46 research outputs found
The order and corrections to the decay width of the neutral Higgs boson to the pair
We present the analytical expressions for the contributions of the order
and corrections to the
decay width of the Standard Model Higgs boson into the -pair. The
numerical value of the mixed QED and QCD correction of order
is comparable with the previously calculated
terms in the perturbative series for .Comment: LaTeX 5 pages, accepted for publication in Pisma Zh. Eksp. Teor. Fiz.
v 66, N5 (1997
Neutron-antineutron Oscillations in the Trapping Box
We have reexamined the problem of oscillations for ultra-cold
neutrons (UCN) confined within a trap. We have shown that the growth of the
component with time is to a decent accuracy given by where is the mixing parameter,
sec in the neutron propagation time between subsequent collisions
with the trap walls. Possible corrections to this law and open questions are
discussed.Comment: 11 pages, LaTeX2
The running mass at low scalefrom the heavy-light meson decay constants
It is shown that a 25(20)% difference between the decay constants
and occurs due to large differences in the pole
masses of the and quarks. The values , recently observed in the CLEO experiment, and
, obtained in unquenched lattice QCD, can be
reached only if the running mass at low scale is GeV) MeV. Our results follow from the analytical expression for the
pseudoscalar decay constant based on the path-integral
representation of the meson Green's function.Comment: 6 pages, no figures; revtex
Gauge-Independent W-Boson Partial Decay Widths
We calculate the partial decay widths of the W boson at one loop in the
standard model using the on-shell renormalization scheme endowed with a
gauge-independent definition of the Cabibbo-Kobayashi-Maskawa (CKM) mixing
matrix. We work in gauge and explicitly verify that the final
expressions are independent of the gauge parameters. Furthermore, we establish
the relationship between the on-shell and definitions of
the CKM matrix, both in its generic form and in the Wolfenstein
parameterization. As a by-product of our analysis, we recover the beta function
of the CKM matrix.Comment: 15 pages; reference added; input parameters updated according to 2000
PDG report; accepted for publication in Phys. Rev.
Limits on \boldmath n {\bar n} oscillations from nuclear stability
The relationship between the lower limit on the nuclear stability lifetime as
derived from the non disappearance of `stable` nuclei
( yr), and the lower limit thus implied on
the oscillation time of a possibly underlying
neutron-antineutron oscillation process, is clarified by studying the time
evolution of the nuclear decay within a simple model which respects unitarity.
The order-of-magnitude result sec, where is a typical
nuclear annihilation width, agrees as expected with the limit on established by several detailed nuclear physics calculations, but sharply
disagreeing by 15 orders of magnitude with a claim published recently in Phys.
Rev. CRAP.Comment: 8 pages; this PRC version (accepted for publication, November 4 1999)
differs from the original version only by a few minor editorial change
A first estimate of triply heavy baryon masses from the pNRQCD perturbative static potential
Within pNRQCD we compute the masses of spin-averaged triply heavy baryons
using the now-available NNLO pNRQCD potentials and three-body variational
approach. We focus in particular on the role of the purely three-body
interaction in perturbation theory. This we find to be reasonably small and of
the order 25 MeV Our prediction for the Omega_ccc baryon mass is 4900(250) in
keeping with other approaches. We propose to search for this hitherto
unobserved state at B factories by examining the end point of the recoil
spectrum against triple charm.Comment: 18 figures, 21 page
Leptonic constants of heavy quarkonia in potential approach of NRQCD
We consider a general scheme for calculating the leptonic constant of heavy
quarkonium QQ-bar in the framework of nonrelativistic quantum chromodynamics,
NRQCD, operating as the effective theory of nonrelativistic heavy quarks. We
explore the approach of static potential in QCD, which takes into account both
the evolution of effective charge in the three-loop approximation and the
linearly raising potential term, which provides the quark confinement. The
leptonic constants of bb-bar and cc-bar systems are evaluated by making use of
two-loop anomalous dimension for the current of nonrelativistic quarks, where
the factor for the normalization of matrix element is introduced in order to
preserve the renormalization group invariance of estimates.Comment: 18 pages, 6 eps-figures, discussion and references added, vNRQCD
analysis considere
Dualities for Loop Amplitudes of N=6 Chern-Simons Matter Theory
In this paper we study the one- and two-loop corrections to the four-point
amplitude of N=6 Chern-Simons matter theory. Using generalized unitarity
methods we express the one- and two-loop amplitudes in terms of dual-conformal
integrals. Explicit integration by using dimensional reduction gives vanishing
one-loop result as expected, while the two-loop result is non-vanishing and
matches with the Wilson loop computation. Furthermore, the two-loop correction
takes the same form as the one-loop correction to the four-point amplitude of
N=4 super Yang-Mills. We discuss possible higher loop extensions of this
correspondence between the two theories. As a side result, we extend the method
of dimensional reduction for three dimensions to five dimensions where dual
conformal symmetry is most manifest, demonstrating significant simplification
to the computation of integrals.Comment: 32 pages and 6 figures. v2: minus sign corrections, ref updated v3:
Published versio
Can the Mechanism for Hybrid Decays be Detected?
Two mechanisms for the () hybrid meson decay processes
are investigated. These mechanisms are applied to
and decays to
illustrate the validity of the decay mechanisms and to obtain independent
information on the coupling of to quark and gluonic operators.
From this information, we find that
is substantially different
in the two decay mechanisms, and hence future experimental measurements of this
ratio will provide valuable information for substantiating the hybrid nature of
these states and for determining the mechanism for these hybrid decays.Comment: 5 pages, revtex, 1 eps figure embedded in manuscript. Analysis and
references extended in v
Small x behavior of parton distributions. A study of higher twist effects
Higher twist corrections to the structure function F_2 at small x are studied
for the case of a flat initial condition for the twist-two QCD evolution in the
next-to-leading order approximation. We present an analytical parameterization
of the contributions from the twist-two and higher twist operators of the
Wilson operator product expansion. Higher twist terms are evaluated using two
different approaches, one motivated by BFKL and the other motivated by the
renormalon formalism. The results of the latter approach are in very good
agreement with deep inelastic scattering data from HERA.Comment: 46 pages, 9 figures, typeset using REVTeX. Misprints corrected, new
results, discussions, references and acknowledgements added, 2 pictures
replaced. The conclusions remain unchange