High- $$p_T$$ p T dilepton tails and flavor physics

Abstract

We investigate the impact of flavor-conserving, non-universal quark-lepton contact interactions on the dilepton invariant mass distribution in p p → + − processes at the LHC. After recasting the recent ATLAS search performed at 13 TeV with 36.1 fb −1 of data, we derive the best up-to-date limits on the full set of 36 chirality-conserving four-fermion operators contributing to the processes and estimate the sensitivity achievable at the HL-LHC. We discuss how these high-p T measurements can provide complementary information to the low-p T rare meson decays. In particular, we find that the recent hints on lepton-flavor universality violation in b → sμ + μ − transitions are already in mild tension with the dimuon spectrum at high-p T if the flavor structure follows minimal flavor violation. Even if the mass scale of new physics is well beyond the kinematical reach for on-shell production, the signal in the high-p T dilepton tail might still be observed, a fact that has been often overlooked in the present literature. In scenarios where new physics couples predominantly to third generation quarks, instead, the HL-LHC phase is necessary in order to provide valuable information.

Flavourful Z ′ models for R K ∗ $$ {R}_{K^{\left(\ast \right)}} $$

“…where 1/3 is quite a stringent limit, for example the usual CKM inspired expectation (V ′ † dL ) 1/2 32 ∼ λ ∼ 0.22 is already not viable, in agreement with the general results in [48]. However large mixings such as, for example, (s Q 34 ) ∼ 1/ √ 2 and (V ′ † dL ) 1/2 32 ∼ 0.5, would imply M ′ Z ∼ 3.2 TeV, just above the current limit.…”

Lepton-flavor universality violation in R K and R D ∗ $$ {R}_{D^{{}_{\left(\ast \right)}}} $$ from warped space

“…8 This issue has been thoroughly analyzed in refs. [54,79]. In particular, using the results from ref.…”

Theory overview on FCNC B-decays

“…In this context, impact of the contact interactions (due to the heavy scale) on the tails of dilepton invariant mass distribution in p p → + − has been studied in Ref. [38]. The limits obtained in this way are used to derive bounds on class of models which aim to solve the b → s anomalies.…”

“…Since the implied scale of new physics is rather low [34], the main challenge is to reconcile it with the non-observation of related signals in (other) flavour changing processes (e.g. [35]), electroweak precision observables, τ decays [36,37], and high-p T searches [15,38].…”