Spin asymmetries in one-jet production at RHIC with polarized proton beams: the effects of a hadrophilic Z′

Abstract

We show that the measurement of some parity violating asymmetry in the production of a large E T jet could reveal the presence of a new hadrophilic Z ′ such as the one recently introduced to interpret possible departures from the Standard Model predictions both at LEP and at CDF. Such a measurement could be performed within a few years by the RHIC Spin Collaboration (RSC) using the Relativistic Heavy Ion Collider (RHIC) as a polarized proton-proton collider.

Weak corrections to four-parton processes

“…Notice that subprocesses (5), (6),(9) and(10)are CKM suppressed in our diagonal approximation through O(α S α EW ).…”

“…(Notice that QED corrections, just like QCD ones, are not subject to Sudakov enhancement.) Furthermore, physics Beyond the Standard Model (BSM), if due to right-handed weak currents [6], contact interactions or compositeness [7] or new massive gauge bosons W ′ , Z ′ [8,9] may well manifest itself in deviations from the SM in jet quantities (which eventually emerge as observables of parton-parton collisions after hadronisation: see [10]- [17] for definitions and reviews of standard algorithms for hadronisation and jet evolution), such as jet transverse energy E T or di-jet invariant masses M jj . The lower bounds on typical W ′ , Z ′ masses from direct searches at Tevatron are model dependent but are typically around 500 − 600 GeV [18], whilst the LHC can access such massive gauge bosons with masses up to 4 − 4.5 TeV [19].…”

Sensitivity to a new right-handed charged current in polarized hadronic collisions at RHIC

“…The standard A P V LL , which is bigger than the corresponding one in p p collisions, is shown for comparison. The error bars correspond to the statistical error for a degree of polarization P = 70% (see [13,14]) and an integrated luminosity of 800 pb −1 which can be achieved in a few months running, the systematic error being negligible [17]. We have chosen an E T region where these errors are small : the range between 60 GeV and 100 Gev will dominate the analysis which follows.…”

“…Therefore, in case of W (W ′ ) exchanges, there is a partial cancellation in the u∆d + d∆u term. This cancellation is much less important in case of Z • (or neutral Z ′ ) exchanges where the combination u∆u + d∆d dominates in the corresponding formula (see [13]) thanks to the dominance ii). Note that this partial cancellation is somewhat compensated by the maximal PV in eq.…”

“…Since, in the context of hadronic collisions it is quite hopeless to analyze the net helicity of an outgoing particle or jet, polarized beams are needed to build an initial-state spin asymmetry. Indeed, we have shown recently that, in polarized pp collisions, the presence of a hadrophilic Z ′ [13] and/or a new PV contact interaction between quarks [14] could yield some deviations from the spin asymmetry in one-jet inclusive production which is due to SM electroweak (EW) bosons exchanges.…”