2. Contents
Introduction (motivation of precise measurements of neutron lifetime, history of experimental accuracy improvement).
a. Result of neutron lifetime measurements with gravitational trap of ultracold neutrons.
b. Preliminary result of neutron lifetime with magnetic trap of ultracold neutrons.
Neutron lifetime data for Standard Model and cosmology.
Conclusion.

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

4. Neutron decay and (V-A) test of Standard Model

5. A-asymmetry measurements (history of experimental results)
Ref./Year 
Mund et al. 2005 
Abele et al. 2002 
Yerozolimsky et al. 1997 
Liaud et al. 1997 
Abele et al. 1997 
Bopp et al. 1986 
Erozolimskii et al. 1979   
Krohn and Ringo 1975 

6. Neutron lifetime measurements (history of experimental results)
Lifetime τ[s]
Ref./Year
V. Ezhov et al. 2005
878.5  0.8
A. Serebrov et al. 2004
886.8  3.42
M.S. Dewey et al. 2003
885.4  0.95
S. Arzumanov et al. 2000
889.2  4.8
J. Byrne et al. 1995
882.6  2.7
W. Mampe et al. 1993
888.4  3.1  1.1
V. Nesvizhevski et al. 1992
878  27  14
R. Kosakowski 1989
887.6  3.0
W. Mampe et al. 1989
877  10
W. Paul et al. 1989
876  10  19
J. Last et al. 1988
891  9
P. Spivac et al. 1988
872  8
A. Serebrov et al. 1987
870  17
M. Arnold et al. 1987
903  13
Y.Y. Kosvintsev et al. 1986
875  95
Y.Y. Kosvintsev et al. 1980
937  18
J. Byrne et al. 1980
881  8
L. Bondarenko et al. 1978
918  14
C.J. Christensen et al. 1972
n=6.5

7. Recent neutron lifetime experiments PNPI with collaborators
Result of neutron lifetime measurements with gravitational trap of UCN (878.50.8) s (PNPI-ILL-JINR)
Preliminary result of neutron lifetime with magnetic trap of UCN ( ) s (PNPI-ILL-TUM)

8. Neutron lifetime measurements with gravitational trap of ultracold neutrons
PNPI-ILL-JINR
Setup for the measurement
of n-lifetime at ILL
(Grenoble, France)

9. Scheme of “Gravitrap”, the gravitational UCN storage system
1 – neutron guide from UCN Turbine;
2 – UCN inlet valve;
3 – beam distribution flap valve;
4 – aluminium foil (now removed);
5 – “dirty” vacuum volume;
6 – “clean” (UHV) vacuum volume;
7 – cooling coils;
8 – UCN storage trap;
9 – cryostat;
10 – mechanics for trap rotation;
11 – stepping motor;
12 – UCN detector;
13 – detector shielding;
14 – evaporator

10. Deposition of LTF on the trap surface
The chemical formula of LTF contains only C, O and F.
Molecular weight
Density at r.t g/ml
Vapour pressure at r.t.
1.5*10-3 mbar
Fermi potential neV
Calculation based on cold neutron transmission data predicts for LTF at 190K h=2*10-6 ( Yu.N.Pokotilovski, JETP 96, 2003)
LTF evaporator is heated to +1400C
Vacuum
Trap surface is cooled to about -1500C

11. Time diagram of measuring cycle

12. Method of n-lifetime measurement
Total probability of UCN losses:
Probability of losses in trap walls:

13. Calculation of loss weighted wall collision frequency

14. Extrapolation to n- lifetime ( joint energy and size extrapolation)
The result of joint (size and energy) extrapolation:
The result of energy extrapolation:
13 s
5 s
The result of size extrapolation:
7 s
Size extrapolation has rather weak dependence on m(E) and we take it as the most reliable.
The most close extrapolation to neutron lifetime (5 s only)
is reached in this experiment!

15. Final result and list of systematic corrections and uncertainties
t n [s] = ± 0.7stat ± 0.3syst

16. Neutron storage bottle
(made of permanent magnets)
PNPI-ILL-TUM
Preliminary measurement of neutron lifetime does not confirm world average value and is more close to measurements with gravitational trap.

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

18. 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.

19. Future projects for correlation coefficients
Experiment
Collaboration
Status
e- correlation a
aSPECT at FRM2/Munich
U. Mainz, TU Munich
e- correlation coefficient a
first data taking now
triple correlation D
emiT (NIST), TRINE (ILL)
emiT – scheduled to run at NIST
triple correlation coefficent R
at PSI
data taking
a,b,B,A correlations
at LANL (SNS)
simulations, hardware tests
A correlation (with UCN)
most parts installed
and tested
A,B correlations (with CN)
PNPI
detailed studies, preparation of installation
PERKEO 3 at ILL
coils delivered, first tests
D.Dubbers TPFNP, University of South Carolina (USA), October 14-15, 2005

20. Future neutron lifetime projects
• S. Dewey, NIST
• V. Ezhov, PNPI (ILL)
• A. Steyerl, URI (ILL)
• V. Morozov, KI (ILL)
• A. Serebrov, PNPI (ILL)
• P. Huffman, NSCU (NIST/SNS)
• S. Paul, TUM (ILL,FRM-II)
• Y. Masuda, KEK (RCNP,J-PARC)
• D. Bowman, LANL
presented at PMSN, NIST, April 2004
• A. Pichlmaier, PSI “insider” information
improvements in n flux measurement
bottle made of permanent magnets
LTF coated “accordion”
LTF coated teflon bottle
big gravitational trap coated with LTF
sc magnet and sfHe
measure decay
bottle made of superconducting magnets
measure storage and decay
bottle made of quadrupoles
now also with permanent magnets!
P.Geltenbort TPFNP, University of South Carolina (USA), October 14-15, 2005

21. Neutron decay and cosmology
G. J. Mathews, T. Kajino, T. Shima, Phys. Rev. D 71, (R) (2005)
n, world average
n, “Gravitrap” result
New n=(878.50.8) s confirms nb/n from CMB.

22. Conclusion
The most precise measurement of neutron lifetime with gravitational trap of UCN (878.50.8) s is in the contradiction with world average value (885.70.8) s - n=6.5 standard deviation.
Preliminary measurement of neutron lifetime with magnetic trap ( ) s does not confirm world average value and is more close to result of measurement with gravitational trap.
The most precise measurements of n and A-asymmetry are in better agreement with unitarity test of CKM.
New n=(878.50.8) s confirms nb/n from CMB.
The future improvement of =GA/GV measurement is extremely important for V-A test of Standard Model on the level 5∙10-4 of nVud.
There are the prospects to reach the level 5∙10-4.