Abstract
Starting from a general effective Lagrangian for lepton flavor violation (LFV) in quark-lepton transitions, we derive constraints on the effective coefficients from the high-mass tails of the dilepton processes pp rightarrow ell _k ell _l (with kne l). The current (projected) limits derived in this paper from LHC data with 36~mathrm {fb}^{-1} (3~mathrm {ab}^{-1}) can be applied to generic new physics scenarios, including the ones with scalar, vector and tensor effective operators. For purely left-handed operators, we explicitly compare these LHC constraints with the ones derived from flavor-physics observables, illustrating the complementarity of these different probes. While flavor physics is typically more constraining for quark-flavor violating operators, we find that LHC provides the most stringent limits on several flavor-conserving ones. Furthermore, we show that dilepton tails offer the best probes for charm-quark transitions at current luminosities and that they provide competitive limits for tauonic brightarrow d transitions at the high-luminosity LHC phase. As a by-product, we also provide general numerical expressions for several low-energy LFV processes, such as the semi-leptonic decays Krightarrow pi ell ^{pm }_k ell ^{{mp }}_l, Brightarrow pi ell ^{pm }_k ell ^{{mp }}_l and Brightarrow K^{(*)} ell ^{pm }_k ell ^{{mp }}_l.
Highlights
From a theoretical perspective, lepton flavor violation (LFV) is predicted in various beyond the SM (BSM) scenarios, such as the ones involving sterile neutrinos [1,2,3], extended Higgs sectors [4,5], Z bosons [6] and leptoquarks [7,8]
Under the assumption of heavy new physics states, the low-energy LFV data can be described by means of an Effective Field Theory (EFT), with the information on the underlying dynamics encoded in effective coefficients that can be probed experimentally
We compare the constraints on left-handed operators derived in Sect. 2 from high- pT data with the ones obtained from flavor-physics observables, as discussed in Sect
Summary
LFV is predicted in various BSM scenarios, such as the ones involving sterile neutrinos [1,2,3], extended Higgs sectors [4,5], Z bosons [6] and leptoquarks [7,8]. Recasts of resonant searches in the invariant mass tails of the pp → − + and pp → ±ν processes have been used to derive stringent limits on various new physics models [21,22,23,24] These constraints turn out to be complementary to the ones coming from flavor physics observables and, in particular, they have been useful to identify the viable solutions of the LFUV anomalies observed in B-meson decays [25,26]. 3 we derive constraints, by using flavor physics observables, on a specific scenario with purely left-handed operators, which are compared with the high- pT limits we have derived in Sect.
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