4,516 research outputs found
A proposed laser measurement system for determining surface contour
Electro-optical system can scan a large /100 ft./ antenna in 30 seconds. Comparison of the reflected signal with a reference signal from a Pockel-cell modulator driver yields a signal that can be correlated with the distance covered by the laser. A scanning arrangement then enables contour measurement
Second Order Power Corrections in the Heavy Quark Effective Theory I. Formalism and Meson Form Factors
In the heavy quark effective theory, hadronic matrix elements of currents
between two hadrons containing a heavy quark are expanded in inverse powers of
the heavy quark masses, with coefficients that are functions of the kinematic
variable . For the ground state pseudoscalar and vector mesons, this
expansion is constructed at order . A minimal set of universal form
factors is defined in terms of matrix elements of higher dimension operators in
the effective theory. The zero recoil normalization conditions following from
vector current conservation are derived. Several phenomenological applications
of the general results are discussed in detail. It is argued that at zero
recoil the semileptonic decay rates for and receive only small second order corrections, which are unlikely
to exceed the level of a few percent. This supports the usefulness of the heavy
quark expansion for a reliable determination of .Comment: (34 pages, REVTEX, two postscript figures available upon request),
SLAC-PUB-589
Determinations of |V_ub| and |V_cb| from measurements of B -> X_u,c\ell\nu differential decay rates
Methods are described in the framework of light-cone expansion which allow
one to determine the Cabibbo-Kobayashi-Maskawa matrix elements |V_ub| and
|V_cb| from measurements of the differential decay rates as a function of the
scaling variables in the inclusive semileptonic decays of B mesons. By these
model-independent methods the dominant hadronic uncertainties can be avoided
and the B -> X_u\ell\nu decay can be very efficiently differentiated from the B
-> X_c\ell\nu decay, which may lead to precise determinations of |V_ub| and
|V_cb|.Comment: 11 pages, 2 figures, version as published in Mod. Phys. Lett. A, more
discussion, references added, title chang
Note on Tests of the Factorization Hypothesis and the Determination of Meson Decay Constants
We discuss various tests of the factorization hypothesis making use of the
close relationship between semi-leptonic and factorized nonleptonic decay
amplitudes. It is pointed out that factorization leads to truely
model-independent predictions for the ratio of nonleptonic to semi-leptonic
decay rates, if in the nonleptonic decay a spin one meson of arbitrary mass or
a pion take the place of the lepton pair. Where the decay constants of those
mesons are known, these predictions represent ideal tests of the factorization
hypothesis. In other cases they may be used to extract the decay constants.
Currently available data on the decays are shown to be in excellent agreement with
the factorization results. A weighted average of the four independent values
for the QCD coefficient extracted from the data gives
suggesting that it may be equal to the Wilson coefficient evaluated
at the scale .Comment: (9 pages, ReVTeX, no figures), HD-THEP-92-3
Simply Modeling Meson HQET
A simple relativistic model of heavy-quark-light-quark mesons is proposed. In
an expansion in inverse powers of the heavy quark mass we find that all zeroth
and first order heavy quark symmetry relations are satisfied. The main results
are: - the difference between the meson mass and the heavy quark mass plays a
significant role even at zeroth order; - the slope of the Isgur-Wise function
at the zero recoil point is typically less than ; - the first order
correction to the pseudoscalar decay constant is large and negative; - the four
universal functions describing the first order corrections to the semileptonic
decay form factors are small; - these latter corrections are quite insensitive
to the choice of model parameters, and in particular to the effects of
hyperfine mass splitting.Comment: 17 pages, LaTeX, 3 LaTeX figures in separate file, UTPT-92-16. This
is the version published long ago but not previously archive
Two-loop corrections to the Isgur-Wise function in QCD sum rules
We complete the QCD sum rule analysis of the Isgur Wise form factor
at next-to-leading order in renormalization-group improved
perturbation theory. To this end, the exact result for the two-loop corrections
to the perturbative contribution is derived using the heavy quark effective
theory. Several techniques for the evaluation of two-loop integrals involving
two different types of heavy quark propagators are discussed in detail, among
them the methods of integration by parts and differential equations. The
order- corrections to the Isgur-Wise function turn out to be small
and well under control. At large recoil, they tend to decrease the form factor
by .Comment: 24 pages (REVTEX), 2 figures available upon request, SLAC-PUB-599
Bounds on R-parity violating supersymmetric couplings from leptonic and semi-leptonic meson decays
We present a comprehensive update of the bounds on R-Parity violating
supersymmetric couplings from lepton-flavour- and lepton-number-violating decay
processes. We consider tau and mu decays as well as leptonic and semi-leptonic
decays of mesons. We present several new bounds resulting from tau, eta and
Kaon decays and correct some results in the literature concerning B-meson
decays.Comment: 30 pages; changed title, updated some bounds from the literature from
different references, added reference
Identification of placental transforming growth factor-beta and bikunin metabolites as contaminants of pharmaceutical human chorionic gonadotrophin preparations by proteomic techniques
This paper is the first to identify the novel bio-molecules found in pregnancy urine and commonly contaminate clinical grade hCG preparation extracted from urine reported to have anti-HIV/HIV Kaposis . Professor Iles was the Principal Investigator
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