38,029 research outputs found
Model-independent Study on Magnetic Dipole Transition in Heavy Quarkonium
Some new results on magnetic dipole (M1) transitions in heavy quarkonium from
nonrelativistic effective field theories of QCD are briefly reported. This
model-independent approach not only facilitates a systematic and lucid way to
investigate the relativistic corrections, it also clarifies some inconsistent
treatment in previous potential model approach. The impact of our formalism on
J/Psi -> eta_c gamma, Upsilon(Upsilon') -> eta_b gamma and h_c -> chi_{c0}
gamma are discussed.Comment: 7 pages and 3 figures. Talk presented at QCD@Work 2005, Conversano,
June 16-20, 2005 and QCD05, Montpellier, July 4-8, 200
Which hadronic decay modes are good for searching: double or something else?
It has been controversial whether can be discovered in Tevatron Run
2 through the decay followed by . We clear this controversy by an explicit calculation which
predicts to be of order . It is
concluded that observing eta_b through this decay mode in Tevatron Run 2 is
rather unrealistic. The eta_b may be observed in the forthcoming LHC
experiments through the 4-lepton channel, if the background events can be
significantly reduced by imposing some kinematical cuts. By some rough but
plausible considerations, we find that the analogous decay processes eta_b to
VV, D^*\bar{D}^* also have very suppressed branching ratios, nevertheless it
may be worth looking for \eta_b at LHC and Super B factory through the decay
modes \eta_b \to K_S K^{\pm}\pi^{\mp}, D^*\bar{D}.Comment: v2; 28 pages, 2 figures. References added, presentation improved.
Discussion on possible nonperturbative mechanism for eta_b->VV added,
analysis for eta_b->VP updated by incoprating the U-spin violation effec
"Hard-scattering" approach to very hindered magnetic-dipole transitions in quarkonium
For a class of hindered magnetic dipole () transition processes, such as
(the discovery channel of the meson),
the emitted photon is rather energetic so that the traditional approaches based
on multipole expansion may be invalidated. We propose that a "hard-scattering"
picture, somewhat analogous to the pion electromagnetic form factor at large
momentum transfer, may be more plausible to describe such types of transition
processes. We work out a simple factorization formula at lowest order in the
strong coupling constant, which involves convolution of the Schr\"odinger wave
functions of quarkonia with a perturbatively calculable part induced by
exchange of one semihard gluon between quark and antiquark. This formula,
without any freely adjustable parameters, is found to agree with the measured
rate of rather well, and can also reasonably
account for other recently measured hindered transition rates. The
branching fractions of are also
predicted.Comment: v3; 5 pages, 1 figure and 1 table; title changed, presentation
improve
A local construction of the Smith normal form of a matrix polynomial
We present an algorithm for computing a Smith form with multipliers of a
regular matrix polynomial over a field. This algorithm differs from previous
ones in that it computes a local Smith form for each irreducible factor in the
determinant separately and then combines them into a global Smith form, whereas
other algorithms apply a sequence of unimodular row and column operations to
the original matrix. The performance of the algorithm in exact arithmetic is
reported for several test cases.Comment: 26 pages, 6 figures; introduction expanded, 10 references added, two
additional tests performe
- …