P. Duinker

Inclusive single-particle distributions in π±p reactions at 8 and 16 GeV/c

Abstract Invariant single-particle cross sections for pion and proton production in π ± p interactions at 8 and 16 GeV/ c are presented in terms of integrated distributions as functions of x , reduced rapidity ζ and p ⊥ 2 , and also in terms of double differential cross sections E d 2 σ /(d x d p ⊥ 2 ) and d ζ d p ⊥ 2 ). A comparison of π ± and π − induced reactions is made and the energy dependence is discussed. It is shown that the single-particle structure function cannot be factorized in its dependece on transverse and longitudinal momentum. For the beam-unlike pion, there is an indication for factorizability in terms of rapidity and transverse momentum in a small central region.

Precision measurement of proton-proton total cross section at the CERN intersecting storage rings

Abstract The measurement of the proton-proton total cross section performed by the CERN-Pisa-Rome-Stony Brook Collaboration at the CERN ISR is discussed in detail. The total interaction rate, the elastic scattering rate in the forward direction, and the machine luminosity were measured simultaneously to obtain three different determinations of the total cross section. Consistent results were found, which made it possible to prove the reliability of the Van der Meer luminosity calibration within +-0.9% and to achieve a precision of +-0.6% in the measurement of the total cross section.

New measurements of proton-proton total cross section at the CERN intersecting storage rings

Abstract Measurements of the proton-proton total cross section have been made with increased precision (±0.6%) over the ISR energy range s =23.5−62.7 GeV . Two different experimental methods gave consistent results, showing that the total cross section increases 10% over the ISR range and in addition that the absolute value of the ISR luminosity can be measured to ±0.9%.

Charged particle multiplicity distributions for 33.8 GeV/c K−p and 50 GeV/c π−p interactions

Abstract Topological cross sections and average charge multiplicities 〈 n c 〉, are presented for 33.8 GeV/ c K − p and 50 GeV/ c π − p interactions observed in the 4.5 m Mirabelle hydrogen bubble chamber at Serpukhov. Values for 〈 n c 〉 of 5.16 ± 0.08 and 5.71 ± 0.13 were found for the K − p and π − p reactions, respectively. The two quantities 〈 n c 〉 and the correlation term ƒ; 2 have been tabulated for π ± p, K ± p, and pp reactions at various energies. It is shown that the energy variation of each of these two quantities is described by a universal curve when plotted against the Q -value of the reaction. The ratio 〈 n c 〉/ D , where D is the dispersion of the multiplicity distribution, is found to approach the constant value of 2 from above as the energy increases.

Study of lambda production in 10 GeV/c K−p interactions

Lambda production is studied in K−p interactions at 10.1 GeV/c, where the dominant reaction is K−p → Λ + pions. General characteristics such as the distributions of the double differential cross section in the lab system, of the variable x = pL∗pmax∗, of p⊥2 and of the missing mass to the lambda are presented. Total cross sections for Λ production and for the various channels are given. Differential cross sections dσdt, dσdt′ and dσdu′ are presented. Forward and backward peaks are observed in the dσdt′ and dσdu′ distributions, respectively. It is found that the exponential slope of these distributions decreases with increasing missing mass to the lambda and, for dσdt′, also for increasing multiplicity in the final state. The polarization of the lambdas is studied as a function of multiplicity, pL∗, (Λπ±) effective mass, t′ and u′. The forward lambdas show

Dominance of isospin zero exchange in π±p → π(Nπ) at 16 GeV/c and production by it of a low mass (Nπ) enhancement

An isospin analysis has been made of the production of (Nπ) states in the reactions π±p → π(Nπ) at 16 GeV/c. The three independent amplitudes and their three interference terms have been determined as functions of the (Nπ) mass. It is found that at 16 GeV/c isospin-zero exchange is the dominant process, and isospin-one occurs much less frequently, mostly producing the I = 32 Δ (1236) isobar. Interference effects do not seem very important. The I = 12 (Nπ) mass spectrum due to isospin-zero exchange presents a broad enhancement from 1.1 to 1.8 GeV, with a broad maximum between 1250 and 1500 MeV. The N* isobars found by phase shift analyses at 1470, 1520, 1690, etc. MeV cannot account for the whole enhancement observed and in particular for its low-mass part. These results are consistent with the interpretation that diffractive phenomena are important at low Nπ masses and may cause mass enahancements not revealed byphase-shift analyses.

