nab ill 2011nab.phys.virginia.edu/slides/nab_ill_2011.pdf · 2011-07-14 · neutron lifetime...

The planned Nab/abBA/PANDA spectrometer

Stefan Baeβler

The Spallation Neutron Source SNS in Oak Ridge, TN

Linear H- accelerator Accumulator ring (buncher)

Target

TargetGuide Hall

Usage of neutrons @ SNS

11A - Powder Diffractometer Commission 2007

7 - Engineering Diffractometer IDT CFI Funded C i i 2008

9 –VISION

12 - Single Crystal Diffractometer Commission 2009

Commission 2008

6 - SANS Commission 2007

4B - Liquids

5 - Cold Neutron Chopper Spectrometer Commission 2007

13 - Fundamental Physics Beamline Commission 2008

4A - Magnetism Reflectometer C i i 2006

ReflectometerCommission 2006

14B - Hybrid Spectrometer Commission 2011

3 - High Pressure Diffractometer Commission 2008

Commission 2006

18 - Wide Angle

17 - High Resolution Chopper Spectrometer

15 – Spin Echo

1B - Disordered Mat’lsCommission 2010

2 - Backscattering Spectrometer Commission 2006

18 Wide Angle Chopper Spectrometer Commission 2007

Commission 2008

Performance of FNPB beamline

Wrap-around neutrons

Measured (@1 MW) neutron capture flux at FNPB beam exit: 9c 2

14 10 @ 1.4 MWcm s

F = ´ ⋅

Neutron beta decay

p+e-

n

n

e

Beta Decay in the Standard Model

60Co

I

I

e-

≠

Fermi’s golden rule:2

weak2 decay probability i f f H i

Parity Violation found by Wu et al, 1956

5G Ve-

60Co

ud 5Fweak 5 h.c.

21 μ μ e

GH p γ γ γ n e γ γ γ νV

3 Helicity1 Quark mixing 2 Nucleon structure 3. Helicity

… of elementary fermions: –p/E,

μ- νμ

1. Quark mixing

2 95%V

2. Nucleon structure effects

gV = GF·Vud·1

… of elementary anti-fermions: +p/E

e

d u

s c

2ud 95%V

gA = GF·Vud·λ

No nuclear structure effectse-

e

epb t

c

(for neutrons)

Observables in Neutron Beta Decay

pe-

n e

Jackson et al., PR 106, 517 (1957):

Observables in Neutron beta decay, as a function of generally possible coupling constants (assuming only

22 22 1 3Vdw G E

pn

e

generally possible coupling constants (assuming only Lorentz-Invariance)

2 ee1 3 1 b md E p p

d eue

1 3F VG EdE

2 ee

e

e e

ee

1 3 1

+

a b

A B

dw EE

p pE E

p p p pD

Fierz interference term 0b

e en

e e

+ A Bp p p pE E E E

D

2 R Beta-Asymmetry

Neutrino-Electron-Correlation

2

Re2

1 3A

2

2

1a

u1 2 2

e2

n d2 1 3FG V E

Neutron lifetime

21 3

The Standard Model Parameters Vud and λ

νe

2

1pFermi-Decay:

gV = GF·Vudνee- e- A = 0S = 0, mS = 0

n

Gamow-Teller-Decay:p

2

1 νe νee- e- A = 0S = 1, mS = 0y

gA = GF·Vud·λ

p e- νe A = -1S = 1, mS = 1

n1 cos ,ee

e

pdw A pE

, S

(after D. Dubbers, Prog. Part. Nucl. Phys. 26, 173 (1991)

Two unknown parameters, gA and gV, need to be determined in 2 experiments

1. Neutron-Lifetime: 1 2 2n V A3g g n 885 s

2

22 0.11 3

A

A

V

gg

2. Beta-Asymmetry:

Neutron Lifetime Measurements

Decrease of Neutron Counts N with storage time t: N(t) = N(0)exp{-t/τeff}

1/ τeff = 1/τβ+1/τwall losses895

Spivak 88

Nesvizh.92

Byrne 96

Arzumanov Nico 05

PDG2010

890

me

[s]

