$P_5^{\mathrm{\prime }}$ Anomaly for Top: $t{Z}^{\mathrm{\prime }}$ Production at LHC

The $P_5^{\mathrm{\prime }}$ anomaly uncovered by the LHCb experiment in $B\to K^{\ast }\mu \mu$ angular observables has motivated a possible $Z^{\mathrm{\prime }}$ boson that couples to left-handed $b\to s$ transitions, where a model would be gauged $L_\mu - L_\tau$symmetry,butdirectsearchforsucha$Z’$ is not promising. Less constrained is an analogous $Z^{\mathrm{\prime }}$ coupling to right-handed $t\to c$ transitions. Motivated by this, we study $cg\to t{Z}^{\mathrm{\prime }}$ associated production at LHC, both for a generic model, and in $L_{\mu }-L_{\tau }$ with a vector-like U quark. We also study $c\bar{c}\to Z^{\mathrm{\prime }}$ production that exists within the model. Both processes can be probed already with LHC Run 2 data, all the way up to the HL-LHC with discovery potential.