Results on polarization in K − p, K + p and p̄p forward elastic scattering at 10 and 14 GeV/ c are presented.
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AVERAGED OVER ALL PRODUCTION ANGLES.
We have studied the K ππ system in the 14.3 GeV/ c reactions K − p → K − π + π − p, K − p → K 0 π − π 0 and K − p → K 0 π + π − n . The data have been obtained from a 500 000 picture exposure of the CERN 2m HBC. The first two final states are dominated by Q-production in the Kππ system; there is also an L-signal at M (K ππ ) ∼ 1.75 GeV. The reaction cross sections are compared to K − p data at other energies. We discuss the K ππ mass dependence of the diffractive production slope. Evidence is presented for a Q − p versus Q + p differential cross section cross-over around | t | = 0.17 GeV 2 . A t -channel isospin analysis for the KN → K ∗(890)π N channels in the Q-region shows that the I = 1 exchange amplitude is ⋍ 10% of the dominant I = 0 exchange amplitude. The K ππ decay distributions indicate a predominant J P = 1 + state in the Q-region, and an important J P = 2 − contribution in the L-region. We find neither s -channel nor t -channel helicity conservation at the meson vertex in the Q- or L-regions. The K π angular correlation moments within the K ππ diffractive system are characteristic of K π elastic scattering, suggesting a π -exchange Deck-type production mechanism. There is evidence for a Kf 0 and κπ contribution (where κ is the J P (K π ) = 0 + state) to the diffractive K ππ system. A fit to the K − π + π − and K 0 π − π 0 Dalitz-plot distributions for the Q-re gion indicates that the ratio of K ϱ to K ∗ π decay amplitudes decreases with increasing K ππ mass.
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Data on the inclusive production spectra of K S 0 and Λ from proton-proton collisions at 19 GeV are presented and discussed in connection with the earlier studied inclusive π − production spectrum. The three single-particle spectra are compared with a crude two-center thermal model for the average radiation from the pp collisions.
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A comparison is made of the properties and production mechanisms of the π + ω and K − ω systems produced in the reactions π + p → π + ω p at 4, 5, 8 and 16 GeV/ c and K − p → K − ω p at 10 and 16 GeV/ c . In the π + ω case apeak is observed at 1.23 GeV (the B meson), while the K − ω mass distribution has a threshold enhancement. The cross section of the low mass (<2.0 GeV) π + ω system falls as p lab −2 , while that of the low mass (<2.0 GeV) K − ω system is almost constant with energy, indicating diffractive production of the K − ω system, but not of the πω system. Using a modified version of the Illinois partial-wave analysis program, it is found that the K − ω system is dominantly produced in the J P = 1 + state with small contributions of 0 − and 2 + , mainly by natural parity exchange - as is found for reactions such as K − p → (K − π + π − )p which are predominantly diffractive. For the π + ω system in the B mass region, J P = 1 + states, produced mainly by natural parity exchange are found; the contributions of 0 − P, 1 − P, 2 − P and 2 + D are consistent with zero. The 1 + D state occurs in the π + ω case but not in the K − ω system, nor in the K ππ − system produced in the K − p → K ππ p reaction.
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FROM BREIT-WIGNER FIT TO B EVENTS AND CORRECTED FOR UNSEEN OMEGA DECAY MODES.
In an exposure of the Argonne National Laboratory 12-foot hydrogen bubble chamber to a beam of 12.4-GeV/c protons, we have measured the total and differential cross sections for the inclusive reactions p+p→γ+X, π0+X, K0+X, and Λ+X, as well as estimates for the inclusive η and Σ0 cross sections. We present the average number of π0, K0, and Λ as a function of the associated charge multiplicity. We observe that the average charge multiplicity in pp collisions is the same whether or not a π0, K0, or Λ is also produced in the interaction. Invariant cross sections are presented as a function of PT2 and x, the Feynman scaling variable. The π0 differential cross sections are consistent with the relation dσdP(π0)=12[dσdP(π+)+dσdP(π−)] for all pion momenta P. The differential cross section for Λ production indicates a break in the distribution of |t−tmin|=1.4 (GeV/c)2. The polarization of the Λ's is found to be consistent with zero for all values of x.
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Using a 16-GeV linearly polarized photon beam, we have measured asymmetries in the process γN→K+(Λ+Σ) from hydrogen and deuterium, for square of four-momentum transfer, t, between -0.01 and -0.8 (GeV/c)2. The data show that for −t≳0.1 (GeV/c)2, the cross sections for γp→K+Λ, γp→K+Σ0, and γn→K+Σ− are strongly dominated by natural-parity exchange, as is the case in single-pion photoproduction.
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We report the observation of a spin 4 resonance from the analysis of the reaction π − p→ K + K − n. The mass and width of the h-meson were determined to be 2050 MeV and 225 MeV. The quantum numbers are J P = 4 + , C = +1 and very probably I G = 0 + .
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A partial-wave analysis has been performed on the (K − π − π + ) system produced in the reaction K − p → K − π − π + p at 10 and 16 GeV/ c . In the Q mass region it is found that the two dominant states, K ∗ π and Kπ, both in 1 + S wave, are produced with different polarisations, helicity being approximately conserved in the t -channel for K ∗ π and in the s -channel for Kπ. This is in contradiction with the assumption that the amplitude can be factorised into “production” and “decay” parts, and hence that the two amplitudes are fully coherent. The phase variation of the two states do not indicate simple resonance behaviour. It is concluded that the Q-mass enhancement is composite.
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Results on the inclusive reactions K − p → K ∗− (890) + X + and K − p → K ∗0 (890) + X 0 at 14.3 GeV/c are presented. A comparison is made with previous data and with the reaction K − p → K 0 + X at 14.3 GeV /c . Predictions of a triple-Regge model for the variation of the unnatural and natural parity exchanges with the mass of the X system are examined. The experimental values of the structure functions are compared with those calculated from a quark model.
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