Mampe 89 00 PDG2010

Pichlmaier 10

Serebrov 08885

Neu

tron

life

tim

Mampe 93Serebrov 05

Serebrov 10875

880

Many new attempts mostly with UCN in magnetic bottles: Ezhov et al (ILL PNPI Gatchina)

1988 1992 1996 2000 2004 2008 2012Experiment publication

Many new attempts, mostly with UCN in magnetic bottles: Ezhov et al. (ILL, PNPI Gatchina), Arzumanov et al. (Kurchatov Inst., ILL), Liu et al. (Indiana), Paul et al. (TUM), Huffman et al. (NIST, NCSU), Nico et al. (NIST), Zimmer et al., (ILL) are (at least) under construction.

The Beta Asymmetry

p+

n

e-

-1.255

e

Electron Detector (Plastic Scintillator)

Yerozolimski

Liaud

PDG20101 265

-1.26

( )

Decay Electrons

PERKEO I

Mostovoi

PDG2010

-1.27

-1.265

λPolarized Neutrons

Decay ElectronsPERKEO II

UCNA

PERKEO II,prelim-1.28

-1.275

1985 1990 1995 2000 2005 2010Publication year

Ongoing funded experiments:Split Pair Magnet

Magnetic Field PERKEO II

Ongoing funded experiments:UCNA (NCSU, LANL), PERKEO III (Heidelberg), PERC (Europe)

Use of coupling constants in Primordial Nucleosynthesis

W±

e-p

W±

νepBefore Phase Transition:

Equilibrium W±

e-p

νen

n + νe ↔ p + e-

e+n

n + e+ ↔ p + νe

After Phase Transition (some minutes

n ↔ p + e-+ νe

νen

After Phase Transition (some minutes after Big Bang):

n + p→ d + γ d + d→ 3He + n → t + p

d + 3He→ 4He + pd + He→ He + p

Then the Primordial Nucleosynthesis stops, as there are no stable nuclei with A = 5, 8, and as h f di

…..

the free neutrons die out.

Stronger coupling constants in n ↔ p reactions⇒ Phase transition later⇒ nucleon density lower after phase transition⇒ less 4He, more d

Search for Standard Model Parameters

0.980

0.975ft(0+→0+) [Hardy09]ft(0+→0+) [Liang09 – DD-ME2]

Kaons+Unitarity [PDG 2010]

0.970V ud

ft(0+→0+) [Liang09 – PKO1] PIBETA [Pocanic04]

0.965 PDG

201

0]

010]

0 960λ

[P

A[U

CN

A 2

0

-1.290 -1.280 -1.270 -1.260λ = gA/gV

0.960

A [PERKEO II, prel.]

Unitarity and superallowed nuclear decaysV Telegdi 1977:V. Telegdi, 1977:I would like to say that the theory of β-decay is the theory of the decay of the neutron. I have always thought that nuclear β-decay experiments were only done faute de mieux: … If you do not know how to do the one experiment, you take the average of twenty.

( )

22 2V F ud

2ud 2

12 1 V

Ft g G V

VG Ft

µ =

µ+D( )F2 1 RG Ft+D

2 2 21 VV Vuud s ub1 VV V= - -(Dubbersaverage)

Liang et al., PRC 79, 064316 (2009)Dubbers, Schmidt, RMP (2011), in press

Possible Tests of the Standard Model

1 S h f Ri ht h d d C t (l t i hth d d) W ?

Multiple determinations (nuclear physics, other correlation coefficients) overconstrain problem, enable:

1. Search for Right-handed Currents (leptons are righthanded): WR?

2. Search for Scalar and Tensor interactions (neutrinos have opposite handedness to electrons – 4 new coupling constants possible):

Leptoquarks? Charged Higgs Bosons? Supersymmetry?

3. Test of the Unitarity of the Cabbibo-Kobayashi-Maskawa-Matrix:

ud u ubsd ' dVV V

Extra Z bosons? Supersymmetry? 4th quark generation?

