1. An experimental limit on neutron mirror-neutron oscillation Ulrich Schmidt Physikalisches Institut, Universität Heidelberg, Germany

2. What are mirror particles ??? P World is not P symmetric P RR World is PR symmetric

3. Properties of mirror particles For each particle exists a mirror particle which has exactly the same properties in the mirror world, as the particle in the world beside handedness. Interaction between particles and mirror particles: gravity Possible interaction between particles and mirror particles: Oscillations/mixing between neutral particles and mirror particles 

4. phenomenology of oscillation with free flying neutron: only magnetic field counts for  E

5. “field free” region magnetic field strongly suppress oscillation

6. n beam beam dump field free region detector field free region Reappearance experiment

7. Problem: loss of neutrons due to  -decay, scattering... R ±  R is compatible with 1 => But !! Only is suppressed by a moderate magnetic field (0.1 mT) Disappearance experiment principle of our measurement: measuring loss of neutrons due to n beam field free region detector

8. RESEDA am FRM II

9. CASCADE: Multiple Boron Layers on GEMs GEMs can be operated to be transparent for charges!  they can be cascaded! Each one can carry two Boron layers. Last one operated as amplifier. Accumulate single layer detection efficiency up to 50% for thermal neutrons (1.8Å) and up to 75% for cold neutrons (5Å). 10 B + n  7 Li +  + 2.79 MeV ( 6%) 3838 b  7 Li * +  + 2.31 MeV (94%) Problem: n-counting at very high rates Conventionel ( 3 He-counters): < 10kHz/cm 2 CASCADE: up to 10 MHz /cm 2

10. The Gas Electron Multiplier (GEM) Amplifier Mode In hole high fields allow Gas amplification 1 - 400 Transparent Mode At gain 1, electric fields transport charges through the holes Electrons Ions pictures from Sauli The GEM inherently introduces high rates capability of 10 MHz/cm 2 ! taken from Sauli et al.: http://www.cern.ch/GDDhttp://www.cern.ch/GDD

11. length flight path velocity of neutrons B-field integral along neutron flight path gyromagnetic ratio U. Kinkel Z.Phys.C 54,573-575(1992)

12. measuring cycle: - 0.5s without magnetic field - switch magnetic field on, wait 0.1 s - 0.5s with magnetic field - switch magnetic field off, wait 0.1 s length flight path: 6m,  = 11Å => v = 360m/s => t = 17ms 2 day measurement, about 10 5 individual ratios R

13. scattering (standard deviation) of the individual ratios: 0.0082 error of the individual ratios calculated from number of count: 0.0039 => sensitivity is limited by intensity fluctuations of the beam

14. VCN beam 50% monitor counter detector field free region noise of R ~ will be much less than noise of R

15. Thank you for your attention Experiment FRM II Barbara Böhm 1 Wolfgang Häusler 2 Dominik Streibel 2 1 Physikalisches Institut Heidelberg 2 FRM II (Forschungsreaktor München II) CASCADE detector Martin Klein 1 Gerd Mozel 1 Jörg Betz 1 Stefan Backfisch 1 n

16. The Assembled 2D-Detector GEM-foils coated with 10 B and 2D readout structure EMI shielding (500 µm Al) Power supply and thermal management FPGA based readout board ASIC frontend- electronic Detector entrance window (100 µm Al)

17. Neutron-Pictures with the 2D-200 CASCADE Detector System Tesa-Tape old PC- Mouse Water Flow- Controller measured at instrument EKN at FZ Jülich Pixel (1.56mm)