the neutron beta-decay exploring the properties of fundamental interactions hartmut abele bar harbor...
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The Neutron Beta-Decay Exploring the properties of fundamental interactions
Hartmut AbeleBar Harbor
A,B,C,D,…A,B,C,D,…The Neutron Alphabet
Hartmut Abele, Technische Universität München 2
1. Standard Model and Neutron Decay
en p e
Neutron -decay
lifetime ~ 15 min -endpoint: Emax = 782 keV
V-A Theory: Vector coupling: gV = GF Vudf1(q2→0)
Axial vector coupling: gA = GF Vud
g1(q2→0)
ratio = gA/ gV = -1.276
Standard Model: Vud,
The Neutron Alphabet, Observables
Electron
Proton
Neutrino
Neutron Spin
A
B
C
A: P-odd Dr. Mund (2007) B: P-odd Schumann et al.,
PRL 99, 191803 (2007)C: P-odd Schumann et al., PRL 100, 151801 (2008)a Stratowa et al. (1975) D: T-odd TRINE, emiTG A. Kozela et al.,
PRL 102, 172301 (2009)N A. Kozela et al.,
PRL 102, 172301 (2009)R: T-odd A. Kozela et al.,
PRL 102, 172301 (2009)
aa
DDRR NN
see review: The neutron. Its properties and basic interactions, Prog. Part. Nucl. Phys. 60 (2008) 1-81
Hartmut Abele, Vienna University of Technology 4
Neutrons alphabetize the Standard Model
a or A = gA/ gV
2
2
( 1)2 0.1173(13)
1 3
( 1)2 0.103(4)
1 3
A
a
aSPECT, correlation a, University Mz/TUM/ILL
Proton spectroscopy
Hartmut Abele, Atominstitut, Vienna University of Technology 6
Analyzing Plane Electrode
Proton detector
Neutron decay
Protons
Magneticfield
Present best experiments: Δa/a = 5%Present status of aSPECT: (Δa/a)stat = 2% per day
Setup at the ILL-Grenoble, 2008
Anti-magnetic screen
… for a = - 0.103 (PDG 2008)
B0
U BA
nννee
p+e-
θ ec ,1 osv
p pc
w ad
Sensitivity of the proton spectrum to the neutrino electron correlation coefficient a
0 200 400 600
Proton kinetic energy E [eV]
Dec
ay r
ate
w(E
)
Spectrum for a = + 0.3
response function Ftr(E)=Ftr(E; U,BA/ B0) @ U=375V
… for a = - 0.103 (PDG 2008)
UMZ, TUM, ILL: Neutron decay spectrometer aSPECT
aCORN
Tulane (F. Wietfeldt), Indiana, NIST, et al.
p e
p pv v
p
n
e-
e ( ) 1 cos ,
ee
vw E a p p
c
pp, 2
eBRp
c ee, 2
eBRp
c
, e,~p p
Fast group Slow group
epp
8
Principle: momentum space diagram
Typical momentum vector for pe
p lie in a second cylinder, kinematically distinct groupsa will cause an asymmetry between coincidence events between I and II.Groups I and II can be experimentally distinguished by TOF.
B
Hartmut Abele, Atominstitut, Vienna University of TechnologyHartmut Abele, University of Heidelberg 9
Nab
Electron and neutrino momenta from electron energycose from proton momentum and electron energy using
4T 1TTOF between electron and proton
Bowman, Pocanic et al.
Hartmut Abele, Technische Universität München 10
Characteristics of Experiments
Using Magnetic Fields
(Dubbers 1980s)
A, B, C
PERKEO I
Results A: 2004 - 2006
PERKEO II CollaborationNew beam position PF1B@ILLNew polarizer system 99.7%New analyzer system 100%
ElectronNeutron Spin
A
Hartmut Abele, Vienna University of Technology
12
2002 2002 2006 2006 correction uncertainty correction uncertainty polarization 1.1 % 0.3 % 0.3 % 0.1 % flipper efficiency 0.3 % 0.1 % 0.0 % 0.1 % Statistical error 0.45 % 0.26 % background 0.5 % 0.25 % 0.1 % 0.1 % detector function 0.26 % 0.18 % edge effect -0.24 % 0.1 % -0.22 % 0.05 % time resolution 0.25 % mirror effect 0.09 % 0.02 % 0.11 % 0.01 % backscattering 0.2 % 0.17% 0.003 % 0.001 % rad. corrections 0.09 % 0.05 % 0.09 % 0.05 % Sum 2.04 % 0.66 % 0.38 % 0.41 %
sum 2006 preliminary
2002 2002 2006 2006 correction uncertainty correction uncertainty polarization 1.1 % 0.3 % 0.3 % 0.1 % flipper efficiency 0.3 % 0.1 % 0.0 % 0.1 % Statistical error 0.45 % 0.26 % background 0.5 % 0.25 % 0.1 % 0.1 % detector function 0.26 % 0.18 % edge effect -0.24 % 0.1 % -0.22 % 0.05 % time resolution 0.25 % mirror effect 0.09 % 0.02 % 0.11 % 0.01 % backscattering 0.2 % 0.17% 0.003 % 0.001 % rad. corrections 0.09 % 0.05 % 0.09 % 0.05 % Sum 2.04 % 0.66 % 0.38 % 0.41 %
sum 2006 preliminary 2002: result: A = -0.1189(8) = -1.2739(19)2006: result: A = -0.1198(5) = -1.2762(13)
13
PERKEO III: Impressions from the Installation at ILL
Plastic Scintillator Detector
Spectrometer PERKEO III
B. Maerkisch, PERKEO III : Neutron Decay Measurements
LiF Chopper
Time of Flight Spectrum
14
neutron time of flight [s]
boron beamdumphomogeneou
s magnetic field region
chopper open
background measurement
counts
in detectors
B. Maerkisch, PERKEO III : Neutron Decay Measurements
June 2009: Fermi Spectrum
15
Spectrum after background subtraction, downstream detector:
it works!