2 95%Vcd cs cb

td td tb

s ' sb ' b

V V VV V V

d u

s c

2ud 95%V

2us 5%V

us2 2

ubu2

d 1 ?V VV+ + = +b t

c2

ub 0.000015V

Determination of the Coupling Constants

νe

2

1pFermi-Decay:

gV = GF·Vudνee- e- a = 1

n

Gamow-Teller-Decay:p

2

1 νe νee- e- a = 1y

gA = GF·Vud·λ

p e- νe a = -1

1 cos ,ee

vdw a p pc

Two unknown parameters, gA and gV, need to be determined in 2 experiments

1. Neutron-Lifetime: 1 2 2n V A3g g n 885 s

A

V

gg

2b. Neutrino-Electron-Correlation a:2

2

1 ~ 0.11 3

a

e-

Idea of the cos θeν spectrometer Nab @ SNS

p n

e

epKinematics:

• Energy Conservation:

• Momentum Conservatione,max eEE E

Proton phase space (Dalitz plot) Probability (arb. units)1 5

1 cosee

e

pdw aE

e• Momentum Conservation

2 2 2e ep 2 cos ep p p p p

cos θeν = 1

Proton phase space (Dalitz plot) Probability (arb. units)

1

1.25

1.5Ee =

236 keV700 keV

[MeV

2 /c2 ]

0.75

1

75 keV 22p emin, max

Edges:

Slope:

p p p

p p2

[

0.25

0.5 cos θeν = 0cos θeν = -1 450 keV

2ep

e

Slope:

1 cos epa pE

Ee [MeV]

00 0.2 0.4 0.6 0.8Alternative approaches: aSPECT (Mainz, ILL), aCORN (Tulane, NIST)

The asymmetric version of Nab @ SNS

30 kV

Advantages of asymmetric configuration:

D i f i I d fli h h

SegmentedSi detector

TOF region• Detection function: Improved flight path length

• Reduced sensitivity to electrostatic and ti t ti l i h iti

magnetic filterregion (field B0)

g(field rB·B0)

magnetic potential inhomogeneities

• Avoid deep Penning trap

• Statistical uncertainty: Bigger decay

decay volume (field rB,DV·B0)

0 kV y gg yvolume vs. angular acceptance

• Polarized experiment (abBA, PANDA) still possible

0 kV

0 kV

Neutronbeam

0 kV

The cosθeν spectrometer Nab @ SNSut

ion

2ep

e

1 cos epa pE

SegmentedSi detector

-30 kV

p p2di

strib

u

2pcos 1e p

2pcos 1e p

magnetic filteri (fi ld B )

TOF region(field rB·B0)

107

pp2 [MeV2/c2]

0.0 0.5 1.0 1.5

Ee = 550 keVregion (field B0)

decay volume (field rB,DV·B0)

nt ra

te 106

107

Neutronbeam

0 kV

Sim

ulat

ed c

oun

Ee = 300 keV

104

105

Ee = 500 keV• Measurement of Ee and tp for each event

B k d i th h i id f l t d

0 kV

0.00 0.02 0.04 0.06 0.081/tp

2 [1/μs2]

103

10Ee = 700 keV • Background suppression through coincidences of electron and

proton.

• Long flight path improves spectrometer

Determination of pp through tp: The magnetic field

30 kV p

||pz

SegmentedSi detector

TOF regionMagnetic Field

abat

ic

ersi

on

x

magnetic filterregion (field B0)

g(field rB·B0)

Proton Trajectory

Adi

aco

nv

z

decay volume (field rB,DV·B0)

0 kV

p

||p

x

0 kV

0 kV

Neutronbeam z • Measurement of Ee and tp for each

event

• Background suppression through 0 kV

x

g pp gcoincidences of electron and proton.

• Long flight path improves spectrometer

Silicon detector for Nab / abBA / PANDA

Front side Back side

Segmented ion-implanted silicon detector with fast readout electronics:

• Thickness 2 mm (less for testing)

• Thin dead layer of < 100 nm silicon (measured!):• Thin dead layer of < 100 nm silicon (measured!):

Energy loss for 30 keV protons: < 11 keV (measured!)

