3,732 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 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
Monte Carlo Studies of a Novel LiF Radiator for RICH Detectors
We show that a multifaceted LiF radiator produces more Cherenkov light and
has better resolution per photon than a flat radiator slab when used in a ring
imaging Cherenkov counter. Such a system is being considered for the CLEO III
upgrade.Comment: 9 page
Test of the photon detection system for the LHCb RICH Upgrade in a charged particle beam
The LHCb detector will be upgraded to make more efficient use of the
available luminosity at the LHC in Run III and extend its potential for
discovery. The Ring Imaging Cherenkov detectors are key components of the LHCb
detector for particle identification. In this paper we describe the setup and
the results of tests in a charged particle beam, carried out to assess
prototypes of the upgraded opto-electronic chain from the Multi-Anode PMT
photosensor to the readout and data acquisition system.Comment: 25 pages, 22 figure
A New Model for Fermion Masses in Supersymmetric Grand Unified Theories
We present a simple model for fermion mass matrices and quark mixing in the
context of supersymmetric grand unified theories and show its agreement with
experiment. Our model realizes the GUT mass relations , , in a new way and is easily consistent with values of
suggested by MSSM fits to LEP data.Comment: Latex, 8 p., ITP-SB-93-37 (revised version contains minor changes in
some wording and citations; no changes in analytic or numerical results.
The Semileptonic Decays and from QCD Sum Rules
We investigate the semileptonic decays of B and D mesons into and
mesons, respectively, by means of QCD sum rules. We find that for the
vector formfactors involved the pole dominance hypothesis is valid to good
accuracy with pole masses in the expected range. Pole dominance, however, does
not apply to the axial formfactors which results in specific predictions for
the predominant polarization of the meson and the shape of the lepton
spectrum. For the total decay rates we find , , and .Comment: 23 pages, 12 figures included as uu-encoded file, needs REVTEX,
TUM--T31--39/9
Anomalous coupling effects in exclusive radiative B-meson decays
The top-quark FCNC processes will be searched for at the CERN LHC, which are
correlated with the B-meson decays. In this paper, we study the effects of
top-quark anomalous interactions in the exclusive radiative and decays. With the current experimental data of
the branching ratios, the direct CP and the isospin asymmetries, bounds on the
coupling from and
from decays are derived,
respectively. The bound on from is generally compatible with that from . However, the isospin asymmetry further
restrict the phase of , and the combined bound results
in the upper limit, , which is lower than the
CDF result. For real , the upper bound on is about of the same order as the discovery
potential of ATLAS with an integrated luminosity of . For
decays, the NP contribution is enhanced by a large CKM factor
, and the constraint on coupling is rather
restrictive, . With refined
measurements to be available at the LHCb and the future super-B factories, we
can get close correlations between and the rare
decays, which will be studied directly at the LHC ATLAS and CMS.Comment: 25 pages, 15 figures, pdflate
Bayesian Fit of Exclusive Decays: The Standard Model Operator Basis
We perform a model-independent fit of the short-distance couplings
within the Standard Model set of and operators. Our analysis of , and decays is the first to harness the full
power of the Bayesian approach: all major sources of theory uncertainty
explicitly enter as nuisance parameters. Exploiting the latest measurements,
the fit reveals a flipped-sign solution in addition to a Standard-Model-like
solution for the couplings . Each solution contains about half of the
posterior probability, and both have nearly equal goodness of fit. The Standard
Model prediction is close to the best-fit point. No New Physics contributions
are necessary to describe the current data. Benefitting from the improved
posterior knowledge of the nuisance parameters, we predict ranges for currently
unmeasured, optimized observables in the angular distributions of .Comment: 42 pages, 8 figures; v2: Using new lattice input for f_Bs,
considering Bs-mixing effects in BR[B_s->ll]. Main results and conclusion
unchanged, matches journal versio
Study of Z Boson Pair Production in e+e- Collisions at LEP at \sqrt{s}=189 GeV
The pair production of Z bosons is studied using the data collected by the L3
detector at LEP in 1998 in e+e- collisions at a centre-of-mass energy of 189
GeV. All the visible final states are considered and the cross section of this
process is measured to be 0.74 +0.15 -0.14 (stat.) +/- 0.04 (syst.) pb. Final
states containing b quarks are enhanced by a dedicated selection and their
production cross section is found to be 0.18 +0.09 -0.07 (stat.) +/- 0.02
(syst.) pb. Both results are in agreement with the Standard Model predictions.
Limits on anomalous couplings between neutral gauge bosons are derived from
these measurements
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