Stringy origin of Tevatron Wjj anomaly

TL;DR

This paper proposes that the Tevatron Wjj anomaly can be explained by a low mass string theory involving a leptophobic Z' boson, which naturally produces the observed dijet excess through string-inspired gauge structures.

Contribution

It introduces a string theory-based model with a leptophobic Z' that accounts for the Wjj anomaly and explores its phenomenological implications at colliders.

Findings

The model explains the Wjj excess via a leptophobic Z' boson.

Constraints from LEP data are satisfied with small Z-Z' mixing.

The heavier Z" boson could be detected at the LHC.

Abstract

The invariant mass distribution of dijets produced in association with W bosons, recently observed by the CDF Collaboration at Tevatron, reveals an excess in the dijet mass range 120-160 GeV/c^2, 3\sigma beyond Standard Model expectations. We show that such an excess is a generic feature of low mass string theory, due to the production and decay of a leptophobic Z', a singlet partner of SU(3) gluons coupled primarily to the U(1) baryon number. In this framework, U(1) and SU(3) appear as subgroups of U(3) associated with open strings ending on a stack of 3 D-branes. In addition, a minimal model contains two other stacks to accommodate the electro-weak SU(2) \in U(2) and the hypercharge U(1). Of the three U(1) gauge bosons, the two heavy Z' and Z" receive masses through the Green-Schwarz mechanism. For a given Z' mass, the model is quite constrained. Fine tuning three of its free parameters is just sufficient to simultaneously ensure: a small Z-Z' mixing in accord with the stringent LEP data on the $Z$ mass; very small (less than 1%) branching ratio into leptons; and a large hierarchy between Z" and Z' masses. The heavier neutral gauge boson Z" is within the reach of LHC.