NLO+NLL Collider Bounds, Dirac Fermion and Scalar Dark Matter in the B-L Model

Abstract

Baryon and lepton numbers being accidental global symmetries of the Standard Model (SM), it is natural to promote them to local symmetries. However, to preserve anomaly freedom, only combinations of B-L are viable. In this spirit, we investigate possible dark matter realizations in the context of the $U(1)_{B-L}$ model: (i) Dirac fermion with unbroken B-L; (ii) Dirac fermion with broken B-L; (iii) scalar dark matter; (iv) two component dark matter. We compute the relic abundance, direct and indirect detection observables and confront them with recent results from Planck, LUX-2016, and Fermi-LAT and prospects from XENON1T. In addition to the well known LEP bound $M_{Z^{\prime}}/g_{BL} \gtrsim 7$ TeV, we include often ignored LHC bounds using 13 TeV dilepton (dimuon+dielectron) data at next-to-leading order plus next-to-leading logarithmic accuracy. We show that, for gauge couplings smaller than $0.4$, the LHC gives rise to the strongest collider limit. In particular, we find $M_{Z^{\prime}}/g_{BL} > 8.7$ TeV for $g_{BL}=0.3$. We conclude that the NLO+NLL corrections improve the dilepton bounds on the $Z^{\prime}$ mass and that both dark matter candidates are only viable in the $Z^{\prime}$ resonance region, with the parameter space for scalar dark matter being fully probed by XENON1T. Lastly, we show that one can successfully have a minimal two component dark matter model.