measurement of parity-violation in cold neutron capture
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Measurement of Parity-Violation in Cold Neutron Capture
Mikayel Dabaghyan for the NPDGamma Collaboration
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Outline
1. Hadronic Weak Interaction
What…
Why…
How…
2. Experiment
Hardware and measurements
3. Analysis and Results
Asymmetry, Errors
4. Summary and Outlook
Present and Future
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Why…
Z0 = 91.2 GeV W± = 80.4 GeV
range - ≤ 2×103 fm . π, ρ, ω ≤ 300 MeV.
range - ≤ 1 fm .
Bosons are too heavyNN
N N
Z0, W± ?ρ, ω, π±
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Explore weak interaction at low energies.
The ΔI = ½ rule: Γ(Ks0 → π0π0) » Γ(K+ → π+π0).
Probe strong interaction at low energies.
Study the weak interaction between hadrons
Weak Interaction
μ → e- + υμ + υe
n → p + e- + υe
n + p → n + p
Weak processesμ-
νμW-
e- νe
d
uW-
e- νe
dun
dup
u
dW+
udp
udn duu
dud n
p
π+
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Weak Interaction
ΔS = 0 : strong
Use Parity!
Weak vs. Strong NN
N N
π±, ρ, ω PCPV𝑺𝑻𝑹𝑶𝑵𝑮𝒘𝒆𝒂𝒌 ~ 𝟏𝟎𝟕
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Parity Violation
Two nucleon system: n + p → d + γ
ΔS = 0, ΔI = 1 channel
Study the weak interaction between hadrons
real worldmirror world
P(x) = - x P(y) = - y P(z) = - z
Parity
P(sn) = sn P(kγ) = - kγ
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Why PV in n+p → d+γ ?
Parity Violation|𝜓𝐽=0𝑖𝑛𝑖𝑡𝑖𝑎𝑙 =ۄ���������� | 𝑆01 +ۄ����������1, 𝛼0| 𝑃03 𝜓𝐽=1𝑖𝑛𝑖𝑡𝑖𝑎𝑙| ۄ����������1, =ۄ���������� | 𝑆13 +ۄ����������0, 𝛼0| 𝑃11 +ۄ����������0, 𝛼1| 𝑃13 𝜓𝐽=1𝑓𝑖𝑛𝑎𝑙| ۄ����������1, | = ۄ���������� 𝑆13 +ۄ����������0, 𝛼0| 𝑃11 +ۄ����������0, 𝛼1| 𝑃13 ۄ����������1,
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
3S1, I=0 3P1, I=1 1P1, I=0
3S1, I=0 3P1, I=1 1P1, I=0 1S0, I=1 3P0, I=1
M1
E1E1
M1
E1
E1E1
E1E1
Hindered transition
n + p excited and ground states
How…
n p d
ϑ
𝑑𝜎𝑑Ω= 1+ 𝐴𝛾 ∙𝑐𝑜𝑠ሺ𝜗ሻ
𝐴𝛾 = 2ξ2∙ ۄ����������𝐸1ۃ������� ۄ����������𝑀1ۃ�������
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
-2 -1 0 1 2 3 4
Goal:DDH: 𝑯𝝅𝟏,𝑯𝝆𝟎,𝑯𝝆𝟏,𝑯𝝆𝟏′ ,𝑯𝝆𝟐,𝑯𝝎𝟎,𝑯𝝎𝟏 𝑯𝝅𝟏 𝑨𝜸 = −𝟎.𝟎𝟒𝟓∙
DDH: Desplanques, Donoghue, Holstein, Annals of Physics 124, 1980, 449.M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
DDH TheoreticalEstimate
n+p→d+γCavaignac et al.Phys.Lett.B., 67148, 197718FEvans et al.; Bini et al.Phys.Rev.Lett. 55133CsWood et al.Science 275, 1753, 1997 Flambaum and MurrayPhys. Rev. C 56, 1641, 1997
Compound NucleiBowman et al. LANL 2002
-2 -1 0 1 2 3 4
Hπ1 so far…
Hπ1(×10-6)
0.5× 10−8 𝑜𝑟𝑑𝑒𝑟 𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑚𝑒𝑛𝑡
Hπ1(×10-6)
Experiment - Overview
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Flight Path
Neutron Guide
Shielding
Holding Field
Beam Monitors
Detector Array
RF Spin Flipper
Polarizer
Analyzer
Hydrogen Target
Compound Targets
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
800 MeV Protons from ½ mile linac (~100μA) Protons hit the W spallation target to produce neutrons Neutrons are moderated by LH2 to ~100meV 20Hz pulses – 50ms frames – time of flight informationNeutrons are delivered by an ~20m “supermirror” guide