prelim
inary
prelim
inary
Spectra for both spin states
B. Maerkisch, PERKEO III : Neutron Decay Measurements
June 2009: Beta Asymmetry Spectrum
16
prelim
inary
18h of data, downstream detector:
Statistical precision ~1% / day
exp
1 v
2 c
N NA
N N
PfA
expA
B. Maerkisch, PERKEO III : Neutron Decay Measurements
Hartmut Abele, Technische Universität München 17
-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), HD, ILL (1997)
-1.2686(47), Gatchina, ILL (2001)
-1.2739(19), HD, ILL (2002)
-1.2762(13), HD, ILL (2006)
a bit history:from neutron -decay
Hartmut Abele, Technische Universität München 18
UCN source
Polarizer / Spin flipper
Diamond-coated quartz tube
MWPCPlastic scintillator
Light guide
Superconducting solenoidal magnet (1.0 T)
Decay volumeField Expansion Region
Detector housing
PMT
Neutron
absorber
UCNA (ultracold neutrons)
Short test run: A0=-0.1138(46)(21)
A. Young (NCSU), A. Saunders (LANL), et al.
A0
-0 .1 5
-0 .1
-0 .0 5
E n erg y (k eV )
Rat
e (1
/50
keV
·s)
00 2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0
0 .1
0 .2
0 .3
0 .4
0 .5S ig n a l
A 0< P > = -0 .11 3 8 ± 0 .0 0 4 6
B ack g ro u n d
Be coatedmylar foil
20
Why ratio = gA/ gV from Neutrons?
Processes with the same Feynman-Diagram
Courtesy of D. DubbersHartmut Abele, Vienna University of Technology
Hartmut Abele, Technische Universität München 21
a,A = gA/ gV
A + Vud from CKM matrix
Letters and SM spelling
0%
50%
100%
'down' 'strange' 'bottom'
down strange bottom
ud us ub
cd cs cb
td ts tb
V V VV V VV V V
d d
s s
b b
|Vud|2 + |Vus|
2 + |Vub|2 = 1-|Vud|
2 + |Vus|2 + |Vub|
2 = 1-
Quark mixing is rotation in flavor spaceCKM-Matrix is unitary
5 4
1 2 2 23 7(1 3 )
2
Re
ud F
f mV
cG
h
Hartmut Abele, Technische Universität München 22
Situation 1995 - 2004
+ +
Neutron -decay
0 0 nuclear -decay
Pion -decay
0.9717(13)
0.9738(4)
0.
0.0040 0.0
972
012
8(30)
ud
ud
ud
V
V
V
Baseline from Vus
Hartmut Abele, Atominstitut, Vienna University of Technology
Present status lifetime2 types of experiments:• Beam experiments • Storage experiments
• Storage losses
23
Hartmut Abele, Atominstitut, Vienna University of Technology
New experiments
World average 885.2 ± 0.8 s without 878.5 ± 0.8 s = 878.2 ±1.9 Ezhov, UCN09 St. PetersburgNew plans:- PENELOPE
- UCN in permanet magnets
- UCN in He
- cold neutrons in beam
24
25
a,A = gA/ gV
A + Vud from CKM matrix
A + B + Right Handed Currents (RHC)?
