Parity‐violaon Studies at JLab‐12GeV - University of...
Transcript of Parity‐violaon Studies at JLab‐12GeV - University of...
Parity‐viola+on Studies at JLab‐12GeV
Kent Paschke
University of Virginia
Many figures from K.Kumar, P.Souder, E. Chudakov, and others
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Parity‐Viola+on in Electron ScaHering
•Incident beam is longitudinally polarized•Change sign of longitudinal polariza+on•Measure frac+onal rate difference
! =!!M! +MZ
!!2ScaHering cross‐sec+on
γ Z0
γ 2 !!!MZ
!!!!M!
!!
! 10!4 Q2!GeV2
"APV !
GF Q2
4!"
!ge
AgTV + #ge
V gTA
"
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Precision Electroweak Physics
• pioneering• recent• next generation• future
The 12 GeV upgrade will open new opportuni+es for ‐ studies of nucleon structure in the valance regime‐ precision electroweak physics These opportuni+es will come with
significant new technological challenges
Steady progress in technology:
• part per billion systematic control
• 1% systematic control
• Major developments in
- photocathodes ( I & P )
- polarimetry- high power cryotargets- nanometer beam stability- precision beam diagnostics- low noise electronics- radiation hard detectors
Electroweak Physics Away from Z pole
Precision Z observables establish anchor points for the Standard ModelAway from the Z resonance, New Physics neutral‐current
interac+ons can be found
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Processes with poten+al sensi+vity to PV couplings: ‐ neutrino‐nucleon deep inelas+c scaHering ‐ Atomic parity viola+on (APV) ‐ parity‐viola+ng electron scaHering
NuTeV at Fermilab 133Cs at Boulder
At low energies:
The Standard Model neutral current is well studied at the Z pole
Proton Weak Charge
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If measurement at low energy comes up different than SM predic+on, indicates proton charged for some other (parity‐viola+ng) interac+on
Proton Extrapolation
G0
PVA4
HAPPEX
SAMPLEProton
weak charge
SM
PDG
0 0.05 0.1 0.15 0.2 0.25 0.3
Q2 !GeV2"0
0.1
0.2
0.3
0.4
ALRp!!!!!
HAPPEX
SAMPLE
PVA4
G0
0 0.05 0.1 0.15 0.2 0.25 0.3
Q2 !GeV2"0
0.1
0.2
0.3
0.4
ALRp!!!!! Theory
estimate for anapole FF
RDY et al., PRL99,122003(2007)
slope due to proton structure
Global fit of exis+ng strange‐quark program data limits hadronic uncertain+es and constrains proton weak charge
“Strange Quark” program collected extensive precision WNC form‐factor data
Bounding the vector weak charge
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SM value
R. Young et al., PRL 99 122003 (2007)
With this parameteriza+on for hadronic effects, what can be said about Standard Model parameters?
QpW = 2 C1u + C1d
These “form factor” measurements offer a powerful
constraint on new physics orthogonal to other lepton‐quark coupling combina+ons
Neutral Weak charge of Up, Down quarks
Proton Weak Charge with Qweak
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δQWp=4%
- Non‐perturba+ve theory g ~ 2π Λ ~ 29 TeV
- Extra Z’ g ~ 0.45 m Z’ ~ 2.1 TeV
Figure: R.Young
PV‐DIS with SOLID at 11 GeV
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Deep Inelas+c ScaHering
For an isoscalar target like 2H, structure funcCons largely cancel in the raCo at high x
e-
N X
e-
Z* γ*
At high x, APV becomes independent of x, W, with well‐defined SM predic+on for Q2 and y
Sensi+ve to new physics at the TeV scale
a(x) and b(x) contain quark distribu+on func+ons fi(x)
0
1
at high x
a(x) =310
!2C1u
"1 +
2c+
u+ + d+
#!C1d
"1 +
2s+
u+ + d+
#+ · · ·
$
0b(x) =
310
[2C2u !C2d]!
uv + dv
u+ + d+
"+ · · ·
PVDIS w/ Base Equipment
Prescott et al(SLAC)
PDG Best Fit
Young Full Fit
Sample
6 GeV PVDIS 3% Ad measurement:Bands correspond to central values of either PDG best fit or Young et al.’s best fit.
StandardModel
SHMS
HMS
Proposal approved for 11 GeV:Factor of ~ 2 to 3 improvement
E08‐011: PVDIS off 2H at 6 GeV
•08-011 provides first look, at x~0.25-0.3• Insensitive to CSV, HT, but possibly sensitive to the quark sea?