Flight – Path
Experiment – Flight Path
Apparatus
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
𝜆= ℎ𝑡𝑚𝐿
Apparatus – Flight Path Length
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Bragg Transmission𝑛𝜆= 2𝑑∙𝑠𝑖𝑛𝜃
Flight Path Length𝐿0 = 21.10± 0.03 𝑚 𝐿1 = 21.11± 0.03 𝑚 𝐿2 = 21.49± 0.03 𝑚 𝐿3 = 22.81± 0.04 𝑚
L1 L2 L3
Tn
3π acceptance
4 rings of 15×15×15 cm3 CsI crystals
VPD: insensitive to magnetic field
High event rate: use current mode
Low-noise preamps: < 0.1 mV RMS
Operate at counting statistics
95% γ’s stopped in crystals
Aligned with B0 better than 1o
Measure Neutron Flux
Experiment – γ-ray Detectors
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Experiment – Polarizer
3He cellUnpolarized
Neutrons
Polarized
Neutrons
Helmholtz Coils
Polarized Laser Light
12 cm in diameter, 5 cm thick
4.9 atm·cm
Relaxation time of 500 hrs
Typical polarization ~ 55%
Boo-Boo
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
- 3 barns
- 5333 barns!
Transmission
3He as a Neutron Spin Filter
n 3He
n 3He
𝑻↑↓ = 𝒆− 𝒏𝒍𝝈∙ሺ𝟏∓𝑷𝟑ሻ 𝑻𝒏 = 𝒄𝒐𝒔𝒉(𝒏𝝈𝒍𝑷𝟑) 𝑷𝒏 = ඨ𝟏 −൬
𝑻𝟎𝑻𝒏൰𝟐
Experiment – Polarizer
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
T n/T
o
TOF [ms]
Experiment – Polarizer Performance
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Experiment – Analyzer
Measure Neutron Beam polarization
Measure RFSF efficiency
Optimize RFSF parameters
Function
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Experiment – Analyzer
PEEK/glass components
Uniform Temperature (165o C)
Non-metallic parts
Polarized light from 2 sides
30 W Laser
Oven
Laser Optics
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Transport Suitcase 2.5 cm in diameter
6.2 atm·cm
Relaxation time of 130 hrs
Typical polarization ~ 47%
Experiment – Analyzer
Helmholtz coils create 12 Gauss fieldRunning on batteriesLoss of polarization: ~10%/hr
TS - 12
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Experiment – RF Neutron Spin Flipper
Limit systematic effects
2 mm Al housing enough to isolate RF field
20 Hz pulse pattern: ↑↓↓↑↓↑↑↓
Resonant Radio Frequency Spin Rotator
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Optimization is performed using the Analyzer
Normalized population difference between ↑↓
RFSF Efficiency Optimization
RFSF – Parameter Optimization
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
OffNo=No++No- N1=N1++N1- N1=N1++N1- N2=N2++N2- Pol Anl
RFSFOn
RFSF
OffPol AnlNo=No++No- N1=N1++N1- N1=N1++N1- N2=N2++N2-
RFSF
OffPol AnlNo=No++No- N1=N1++N1- N1=N1++N1- N2=N2++N2-
RFSF
OnPol AnlNo=No++No- N1=N1++N1- N’1=N’
1++N’1- N’
2=N’2++N’
2-
NMR Flip – 100%
Compare NMR and RFSF flips
Scan off-axis by moving
collimator+analyzer+M3
εon axis = 99.69 ± 0.12
ε1.3” beam left = 94.06 ± 0.11
ε1.3” beam right = 93.83 ± 0.11
RFSF Efficiency Measurement
RFSF – Efficiency
൫𝑇𝑜𝑓𝑓↑↑ − 𝑇𝑜𝑛↑↑൯൫𝑇𝑜𝑓𝑓↑↑ − 𝑇𝑜𝑓𝑓↓↑ ൯ൗ� = 1+ 𝜀2
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
PV in Compound Nuclei – Not so simple, so why bother?
