Leptophobic Z ' in heterotic-string derived models

Abstract The CDF Collaborationʼs recent observation of an excess of events in the Wjj channel may be attributed to a new Abelian vector boson with suppressed couplings to leptons. While D0 finds no evidence of an excess, the CDF data provide an opportunity to revisit an old result on leptophobic Z ′ in heterotic-string derived models. We re-examine the conditions for the existence of a leptophobic U ( 1 ) symmetry, which arises from a combination of the U ( 1 ) B − L symmetry and the horizontal flavour symmetries, to form a universal U ( 1 ) symmetry. While the conditions for the existence of a leptophobic combination are not generic, we show that the left–right symmetric free fermionic heterotic-string models also admit a leptophobic combination. In some cases the leptophobic U ( 1 ) is augmented by the enhancement of the colour group, along the lines of models proposed by Foot and Hernandez.