Hartmut Abele, Technische Universität Wien Bastian Märkisch Hartmut Abele CKM2014 Neutron Beta...

Hartmut Abele, Technische Universität Wien

Bastian MärkischHartmut AbeleCKM2014

Neutron Beta Decay:

Determination of the Weak Axial Vector Coupling

2

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, , ei= -1

en p e

Standard Model and Neutron Decay

ud us ub

cd cs cb

td ts tb

CKM-Matrix: V V VV V VV V V

d d

s s

b b

3

Parameters• Strength: GF

• Quark mixing: Vud

• Ratio: = gA/gV

5 41 2 2 2

3 7(1 3 )2ud

Re

F

fV

mG

ch

ObservablesLifetime Correlation A

Correlation B

Correlation C

Correlation a

Correlation D

Correlation N

Correlation Q

Correlation R

Beta Spectrum

Proton Spectrum

Beta Helicity

Electron

Proton

Neutrino

Neutron Spin

A

B

C

a

D

R N

Neutron Alphabet deciphers the SM

High Precision - Low Energy• Hartmut Abele, Atominstitut, TU Wien

RQ

4

a,A = gA/ gV

A + t Vud from CKM matrix

A + B + t Right Handed Currents (RHC)?

WL WR


H. Abele, NIM A 611 (2009) 193–197

5

D, R ? T-odd CP-violation

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): 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

Courtesy of K. Bodek


6Hartmut Abele, Technische Universität München

Characteristics of Experiments

Using Magnetic Fields

(Dubbers 1980s)

A, B, C

PERKEO I

Method: P. Bopp et al., NIM A 267 (1988) 436.

7

Why ratio = gA/ gV from Neutrons?

Processes with the same Feynman-Diagram

Courtesy of D. Dubbers

PERKEO II Spectrometer

8.9.2014 CKM 2014, Vienna - Bastian Märkisch 8

• X-SM crossed polariser geometry: Kreuz et al., NIM A 547, 583 (2005) Neutron polarisation P = 99.7(1)%

• Largely reduced background (Mund et al., PRL 110 (2013))Improved beam line setup and shielding, Overall S:B = 8:1 Beam related background : 1/1700 in signal region (previous:1/200)

3rd run (beta asymmetry), major Improvements:

Magnetic field:

• alignment of neutronspin

• guide e, p onto detectors

• separation into hemispheres

2 x 2 detector

• backscatter suppression

Error Budget A

9

10

-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

-14 PERKEO II (2013)

a bit history: l from neutron b-decay

PERKEO II: Combined Result


Combine all PERKEO II results:

H. Abele et al., Phys. Lett. B 407, 212 (1997) A = - 0.1189(12)H. Abele et al., PRL 88, 211801 (2002) A = - 0.1189(8)D. Mund et al., PRL 110, 172502 (2013) A = - 0.11972(+53

-65)

Final Perkeo II result:A = - 0.11926(+47

-53) ΔA/A = 4.2 ∙ 10-3

λ = - 1.2748(+13-14) Δ λ / λ = 1.1 ∙ 10-3

Conservative treatment of correlated errors:detector calibration and uniformity, background determination, edge effect, radiative correction

Vud = 0.97449(18)RC(40)tau(80)AVud = 0.97449(18)RC(40)tau(80)A

Vud = 0.97425(8)exp.(10)nucl.dep.(18)RC (superallowed)Vud = 0.97425(8)exp.(10)nucl.dep.(18)RC (superallowed)

12

-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

-14 PERKEO II (2013)

a bit history: l from neutron b-decay

13 = l -1.2756(30), UCNA (2013)

UCNA (2013)

Recent Results: PERKEO Collaboration

14 14

A =-0.1197(6)

APII = 0.1193(5)PII = 1.2748(13)

error: 1×103

Electron Asymmetry A:

PRL 110, 172502 (2013)

Proton Asymmetry C:

Neutrino Asymmetry B:

B = 0.9802(50)Schumann et a.PRL 99, 191803 (2007)