Some materials are in the beamline – Al, Cu, In …
Reason 1.
Study PV in nuclear targets – has not been done for this A-range
Reason 2.
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Large capture cross-section
Small scattering cross-section
Small incoherent cross-section
Close level spacing
Selection Criteria
Compound Solid Targets
Al
Mn
Co
Cu
Ti
Cl
In
V
Sc
List of Solid Targets
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Compound Solid Targets
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Targets – LH2
LH2 Target Aluminum cylinder
Diameter of 26.62 cm
16L of LH2
kept at ~ 17 K
σcap « σscatt
Para-H2: capture and coherent scatter
Ortho-H2: coherent and incoherent scatter
𝜎𝑖𝑛𝑐𝑜ℎ𝑜𝑟𝑡ℎ𝑜 = 20.052± 0.014 𝑏 𝜎𝑐𝑜ℎ𝑜𝑟𝑡ℎ𝑜 = 0.439± 0.003 𝑏
Cross sections
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Cro
ss S
ectio
n
meV
σsortho
σspara
σa
Ortho-Para conversion - 1030 hrs
Two FeO2 OPCs – 112 hrs
OPC #1
OPC #2
LH2 target
Neutron Beam
Targets – LH2
𝐾𝑂𝑃𝐶 = 6.09 %ℎ𝑟
𝐾𝑛𝑎𝑡𝑢𝑟𝑎𝑙 = 1.94 %ℎ𝑟
Ortho-to-Para Conversion
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Targets – LH2
M2 M3
LH2 Full measurement:
Empty measurement:
Resulting in
Transmission Through LH2
𝑆𝑀3𝐸𝑚𝑝𝑡𝑦𝑆𝑀2𝐸𝑚𝑝𝑡𝑦 = 𝐾3𝐾2 ∙𝑇𝑜𝑡ℎ𝑒𝑟
𝑆𝑀3𝐹𝑢𝑙𝑙𝑆𝑀2𝐹𝑢𝑙𝑙 = 𝐾3𝐾2 ∙𝑇𝑜𝑡ℎ𝑒𝑟 ∙𝑇𝐻2
𝑇𝐻2 = 𝑆𝑀3𝐹𝑢𝑙𝑙 𝑆𝑀2𝐹𝑢𝑙𝑙Τ𝑆𝑀3𝐸𝑚𝑝𝑡𝑦 𝑆𝑀2𝐸𝑚𝑝𝑡𝑦ൗ�
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Para: 99.98%
Data Analysis
n p d
ϑ
𝑑𝜎𝑑Ω= 1+ 𝐴𝛾 ∙𝑐𝑜𝑠ሺ𝜗ሻ
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Raw Asymmetry
Physics Asymmetryθ
Data Analysis
𝐴𝛾𝑟𝑎𝑤 = 𝑈− 𝐷𝑈+ 𝐷 U
D
𝐴𝛾𝑟𝑎𝑤 = 𝐴𝛾𝑈𝐷𝐺𝑖𝑈𝐷 + 𝐴𝛾𝐿𝑅𝐺𝑖𝐿𝑅
𝐴𝛾 = 𝐴𝛾𝑟𝑎𝑤𝑃ሺ𝑡ሻ∙𝑇ሺ𝑡ሻ∙𝑆ሺ𝑡ሻ
𝑨𝜸𝒕𝒐𝒕𝒂𝒍 = σ 𝑨𝜸𝒊𝝈𝒊,𝜸𝟐𝒊σ 𝟏𝝈𝒊,𝜸𝟐𝒊 ± 𝟏
ඨσ 𝟏𝝈𝒊,𝜸𝟐𝒊
Sequence Asymmetry
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Table Motion Measurements
Reconstructed Angles
Detector Geometry
RC
R
XC -R
XC
YC
Crystal
Source
𝑺ሺ𝒙,𝒚ሻ∝ 𝟏𝑹𝟐 ⇒ 𝝏𝑺𝝏𝒚ൗ�𝝏𝑺𝝏𝒙ൗ�= 𝒕𝒂𝒏ሺ𝝑ሻ
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Error from Left-Right Mixing into Up-Down
