MANIFESTATION OF AN EXCITED ELECTRON IN e⁺e¯ → γγ REACTION

Abstract

The differential cross section and some polarization observables have been calculated for the e⁺e¯ → γγ reaction taking into account the contribution of the excited electron. The spin correlation coefficients were calculated for the case when both beams are polarized. We consider two approaches for the excited electron contribution: the eу → γγ contact interaction and the exchange of the excited electron in t- and u-channels. Numerical estimations are given for the excited electron contribution to the differential cross section and spin correlation coefficients for vari-ous values of the electron beam energy and excited electron mass.

Is the Non-Pointness of the Electron Observable in e+e− Annihilation at Center-of-Mass Energies 55–207 GeV?

“…The exchange of the excited electron does not produce non-zero polarization effects in the case of only one polarized beam [146], at least in the lowest order of perturbation theory. This is because the reaction that produces the excited electron conserves space parity, which can be inferred from the expression for the Lagrangian (28).…”

“…From the other side, contact interaction affects the polarization observables in reaction e + e − → γγ(γ) when the initial particles are polarized. In the general case, the contact interaction violates space parity [146]. Therefore, non-zero observables arise only when one of the beams is polarized.…”

About the polarized τ-lepton radiative decay

“…It is expressed in terms of complex vector v(t) , t = (q + k) 2 , and axial-vector a(t) form factors which describe, on the phenomenological level, the hadronization process of the charged weak currents [9][10][11][12][13][14][17][18][19]]…”

“…As we mentioned above, the decay width does not depend on any angles if τ lepton is unpolarized. In this case, we can define the differential decay width and the Stokes parameters of a photon [12,17,18]. But there is additional 3-vector in the rest frame of the polarized τ which is just its polarization S µ = (0, n), n 2 = 1.…”

“…(12)(13)(14)(15) in Ref. [18] To find these quantities for the restricted photon phase space, we have to calculate the following integrals (see also Eq. ( 11))…”