1,764 research outputs found
Faddeev calculation of pentaquark in the Nambu-Jona-Lasinio model-based diquark picture
A Bethe-Salpeter-Faddeev (BSF) calculation is performed for the pentaquark
in the diquark picture of Jaffe and Wilczek in which is a
diquark-diquark- three-body system. Nambu-Jona-Lasinio (NJL) model is
used to calculate the lowest order diagrams in the two-body scatterings of
and . With the use of coupling constants determined from the
meson sector, we find that interaction is attractive in s-wave
while interaction is repulsive in p-wave. With only the lowest three-body
channel considered, we do not find a bound pentaquark state.
Instead, a bound pentaquark with is obtained with a
unphysically strong vector mesonic coupling constants.Comment: 22 pages, 11 figures, accepted version in Phys. Rev. C. Summary of
main changes/corrections: 1. "which only holds at tree level" below the eq.
(23) is added. 2. In the last paragraph of p.23 we added a remark that the
coupling constant obtained from Lambda mass is different from the estimate as
obtained from the meson spectru
Pion and Kaon Polarizabilities and Radiative Transitions
CERN COMPASS plans measurements of gamma-pi and gamma-K interactions using
50-280 GeV pion (kaon) beams and a virtual photon target. Pion (kaon)
polarizabilities and radiative transitions will be measured via Primakoff
effect reactions such as pi+gamma->pi'+gamma and pi+gamma->meson. The former
can test a precise prediction of chiral symmetry; the latter for
pi+gamma->a1(1260) is important for understanding the polarizability. The
radiative transition of a pion to a low mass two-pion system, pi+gamma->pi+pi0,
can also be studied to measure the chiral anomaly amplitude F(3pi)
(characterizing gamma->3pi), arising from the effective Chiral Lagrangian. We
review here the motivation for the above physics program. We describe the beam,
target, detector, and trigger requirements for these experiments. We also
describe FNAL SELEX attempts to study related physics via the interaction of
600 GeV pions with target electrons. Data analysis in progress aims to identify
the reactions pi+e->pi'+e'+pi0 related to the chiral anomaly, and
pi+e->pi'+e'+gamma related to pion polarizabilities.Comment: 16 pages, 6 figures, Latex Springer-Verlag style Tel Aviv U. Preprint
TAUP-2469-97, Contribution to the Workshop on Chiral Dynamics Theory and
Experiment, U. of Mainz, Sept. 1-5, 1997, to be published in Springer-Verlag,
Eds. A. Bernstein, Th. Walcher, 199
The Uses of Chiral Anomaly for Determination of the Number of Colors
The -dependence of the vertices , where is a pseudoscalar
meson and is the number of colors, is analyzed with regard for the
-dependence of the quark charges. It is shown that the best processes for
the determination of are the reactions and
as well as the decay \eta\ra\pi^+\pi^-\gamma.
The measurement of the cross section \sigma(\pi^-\gamma\ra\pi^-\eta) at the
VES facility at the IHEP agrees with the value .Comment: 7 pages, 1 figure; accepted to Phys. Atom. Nucl., references adde
The soft and the hard pomerons in hadron elastic scattering at small t
We consider simple-pole descriptions of soft elastic scattering for pp, pbar
p, pi+ p, pi- p, K+ p and K- p. We work at t and s small enough for
rescatterings to be neglected, and allow for the presence of a hard pomeron.
After building and discussing an exhaustive dataset, we show that simple poles
provide an excellent description of the data in the region - 0.5 GeV^2 < t <
-0.1 GeV^2, 6 GeV<sqrt(s)< 63 GeV. We show that new form factors have to be
used, and get information on the trajectories of the soft and hard pomerons.Comment: 27 pages, 9 figures, LaTeX. A few typos fixed, and references
correcte
Search for the pentaquark resonance signature in lattice QCD
Claims concerning the possible discovery of the \Theta^+ pentaquark, with
minimal quark content uudd\bar{s}, have motivated our comprehensive study into
possible pentaquark states using lattice QCD. We review various pentaquark
interpolating fields in the literature and create a new candidate ideal for
lattice QCD simulations. Using these interpolating fields we attempt to isolate
a signal for a five-quark resonance. Calculations are performed using improved
actions on a large 20^3 x 40 lattice in the quenched approximation. The
standard lattice resonance signal of increasing attraction between baryon
constituents for increasing quark mass is not observed for spin-1/2 pentaquark
states. We conclude that evidence supporting the existence of a spin-1/2
pentaquark resonance does not exist in quenched QCD.Comment: 42 pages, 28 figures, 11 table
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