• 127 channels

Sufficiently small count rate/pixel,

Allows to find electron and correlated proton.

Detector properties: proton response

Proton beam, 32 keV, 50 s-1

Detector thickness: 500 μm

Detector properties: proton spectrum (II)ld 103

104

105

average energyloss: 11 keVThreshold?

Worst case simulation (dead layer: 100 nm Si)

Energy calibration: Si 1.0mm detector

Yie

l

101

102

103

Energy calibration: Si 1.0mm detector

Cd-109 dataProton data75

10

deposited Ep [keV] (w/o electronic noise)0 5 10 15 20 25

E (k

eV)

50Threshold lost protons efficiency slope

8 keV 0.19% 110(30) ppm/keV10 keV 0.20% 131(31) ppm/keV12 k V 0 21% 165(32) /k V

25 dead layer: 65 nm(but pulse heightdefect neglected)

12 keV 0.21% 165(32) ppm/keV14 keV 0.28% 304(76) ppm/keV

channels0

0100 200 300

For uncertainty in a, we assume a threshold of 10 keV and direct measurement of efficiency slope to 50%.

Electron energy measurement with backscattering suppression

30 kV10 4

10 5

detected Ee for e- in lower detector

detected Ee with only lower detector

D t t fSegmentedSi detector

TOF region

Yie

ld

10 1

10 2

10 3 Detector response forincoming Ee = 300 keV

magnetic filterregion (field B0)

g(field rB·B0)

detected Ee [keV]

1

10

0 50 100 150 200 250 300

decay volume (field rB,DV·B0)

0 kV

e [ ]

1000incoming Ee = 300 keV0 kV

0 kV

Neutronbeam

Yie

ld

10

100

0 kV

electron TOF between detectors [ns]

1

0 50 100 150-50-150 -100

Electron energy measurement with backscattering suppression

30 kV10 4

10 5

detected Ee for e- in lower detector

detected Ee with only lower detector

D t t fSegmentedSi detector

TOF region

Yie

ld

10 1

10 2

10 3 Detector response forincoming Ee = 300 keV

magnetic filterregion (field B0)

g(field rB·B0)

detected Ee [keV]

1

10

0 50 100 150 200 250 300

decay volume (field rB,DV·B0)

0 kV • Measurement of Ee (and tp) for each event

e [ ]

0 kV

0 kV

Neutronbeam

e ( p)

• Backscattering suppression through adding energies of both detectors.

• Reconstructing of electron energy needs 0 kV g gytime resolution of < 20 ns

Detector properties: Speed

Extraction of a in Nab

2ep

e

1 cos epa pE

A.U

.]

p p2

dist

ribut

ion

2pcos 1e p

2pcos 1e p

late

d co

unts

[A

Ee = 300 keV0.0 0.5 1.0 1.5

Ee = 550 keV

Sim

ul Ee = 500 keVEe = 700 keV

pp2 [MeV2/c2]

0.002 0.004 0.00601/tp

2 [µs-2]

Data analysis: Use edge to determine or verify the shape of the detection function

pp

p pcos ( )m dztp zq

= ò

shape of the detection function.

Then, use central part to determine slope and the correlation coefficient a.

Detailed spectrometer magnet design0.50

37.5014.7525.90

c1i

z

c1o eld

[T]

B

3

4

5

B (on axis)

Si detector

0.03

25.28 43.81

481.25

c1ic1o

Mag

netic

f ie

1

2

Bz (on axis)

Decayvolume

4 m flight path is omitted here466.25

5.00

4.34

10.5220.5838.16

29 94

3.193.28

4.9312.92

8 00

16.77 rc4i

c3ic2i

c4o

c3oc2o

M

z [m]0 0 1-1 2 3 4 5

5Filter

41.66

4.343.13

3.13

29.9416.4130.24

8.00c5ic5o

cfie

ld[ T

]B

2

3

4 Decayvolume

Filter

67.0914.7725.90

0 20-20 10-10-30

Bz (on axis)Bz (off axis)M

agne

tic

0

1

2

0.47

c6ic6o z [cm]

