Post on 18-Jan-2022
Nab: precise experimental study ofunpolarized neutron beta decay
Dinko Pocanic, (for the Nab collaboration)
University of Virginia
4th Joint Meeting of the Nuclear Physics Divisionsof the Am. Phys. Soc. and Phys. Soc. of Japan
Kona, HI6–11 Oct 2014
Neutron beta decay observables (SM)
dw
dEedΩedΩν' peEe(E0 − Ee)2
×[
1 + a~pe · ~pνEeEν
+ bm
Ee+ 〈~σn〉 ·
(A~peEe
+ B~pνEν
)+ . . .
]where in SM:
a =1− |λ|2
1 + 3|λ|2A = −2
|λ|2 + Re(λ)
1 + 3|λ|2
B = 2|λ|2 − Re(λ)
1 + 3|λ|2λ =
GA
GV(with τn ⇒ CKM Vud)
also proton asymmetry: C = κ(A + B) where κ ' 0.275 .
⇒ SM overconstrains a, A, B observables in n β decay!Fierz interf. term b brings add’l. sensitivity to non-SM processes!
D. Pocanic (UVa) The Nab experiment: Basic definitions 10 Oct ’14/DNP2013 2 / 14
Neutron beta decay observables (SM)
dw
dEedΩedΩν' peEe(E0 − Ee)2
×[
1 + a~pe · ~pνEeEν
+ bm
Ee+ 〈~σn〉 ·
(A~peEe
+ B~pνEν
)+ . . .
]where in SM:
a =1− |λ|2
1 + 3|λ|2A = −2
|λ|2 + Re(λ)
1 + 3|λ|2
B = 2|λ|2 − Re(λ)
1 + 3|λ|2λ =
GA
GV(with τn ⇒ CKM Vud)
also proton asymmetry: C = κ(A + B) where κ ' 0.275 .
⇒ SM overconstrains a, A, B observables in n β decay!Fierz interf. term b brings add’l. sensitivity to non-SM processes!
D. Pocanic (UVa) The Nab experiment: Basic definitions 10 Oct ’14/DNP2013 2 / 14
Goals of the Nab experiment (at SNS, ORNL)
I Measure the e–ν correlation a in neutron decay with precision
∆a/a ' 10−3 or ∼ 50× better than:
current results:−0.1054± 0.0055 Byrne et al ’02−0.1017± 0.0051 Stratowa et al ’78−0.091± 0.039 Grigorev et al ’68
I Measure b (Fierz interf. term) in n decay with ∆b ' 3× 10−3
current results: none (not yet reported for n decay)
I Nab will be followed by the ABba/PANDA polarized program tomeasure A, electron, and B/C , neutrino/proton, asymmetries with' 10−3 relative precision.
Motivation:
multiple independent determinations of λ (test of CKM unitarity),
independent and competitive limits on S , T currents (BSM).
D. Pocanic (UVa) The Nab experiment: Goals and motivation 10 Oct ’14/DNP2013 3 / 14
Goals of the Nab experiment (at SNS, ORNL)
I Measure the e–ν correlation a in neutron decay with precision
∆a/a ' 10−3 or ∼ 50× better than:
current results:−0.1054± 0.0055 Byrne et al ’02−0.1017± 0.0051 Stratowa et al ’78−0.091± 0.039 Grigorev et al ’68
I Measure b (Fierz interf. term) in n decay with ∆b ' 3× 10−3
current results: none (not yet reported for n decay)
I Nab will be followed by the ABba/PANDA polarized program tomeasure A, electron, and B/C , neutrino/proton, asymmetries with' 10−3 relative precision.
Motivation:
multiple independent determinations of λ (test of CKM unitarity),
independent and competitive limits on S , T currents (BSM).
