We have measured exclusive ρ0, ω, and φ meson electroproduction at the Cornell Wilson Synchrotron. The final ρ0 data sample included 4637 four-constraint e+p→e+π++π−+p events, with incident energy E=11.5 GeV and electroproduction variables Q2 and W in the region 0.7<Q2<4 GeV2 and 1.9<W<4 GeV. We find that the width of the forward ρ0 diffraction peak increases rapidly as the lifetime of the intermediate hadron states decreases below cΔτ=1 fm and that the peak is wider for longitudinal ρ0 than it is for transverse ρ0. The longitudinal-transverse cross-section ratio Rp=σLσT, obtained assuming s-channel helicity conservation, becomes constant at high Q2. At fixed W the diffractive vector-meson-dominance (VMD) model reproduces the Q2 dependence of our cross section, σ=(σT+εσL), but is is not able to account for the rapid decrease in the cross section with increasing W we observe. We find that σωσρ depends on W but is independent of Q2 for 0.7<Q2<3 GeV2 and 2.2<W<3.7 GeV. However, σω is substantially larger than the diffractive VMD cross section. Our results for σφ are consistent with the Q2 dependence of the diffractive VMD model for 0.8<Q2<4 GeV2 and 2<W<3.7 GeV, but this model again fails to predict the W dependence we observe.
FOUR CHANNEL FIT TO TWO PION PRODUCTION ASSUMING NO INTERFERENCE.
DEPENDENCE OF TOTAL, LONGITUDINAL (L) AND TRANSVERSE (U) DIFFERENTIAL CROSS SECTIONS ON C*DELTA(TAU), THE FORMATION TIME FOR VIRTUAL INTERMEDIATE HADRON STATES. DELTA(TAU) IS 1/DELTA(E) WHERE DELTA(E) IS E(RF=LAB,P=3) - NU = SQRT(NU**2 + Q2 + M(RHO)**2) - NU.
No description provided.
Results are presented on vector meson production in the hypercharge exchange reactions: π + p → K ∗+ (890) Y + and K − p→ ρ − Y + where Y + is either Σ + or Y ∗+ (1385). These reactions have been studied at 7 GeV/ c and 11.5 GeV/ c using the SLAC Hybrid Facility. Total and differential cross sections, hyperon polarization, and vector meson decay angular distributions are presented. We find that reactions with Σ + production are dominated by natural parity exchange. The Y ∗ (1385) reactions are consistent with substantial natural parity exchange contributions but also show significant unnatural parity exchange. The differential cross sections and polarization measurements for the vector meson production are compared to the pseudoscalar production reactions.
Axis error includes +- 20/20 contribution.
Axis error includes +- 20/20 contribution.
Axis error includes +- 20/20 contribution.
We have studied hypercharge exchange in two pairs of line-reversed reactions at 7 GeV/ c incident beam momentum in a triggered bubble chamber experiment at the SLAC Hybrid Facility. The experiment was carried out with the particular object of testing the predictions of exchange degeneracy using the same apparatus. We present differential and total cross sections for the reactions π + p → K + Σ + , K − p →π − Σ + and π + p → K + Y ∗+ (1385), K − p →π − Y ∗+ (1385) from a π + exposure of sensitivity 150 events/μb and a K − exposure of 100 events/μb. In each case we have measured the polarization of the final-state hyperon for | t |<1.0 (GeV/ c ) 2 by direct observation of its decay in the bubble chamber. We present results from an amplitude analysis of the Y ∗ (1385) reactions and find agreement with the predictions of the additive quark model. The Σ + polarization data are consistent with weak exchange degeneracy but the predicted equality of the differential cross section is not observed.
Axis error includes +- 10/10 contribution.
Axis error includes +- 10/10 contribution.
INCREASED STATISTICS OVER EARLIER RESULTS REPORTED IN P. A. BAKER ET AL., PRL 40, 678 (1978).
Cross sections, differential cross sections, and hyperon polarization results are presented for the reactions K¯0p→Λπ+ and K¯0p→Σ0π+ in the momentum interval 1 to 12 GeV/c. Emphasis is placed on the comparison of Λ and Σ channels, and on the momentum dependences of the data. In particular, the Λ polarization data are consistent with being independent of energy above 2 GeV/c; and the slopes of the forward cross sections are found to increase toward the slope values for the line-reversed reactions πp→K(Λ,Σ) as energy increases.
No description provided.
No description provided.
RESONANCE REGION CROSS SECTIONS.
The differential cross sections for KL0p→KS0p scattering are presented in several momentum intervals between 1 and 10 GeVc. The data are strongly peaked in the forward direction, characteristic of a large s-channel helicity-nonflip scattering amplitude in this reaction, and a distinct break in the differential cross section occurs at |t|=0.3 GeV2. The phase of the forward scattering amplitude, φ, is consistent with being independent of momentum. The average value of the phase, φ=−133.9±4.0∘, corresponds to a Regge trajectory α(0)=0.49±0.05 in agreement with the canonical ρ, ω0 Regge intercept, α(0)∼0.5. However, this result disagrees with the Regge trajectory determined from the energy dependence of the forward cross section, α(0)=0.30±0.03, indicating a breaking of the Regge phase-energy relation. Comparisons of KL0p→KS0p and π−p→π0n scattering data reveal substantial differences in the energy dependence of the differential cross sections. Comparisons to KN charge-exchange data then suggest that direct-channel (absorption) effects may explain the differences in πN and KN channels.
No description provided.
No description provided.
No description provided.
Total and differential cross sections are presented for the reaction KL 0p→KS 0p from 1.3 to 8.0 GeVc as measured in an exposure of the Stanford Linear Accelerator Center 40-in. hydrogen bubble chamber to a neutral beam. The forward points of dσ(KL 0p→KS 0p)dt together with K+n and K−n total cross sections are used to determine the intercept of the effective Regge trajectory, α(0)=0.47±0.09, and the regeneration phase ϕf=−43∘±8∘.
No description provided.
FULL T REGION.
FULL T REGION.
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