[PPT] - Precision Measurement of a and b in Neutron Decay The Nab/abBA PowerPoint Presentation

SLIDE 1

Precision Measurement of a and b in Neutron β Decay

The Nab/abBA Experimental Program

L. Peter Alonzi III, for the Nab Collaboration

University of Virginia

April APS Meeting, Denver, 03 May 2009

SLIDE 2

Motivation Spectrometer

Outline

Neutron Decay Theory and Measurement Principles The Nab Spectrometer

L.P. Alonzi (UVa) The Nab Experiment 03 May ’09 2 / 11

SLIDE 3

Motivation Spectrometer

World Neutron Experimental Results and Nab goal

Electron-neutrino parameter a: Experimental results            −0.1054 (55) Byrne et al, [2002] −0.1017 (51) Stratowa et al, [1978] −0.091 (39) Grigorev et al, [1968] −0.103 (4) PDG, [2008] Nab goal: ∆a a ≃ 1 × 10−3 Fierz interference term b: Experimental results

none

Nab goal: ∆b ≃ 3 × 10−3

L.P. Alonzi (UVa) The Nab Experiment 03 May ’09 3 / 11

SLIDE 4

Motivation Spectrometer

World Neutron Experimental Results and Nab goal

Electron-neutrino parameter a: Experimental results            −0.1054 (55) Byrne et al, [2002] −0.1017 (51) Stratowa et al, [1978] −0.091 (39) Grigorev et al, [1968] −0.103 (4) PDG, [2008] Nab goal: ∆a a ≃ 1 × 10−3 Fierz interference term b: Experimental results

none

Nab goal: ∆b ≃ 3 × 10−3

L.P. Alonzi (UVa) The Nab Experiment 03 May ’09 3 / 11

SLIDE 5

Motivation Spectrometer

Neutron Decay Rate

ν e p n W

dw dEedΩedΩν ≃ keEe(E0 − Ee)2 ×

1 + a
ke ·

kν EeEν + bme Ee + σn ·

B
kν

Eν + A

ke

Ee

a =

1−|λ|2 1+3|λ|2

A = −2 |λ|2+Re(λ)

1+3|λ|2

B = 2|λ|2−Re(λ)

1+3|λ|2

λ = GA(0) GV(0) (with τn ⇒ CKM Vud)

L.P. Alonzi (UVa) The Nab Experiment 03 May ’09 4 / 11

SLIDE 6

Motivation Spectrometer

Neutron Decay Rate

ν e p n W

dw dEedΩedΩν ≃ keEe(E0 − Ee)2 ×

1 + a
ke ·

kν EeEν + bme Ee + σn ·

B
kν

Eν + A

ke

Ee

a =

1−|λ|2 1+3|λ|2

A = −2|λ|2+Re(λ)

1+3|λ|2

B = 2|λ|2−Re(λ)

1+3|λ|2

λ = GA(0) GV(0) (with τn ⇒ CKM Vud)

L.P. Alonzi (UVa) The Nab Experiment 03 May ’09 4 / 11

SLIDE 7

Motivation Spectrometer

Decay Kinematics

Ee (MeV) pp2 (MeV2/c2) cos θeν = -1 cos θeν = 1 cos θeν = 0 proton phase space

0.2 0.4 0.6 0.8 1 1.2 1.4 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

pp2 (MeV2/c2) Yield (arb. units) Ee = 0.075 MeV 0.236 MeV 0.450 MeV 0.700 MeV

0.1 0.2 0.3 0.4 0.5 0.2 0.4 0.6 0.8 1 1.2 1.4

Ep ∼ eV and Ee ∼ 0-800 keV
For a given Ee
cos θeν is a function of p2

p only

(p2

p = p2 e + p2 ν + 2pepν cos θeν)

dw

dEedΩedΩν ≃ Constant + a p2

p

L.P. Alonzi (UVa) The Nab Experiment 03 May ’09 5 / 11

SLIDE 8

Motivation Spectrometer

Decay Kinematics

Ee (MeV) pp2 (MeV2/c2) cos θeν = -1 cos θeν = 1 cos θeν = 0 proton phase space

0.2 0.4 0.6 0.8 1 1.2 1.4 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

pp2 (MeV2/c2) Yield (arb. units) Ee = 0.075 MeV 0.236 MeV 0.450 MeV 0.700 MeV

0.1 0.2 0.3 0.4 0.5 0.2 0.4 0.6 0.8 1 1.2 1.4

Ep ∼ eV and Ee ∼ 0-800 keV
For a given Ee
cos θeν is a function of p2

p only

(p2

p = p2 e + p2 ν + 2pepν cos θeν)