•11 GeV, allows greater precision at higher x, but doesn’t provide lever arm to fully separate QCD effects
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CSV with PVDISParton-level charge symmetry assumed in deriving 2H APV
Charge Symmetry Violation may arise from• u,d quark mass difference• electromagnetic effects
• Direct sensitivity of parton-level CSV• Important implications for high energy collider pdfs• Could explain significant portion of the NuTeV anomaly
Sensi+vity will e enhanced if u+d falls off more rapidly than δu‐δd as x → 1
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Higher Twist
≠• APV sensi+ve to diquarks: ra+o of weak to electromagne+c charge depends on amount of coherence (elas+c He vs PVDIS)• Do diquarks have twice the x of single quarks? High x is prime spot for valance quark‐quark higher‐twist contribu+ons (in hadronic vector term, contribu+ons from smaller axial term require constraint from neutrino data).
Subject of recent workshop at Madison, Wisconsin
Parton Modelor
leading twist
Di‐quarks
Quark‐gluondiagram
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Coherent Program of PVDIS Study
• Measure AD in NARROW bins of x, Q2 with 0.5% precision
• Cover broad Q2 range for x in [0.3,0.6] to constrain HT• Search for CSV with x dependence of AD at high x
• Use x>0.4, high Q2, and to measure a combination of the Ciq’s
Strategy: requires precise kinema+cs and broad range
x y Q2
New Physics no yes no
CSV yes no no
Higher Twist yes no yes
Fit data to:
C(x)=βHT/(1‐x)3
Addi+onal measurements from hydrogen target provides high precision on d/uMeasurement on nulcei gives access to “EMC” type effects
(isovector vector mean field effects, Cloet, Bentz and Thomas)
SOLID: Solenoid Spectrometer for PVDIS Physics
Figure from E.Chudakov
trackingE-calgas Cerenkovcollimator
A large solenoidal spectrometer works • need BaBar, CDF or CLEOII Solenoid• fast tracking, particle ID and “parity” counting
electronics• polarimetry ~ 0.4%
• 20o - 35o, E’~ 1.5 - 5 GeV• δp/p ~ 2% • some regions 10’s of kHz/mm2
• Pion rejection with Cerenkov + segmented calorimeter.
