66 research outputs found
The open-charm radiative and pionic decays of molecular charmonium Y(4274)
In this work, we investigate the decay widths and the line shapes of the
open-charm radiative and pionic decays of Y(4274) with the
molecular charmonium assignment. Our calculation
indicates that the decay widths of and
can reach up to 0.05 keV and 0.75 keV,
respectively. In addition, the result of the line shape of the photon spectrum
of shows that there exists a very sharp
peak near the large end point of photon energy. The line shape of the pion
spectrum of is similar to that of the pion
spectrum of , where we also find a very
sharp peak near the large end point of pion energy. According to our
calculation, we suggest further experiments to carry out the search for the
open-charm radiative and pionic decays of Y(4274).Comment: 7 pages, 6 figures, 1 table. Published versio
Phenomenology of V_ub from Ratios of Inclusive B Decay Rates
We explore the theoretical feasibility of extracting V_ub from two ratios
built from B meson inclusive partial decays,
R_1 = Gamma(b-> u cbar s)/3Gamma(b -> c l nu), and
R_2 = [Gamma(b -> c X) - Gamma(b -> cbar X)]/Gamma(b -> c ubar d).
We discuss contributions to these quantities from perturbative and
nonperturbative physics, and show that they can be computed with overall
uncertainties at the level of 10%.Comment: 19 pages, 8 embedded EPS figures, uses REVTe
Effective Field Theories
These lectures introduce some of the basic notions of effective field
theories, as used in particle physics. The topics discussed are the and weak interactions, and chiral perturbation theory as
applied to mesons, baryons, and hadrons containing heavy quarks.Comment: Lectures on Effective Field Theories at the Lake Louise Winter
Institute, February 1995. 42 pages, 16 figures; extended version in
hep-ph/960622
Tests for a Strong Electroweak Sector at Future e^+e^- High Energy Colliders
The study of the scattering at high energy of the gauge bosons W and Z, in
particular longitudinally polarized W and Z, can clarify the mechanism of
spontaneous symmetry breaking in the Standard Model of the electroweak
interactions. Different models of strong electroweak sector, based on the
effective lagrangian approach are briefly reviewed. They include models with no
resonance, with scalar resonance, additional vector and axial-vector
resonances. The effective Lagrangians are derived from the chiral symmetry of
the symmetry breaking sector. Limits on these models from existing
measurements, mainly LEP and Tevatron, are considered. We study also direct and
indirect effects of the new interactions at high energy future e^+e^- linear
colliders, through WW scattering and the direct production of these new vector
gauge bosons.Comment: 74 pages, 19 figures and 4 tables included, Latex, uses epsf, to
appear in La Rivista del Nuovo Cimento, some minor change
Leptonic and Semileptonic Decays of Charm and Bottom Hadrons
We review the experimental measurements and theoretical descriptions of
leptonic and semileptonic decays of particles containing a single heavy quark,
either charm or bottom. Measurements of bottom semileptonic decays are used to
determine the magnitudes of two fundamental parameters of the standard model,
the Cabibbo-Kobayashi-Maskawa matrix elements and . These
parameters are connected with the physics of quark flavor and mass, and they
have important implications for the breakdown of CP symmetry. To extract
precise values of and from measurements, however,
requires a good understanding of the decay dynamics. Measurements of both charm
and bottom decay distributions provide information on the interactions
governing these processes. The underlying weak transition in each case is
relatively simple, but the strong interactions that bind the quarks into
hadrons introduce complications. We also discuss new theoretical approaches,
especially heavy-quark effective theory and lattice QCD, which are providing
insights and predictions now being tested by experiment. An international
effort at many laboratories will rapidly advance knowledge of this physics
during the next decade.Comment: This review article will be published in Reviews of Modern Physics in
the fall, 1995. This file contains only the abstract and the table of
contents. The full 168-page document including 47 figures is available at
http://charm.physics.ucsb.edu/papers/slrevtex.p
Experimental Tests of Factorization in Charmless Non-Leptonic Two-Body B Decays
Using a theoretical framework based on the next-to-leading order QCD-improved
effective Hamiltonian and a factorization Ansatz for the hadronic matrix
elements of the four-quark operators, we reassess branching fractions in
two-body non-leptonic decays , involving the lowest lying
light pseudoscalar and vector mesons in the standard model. Using
the sensitivity of the decay rates on the effective number of colors, , as
a criterion of theoretical predictivity, we classify all the current-current
(tree) and penguin transitions in five different classes. The recently measured
charmless two-body decays and charge conjugates) are
dominated by the -stable QCD penguins (class-IV transitions) and their
estimates are consistent with data. The measured charmless and transition ,
on the other hand, belong to the penguin (class-V) and tree (class-III)
transitions. The class-V penguin transitions are in general more difficult to
predict. We propose a number of tests of the factorization framework in terms
of the ratios of branching ratios for some selected decays
involving light hadrons and , which depend only moderately on the
form factors. We also propose a set of measurements to determine the effective
coefficients of the current-current and QCD penguin operators. The potential
impact of decays on the CKM phenomenology is emphasized by
analyzing a number of decay rates in the factorization framework.Comment: 64 pages (LaTex) including 13 figures, requires epsfig.sty; submitted
to Phys. Rev.
Rare Charm Decays in the Standard Model and Beyond
We perform a comprehensive study of a number of rare charm decays,
incorporating the first evaluation of the QCD corrections to the short distance
contributions, as well as examining the long range effects. For processes
mediated by the transitions, we show that sensitivity to
short distance physics exists in kinematic regions away from the vector meson
resonances that dominate the total rate. In particular, we find that
and are sensitive to non-universal
soft-breaking effects in the Minimal Supersymmetric Standard Model with
R-parity conservation. We separately study the sensitivity of these modes to
R-parity violating effects and derive new bounds on R-parity violating
couplings. We also obtain predictions for these decays within extensions of the
Standard Model, including extensions of the Higgs, gauge and fermion sectors,
as well as models of dynamical electroweak symmetry breaking.Comment: 45 pages, typos fixed, discussions adde
Virtual Compton Scattering and Neutral Pion Electroproduction in the Resonance Region up to the Deep Inelastic Region at Backward Angles
We have made the first measurements of the virtual Compton scattering (VCS)
process via the H exclusive reaction in the nucleon resonance
region, at backward angles. Results are presented for the -dependence at
fixed GeV, and for the -dependence at fixed near 1.5 GeV.
The VCS data show resonant structures in the first and second resonance
regions. The observed -dependence is smooth. The measured ratio of
H to H cross sections emphasizes the different
sensitivity of these two reactions to the various nucleon resonances. Finally,
when compared to Real Compton Scattering (RCS) at high energy and large angles,
our VCS data at the highest (1.8-1.9 GeV) show a striking -
independence, which may suggest a transition to a perturbative scattering
mechanism at the quark level.Comment: 20 pages, 8 figures. To appear in Phys.Rev.
The Renormalization Group with Exact beta-Functions
The perturbative -function is known exactly in a number of
supersymmetric theories and in the 't Hooft renormalization scheme in the
model. It is shown how this allows one to compute the effective
action exactly for certain background field configurations and to relate bare
and renormalized couplings. The relationship between the MS and SUSY
subtraction schemes in super Yang-Mills theory is discussed
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
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