tensor polarized targets at triumf g. smith, march 2014 1 tensor target polarization at triumf...
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![Page 1: Tensor Polarized Targets at TRIUMF G. Smith, March 2014 1 Tensor Target Polarization at TRIUMF 1929-2014 Erich Vogt TRIUMF director 1981-1994 G. Smith,](https://reader030.vdocument.in/reader030/viewer/2022033107/56649f3b5503460f94c5a71d/html5/thumbnails/1.jpg)
Tensor Polarized Targets at TRIUMFG. Smith, March 2014 1
• The Program: First msrmnts of tensor observables in scattering expt’s (mid-80’s)– (iT11), T20, T21, T22
• Msrmnts mostly in elastic channel• Some also in absorption & breakup
– Direct msrmnt of tgt tensor polarization
• Independent of usual NMR techniques• RF burning results also studied
– Brief description of • tgts used• expt’l techniques• physics
– Description of analysis techniques
Tensor Target Polarization at TRIUMF
1929-2014
Erich VogtTRIUMF director
1981-1994
G. Smith, JLab
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 2
• Use Madison convention– Proceedings of the Third International Symposium on Polarization Phenomena in Nuclear
Reactions, Madison, 1970, edited by H. H. Barschall and W. Haeberli (University of Wisconsin, Madison, 1971).
– P. Schwandt and W. Haeberli, Nucl. Phys. A110, 585 (1968).
• Target vector (pz) & tensor (pzz) polarization
• Msrd tensor polarization (t20) of recoil d– : unpolarized tgt
• 3He(,p)4He polarimeter to analyze recoil d
• Vector (iT11) & tensor (T20, T21, T22) analyzing powers. Composite observables & – elastic: tensor polarized target
Nomenclature
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 3
Brillouin formula:
With I=1, x=(μH)/(2kT) Likewise, , peak asym
And νD=d NMR ν (16.6 MHz) & Ts=d spin temp
Some Basic Formulas
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 4
• x = (μH)/(2kT)– µ = 2.703x10-14 MeV/T– k = 8.617×10−11
MeV/K
– 3He fridge: pz~0.25
– 3He/4He fridge: pz~0.5
Plots
0
0.05
0.1
0.15
0.2
0.25
0.3
0 0.1 0.2 0.3 0.4 0.5 0.6
Tens
or p
olar
izati
on p
zz
Vector Polarization pz
0
0.005
0.01
0.015
0.02
0.025
0.03
0 100 200 300 400 500
Deu
tero
n po
lariz
ation
pz
Temp (mK)
Natural Polarization (T)
Dilutionrefrigerator 3He
refrigerator
Not much to work with!
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 5
SIN
LAMPF
SIN
SIN
LAMPF
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 6
• Perform 1st expt. ever using a tensor polarized target!
• , with longitudinal – We thought we were pioneering this back in 1984
• Knew about some CERN tech notes on pol tgts– deBoer etal PL46A, 143 (1974), Ninnikoski, Scheffler,
Guckelsberger & Udo NIM137, 415 (1976), Hamada etal NIM189, 561 (1981)
– No double scattering/recoil polarimeter– Fewer systematic errors: msr xsec ratios– Develop a large dΩ detection system with lots of θ
multiplicity– Crucial to insure to suppress other Tij
• Used a split counter with field on/off to do this, lasers & mirrors
– Be damn sure you can msr pzz
How to resolve this?
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 7
Where the are the Wigner d functions, and
using either calculated values of T21 & T22 ,or
limiting values .Coordinate system rotation needed because
T20 z along incident beam, but t20 z along d momentum.
This rotation mixes in small components from T21 & T22.
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T20 First Results
SIN t20
LAMPF t20
TRIUMF t20
TRIUMF T20
Full calc
No P11 abs
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 9
Conditions: • Dilution fridge ~ 120 mK – s.b. 50 mK!
