Rare Kaon DecayK+→π+l+l

Abstract

A new treatment is proposed for the rare kaon decays K'^ -^ TT"^e'^e~ and AT"*"-•7r"*"/x"*"/x~. Although the individual rates seem impossible to predict accurately at present because of large cancellations of different amplitudes, it is pointed out that a measurement of certain ratios involving these decays could provide interesting information on the weak nonleptonic interaction.PACS numbers: 13.20. Eb, 13.25.+ m, 13.40.Hq In recent years, there has been renewed interest in the physics of rare kaon decays, mainly because of their potential to indicate deviations from the standard electroweak model, in particular in the new generation of remarkably sensitive experiments currently being performed or planned (for recent reviews, see, e.g., Walter^ and Littenberg^). It should be noted, however, that there are also problems within the standard model concerning the nonleptonic weak interaction that still lack a satisfactory solution. The foremost of these concerns the structure of the strangenesschanging (A5= 1 or 2) weak Hamiltonian, in particular the origin of the A/= y rule.The generic problem, e.g., the calculation of the K-TT transition induced by the interplay between the strong and electroweak interaction, consists of three components in the commonly accepted Wilson expansion method: (a) identification of the relevant local field operators, (b) calculation of the quantumchromodynamics-corrected Wilson coefficients, and (c) evaluation of the matrix elements of the operators between hadronic states. To this should be added (outside the Wilson expansion) the problem of (d) estimating the long-distance effects. In a previous pa-per^ it was shown how a study of the rare kaon decays Ki--^ l^Ty (l = e or fji) could shed some light on these questions, in particular the role of the so-called penguin operators first introduced by Shifman, Vainshtein, and Zakharov."^ In this article we show that interesting information can be obtained from the decays/^^ -77^/+/-.

The e-ASTROGAM mission

“…• Monochromatic photons at MeV energies may result from DM annihilation to quarkonium [120], as well as step-like features from the decay b → s + γ or b → b + γ, where b is a hypothetical 4th generation quark [28]. Another possibility is the decay of DM candidates like the gravitino, which has motivated line searches with the Fermi Large Area Telescope down to energies of 100 MeV [21].…”

QED radiative corrections to the decay π0→e+e-

“…Usually this constant, containing the nontrivial dynamics of the process, is calculated within different models describing the form factor F π (k 2 , q 2 ) [2,6,7,8]. However, it has recently been shown in [2] that this constant may be expressed in terms of the inverse moment of the pion transition form factor given in symmetric kinematics of spacelike photons…”

“…1a) corresponding to the conversion of the pion through two virtual photons into an electronpositron pair. The normalized branching ratio is given by [4,5,6]…”

Gamma-ray triangles: A possible signature of asymmetric dark matter in indirect searches

“…This new signal adds to the list of sharp spectral features known to arise in particle physics scenarios (for a phenomenological analysis, see Ref. [20]): gamma-ray lines [21][22][23], internal electromagnetic bremsstrahlung [24][25][26] and gamma-ray boxes [27].…”