UCN magnetic storage and neutron lifetime

1. UCN magnetic storage and neutron lifetime V.F.Ezhov Petersburg Nuclear Physics Institute, Gatchina, Russia. (ITEP - 2007)

3. After neutrino decoupling and electron-positron annihilation, neutron decay (lifetime ~ 880 sec) begins to deplete neutrons. Once temperature drops below 1.3·109 K, at t ~ 98 s, the rate of two-body and three-body reactions become negligible compared to the one-body reaction. Only neutron decay then dominates.

6. Neutron decay and Standard Model CKM mixing matrix: W.Marciano A.Sirlin PRL 96, 032002 (2006) Required experimental accuracy for n and A has to be about 10-3 and better.

7. N beam: 886.8±1.2±3.2 (NIST, 2003) 889.2±4.8 (Sussex-ILL, 1995) UCN storagein material trap: 878.5±0.7± 0.3 (PNPI-ILL,2004) 885.4±0.9±0.4 (KI-ILL, 1997) 882.6±2.7 (KI-ILL, 1997) 888.4±3.1±1.1 (PNPI, 1992) 887.6±3.0 (ILL, 1989) The best results for neutron lifetime Particle data 2003 (without PNPI - ILL,2004): n = (885.70.8) s

9. Neutron decay and Standard Model (status in 2003)

10. Data analysis with the most precise measurements of neutron decay nVud ΔVud=2.4σ 00Vud Δ=2.4σ The improvement of the accuracy of A-measurements (factor of 3 or more) is extremely important.

11. Reflection of UCN by magnetic barrier W. Paul, in Proc. Int. Conf. on Nuclear Physics and Physics of Fundamental Particles, Chicago, 1951. V.V. Vladimirskii, Sov.Phys. - JETP 12, 740, 1961 • Magnetic potential • For magnetic moment of neutron • Nuclear potential of Be • Magnetic field 1 T reflects neutrons up to 3.4 m/s, as Al. • + for and • – for

12. Probability of depolarization • Precession of magnetic moment • Adiabatic condition • ( -- is the velocity of neutron) • For case of strong field • (B = 1T), B = 1T/mm and velocity v = 3.4 m/s one can receive next relation for adiabatic condition: • 1.83108 >> 3.4103.

13. “UCN storage in the vessel with magnetic wall.” JETP Letters 23(3), 1976 Y.Y.Kosvintsev, Y.A.Kushnir, V.I.Morozov =25±2 sec

14. Y.G.Abov, V.V.Vasil’ev, V.V.Vladirski, I.B.Rozhnin JETP Letters, 44(8), 369, (1986) Ю.Г.Абов, В.В.Васильев,В.В.Владимирский, И.Б.РожнинПисьма ЖЭТФ, т.44(8), 369, (1986). Main problem of the current systems is too large electric power (about 100 kWt) Main result: It was shown firstly that it’s possible to obtain τ > 700 sec in the magneto-gravitational trap.

15. W. Paul, F. Anton, L. Paul, S. Paul, and W. Mampe, Z. f. Physik C 45, 25(1989). Sextupole torus. Rs orbit of circulating neutrons. τ= 877 ± 10 s The achieved usable fieldof 3.5 T permits the confinement of neutrons in the velocity range of 5 – 20m/s corresponding to a kinetic energy up to 2 * 10-6 eV.

17. P.R. Huffman, C.R. Brome, J. S. Butterworth, K. J. Coakle,M. S. Dewey, S.N. Dzhosyuk, R. Golub, G. L. Greene, K. Habicht,S.K. Lamoreaux, C.E.H. Mattoni, D.N. McKinsey, F. E. Wietfeldt,& J.M. DoyleNature 403, 62, 2000 The main problems: 1. Filling and empting. If one use superconducting system, then he can’t switch on field too fast. 2. Huge setup and small storage volume The trapping region is filled with superfluid 4He, which is used to load neutrons into the trap and as a scintillator to detect their decay. Neutrons have a lifetime in the trap of τ = 750+330−200 s.

18. Magnetic wall 1 – permanent magnet 2 – magnetic field guide

19. 2004

21. Detector of both polarization

22. Experimental advantages • To control the depolarization of UCN we cover the inner trap walls with thin lay of fomblin that reflects depolarized UCN. In this case the depolarized UCN penetrate the magnetic barrier inside the solenoid and are measured by the UCN detector installed below the solenoid. Hence this detector may be used as monitor for depolarization losses during neutron storage. • Monitor of trap filling • Preliminary neutron spectrum preparation • Absence of neutrons heating at the moment of magnetic shutter switching on. • Possibility to divide fast and spin-flipped neutrons

24. Cleaning. Magnetic wall is an ideal mirror, as a result there are stationary trajectories. Efficiency of depolarized neutrons collection. Problems

25. First stage: (2006) Neutron guide diameter 20 mm Without forced spin-flip Second stage: (2007) Neutron guide diameter 60 mm Forced spin-flip is switched on

27. Lifetime no depended method of efficiency measuring

29. 2005-2006 Volume 15 l Neutron elevator Storage time 874.6 -1.6 +4 sec. decay = 878.4  1.8 s. ε = 0.90±0.02

30. …………………………………………………….…………………………………………………….

31. 877.4±1.7 s.

32. 878.6±1.8 s.

33. N beam: 886.8±1.2±3.2 (NIST, 2003) 889.2±4.8 (Sussex-ILL, 1995) UCN storagein material trap: 878.5±0.7± 0.3 (PNPI-ILL,2004) 885.4±0.9±0.4 (KI-ILL, 1997) 882.6±2.7 (KI-ILL, 1997) 888.4±3.1±1.1 (PNPI, 1992) 887.6±3.0 (ILL, 1989) The best results for neutron lifetime Particle data 2003 (without PNPI - ILL,2004): n = (885.70.8) s Magnetic trap (2007) 878.2  1.6 s. Preliminary

35. Our plans • 2008 – increasing the volume to one order and increasing of magnetic barrier to 2 times • 2009 – run with new trap

36. V.F.Ezhov,1 B.A.Bazarov,1 P.Geltenbort,2 F.J.Hartman,3 N.A.Kovrizhnykh,4 A.Z.Andreev, 1 G.Ban5, A.G.Glushkov, 1 M.G.Groshev, 1 V.A.Knyazkov, 1 G.D.Krygin, 1 A.R.Muller, O.Naviliat-Cuncic5 S.Paul, 3 R.Picker, 3 V.L.Ryabov, 1 A.P.Serebrov, 1 O.Zimmer3,2 1 - Petersburg Nuclear Physics Institute, Gatchina, Russia. 2 - Institut Laue-Langevin, Grenoble, France. 3 - Technical University, Munich, Germany. 4 - Reseach Institute of electrophysical apparatus, S-Petersburg, Russia. 5 - Caen University, France

39. 2006-2007 Small diameter of neutron guide ε = 0.90±0.02 decay = 878.4  1.8 s. 877.4±1.7 s. Increased diameter of neutron guide 878.6±1.8 s. decay = 878.2  1.6 s. Preliminary