Y. A. Litvinov

 

Non-exponential two-body beta decay of stored hydrogen-like ions

 

The ion storage-cooler ring ESR at GSI, Darmstadt, coupled to a high-energy syn- chrotron SIS and a fragment separator FRS, is a unique tool for addressing two-body beta decays of stored and cooled highly-charged ions, i.e. bound-state beta decay and orbital electron-capture (EC). In such two-body beta decays, the monochro- matic (anti)neutrinos created in the electron- avour eigenstate are entangled with the recoiling daughter ions by the energy and momentum conservation. In course of the very rst measurements of the EC decay probability of hydrogen- like ions, it turned out that hydrogen-like 140Pr58+ and 142Pm60+ nuclides decay by about 50% faster than the corresponding helium-like ions. It will be shown that this result, albeit being somewhat surprising, can be understood within the framework of standard nuclear physics theory. By reducing the number of stored ions to less than four, each single ion can be continuously monitored with a time resolution of better than 100 ms. These experiments were conducted with both, hydrogen-like 140Pr58+ and 142Pm60+ ions. The time of each EC decay has been precisely determined. Several thousands of EC decays have been recorded. Superimposed on the expected exponential decrease of the number of EC decays as function of time, we observed a time modulation with a period of about 7 seconds for both systems. The observed e ect is meanwhile broadly discussed in literature. Some scenarios show that our observations could be attributed to the coherent creation of nite mass eigenstates of the electron neutrino in these two-body weak decays. It will be shown how this hypothesis of a special kind of "quantum beats" could be corroborated or disproved in other two- body weak decays. The present status of the experiments and some preliminary results will be presented. On leave from GSI Helmholtzzentrum fur Schwerionenforschung, 64291 Darmstadt, Germany 1 The ion storage-cooler ring ESR at GSI, Darmstadt, coupled to a high-energy syn- chrotron SIS and a fragment separator FRS, is a unique tool for addressing two-body beta decays of stored and cooled highly-charged ions, i.e. bound-state beta decay and orbital electron-capture (EC). In such two-body beta decays, the monochro- matic (anti)neutrinos created in the electron- avour eigenstate are entangled with the recoiling daughter ions by the energy and momentum conservation. In course of the very rst measurements of the EC decay probability of hydrogen- like ions, it turned out that hydrogen-like 140Pr58+ and 142Pm60+ nuclides decay by about 50% faster than the corresponding helium-like ions. It will be shown that this result, albeit being somewhat surprising, can be understood within the framework of standard nuclear physics theory. By reducing the number of stored ions to less than four, each single ion can be continuously monitored with a time resolution of better than 100 ms. These experiments were conducted with both, hydrogen-like 140Pr58+ and 142Pm60+ ions. The time of each EC decay has been precisely determined. Several thousands of EC decays have been recorded. Superimposed on the expected exponential decrease of the number of EC decays as function of time, we observed a time modulation with a period of about 7 seconds for both systems. The observed e ect is meanwhile broadly discussed in literature. Some scenarios show that our observations could be attributed to the coherent creation of nite mass eigenstates of the electron neutrino in these two-body weak decays. It will be shown how this hypothesis of a special kind of "quantum beats" could be corroborated or disproved in other two- body weak decays. The present status of the experiments and some preliminary results will be presented. On leave from GSI Helmholtzzentrum fur Schwerionenforschung, 64291 Darmstadt, Germany 1 The ion storage-cooler ring ESR at GSI, Darmstadt, coupled to a high-energy syn- chrotron SIS and a fragment separator FRS, is a unique tool for addressing two-body beta decays of stored and cooled highly-charged ions, i.e. bound-state beta decay and orbital electron-capture (EC). In such two-body beta decays, the monochro- matic (anti)neutrinos created in the electron- avour eigenstate are entangled with the recoiling daughter ions by the energy and momentum conservation. In course of the very rst measurements of the EC decay probability of hydrogen- like ions, it turned out that hydrogen-like 140Pr58+ and 142Pm60+ nuclides decay by about 50% faster than the corresponding helium-like ions. It will be shown that this result, albeit being somewhat surprising, can be understood within the framework of standard nuclear physics theory. By reducing the number of stored ions to less than four, each single ion can be continuously monitored with a time resolution of better than 100 ms. These experiments were conducted with both, hydrogen-like 140Pr58+ and 142Pm60+ ions. The time of each EC decay has been precisely determined. Several thousands of EC decays have been recorded. Superimposed on the expected exponential decrease of the number of EC decays as function of time, we observed a time modulation with a period of about 7 seconds for both systems. The observed e ect is meanwhile broadly discussed in literature. Some scenarios show that our observations could be attributed to the coherent creation of nite mass eigenstates of the electron neutrino in these two-body weak decays. It will be shown how this hypothesis of a special kind of "quantum beats" could be corroborated or disproved in other two- body weak decays. The present status of the experiments and some preliminary results will be presented.