• Longitudinal 2.5 T sc split pair– ΔB/B ~ 10-4, persistent mode
• νμwave 70.820 GHz (3h @ 1 mW)– νNMR ~ 16.660 ± 0.256 MHz
• 1 mm φ deuterated butanol beads– 95% deuterated n-butyl alchohol– 5% D2O doped with EHBA-(CrV)– Teflon cell 16x16x5 mm3
• Pz=0.333 ± 0.015 Pzz=0.085 ± 0.008– 3 techniques used to msr pzz:
• pz = P(N) A(D)/A(N)
• DIRECT MSR OF PZZ
𝒑 𝒛𝒛=𝟐−√𝟒−𝟑𝒑𝒛𝟐
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 10
• Area & R techniques rely on assumptions:– D quadrupole moment contribution
negligible • 20 kHz vs 16 MHz @ 2.5 T
– Boltzmann dist. (equal spin temps)• Kiss that goodbye with RF burning
– pzz deduced from msrd pz
– pzz is bloody small…– NMR system linear over a wide range
• In gain (~3 orders of magnitude)• In frequency too (16.6 ± 0.3 MHz @ 2.5 T)
pzz is abstract. Can we trust it?
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 11
• BENCHMARK usual NMR methods to msr pzz by direct msrmnt:
– T20 at 90º(cm) in pp “known” virtually model independently, and is large, maximal in fact: • , where σ = Yield/(Nbeamε)
• Get T20 2 ways:– Msrd Ayy in pp πd at 90º:
• Ayy=-0.86±0.04 at Tp=447 MeV (NPA415, 391 (1984))
• Then T20 = -1.27 ± 0.05
– PWA & 3-body Fadeev calculations• If a2 (feeds the 1D2 pp wave) dominates (as expected on
resonance):
Novel DIRECT msr of pzz
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 12
Msrd Ayy in ppπd
Fadeev
Our PSA
beam
C4D9OD
C4H9OH(bkg)
foreground minus bkg
BKG: QF abs on 12C
Since no abs on H, this is a perfect bkg tgt!
Flinders PSA
pzz Experiment
Took T20= -1.28 ± 0.03after accounting for
±2.5º angular acceptance
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 13
• Analyzed πd 2p data using:– TOF: pzz = 0.098 ± 0.024
– Coplanarity: pzz = 0.100 ± 0.022
• Using NMR techniques:– NMR Areas: pzz = 0.083 ± 0.008
– NMR peak ratios: pzz = 0.095 ± 0.008• RF pedestal burning msrd in frozen spin mode
(no μw) over 18h after burning. NMR pzz
unknown:– TOF: pzz = 0.10 ± 0.017
– Coplanarity: pzz = 0.11 ± 0.018– Consistent with unburned
• Either no enhancement, or relaxation times too short
Benchmarking pzz Results
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0 1 2 3 4 5 6 7
pzz
?
?
?
ok
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 14
• Saw no effect– Within our uncertainties– Also none from holding field– But pzz was very small
– Hazy on what NMR predicted burned pzz was• I think it was Δpzz ~ 0.05 (see TRI-PP-86-027 by Delheij, Healey &
Wait)
– Really no effect? • Msrd burned/unburned = 1.08 ± 0.30• A larger ratio if comparing burned to NMR… grasping at straws though
– After burning, msrd average polarization over an 18h period• Did not investigate shorter time periods
• Was frozen spin the problem?– May have had better rslts with MUCH higher B (longer relaxation
times)
• Need to know pzz during the entire physics msrmnt– Problematic if burned pzz(time) is hard to msr
More on Burning
00.020.040.060.08
0.10.120.140.160.18
0 2 4 6 8 10
pzz
NMR
πd2punburned
Avg of πd2pburned
2.5 Tburned
1.25 Tburned
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 15
TRIUMFTgt Grp
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 16
Next: T21
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 17
• With Euler angles– = polar angle between incident beam (z-axis) and – = angle between y-axis () and projection of on x-y plane
• To emphasize T21 take = 54.7° to kill T20 term and = 90° to kill iT11 term
– But had to pick =45° due to magnet geometry
How to get at T21?
