LHCb

Abstract:

Using samples of (5.93±0.10)×106 Υ(3S) decays and (9.11±0.14)×106 Υ(2S) decays collected with the CLEO detector, we report improved measurements of the following branching fractions: B(Υ(3S)→Υ(1S)π+π-)=(4.46±0.01±0.13)%, B(Υ(2S)→Υ(1S)π+π-)=(18.02±0.02±0.61)%, B(Υ(3S)→Υ(1S)π0π0)=(2.24±0.09±0.11)%, B(Υ(2S)→Υ(1S)π0π0)=(8.43±0.16±0.42)%, and B(Υ(3S)→Υ(2S)π0π0)=(1.82±0.09±0.12)%. In each case, the first uncertainty reported is statistical, while the second is systematic. © 2009 The American Physical Society.

Abstract:

Using 2.45×107 ψ(2S) decays collected with the CLEO-c detector at the Cornell Electron Storage Ring we present the most precise measurements of magnetic dipole transitions in the charmonium system. We measure B(ψ(2S)→γηc)=(4.32±0.16±0.60)×10-3, B(J/ψ→γηc)/B(ψ(2S)→γηc)=4.59±0. 23±0.64, and B(J/ψ→γηc)=(1.98±0.09±0.30) %. We observe a distortion in the ηc line shape due to the photon-energy dependence of the magnetic dipole transition rate. We find that measurements of the ηc mass are sensitive to the line shape, suggesting an explanation for the discrepancy between measurements of the ηc mass in radiative transitions and other production mechanisms. © 2009 The American Physical Society.

Abstract:

We search for b→sμ+μ- transitions in B meson (B+, B0, or Bs0) decays with 924pb-1 of pp̄ collisions at s=1.96TeV collected with the CDF II detector at the Fermilab Tevatron. We find excesses with significances of 4.5, 2.9, and 2.4 standard deviations in the B+→μ+μ-K+, B0→μ+μ-K*(892)0, and Bs0→μ+μ- decay modes, respectively. Using B→J/ψh (h=K+, K*(892)0,) decays as normalization channels, we report branching fractions for the previously observed B+ and B0 decays, B(B+→μ+μ-K+)=(0.59±0.15±0. 04)×10-6, and B(B0→μ+μ-K*(892)0)=(0.81±0. 30±0.10)×10-6, where the first uncertainty is statistical, and the second is systematic. We set an upper limit on the relative branching fraction B(Bs0→μ+μ-)/B(Bs0→J/ψ)<2.6(2.3)×10-3 at the 95(90)% confidence level, which is the most stringent to date. © 2009 The American Physical Society.

Abstract:

A series of tests in CERN’s North Area beam facility have been used to demonstrate the suitability of the Timepix chip, combined with a silicon sensor, as a particle tracking device. Specifically of interest is the potential of a successor to the current chip to be used in the context of an LHCb VELO upgrade. The 55µm square pixels, large active fraction and analogue information make the chip very attractive for forward, high precision tracking systems such as the VELO. In this contribution preliminary results are presented showing the resolution achieved by a Timepix assembly in a 120GeV π beam, over a wide range of incident angles. At the optimum angle the detector was able to provide an unbiased track residual of 5.5µm. The telescope constructed for these measurements contributed a track extrapolation error of 2.5µm. The plans for a future development of this telescope, also based on Timepix assemblies are discussed, with proposals for upgrading its spatial and timing resolution.

Abstract:

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. 55μm 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. ©2009 IEEE.