3,208 research outputs found
Nonperturbative QCD Contributions to the Semileptonic Decay Width of the B Meson
Nonperturbative QCD contributions to the inclusive semileptonic decay of the
B meson consist of the dynamic and kinematic components. We calculate the decay
width in an approach based on the light-cone expansion and the heavy quark
effective theory, which is able to include both components of nonperturbative
QCD contributions. The kinematic component results in the phase-space extension
and is shown to be quantitatively crucial, which could increase the decay width
significantly. We find that the semileptonic decay width is enhanced by
long-distance strong interactions by +(9\pm 6)%. This analysis is used to
determine the CKM matrix element |V_{cb}| with a controlled theoretical error.
Implications of the phase-space effects for the nonleptonic decay widths of b
hadrons are briefly discussed. The experimental evidence for the phase-space
effects is pointed out.Comment: 16 pages, Latex, 3 eps figures included, published version
(discussion extended, references updated, the main result unchanged
The CLEO-III Ring Imaging Cherenkov Detector
The CLEO-III Detector upgrade for charged particle identification is
discussed. The RICH design uses solid LiF crystal radiators coupled with
multi-wire chamber photon detectors, using TEA as the photosensor, and
low-noise Viking readout electronics. Results from our beam test at Fermilab
are presented.Comment: Invited talk by R.J. Mountain at ``The 3rd International Workshop on
Ring Imaging Cherenkov Detectors," a research workshop of the Israel Science
Foundation, Ein-Gedi, Dead-Sea, Israel, Nov. 15-20, 1998, 14 pages, 9 figure
The Cleo Rich Detector
We describe the design, construction and performance of a Ring Imaging
Cherenkov Detector (RICH) constructed to identify charged particles in the CLEO
experiment. Cherenkov radiation occurs in LiF crystals, both planar and ones
with a novel ``sawtooth''-shaped exit surface. Photons in the wavelength
interval 135--165 nm are detected using multi-wire chambers filled with a
mixture of methane gas and triethylamine vapor. Excellent pion/kaon separation
is demonstrated.Comment: 75 pages, 57 figures, (updated July 26, 2005 to reflect reviewers
comments), to be published in NIM
A connection between inclusive semileptonic decays of bound and free heavy quarks
A relativistic constituent quark model, formulated on the light-front, is
used to derive a new parton approximation for the inclusive semileptonic decay
width of the B-meson. A simple connection between the decay rate of a free
heavy-quark and the one of a heavy-quark bound in a meson or in a baryon is
established. The main features of the new approach are the treatment of the
b-quark as an on-mass-shell particle and the inclusion of the effects arising
from the b-quark transverse motion in the B-meson. In a way conceptually
similar to the deep-inelastic scattering case, the B-meson inclusive width is
expressed as the integral of the free b-quark partial width multiplied by a
bound-state factor related to the b-quark distribution function in the B-meson.
The non-perturbative meson structure is described through various quark-model
wave functions, constructed via the Hamiltonian light-front formalism using as
input both relativized and non-relativistic potential models. A link between
spectroscopic quark models and the B-meson decay physics is obtained in this
way. Our predictions for the B -> X_c l nu_l and B -> X_u l nu_l decays are
used to extract the CKM parameters |V_cb| and |V_ub| from available inclusive
data. After averaging over the various quark models adopted and including
leading-order perturbative QCD corrections, we obtain |V_cb| = (43.0 +/-
0.7_exp +/- 1.8_th) 10^-3 and |V_ub| = (3.83 +/- 0.48_exp +/- 0.14_th) 10^-3,
implying |V_ub / V_cb| = 0.089 +/- 0.011_exp +/- 0.005_th, in nice agreement
with existing predictions.Comment: revised version with pQCD corrections included, to appear in Physical
Review
from the Hadron Energy Spectrum in Inclusive Semileptonic B Decays
A measurement of the hadron energy spectrum in inclusive semileptonic
decays is proposed as a viable method for extracting . Compared to
the traditional energy spectrum of the charged lepton, the hadron energy
spectrum exhibits kinematical advantages such as a wider energy window and a
larger signal branching fraction. It is emphasized that the hadron energy
spectrum method is most suited for symmetric factories, such as CLEO. The