𝜶
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 18
– take =0° to eliminate all other Tij – undefined
– take =54.7° to kill T20, =90° to kill iT11. Some T22.
– We had to take =45° which mixes in some T20 (& T22)
– take =90° to eliminate T21
– Take =0° to maximize iT11 & T22 terms. Some T22.
𝜶
𝜷Choice of Euler Angles Determines the Observables
Can separate Tij after measuring , composite obs. , &
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 19
• With = 45° and = 90° :
Initial Results
Small by Small at back angles
C4D9OD C4H9OH
pz=0.47
TE
pzz=0.17
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 20
More on T20 & T21
pzz 0.10 up to 0.17
pz=0.47
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 21
Better without the P11 !
Some Results
Full 3 body(Flinders)
Same, but w/o P11
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 22
The P11 Phase Shift
• NN – πNN system: hard to couple to 2 body cuz π can absorb on one N and be emitted by the other. – Soln: treat abs. via the P11 πN
interaction
• 3-body calculations sensitive to cancellation of the pole (true π absorption) & non-pole (multiple scattering w/o absorption) in the P11 πN phase shift.– Problem: cacl’s w/o the P11 generally
compare better to data!– Soln (Jennings, PLB205, 187 (1988):
Pole term Pauli blocked. Missing diagrams (different time ordering) cancel ones responsible for the Pauli blocking & improves agreement!
cancels 1b & 1c missing
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 23
• Propandiol: C3D6(OD)2 & C3D6(OH)2 92% deuterated, doped with CrV
– 1 mm beads in a 0.1 mm thick 5x18x18 mm3 brass cell
– 4 mW cooling power – 50 mK dilution fridge
– Up to pz=-0.48 (pzz=0.18) after 12 h
Back to SIN/PSI
150h @ 0.83T
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 24
• Till now, only msrd (pol)/σ(unpol)– What about AND ?– Use both reduce systematic errors
• Rewrite general eq. as σ(pz) = A + Bpz + Cpzz
– Where A = σ0, B = σ0aViT11, & C = σ0aTT
• And for T=T20,
for T=21, & aV~0– – If B≠0
• pz is wrong, or tgt/B misaligned
Extraction Method 2: Fitting
T20
21
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 25
o Take data in sequence:o ...,,
o Adding & subtracting:
o Likewise for
o Construct matrices of for each pair (ie like , ). o Ex: 5 pairs of, , 5 of,
o 5 rows & 5 columnso Diag elements are time ordered pairs
o Weighted avg of these is the resulto Row & column avgs consistencyo Eliminates electronic drifts
Extraction Method 3: Matrices
Diagonalmatrix
elements &result =
weighted avg
Columnaverages
Rowaverages
294 MeV, θπ=151°
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 26
Completing the suite:
– With normal to scattering plane (vertical)
with α=90º & β=0º
So you get iT11 from the difference of σ±, & τ22 simultaneously from the sum
-48.2%
+41.7%
134º
76º
400h @ 2.5T
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•
&
134º
76º
𝝉𝟐𝟐
𝑖𝑇 11
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Tensor Polarized Targets at TRIUMFG. Smith, March 2014 28
• Tensor polarized targets have been used successfully to measure iT11, T20, and in π scattering– With pz=0.48, get pzz=0.18
• RF burning was a bust (for us) within our (large) uncertainties– pzz direct msrmnt to confirm NMR techniques
– Target alignment () with crucial to select Tij
– Various methods to extract Tij using • But can make do just fine with just σ(pol) & σ(unpol)
– Caveats: Beam heating negligible with pions
• My b1 opinion: dangerous to bank on rf burning– rf burning probably still worth investigating further/better
• But essential to find a way to benchmark it outside NMR– Backup plan with pzz ~0.2 (you know you can do this)
Summary