R.A. Donald

π±-p and p-p Elastic scattering at 8.5, 12.4 and 18.4 GeV/c

SummaryApproximately 60 000 events have been collected in a spark chamber experiment at the CERN Proton Synchrotron which studied elastic diffraction scattering of π--p and p-p at incident momenta of 8.5, 12.4 and 18.4 GeV/c and of π+-p at 8.5 and 12.4 GeV/c. Magnetic analysis of the incoming and diffraction scattered particle, together with measurement of all angles, permitted each event to be determined as elastic subject to three constraints, so that the inelastic background was rejected with. high efficiency, even at the larger momentum, transfers. Much of the data have been processed by the CERN Automatic Flying-Spot DigitizerHPD. A detailed description of the experimental technique and of the methods of analysis is given. The results, together with data from lower energies, confirm the remarkable energy-independence of the shape of the pion-proton diffraction scattering peak up to |t| = 1.5 (GeV/c)2, wheret is the square of the four-momentum transfer, over a range of pion energies from 2 to 18 GeV. Proton-proton scattering does however appear to show a shrinking diffraction peak. In general, the data agree with other experiments using both counter and bubble chamber techniques, but some differences do appear. During the experiment, data were taken which set an upper limit of 2·102 μb/(GeV/c)2 on the differential elastic cross-section dσ/dt over a range of |t| from 20.9 to 23.4 (GeV/c)2 at 13.4 GeV/c incident pion momentum.RiassuntoSi sono raccolti circa 60 000 eventi in un esperimento eseguito con camere a scintilla al protosincrotrone del CERN, in cui si è studiato lo scattering di diffrazione elastica di π--p e p-p a impulsi incidenti di 8.5, 12.4 e 18.4 GeV/c e di π+-p a impulsi di 8.5 e 12.4 GeV/c. L’analisi magnetica della particella entrante e di quella diffusa per diffrazione, assieme alle misure di tutti gli angoli, ha permesso di determinare ciascun evento come elastico con tre limitazioni, cosicclié il fondo inelastico venne scartato con ottima, efficienza, anche a grandi momenti trasferiti. Molti dei dati sono stati analizzati dall’Automatic Flying Spot Digitizer (HPD) del CEEN. Si fa una dettagliata descrizione della tecnica sperimentale e dei metodi di analisi. I risultati, assieme ai dati ottenuti a piÚ basse energie, confennano la notevole indipendenza dell’energia dalla forma del pico dello scattering di diffrazione pione-protone sinoa, |t| = 1.5 (GeV/o)2, in cuit è il quadrato del quadrimomento trasferito, in un intervallo di energia del pione fra 2 e 18 GeV. Invece lo scattering protone-protone sembra presentare un picco di diffrazione che si restringe. In generate i dati concordano con altri esperimenti che fanno uso sia di tecniche con contatori che di tecniche con camere a bolle, ma compaiono alcune differenze. Durante l’esperimento, si sono rilevati dei dati che impongono un limite superiore di 2·102 Μb/(GeV/c)2 alla sezione d’urto elastico differenziale dσ/dt in un intervallo. di |t| fra 20.9 e 23.4 (GeV/c)2 ad un impulso del pione incidente di 13.4 GeV/c.

The four-prong annihilation of 1.2 GeV/c antiprotons in hydrogen (II) π+π+π−π−π0 final state

Abstract Approximately 17 000 four-prong annihilations of 1.2 GeV/ c antiprotons in hydrogen have been analyzed. The present report considers those events with one neutral pion (5π). The 5π events show production of ϱ 0 , ϱ ± , f 0 , ω 0 , η 0 mesons, and the possibility of a ϱϱ enhancement at 1400 MeV/ c and/or a ϱπ enhancement at 1080 MeV/ c is considered. The influence of the Bose-Einstein correlation function of Goldhaber et al. [6] is investigated. Centre-of-mass angular distributions of the pions and centre-of-mass opening angles between pairs of pions are presented. The production upper limits at the 95% confidence level, for several resonant states are given.

Evidence for a narrow width boson of mass 2.95 GeV

Abstract In a search for resonances coupled to the p pπ − system, we have studied π − p interactions at 16 GeV/ c giving a forward antiproton, using the Omega spectrometer at CERN. In the final states involving a p , p and π − we observe a 5.6 (6.3) standard deviation enhancement in the p pπ − mass spectrum at (2.95 ± 0.01) GeV with a width consistent with the resolution ( σ = 15 MeV). The production cross section × branching ratio is estimated to be of the order 1 μb. The data are consistent with a resonance decaying partly via intermediate p p final states.

The applicability of Zweig's rule to p̄p annihilations at 3.6 GeV/c

Abstract The final states oππ and oKK arising from pp annihilations at 3.6 GeV/ c have been studied. The results are in agreement with Zweigs rule contrary to what is observed in high energy pp collisions.

Antiproton-proton annihilation into (KK + 3π) and (KK + 4π) at 1.2 GeV/c study of the DO properties

Experimental results are presented for the five- and six-body annihilations pp → KK3π and pp → KK 4π of 1.2 GeV/c antiprotons. Analysis of these results in terms of production of K∗(890), ϱ, ω, η and D(1280) resonances is made. A detailed analysis of the quantum numbers for the D-meson is given.

ANTIPROTON--PROTON ANNIHILATION INTO (KantiK + 3

Experimental results are presented for the five- and six-body annihilations pp → KK3π and pp → KK 4π of 1.2 GeV/c antiprotons. Analysis of these results in terms of production of K∗(890), ϱ, ω, η and D(1280) resonances is made. A detailed analysis of the quantum numbers for the D-meson is given.

pi

Abstract Performing a PWA of the π − π − π + system over the −t p/p range 0.2 to 0.4 GeV 2 we find evidence for a J P = 0 − , J G =1 − meson of mass 1342 ± 20 MeV and width 220 ±70 MeV decaying into ϵπ. This state is produced by natural parity exchange with a slope similar to that of elastic scattering. It can be interpreted as a radial excitation of the π meson (π′).

) AND (KantiK + 4

Abstract The reaction π − p → φφ n has been isolated at 16 GeV/ c and its cross section determined to be 40 ± 10 nb. The φφ mass spectrum shows a threshold enhancement between 2.1 and 2.5 GeV. A successful description of the angular content of the φφ system requires two interferingss J P = 2 + states.

pi

Abstract The analysis of 18 900 V O events is presented, with reference to the production of K K and K K π resonances in the three-, four-, five- and six-body final states. It is established that there is a threshold structure in the ( K K ) I=1 state which comes entirely from the decay of K K π resonances, the D O and E O . The S ∗ and E O are definitely observed. The isospin of the D O is confirmed to be 0, J D O ⩾1 and, under the assumption L D ω =0, J D PC =1 ++ . The F 1 is observed in the final state F 1 η O and the analysis of this channel leads to the conclusion that J F 1 PC =1 +− or 2 − In the five-body final state there is some appearance of two-peaks in the D O mas region, but with the present statistics there is no clear evidence for this effect. The cross sections for single and associated resonance production are given.

) AT 1.2 GeV/c STUDY OF THE D

We show that the four-body pp annihilations at rest: pp → KKππ cannot be interpreted without the introduction of a Kππ resonance, the C-meson. We find the properties of the C-meson are the following: M = 1242−10+9 MeV, Γ = 127−25+7 MeV, I JP = 12 1+.