The CDF dijet excess and Z'_{cs} coupled to the second generation quarks

TL;DR

This paper proposes a new Z' model that couples only to second-generation quarks, explaining the CDF Wjj excess while avoiding signals in gamma jj and Z jj channels, consistent with current experimental constraints.

Contribution

The paper introduces a Z' model with selective coupling to second-generation quarks, providing a novel explanation for the CDF dijet excess without conflicting with other collider data.

Findings

The model can explain the CDF Wjj excess with a sufficiently large gauge coupling.

It avoids constraints from other channels like gamma jj and Z jj.

The Z'-b-b coupling is set to zero to evade certain experimental bounds.

Abstract

Recently the CDF collaboration has reported the excess in the dijet invariant-mass distribution of the Wjj events, corresponding to a significance of 3.2 standard deviations. Considering the lack of similar excesses in the $\gamma jj$ and $Z jj$ events yet, we propose a new Z' model: Z' couples only to the second generation quarks. Single production of $\zsc$ as well as associated production with $W,\gamma, Z$ are mainly from the sea quarks. Only $W Z'$ production has additional contribution from one valence quark and one sea quark, which is allowed by CKM mixing. We found that if the new gauge coupling is large enough, marginally permitted by perturbativity, this new model can explain the observed CDF $Wjj$ anomaly as well as the lack of $\gm jj$ and $Z jj$ anomalies. Vanishing coupling of Z'-b-b protects this model from the constraint of p pbar ->WH -> l\nu b \bar{b}.