223 research outputs found
Search for isotensor exotic meson and twist 4 contribution to
We present a theoretical estimate for the cross-section of exclusive
and -meson production in two photon collisions
when one of the initial photons is highly virtual. We focus on the discussion
of the twist 4 contributions which are related to the production of an exotic
isospin 2 resonance of two mesons. Our analysis shows that the recent
experimental data obtained by the L3 Collaboration at LEP can be understood as
a signal for the existence of an exotic isotensor resonance with a mass around
.Comment: 8 pages, 5 figure
Do L3 data indicate the existence of an isotensor meson ?
The QCD analysis of the hard exclusive production of and
mesons in two photon collisions shows that the recent
experimental data obtained by the L3 Collaboration at LEP can be understood as
a signal for the existence of an exotic isotensor resonance with a mass around
.Comment: 3 pages, 2 figures; Presented at Photon2005, Warsaw, Polan
On the gauge invariance of the DVCS amplitude
We analyze in detail the problem of gauge invariance of the deeply vitual
Compton scattering (DVCS) amplitude. Using twist 3 one-gluon exchange diagram
contributions and the QCD equations of motion, we derive the general gauge
invariant expression of the DVCS amplitude on a (pseudo)scalar particle (pion,
). Similarly to the case of deep inelastic scattering, the amplitude does
not depend on the twist-3 quark-gluon correlations at the Born level. The
contribution of the derived amplitude to the single-spin asymmetry with
longitudinally polarized lepton is calculated.Comment: 5 pages, 1 figure, LaTeX; Types fixed, formula for asymmetry
completed, one reference adde
Strong and radiative decays of the Ds0*(2317) meson in the DK-molecule picture
We consider a possible interpretation of the new charm-strange meson
Ds0*(2317) as a hadronic molecule - a bound state of D and K mesons. Using an
effective Lagrangian approach we calculate the strong Ds0* to Ds pi0 and
radiative Ds0* to Ds* gamma decays. A new impact related to the DK molecular
structure of the Ds0*(2317) meson is that the presence of u(d) quarks in the D
and K mesons gives rise to a direct strong isospin-violating transition Ds0* to
Ds pi0 in addition to the decay mechanism induced by eta-pi0 mixing considered
previously. We show that the direct transition dominates over the eta-pi0
mixing transition in the Ds0* to Ds pi0 decay. Our results for the partial
decay widths are consistent with previous calculations.Comment: 22 pages, 4 figures, accepted for publication in Phys. Rev.
On BLM scale fixing in exclusive processes
We discuss the BLM scale fixing procedure in exclusive electroproduction
processes in the Bjorken regime. We show that in the case of vector meson
production the usual way to aplly the BLM method fails due to singularities
present in equations fixing the BLM scale. We argue that the BLM scale should
be extracted from the squared amplitudes which are directly related to
observables.Comment: accepted for the publication in Eur.Phys.J.
Dispersion relations and subtractions in hard exclusive processes
We study analytical properties of the hard exclusive processes amplitudes. We
found that QCD factorization for deeply virtual Compton scattering and hard
exclusive vector meson production results in the subtracted dispersion relation
with the subtraction constant determined by the Polyakov-Weiss -term. The
relation of this constant to the fixed pole contribution found by Brodsky,
Close and Gunion and defined by parton distributions is proved, while its
manifestation is spoiled by the small divergence. The continuation to the
real photons limit is considered and the numerical correspondence between
lattice simulations of -term and low energy Thomson amplitude is found.Comment: 4 pages, journal versio
Hard Electroproduction of Hybrid Mesons
We estimate the sizeable cross section for deep exclusive electroproduction
of an exotic hybrid meson in the Bjorken regime. The production
amplitude scales like the one for usual meson electroproduction, {\it i.e.} as
. This is due to the non-vanishing leading twist distribution amplitude
for the hybrid meson, which may be normalized thanks to its relation to the
energy momentum tensor and to the QCD sum rules technique. The hard amplitude
is considered up to next--to--leading order in and we explore the
consequences of fixing the renormalization scale ambiguity through the BLM
procedure.Comment: e-version for "Advanced Studies Institute Conference on Symmetries
and Spin (SPIN-Praha-2004)", Prague, Czech Republic, 5-10 Jul 200
Recent and future experimental evidences for exotic mesons in hard reactions
The QCD analysis of the recent experimental data (L3@LEP) of the hard
exclusive production in two photon collisions shows that these data
can be understood as a signal for the existence of an exotic isotensor
resonance with a mass around . We also argue that hard exclusive
reactions are a powerful tool for an experimental study of exotic hybrid mesons
with .Comment: Talk given at XXXIII International Conference on High Energy Physics,
July 26 - August 2, Moscow, Russi
Probing the partonic structure of exotic particles in hard electroproduction
We argue that the electroproduction of exotic particles is a useful tool for
study of their partonic structure. In the case of hybrid mesons, the magnitude
of their cross sections shows that they are accessible for measurements in
existing electroproduction experiments.Comment: 10 pages Latex, 5 figs., talk at Three Days of Hadronic Physics
(HLPR04): Joint Meeting Heidelberg-Liege-Paris-Rostock, Liege, Belgium, 16-18
Dec 200
Hard production of exotic hybrid mesons
Exotic hybrid mesons H, with quantum numbers J^{PC}= 1^{- +} may be copiously
produced in the hard exclusive processes gamma^*(Q^2) gamma -> H and
gamma^*(Q^2) P(p) -> H P(p') because they have a leading twist distribution
amplitude with a sizable coupling constant f_H, which may be estimated through
QCD sum rules. The reaction rates scale in the same way as the corresponding
rates for usual mesons.Comment: 4 pages Latex, talk at XIth International Conference on Elastic and
Diffractive Scattering Chateau de Blois, France, May 15 - 20, 200
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