PERKEO II combined:

first precision measurement

C = 0.2377(36)Schumann et al.,PRL 100, 151801 (2008)

15

Coefficient B,C Proton detector

H. Abele, NIM A 611 (2009) 193–197

C foil ScintillatorProton

Proton detection:• Measure electron energy• Wait for proton• Convert proton into electron signal

Proton detection:• Measure electron energy• Wait for proton• Convert proton into electron signal

n-Spin

16

M. Schumann: The Neutrino-Asymmetry B

M. Schumann,M. Kreuz, M. Deissenroth,F. Glück,J. Krempel, B. Märkisch,D Mund, A. Petoukhov, T. Soldner, H. Abele, PRL 100, 151801 (2008)

• Electron and Proton in same hemisphere

low dependence on energy calibration and energy resolution higher sensitivity due to larger exp. asymmetry

• Electron and Proton in opposite hemispheres

more statistics since this case occurs for ~78% of the events

Electron Proton

Neutron Spin

Neutrino

Electron

Proton

Neutrino

Neutron Spin

NN

NNBexp

NN

NNBexp

Systematically clean method: Integration over two hemispheres

17

Coefficient B, Serebrov et al.

H. Abele, TU Wien

P E R K E O I I IB. Märkisch:Spectrometer PERKEO III

8.9.2014 18

Magnetic field :• alignment of nspin• guide e, p onto detectors

2 x 2 detector

• separation into hemispheres

detector

detector

neutron beam

electron tracks

B = 150 mT

active volume ~2m, 15x15cm²

B = 90 mT

• decay volume 10x longer: ~50.000 events/s in cont. Beam• B = 0.15T

CKM 2014, Vienna - Bastian MärkischB. Maerkisch et al., NIM 611 (2009) 216–218

P E R K E O I I I

velocity selectorl=5.0Å∆ / = 10%l l

~2m, 150mTbeam dump, enriched 10B

homogeneous fieldContinuous,“monochromatic”neutron beam

chopper (6LiF)@ 94Hz

magnetic field

Pulsed Cold Neutron Beam

8.9.2014 19

electron detector

• Edge-free projection onto detectors: full 2 x 2 p detection without distortions

• Background can be fully measured and subtracted

D. Werder, UHD

• Magnetic mirror effect controlled

Benefits:

CKM 2014, Vienna - Bastian Märkisch

P E R K E O I I IPulsed Neutron Beam


time for signalmeasurement

neutrons hitbeam dump

time forbackgroundmeasurement

slopes due tomagnetic mirror

Signal region 300 keV < E < 700 keV

upstreamdownstream

P E R K E O I I IBackground Subtraction

8.9.2014 21

Time variation of background signal consistent with zero!

Signal region 300 keV < E < 700 keV

Additional background tests:Background monitors (NaI and He), control measurements with blocked beam

Chopper83 Hz

Chopper94 Hz

4101 A

A

CKM 2014, Vienna - Bastian Märkisch

coun

ts (a

.u.)

coun

ts (a

.u.)

P E R K E O I I IInstallation at PF1B, ILL

8.9.2014 22

One of two trucks

Plastic scintillator

Experimental Zone

96% of data acquired in analysis6 10∙ 8 neutron decay events

P E R K E O I I IBeta Asymmetry, Chopper 94 Hz

23

Raw Signal + Background Signal, Background Subtracted

Sum and Difference Experimental Asymmetry

preliminary

preliminary

preliminary

preliminary

NN

NNAexp

P E R K E O I I I

Source Correction ∆A/A (10-4)

Uncertainty ∆A/A (10-4) Predecessor

Neutron beam Polarisation < 10 / 1.4Spin flip efficiency

Background / 7Undetected 1Time variation -1 1

ElectronsMagnetic mirror effect 4Lost backscatter energy 1.4

DetectorDeadtime * -5 2Non-linearity 4 / 4.6Non-uniformity 3Stability * 2Calibration 0.5

