Hunting for contact interactions at HERA with polarized lepton and proton beams

Abstract

We explore the discovery and analysis potentials of the HERA collider, with and without polarized beams, in search for electron-quark contact interactions in the neutral current channel. We find that the sensitivity to contact interactions when both beams are polarized is similar to the unpolarized case, and is better than in the case where one has only lepton polarization. We emphasize that the measurement of spin asymmetries in such a polarized context could give some crucial informations on the chiral structure of these postulated new interactions. The experimental conditions are carefully taken into account.

Spin asymmetries in squark and gluino production at polarized hadron colliders

“…So far, there is very little theoretical work in this direction. The only comprehensive studies of new physics searches in polarized hadronic collisions to date concern the effects of contact interactions [13,14] and of new gauge bosons [15] on spin asymmetries at RHIC and HERA. It was found that polarization information can yield vital insights, such as discriminating different types of contact interactions that yield identical signatures at unpolarized colliders.…”

Search for scalar leptoquarks with polarized protons (and neutrons) at HERA and future ep(n) machines

“…According to our previous experience [7] we know that in general the Parity Violating (PV) two spin asymmetries exhibit stronger sensitivities to new chiral effects than the single spin asymmetries. Then we consider the case where the e and p (or neutrons) beams are both polarized.…”

“…Some other observables, defined in [7], could be used to go further into the separation of the models. However the sensitivities of these asymmetries are rather weak, and they can be useful only for some particularly favorable values of the parameters (M,λ).…”

“…Then some ambiguities can remain. Nevertheless, the use of additional asymmetries, like the huge number of charge and PC spin asymmetries that one can define with lepton plus nucleon polarizations [7], should be very useful for the determination of the chiral structure of the new interaction.…”

Beyond the standard model physics at RHIC in polarized pp collision

“…Helicity-selected matrix elements have been theoretically obtained in LO not only for the standard model but also for the contact interaction. In case' of Drell-Yan process, corresponding matrix elements were obtained from Virey's calculation for DIS by crossing [8]. A weighted mean method is applied in order to extract spin asymmetries using "unpolarized" event generator PYTHIA.…”