Could HERA results have been predicted from semileptonic meson decays

The anomalous value of the tensor form factor in the kaon decay K → πeν and the destructive interference in pion decay π− → e−ν̄γ can be simultaneously described by admixture of a tensor interaction in the standard V -A one. It is shown that the same tensor interaction can describe recent HERA data at very large Q. 1 On leave from Centre for Space Research and Technologies, Faculty of Physics, University of Sofia, 1164 Sofia, Bulgaria, E-mail: [email protected] In the last years precision electroweak tests were performed at LEP, SLC and Tevatron. The announcements about deviations from the Standard Model (SM) have given rich possibility for theorists to speculate about the existence of a new physics. Unfortunately, the anomalies seam to have disappeared after taking into account the systematic errors more precisely [1] and appropriately modifying the structure functions [2]. Although some contradictions between the experimental data and the SM predictions exist, they are not paid a great attention. Nevertheless, the recent HERA results of H1 [3] and ZEUS [4] Collaborations have been met with a considerable interest. Now there are lots of theoretical works explaining the events excess at HERA by some new physics. In our work we will present an explanation of the deviation from the SM, observed in deep-inelastic scattering (DIS), by introducing a new effective (non contact) interaction present in the t-channel. Usually such interaction appears from the exchange of a new intermediate boson with a large mass M > MW/Z , which is almost negligible for small momentum transfers. However, if the new boson has approximately the same coupling constant with the fermions as γ, W and Z ones, then at high momentum transfer the strength of the new interaction will be comparable with the usual electroweak interactions. In case of ep → eX DIS at large Q, there exists a destructive interference between γ and Z exchange amplitudes and the expected cross section is substantially reduced. Therefore, in this case the additional contribution from the new interaction may be more definitely observed than in ep → eX DIS. Another characteristic feature of our approach is the suggestion about the existence of new vector bosons, different from the gauge ones W ′ and Z , and inducing the new interaction. The new vector particles are described by antisymmetric second-rank tensor field Tμν [5], and not by the vector Aμ. They correspond to the representation of the Lorentz group (1,0) + (0,1) in contrast to the widely used one (1/2,1/2) for the vector particles. As far as both of these nonequivalent representations for the description of vector particles exist in the Lorentz group on the same footing, we will assume, that besides the gauge bosons, there exists another kind of vector particles in Nature. Due to the particular Lorentz indices structure, the new vector bosons couple to the tensor currents Ψ̄RσμνΨL, Ψ̄LσμνΨR, while the usual gauge bosons interact with the vector currents Ψ̄LγμΨL, Ψ̄RγμΨR. This determines their main differences in the interactions with fermions. Note, that while the gauge bosons conserve the chiralities of the fermions, the new vector particles change fermion chiralities. This feature allows to distinguish their presence on the background of the standard electroweak interactions in polarization experiments and by analyzing the angular distributions. The helicity dependence of DIS cross section is parameterized by the variable y. As far as at large Q the contribution of the sea quarks into the cross section is negligible, and scattering occurs mainly on the valence quarks, the cross section of the charged-current (CC) process ep → ν̄X is suppressed by a factor (1 − y) in comparison with ep → νX due to chirality considerations. Therefore, the events excess, observed by H1 Collaboration 2 at large y, may indicate in favor of the presence of the new interactions leading to leptons and quarks spin flip. Those interactions can be chosen in the form