Related papers: Long vs. short distance dispersive two-photon K_L …

We present a full account of the two-loop electroweak, two-photon mediated short-distance dispersive $K_L \to\mu^+\mu^-$ decay amplitude. QCD corrections change the sign of this amplitude and reduce it by an order of magnitude. Thus, the…

A new analysis of the long-distance two-photon dispersive amplitude of K_L -> mu^+ mu^- is presented. We introduce a phenomenological parameterization of the K_L -> gamma^* gamma^* form factor, constrained at low energies by K_L -> gamma…

The dispersive two-photon contribution to the K_L --> mu+ mu- decay amplitude is analyzed, using chiral perturbation theory techniques and large-N_C considerations. A consistent description of the decays Pi^0 --> e+ e-, Eta --> mu+ mu- and…

We present a theoretical framework within which both the real and imaginary parts of the complex, two-photon exchange amplitude contributing to $K_L\rightarrow\mu^+\mu^-$ decay can be calculated using lattice QCD. The real part of this…

We propose a lattice-QCD-suitable framework for computing the two-photon long-distance contribution to the complex $K_{\rm L}\rightarrow\mu^+\mu^-$ decay amplitude, where QED is treated perturbatively in the continuum and infinite-volume.…

The interplay between short- and long-distance contributions to the K_L-->mu+ mu- decay amplitude is analyzed. The long-distance piece is estimated using chiral perturbation theory techniques and large-N_C considerations, leading to a…

An amplitude analysis of the $B^{0}\to K^{*0}\mu^+\mu^-$ decay is presented using a dataset corresponding to an integrated luminosity of $4.7$ fb$^{-1}$ of $pp$ collision data collected with the LHCb experiment. For the first time, the…

In this contribution, we present recent progress from the RBC/UKQCD collaboration on the first calculation of the long-distance two-photon contribution to the decay amplitude of a long-lived kaon into a pair of charged muons.

We study the long-distance contribution to $B_s\to\mu^+\mu^-$ decay, which is generated by the two-photon intermediate state via $B_s\to\gamma^*\gamma^*\to\mu^+\mu^-$ transition. It is found that the dispersive two-photon amplitude can…

We compute the complex, long-distance two-photon-exchange amplitude which contributes to the rare $K_{\rm L}\rightarrow\mu^+\mu^-$ decay from lattice QCD. We use a $24^3\times 64$ physical-pion-mass gauge field ensemble at an inverse…

A measurement of the phase difference between the short- and long-distance contributions to the $B^{+}\to K^{+}\mu^{+}\mu^{-}$ decay is performed by analysing the dimuon mass distribution. The analysis is based on $pp$ collision data…

Two pion Decays of K mesons, K_L-K_S mass difference, two photon decay and the Dalitz decays of K_L are studied systematically by assuming that their amplitude can be described in terms of a sum of short distance and long distance…

We present a lattice-QCD calculation of the long-distance two-photon contribution to the decay amplitude of a long-lived kaon to a pair of muons on a $24^3\times 64$ physical-pion-mass ensemble. In these proceedings, the theoretical…

We analyze data on $B\to K\mu^+\mu^-$ and $B\to K^*\mu^+\mu^-$ decays in the whole dilepton invariant mass spectrum with the aim of disentangling short- vs. long-distance contributions. The sizable long-distance amplitudes from $c \bar{c}$…

Motivated by new precise results on several $K_L$ decays, sensitive to the ${K_L \to \gamma \gamma}$ form factor, we present a new analysis of the $K_L\to \mu^+\mu^-$ long-distance amplitude based on a semi-phenomenological approach.…

The long-distance contribution via the two-photon intermediate state to the forward-backward asymmetries in decays K+ --> pi+ l+ l- (l=e and mu) has been studied within the standard model. In order to evaluate the dispersive part of the K+…

The short-distance behaviour of the hadronic light-by-light (HLbL) contribution to $(g-2)_{\mu}$ has recently been studied by means of an operator product expansion in a background electromagnetic field. The leading term in this expansion…

Rare K decays provide for very clean tests of the Standard Model, and are especially suited to search for New Physics signal. In this talk, recent progresses in the estimation of long-distance effects induced by light quarks in KL to pi0…

We develop a new method that allows us to deal with two-photon intermediate states in a lattice QCD calculation. We apply this method to perform a first-principles calculation of the $\pi^0 \rightarrow e^+ e^-$ decay amplitude. Both the…

Applying asymptotic expansions at threshold, we compute the two-loop QCD correction to the short-distance coefficient that governs the leptonic decay $\psi\to l^+ l^-$ of a S-wave quarkonium state and discuss its impact on the relation…