D. Pocanic (UVa) The Nab experiment: Goals and motivation 10 Oct ’14/DNP2013 3 / 14
Goals of the Nab experiment (at SNS, ORNL)
I Measure the e–ν correlation a in neutron decay with precision
∆a/a ' 10−3 or ∼ 50× better than:
current results:−0.1054± 0.0055 Byrne et al ’02−0.1017± 0.0051 Stratowa et al ’78−0.091± 0.039 Grigorev et al ’68
I Measure b (Fierz interf. term) in n decay with ∆b ' 3× 10−3
current results: none (not yet reported for n decay)
I Nab will be followed by the ABba/PANDA polarized program tomeasure A, electron, and B/C , neutrino/proton, asymmetries with' 10−3 relative precision.
Motivation:
multiple independent determinations of λ (test of CKM unitarity),
independent and competitive limits on S , T currents (BSM).
D. Pocanic (UVa) The Nab experiment: Goals and motivation 10 Oct ’14/DNP2013 3 / 14
Goals of the Nab experiment (at SNS, ORNL)
I Measure the e–ν correlation a in neutron decay with precision
∆a/a ' 10−3 or ∼ 50× better than:
current results:−0.1054± 0.0055 Byrne et al ’02−0.1017± 0.0051 Stratowa et al ’78−0.091± 0.039 Grigorev et al ’68
I Measure b (Fierz interf. term) in n decay with ∆b ' 3× 10−3
current results: none (not yet reported for n decay)
I Nab will be followed by the ABba/PANDA polarized program tomeasure A, electron, and B/C , neutrino/proton, asymmetries with' 10−3 relative precision.
Motivation:
multiple independent determinations of λ (test of CKM unitarity),
independent and competitive limits on S , T currents (BSM).
D. Pocanic (UVa) The Nab experiment: Goals and motivation 10 Oct ’14/DNP2013 3 / 14
Electron–neutrino angle from Ee and Ep
−ν
νeθ
e
n
p Conservation of momentum in n beta decay,
~pp + ~pe + ~pν = 0 ,
yields
p2p = p2
e + 2pepν cos θeν + p2ν .
Neglecting proton recoil energy, Ee + Eν = E0,so that pν = E0 − Ee. Therefore:
cos θeν is uniquely determined by mea-suring Ee and Ep (or pp ⇒ TOFp).
D. Pocanic (UVa) The Nab experiment: Principles of measurement 10 Oct ’14/DNP2013 4 / 14
Nab measurement principles: proton phase space
e (MeV)
p2 (
MeV
2 /c2 )
E
p
cos
θ eν =
-1
cos θ eν = 1
cos θeν = 0
proton phase spaceYield (arb. units)
Ee =
100 keV
300 keV
500 keV
700 keV
0
0.5
1
1.5
0 0.2 0.4 0.6 0.8
NB: For a given Ee , cos θeν is a function of p2p only.
Slope ∝ aAAAAAAAK
AAAAK
AAAAAAAAK
AAAAAAAAAAAAAK
Numerous consistency checks are built-in!
D. Pocanic (UVa) The Nab experiment: Principles of measurement 10 Oct ’14/DNP2013 5 / 14
Nab measurement principles: proton phase space
e (MeV)
p2 (
MeV
2 /c2 )
E
p
cos
θ eν =
-1
cos θ eν = 1
cos θeν = 0
proton phase spaceYield (arb. units)
Ee =
100 keV
300 keV
500 keV
700 keV
0
0.5
1
1.5
0 0.2 0.4 0.6 0.8
NB: For a given Ee , cos θeν is a function of p2p only. Slope ∝ a
AAAAAAAK
AAAAK
AAAAAAAAK
AAAAAAAAAAAAAK
Numerous consistency checks are built-in!
D. Pocanic (UVa) The Nab experiment: Principles of measurement 10 Oct ’14/DNP2013 5 / 14
I Collect and detectboth electrons andprotons from neutronbeta decay.
