Abstract
We present a detailed analysis of the collider signatures of TeV-scale massive vector bosons motivated by the hints of lepton flavour non-universality observed in B-meson decays. We analyse three representations that necessarily appear together in a large class of ultraviolet-complete models: a colour-singlet (Z'), a colour-triplet (the U_1 leptoquark), and a colour octet (G'). Under general assumptions for the interactions of these exotic states with Standard Model fields, including in particular possible right-handed and flavour off-diagonal couplings for the U_1, we derive a series of stringent bounds on masses and couplings that constrain a wide range of explicit new-physics models.
Highlights
The hints of Lepton Flavour Universality (LFU) violation in semi-leptonic B decays, namely the deviations from τ/μ universality in b → c νdecays [1,2,3,4] and the deviations from μ/e universality in b → sdecays [5,6], are among the most interesting departures from the Standard Model (SM) reported by experiments in the last few years
Since the leptoquarks are predominantly produced via their strong couplings to gluons, the limits only depend on the branching ratios to the relevant final states
The high- pT phenomenology of models predicting a TeVscale SU (2)L singlet vector leptoquark which is able to account for the hints of LFU violations observed in B-meson decays is quite rich
Summary
The hints of Lepton Flavour Universality (LFU) violation in semi-leptonic B decays, namely the deviations from τ/μ (and τ/e) universality in b → c νdecays [1,2,3,4] and the deviations from μ/e universality in b → sdecays [5,6], are among the most interesting departures from the Standard Model (SM) reported by experiments in the last few years. The attempt to find a single beyond-the-SM (BSM) explanation for the combined set of anomalies has triggered intense theoretical activity, whose interest goes beyond the initial phenomenological motivation It has shed light on new classes of SM extensions that turn out to be very interesting per se and that have not been investigated in great detail so far, pointing to non-trivial dynamics at the TeV scale possibly linked to a solution of the SM flavour puzzle. In early EFT attempts, it was realised that a good mediator accounting for both sets of anomalies is a TeVscale U1 ∼ (3, 1, 2/3) vector leptoquark, coupled mainly to third-generation fermions [8,11] The effectiveness of this state as a single mediator accounting for all available lowenergy data has been clearly established in [28]. The purpose of this paper is to provide a comprehensive analysis of the high- pT constraints on the vector leptoquark U1 and what can be considered its minimal set of vector companions, namely a colour octet G ∼ (8, 1, 0), which we will refer to as the coloron, and a colour singlet Z ∼ (1, 1, 0)
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