Test of lepton-flavour conservation in μ → e conversion on titanium

Dohmen, C.; Groth, K.-D.; Heer, B.; Honecker, W.; Otter, G.; Steinrücken, B.; Wintz, P.; Djordjadze, V.; Hofmann, J. I.; Kozłowski, T.; Playfer, S.; Bertl, W.; Egger, J.; Herold, W.; Krause, B.; Walter, H. K.; Engfer, R.; Findeisen, C.; Grossmann-Handschin, M.; Hermes, E.A.; Muheim, F.; Niebuhr, C.; Pruys, H.; Ricken, L.; Vermeulen, D.; Schaaf, A. van der

doi:10.1016/0370-2693(93)91383-x

Cited by 318 publications

(231 citation statements)

References 17 publications

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“…(47). Since m e c << p e we can consider the approximation p e ≈ E e /c, which is equivalent to neglecting the electron mass (m e ) in the kinematics of the reaction (13). For the explicit contribution of the excited states to the branching ratio we present in Table 2 the sum f S gs→f for each set of excited states of given |J f .…”

Section: Resultsmentioning

confidence: 99%

“…Up to now only upper limits have been set and the best limit found is for the 48 Ti nucleus at TRIUMF and PSI [11,12,15,16] yielding the values R µe + ≤ 4.6 × 10 −12 [15] and R µe + ≤ 4.4 × 10 −12 [13] ,…”

Section: Introductionmentioning

confidence: 99%

“…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%

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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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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2002

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“…[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%

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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“…In the aspect of experimental study, the current upper limits for muon-electron conversion in the nuclear field are given by the experiments at TRIUMF and PSI. The upper limit for gold is 7 × 10 −13 from the results of SINDRUM-II experiment at PSI [7], and upper limits for titanium are 4.3 × 10 −12 and 4.6 × 10 −12 from the results of SINDRUM-II [8] and an experiment at TRIUMF [9], respectively. The experimental results are getting closer to the level of thoeretical predictions and it is possible to reach the predicted level by improving the experimental sensitivity by only a few orders of magnitude.…”

Section: Introductionmentioning

confidence: 94%

Silicon Carbide Target for a Muon-Electron Conversion Search at J-PARC MLF

Nakatsugawa¹,

Aoki²,

Meigo³

et al. 2015

Proceedings of the 2nd International Symposium on Science at J-Parc — Unlocking the Mysteries of Life, Matter and the Universe

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It is considered that muon-electron conversion would be one of the most obvious evidence of the new physics beyond the standard model. An experimental search for muon-electron conversion in the nuclear field, DeeMe, is proposed at J-PARC Materials and Life Science Experimental Facility (MLF). DeeMe experiment will be carried out at a brand-new beamline (H-Line) which will be constructed at J-PARC MLF Muon Science Establishment (MUSE). The single event sensitivity achieved by the experiment with the current graphite production target of MUSE is estimated to be 1.2 × 10 −13 . This is smaller than the current upper limit but it is desirable to make the experiment more sensitive. In order to improve the sensitivity, it is planned to replace the graphite target with a silicon carbide (SiC) target. Thanks to the larger pion production rate and the larger muon capture rate of silicon nucleus, the number of muonic atoms formed in a SiC target is expected to be totally 6 times as large as in a graphite target and then the single event sensitivity for SiC target is estimated to be 2.1 × 10 −14 , nearly two orders of magnitudes below current upper limit. The current status of the preparation for the use of a SiC target is reported.

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Test of lepton-flavour conservation in μ → e conversion on titanium

Cited by 318 publications

References 17 publications

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

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

Impact of sterile neutrinos on nuclear-assisted cLFV processes

Silicon Carbide Target for a Muon-Electron Conversion Search at J-PARC MLF

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