Neutron Bound β-decay-bob S. Paul 1, M. Berger 1, R. Emmerich 1, R. Engels 2, T. Faestermann 1, P. Fierlinger 3, M. Gabriel 1, F. Grünauer 1, E. Gutsmiedl 1, F. J. Hartmann 1, R. Hertenberger 4, A. Röhrmoser 5, S. Ruschel 1, J Schön 1, W. Schott 1, U. Schubert 1, A. Trautner 1, T. Udem 6, A. Ulrich 1 1 Physik-Department, TUM 2 Institut für Kernphysik, Forschungszentrum Jülich 3 Excellence Cluster Universe, TUM 4 Sektion Physik, LMU 5 Forschungs-Neutronenquelle Heinz- Maier- Leibniz 6 Max-Planck-Institut für Quantenphysik
Overview 1. Principle of the bound beta decay 2. The metastable 2s state of the H atom 3. Planned setup at FRM2 4. Simulations on background 5. Mockup experiments and options for detection 6. Current status and outlook
1. Principle of BOB With a small predicted branching ratio of the neutron ß decay, the reaction occurs. (L. L. Nemenov, Sov. J. Nucl. Phys. 31 (1980) 115) E kin of hydrogen: 325.7 ev predicted atomic states: 1s 83.2% 2s 10.4% Correlation between spins of the daughter products delivers new limits on g S and g T
1. Principle of BOB forbidden by SM
1. Principle of BOB W i (%) for various g S and g T config. i g S =0, g T =0 g S =0.1, g T =0 g S =0, g T =0.02 1 44.114 46.44 43.40 2 55.24 53.32 55.82 3 0.622 0.238 0.78 4 0. 0. 0.
1. Principle of BOB Beyond SM: right handed currents? Left-right symmetric V+A model: In standard model M 1 and M 2 are mass eigenstates of two new vector bosons W L and W R. They couple with left and right handed particles respectively with Ϛ being the mixing angle. Helicity of the neutriono:
1. Principle of BOB present values: goal: g S or g T upper limits can be reduced by a factor of 10 Neutrino helicity can be measured within 10-3
Overview 1. Principle of the bound beta decay 2. The metastable 2s state of the H atom 3. Planned setup at FRM2 4. Simulations on background 5. Mockup experiments and options for detection 6. Current status and outlook
energy 2. The metastable 2s state 2s metastable 2p Metastability of the 2s hydrogen atom Ly-alpha: 122nm 1s lifetime manipulation with electric field:
energy 2. The metastable 2s state 2s metastable 2p Metastability of the 2s hydrogen atom Ly-alpha: 122nm 1s flight length of 2.5cm lifetime manipulation with electric field: flight length of 20km
Overview 1. Principle of the bound beta decay 2. The metastable 2s state of the H atom 3. Planned setup at FRM2 4. Simulations on background 5. Mockup experiments and options for detection 6. Current status and outlook
3. Planned setup at FRM2
Overview 1. Principle of the bound beta decay 2. The metastable 2s state of the H atom 3. Planned setup at FRM2 4. Simulations on background 5. Mockup experiments and options for detection 6. Current status and outlook
4. Simulations on background simulated hydrogen density Background simulations observable neutrons solid angle hydrogens from decay number of hydrogens At the end of SR6
4. Simulations on background Flux of particles without any shielding outside the SR6
Overview 1. Principle of the bound beta decay 2. The metastable 2s state of the H atom 3. Planned setup at FRM2 4. Simulations on background 5. Mockup experiments and options for detection 6. Current status and outlook
5. Mockup experiments General test setup for spin state detection H-2s detection chamber coated with alkali halides such as CsI -> high QE for photo effect. detector efficiency can be in the order of 40%
5. Mockup experiments
5. Mockup experiments Other detection mode: charge exchange 2s states 1s states
5. Mockup experiments Other detection mode: charge exchange
Overview 1. Principle of the bound beta decay 2. The metastable 2s state of the H atom 3. Planned setup at FRM2 4. Simulations on background 5. Mockup experiments and options for detection 6. Current status and outlook
Status & outlook Step 1 More MC simulations are currently running, including better shielding and more precise geometry of the experiment Cross section measurements for lower energy charge exchange reaction in argon Alternative modes of hydrogen detection such as quenching chamber Installation of first BOB step (confirmation of branching ratio) at FRM2: hopefully until end of 2012! Step 2 Development of a spin conservation field inside the beam tube Using spin filter to analyze the spins of emerging hydrogen atoms Time scale: yet unknown.
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Proton source
Cesium cell
Spin filter spin state selection α states: F,m F >= 1,+1> & F,m F >= 1,0> β states: F,m F >= 1,-1> & F,m F >= 0,0>
Spin filter spin state selection