The angular distribution of 2720 tracks of 1085 hadronic final states produced from (e+e-) annihilation has been studied in the 1.2 to 3.0 GeV total centre-of-mass energy range. If we parametrize the angular distribution in terms off(θ) =1 + A cos2 θ, where 6 is the angle between the hadronic track produced and the colliding-beam direction, the results show thatA is less than 0.21, with 90% confidence.
ANGULAR DISTRIBUTION OF CHARGED HADRONS FOUND TO BE 1 + (0.07 +- 0.11)*(COS(THETA)**2).
A partial-wave analysis has been performed of the diffractively produced low-mass ( K ̄ 0 π − π 0 ) system in the reaction K − p → ( K ̄ 0 π − π 0 ) p at 10 and 16 GeV/ c . Thus information complementary to that derived from the K − p → (K − π + π − )p) channel is obtained. The presence of the K ϱ decay mode, besides the dominant K ∗ (890)π mode, for the state J P = 1 + , is confirmed. It is also confirmed that for this 1 + state the assumption of factorization of the amplitude into “production” and “decay” does not hold: the two decay modes K ∗ π and K ϱ have different polarisation properties (helicity is approximately conserved in the t -channel for the first, in the s -channel for the second). The assumption that the ( K ̄ 0 π − π 0 ) system has isospin I = 1 2 has been tested and found to hold. From the cross sections for the various J P states, assuming I = 1 2 , the cross sections for the (K − π + π − ) system are predicted and compared with the experimental ones. In general, agreement is found.
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A comparison is made of the low-mass three-meson systems (πππ), (Kππ), (π K K ) and ( K K K ) diffractively produced in the reaction meson + proton → three mesons + proton. Several striking similarities and a few important differences are observed: (i) the reactions are consistent with the assumption that the three mesons decay entirely into a 0 − meson and a 0 + , 1 − or 2 + resonance; (ii) the three-meson mass spectra have a peak ≈ 250 MeV above the effective threshold M eff of the dominant decay mode and then fall off approximately as (mass) −3 ;(iii) the average spin 〈 J 〉 = 0.55 + 1.1 Q eff , where Q eff = M - M eff ; (iv) the average orbital angular momentum 〈 l 〉 increases according to 〈 l 〉 = 0.75 Q eff ; (v) the three-meson states are produced dominantly in unnatural spin-parity states and no evidence for their being resonant is found; (vi) the only natural spin-parity states found are the well-established 2 + resonances A 2 and K ∗ (1420); they have similar properties to the non-resonant unnatural parity states except for a dip at t = 0 in the dσ/d t distributions; (vii) both the unnatural and natural spin-parity states are produced mostly by an exchange of natural parity; (viii) there is evidence for two types of production mechanism with different polarization properties, one approximately conserving helicity in the t -channel and the other in the s -channel.
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K L 0 p interactions were studied in the CERN 2m H 2 bubble chamber in the c.m. energy range 1490–1700 MeV. The experimental details are described. Results are presented on the final states Λπ + , Σ 0 π + and Λπ + π 0 . The effect of these data on a recent partial-wave analysis of the two-body states is examined.
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KL --> 3PI USED TO MEASURE ABSOLUTE CROSS SECTIONS AT 530 MEV/C.
Experimental results on the K L 0 p → K S 0 p reaction at 11 laboratory momenta between 300 and 800 MeV/ c are presented. The data are used to discriminate among the various sets of phase shifts for K + N scattering in the I = 0 state.
STATISTICAL ERRORS ONLY. CROSS SECTIONS ARE NORMALIZED RELATIVE TO THE PI+ LAMBDA EVENTS - SEE THE RECORD OF L. BERTANZA ET AL., NP B110, 1 (1976).
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We present a systematic analysis of the production of K ∗+ (892) and Δ ++ (1236) resonances in the K + p → K 0 p π + reaction at 5, 8.25 and 16 GeV/ c . We have measured total cross sections, differential cross sections, density matrix elements and examined resonance production mechanisms in terms of the exchange of states with definite naturality. Some results on the reaction K + p → K ∗+ (1420) p are also given.
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The analysis of A2−→ηπ− at 11.2 GeV/c confirms that A2− is essentially produced by natural-parity exchange. In the differential cross-section as a function oft′ there is evidence of the dip at smallt′ values. The branching ratio (A2→ηπ)/(A2→ϱπ) is 0.18±0.05.
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NUMERICAL VALUES SUPPLIED BY G. THOMPSON. 100 EVENTS IN A2 REGION DEFINED BY 1.18 < M(ETA PI-) < 1.44 GEV.
ROUGH BACKGROUND SUBTRACTION TO REMOVE NON-TRUE ETA EVENTS. FIRST THREE DENSITY MATRIX COMBINATIONS ARE NATURAL-PARITY EXCHANGE, THE REMAINDER BEING UNNATURAL-PARITY EXCHANGE.
We study the reactions π + p → π + p nπ 0 ( n = 2, 3) at 3.5 GeV/ c , with 940 and 143 events, respectively. Complete final states are recorded and measured in a heavy liquid bubble chamber. We find the cross sections: sigma;(π + p → π + p 2π 0 ) = 1300 ± 210 μ b , σ(π + p → π + p 3π 0 ) = 320 ± 70 μ b , below the values predicted by statistical models from charged pion data. The mass spectra are given and channel separations are performed using Van Hove variables. Our results are in agreement with charged pion experiments. We present a description of the 3 π 0 system, with 61 events. Under certain hypotheses a spin-parity analysis favours 0 − at low mass and 1 − at high mass.
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New experimental results on the reactions K L 0 p→K S 0 p, Λπ + , Σ 0 π + andΛπ + π 0 at c.m. energies between 1.54 and 1.71 GeV are presented. This experiment has a statistical accuracy comparable with or greater than corresponding K − p and K − d experiments in the same energy range and a comparison with the data from these different types of experiments has been made. A search has been made for narrow states with masses in the region of 1.58 GeV.
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We present results on charged multiplicity nch=2 and nch>2 muon events produced in e+e− collisions with 〈s12〉=7.3 GeV at 90° to the beams. The background-subtracted inclusive cross section for the nch=2 events is 10.2±5.4 pb/sr, in agreement with the expected contribution from the heavy lepton τ. The cross section for the nch>2 events is 19.0±6.5 pb/sr whereas we expect only 2.9 pb/sr from the τ, indicating that we may be seeing the weak decays of charmed mesons.
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