The exotic double-charge exchange μ−→e+ conversion in nuclei

Abstract

The formalism for the neutrinoless (µ − , e + ) conversion is investigated in detail and the relevant nuclear matrix elements for light intermediate neutrinos in the case of 27 Al(µ − , e + ) 27 N a are calculated. The nucleus 27 Al is going to be used as a stopping target in the MECO experiment at Brookhaven, one of the most sensitive probes expected to reach a sensitivity in the branching ratio of the order 10 −16 within the next few years. The relevant transition operators are constructed utilizing a variety of mechanisms present in current gauge theories, with emphasis on the intermediate neutrinos, both light and heavy, and heavy SUSY particles. The nuclear wave functions, both for the initial state and all excited final states are obtained in the framework of 1s − 0d shell model employing the well-known and tested Wildenthal realistic interaction. In the case of the light intermediate neutrinos the transition rates to all excited final states up to 25 M eV in energy are calculated. We find that the imaginary part of the amplitude is dominant. The total rate is calculated by summing over all these partial transition strengths. We also find that the rate due to the real part of the amplitude is much smaller than the corresponding quantity found previously by the closure approximation.

Study of requirements and performances of the electromagnetic calorimeter for the Mu2e experiment at Fermilab

“…There is also the possibility to measure a similar process with ∆L = 2 [31]: 13) which violates both total lepton number and lepton flavor numbers L e and L µ and it is related to the the neutrinoless double β-decay. Some theoretical models indicate a rate of this reaction between 10 −12 and 10 −14 .…”

Nuclear(μ−,e+)conversion mediated by Majorana neutrinos

“…In Ref. [24] it was shown that the imaginary part of the amplitude dominates in the total branching ratio of the (µ − , e + ) conversion in 27 Al. In the next section we will demonstrate that the similar conclusion is valid for (µ − , e + ) conversion in 48 Ti.…”

“…[22] and then in Refs. [23,24]. In the previous studies of (µ − , e + ) conversion [9,15,16,18] the role of imaginary part was overlooked.…”

“…These two processes, conserving both total lepton number and lepton flavors, are the SM processes and have been well studied both theoretically and experimentally. The physics beyond the SM resides in yet non-observed channels of muon capture: muon-electron (µ − , e − ) and muonpositron (µ − , e + ) conversions in nuclei [15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30]:…”

Lepton Flavor Violating Higgs Boson Decays in Supersymmetric High Scale Seesaw Models

“…This picture changes when these masses are explained with a "see-saw" mechanism [8], that can be implemented in different ways [9][10][11][12]. The most popular of these mechanisms is Type-I see-saw [8], the small neutrino mass m ν ≈ Y Even with the assumption of universal soft masses at the GUT scale, the presence of Y ν in the RGE above M R can generate non trivial slepton mixings, hence relating cLFV to the neutrino problem [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] and GUT scenarios [29][30][31][32]. Other popular high scale seesaw mechanisms are Type II [33,34] and Type III [35,36] seesaw models.…”