I Measure Ee and TOFp
and reconstruct decaykinematics
I Segmented Si det’s:
PPPPPq
LANL/Micron development
PiPPi
AK
CCOCCO
CCOCCOCCO
6
Nab principles of measurement
D. Pocanic (UVa) The Nab experiment: Principles of measurement 10 Oct ’14/DNP2013 6 / 14
Spectrometer Coil design and ~B field profile
upper detector
lower detector
NBL
NBUF
TOF TOF’
NBU’
NBL’
UDET’UDET
LDET
LDET’
neutron beam
z [m]
r [m]
0
0 0.2 0.4
5
-1
3.5 m flight path omitted
Mag
net
ic f
ield
B
[T]
0
1
2
3
4
-1 0 1 2 3 4 5
fiducialvolume
lowerdetector
upperdetector
z [m]
z [cm]
Mag
neti
c fi
eld
B
[T]
0
1
2
3
4
fiducialvolume
B (on axis)z
B (off axis)z
Filter
-30-20 -10 0 10 20 30
D. Pocanic (UVa) The Nab experiment: Principles of measurement 10 Oct ’14/DNP2013 7 / 14
Nab Si detectors (LANL-Micron development)
I 15 cm diameter
I full thickness: 2 mm
I dead layer ≤100 nm
I 127 pixels
Front
Back
D. Pocanic (UVa) The Nab experiment: Principles of measurement 10 Oct ’14/DNP2013 8 / 14
Nab Si detectors (LANL-Micron development)
I 15 cm diameter
I full thickness: 2 mm
I dead layer ≤100 nm
I 127 pixels
Front
Back
These look lovely, buthow well do they work?
D. Pocanic (UVa) The Nab experiment: Principles of measurement 10 Oct ’14/DNP2013 8 / 14
Nab Si detectors (LANL-Micron development)
I 15 cm diameter
I full thickness: 2 mm
I dead layer ≤100 nm
I 127 pixels
Front
Back
0 10 20 30 40 50 60 70 80Channels
0
5000
10000
15000
Pro
ton
no
rma
lize
d y
ield
Noise
20 25 30
1mm thick Si det.A. Salas-Bacci et al., NIM A 735 (2014) 408
35 kV15
D. Pocanic (UVa) The Nab experiment: Principles of measurement 10 Oct ’14/DNP2013 8 / 14
Analysis strategy (methods “A” and “B”)
21/t ’ [1/μs ]p
2
Yie
ld
0 0.002 0.004 0.006 0.008
E = 150 keVe
E = 300 keVe
E = 450 keVe
E = 600 keVe
E = 750 keVe
I Use edges to determine andverify shape of detectionfunction Φ(pp, 1/tp);
I Use central part of Pt(1/t2p)
(∼ 70%) to extract a.
A. parametrize edges and width of Φ(pp, 1/tp) by fitting; use central partof Φ (∼ 70%) to extract a in a multiparameter fit, and
B. specify accessible parameters of Φ by direct measurement; ⇒ treat a,µ = 1/t2p(pp), and Ndecays as free parameters in a two-step fit,
I as well as a HYBRID OF THE TWO METHODS.
D. Pocanic (UVa) The Nab experiment: Principles of measurement 10 Oct ’14/DNP2013 9 / 14
Analysis strategy (methods “A” and “B”)
21/t ’ [1/μs ]p
2
Yie
ld
0 0.002 0.004 0.006 0.008
E = 150 keVe
E = 300 keVe
E = 450 keVe
E = 600 keVe
E = 750 keVe
I Use edges to determine andverify shape of detectionfunction Φ(pp, 1/tp);
I Use central part of Pt(1/t2p)
(∼ 70%) to extract a.
A. parametrize edges and width of Φ(pp, 1/tp) by fitting; use central partof Φ (∼ 70%) to extract a in a multiparameter fit, and
B. specify accessible parameters of Φ by direct measurement; ⇒ treat a,µ = 1/t2p(pp), and Ndecays as free parameters in a two-step fit,
I as well as a HYBRID OF THE TWO METHODS.
D. Pocanic (UVa) The Nab experiment: Principles of measurement 10 Oct ’14/DNP2013 9 / 14
Analysis strategy (methods “A” and “B”)
21/t ’ [1/μs ]p
2
Yie
ld
0 0.002 0.004 0.006 0.008
E = 150 keVe
E = 300 keVe
E = 450 keVe
E = 600 keVe
E = 750 keVe
I Use edges to determine andverify shape of detectionfunction Φ(pp, 1/tp);
I Use central part of Pt(1/t2p)
(∼ 70%) to extract a.
