Three new bosons, referred to as S, T and U, have been observed in the reaction π - + p → p + X - using the missing-mass spectrometer; their masses are 1929, 2195 and 2382 MeV, respectively. Their physical widths are equal to our experimental resolution and compatible with zero-width, with the upper limits: Γ ≤ 35, ≤ 13 and ≤ 30 MeV, respectively. They are produced with the differential cross section d σ/d t between 20 and 40 microbarn per (GeV/ c ) 2 at an average t = 0.3 (GeV/ c ) 2 .
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Data at two additional π+ momenta (1.28 and 1.41 GeVc) in the reaction π+p→Σ+K+ are presented. Charge independence is tested over the c.m. energy range 1.820 to 2.090 GeV; we used our data for the Σ+K+ channel and published data for the π−p→Σ0K0 and Σ−K+ channels.
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Total and differential elastic cross-section data are presented at eight incident π+ momenta: 1.28, 1.34, 1.40, 1.43, 1.55, 1.68, 1.77, and 1.84 GeVc. These data were obtained from a hydrogen-bubble-chamber exposure at the Bevatron, and contain more than 65 000 events. This represents more than 1½ times the world's data hitherto available in this energy region.
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Results of a high-statistics study of π++p→ρ++p at 1.55-1.84 GeVc are consistent with dominance of π and ω exchange close to threshold. A pronounced dip in ρ00sdσdt at −t≃0.4 GeV2 may be attributed to pion exchange with strong absorption.
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Data at nine π+ momenta are presented in the following three-body final states: Σ+K+π0, Σ+K0π+, Σ0K+π+, ΛK+π+, pK+K¯0. The data consist of cross sections, Dalitz plots, and angular distributions for the quasi-two-body final state Y*+(1385)K+. In the channel Y*+(1385)K+ the production and Y* decay distributions are compared with the predictions of Stodolsky and Sakurai.
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EVENTS ABOVE BACKGROUND - NO FIT.
DATA VALUES TAKEN FROM PDG2 CHEW 73B COMPILATION WHICH READ THEM FROM THE GRAPH AND CONVERTED TO MUB. BACKGROUND NOT SUBTRACTED.
In a counter and wire spark chamber experiment with a polarized target, backward kaons were detected, and the Σ + 's identified by a missing-mass technique. An average polarization of −0.08 ± 0.05 was found for −0.2 < u < 0.1 GeV 2 .
THE MEAN POLARIZATION FOR ALL EVENTS IS -0.08 +- 0.05.
Data on polarization in backward elastic π + p scattering at 2.0, 3.5 and 4.0 GeV/ c are presented. The data at 2.0 GeV/ c are compared with the result of a recent phase-shift analysis. Our data at 3.5 and 4.0 GeV/ c , and existing data above 3 GeV/ c , show no significant energy dependence of the polarization over the measured u -range. A comparison with Regge models and with results from amplitude analysis is made.
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Charged multiplicity and π 0 cross sections for π − p inelastic interactions at 70 GeV/ c are presented. The data were obtained from an exposure of the BEBC bubble chamber equipped with a track sensitive target (TST) to an unseparated negative beam at the CERN SPS. About 10 000 events were used for the charged multiplicity study, and about 2000 Dalitz pairs for the π 0 production analysis. A total of 12 e + e − pairs with a mass higher than the π 0 mass were found and analysed in terms of η or ω Dalitz pairs or decay pairs of vector mesons. Comparisons with data at other energies are made in terms of charged prong, π 0 cross sections, and of multiplicity parameters. The moments of longitudinal and transverse momentum distributions of the π 0 are determined and compared to the predictions of quark counting rule models.
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Using a double arm electromagnetic calorimeter we have searched for narrow states produced in the exclusive reaction π − p→γγn at 13 GeV/c. No enhancements were observed in the mass range 2.0–4.0 GeV/c 2 . For example, the 90% confidence limit on η c production is σ ( π − p→ η c n)× B ( η c → γγ ) < 44 pb.
UPPER LIMIT (90 PCT CL) FOR SIG*BR(ETA/C --> 2 GAMMA).
A precise measurement of the differential cross section at zero degrees for the pion charge-exchange reaction π−p→π0n at pπ=522 MeV/c has been made. The result is dσdΩ (0∘)=4.32±0.11 mb/sr.
DIFFERENTIAL CROSS SECTION AT THETA = 0.
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