Nab setup, about to scale

B

Passive Antimagnetic Shield200cm

300cm

Top view:

Beam shutter

Beam stop

Beam pipe

200cm

Beam shutter

Spectrometer magnetNeutron guide

Side view: Detector supportt

Magnet Pit

Prototype detector spectra

Source: Cd 109. Preamp: LANL homemade. Micron detector, thickness: 1.5 mm

18.5 keV e-

62.5 keV e-

84.2,87.3,87.9 keV e-

Kelvin Probe: Tool to measure Work Functions

VMaterial 1 Material 2

Φ2 Φ2

Material 1 Material 2 Material 1 Material 2

VC

Φ1

EF,1

2

EF,2Φ1 Φ2 Φ1

EF 1 EF 2

EF,2

EF 1

VC

___

+++

+

F,1 F,2 F,1

VBias = -VC

2 M t i l ith diff t

Electrical Connection:

→ Charging, until Fermi Bi V lt2 Materials with different

work functions, isolated

1st material: to be tested

2nd t i l ti ith k

g g,levels are equal

→ External electric field

→ If Material 2 is moved:

Bias Voltage

→ Charge disappears, no external electric field

N t if M t i l 2 i2nd material: tip with known work function

Capacitance changes, voltage is constant, therefore charge has to change (current)

→ No current if Material 2 is moved

Kelvin Probe: First results from early work on aSPECT

Work Function [meV]

30

35

404900

[ ]

20

25

30ht

[mm

]4950

5000

5

10

15Hei

gh 5000

5050

0 50 100 150 200 250 300 3500

5

Angle [°]

5100

g [ ]

In collaboration with Prof. I. Baikie, KP Technologies

Now: Better coating

Work Function [meV]

303540

4900

15202530

Hei

ght [

mm

]

4950

5000 (arbitrary offset added)

16

0 50 100 150 200 250 300 35005

1015H

5050

5100

8

12

ight

[mm

]0 50 100 150 200 250 300 350Azimuth angle [°]

5100

In collaboration with Prof. I. Baikie, KP Technologies

0

4H

ei

0 4 8 120

Width [mm]Thanks to:Rachel Hodges (undergraduate research prize), Gertrud Konrad, Sean McGovern (Masters), Henry Bonner

Uncertainty budgetPLANNED systematic uncertainty budget:i i l i b d PLANNED systematic uncertainty budget:PLANNED statistical uncertainty budget:

lower Ee cutoff none 100 keV

100 keV

300 keV

Experimental parameter Systematic uncertainty Δa/a

Magnetic fieldcurvature at pinch 5 10 4

upper tp cutoff none none 40 μs 40 μs

Δa 2.4/√N 2.5/√N 2.5/√N 2.6/√N

Δa (Ecal, l 2 5/√N 2 6/√N 2 7/√N 2 7/√N

... curvature at pinch 5·10-4

… ratio rB = BTOF/B0 2.5·10-4

… ratio rB,DV = BDV/B0 3·10-4

Length of the TOF region (*)Electrical potential inhomogeneity:variable) 2.5/√N 2.6/√N 2.7/√N 2.7/√N

Δa (Ecal, lvariable, inner 70% of data)

4.1/√N 4.1/√N 4.1/√N 4.1/√N

Electrical potential inhomogeneity:… in decay volume / filter region 5·10-4

… in TOF region 1·10-4

Neutron Beam:position 4·10-4

About 2×109 events can be detected in 6 weeks (Decay volume V = 246 cm3, decay density n = 20 cm-3 12 7 % of decay protons

… position 4 10… profile (including edge effect) 2.5·10-4

… Doppler effect smallUnwanted beam polarization can be made smallAdiabaticity of proton motion 1·10-4density nd = 20 cm 3, 12.7 % of decay protons

go to upper detector, 80% duty factor)

