R. Matthews

Cross sections of common final states for K−p interactions at 8.25 GeV/c

Abstract Topological and channel cross sections are given for the more common final states produced in K − p interactions at 8.25 GeV/ c together with the single particle inclusive cross sections. We present cross sections for prominent resonances occurring in final states K N (nπ) and find the resonance fractions to be roughly independent of multiplicity.

A study of inclusive reactions K−p → K0 + X0 and K−p → K∗− (890) + X+ at 8.25 GeV/c

The inclusive reactions K−p → K0 + X0 and K−p → K∗− (890) + X+ are studied in detail at 8.25 GeV/c. The most prominent experimental features are discussed in connection with a triple-Regge behavior and, where relevant, compared with the corresponding data of K+p at the same energy. Evidence for pseudoscalar exchange dominance at small t′ and low missing mass is suggested by the density matrix element analysis of K∗− (890). The natural- and unnatural-parity contributions to the cross section in the helicity frame indicate characteristics of absorptive behavior.

High transverse momentum and baryon exchange

Abstract Data are presented on the average transverse momentum of pions produced in events selected so as to enhance the baryon exchange contribution. High values are found compared with unselected events having only a small baryon exchange contribution.

Helicity conservation for K−p → Q−pat 8.25 GeV/c

Abstract The reaction K − p→Q − p→p(K − K − π + π − ) at 8.25 GeV/ c favours t -channel helicity conservation over s -channel helicity conservation. This is shown by comparing the Q density matrix elements with the predictions of the above two hypothesis as functions of the crossing angle.

Leading particles and charged particle multiplicity in annihilation and non-annihilation interactions

Using data from our K−p experiment at 8.25 GeV/c we have investigated the charged particle multiplicity, and the variation of charged pion multiplicity as a function of the effective mass squared of all pions, for various samples of data, and compared our results with pp annihilation data and pp data. Evidence is presented which suggests that the difference in behaviour between the annihilation and non-annihilation data is not due to some specific mechanism such as baryon exchange, but is related to the absence of leading particles in the former case.

A study of the reaction K−p → K−π−Δ++ (1236) at 8.25 GeV/c

Abstract The reaction K − p → K − π − Δ ++ has been studied at 8.25 GeV/ c in terms of the CLA model. Evidence for separate amplitudes including pomeron and K ∗ exchange was found. Good agreement was obtained between the model and our data without the need for any terms involving resonance production in the amplitudes for the reaction.

Experimental tests of the factorisation of Regge trajectories in the proton fragmentation region

Abstract We present double differential cross sections for the reactions K − + p → π ± + anything at 8.25 GeV/ c . Using published data for reactions K + + p→ π − + anything and p + p → π + anything we predict the differential cross sections for γ + p → π − + anything, π − + p → π − + anything and π − + p → π + + anything in the target fragmentation region based on factorisation of the pomeron and Regge trajectories. Our predictions agree with the experimental data and support the hypothesis of factorisation of the Regge trajectories in the target fragmentation region.

A study of the K−π− interaction from K−p data at 8.25 GeV/c

Abstract Total and elastic cross sections have been obtained for the I = 3 2 K − π − system as a function of K−π− mass by performing a one-pion-exchange analysis on K−p interactions at 8.25 GeV/c; the results indicate that the interaction becomes rapidly inelastic with increasing K−π− mass. The differential elastic cross sections have also been examined, and the data compared with an amplitude containing a Veneziano plus a diffraction term. Good overall agreement was achieved.

A study of the reaction K− p → K−ωp at 8.25 GeV/c

Abstract The final state K − ω p shows no significant resonance production at 8.25 GeV/ c . A double moments analysis of the broad threshold (K − ω ) enhancement shows the presence of 0 − , 1 + and 1 − spin-parity states. The last one was foundto contribute about 10% (while we were unable to separate the contributions from 1 + and 1 − . An analysis of the final state in terms of the CLA model shows qualitative agreement with the data. Moreover, using the same parameters, the predicted distributions at 6 and 10 GeV/ c show the same qualitative agreement with the published data.

Comparison of the reactions K±p→Q±p at incident momentum 8.25 GeV/c

Abstract In this paper a comparison of the general features of the reactions K ± p→Q ± p (1) at incident momentum 8.25 GeV/ c is presented. The relevant data derive from events yielding four-constraint fits to the reactions K ± p→K ± π + π − p in exposures of the CERN 2m HBC to RF-separated K + and K − beams. The (K ππ ) effective mass distributions, production angular distributions in the Q region (1.2⩽ M (K ππ )⩽1.5 GeV) and corresponding decay angular distributions are exhibited, and background effects due to N ∗ and Δ production are systematically studied. In particular, it is found that the distributions d σ /d t ′ and d σ /d t for reactions (1) are adequately described by exponential functions over the interval 0.05–0.35 GeV 2 , and exhibit a cross-over effect for momentum transfer squared −0.1 GeV 2 . For both reactions a flattening of d σ /d t ′ for t ′ 2 is observed. By studying the Chew-Low plots and the effects of the different cuts it was found that this flattening cannot be attributed to amplitudes with net s -channel helicity flip different from zero, at least at these energies.