The reactions ${\ensuremath{\pi}}^{+}p\ensuremath{\rightarrow}{\ensuremath{\Sigma}}^{+}(1385){K}^{+}$ and ${\ensuremath{\pi}}^{+}p\ensuremath{\rightarrow}{\ensuremath{\Sigma}}^{+}(1385){K}^{*+}(890)$ are examined. The ${\ensuremath{\Sigma}}^{+}(1385){K}^{+}$ differential cross section for $\ensuremath{-}{t}^{\ensuremath{'}}<0.5$ Ge${\mathrm{V}}^{2}$ and spin density matrix elements agree with a Regge-pole model incorporating (nondegenerate) vector and tensor ${K}^{*}$ exchange with dominant $M1$ coupling. The ${\ensuremath{\Sigma}}^{+}(1385){K}^{*+}(890)$ density matrix elements are consistent with the quark-additivity predictions. A ${Y}^{*+}$ at a mass of 1700 MeV is also observed in the $\ensuremath{\Lambda}{\ensuremath{\pi}}^{+}$ mass distribution, produced opposite both ${K}^{+}$ and ${K}^{*+}(890)$.

We have measured total hadronic photoproduction cross sections on carbon, copper, and lead. Tagged-photon energies ranged from 20 to 185 GeV for copper and from 45 to 82 GeV for carbon and lead. The energy and $A$ dependence of shadowing were computed by comparing these results to the hydrogen cross section as measured nearly simultaneously with the same apparatus. We observed somewhat more shadowing than did most experiments at lower photon energies.

The formation of KBr+ HgBr is the predominant reaction channel as deduced by the scattering kinematics.

The elastic photoproduction cross sections for $\ensuremath{\rho}$ and $\ensuremath{\phi}$ mesons from protons have been measured from 30 to 180 GeV. The energy dependences agree well with predictions made by using vector-meson dominance and an additive quark model. The $\ensuremath{\rho}$ cross section is approximately constant with energy while the $\ensuremath{\phi}$ cross section rises from 0.5 to 0.7 \ensuremath{\mu}b with increasing energy.

The photon total cross section on protons has been measured with high precision in the Fermilab tagged-photon beam for photon energies from 18 to 185 GeV. The cross section decreases to a broad minimum near 40 GeV, and then rises by about 4 \ensuremath{\mu}b over the remainder of the range. A $\ensuremath{\rho}+\ensuremath{\omega}+\ensuremath{\phi}$ vector-dominance model (normalized to low-energy data) falls below the high-energy results by 2 to 6 \ensuremath{\mu}b, suggesting a contribution from charm-anticharm states.

We report the result of a brief experiment to measure the cross section for photoproduction of $\frac{J}{\ensuremath{\psi}}(3100)$. At a mean energy of 55 GeV we find this cross section per nucleon to be 37.5 \ifmmode\pm\else\textpm\fi{} 8.2 (statistical) \ifmmode\pm\else\textpm\fi{} 4 (systematic) nb. The result establishes the previously indicated rise in $\frac{J}{\ensuremath{\psi}}$ photoproduction on protons above 20 GeV and suggests that the rise has occurred by 55 GeV.

A partial-wave analysis of the charged three-pion system in the reaction π−p→pπ+π−π− for incident π− momenta from 5 to 25 GeV/c shows the existence of a broad enhancement (∼ 300 MeV) in the JP=2−fπ (S-wave) state in the region of the A3(1650). No other state (J≤4) shows structure in this region. Upper bounds for ρπ and επ decay modes of the A3 are given. The interference of the 2−fπ (S-wave) amplitude with other amplitudes has been observed. The mass variation of the phase of the 2−fπ (S-wave) amplitude measured with respect to the phases of other amplitudes does not show the behavior expected for the relative phase between resonant and nonresonant amplitudes. Results are given on the polarization and momentum-transfer dependence of the A3 and on the A3 production cross section as a function of incident π− momentum.Received 17 July 1972DOI:https://doi.org/10.1103/PhysRevD.7.669©1973 American Physical Society

This paper reports the investigation of the reaction ${\ensuremath{\pi}}^{+}+d\ensuremath{\rightarrow}K+\ensuremath{\pi}+{\ensuremath{\Lambda}}^{0}+{p}_{s}$ at a bombarding energy of 7 GeV/c. A recent compilation of data concerning ${\ensuremath{\pi}}^{\ensuremath{-}}+p\ensuremath{\rightarrow}K+\ensuremath{\pi}+{\ensuremath{\Lambda}}^{0}$ showed a discrepancy in the decay ${K}^{*0}(890)\ensuremath{\rightarrow}{K}^{+}+{\ensuremath{\pi}}^{\ensuremath{-}}$ and ${K}^{0}+{\ensuremath{\pi}}^{0}$. The discrepancy was that too few of the latter decay modes were observed as compared with isospin predictions. This paper reports further investigation which shows a considerably smaller discrepancy than that previously found. The previously noted discrepancy must have been in part produced by a low scanning efficiency. The characteristics of these reactions are in other respects very similar to those observed at lower energies. The ${K}^{*}'\mathrm{s}$ seem to be produced by natural-parity exchange.