Theory Radiative corr. * -1.1 2Total Systematics 12.4 / 3.2Statistics 13.9 / 2.7Total 18.6

Error Budget

24

separate analysis

3109.1 A

A

4108.4

Result (still blinded):separate analysis

2.3x better than Perkeo II

P E R K E O I I IPERKEO III Team

8.9.2014 25

D. Dubbers, B. Märkisch, H. Mest, C. Roick, D. WerderHeidelberg University

H. Abele, H. Saul, X. Wang

Institut Laue Langevin, GrenobleT. Soldner, A. Petoukhov

TU Vienna, TU Munich

PERKEO III Team, ILL

Source Correction ∆A/A (10-4)

Uncertainty ∆A/A (10-4) Predecessor

Neutron beam Polarisation < 10 / 1.4Spin flip efficiency

Background / 7Undetected 1Time variation -1 1

ElectronsMagnetic mirror effect 4Lost backscatter energy 1,4

DetectorDeadtime * -5 2Non-linearity 4 / 4.6Non-uniformity 3Stability * 2Calibration 0,5

Theory Radiative corr. * -1,1 2Total Systematics 12,4 / 3.2Statistics 13,9 / 2.7Total 18,6

Error Budget Uni HD Maerkisch et al., ILL: Soldner et al. TU Wien: Wang et al.

26

separate analysis

3109.1 A

A

4108.4

Result:

separate analysis

Factor 4 improvement over PDG 2013 average

Close to Publication

aCORN @ NISTaSPECT @ Mz, ILL, TUWPERKEO III @ UHD, ILL, TUW: A (B,C not so close)

New InstrumentsNab, PERC

Hartmut Abele, Atominstitut, Vienna University of Technology 27

R. Feynman

Hartmut Abele, Helmut Leeb, Technische Universität Wien

28

30

Standard Model of Particle PhysicsInput: Principia: - Gauge principle U(1) x SU(2) x SU(3)- Lorentz invariance : x‘ = Lx- CPT, ...Invariance

Output: - Interactions- Equation of motion Maxwell, Schrödinger, Dirac- Existence of Photons, Gluons, W±, Z0

(carriers of interaction)- Charge conservation (Source of interaction)

Conclusion: SM very successful- e.g. as basis for technology, chemistry, biology, mol.biologie

D. Dubbers 2007

31

Weak Magnetism form factor f2

Neutron Decay Transition Matrix:

Electron Asymmetry:

f2 Weak Magnetism Form Factor

(SM prediction)

2 % additional Edependence of A

2 21 3

22[ ( ) ( ) ]|2

( )

p

V p f k k if k k nf k

m

Ffi 5 5

GT | (1 ) | ( (1 ) )

2udV p n e

Beyond SMA search for - right-handed admixtures to the left-handed feature of the Standard model. They

are forbidden in the Standard-Model, but, as a natural consequence of symmetry breaking in the early universe, they should be found in neutron-decay. Signatures are a WR mass with mixing angle z.

- scalar and tensor admixtures gS and gT to the electroweak interaction. gS and gT are also forbidden in the Standard model but supersymmetry contributions to correlation coeffi cients or the Fierz interference term b can approach the 10−3 level.

A precision measurement of - the weak-magnetism form factor f2 prediction of electroweak theory. Such an

experiment would be one of the rare occasions, where a strong test of the underlying structure itself of the Standard model becomes available.

Supersymmetry search in the LHC era: - one could expect small deviations in the low-energy tests, such as deviations from

CKM unitarity, but no effect at the LHC, especially if the supersymmetry spectrum is below one TeV, but the spectrum is compressed, or if some of the superpartners are light and others are heavy (a variant on the “split-SUSY” scenario)

Hartmut Abele, Atominstitut, TU Wien 32

Participating Institutions:

• IST Braunschweig

• Univ. Heidelberg• ILL

• Univ. Jena

• Univ. Mainz

• Priority Areas• CP-symmetry violation and particle physics in the early universe. • The structure and nature of weak interaction and possible extensions of

the Standard Model. • Tests of gravitation with quantum objects • Charge quantization and the electric neutrality of the neutron.

