Contents

1

Neutron decay, Standard Model

and Cosmology

A.Serebrov, PNPI, Gatchina, RussiaICHEP’06 Moscow, 26.07-02.08, 2006

2

Contents

1. Introduction (motivation of precise measurements of neutron lifetime, history of experimental accuracy improvement).

2. a. Result of neutron lifetime measurements with gravitational trap of ultracold neutrons.

b. Preliminary result of neutron lifetime with magnetic trap of ultracold neutrons.

3. Neutron lifetime data for Standard Model and cosmology.

4. Conclusion.

3

CKM mixing matrix:

V F udG G V

A0 2

V

1G A 2

G 1 3

2

ud 2n

4908.7 1.9 sV

1 3

R R 2 2 2

ud F

kft 1 1

V G 1 3

Required experimental accuracy for n and A has to be about 10-3 and better.

Neutron decay and Standard Model

~1.5 % ~2.4 %

u

n d

d

u

d p

u

e-

eW-

GA

GV

u

n d

d

u

d p

u

e-

eW-

u

n d

d

u

d p

u

e-

eW-

GA

GV

GA

GV

W.MarcianoA.SirlinPRL 96, 032002 (2006)

ud us ub

cd cs cb

td ts tb

d V V V d

s V V V s

b V V V b

4

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

00 002R R C

0u

20Fd

kFt (ft) (1 )(1 )(1 )

GV

n 00 2 2ud ud us ubV V 1 V V

V-A test of Standard Model

n2n

nR R

2ud F

kFt (ft) (1 )(1 )

)V G (1 3

0 0 superallowed Fermi transition

neutron

5

A-asymmetry measurements (history of experimental results)

A-asymmetry Ref./Year

-0.1187 0.0005

Mund et al. 2005

-0.1189 0.0008

Abele et al. 2002

-0.1135 0.0014

Yerozolimsky et al. 1997

-0.1160 0.0015

Liaud et al. 1997

-0.1189 0.0012

Abele et al. 1997

-0.1146 0.0019

Bopp et al. 1986

-0.1120 0.0062

Erozolimskii et al. 1979

-0.1140 0.0120

Erozolimskii et al. 1979

-0.1200 0.0100

Erozolimskii et al. 1979

-0.1160 0.0110

Krohn and Ringo 1975

-0.1040 0.0110

Krohn and Ringo 1975

1970 1980 1990 2000 2010

-0,130

-0,125

-0,120

-0,115

-0,110

-0,105

-0,100

-0,095

A=-0.1173(13)=-1.2695(29)

A=-0.1187(5) PERKEO 2005=-1.2733(13) (preliminary)

the most precise measurement

A-a

sy

mm

etr

y

year

PDG 2006

6

Neutron lifetime measurements (history of experimental results)

Lifetime τ[s] Ref./Year

874.6+4.0-1.6

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=6.51970 1980 1990 2000 2010

820

840

860

880

900

920

940

960

-1.6-1magnetic trap

(V.Ezhov et al.)

+4.0874.6878.5±0.8

885.7±0.8

"Gravitrap"(A.Serebrov et al.)

ne

utr

on

lif

eti

me

(),

s

year

world average

7

Recent neutron lifetime experiments

a. Result of neutron lifetime measurements with gravitational trap of UCN (878.50.8) s (PNPI-ILL-JINR)

b. Preliminary result of neutron lifetime with magnetic trap of UCN (874.6+4.0

-1.6) s (PNPI-ILL-TUM)

PNPI with collaborators

8

Setup for the measurement of n-lifetime at ILL (Grenoble, France)

Neutron lifetime measurements with gravitational trap of ultracold neutrons

PNPI-ILL-JINR

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.

mbar

Fermi potential neV

Calculation based on cold

neutron transmission data

predicts for LTF at 190K

( Yu.N.Pokotilovski

, JETP 96, 2003) Trap surface is cooled to about -1500C

LTF evaporator is heated to +1400C

Vacuum

11

010-2

10-1

100

101

102

103

104

105

Co

un

t ra

te

700 1000 1500 2000 2500 30000

10

20

30

40

010-2

10-1

100

101

102

103

104

105

Co

un

t ra

te

700 1000 1500 2000 2500 30000

10

20

30

40

Time, s

Time diagram of measuring cycle

2 1

1

2

ln

hold holdst

t t

N

N

12

Method of n-lifetime measurement

Im( )

Re( ) F

F

U

U wall loss coefficient

E loss weighted wall collision frequ ency

1 1 (1) 1 1(1) (2) (1)1 1

(1) (2)1 1 (2)(2)

