Improved Limit on the Branching Ratio of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>μ</mml:mi><mml:mi /><mml:mo>→</mml:mo><mml:mi /><mml:mi mathvariant="italic">e</mml:mi></mml:math>Conversion on Lead

Honecker, W.; Dohmen, C.; Haan, H.; Junker, D.; Otter, G.; Starlinger, M.; Wintz, P.; Hofmann, J. I.; Bertl, W.; Egger, J.; Krause, B.; Eggli, S.; Engfer, R.; Findeisen, C.; Hermes, E.A.; Kozłowski, T.; Niebuhr, C.; Pruys, H.; Schaaf, A. van der

doi:10.1103/physrevlett.76.200

Cited by 136 publications

(117 citation statements)

References 17 publications

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“…3 The choice of a larger interval for the complex angles would increase the range of the entries of Y ν , and thus would lead to augmented contributions to the considered cLFV observables; however, this would also increase the other (muonic) cLFV observables which, given the present bounds, would in turn lead to the exclusion of these regimes. 4 In our numerical analysis, we rely on the results of [43], where the most relevant constraints are translated into bounds on the (U 2 , M ) planes, as well as on the splitting δM between the two heaviest states (in the range from ∼ 10 −4 eV to 1 keV).…”

Section: Constraints On Sterile Fermionsmentioning

confidence: 93%

“…[1]). Numerous experiments have already set strong bounds on the corresponding rate [2][3][4], and the experimental sensitivity to CR(µ − e, N) is expected to significantly improve in the near future [5][6][7][8][9]. Recently, another interesting observable has been proposed [10], which is the Coulomb-enhanced decay of a muonic atom into a pair of electrons, µ − e − → e − e − .…”

Section: Jhep02(2016)083mentioning

confidence: 99%

See 1 more Smart Citation

Impact of sterile neutrinos on nuclear-assisted cLFV processes

Abada

Romeri

Teixeira

2016

J. High Energ. Phys.

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We discuss charged lepton flavour violating processes occurring in the presence of muonic atoms, such as muon-electron conversion in nuclei CR(µ − e, N), the (Coulomb enhanced) decay of muonic atoms into a pair of electrons BR(µ − e − → e − e − , N), as well as Muonium conversion and decay, Mu − Mu and Mu → e + e − . Any experimental signal of these observables calls for scenarios of physics beyond the Standard Model. In this work, we consider minimal extensions of the Standard Model via the addition of sterile fermions, providing the corresponding complete analytical expressions for all the considered observables. We first consider an "ad hoc" extension with a single sterile fermion state, and investigate its impact on the above observables. Two well motivated mechanisms of neutrino mass generation are then considered: the Inverse Seesaw embedded into the Standard Model, and the νMSM. Our study reveals that, depending on their mass range and on the active-sterile mixing angles, sterile neutrinos can give significant contributions to the above mentioned observables, some of them even lying within present and future sensitivity of dedicated cLFV experiments. We complete the analysis by confronting our results to other (direct and indirect) searches for sterile fermions.

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Section: Constraints On Sterile Fermionsmentioning

confidence: 93%

Section: Jhep02(2016)083mentioning

confidence: 99%

Impact of sterile neutrinos on nuclear-assisted cLFV processes

Abada

Romeri

Teixeira

2016

J. High Energ. Phys.

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“…To lift this degeneracy the observation of a third µ → e transition process would be necessary: for instance R T i µ→e at PRISM or µ → eee at µ3e − P SI [55]. Alternatively, the measurement of two rates might be incompatible with the upper bound or measurement of a third one, which would rule out the scenario 9 . Similarly the measurement of a single rate, together with the upper bound or measurement of another one, could exclude this scenario for ranges of m N values (eventually excluding the whole mass range).…”

Section: Ratios Of Rates Involving One Same Flavour Transitionmentioning

confidence: 99%

“…Current experimental bounds on the various rates are expected to be improved in the near future by a long series of new experiments. In particular, µ → e conversion processes [1] will become especially competitive, as the sensitivities for various nuclei are expected to be improved by several orders of magnitude, R T i µ→e 10 −18 [2,3] , ( as compared to the present sensitivities R T i µ→e < 4.3 × 10 −12 [7] , (1.3) R Au µ→e < 7 × 10 −13 [8] , (1.4) R P b µ→e < 4.6 × 10 −11 [9] .…”

Section: Introductionmentioning

confidence: 99%

Muon conversion to electron in nuclei in type-I seesaw models

Alonso

Dhen

Gavela

et al. 2013

J. High Energ. Phys.

171

175

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We compute the µ → e conversion in the type-I seesaw model, as a function of the right-handed neutrino mixings and masses. The results are compared with previous computations in the literature. We determine the definite predictions resulting for the ratios between the µ → e conversion rate for a given nucleus and the rate of two other processes which also involve a µ − e flavour transition: µ → eγ and µ → eee. For a quasi-degenerate mass spectrum of right-handed neutrino masses -which is the most natural scenario leading to observable rates-those ratios depend only on the seesaw mass scale, offering a quite interesting testing ground. In the case of sterile neutrinos heavier than the electroweak scale, these ratios vanish typically for a mass scale of order a few TeV. Furthermore, the analysis performed here is also valid down to very light masses. It turns out that planned µ → e conversion experiments would be sensitive to masses as low as 2 MeV. Taking into account other experimental constraints, we show that future µ → e conversion experiments will be fully relevant to detect or constrain sterile neutrino scenarios in the 2 GeV−1000 TeV mass range.

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“…This limit could be further improved by future experiments, at PSI (SIN-DRUM II experiment), which aims to push the sensitivity of the branching ratio R µe + to 10 −14 , and at Brookhaven (MECO experiment) [28] with expected sensitivity about three to four orders of magnitude below the existing experimental limits [28,29]. Traditionally the exotic µ − → e ± processes were searched by employing medium heavy (like 48 Ti and 63 Cu) [13,16] or very heavy (like 208 Pb and 197 Au) [14,15,16] targets. For technical reasons the MECO target has been chosen to be the light nucleus 27 Al [28].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2002

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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.

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Improved Limit on the Branching Ratio ofμ→eConversion on Lead

Cited by 136 publications

References 17 publications

Impact of sterile neutrinos on nuclear-assisted cLFV processes

Impact of sterile neutrinos on nuclear-assisted cLFV processes

Muon conversion to electron in nuclei in type-I seesaw models

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

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