منابع مشابه
Combined QCD analysis of e + e − data at √ s = 14 to 172 GeV
A study of the energy dependence of event shape observables is presented. The strong coupling constant αs has been determined from the mean values of six event shape observables. Power corrections, employed for the measurement of αs, have been found to approximately account for hadronisation effects.
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The measurements of reactions πp → ππn and πn → ππp on polarized targets at CERN found a strong dependence of pion production amplitudes on nucleon spin. Analyses of recent measurements of πp → ππn reaction on unpolarized targets by GAMS Collaboration at 38 GeV/c and BNL E852 Collaboration at 18 GeV/c use the assumption that pion production amplitudes do not depend on nucleon spin, in conflict ...
متن کاملOn the Interpretation of Πn → Ππn Data near Threshold
Near threshold pion production experiments have been recently carried out and used to extract S–wave ππ scattering lengths. We emphasize here that at present these processes are related only at the tree level (and its first correction) in chiral perturbation theory. Higher order corrections (including loops) must be evaluated before rigorous claims concerning S–wave ππ scattering lengths can be...
متن کاملThe Reaction Πn → Ππn at Threshold in Chiral Perturbation Theory
In the framework of heavy baryon chiral perturbation theory, we give the chiral expansion for the πN → ππN threshold amplitudes D1 and D2 to quadratic order in the pion mass. The theoretical results agree within one standard deviation with the empirical values. We also derive a relation between the two threshold amplitudes of the reaction πN → ππN and the ππ S–wave scattering lengths, a0 and a0...
متن کاملRigorous pion - pion scattering lengths from threshold πN → ππN data
A new evaluation of the universal ππ scattering length relation is used to extract the ππ s-wave scattering lengths from threshold pion production data. Previous work has shown that the chiral perturbation series relating threshold pion production to ππ scattering lengths appears to converge well only for the isospin-2 case, giving a2 = −0.031±0.007m−1 π . A model-independent and data-insensiti...
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ژورنال
عنوان ژورنال: Physics Letters B
سال: 1972
ISSN: 0370-2693
DOI: 10.1016/0370-2693(72)90594-1