15PAC34
Sta+s+cal Errors (%) vs Kinema+cs
4 months at 11 GeV
2 months at 6.6 GeV
Sta+s+cal uncertainty σA/A (%)shown at center of bins in Q2, x
Strategy: sub-1% precision over broad kinema+c range for sensitive Standard Model test and detailed study of hadronic structure contributions
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PAC34
Precision on sin2θW
fig from J. Erler
Impressive precision on sin2θw (comparable to Qweak)
but real value is in sensi+vity to different combina+on of couplings
Constraint on contact interac+ons
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PAC34
Precision on sin2θW
fig from J. Erler
Impressive precision on sin2θw (comparable to Qweak)
but real value is in sensi+vity to different combina+on of couplings
Constraint on contact interac+ons
Theore+cal developments on higher‐twist contribu+ons, RγZ, target‐mass correc+ons, etc. will be crucial
Neutrino data will pay a key role in controlling these effects
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D. Armstrong, T. Averett, J. M. Finn
William and Mary P. Decowski
Smith College L. El Fassi, R. Gilman,
R. Ransome, E. SchulteRutgers
W. Chen, H. Gao, X. Qian, Y. Qiang, Q. Ye
Duke UniversityK. A. Aniol
California StateG. M. Urciuoli
INFN, Sezione di RomaA. Lukhanin, Z. E. Meziani,
B. SawatzkyTemple University
P. M. King, J. RocheOhio University
E. BeiseUniversity of Maryland
W. Bertozzi, S. Gilad, W. Deconinck, S. Kowalski,
B. Moffit MIT
Benmokhtar, G. Franklin, B. Quinn
Carnegie MellonG. Ron
Tel Aviv University
T. HolmstromLongwood University
P. MarkowitzFlorida International
X. JiangLos Alamos
W. KorschUniversity of Kentucky
J. Erler Universidad Autonoma de
MexicoM. J. Ramsey-Musolf
University of WisconsinC. Keppel
Hampton UniversityH. Lu, X. Yan, Y. Ye, P. Zhu
University of Science and Technology of China
N. Morgan, M. PittVirginia Tech
J.-C. PengUniversity of Illinois
H. P. Cheng, R. C. Liu, H. J. Lu, Y. Shi
Huangshan UniversityS. Choi, Ho. Kang, Hy. Kang B. Lee,
Y. OhSeoul National University
J. Dunne, D. DuttaMississippi State
K. Grimm, K. Johnston, N. Simicevic, S. WellsLouisiana Tech
O. Glamazdin, R. PomatsalyukNSC Kharkov Institute
for Physics and Technology
Z. G. XiaoTsinghua University
B.-Q. Ma, Y. J. MaoBeijing UniversityX. M. Li, J. Luan, S. Zhou
China Institute of Atomic Energy
B. T. Hu, Y. W. Zhang, Y. Zhang
Lanzhou UniversityC. M. Camacho, E. Fuchey,
C. Hyde, F. ItardLPC Clermont,
Université Blaise Pascal A. Deshpande
SUNY Stony BrookA. T. Katramatou,
G. G. PetratosKent State University
J. W. MartinUniversity of Winnipeg
Collabora+onP. Bosted, J. P. Chen, E. Chudakov, A. Deur,
O. Hansen, C. W. de Jager, D. Gaskell, J. Gomez,
D. Higinbotham, J. LeRose, R. Michaels, S. Nanda, A. Saha, V. Sulkosky,
B. Wojtsekhowski
Jefferson LabP. A. Souder, R. Holmes
Syracuse UniversityK. Kumar, D. McNulty,
L. Mercado, R. Miskimen
U. MassachusettsH. Baghdasaryan, G. D. Cates, D. Crabb, M. Dalton, D. Day,
N. Kalantarians, N. Liyanage, V. V. Nelyubin, B. Norum, K. Paschke, S. Riordan,
O. A. Rondon, M. Shabestari, J. Singh, A. Tobias, K. Wang,
X. Zheng
University of VirginiaJ. Arrington, K. Hafidi,
P. E. Reimer, P. Solvignon
Argonne
MOLLER(Measurement of Lepton‐Lepton Electroweak Reac+on)
MØller scaHering at 11 GeV
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Møller ScaHering at 11 GeV
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Purely leptonic reac+on
�
APV ∝meElab (1− 4sin2ϑW )
�
δ(sin2ϑW )sin2ϑW
≅ 0.05δ(APV )APV
�
σ ∝ 1Elab
Figure of Merit rises linearly with Elab
Møller ScaHering at 11 GeV
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•Comparable to the best measurements (LEP and BaBar)•Best new measurement un+l Linear Collider or Neutrino Factory•At this level, one‐loop effects from “heavy” physics
Compelling opportunity with high luminosity, polarized 11 GeV beam:
APV = 35.6 ppbδ(APV) = 0.73 ppb δ(QeW) = ± 2.1 (stat.) ± 1.0 (syst.) %
δ(sin2θW) = ± 0.00026 (stat.) ± 0.00012 (syst.) ~ 0.1%
Luminosity and Stability at Jlab upgrade makes feasible a factor of 5 improvement over E158
Λee ~ 25 TeV reach
not just “another measurement” of sin2θW ; 0.0003 passes a threshold
Purely leptonic reac+on
�
APV ∝meElab (1− 4sin2ϑW )
�
δ(sin2ϑW )sin2ϑW
≅ 0.05δ(APV )APV
�
σ ∝ 1Elab
Figure of Merit rises linearly with Elab
1‐loop EW Physics / Contact Interac+ons
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102
103
0.23 0.232 0.234
sin2!
