30 research outputs found
The scattering length based on near-threshold charmoniums photoproduction
Under the framework of Vector Meson Dominance model, the value of scattering
length can be expressed as a function of the ratio between total cross section
and , where is the ratio between final momentum
and initial momentum and positively correlated
with the center-of-mass energy. Based on the theoretical study of charmoniums
photoproduction within two gluon exchange model and effective pomeron model, we
research the scattering lengths of vector mesons and proton interaction in this
work. Results show that the scattering length
obtained from the two models are close and basically in agreement with the
theoretical prediction of Strakovsky and co-workers. Additionally, we first
calculate the scattering length of -proton interaction in two gluon
exchange model and effective pomeron model as am (1 am =
fm) and am, respectively. This is a little bit
different from the two models and requires precise measurements from subsequent
experiments. In short, our results will provide a theoretical reference for
future studies on characterizing the vector meson-proton scattering length.Comment: 7 pages, 7 figure
Unified Chew-Mandelstam SAID analysis of pion photoproduction data
A unified description of single-pion photoproduction data, together with
pion- and eta-hadroproduction data, has been achieved in a Chew-Mandelstam
parametrization which is consistent with unitarity at the two-body level.
Energy-dependent and single-energy partial wave analyses of pion
photoproduction data have been performed and compared to previous SAID fits and
multipoles from the Mainz and Bonn-Gatchina groups.Comment: 11 pages, 9 figures, and 2 table
Search for {\Theta^+} in KLp \to K+n reaction in KLF at JLab
The possibility of the existence of multiquark hadrons made of 4-quark for
mesons and 5-quark for baryons was predicted by Gell-Mann in Ref. [1]. The
renewed interest for the search of exotic pentaquark states was initiated by
the paper by Diakonov, Petrov, and Polyakov in Ref. [2]. The 2003 experimental
reports on the observation of {\Theta^+} pentaquark with a uudd{\bar s} quark
content created a big excitement and many following experiments have reported
its observation [3]. After high-statistics experiments at JLab, which did not
confirm previous claims by the CLAS collaboration, the community concluded that
the {\Theta^+} pentaquark either does not exist at all or has an extremely
small cross section, making it currently unobserved. There were different
review papers on this subject, either questioning the existence of the
{\Theta^+} or attempting to explain the reasons why reaching a conclusion based
on production experiments is challenging [4]. To address the challenge of
minimal 3-body final states, a formation experiment with a projectile kaon beam
is proposed. Below, we discuss how the {\Theta^+} could be observed in the KLp
\to {\Theta^+} \to {K^+}n reaction in the KLF experiment at JLab [5]
Physics Opportunities with Meson Beams
Over the past two decades, meson photo- and electro-production data of
unprecedented quality and quantity have been measured at electromagnetic
facilities worldwide. By contrast, the meson-beam data for the same hadronic
final states are mostly outdated and largely of poor quality, or even
nonexistent, and thus provide inadequate input to help interpret, analyze, and
exploit the full potential of the new electromagnetic data. To reap the full
benefit of the high-precision electromagnetic data, new high-statistics data
from measurements with meson beams, with good angle and energy coverage for a
wide range of reactions, are critically needed to advance our knowledge in
baryon and meson spectroscopy and other related areas of hadron physics. To
address this situation, a state of-the-art meson-beam facility needs to be
constructed. The present paper summarizes unresolved issues in hadron physics
and outlines the vast opportunities and advances that only become possible with
such a facility.Comment: 46 pages, 10 figures, 4 table
Experimental Tests of QCD Scaling Laws at Large Momentum Transfer in Exclusive Light-Meson Photoproduction
We evaluated CLAS Collaboration measurements for the 90◦ meson photoproduction off the nucleon using a tagged photon beam spanning the energy interval s = 3–11 GeV2. The results are compared with the “quark counting rules” predictions
Radiative Decay Width of Neutral non-Strange Baryons from PWA
An overview of the GW SAID and ITEP groups effort to analyze pion
photoproduction on the neutron-target will be given. The disentanglement the
isoscalar and isovector EM couplings of N* and Delta* resonances does require
compatible data on both proton and neutron targets. The final-state interaction
plays a critical role in the state-of-the-art analysis in extraction of the
gamma n --> pi N data from the deuteron target experiments. It is important
component of the current JLab, MAMI-C, SPring-8, ELSA, and ELPH programsComment: 7 pages, 7 figures, 1 table; Proceedings of International Conference
Dark Matter, Hadron Physics and Fusion Physics, Messina, Italy, Sept. 2014;
will be published in EPJ Web of Conference
Extraction of the D13(1520) photon-decay couplings from pion- and eta-photoproduction data
We compare results for the D13(1520) photon-decay amplitudes determined in
analyses of eta- and pion-photoproduction data. The ratio of helicity
amplitudes (A_3/2 / A_1/2), determined from eta-photoproduction data, is quite
different from that determined in previous analyses of pion-photoproduction
data. We consider how strongly the existing pion-photoproduction data constrain
both this ratio and the individual photon-decay amplitudes.Comment: 7 pages, 2 figure
Pseudoscalar and Scalar Meson Photoproduction Interpreted by Regge Phenomenology
We have evaluated pseudoscalar and scalar neutral pion photoproduction in
and above the resonance
region and within Regge phenomenology. Our fit, including GlueX
pseudoscalar photoproduction data, shows that previous SLAC
measurements for above
are at variance with SLAC data with more recent measurements made by GlueX in
vicinity of . The Regge model predicts that the beam
polarization asymmetry of the scalar meson is opposite to that of
pseudoscalar meson photoproduction, however, the cross sections are similar.
While the vector natural parity meson exchange is dominant in both cases, the
contribution of the pseudovector unnatural parity meson exchange is very small.
Using Regge phenomenology, we predicted high energy behavior for double
polarized observables , , , and
for the reactions and .Comment: 8 pages, 5 figures, several small glitches were fixe
Nucleon Helicity in Pion Photoproduction
Pion-photoproduction data is examined to check for the nucleon-helicity
conservation predicted by asymptotic QCD. The differential cross section shows
agreement with constituent-counting rules, and polarization data is not in
disagreement with conservation of nucleon helicity. However large uncertainties
in the polarization measurements do not allow a conclusive statement. The
helicity amplitudes from a partial-wave analysis are also examined for helicity
conservation. While the amplitudes become small as increases, the
dependence of the helicity-conserving amplitudes is similar to the dependence
of the non-conserving amplitudes.Comment: plain tex, 6 pages, 8 figure