Measurement of the real part of the k- p elastic scattering amplitude at 10 gev/c

Abstract Bubble chamber film of 10 GeV/ c K − p interactions was scanned automatically by an H.P.D. to look for small angle scatters in the | t |-range from 0.008 to 0.1 GeV 2 . Combining the 1800 events so obtained with 22 000 elastic events obtained from normal scanning (| t | > 0.06 GeV 2 ), the real part of the elastic scattering amplitude was found to be (+25 ± 10)% of the imaginary part. Evidence is found for a change in slope in the differential cross-section distribution, from 9.8 ± 0.6 GeV −2 in the | t |-range below 0.1 GeV 2 to 7.1 ± 0.2 GeV −2 in the range 0.12 t | ⩽ 0.4 GeV 2 .

Inclusive Δ++ production and a test of the triple regge limit

Abstract Results on the inclusive reaction π+ p→Δ++ X0 at 8, 16 and 23GeV/c are used for quantitative tests of the triple Regge formula. As predicted, the slopes ofthe missing mass (M) spectra at fixed t are independent of s. Furthermore the trajectory α(t) obtained from the s-iependence at fixed M appears consistent with that obtained from the M-dependence at fixed s. However, the pomeron intercept α (0) is found to depend on t, suggesting that no single triple Regge diagram dominates at the M and s values studied in this reaction. Provided such a t-dependence is allowed, a single term triple Regge formula gives a very satisfactory parametrisation of our data.

Study of the exchange mechanisms in the rho production reactions π±p→ϱN at 16 GeV/c

Abstract Results are presented of a study of the reactions π + p→ ϱ + p, π − p→ ϱ − p and π − p → ϱ 0 n, all at 16 GeV/ c . For ϱ + and ϱ − , the d σ /d t ′ distributions have a wide forward dip which results from ω exchange. For ϱ 0 , the d σ /d t ′ distribution is consistent with having a narrower forward dip as expected for π-exchange. The ω-exchange contribution is isolated from a linear combination of the three differential cross sections. It is found that the variation of the ω-exchange contribution with the energy s is consistent with s 2 α ω ( t )−2 , where α ω ( t ) = 0.5 + t . Using the Harari absorption model, the radius of interactions is found to be independent of energy. Evidence that exchange of both spin-parity series occurs was obtained from the density matrix elements. The values of ( ϱ 11 + ϱ 1−1 ) indicate that natural parity exchanges become more important at t ′ increases. The study of ( ϱ 00 GJ d σ /d t ′) allows us to isolate an exchange having the quantum numbers I =0, G =−1, P (−1) J =−1 which may represent the contribution of a “cut”, as no particle carrying these quantum numbers is known.

Transverse spectra in π±p and K−p interactions between 8 and 16 GeV/c

Abstract Using data from several bubble chamber experiments, we have studied the inclusive reactions π ± p → π − + X, K − p → K 0 + X and K−p → Λ + X at incident momenta ranging from 8 to 16 GeV/c. Single particle spectra are given as functions of the transverse energy E ⊥ = (p ⊥ 2 + m 2 ) 1 2 for selected intervals of the longitudinal rapidity y. Using these two variables we find a simple, mass independent, representation of all particle spectra. Within a large range of y, non-Lorentz-invariant E⊥ distributions are nearly exponential and, over several orders of magnitude in cross section, can be fitted well with the single-parameter function (eE⊥/T −1)−1. The slope parameter T is shown to depend on y but, in the central region, it appears to be independent of the particle mass and gives indications of approaching a limiting value of approximately 120 MeV. Implications of these results with regard to thermodynamic models are briefly discussed.