✍ Scribed by G. Pòcsik
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The effects of neutral weak currents are discussed in e+e-annihilation into final states such as pL+pL-, e+e-, rr+n-, many hadrons and also in the one particle inclusive production. According to current gauge models these weak effects which are manifested as various asymmetries, turn out to be around 10 "/ in the energy range of PEP and PETRA. In identifying weak effects polarized incident beams are advantageous, in particular, the longitudinally polarized beams select parity violating asymmetries.
In the past few years several proposals [-, 7 47,481 have been made for detecting asymmetries coming from neutral weak currents in efe-collisions. Since important experimental evidence has been found in favor of the neutral weak current [I, 21. the experimental investigation of these weak asymmetries will provide further statistics as well as essential details on the structure of neutral weak currents allowing comparisons of the results with predictions of several theoretical models. In general, the photon-neutral weak boson Z interference influences the &em annihilation in such a way that characteristic asymmetries should grow with the center-of-mass energy squared, therefore the high energy region is most promising for finding effects caused by Z. In gauge models, like the Weinberg-Salam, Lee-Prentki-Zumino ones, etc., the weak asymmetries are about 10:: in the total center-of-mass energy range of 20-40 GeV.
From the theoretical point of view the simplest treatments concern final states of p'p-. e+ep which avoid all the hadronic complications. Here, weak effects cause forward-backward and charge asymmetries. as well as outgoing particles that appear with nonvanishing average helicities due to y-Z interference. Transversely or longitudinally polarized incident beams make the separation of weak terms easier and sometimes they enhance the effects. In particular, longitudinally polarized beams identify parity violating terms in the cross section.
The kinematics of y-Z interference has been calculated also for two hadrons, many hadt-on final states and one particle inclusive production. The measurability depends crucially upon the luminosity and timelike electromagnetic form factors at high energies. Furthermore, at present the theoretical estimates for weak effects are rather uncertain for one particle inclusive production through &e-annihilation * Work support4 by the Energy Research and Development Administration.
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