K − p reactions have been studied at 13 different incident momenta between 1138 and 1434 MeV/ c . This interval corresponds to a mass of the K − p system varying from 1858 to 1993 MeV. About 300 000 photographs were taken in the 81 cm Saclay hydrogen bubble chamber exposed to a separated K − beam at the CERN proton-synchrotron. A total of about 44 000 events were analyzed, from which partial and differential cross sections were determined. Polarizations were obtained for the two-body reactions where the decay of the Λ or Σ hyperon allowed their measurement. Data for the two-body channels are presented here as well as for the main quasi-two-body reactions.
PARTIAL CROSS SECTIONS. DATA AT 1.305 TO 1.434 GEV/C FOR FINAL STATES K- P, K- P PI0 AND K- N PI+ COME FROM THE HAIFA GROUP, S. DADO ET AL.
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Measurements were made of the differential cross sections for the charge exchange of K − mesons on protons at momenta of 25 and 40 GeV/ c using a high-precision spectrometer with no magnetic field. In the range 5–40 GeV/ c the reaction cross section follows a power-law dependence p K − −1.52 . In the snall momentum transfer region (− t ⪅ m π 2 ) a minimum is observed, similar to that discovered at lower energies. The differential cross sections t = 0 are considerably less than those predicted by the Regge-pole model. The parameters of the effective trajectory are determined.
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Total and differential cross sections are presented for the reactions K − p → K − p and K − p → K o n at 13 points in the c.m. energy range 1915–2168 MeV. An energy-dependent partial-wave analysis is carried out on these data together with the polarisation measurements of Daum et al. [1] and the total cross section measurements [2] within this energy range. The well known Σ(1915), Σ(2030) and Λ(2100) are observed and their resonance parameters measured. Structure is also found in the D 05 and F 07 waves. An SU(3) analysis of the 5 2 + octet, 7 2 + decuplet and 7 2 − singlet gives generally good agreement between theory and experiment except that the elasticity of the Σ(1915) is experimentally rather larger than predicted.
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DETERMINED BY NORMALIZING AT ZERO DEG TO TOTAL CROSS SECTIONS VIA THE OPTICAL THEOREM.
We present the results on total channel cross-sections obtained in the Saclay 180 l HBC exposed to a separated K− beam at Nimrod. The cross-sections for each channel are given at 13 incident K− momenta between 1.26 and 1.84 GeV/c.
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The\(K^ -p \to \bar K^0 n\) charge exchange differential cross-section has been measured at 30 GeV/c with high statistical accuracy and high angular resolution. The experiment was made at the IHEP 70 GeV accelerator, by using a hodoscope hadron calorimeter to detect KL0. The cross-section shows a dip at small |t|, which indicates a dominance of spin-flip amplitudes in ρ and A2 exchanges in thet-channel.
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The K − p reactions leading to charge exchange and hyperon final states have been studied at nine momenta between 862 and 1001 MeV/ c using data from a 600 000 picture exposure of the Lawrence Berkeley Laboratory 25″ liquid hydrogen bubble chamber. Partial cross sections are determined for all final states resolved by kinematic fitting. In addition, differential cross sections are presented for the two-body final states K o n , Λπ o and Σ +- π -+ along with hyperon polarization angular distributions for Λπ o and Σ + π − .
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AVERAGED OVER ALL PRODUCTION ANGLES.
A bubble-chamber study is presented of a 10 events/μb experiment using K − mesons of 4.25 GeV/ c incident momentum. Differential and total cross sections are determined for 7 different reactions: K − p → K 0 n ( la ), → π 0 Λ ( lb ), → ηΛ ( lc ), → η′Λ ( ld ), → π − Σ ( le ), → π + Σ − ( lf ), K + Ξ − ( lg ) . The experimental characteristics in d σ /d t of each reaction are described: (la) shows a levelling off at t = 0 (GeV/ c ) 2 , a break at t = −0.6 (GeV/ c ) 2 and no backward events, (lb) d σ /d t has a smooth behaviour and a measurable backward component with an indication of a dip at u = −0.2 (GeV/ c ) 2 , (1c) d σ /d t shows a dip in the region between t ≈ −0.2 and −0.4 (GeV/ c ) 2 , (ld) d σ /d t has a smooth behaviour; neither this reaction nor the preceding one shows a clear evidence for backward events, (le) d σ /d t has a break at t = −0.5 (GeV/ c ) 2 ; there is a significant cross section in the backward region; (lf) and (lg) show mainly backward production. The polarization of the hyperon is measured in the reactions (lb), (lc), (ld) and (le) in the forward production peak. The statistics do not allow the detection of a definite structure in the polarization but the sign and magnitude are determined. An interpretation of the results is given in terms of a dual Regge model, including the effects of absorption as elaborated recently by several authors.
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Differential cross sections for K−p→K¯0n and K+n→K0p have been measured at 3, 4, and 6 GeV/c using a data sample of 6000 events. Contrary to simple exchange-degenerate models, the ratio of K+ to K− cross sections was found to be approximately 1.35, with little dependence on either s or t. Both reactions show a shallow dip near the forward direction, suggesting the importance of spin-flip amplitudes.
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LARGE -T CONTRIBUTIONS (TYPICALLY 12 PCT) ESTIMATED FROM BUBBLE-CHAMBER DATA.
The cross sections for the line-reversed reaction pairs K+n→K0p and K−p→K¯0n, and K+p→K0Δ++ and K−n→K¯0Δ− have been determined with high statistics and good relative normalization at 8.36 and 12.8 GeV/c in a spectrometer experiment at Stanford Linear Accelerator Center. The cross sections for the K+-induced reactions are larger than for the K−, contrary to the expectations of weakly-exchange-degenerate Regge-pole models. The ratio of the reaction cross sections is about the same as at lower energies and shows little change with momentum transfer.
Axis error includes +- 11/11 contribution.
Axis error includes +- 11/11 contribution.
Axis error includes +- 11/11 contribution.
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