→ (Δa/a)stat < 1×10-3 can be reached

Adiabaticity of proton motion 1 10Detector effects:… Electron energy calibration (*)… Electron energy resolution 5·10-4

… Proton trigger efficiency 2.5·10-4

Compare to Δa/a = 5 % of existing experimental results

gg yResidual gas smallBackground smallAccidental coincidences smallSum 1·10-3

Other ongoing experiments: aSPECT

i fi ld y ra

te w

(E)

Magnetic field

Protondetector

Analyzing PlaneB 0 314 T and for a = -0.103 (PDG 2006)

Dec

ay

Proton spectrum for a = +0.3

Superconducting

Retardationvoltage U

•+

•+

•+

•+

detectorBA = 0.314 T0 200 400 600

( )

Proton kinetic energy E [eV]

magnet

ProtonsDecayVolume= 1.55 TB0

Mirror voltageNeutrons

•+

•+

•+

•+

Leading uncertainty probably trapped particle background, (Δa/a)background = 0.61%

Other ongoing experiments: aCORN @ NIST

solenoid

Bproton

electroncollimator

electron

decay volume

+Vneutronbeam

protondetector proton

collimator

electrondetector

] l t t

4Simulated Data

pe

pp

pν

ton

TOF

[s]μ late protons

3

2Expected total uncertainty of Δa/a ~ 1 %

(limited by systematics)

l t f th il bl t dpr

ot6008004002000

early protons2

180-300 keV

• only part of the available neutron decays used

• I find it hard to determine the acceptance i l

beta kinetic energy [keV]

precisely

The determination of the Fierz Interference term

2 ee

e

1 3 1 mdw E bE

Electron spectrum:

e

Systematic uncertainties: nits

)

Sy1. Electron energy determination

Yie

ld(a

rb.u

n

b = +0.1SM104

105

Detector response to decay

Y SM

Yie

ld

102

103

electron with Ee = 300 keV

0 200 400 600 800Ee,kin (keV)

2% of events in tail(deadlayer,external bremsstrahlung)1

101

0 50 100 150 200 250 300

Δb ~ 3×10-3 can be reached (systematics limited)

2. Background

detected Ee [keV]

A/B at SNS or NIST: abBA / Nab / PANDA

Segmented Si detector

• A: reflect all protons to bottom detector, use top detector for electrons

TOF region (field rB·B0)

S iAFPSpin

3He

• B: detect protons at top

decay volume (field rB,DV·B0)

Supermirror(3He)

SpinFlipper

PolarimeterAFP

• Main uncertainties in PERKEO II: statistics, detector, polarization, background

• Superior detector energy resolution, good enough time resolution

K i id t i b k d• Keep coincidences to improve background

• Asymmetric detector: Filter improves on systematics; statistics @ SNS is an issue for A

• Polarization measurement seems manageable (XSM or He-3)

Uncertainty budget for APLANNED t ti t i t b d tPLANNED systematic uncertainty budget:PLANNED statistical uncertainty budget:

Experimental parameter Systematic uncertainty ΔA/ARelevant only for

lower Ee cutoff none100 keV

200 keV

250 keV

∆A 4.3/√N 4.8/√N 7/8/√N 11.9/√N

Nd is the number of decays. Only 13% are detected, due to asymmetric configuration.

Electrical potential inhomogeneity:y

B/CNeutron Beam:… position irrelevant… profile (including edge effect) small

D l ff ll

∆A 4.3/√N 4.8/√N 7/8/√N 11.9/√N

Nd = 2×109 decay events (40 live days at SNS)→ (ΔA/A)stat = 1×10-3 can be reached

ibl i

… Doppler effect small… Beam polarization < 10-3

Detector effects:… Electron energy calibration 2·10-4

… Electron energy resolution smallPossible improvements:• He3?• NIST NG-C?

