Rate amplification of the two photon emission from para-hydrogen toward the neutrino mass measurement
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Rate amplification of the two photon emission from para-hydrogen toward the neutrino mass measurement Takahiko Masuda1 · Hideaki Hara1 · Yuki Miyamoto1 · Susumu Kuma1,5 · Itsuo Nakano1 · Chiaki Ohae2,6 · Noboru Sasao1 · Minoru Tanaka4 · Satoshi Uetake3 · Akihiro Yoshimi1 · Koji Yoshimura1 · Motohiko Yoshimura3 © Springer International Publishing Switzerland 2015
Abstract We recently reported an experiment which focused on demonstrating the macrocoherent amplification mechanism. This mechanism, which was proposed for neutrino mass measurements, indicates that a multi-particle emission rate should be amplified by coherence in a suitable medium. Using a para-hydrogen molecule gas target and the adiabatic Raman excitation method, we observed that the two photon emission rate was amplified by a factor of more than 1015 from the spontaneous emission rate. This paper briefly summarizes the previous experimental result and presents the current status and the future prospect. Keywords Neutrino · Raman excitation · Para-hydrogen
Proceedings of the 6th International Conference on Trapped Charged Particles and Fundamental Physics (TCP 2014), Takamatsu, Japan, 1–5 December 2014. Takahiko Masuda
[email protected] 1
Research Core for Extreme Quantum World, Okayama University, Okayama 700-8530, Japan
2
Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
3
Research Center of Quantum Universe, Okayama University, Okayama 700-8530, Japan
4
Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan
5
Present address: Atomic, Molecular and Optical Physics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
6
Present address: Department of Engineering Science, University of Electro-Communications, Chofu, Tokyo 182-8585, Japan
T. Masuda et al.
1 Introduction As Higgs particle was observed [1, 2], all 17 elementary particles in the Standard Model of elementary particle physics have been found. One of the basic parameters, masses of the particles, also have been determined. But the absolute masses of neutrinos are not determined yet because of the smallness of their masses and the weakness of their interaction. In addition to the fact that unknown parameters of particles should be determined, the mass of neutrino possibly relates the matter-antimatter asymmetry in our universe [3], which is one of the most interesting objectives in the particle physics. Many experiments aiming to determine the neutrino mass are going on in the world. The current neutrinoless double beta decay experiments have sensitivity of ∼ 0.2 – 0.4 eV if the neutrino is Majorana particle [4–6]. The direct mass measurement using tritium beta decay has set an upper limit of m(νe ) < 2.05 eV [7] and the next experiment which is being constructed will have sensitivity of 0.2 eV [8]. The cosmological surveys, on the other hand, have set an upper limit on the total neutrino mass of 0.28 eV [9]. Our group has proposed a new method of the neutrino mass measurement, which uses atom or molecule targets
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