A. parametrize edges and width of Φ(pp, 1/tp) by fitting; use central partof Φ (∼ 70%) to extract a in a multiparameter fit, and
B. specify accessible parameters of Φ by direct measurement; ⇒ treat a,µ = 1/t2p(pp), and Ndecays as free parameters in a two-step fit,
I as well as a HYBRID OF THE TWO METHODS.
D. Pocanic (UVa) The Nab experiment: Principles of measurement 10 Oct ’14/DNP2013 9 / 14
Projected statistical uncertainties for a and b
Statistical uncertainties for a
Ee,min 0 100 keV 100 keV 300 keV 100 keVtp,max – – 40µs 40µs 30µs
σa 2.4/√Nu 2.5/
√Nu 2.5/
√Nu 2.6/
√Nu 2.8/
√Nu
σa† 2.5/
√Nu 2.6/
√Nu 2.7/
√Nu 2.7/
√Nu 3.1/
√Nu
σa§ 4.1/
√Nu 4.1/
√Nu 4.1/
√Nu 4.1/
√Nu 4.4/
√Nu
† with Ecalib and LTOF variable; § using inner 70% of p2p data.
Statistical uncertainties for b
Ee,min 0 100 keV 200 keV 300 keV
σb 7.5/√N 10.1/
√N 15.6/
√N 26.3/
√N
σb†† 7.7/
√N 10.3/
√N 16.3/
√N 27.7/
√N
†† with Ecalib variable.
D. Pocanic (UVa) The Nab experiment: Uncertainties 10 Oct ’14/DNP2013 10 / 14
Projected statistical uncertainties for a and b
Statistical uncertainties for a
Ee,min 0 100 keV 100 keV 300 keV 100 keVtp,max – – 40µs 40µs 30µs
σa 2.4/√Nu 2.5/
√Nu 2.5/
√Nu 2.6/
√Nu 2.8/
√Nu
σa† 2.5/
√Nu 2.6/
√Nu 2.7/
√Nu 2.7/
√Nu 3.1/
√Nu
σa§ 4.1/
√Nu 4.1/
√Nu 4.1/
√Nu 4.1/
√Nu 4.4/
√Nu
† with Ecalib and LTOF variable; § using inner 70% of p2p data.
Statistical uncertainties for b
Ee,min 0 100 keV 200 keV 300 keV
σb 7.5/√N 10.1/
√N 15.6/
√N 26.3/
√N
σb†† 7.7/
√N 10.3/
√N 16.3/
√N 27.7/
√N
†† with Ecalib variable.
D. Pocanic (UVa) The Nab experiment: Uncertainties 10 Oct ’14/DNP2013 10 / 14
Nab systematic uncertainties: Method B
Experimental parameter (∆a/a)SYST
Magnetic field: curvature at pinch 5× 10−4
ratio rB = BTOF/B0 2.5× 10−4
ratio rB,DV = BDV/B0 3× 10−4
LTOF, length of TOF region (*)U inhomogeneity: in decay / filter region 5× 10−4
in TOF region 1× 10−4
Neutron beam: position 4× 10−5
width 2.5× 10−4
Doppler effect smallunwanted beam polarization small
Adiabaticity of proton motion 1× 10−4
Detector effects: Ee calibration (*)Ee resolution 5× 10−4
Proton trigger efficiency 2.5× 10−4
Accidental coinc’s (will subtract out of time coinc) smallResidual gas ongoing parametric studies smallBackground ongoing parametric studies small
Overall sum 1× 10−3
(*) Free fit parameter
D. Pocanic (UVa) The Nab experiment: Uncertainties 10 Oct ’14/DNP2013 11 / 14
Nab systematic uncertainties: Method B
Experimental parameter (∆a/a)SYST
Magnetic field: curvature at pinch 5× 10−4
ratio rB = BTOF/B0 2.5× 10−4
ratio rB,DV = BDV/B0 3× 10−4
LTOF, length of TOF region (*)U inhomogeneity: in decay / filter region 5× 10−4
in TOF region 1× 10−4
Neutron beam: position 4× 10−5
width 2.5× 10−4
Doppler effect smallunwanted beam polarization small
Adiabaticity of proton motion 1× 10−4
Detector effects: Ee calibration (*)Ee resolution 5× 10−4
Proton trigger efficiency 2.5× 10−4
Accidental coinc’s (will subtract out of time coinc) smallResidual gas ongoing parametric studies smallBackground ongoing parametric studies small
