The Neutron Beta-Decay Exploring the properties of fundamental interactions Hartmut Abele Bar Harbor A,B,C,D,… The Neutron Alphabet

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.


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


June 2009: Fermi Spectrum

15

Spectrum after background subtraction, downstream detector:

it works!

prelim

inary

prelim

inary

Spectra for both spin states


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



-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


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


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


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


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)?


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)?


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


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


Can we get there?

New experimentsNew source for beta-decay products: PERC

35


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

Documents

The Neutron Beta-Decay Exploring the properties of fundamental interactions Hartmut Abele Bar Harbor A,B,C,D,… The Neutron Alphabet