Disentangling QCD and new physics in D → πℓ+ℓ−

Abstract

In this paper we consider the decay D+ → π+ℓ+ℓ−, addressing in particular the resonance contributions as well as the relatively large contributions from the weak annihilation diagrams. For the weak annihilation diagrams we include known results from QCD factorisation at low q2 and at high q2, adapting the existing calculation for B decays in the Operator Product Expansion. The hadronic resonance contributions are obtained through a dispersion relation, modelling the spectral functions as towers of Regge-like resonances in each channel, as suggested by Shifman, imposing the partonic behaviour in the deep Euclidean. The parameters of the model are extracted using e+e− → (hadrons) and τ → (hadrons) + ντ data as well as the branching ratios for the resonant decays D+ → π+R(R → ℓ+ℓ−), with R = ρ, ω, and ϕ. We perform a thorough error analysis, and present our results for the Standard Model differential branching ratio as a function of q2. Focusing then on the observables FH and AFB, we consider the sensitivity of this channel to effects of physics beyond the Standard Model, both in a model independent way and for the case of leptoquarks.

Probing for new physics with rare charm baryon (Λc, Ξc, Ωc) decays

“…As in semileptonic rare b-decays, a dispersion relation plus e + e − → hadrons-data [21] can provide an alternative resonance parameterization to (2.4). It also invokes factorization and fudge factors a M , however, avoids double-counting by extracting the sum of long-and short-distance contributions experimentally, see also [22] and [23] for application to D → ρ and D → π decays, respectively. Since in charm, unlike in beauty, C R 9 dominates over the SM short-distance contribution, see figure 9, and the parameterizations yield similar distributions in D-decays within their sizable, notably, phase-induced uncertainties [8,23], we employ the significantly simpler ansatz (2.5) for null test analyses in charmed baryons.…”

Prospects for discovering new physics in charm sector through low-energy scattering processes $e^-p\to e^- (μ^-)Λ_c$

“…Refs. [9,10], where the hadronic resonance contributions are obtained through a dispersion relation, modeling the spectral functions as towers of Regge-like resonance in each channel and imposing the partonic behavior in the deep Euclidean.…”

Null test searches for BSM physics with rare charm decays

“…The experimental and theoretical status of rare charm decays is presented in Ref. [5] and increasing and ongoing research interest [1,2,[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] manifests the importance of progress in the field.…”