Cross sections or upper limits are reported for 12 meson-baryon and two baryon-baryon reactions for an incident momentum of 9.9 GeV/c, near 90° c.m.: π±p→pπ±,pp±,π+°±,K+Σ±, (Λ0/Σ0)K0; K±p→pK±; p±p→pp. By studying the flavor dependence of the different reactions, we have been able to isolate the quark-interchange mechanism as dominant over gluon exchange and quark-antiquark annihilation.
No description provided.
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We report a study of 20 exclusive reactions measured at the AGS at 5.9 GeV/c incident momentum, 90° center of mass. This experiment confirms the strong quark flow dependence of two-body hadron-hadron scattering at large angle. At 9.9 GeV/c an upper limit had been set for the ratio of cross sections for (p¯p→p¯p)(pp→pp) at 90° c.m., with the ratio less than 4%. The present experiment was performed at lower energy to gain sensitivity, but was still within the fixed angle scaling region. A ratio R(p¯ppp)≈140 was measured at 5.9 GeV/c, 90° c.m. in comparison to a ratio near 1.7 for small angle scattering. In addition, many other reactions were measured, often for the first time at 90° c.m. in the scaling region, using beams of π±, K±, p, and p¯ on a hydrogen target. There are similar large differences in cross sections for other reactions: R(K−p→π+Σ−K−p→π−Σ+)≈112, for example. The relative magnitudes of the different cross sections are consistent with the dominance of quark interchange in these 90° reactions, and indicate that pure gluon exchange and quark-antiquark annihilation diagrams are much less important. The angular dependence of several elastic cross sections and the energy dependence at a fixed angle of many of the reactions are also presented.
Cross sections at 90 degrees in the centre-of-mass.
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The exclusive process π−p→ρ−p has been measured at 90° c.m. with an incident pion momentum of 9.9 GeV/c. We present data on the angular dependence of the decay ρ−→π−π0. We observe a strong azimuthal dependence in the decay in the c.m. helicity frame of the ρ. Such an azimuthal dependence is not compatible with SU(6) valence-quark perturbation calculations.
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Results of a high-statistics study of elastic scattering and meson resonances produced by π−p interactions at 8 GeV/c are presented. Large statistics and small systematic errors permit examination of the complete kinematic region. Total differential cross sections are given for ρ0,−, f0, g0,−, Δ±, Δ0, and N* resonances. Spin-density matrix elements and Legendre-polynomial moments are given for ρ, f, and Δ resonances. The results for ρ0 and f0 resonances are compared with the predictions of a Regge-pole-exchange model. Properties of the above resonances are compared and discussed. In particular, we present evidence that the ρ0 and f0 production mechanisms are similar. The similarity of the g0 t distribution to that of the ρ0 and f0 suggests a common production mechanism for all three resonances.
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SLOPE REFERS TO EXPONENTIAL FIT IN U.
A new method, using spark chambers, for the study of the reactions π ± + p → ϱ ± + p is described. The charged pion and both γ rays from the π ± decay are detected. Differential and integrated cross sections σ π + =50 ± 9 μ b, σ π − =47 ± 9 μ b) for 0.0 ⩽| t |⩽1. (GeV/ c ) 2 and a laboratory momentum ( p Lab ) of 15 GeV/c are presented. The momentum dependence of σ γ ± is well fitted from 2.7 to 16 GeV/c by σ = K p Lab − with n γ + = 1.80 ± 0.80 and n γ − = 1.87 ± 0.15.
Axis error includes +- 17/17 contribution.
Axis error includes +- 17/17 contribution.
Mesons decaying into π 0 or η and one charged meson were studied using a liquid-argon calorimeter in a non-magnetic double-arm spectrometer. Cross sections and energy dependences are presented. The ϱ ± production mechanisms are discussed in detail: ω and π exchange contribute the largest fractions, but also A 2 exchange is present. ϱ ± production by ω exchange is shown to follow the energy behaviour predicted by the Regge trajectory α ω ( t ) = 0.4 − | t |.
Axis error includes +- 0.0/0.0 contribution (13 TO 25////STATISTICAL ERRORS ARE SMALLER THAN THE SYSTEMATIC ERRORS).
No description provided.
We have investigated the ρ-meson production mechanism in the three reactions π±p→ρ±p and π−p→ρ0n at 3.9 GeV/c (s=8.2 GeV2) using the prism-plot technique. Differential cross sections at all momentum transfers are presented. A significant backward peak has been found in all three reactions. The differential cross sections for these backward peaks are given and are compared with the equivalent pion elastic and charge-exchange cross sections in the backward direction. Using a linear combination of the three differential cross sections we have isolated the I=0 exchange contribution in the forward direction. This differential cross section has a zero at −t=0.45 (GeV/c)2 and is fitted by the dual absorptive model of Harari with an interaction radius of ∼ 1.2 F. The total I=0 cross section is calculated and compared with similarly determined cross sections at higher momenta. An analysis of the properties of the other possible spin-parity exchanges is also presented.
SLOPE FITTED OVER 0.05 < -T < 0.3 GEV**2.
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Results are presented of a study of the reaction π+p→ρ+p at 2.67 GeV/c incident π+ momentum. The contributions due to given spin-parity exchanges are isolated; and, by combining these results with those of a similar π− experiment, the It=0 component of each series is separated. The ω (I=0, JPG=1−−) exchange contribution shows a pronounced dip at −t=0.4 (GeV/c)2. Evidence is presented for the exchange of a state of minimum quantum numbers, H (I=0, JPG=1+−).
No description provided.
No description provided.
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