Overall sum 1× 10−3
(*) Free fit parameter
D. Pocanic (UVa) The Nab experiment: Uncertainties 10 Oct ’14/DNP2013 11 / 14
Nab systematic uncertainties: Method B
Experimental parameter (∆a/a)SYST
Magnetic field: curvature at pinch 5× 10−4
ratio rB = BTOF/B0 2.5× 10−4
ratio rB,DV = BDV/B0 3× 10−4
LTOF, length of TOF region (*)U inhomogeneity: in decay / filter region 5× 10−4
in TOF region 1× 10−4
Neutron beam: position 4× 10−5
width 2.5× 10−4
Doppler effect smallunwanted beam polarization small
Adiabaticity of proton motion 1× 10−4
Detector effects: Ee calibration (*)Ee resolution 5× 10−4
Proton trigger efficiency 2.5× 10−4
Accidental coinc’s (will subtract out of time coinc) smallResidual gas ongoing parametric studies smallBackground ongoing parametric studies small
Overall sum 1× 10−3
(*) Free fit parameter
D. Pocanic (UVa) The Nab experiment: Uncertainties 10 Oct ’14/DNP2013 11 / 14
Nab apparatus in FnPB/SNS Apparatus extends:
• ∼6 m above beam height,
• ∼1.5 m below beam height.
Fully funded (NSF-MRI, plus DOE constr. + operating funds);Project so far on track to be ready for beam in early 2016.
D. Pocanic (UVa) The Nab experiment: Apparatus drawings 10 Oct ’14/DNP2013 12 / 14
Status: some drawings of the Nab apparatus
Parts List
DESCRIPTIONQTYITEM
Axial tie rod fixing41
16.5 inch US CF flange22
Axial tie rod fixing23
Sumitomo SRDK -415D 1.5W cryocooler44
Radial tie rod fixing45
Instrumentation flange26
CF 160 flange47
Magnet terminals 108
NW50KF evacuation valves29
Rotation plate210
Lifting eye211
657
Plain washers - Normal series - Product grade A12059
Hexagon Socket Head Cap Screw12060
261
Plain washers - Normal series - Product grade A7263
Hexagon head bolt - product grades A and B7264
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B B
C C
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CRYOGENIC LTD
QUANTITY
CUSTOM FINISHMATERIAL SPECIFICATION
DRAWN BY: REVIEWED BY:
JOB NUMBERTOLERANCE(UNLESS STATED) `0.1
DIMENSION
STD.PART No.
THIS DRAWING BELONGS TO CRYOGENIC LTD AND IS ISSUED ON THE CONDITION THAT IT IS NOT COPIED, REPRINTED OR DISCLOSED EITHER IN WHOLE OR IN PART TO A THIRD PARTY WITHOUT THE PRIOR CONSENT OF:CRYOGENIC LTD, ACTON PARK IND. ESTATE.THE VALE, LONDON W3 7QE
MM
THIS DRAFT:
THIRD ANGLE PROJECTION
DWG No.
OFSHEETFIRST DRAFT:
External View
GA03
3658
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11:51:06
3658 -
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16.50 7.93 5.38 11.50 5.63
SECTION A-ASCALE 1 : 4
D
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AA
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C
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12345678
8 7 6 5 4 3 2 1
WEIGHT:
Detector Assembly_nab
VARIED
RAMSEY 8/6/2014
COMMENTS:
SHEET 1 OF 3
Q.A.
MFG APPR.
ENG APPR.
CHECKED
DRAWN
DATENAMEDIMENSIONS ARE IN INCHESTOLERANCES UNLESS SPECIFIED:FRACTIONALANGULAR: MACH BEND TWO PLACE DECIMAL 0.01THREE PLACE DECIMAL 0.003
FINISH
MATERIAL
REV.