… Electron energy resolution smallResidual gas smallBackground smallSum TBD

3Our goal is a total uncertainty of ΔA/A = 10-3 or better (same for B/C, not discussed)

Competition:

• UCNA: Goal ΔA/A = 2·10-3 (A. Young, NSAC), check of cold beam experimentsUCNA: Goal ΔA/A 2 10 (A. Young, NSAC), check of cold beam experiments

• UCNB: Goal ΔB/B = 10-3 , but electric potential homogeneities have to be ΔU < 0.3 mV

• PERC: Goal ΔA/A = 3·10-4

Time schedule

As presented at NSAC meeting,

assuming NO major technical or funding delays

2011 2012 2013 2014 2015 2016 2017 2018

design

Procurement, fabrication, optimization

installation and data takingtaking

switchover

data takingg

Nab abBA / PANDA

The experiment might move to NIST NG-C, probably for the polarized program.

Sensitivity to left-handed S-T couplings

“present limits”( )

muon decay

neutron and nuclear decays(survey, 68% C.L.)

(68% C.L.)“90% C.L.”

superallowed0?0 d++l d 0?0 decays(68% C.L.)

nuclear decays((In), 90% C.L.)P 107

Present limits (n decay data)SM is in the origin of this plot

Future limits,assuming a = -0.1059(1), A = -0.1186(1) ,B = 0.9807(30), C = -0.23785(24), τn = 882 2(13) s b = 0±0 003882.2(13) s, b 0±0.003

Model-dependent predictions: Supersymmetry, leptoquarks, …

Analysis similar to G. Konrad, S.B. et al., ArXiv:1007.3027

Sensitivity to right-handed S-T couplings

Present limits (n decay data)SM is in the origin of this plot

Future limits,assuming a = -0.1059(1), A = -0.1186(1) ,B = 0.9807(30), C = -0.23785(24), τn = 882.2(13) s0.9807(30), C 0. 3785( ), τn 88 . ( 3) s

Analysis similar to G. Konrad, S.B. et al., ArXiv:1007.3027

The Nab collaboration

R. Alarcona, L.P. Alonzib , S.B.b (Experiment Manager), S. Balascutaa, J.D. Bowmanc (Co-Spokesmen), M.A. Bychkovb, J. Byrned, J.R. Calarcoe, T.V. Ciancioloc, C. Crawfordf, E. Frležb, M.T. Gerickeg, F. Glückh, G.L. Greenei, R.K. Grzywaczi, V. Gudkovj, F.W. Hersmane, A. Kleink, J. Martinl, S. McGovernb, S. Pageg, A. Palladinob, S.I. Penttiläc (On-site Manager), D. PočanićcJ , S G , S g , , S (O g ),(Co-Spokesmen), K.P. Rykaczewskic, W.S. Wilburnk, A.Youngm

a Department of Physics, Arizona State University, Tempe, AZ 85287-1504b Department of Physics, University of Virginia, Charlottesville, VA 22904-4714c Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831d Department of Physics and Astronomy, University of Sussex, Brighton BN19RH, UKe Department of Physics, University of New Hampshire, Durham, NH 03824f Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506g Department of Physics, University of Manitoba, Winnipeg, Manitoba, R3T 2N2, Canadah IEKP, Universität Karlsruhe (TH), Kaiserstraße 12, 76131 Karlsruhe, Germanyi Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996j Department of Physics and Astronomy, University of South Carolina, Columbia, SC 29208kk Los Alamos National Laboratory, Los Alamos, NM 87545l Department of Physics, University of Winnipeg, Winnipeg, Manitoba R3B2E9, Canadam Department of Physics, North Carolina State University, Raleigh, NC 27695-8202

Tasks of UVa group: Spectrometer design, Superconducting magnet, Proton source

Summary

• Precise and reliable results from neutron physics are preferred to extract information about the Standard Model withoutto extract information about the Standard Model without nuclear structure uncertainties

• Main difference to European effort (PERKEO II/III, aSPECT, p ( , ,PERC): less count rate, e--p coincidences

• Status of Nab spectrometer: Funding application at DOE to perform Nab at the FNPB beamline at the SNS. Second funding application to NSF (MRI)

E i i i d ( li i ) d f NSAC• Experiment is received (preliminary) endorsement of NSAC last week (rank 4 out of 5 out of 15)

Thank you for your interest !!