(1) 1

storage n storage storagen storage

storage n

E

EE

E

1 1 1 storage n loss Total probability of UCN losses:

Probability of losses in trap walls:

1 loss E

13

Calculation of loss weighted wall collision frequency

( )є

UCN energy, neV

1 0

0

1v

4

є

wall є

n

n

dS

dV

( ) ( )

( )

є-h є-h (є-h) (h)

(є)

є-h (h)

0 10 20 30 40 50 60 700

2

4

6

8

10

12

narrow trap wide trap

0 10 20 30 40 50 60 700

10000

20000

30000

40000

Measurement of UCN spectrum

Co

un

t o

f c

ap

ture

d U

CN

Gravitational barrier height, cm

wide trap narrow trap

14

Extrapolation to n- lifetime ( joint energy and size extrapolation)

The result of joint (size and

energy) extrapolation:

877.60 0.65 Jn s

878.07 0.73 Sn s

875.55 1.60 En s

6(2.23 0.19) 10 2 0.95

The most close extrapolation to neutron lifetime (5 s only) is reached in this experiment!

7 s

5 s

13 s

Size extrapolation has rather

weak dependence on (E) and

we take it as the most reliable.

The result of energy extrapolation:

The result of size extrapolation:

15

Final result and list of systematic corrections and uncertainties

n [s] = 878.5 ± 0.7stat ± 0.3syst

Size extrapolation Value,s Uncertainty, s

n-lifetime 878,07 0,73

Systematic effect Value,s Uncertainty, s

Method of values calculation 0 0,236

Influence of mu-function shape 0 0,144

Spectrum uncertainties 0 0,104

Uncertainties of traps sizes(1mm) 0 0,058

Influence of the residual gas 0,40 0,024

Uncertainty of LTF critical energy (20 neV) 0 0,004

Total systematic effect 0,40 0,30

16

Neutron storage bottlePNPI-ILL-TUM

4.01.6874.6 s

st

Preliminary measurement of neutron lifetime does not confirm world average value and is more close to measurements with gravitational trap.

(made of permanent magnets)

17

Neutron decay and Standard Model (status in 2003)

2 2 2nud us ubV V V

1 0.9924(28)

0.0076(28) 2.7

nud

00ud

us

ub

V 0.9717(13)

V 0.9738(5)

V 0.2196(23) PDG(2003)

V 0.0036(9) PDG(2003)

nA,

00ft

2us1 V

n 00ud udV V 0.0021(26)

0.8

n

A=-0.1189(8) PERKEO 2002

885.7 0.8 s PDG(2003)

18

Data analysis with the most precise measurements of neutron decay

2 2 2nud us ubV V V

1.0038 28 = 1.4 -

2 2 200ud us ubV V V

0.9992 15 = 0.5 +

n 00ud ud

3

However

V V

2.4 1.0 10

2.4Δ=2.4σ

ΔV

ud=

2.4σ

nVud

00Vud

n 878.5 0.8 s (A.Serebrov et al. 2005)

A=-0.1187(5) (PERKEO 2005)

=-1.2733(13)

nud

2ud us

us

00ud

ub

V 0.97614(95)

V 1 V 0.97420(47)

V 0.2257(21) PDG06

V 0.97377(27) PDG06

V 0.0043(3) PDG06

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) at LANL (SNS) most parts installed

and tested

A,B correlations (with CN) PNPI detailed studies, preparation of installation

A,B correlations (with CN) 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

P.Geltenbort TPFNP, University of South Carolina (USA), October 14-15, 2005

• 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

measure decay

bottle made of quadrupoles

now also with permanent magnets!

bottle made of permanent magnets

measure storage and decay

21

Δ 1% Δ =0.75% 0.61%

Δ 1% Δ =17% 3.3%

n

n

Y

2

1 2 53

1 32F

n A e

Gf g m

n, “Gravitrap” result

n, world average

Neutron decay and cosmologyG. J. Mathews, T. Kajino, T. Shima, Phys. Rev. D 71, 021302(R) (2005)

New n=(878.50.8) s confirms nb/n from CMB.

22

Conclusion

1. The most precise measurement of neutron lifetime with gravitational trap of UCN (878.50.8) s is in the contradiction with world average value (885.70.8) s - n=6.5 standard

deviation.

2. Preliminary measurement of neutron lifetime with magnetic trap (874.6+4.0

-1.6) s does not confirm world average value and is

more close to result of measurement with gravitational trap.

3. The most precise measurements of n and A-asymmetry are in

better agreement with unitarity test of CKM.

4. New n=(878.50.8) s confirms nb/n from CMB.

5. 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.

6. There are the prospects to reach the level 5∙10-4.