44 research outputs found
P Wave Meson Spectrum in a Relativistic Model with Instanton Induced Interaction
On the basis of the phenomenological relativistic harmonic models for quarks
we have obtained the masses of P wave mesons. The full Hamiltonian used in the
investigation has Lorentz scalar + vector confinement potential, along with one
gluon exchange potential (OGEP) and the instanton-induced quark-antiquark
interaction (III). A good agreement is obtained with the experimental masses.
The respective role of III and OGEP for the determination of the meson masses
is discussed.Comment: Corrected typo
Ultra-High Energy Cosmic Rays and Stable H-dibaryon
It is shown that an instanton induced interaction between quarks produces a
very deeply bound H-dibaryon with mass below 2M_N, M_H=1718 MeV. Therefore the
H-dibaryon is predicted to be a stable particle. The reaction of
photodisintegration of H-dibaryon to in during of its penetration
into cosmic microwave background will result in a new possible cut-off in the
cosmic-ray spectrum. This provides an explanation of ultra-high energy cosmic
ray events observed above the GZK cut-off as a result of the strong interaction
of high energy H-dibaryons from cosmic rays with nuclei in Earth's atmosphere.Comment: 5 pages, Late
Anomalous f_1 exchange in vector meson photoproduction asymmetries
We perform an analysis of the elastic production of vector mesons with
polarized photon beams at high energy in order to investigate the validity of a
recently proposed dynamical mechanism based on the dominance of the f_1
trajectory at large momentum transfer. The density matrix characterizing the
angular distributions of the vector meson decays is calculated within an
exchange model which includes the Pomeron and the f_1. The asymmetries of these
decays turn out to be very useful to disentangle the role of these exchanges
since their effect depends crucially on their quantum numbers which are
different. The observables analyzed are accessible with present experimental
facilities.Comment: 10 pages, REVTeX, 4 figures, some figures are corrected, conclusions
unchange
Closed-flavor pi + J/psi and pi + Upsilon Cross Sections at Low Energies from Dipion Decays
The scale of low energy c-cbar and b-bbar cross sections on light hadrons is
of great importance to searches for the quark gluon plasma using the
heavy-quarkonium suppression signature. Unfortunately, little is known about
these near-threshold cross sections at present, and recent theoretical
estimates span many orders of magnitude. Here we use experimental data on the
four observed closed-flavor heavy quarkonium hadronic decays psi' -> pi pi
J/psi, Upsilon' -> pi pi Upsilon, Upsilon'' -> pi pi Upsilon and Upsilon'' ->
pi pi Upsilon', combined with simple models of the transition amplitudes, to
estimate the pion scattering cross sections of c-cbar and b-bbar mesons near
threshold. Specifically we consider the closed-flavor reactions pi J/psi -> pi
psi', pi Upsilon -> pi Upsilon', pi Upsilon -> pi Upsilon'' and pi Upsilon' ->
pi Upsilon'' and their time-reversed analogues. Our results may be useful in
constraining theoretical models of the strong interactions of heavy quarkonia,
and can be systematically improved through future detailed studies of dipion
decays, notably psi' -> pi pi J/psi and Upsilon'' -> pi pi Upsilon.Comment: 6 pages, 6 figure
A quark model analysis of the charge symmetry breaking in nuclear force
In order to investigate the charge symmetry breaking (CSB) in the short range
part of the nuclear force, we calculate the difference of the masses of the
neutron and the proton, , the difference of the scattering
lengths of the p-p and n-n scatterings, , and the difference of the
analyzing power of the proton and the neutron in the n-p scattering, , by a quark model. In the present model the sources of CSB are the
mass difference of the up and down quarks and the electromagnetic interaction.
We investigate how much each of them contributes to , and . It is found that the contribution of CSB of the
short range part in the nuclear force is large enough to explain the observed
, while is rather underestimated.Comment: 26 pages,6 figure
Mechanism of single-spin asymmetries generation in the inclusive hadron processes
We discuss a nonperturbative mechanism for generation of the single-spin
asymmetries in hadron interactions. It is based on the chiral quark model
combined with unitarity and impact parameter picture and provides explanation
for the experimental regularities observed under the measurements of the spin
asymmetries.Comment: 20 pages, 7 figure
Diffractive production of dijets by double Pomeron exchange processes
A phenomenological description of diffractive dijet hadroproduction via
double Pomeron exchange is presented. This description is based on a modified
version of the Ingelman-Schlein model which includes the evolution of the
Pomeron structure function and corrections regarding rapidity gap suppression
effects. The same quark-dominant Pomeron structure function employed in a
previous report to describe diffractive dijet and W production via single
Pomeron processes is shown here to yield results consistent with the available
data for double Pomeron processes as well.Comment: 4 pages, REVTEX4.
Instantons and Polarized Structure Functions
The contribution of the quark-quark and quark-gluon interaction induced by
instantons to the valence quark and proton spin-dependent structure functions
is estimated within the instanton liquid model for QCD vacuum. It
is shown, that this interaction leads to a rather large violation of the
Ellis-Jaffe sum rule.Comment: 9 pages, Latex, 4 figures. To appear in Proc. Workshop "Deep
Inelastic Scattering off Polarized Targets: Theory Meets Experiment",
September 1997, DESY-Zeuthe
Near-Maximal Mixing of Scalar Gluonium and Quark Mesons: A Gaussian Sum-Rule Analysis
Gaussian QCD sum-rules are ideally suited to the study of mixed states of
gluonium (glueballs) and quark () mesons because of their capability
to resolve widely-separated states of comparable strength. The analysis of the
Gaussian QCD sum-rules (GSRs) for all possible two-point correlation functions
of gluonic and non-strange () quark scalar () currents is
discussed. For the non-diagonal sum-rule of gluonic and currents we
show that perturbative and gluon condensate contributions are chirally
suppressed compared to non-perturbative effects of the quark condensate, mixed
condensate, and instantons, implying that the mixing of quark mesons and
gluonium is of non-perturbative origin. The independent predictions of the
masses and relative coupling strengths from the non-diagonal and the two
diagonal GSRs are remarkably consistent with a scenario of two states with
masses of approximately 1 GeV and 1.4 GeV that couple to significant mixtures
of quark and gluonic currents. The mixing is nearly maximal with the heavier
mixed state having a slightly larger coupling to gluonic currents than the
lighter state.Comment: Updated version contains extended analysis and revised analysis
methods. 21 pages, 14 figure