dw

dEedΩedΩν ≃ Constant + a p2

p

L.P. Alonzi (UVa) The Nab Experiment 03 May ’09 5 / 11

SLIDE 9

Motivation Spectrometer

Beamline 13: Spallation Neutron Source, Oak Ridge, TN

L.P. Alonzi (UVa) The Nab Experiment 03 May ’09 6 / 11

SLIDE 10

Motivation Spectrometer

The Nab Symmetric Configuration

z (m) B0 B (T) BTOF U (104 V) Nab Spectrometer Field Profiles

1 2 3 4 0.25 0.5 0.75 1 1.25 1.5 1.75 2

L.P. Alonzi (UVa) The Nab Experiment 03 May ’09 7 / 11

SLIDE 11

Motivation Spectrometer

Geant4 Simulation

a120→

+

z

r dimensionsincm

2.0 11.8 9.0 4.6 1.0 1.5 5.0 Currentdensity:3500 A/cm2

+

25 100 0.039 2.4 1.3 1.0

a120→

2

s µ

2

TOF

0.01 0.02 0.03 0.04 0.05

4

10

3

10

2

10

a120 = 0.949 MeV/c

p

P = 1.140 MeV/c

p

P

2

s µ

2

TOF

0.01 0.02 0.03 0.04 0.05

5

10

4

10

3

10

2

10

1

10

β a147 = 0.949 MeV/c

p

P = 1.140 MeV/c

p

P

← a147β

+

z

r dimensionsincm

2.0 6.2 2.0 11.0 Currentdensity:3500 A/cm2

+

50 400 0.014 1.3 11.0 3.0 3.4 3.9 7.0 8.4 2.4 1.0 1.3

← a147β

L.P. Alonzi (UVa) The Nab Experiment 03 May ’09 8 / 11

SLIDE 12

Motivation Spectrometer

Geant4 Simulation

Ideal Spectrometer

]

2

[(MeV/c)

2 p

P 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0.05 0.1 0.15 0.2 0.25 0.3 0.35

3

10 ×

= 300 keV

e

E 500 keV 700 keV

Practicable Spectrometer

]

2

s µ [

2

TOF 0.01 0.02 0.03 0.04 0.05 0.05 0.1 0.15 0.2 0.25 0.3

3

10 ×

= 300 keV

e

E 500 keV 700 keV

Ee Measured a Seed

0.10500

300 keV

0.10526(10)

500 keV

0.10509(10)

700 keV

0.10529(10)

L.P. Alonzi (UVa) The Nab Experiment 03 May ’09 9 / 11

SLIDE 13

Motivation Spectrometer

Basic design and features of asymmetric Nab

Segmented Si detector decay volume (field rB,DV·B0) 30 kV 0-30 kV 0-31 kV magnetic filter region (field B0) Neutron beam TOF region (field rB·B0) Stefan Baeßler, March 2009

Features:

U tolerance ∼ µV → ∼ mV
magnetic cos θ filter
no count rate penalty vs.

symmetric Nab

Height z [m]

1 2 3 4

Magnetic field B [T] z1 z2 z3

z2-z1

filterregion decayvolume detector detector expansionregion B B z (z)= (1-( )) α

2

linearfielddecay B r B (z)=

B

B r B (z)~ (smallgradient, ~10 /cm)

B,DV

3

L.P. Alonzi (UVa) The Nab Experiment 03 May ’09 10 / 11

SLIDE 14

The Nab collaboration

R. Alarcon1, L.P. Alonzi2, S. Baeßler2∗, S. Balascuta1, J.D. Bowman3†,

M.A. Bychkov2, J. Byrne4, J.R. Calarco5, V. Cianciolo3, C. Crawford6,

E. Frleˇ

z2, M.T. Gericke7, F. Gl¨ uck8, G.L. Greene9, R.K. Grzywacz9,

V. Gudkov10, F.W. Hersman5, A. Klein11, J. Martin12, S.A. Page6,
A. Palladino2, S.I. Penttil¨

a3, D. Poˇ cani´ c2†, K.P. Rykaczewski3, W.S. Wilburn11, A.R. Young13, G.R. Young3.

1Arizona State University 2University of Virginia 3Oak Ridge National Lab 4University of Sussex

5Univ. of New Hampshire

6University of Kentucky 7University of Manitoba

8Uni. Karlsruhe/RMKI Budapest

9University of Tennessee 10University of South Carolina 11Los Alamos National Lab 12University of Winnipeg 13North Carlolina State Univ. ∗Experiment Manager †Co-spokesmen

Home page: http://nab.phys.virginia.edu/