• New Infrastructure (UCN-Source, cold Neutrons)- * Coordinators first round (S. Paul, H.A. )

DFG/FWF Priority Programme 1491 : Precision experiments in particle- and astrophysics with cold and ultracold neutrons,

• Exzellenzcluster ‚Universe‘ München

• Techn. Univ. München*

• PTB Berlin

• Vienna University of Technology*

Priority Programme 1491

Research Area A: CP-symmetry violation and particle physics in the early universe- Neutron EDM E = 10-23 eV

Research Area B: The structure and nature of weak interaction and possible extensions of the Standard Model - Neutron b-decay V – A Theory

Research Area C: Test of gravitation with quantum interference - Neutron bound gravitational quantum states

Research Area D: Charge quantization and the electric neutrality of the neutron- Neutron charge

Research Area E: New measuring techniques- Particle detection- Magnetometry- Neutron optics

Experiment PERC- PERC, a clean, bright and versatile source of neutron decay products

(Maerkisch) - Proton spectroscopy (Heil, Zimmer)- Electron spectroscopy (Abele)- Neutron polarisation + analysis with 10-4 accuracy (Soldner)- design of the beam line for PERC (Soldner, Jericha)- Development of a non-depolarising neutron guide needed for PERC

(Schmidt)

Measurement of the neutron lifetime- O. Zimmer et al.

Measurement of n -> H- S. Paul et al.

Priority area B (first 3 years round):Novel experiments on neutron beta-decay

SM tests on 10-4 level

Theory- Recalculation of corrections induced by the “weak magnetism”, the

proton recoil and the radiative corrections.- A. Ivanov, M. Pitschmann, and N. Troitskaya, Phys.Rev. D88, 073002 (2013),

1212.0332.

Experiment PERC- High statistic measurements: - Today: High Average Flux: = 2 x 1010 cm-2s-1

- Decay rate of 1 MHz / metre- Thesis C. Klauser (2013) Polarizer P/P = 10-4 , Spin Flipper f/f = 10-4


Proton Electron Radiation Channel: B. Maerkisch

D. Dubbers et al., NIM A 596 (2008) 238 and arXiv:0709.4440G. Konrad et al. (for the PERC collaboration), J. Phys.: Conf. Ser. 340 (2012) 012048

=0.5T

cold

Versatile: A, B, C, a, b, κ, …

Sensitivity: • improved by up to 2 orders of magnitude

• high phase space density

Systematics: • 10-4 (for e-)

• precise cuts in dΩe:

Requirements: • no local field minima

• adiabaticity criterion

• B1 homogeneity 10-4 in e/p beam

0 0

sin

sin

B

B

Superconducting Magnet

8.9.2014 38

Preliminary Magnet Design

L = 11.3m

Precision experiments in particle and astrophysics with cold and ultracold neutronsPriority Programme 1491

6 T

1.5 T

Status:Magnet in productionInstallation in 2016

Physikalisches InstitutUniversität Heidelberg

1220

1 BB

39

G. Konrad: R x B Spectrometer

R×B Drift Momentum Spectroscopy

- Small drift distances (cm)

Xiangzun Wang, G. Konrad et al., NIM A (2012), DOI 10.1016/ j.nima.2012.10.071

+ Adiabatic transport of particles+ Low momentum measurements+ Large acceptance of θ0

+ Small corrections for θ0

Last Coil of PERC

Tilted Coils

e-/p+ beam

Detector

Aperture

y

z

x

y

xz

RxBvd qR²B²

B3=0.15T

B2=0.5T

ElectronsProtons

D

1 1(cos )

2 cod

sdT

pD

qBv t

D

RB

α

Hartmut Abele, Technische Universität München 41

SOURCE OF ERROR COMMENT SIZE OF CORRECT.