BDWG. NO.SIZE
SCALE:1:8
P-25SUBATOMIC PHYSICS
LOS ALAMOS NATIONAL LABORATORYLOS ALAMOS, NM, 87545 126Y-1766781 B1QUANTITY REQUIRED
1
PRELIMINARYNOT FOR
PRODUCTIOND. Pocanic (UVa) The Nab experiment: Apparatus drawings 10 Oct ’14/DNP2013 13 / 14
Summary
I Nab is part of a broad experimental effort, to exploit the unparalleledtheoretical precision in electroweak processes in general. The programof precision studies is timely, complementary, and valuable for properinterpretation of collider data.
I Nab is expected to resolve the longstanding consistency problem withλ = GA/GV , and provide new constraints on non-SM processes; ABbawill add independent constraints.
I Nab is fully funded and all parts of the project are proceeding apace;it is expected on the floor at SNS in 2016.
I Significant synergies and joint interest exist between the LANL UCNxand Nab/ABba programs.
Home page: http://nab.phys.virginia.edu
D. Pocanic (UVa) The Nab experiment: Summary 10 Oct ’14/DNP2013 14 / 14
Summary
I Nab is part of a broad experimental effort, to exploit the unparalleledtheoretical precision in electroweak processes in general. The programof precision studies is timely, complementary, and valuable for properinterpretation of collider data.
I Nab is expected to resolve the longstanding consistency problem withλ = GA/GV , and provide new constraints on non-SM processes; ABbawill add independent constraints.
I Nab is fully funded and all parts of the project are proceeding apace;it is expected on the floor at SNS in 2016.
I Significant synergies and joint interest exist between the LANL UCNxand Nab/ABba programs.
Home page: http://nab.phys.virginia.edu
D. Pocanic (UVa) The Nab experiment: Summary 10 Oct ’14/DNP2013 14 / 14
Summary
I Nab is part of a broad experimental effort, to exploit the unparalleledtheoretical precision in electroweak processes in general. The programof precision studies is timely, complementary, and valuable for properinterpretation of collider data.
I Nab is expected to resolve the longstanding consistency problem withλ = GA/GV , and provide new constraints on non-SM processes; ABbawill add independent constraints.
I Nab is fully funded and all parts of the project are proceeding apace;it is expected on the floor at SNS in 2016.
I Significant synergies and joint interest exist between the LANL UCNxand Nab/ABba programs.
Home page: http://nab.phys.virginia.edu
D. Pocanic (UVa) The Nab experiment: Summary 10 Oct ’14/DNP2013 14 / 14
Summary
I Nab is part of a broad experimental effort, to exploit the unparalleledtheoretical precision in electroweak processes in general. The programof precision studies is timely, complementary, and valuable for properinterpretation of collider data.
I Nab is expected to resolve the longstanding consistency problem withλ = GA/GV , and provide new constraints on non-SM processes; ABbawill add independent constraints.
I Nab is fully funded and all parts of the project are proceeding apace;it is expected on the floor at SNS in 2016.
I Significant synergies and joint interest exist between the LANL UCNxand Nab/ABba programs.
Home page: http://nab.phys.virginia.edu
D. Pocanic (UVa) The Nab experiment: Summary 10 Oct ’14/DNP2013 14 / 14
Summary
I Nab is part of a broad experimental effort, to exploit the unparalleledtheoretical precision in electroweak processes in general. The programof precision studies is timely, complementary, and valuable for properinterpretation of collider data.
I Nab is expected to resolve the longstanding consistency problem withλ = GA/GV , and provide new constraints on non-SM processes; ABbawill add independent constraints.
I Nab is fully funded and all parts of the project are proceeding apace;it is expected on the floor at SNS in 2016.
I Significant synergies and joint interest exist between the LANL UCNxand Nab/ABba programs.