Letters and SM spelling
WL WR
2626
Origin of nature’s lefthandednessStandard Model: Elektroweak interaction 100% lefthanded
Grand unified theories:Universe was left-right symmetric at the beginningParity violation = 'emergent' Order parameter <100%
Neutron decay: Correlation B + A:Mass right handed W-Boson: mR > 280 GeV/c2
Phase: -0.20 < <0.07
WL WR
Our Result:
New mean Value:
Bmean = 0.9807(30)
Result PERKEOII: Asymmetry B & Asymmetry C
Thesis: M. Schumann 2007
Background Bn Displacement
B = 0.9802(50)
result is virtually independent from detector calibration
• result limited by statistics and error ( magnetic mirror effect)
Schumann et al., Phys. Rev. Lett. 99, 191803 (2007), arXiv:0706.3788.
C = -0.2377(26)Schumann et al., Phys. Rev. Lett. 100, 151801 (2008), arXiv:0706.3788.
28
C = xc A + B
A + B + C Scalar Interactions Tensor Interactions
A + B + C Right Handed Currents (RHC)?
Letters and SM spelling
S, T
WL WR
V-A
A + B + C + Neutrons 29
A + B + C Scalar Interactions Tensor Interactions
Letters and SM spellingS, TV-A
World average 2007
gT/gA gT/gA
Schumann et al., PRL 100, 151801 (2008)
30
D, R ? T-odd CP-violation
Letters and SM spelling: Times Reversal Tests
CP
See P. Herczeg, Prog. Part. Nucl. Phys. 46 (2001) 413.See P. Herczeg, Prog. Part. Nucl. Phys. 46 (2001) 413.
Candidate models for scalar couplings (at tree-level):Candidate models for scalar couplings (at tree-level): Charged Higgs exchangeCharged Higgs exchange Slepton exchange (R-parity violating super symmetric models)Slepton exchange (R-parity violating super symmetric models) Vector and scalar leptoquark exchangeVector and scalar leptoquark exchange
The only candidate model for tree-level tensor contribution (in The only candidate model for tree-level tensor contribution (in renormalizable gauge theories) is:renormalizable gauge theories) is: Scalar leptoquark exchangeScalar leptoquark exchange
Courtesy of K. Bodek
K. Bodek, PSI Users' Meeting No. 40, 2009
31
x
y
z
MWPCscintillator scintillator
Pb-foilPb-foil
Mott polarimeterMott polarimeter
<SMott> 0.2Analyzing power• Measure polarization of e in polarized n-decayMeasure polarization of e in polarized n-decay
– Analyzer: Mott scattering of e on leadAnalyzer: Mott scattering of e on lead– Measure e-track twiceMeasure e-track twice– Precision: 2Precision: 21010-2-2
– R = 0.008 ± 0.015 ± 0.005R = 0.008 ± 0.015 ± 0.005
– For details : Bodek et al.For details : Bodek et al.
PRL 102 172301 (2009)PRL 102 172301 (2009)
( ), 1 ..e
eA
e
eA R
JW J
E
p
19-Feb-2009
Bodek, PSI Users' Meeting No. 40, 200932
Limits on Limits on SS and and TT coupling coupling
constantsconstants
Low energy studies in the LHC era
Low energy =High precision
33
Hartmut Abele, Atominstitut, Vienna University of Technology
Super symmetry effects:B-coefficientEffect large:
g-2
neutron-beta-decy
3
~
~ 10
W
SUSY
M M
9
~
~
~ 10
W
SUSY
M m
m M
10-5
See Ramsey-Musolf, Physics Reports 456 (2008) 1–88Low-energy precision tests of supersymmetry
Hartmut Abele, Atominstitut, Vienna University of Technology
Can we get there?
New experimentsNew source for beta-decay products: PERC
35
Hartmut Abele, Technische Universität München 36
Cold Neutrons @ PF1B (ILL), MEPHISTO (FRM2)
High Flux: = 2 x 1010 cm-2s-1
Decay rate of 1 MHz / metre
Polarizer: 99.7 ± 0.1 %Spin Flipper: 100.05 ± 0.1 %Analyzer: 100 % 3He-cells
Spectrometer
Hartmut Abele, Atominstitut, Vienna University of TechnologyHartmut Abele, Technische Universität München 37
v- selector
Spin flipper
PolarizerDecay Volume, 8m
Chopper
Beam stop
e,p selector Analyzing area
PERC: A clean, bright and versatile source of neutron decay products
n-guide + solenoid: field B0polarized, monochromatic n-pulse
n + γ-beam stopsolenoid, field B1
solenoid, field B2p+ + e− window-framep+ + e− beam
D. Dubbers, H. Abele, S. Baeßler, B. Maerkisch, M. Schumann, T. Soldner, O. Zimmer, arXiv:0709.4440.
Summarya, A, B, C, D… In standard model: a and A are related to
Sensitivity to S, V, A, T, P interaction
Sensitivity to symmetries- P-violating: A, B , C, R
- T-violating: D, R
If T-invariance holds, coupling constants are real
4, 7 10A
V
g
g