P. Michaelidis

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.

Evidence for unnatural spin-parity states of (Kππ)0 in the charge-exchange reaction K−p→(K0π+π−)n

Abstract A partial-wave analysis of the (Kππ)0 system produced in the charge exchange reaction K − p →( K 0 π + π − ) n has been made in the mass range 1.04 ⩽ M (Kππ) 2 3 of the cases, the (Kππ)0 system is produced in states of unnatural spin-parity, namely JP = 0− and 1+; the rest is in the natural spin-parity state JP = 2+ state is consistent with being all K∗ (1420). The unnatural spin-parity states are produced mostly (∼ 80% of the events) by natural parity exchange. The facts that unnatural spin-parity states are produced in this non-diffractive channel, with JP = 1+ dominant, and that the exchange responsible for their production is mostly of natural parity, are similar to what was found for the charged (Kππ)− system in the diffractive reaction K−p→(Kππ)−p. However, the absolute value and the energy dependence of the cross sections are very different in the two cases.

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 comparison of pion production in the reaction K−p → Λ + pions at 8.25 GeV/c with pp and ee annihilation data

Abstract We present data on the production of charged and neutral pions in the hypercharge annihilation reaction K − p → Λ + pions at 8.25 GeV/ c . Using the concept of available energy we have compared our data with that from the processes p p annihilation, and e e annihilation to hadrons. The measure of agreement among the three samples of data is in contrast with the behaviour of non-annihilation data, which we present for comparison, and indicates that over the present energy range our approach is a useful phenomenological way of looking at the annihilation process.

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.

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.

A study of the low-mass part of the (Kππ) system in the reaction K−p→K−pπ+π− at 8.25 GeV/c

SummaryThe low-mass (Kππ) system of the reaction K−p → K−pπ+π− at 8.25 GeV/c is studied. The cross-section of this reaction is (0.97± ±0.04) mb. The dependence of the cross-section on the proton-proton momentum transfer shows broadening of the diffraction peak with respect to increasing (Kππ) mass. The production of two-body and three-body resonances is discussed with respect to their occurrence in the four longitudinal-momentum phase space sectors ofpl(π+)vs.pl(π−). This allows to separate the three-body low-mass systems (Kππ) and (pππ), which can be produced diffractively, from the other quasi-two-body processes whose production mechanism is meson exchange. In order to discuss what spin-parity contributions can be distinguished in the lowmass (Kππ) system, theD-moments of the angular distributions of the (Kππ) system with respect to variation of its effective mass and to variation of the possible analyser directions are carried out. The result is that, in addition to the dominantJP=1+ content, there is a clearly identifiableJP=0− contribution to the low-mass (Kππ) system. This contribution can be estimated to be 10% by an analysis of the density of events in the Dalitz plot, which gives also that the ρ production amplitude with respect to the K*(890) production amplitude decreases with increasing (Kππ) mass. This result is in agreement with an analysis of the reaction K+p→ K+pπ+π−. In the Appendix are given the properties of theD-moments and their predictability or suppression with respect to various spin-parity contributions.RiassuntoSi studia il sistema (Kππ) di piccola massa della reazione K−p→K−Pπ+π− a 8.25 GeV/c la cui sezione d’urto è (0.97±0.04) mb. La dipendenza della sezione d’urto dell’impulso trasferito protone-protone mostra un’allargamento del picco di diffrazione in corrispondenza dell’aumento della massa del sistema Kππ. Si discute la produzione di risonanze a due e a tre corpi rispetto al fatto che si verifichino nei quattro settori dello spazio delle fasi dell’impulso longitudinale definiti dapl(π+) in funzione dipl(π−) Ciò permette di separare i sistemi a tre corpi Kππ e pππ di massa piccola che si possono produrre per diffrazione dagli altri processi a quasi due corpi il cui meccanismo di produzione è lo scambio di mesoni. Al fine di discutere quali contributi di spin-parità si possono distinguere nel sistema Kππ di massa piccola, si calcolano i momentiD della distribuzione angolare del sistema Kππ rispetto alla variazione della sua massa effettiva e alla variazione delle possibili direzioni dell’analizzatore. Il risultato è che, oltre al contenuto dominante diJP=1+, vi è un contributoJP=0− chiaramente identificabile al sistema Kππ di massa piccola. Si è potuto valutare questo contributo in 10% da un’analisi della densità di eventi nel diagramma di Dalitz, che indica anche che l’ampiezza di produzione di ρ rispetto all’ampiezza di produzione di K*(890) diminuisce al crescere della massa di Kππ. Questo risultato è in accordo con un’analisi della reazione K+p→K+pπ+π−. Nell’Appendice si dànno le proprietà dei momentiD e la loro previdibilità o sopprimibilità nei confronti dei vari contributi di spin-parità.РеэюмеИсследуется (Kππ) система с малой массой в реакции K−p→K−pπ+π− при 8.25 ГзB/c. Поперечное сечение зтой реакции составляет (0.97±0.04) mb. Зави-симость поперечного сечения от протон-протонного передаваемого импульса покаэы-вает ущирение дифракционного пика при увеличении массы (Kππ). Обсуждается рождение двухчастичных и трехчастичных реэонансов относительно их появления в секторах фаэового пространства четырехмерного продольного импульсаpl(π+) в эависимости отpl (#x03C0;−). Это поэволяет раэличить трехчастичные системы с малыми массами (Kππ) и (pππ), которые рождаются дифракционным обраэом иэ других кваэи-двухчастичных процессов, механиэм рождения которых представляет меэонный обмен. Чтобы обсудить, как можно раэличить вклады с раэличными спинами и четностями в систему (Kππ) с малой массой, аналиэируютсяD-моменты угловых распределений (Kππ) системы по отнощению к иэменению ее зффективной массы и к иэменению воэможных направлений аналиэаторов. Получен следуюший реэуль-тат: помимо доминируюшегоJP=1+ вклада, сушествует ясно идентифицируемыйJp=0− вклад в систему (Kππ) с малой массой. Можно оценить, что зтот вклад составляет 10% с помошью аналиэа плотности событий на диаграмме Далитца, которая также укаэывает, что амплитуда ρ-рождения по отнощению к амплитуде K*(890)-рождения уменьщается с увеличением массы (Kππ). Этот реэультат со-гласуется с аналиэом реакции K+p→K+pπ+π−. В приложении приводятся свойстваD-моментов и их предскаэуемость или опускание по отнощению к вкладам с раэ-личными спинами и четностями.

Shape of the invariant differential cross section in the reactions K−p→K0 + anything and K−p → Λ anything at 8.2 GeV/c

The energy dependence and shape of the differential cross sections for the reactions K−p→K0 + anything and K−p → Λ + anything have been studied in the koan and proton fragmentation regions. We have shown that their behaviour may be understood within the framework of the triple-Regge model, and that the dominant contribution to the shape of the differential cross section comes from the intercepts of the appropriate trajectories.