Electroproduction of exclusive $\phi$ vector mesons has been studied with the CLAS detector in the kinematical range $1.6\leq Q^2\leq 3.8$ GeV$^{2}$, $0.0\leq t^{\prime}\leq 3.6$ GeV$^{2}$, and $2.0\leq W\leq 3.0$ GeV. The scaling exponent for the total cross section as $1/(Q^2+M_{\phi}^2)^n$ was determined to be $n=2.49\pm 0.33$. The slope of the four-momentum transfer $t'$ distribution is $b_{\phi}=0.98 \pm 0.17$ GeV$^{-2}$. The data are consistent with the assumption of s-channel helicity conservation (SCHC). Under this assumption, we determine the ratio of longitudinal to transverse cross sections to be $R=0.86 \pm 0.24$. A 2-gluon exchange model is able to reproduce the main features of the data.
Axis error includes +- 18.6/18.6 contribution.
Axis error includes +- 18.6/18.6 contribution.
Axis error includes +- 18.6/18.6 contribution.
We have extended our survey of the reaction γ+p→p+e++e− by collecting 20 000 additional e+e− pairs in the invariant-mass region 900<m<1500 MeV. The measured interference pattern shows two enhancements at mass values of 1097 and 1266 MeV. The parameters of those structure, when interpreted as vector mesons in the VDM framework, are given.
No description provided.
We report measurements of the electroproduction of ϕ mesons from hydrogen at Q2 values of 0.23, 0.43, and 0.97 GeV2 with |t| varying from 0.125 to 1.3 GeV2 at each Q2 point. The data show no evidence for a Q2 dependence of the slope of the t distribution; the forward cross section falls with increasing Q2 as the square of the ϕ propagator; the decay angular distributions agree with the predictions of s-channel helicity conservation; and the ratio of the longitudinal to the transverse component increases linearly with Q2.
'DATA POINT ONE'.
'DATA POINT TWO'.
'DATA POINT THREE'. POOR STATISTICS - NOT IN PUBLISHED FIGURE.
We have studied photoproduction using a 1 m streamer chamber at DESY and a tagged photon beam with an energy range of 1.6 GeV < E γ < 6.3 GeV. We analysed approximately 30 000 events and report topological, channel and resonance production cross sections for a large number of reactions with three and five outgoing charged particles.
CHANNEL CROSS SECTIONS FOR 3, 5 AND 7 PRONG REACTIONS.
'PARAMETRIZATION'.
'INTERFERENCE'.