Ideally cosϑ and sinϑ
Neutron absorption probability
Energy left by a γ in the crystal
Geometry Factors
Detector Geometry
𝑨𝜸′𝒓𝒂𝒘 = 𝒄𝒐𝒔𝝑𝑨𝜸𝑼𝑫+ 𝜹𝝑𝟐 𝑨𝜸𝑳𝑹൨+ 𝒔𝒊𝒏𝝑𝑨𝜸𝑼𝑫+ 𝜹𝝑𝟐 𝑨𝜸𝑳𝑹൨
𝝑′ = 𝒔𝒊𝒏−𝟏ۏ����������ێ�����ێ�����ۍ����������������� 𝑮𝑳𝑹𝒊ට൫𝑮𝑳𝑹𝒊 ൯
𝟐 +൫𝑮𝑳𝑹𝒊 ൯𝟐ے�������������������ۑ��������������ۑ��������������ې�����
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Depolarization in the targets
Neutron Beam Depolarization𝝈𝒕𝒐𝒕 = 𝝈𝒂+𝝈𝒄+ 𝝈𝒊
𝑷𝒂 = 𝝈𝒂𝝈𝒕𝒐𝒕 ,𝑷𝒇𝒍𝒊𝒑 = 𝟏𝟑𝝈𝒊𝝈𝒄+𝝈𝒊
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Backgrounds and false asymmetries
Electronic pick-up
Activation
Scattered neutrons
Frame overlap
γ’s from spallation
Few percent for solids
More for LH2
ABkg = 0
Sources of Backgrounds
𝑨𝒔𝒊𝒈 = 𝑨𝒔𝒊𝒈+𝒃𝒌𝒈൫𝑺𝒔𝒊𝒈 + 𝑺𝒃𝒌𝒈൯𝑺𝒔𝒊𝒈 = 𝑨𝒔𝒊𝒈+𝒃𝒌𝒈ሺ𝟏 + 𝜷ሻ− 𝑨𝒃𝒌𝒈𝜷
𝝈𝑨𝒔𝒊𝒈 = ටሺ𝟏 + 𝜷ሻ𝟐𝝈𝑨𝒔𝒊𝒈+𝒃𝒌𝒈𝟐 + 𝜷𝟐𝝈𝑨𝒃𝒌𝒈𝟐
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Cuts
Neutron beam current
Detector sums/diff’s
Beam fluctuations
Detector saturation
Valid spin sequences
Cuts on the Data
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Systematics
Multiplicative noise
Additive noise
Non-hydrogen target Aγ
Mott – Schwinger LR
Stern – Gerlach steering
Sources
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Huge known UD asymmetry
Calibrate the experiment
Chlorine
𝑨𝜸𝒓𝒂𝒘 = 𝑨𝜸𝑼𝑫𝒄𝒐𝒔ሺ𝝑′ሻ+ 𝑨𝜸𝑳𝑹𝒔𝒊𝒏ሺ𝝑′ሻ Fit to
Asymmetry Results - Chlorine
AγUD = (19.62)×10-6
AγLR = (0.087)×10-6
RIN
G
4RIN
G
3RIN
G
2RIN
G
1
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Aγ = (19.47 ± 2.02)×10-6
-3.0E-05
-2.0E-05
-1.0E-05
0.0E+00
1.0E-05
2.0E-05
3.0E-05
0 2.5 5 7.5 10 12.5 15 17.5 20 22.5
Aγ
raw
θdetector [rad]
Cl Data A=UD*COS(x) + LR*SIN(x)
Para-Hydrogen, Aγ
More statistics
Better knowledge of
background
Hydrogen
Asymmetry Results - Hydrogen
RIN
G
4RIN
G
3RIN
G
2RIN
G
1
Aγ = (0.95 ± 2.01)×10-7
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
AγUD = (1.7)×10-7