hadron energy distribution is calculated in the approach of the Altarelli et
al. model and of the heavy-quark effective field theory. In both methods,
perturbative QCD corrections, the Fermi motion of the -quark in the
-meson, and the recoil momentum of the -meson (stemming from the
resonance) are taken into account. We have found excellent
agreement between the spectra calculated in both methods, especially in the
relevant kinematical region below the charmed meson threshold. The theoretical
error to , which is dominated by the uncertainty of the -quark
mass, is estimated to be at the level.Comment: 16 pages, 4 Figures included in the text (uses epsfig.sty), 1 tabl
Performance of the CLEO III LiF-TEA Ring Imaging Cherenkov Detector in a High Energy Muon Beam
The CLEO III Ring Imaging Cherenkov detector uses LiF radiators to generate Cherenkov photons which are then detected by proportional wire chambers using a mixture of CH and TEA gases. The first two photon detector modules which were constructed, were taken to Fermilab and tested in a beam dump that provided high momentum muons. We report on results using both plane and "sawtooth" shaped radiators. Specifically, we discuss the number of photoelectrons observed per ring and the angular resolution. The particle separation ability is shown to be sufficient for the physics of CLEO III
Rare exclusive semileptonic b -> s transitions in the Standard Model
We study long-distance effects in rare exclusive semileptonic decays B -> (K,
K*) (l+ l-, nu bar{nu}) and analyze dilepton spectra and asymmetries within the
framework of the Standard Model. The form factors, describing the meson
transition amplitudes of the effective Hamiltonian are calculated within the
lattice-constrained dispersion quark model: the form factors are given by
dispersion representations through the wave functions of the initial and final
mesons, and these wave functions are chosen such that the B -> K* transition
form factors agree with the lattice results at large q**2. We calculate
branching ratios of semileptonic B -> K, K* transition modes and study the
sensitivity of observables to the long-distance contributions. The shape of the
forward-backward asymmetry and the longitudinal lepton polarization asymmetry
are found to be independent of the long-distance effects and mainly determined
by the values of the Wilson coefficients in the Standard Model.Comment: revtex, 17 pp., 5 figures with epsfig.st
Measurement of the eta-Meson Mass using psi(2S) --> eta J/psi
We measure the mass of the eta meson using psi(2S) --> eta J/psi events
acquired with the CLEO-c detector operating at the CESR e+e- collider. Using
the four decay modes eta --> gamma gamma, 3pi0, pi+pi-pi0, and pi+pi-gamma, we
find M(eta)=547.785 +- 0.017 +- 0.057 MeV, in which the first uncertainty is
statistical and the second systematic. This result has an uncertainty
comparable to the two most precise previous measurements and is consistent with
that of NA48, but is inconsistent at the level of 6.5sigma with the much
smaller mass obtained by GEM.Comment: 10 pages postscript,also available through
http://www.lns.cornell.edu/public/CLNS/2007/, Submitted to PR
Determination of the D0 -> K+pi- Relative Strong Phase Using Quantum-Correlated Measurements in e+e- -> D0 D0bar at CLEO
We exploit the quantum coherence between pair-produced D0 and D0bar in
psi(3770) decays to study charm mixing, which is characterized by the
parameters x and y, and to make a first determination of the relative strong
phase \delta between doubly Cabibbo-suppressed D0 -> K+pi- and Cabibbo-favored
D0bar -> K+pi-. We analyze a sample of 1.0 million D0D0bar pairs from 281 pb^-1
of e+e- collision data collected with the CLEO-c detector at E_cm = 3.77 GeV.
By combining CLEO-c measurements with branching fraction input and
time-integrated measurements of R_M = (x^2+y^2)/2 and R_{WS} = Gamma(D0 ->
K+pi-)/Gamma(D0bar -> K+pi-) from other experiments, we find \cos\delta = 1.03
+0.31-0.17 +- 0.06, where the uncertainties are statistical and systematic,
respectively. In addition, by further including external measurements of charm
mixing parameters, we obtain an alternate measurement of \cos\delta = 1.10 +-
0.35 +- 0.07, as well as x\sin\delta = (4.4 +2.7-1.8 +- 2.9) x 10^-3 and \delta
= 22 +11-12 +9-11 degrees.Comment: 37 pages, also available through
http://www.lns.cornell.edu/public/CLNS/2007/. Incorporated referee's comment
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