1,328 research outputs found
Review of Heavy Quark Physics - theory
Recent progress in the theory of B-meson decays is reviewed with emphasis on
the aspects related to the B-factory data.Comment: 15 pages; Invited Plenary Talk at the 32nd International Conference
on High Energy Physics (ICHEP'04), Beijing, China, Aug. 16-22, 200
Radiative Neutron Capture on Carbon-14 in Effective Field Theory
The cross section for radiative capture of neutron on carbon-14 is calculated
using the model-independent formalism of halo effective field theory. The
dominant contribution from E1 transition is considered, and the cross section
is expressed in terms of elastic scattering parameters of the effective range
expansion. Contributions from both resonant and non-resonant interaction are
calculated. Significant interference between these leads to a capture
contribution that deviates from simple Breit-Wigner resonance form.Comment: 14 pages, 6 figure
Angular Distribution and Polarization of Photons in the Inclusive Decay
We study the angular distribution of photons produced in the inclusive decay
of a polarized , , using the technique of
Heavy Quark Effective Theory. Finite non-perturbative corrections are obtained
relative to the free quark decay . These corrections affect
significantly the intensity and polarization of photons emitted at small angles
relative to the spin direction.Comment: 10 pages, LaTeX, uses epsf, 2 figures appended as uuencoded,
compressed eps tar-file
Renormalons in Effective Field Theories
We investigate the high-order behavior of perturbative matching conditions in
effective field theories. These series are typically badly divergent, and are
not Borel summable due to infrared and ultraviolet renormalons which introduce
ambiguities in defining the sum of the series. We argue that, when treated
consistently, there is no physical significance to these ambiguities. Although
nonperturbative matrix elements and matching conditions are in general
ambiguous, the ambiguity in any physical observable is always higher order in
than the theory has been defined. We discuss the implications for the
recently noticed infrared renormalon in the pole mass of a heavy quark. We show
that a ratio of form factors in exclusive decays (which is related
to the pole mass) is free from renormalon ambiguities regardless of the mass
used as the expansion parameter of HQET. The renormalon ambiguities also cancel
in inclusive heavy hadron decays. Finally, we demonstrate the cancellation of
renormalons in a four-Fermi effective theory obtained by integrating out a
heavy colored scalar.Comment: Minor changes mad
Radiative Decay Using Heavy Quark and Chiral Symmetry
The implications of chiral symmetry and heavy quark
symmetry for the radiative decays , ,
and are discussed. Particular attention is paid to
violating contributions of order . Experimental data on these
radiative decays provide constraints on the coupling.Comment: 9 pages plus 3 pages of figures in POSTSCRIPT file appended to TeX
file (uses harvmac.tex and tables.tex), UCSD/PTH 92-31, CALT-68-1816,
EFI-92-45, CERN-TH.6650/9
The 1/N Expansion in Noncommutative Quantum Mechanics
We study the 1/N expansion in noncommutative quantum mechanics for the
anharmonic and Coulombian potentials. The expansion for the anharmonic
oscillator presented good convergence properties, but for the Coulombian
potential, we found a divergent large N expansion when using the usual
noncommutative generalization of the potential. We proposed a modified version
of the noncommutative Coulombian potential which provides a well-behaved 1/N
expansion.Comment: v2: resided version, to appear in PRD, 18 pages, 4 figure
Resolving the Large-N Nuclear Potential Puzzle
The large nuclear potential puzzle arose because three- and
higher-meson exchange contributions to the nucleon-nucleon potential did not
automatically yield cancellations that make these contributions consistent with
the general large scaling rules for the potential. Here it is proposed
that the resolution to this puzzle is that the scaling rules only apply for
energy-independent potentials while all of the cases with apparent
inconsistencies were for energy-dependent potentials. It is shown explicitly
how energy-dependent potentials can have radically different large N behavior
than an equivalent energy-independent one. One class of three-meson graphs is
computed in which the contribution to the energy-independent potential is
consistent with the general large N rules even though the energy-dependent
potential is not.Comment: Corrections to the toy mode
Strong Decays of Excited Heavy Mesons In Chiral Perturbation Theory
We construct an effective Lagrangian describing the interaction of soft pions
and kaons with mesons containing a heavy quark and light degrees of freedom in
an orbital wave. The formalism is easily extended to heavy mesons and
baryons in arbitrary excited states. We calculate the leading contributions to
the strong decays \dtwo\to\d\pi, \dtwo\to\dstar\pi and \done\to\dstar\pi.
We confirm the relations between the rates previously obtained by Isgur and
Wise using heavy quark symmetry, and find that the absolute widths are
consistent with na\"\i ve power counting. We also estimate the branching ratios
for the two pion decays \dtwo\to\dstar\pi\pi, \done\to\dstar\pi\pi and
\done\to\d\pi\pi, which are dominated by pole graphs. Our predictions depend
on the masses and widths of the as yet unseen scalar-pseudovector -wave
doublet. Heavy quark spin symmetry predicts \Gamma(\dtwo\to\dstar\pi\pi):
\Gamma(\done\to\dstar\pi\pi):\Gamma(\done\to\d\pi\pi)=3:1:2, but this relation
is badly violated in practice because effects arising purely from
kinematics are large.Comment: (14 pages, 2 figures available from the authors, harvmac.tex
required), SLAC-PUB-5812, UCSD/PTH 92-1
\Lambda_b \to \Lambda_c P(V) Nonleptonic Weak Decays
The two-body nonleptonic weak decays of \Lambda_b \to \Lambda_c P(V) (P and V
represent pseudoscalar and vector mesons respectively) are analyzed in two
models, one is the Bethe-Salpeter (B-S) model and the other is the hadronic
wave function model. The calculations are carried out in the factorization
approach. The obtained results are compared with other model calculations.Comment: 18 pages, Late
New meson spectroscopy with open charm and beauty
All the available experimental information on open charm and beauty mesons is
used to classify the observed states in heavy quark doublets. The masses of
some of the still unobserved states are predicted, in particular in the beauty
sector.
Adopting an effective Lagrangian approach based on the heavy quark and chiral
symmetry, individual decay rates and ratios of branching fractions are
computed, with results useful to assign the quantum numbers to recently
observed charmed states which still need to be properly classified.
Implications and predictions for the corresponding beauty mesons are provided.
The experimental results are already copious, and are expected to grow up
thanks to the experiments at the LHC and to the future high-luminosity flavour
and facilities.Comment: RevTex, 15 pages, 1 figure. Corrected Equations (8) and (9
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