AγLR = (1.1)×10-7
-1.5E-06
-1.0E-06
-5.0E-07
0.0E+00
5.0E-07
1.0E-06
1.5E-06
0 2.5 5 7.5 10 12.5 15 17.5 20 22.5
Aγra
w
θdetector [rad]
DATA A=UD*COS(x) + LR*SIN(x)
Results – The other targets
Co 7.7 3.5 0.7 3.6Cu -11.9 5.8 1.1 5.9In 6.8 3 0.6 3.1
Mn -5.3 7.8 0.5 7.8Sc 7 2.8 0.7 2.9Ti -6.5 3 0.6 3.1V 1.7 6.3 0.2 6.3
Targets Aγ(×10-7) σAγ,stat(×10-7) σAγ,syst(×10-7)
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
σAγ,TOT(×10-7)
Summary
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
Aγ = (0.95 ± 2.01)×10-7
Hπ1 = (-2.1 ± 4.5)×10-6
LANL 2006, Production Phase 1
Preliminary
Cavaignac et al.Phys.Lett.B., 67
148, 1977
Aγ = (0.6 ± 1.8)×10-7
Hπ1 = (-1.4 ± 4.0)×10-6
DDH TheoreticalEstimate
n+p→d+γCavaignac et al.Phys.Lett.B., 67148, 1977
18FEvans et al.; Bini et al.Phys.Rev.Lett. 55
133CsWood et al., Science 275, 1753, 1997 Flambaum and Murray, Phys. Rev. C 56, 1641, 1997
Compound NucleiBowman et al. LANL 2002
-4 -2 0 2 4Hπ
1(×10-6)
n + p → d + γLANL 2006, Preliminary
ORNLLANLJLABUniversity of MichiganIndiana UniversityIndiana Univ. CyclotronNISTUniversity of New HampshireUniversity of TennesseeUniv. of California, BerkeleyUniv. of California, DavisUniversity of ManitobaUniversity of ArizonaHamilton CollegeNorth Carolina State Univ.JINR, Dubna, RussiaUniv. of DaytonKEK, Japan
J.D. Bowman, S. Penttila S.Wilburn.T.Ito,A. Klein,V.Yuan,A.Salas-Bacci, S.SantraR.D. Carlini T.E. Chupp, M. SharmaM. Leuschner, J. Mei, H. Nann, W.M. Snow, R.C. GillisB. LosowkiT.R. GentileF.W. Hersman, M. Dabaghyan,H. Zhu,S. Covrig, M.MasonG.L. Greene, R. MahurinS.J. Freedman, B. LaussG.S. MitchellM.T. Gericke, S. Page, D. RamsayL. Barron-Palos, S. BalascutaG.L. JonesP-N. SeoE. SharapovT. SmithT. Ino, Y. Masuda, S. Muto
The NPDγ Collaboration
M. Dabaghyan for the NPDGamma Collaboration The n + p → d + γ Experiment at LANL
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