Hartmut Abele - Solvay Institutes

42 Pages·2014·3.12 MB·English

by  Physikalisches Institut

Neutron Beta Decay:

C C A & B
ORRELATION OEFFICIENTS

Hartmut Abele
Solvay Workshop 2014

Hartmut Abele, Technische Universität Wien
Standard Model and Neutron Decay
β
Neutron -decay

     
d′ d
V V V
     
ud us ub
n → p e ν CKM-Matrix: s′  =  V V V  s 
e
cd cs cb
     
b′ b
V V V
     
td ts tb
τ
lifetime ~ 15 min
β
-endpoint: E = 782 keV
max
V-A Theory: Vector coupling: g = G V f (q2→0)
V F ud 1
Axial vector coupling: g = G V g (q2→0)
A F ud 1
λ
ratio = g / g = -1.276
A V
Standard Model: V , λ, eiθ= -1
ud
2
Neutron Alphabet deciphers the SM
A
Observables
Parameters
Neutron Spin τ
ϑ Lifetime

Electron
• Strength: G a B Correlation A
F
D
• Quark mixing: V
Correlation B
ud
• Ratio: λ = g /g Correlation C
A V R Neutrino
N
Correlation a
C Q
R Correlation D
Proton
Correlation N
Correlation Q
R 5 4
f m c
τ−1 =V 2G 2(1 + 3λ2) e
Correlation R
ud F 2π3h 7
Beta Spectrum
Proton Spectrum
Beta Helicity
• Hartmut Abele, Atominstitut, TU Wien High Precision - Low Energy 3
Neutron Alphabet deciphers the SM
λ
a,A →
= g / g
A V

τ
A + → V from CKM matrix
ud

τ
A + B + → Right Handed Currents (RHC)?

W
W
L
R
H. Abele, NIM A 611 (2009) 193–197 4
Neutron Alphabet deciphers the SM

D, R ? T-odd → CP-violation

CP

 Candidate models for scalar couplings (at tree-level):
 Charged Higgs exchange
 Slepton exchange (R-parity violating super symmetric models)
 Vector and scalar leptoquark exchange
 The only candidate model for tree-level tensor contribution (in
renormalizable gauge theories) is:
 Scalar leptoquark exchange
See P. Herczeg, Prog. Part. Nucl. Phys. 46 (2001) 413.
5
Courtesy of K. Bodek
Characteristics PERKEO I
of Experiments
Using
Magnetic Fields
(Dubbers 1980s)
ϑ
A, B, C
Hartmut Abele, Technische Universität München 6
Method: P. Bopp et al., NIM A 267 (1988) 436.
λ
Why ratio = g / g from Neutrons?
A V
Processes with the same Feynman-Diagram
Courtesy of D. Dubbers 7
up: down:

Spectrometer Perkeo II N⇑ − N⇓ N⇑ − N⇓
A = A =
exp N⇑ + N⇓ exp N⇑ + N⇓

precise electron spectroscopy

Principle:
2x2π- Detection
two hemispheres
backscattering suppression
low background
strong beam PF1:
- count rate→systematic
zum beamstop
v λ(λ+ 1)
A = A Pf A = −2
exp
c 1 + 3λ2
λ= g /g
A V
Method see also: H. Abele et al., 17 keV Neutrino PLB 316 26 1993
8
a bit history:
λ from neutron β-decay

-1.1900(200), PDG (1960)
-1.2500(200), PDG (1975)
-1.2610(40), PDG (1990)
-1.2594(38), Gatchina (1997)
-1.2660(40), M, ILL (1997)
-1.2740(30), PERKEO II (1997)
-1.2686(47), Gatchina, ILL (2001)
-1.2739(19), PERKEO II (2002)
−1.27590(+409)(−445), UCNA (2011)
-1.2756(30), UCNA (2013)
-1.2748+13 PERKEO II (2013)
-14

9
Error Budget A
10