SIZE OF ERROR:

non-uniform n-beamfor ΔΦ/Φ = 10 % over 1 cm width

2.5·10−4 5·10−5

other edge effects on e/p-window for worst case at max. energy 4·10−4 1·10−4

magn. mirror effect, contin's n-beam 1.4·10−2 2·10−4

magn. mirror effect, pulsed n-beam for ΔB/B = 10 % over 8 m length 5·10−5 <10−5

non-adiabatic e/p-transport 5·10−5 5·10−5

background from n-guide}is separately measurable

2∙10−3 1·10−4

background from n-beam stop 2·10−4 1·10−5

backscattering off e/p-window 2·10−5 1·10−5

backscattering off e/p-beam dump 5∙10−5 1∙10−5

backscatt. off plastic scintillator}for worst case

2∙10−3 4·10−4

~ same with active e/p-beam dump − 1·10−4

neutron polarisation present status 3·10−4 1·10−4

Dubbers, Baessler, Märkisch, Schumann, Soldner, Zimmer, H.A., arXiv 2007

PERC Collaboration

B. MärkischU. SchmidtD. DubbersH. MestL. RaffeltC. RoickN. RebrovaC. ZienerR. MaixB. Windelband

H. AbeleE. JerichaG. KonradJ. ErhartC. GösselsbergerX. WangH. FillungerM. HorvathR. Maix

J. KlenkeT. LauerH. SaulK. Lehmann

T. SoldnerO. ZimmerC. Klauser

W. HeilM. Beck

Heidelberg Vienna

FRM II, MunichGrenoble

8.9.2014 42CKM 2014, Vienna - Bastian Märkisch

Reserva


PERKEO II: Polarisation

44

Single Polariser: X-SM Geometry:

New polarisation technique: X-SM (crossed super mirror) polarisers Kreuz et al., NIM A 547, 583 (2005)

New analyser technology: 3He Spin Filters

Average polarisation: 99.7(1)%, spin flip efficiency 100.0(1)%Correction 4 times smaller, uncertainty 3 times smaller

wavelength

8.9.2014 CKM 2014, Vienna - Bastian Märkisch

PERKEO II: Background

8.9.2014 45

shutter up

shutter down

closed closed

Shutter Down – Shutter Up, Detector 1

• Overall S:B = 8:1 in fit region• Background variation due to changes

of neighbouring instruments: reduced data set (70%)

• Beam-related background determined by extrapolation procedure, Reich al., NIM A 440.

Only 1/1700 of the electron rate in signal region (previous: 1/200)

PERKEO II: Error Budget


AA /Mund et al., PRL 110 (2013)

PERKEO II Result, 2013


APNN

NNA c

v21

exp

Combined, including corrections:A = −0.11972 (45)stat(+32

-44)sys = −0.11972(+53-65); = −1.2761(+14

-17)

Fit: Adet 1 = −0.11846(64)stat Fit: Adet 2 = −0.12008(64)stat

Difference in results for both detectors in agreement with expectation from magnetic mirror effect.

PERKEO II: Combined Result


Combine all PERKEO II results:

H. Abele et al., Phys. Lett. B 407, 212 (1997) A = - 0.1189(12)H. Abele et al., PRL 88, 211801 (2002) A = - 0.1189(8)D. Mund et al., PRL 110, 172502 (2013) A = - 0.11972(+53

-65)

Final Perkeo II result:A = - 0.11926(+47

-53) ΔA/A = 4.2 ∙ 10-3

λ = - 1.2748(+13-14) Δ λ / λ = 1.1 ∙ 10-3

Conservative treatment of correlated errors:detector calibration and uniformity, background determination, edge effect, radiative correction

49M. Pitschmann, A. Ivanov, Atominstitut, Vienna University of Technology

Coefficient A

55Hartmut Abele, Vienna University of Technology

Coefficient C

56Hartmut Abele, Vienna University of Technology

Error budget B

Error Budget C

58

Hartmut Abele, Technische Universität Wien Bastian Märkisch Hartmut Abele CKM2014 Neutron Beta...

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