M.F. Hodous

Inclusive and semi-inclusive ϱ0 production in π−p interactions at 15 GeV/c☆

Abstract We have done an inclusive study of ϱ0 production in π−p interactions at 15 GeV/c. Evidence for two different production mechanisms, in addition to the known quasi two-body processes, is presented: production of ϱ0s in the central region of rapidity similar to the “pionization” region seen in the inclusive studies of pions; and forward production in the beam dissociation region of rapidity. Cross sections and rapidity distributions for the ϱ0 are given inclusively and by topology, and the results are compared with similar studies at other energies and with other incident particles. Results are also presented for the semi-inclusive reaction π−p → pϱ0 + X− and the exclusive final state pπ−ϱ0.

Cross channel isospin amplitudes for 3.9 GeV/c π+-p → π(Nπ) compared with the predictions of a double exchange model

A cross-channel isospin analysis has been carried out on a prism plot separated sample of 3.9 GeV/c π+-p → π(Nπ) events. An enhancement is observed in the low (Nπ) invariant mass region for an I = 12 state of the Nπ system when the isospin for the cross channel is both IE = 0 and 1. These results and those of similar analyses at 8 and 16 GeV/c are compared with the predictions of a double-exchange model and good agreement is obtained. Neither interpretation of this phenomenon as a resonance nor as a consequence of diffraction dissociation in the usual definition, non-resonating single pomeron exchange, explains all the features of the results.

s-and t-channel helicity conservation of pion induced nucleon diffraction dissociation at 3.9 GeV/c and the implications of a two-component model☆

Abstract A study of schannel and t-channel helicity conservation has been carried out on a prism plot separated sample of 3.9 GeV/c π±p → π (Nπ)dd diffraction dissociation events. s-channel helicity conservation is found to be strongly violated while t-channel helicity conservation is found to be mildly violated. These results are similar to that found at 11.7 GeV/c. We explain these violations on the basis of a “two-component model” of which the first component is a single exchange amplitude. We postulate that this amplitude is the generalization of the pomeron exchange amplitude which may conserve s-channel helicity. The second component of the model is a double exchange mechanism which strongly violates s-channel helicity. The predictions of this model agree with the experimental data.

A two-component model definition of two-body nucleon diffraction dissociation in πp → π(Nπ)reactions at 3.9 GeV/c and comparison with other experiments☆

Abstract Four low-mass “diffractive like” reactions π ± p → π ± (p π 0 ) and π ± p → π ± (n π + ) have been studied at 3.9 GeV/ c incident pion momentum. These channels have been studied in the framework of a two-component model and we have proposed a definition of the diffraction dissociation amplitude. The following three features of the data are discussed: (1) an apparent violation of the predictions of isospin invariance for the cross section ratios, (2) the marked anisotropy of the s -channel helicity distributions and (3) the absence of the cross-over effect in the differential cross sections. The predictions of a two-component model previously used to explain the low mass I = 1 2 ( N π) enhancement [1] and s - and t -channel helicity non-conservation [2] are seen to be in agreement with these observations. Predictions are also made for higher energy incident pions and incident K, p, and p projectiles. These predictions are compared with available data including recent results at Fermilab and ISR energies.

A two-component model for two-body nucleon diffraction dissociation and comparison with data from π-p at 3.9 GeV/c and p-p at fermilab and ISR energies

The isospin |M12o|2 amplitude measured by means of π±p interactions at 3.9 GeV/c is compared to the low mass diffraction dissociation distributions in the process p+p→p+X at incident momentum from 175 to 400 GeV/c and p+p→(nπ+)+p at 1500 GeV/c. The comparison is made within the framework of a two-component model which predicts that the properties of the |M12o|2 amplitude at 3.9 GeV/c should be describe the p-p process. This predictio n is shown to be in excellent agreement with the high energy data.

Vector Meson Production in Semi‐Inclusive π ‐ p Interactions

We have studied a sample of events taken in the SLAC 82″ chamber and measured by PEPR. These events contain an identified proton with momentum less than 1 GeV/c. We have isolated the produced ρ0 and ω in these events and have been able to classify them as to production mechanism. We find that these vector mesons are mainly decay products of diffractively produced mesons.