399 research outputs found
Tau Polarimetry with Inclusive Decays
The spin asymmetry parameter characterizing the angular distribution
of the total hadron momentum in the decay of a polarized tau can be calculated
rigorously using perturbative QCD and the operator product expansion.
Perturbative QCD corrections to the free quark result can be
expressed as a power series in and nonperturbative QCD
corrections can be expanded systematically in powers of . The QCD
prediction is . In the decay of a high energy tau into
hadrons, the value of the hadronic energy distribution evaluated
at the maximum hadronic energy fraction can also be calculated
rigorously from QCD.Comment: LateX, 11 pages, no figures, NUHEP-TH-93-
Study of the , , and in the radiative decays
In this paper we present an approach to study the radiative decay modes of
the into a photon and one of the tensor mesons ,
, as well as the scalar ones and .
Especially we compare predictions that emerge from a scheme where the states
appear dynamically in the solution of vector meson--vector meson scattering
amplitudes to those from a (admittedly naive) quark model. We provide evidence
that it might be possible to distinguish amongst the two scenarios, once
improved data are available.Comment: The large Nc argument improved; version published in EPJA
Hadronic effects in leptonic systems: muonium hyperfine structure and anomalous magnetic moment of muon
Contributions of hadronic effects to the muonium physics and anomalous
magnetic moment of muon are considered. Special attention is paid to
higher-order effects and the uncertainty related to the hadronic contribution
to the hyperfine structure interval in the ground state of muonium.Comment: Presented at PSAS 2002 (St. Petersburg
Possible large phase in psi(2S) -> 1-0- Decays
The strong and the electromagnetic amplitudes are analyzed on the basis of
the measurements of J/psi, psi(2S) -> 1-0- in e+e- experiments. The currently
available experimental information is revised with inclusion of the
contribution from e+e- -> gamma * -> 1-0- . The study shows that a large phase
around minus 90 degree between the strong and the electromagnetic amplitudes
could not be ruled out by the experimental data for psi(2S).Comment: 4 page
Probing unparticle theory via lepton flavor violating process at BESIII
The lepton flavor violating process serves as an
ideal place to probe the unparticle theory. Such process can only occur at loop
level in the Standard model (SM), so that should be very suppressed, by
contrast in unparticle scenario, it happens at tree level and its contribution
may be sizable for practical measurement. Moreover, the BESIII will offer the
largest database on which makes more accurate measurements possible.
Furthermore, for such purely leptonic decays background is relatively low and
signal would be cleaner. Our work carefully investigates the possibility of
observing such processes from both theoretical and experimental aspects.Comment: 11 pages, 2 figures, revised version for publicatio
Final State Interactions in
It is believed that the production rate of is almost
solely determined by final state interactions (FSI) and hence provides an ideal
place to test FSI models. Here we examine model calculations of the
contributions from s-channel resonance and t-channel exchange to
the FSI effects in . The contribution from s-channel
is sma The results from
two methods are roughly consistent with each other and can reproduce the large
rate of reasonably well$Comment: Latex, 16 pages, with 2 figure
Hybrid configuration content of heavy S-wave mesons
We use the non-relativistic expansion of QCD (NRQCD) on the lattice to study
the lowest hybrid configuration contribution to the ground state of heavy
S-wave mesons. Using lowest-order lattice NRQCD to create the heavy-quark
propagators, we form a basis of ``unperturbed'' S-wave and hybrid states. We
then apply the lowest-order coupling of the quark spin and chromomagnetic field
at an intermediate time slice to create ``mixed'' correlators between the
S-wave and hybrid states. From the resulting amplitudes, we extract the
off-diagonal element of our two-state Hamiltonian. Diagonalizing this
Hamiltonian gives us the admixture of hybrid configuration within the meson
ground state. The present effort represents a continuation of previous work:
the analysis has been extended to include lattices of varying spacings, source
operators having better overlap with the ground states, and the pseudoscalar
(along with the vector) channel. Results are presented for bottomonium
(, ) using three different sets of quenched lattices. We
also show results for charmonium (, ) from one lattice set,
although we note that the non-relativistic approximation is not expected to be
very good in this case.Comment: 9 pages, 7 figures, version to appear in Phys Rev
On Two-Body Decays of A Scalar Glueball
We study two body decays of a scalar glueball. We show that in QCD a spin-0
pure glueball (a state only with gluons) cannot decay into a pair of light
quarks if chiral symmetry holds exactly, i.e., the decay amplitude is chirally
suppressed. However, this chiral suppression does not materialize itself at the
hadron level such as in decays into and , because in
perturbative QCD the glueball couples to two (but not one) light quark pairs
that hadronize to two mesons. Using QCD factorization based on an effective
Lagrangian, we show that the difference of hadronization into and
already leads to a large difference between and , even the decay amplitude is not chirally suppressed. Moreover,
the small ratio of of
measured in experiment does not imply to be a pure glueball. With
our results it is helpful to understand the partonic contents if or is measured reliably.Comment: revised versio
Charmless Three-Body Baryonic B Decays
Motivated by recent data on B-> p pbar K decay, we study various charmless
three-body baryonic B decay modes, including Lambda pbar pi, Sigma0 pbar pi, p
pbar pi, p pbar Kbar0, in a factorization approach. These modes have rates of
order 10^{-6}. There are two mechanisms for the baryon pair production,
current-produced and transition. The behavior of decay spectra from these
baryon production mechanisms can be understood by using QCD counting rules.
Predictions on rates and decay spectra can be checked in the near future.Comment: 26 pages, 9 figures; version to appear in Phys. Rev.
J/psi->VP decays and the quark and gluon content of the eta and eta'
The - pseudoscalar mixing angle and the gluonium content
of the meson are deduced from an updated phenomenological
analysis of decays into a vector and a pseudoscalar meson. In absence
of gluonium, the value of the mixing angle in the quark-flavour basis is found
to be . In presence of gluonium, the values for the
mixing angle and the gluonic content of the wave function are
and ,
respectively. The newly reported values of by the BABAR
and BES Collaborations are crucial to get a consistent description of data.Comment: 7 pages, 1 figure, uses svjour style. Comments on the relationship
between J/psi to VP and V to Pgamma decays and on the neglected contributions
together with an asymmetric treatment of errors are include
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