Home page: http://nab.phys.virginia.edu
D. Pocanic (UVa) The Nab experiment: Summary 10 Oct ’14/DNP2013 14 / 14
Current Nab collaboration
R. Alarcona, L.P. Alonzi2§, S. Baeßlerb∗, S. Balascutaa, A. Barkana, L. BarronPalosc , N. Birgei , J.D. Bowmand†, L. Broussardm, J. Byrnee , J.R. Calarcof ,
T. Chuppg , V. Cianciolod , C. Crawfordh, N. Fomini , E. Frlezb, M.T. Gerickej ,F. Gluckk , G.L. Greened,i , R.K. Grzywaczi , V. Gudkovl , D. Harrisonj ,
F.W. Hersmanf , T. Itom, H. Lib, M.F. Makelam, J. Martino , P.L. McGaugheym,S.A. Pagej , S.I. Penttilad‡, D. Pocanicb†, K.P. Rykaczewskid , A. Salas-Baccib,
E.M. Scotti , A. Sprowh, J. Thomisond , Z. Tompkinsb§, W.S. Wilburnm,A.R. Youngp, B. Zeckp.
aArizona State University bUniversity of VirginiacUNAM, Mexico dOak Ridge National LabeUniversity of Sussex f Univ. of New HampshiregUniversity of Michigan hUniversity of KentuckyiUniversity of Tennessee jUniversity of ManitobakUni. Karlsruhe/RMKI Budapest lUniversity of South CarolinamLos Alamos National Lab oUniversity of WinnipegpNorth Carlolina State Univ. †Co-spokesmen∗Project Manager ‡On-site Manager
Home page: http://nab.phys.virginia.edu/
D. Pocanic (UVa) The Nab experiment: Summary 10 Oct ’14/DNP2013 15 / 14
Current status of Vud and λ, from n decay. . . remains an unresolved mess:
λ = gA/gV
V
ud
PIBETA [Pocanic04]
ft(0+→0
+) [Hardy09]
CKM unitarity
[PDG 2012]
τ n [P
DG
201
2]
PKO1 DD-ME2ft(0
+→0
+) [Liang09]
λ [
PD
G 2
01
2]
λ [
UC
NA
20
10]
λ [
PE
RK
EO
II
20
12]
0.96
0.965
0.97
0.975
0.98
-1.29 -1.28 -1.27 -1.26
τ−1n ∝ |Vud |2|gV |2(1 + 3|λ|2)
-1.28 -1.26 -1.24
Stratowa (1997)
PERKEO I (1986)
Liaud (1997)
PERKEO II (1997) ( )
( ) PERKEO II (2002)
PERKEO II (2013)
UCNA (2010) ( )
UCNA (2013)
Mostovoi (2001)
Yerozolimskii (1997)
Byrne (2002)
Average:-1.2724(21)
Δ λ/ = 0.03% (Nab goal)
λ
Very low CL!
∆λ
λ' 0.27
∆a
a' 0.24
∆A
Aλ sensitivity to a, A is similar.
I Nab+abBA ⇒ several independent ∼ 0.03% determinations of λ,I Combined with b ⇒ new limits on non-SM terms, esp. Tensor.
D. Pocanic (UVa) The Nab experiment: Summary 10 Oct ’14/DNP2013 16 / 14
Limits on T , S couplings from beta decay
-0.0010 -0.0005 0.0000 0.0005 0.0010-0.02
-0.01
0.00
0.01
0.02
¶T
¶S
b¤ < 10-3 bΝ - b¤ < 10-3
b0 + = -H2.2 ± 4.3L 10-3
-0.0010 -0.0005 0.0000 0.0005 0.0010-0.02
-0.01
0.00
0.01
0.02
¶T¶
S
b¤ < 10-3 bΝ¤ < 10-3
b0 + = -H2.2 ± 4.3L 10-3
Measurement of b with δb < 10−3 ⇒ > 4-fold improvement on the currentlimit for εT from π+ → e+νγ decay.From T. Bhattacharya, V. Cirigliano, S.D. Cohen, A. Filipuzzi, M. Gonzalez-Alonso,
M.L. Graesser, R. Gupta, H-W. Lin, Phys. Rev. D 85 (2012) 054512.
D. Pocanic (UVa) The Nab experiment: Summary 10 Oct ’14/DNP2013 17 / 14