5,701 research outputs found
B and D Spectroscopy at LEP
Results from the four LEP experiments ALEPH, DELPHI, L3, and OPAL on the
spectroscopy of B and charmed mesons are presented. The predictions of Heavy
Quark Effective Theory (HQET) for the masses and the widths of excited L=1 B
mesons are supported by a new measurement from L3. A few B_c candidate eve nts
have masses consistent with the recent CDF observation and the predictions. New
results on Ddstar production and B -> Ddstar l nu are also presented. The
evidence for a Dstarpr meson reported recently by DELPHI is not supported by
OPAL and CLEO.Comment: 10 pages, 6 figure
Multianode Photo Multipliers for Ring Imaging Cherenkov Detectors
The 64-channel Multianode Photo Multiplier has been evaluated as a possible
choice for the photo detectors of the LHCb Ring Imaging Cherenkov detector.Comment: 3 pages, 3 figures, contributed to the Proceedings of ICHEP200
Status of the LHCb Experiment
We present the status of the LHCb experiment which will make precision
measurements of CP violation in meson decays. The motivation for the
experiment and an overview of the detector design are given. The vertex
detector, ring imaging Cherenkov counter, calorimeters, and trigger systems are
discussed in detail. We also present the expected physics performance for
selected modes.Comment: 10 pages, 16 figures, presented at BEAUTY2000, Israe
Multianode Photo Multiplier Tubes as Photo Detectors for Ring Imaging Cherenkov Detectors
The 64-channel Multianode Photo Multiplier (MaPMT) has been evaluated as a
candidate for the LHCb Ring Imaging Cherenkov (RICH) photo detectors. We
present result from data taken with a 3x3 array of closely packed MaPMTs
mounted onto the RICH 1 prototype vessel, exposed to charged particle beams at
CERN, and read out at LHC speed. Using a LED light source, we have performed
spatial light scans to study the light collection efficiency of the MaPMTs We
have also measured the performance of the MaPMTs as a function of the applied
high voltage. Different dynode resistor chains have been used to study the
tubes at low gains. In addition, we have studied the behaviour of the MaPMT in
magnetic fields.Comment: 5 pages, 6 figures, 8 .eps files, RICH2002 conference, Pylo
Quantum dynamics of the avian compass
The ability of migratory birds to orient relative to the Earth's magnetic
field is believed to involve a coherent superposition of two spin states of a
radical electron pair. However, the mechanism by which this coherence can be
maintained in the face of strong interactions with the cellular environment has
remained unclear. This Letter addresses the problem of decoherence between two
electron spins due to hyperfine interaction with a bath of spin 1/2 nuclei.
Dynamics of the radical pair density matrix are derived and shown to yield a
simple mechanism for sensing magnetic field orientation. Rates of dephasing and
decoherence are calculated ab initio and found to yield millisecond coherence
times, consistent with behavioral experiments
Development and verification of global/local analysis techniques for laminated composites
A two-dimensional to three-dimensional global/local finite element approach was developed, verified, and applied to a laminated composite plate of finite width and length containing a central circular hole. The resulting stress fields for axial compression loads were examined for several symmetric stacking sequences and hole sizes. Verification was based on comparison of the displacements and the stress fields with those accepted trends from previous free edge investigations and a complete three-dimensional finite element solution of the plate. The laminates in the compression study included symmetric cross-ply, angle-ply and quasi-isotropic stacking sequences. The entire plate was selected as the global model and analyzed with two-dimensional finite elements. Displacements along a region identified as the global/local interface were applied in a kinematically consistent fashion to independent three-dimensional local models. Local areas of interest in the plate included a portion of the straight free edge near the hole, and the immediate area around the hole. Interlaminar stress results obtained from the global/local analyses compares well with previously reported trends, and some new conclusions about interlaminar stress fields in plates with different laminate orientations and hole sizes are presented for compressive loading. The effectiveness of the global/local procedure in reducing the computational effort required to solve these problems is clearly demonstrated through examination of the computer time required to formulate and solve the linear, static system of equations which result for the global and local analyses to those required for a complete three-dimensional formulation for a cross-ply laminate. Specific processors used during the analyses are described in general terms. The application of this global/local technique is not limited software system, and was developed and described in as general a manner as possible
LHCb Upgrade Plans
The LHCb experiment will operate for about five years at a luminosity of
2x10^32 cm^-2 s^-1 and plans are to accumulate a data sample of ~10 fb^-1. Here
we present the physics programme and detector design for a future high
luminosity phase of the LHCb experiment. An upgraded LHCb experiment would
operate at ten times the design luminosity, i.e. at ~2x10^33 cm^-2 s^-1 and
aims to collect a data sample of ~100 fb^-1 over five years. This programme
would allow the probe of new physics at an unprecedented level. Key
measurements include the B^0_s mixing phase phi_s in B^0_s -> J/\psi phi and
B^0_s -> phi phi decays with a significant sensitivity to the small Standard
Model prediction and a very precise measurement of the CKM angle gamma in tree
diagram decays. Initial studies of the modified LHCb trigger and detectors are
presented. The upgraded LHCb experiment can run with or without an LHC
luminosity upgrade.Comment: 6 pages, 2 figures, to appear in the proceedings of International
Conference on B-Physics at Hadron Machines (Beauty 2006), Oxford, England,
25-29 Sep 200
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