a drop of 0.5% in efficiency due to the central electrode was observed. Evidence of a considerable reduction in charge sharing in the 3D detectors compared to the planar devices is also shown

Determination of the quark coupling strength vertical bar V-ub vertical bar using baryonic decays

In the Standard Model of particle physics, the strength of the couplings of the b quark to the u and c quarks, vertical bar V-ub vertical bar and vertical bar V-ub vertical bar, are governed by the coupling of the quarks to the Higgs boson. Using data from the LHCb experiment at the Large Hadron Collider, the probability for the Lambda(0)(b) baryon to decay into the p mu(-)(nu) over bar (mu) final state relative to the Lambda(+)(c)mu(-)(nu) over bar (mu) final state is measured. Combined with theoretical calculations of the strong interaction and a previously measured value of vertical bar V-ub vertical bar, the first vertical bar V-ub vertical bar measurement to use a baryonic decay is performed. This measurement is consistent with previous determinations of vertical bar V-ub vertical bar using B meson decays to specific final states and confirms the existing incompatibility with those using an inclusive sample of final states

Measurement of psi (2S) production cross-sections in proton-proton collisions at v s=7 and 13 TeV

The cross-sections of \u3c8(2 S) meson production in proton-proton collisions at s=13TeV are measured with a data sample collected by the LHCb detector corresponding to an integrated luminosity of 275pb-1. The production cross-sections for prompt \u3c8(2 S) mesons and those for \u3c8(2 S) mesons from b-hadron decays (\u3c8(2S)-from-b) are determined as functions of the transverse momentum, pT, and the rapidity, y, of the \u3c8(2 S) meson in the kinematic range 2<20GeV/c and 2.0 < y< 4.5. The production cross-sections integrated over this kinematic region are \u3c3(prompt\u3c8(2S),13TeV)=1.430\ub10.005(stat)\ub10.099(syst)\u3bcb,\u3c3(\u3c8(2S)-from-b,13TeV)=0.426\ub10.002(stat)\ub10.030(syst)\u3bcb.A new measurement of \u3c8(2 S) production cross-sections in pp collisions at s=7TeV is also performed using data collected in 2011, corresponding to an integrated luminosity of 614pb-1. The integrated production cross-sections in the kinematic range 3.5<14GeV/c and 2.0 < y< 4.5 are \u3c3(prompt\u3c8(2S),7TeV)=0.471\ub10.001(stat)\ub10.025(syst)\u3bcb,\u3c3(\u3c8(2S)-from-b,7TeV)=0.126\ub10.001(stat)\ub10.008(syst)\u3bcb.All results show reasonable agreement with theoretical calculations

Measurement of the eta(c)(1S) production cross-section in p p collisions at root s=13TeV

Using a data sample corresponding to an integrated luminosity of 2.0 fb-1, collected by the LHCb experiment, the production of the \u3b7c(1 S) state in proton\u2013proton collisions at a centre-of-mass energy of s=13TeV is studied in the rapidity range 2.0 < y< 4.5 and in the transverse momentum range 6.5<14.0GeV. The cross-section for prompt production of \u3b7c(1 S) mesons relative to that of the J/ \u3c8 meson is measured using the pp\uaf decay mode and is found to be \u3c3\u3b7c(1S)/\u3c3J/\u3c8=1.69\ub10.15\ub10.10\ub10.18. The quoted uncertainties are, in order, statistical, systematic and due to uncertainties on the branching fractions of the J/\u3c8\u2192pp\uaf and \u3b7c\u2192pp\uaf decays. The prompt \u3b7c(1 S) production cross-section is determined to be \u3c3\u3b7c(1S)=1.26\ub10.11\ub10.08\ub10.14\u3bcb, where the last uncertainty includes that on the J/ \u3c8 meson cross-section. The ratio of the branching fractions of b-hadron decays to the \u3b7c(1 S) and J/ \u3c8 states is measured to be Bb\u2192\u3b7cX/Bb\u2192J/\u3c8X=0.48\ub10.03\ub10.03\ub10.05, where the last uncertainty is due to those on the branching fractions of the J/\u3c8\u2192pp\uaf and \u3b7c\u2192pp\uaf decays. The difference between the J/ \u3c8 and \u3b7c(1 S) masses is also determined to be 113.0\ub10.7\ub10.1MeV, which is the most precise single measurement of this quantity to date