lept
eff
mH [G
eV]
"2/d.o.f.: 11.8 / 5
Al(SLD) 0.23098 ± 0.00026
A0,b
fb 0.23221 ± 0.00029
± 0.00029
Average 0.23153 ± 0.00016
had= 0.02758 ± 0.00035(5)
mt= 172.7 ± 2.9 GeV
1‐loop EW Physics / Contact Interac+ons
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102
103
0.23 0.232 0.234
sin2!
lept
eff
mH [G
eV]
"2/d.o.f.: 11.8 / 5
Al(SLD) 0.23098 ± 0.00026
A0,b
fb 0.23221 ± 0.00029
± 0.00029
Average 0.23153 ± 0.00016
had= 0.02758 ± 0.00035(5)
mt= 172.7 ± 2.9 GeV
1‐loop EW Physics / Contact Interac+ons
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This proposal
Powerful impact on Standard Model consistency in 1‐loop EW fit
102
103
0.23 0.232 0.234
sin2!
lept
eff
mH [G
eV]
"2/d.o.f.: 11.8 / 5
Al(SLD) 0.23098 ± 0.00026
A0,b
fb 0.23221 ± 0.00029
± 0.00029
Average 0.23153 ± 0.00016
had= 0.02758 ± 0.00035(5)
mt= 172.7 ± 2.9 GeV
1‐loop EW Physics / Contact Interac+ons
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This proposal
Powerful impact on Standard Model consistency in 1‐loop EW fit
!!|g2
RR ! g2LL|
= 7.5 TeV
Le1e2 =!
i,j=L,R
g2ij
2!2ei!µeiej!
µej
Extremely sensi+ve to new physics at heavy mass scales
102
103
0.23 0.232 0.234
sin2!
lept
eff
mH [G
eV]
"2/d.o.f.: 11.8 / 5
Al(SLD) 0.23098 ± 0.00026
A0,b
fb 0.23221 ± 0.00029
± 0.00029
Average 0.23153 ± 0.00016
had= 0.02758 ± 0.00035(5)
mt= 172.7 ± 2.9 GeV
1‐loop EW Physics / Contact Interac+ons
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This proposal
!!|g2
RR + g2LL|
= 4.4 TeV !gRL
= 5.2 TeV |g2RR ! g2
LL|
Best current limits on 4-electron contact interactions: LEPII at 200 GeV(Average of all 4 LEP experiments)
insensi+ve toOR
Powerful impact on Standard Model consistency in 1‐loop EW fit
!!|g2
RR ! g2LL|
= 7.5 TeV
Le1e2 =!
i,j=L,R
g2ij
2!2ei!µeiej!
µej
Extremely sensi+ve to new physics at heavy mass scales
g2RR ! g2
LL
!2=
e2R ! e2
L
M2Z!
! 1(7.5TeV)2
Example of Complementarity to LHC: Heavy Z’
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•Most unified theories predict addi+onal neutral Z’•LHC can find these ~5 TeV, can determine proper+es 1‐2 TeV •11 GeV Moller can help pin down couplings
LHC can extract mass, width, and AFB to get constraint on
eR/eL
Moller sensi+vity:
Figure: F. Petriello & S. Quackenbush
eR/eL
eR2 ‐ eL2
New Challenges
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• ~ 150 GHz sca0ered electron rate– Design to flip Pockels cell ~ 2 kHz
– 80 ppm pulse‐to‐pulse staDsDcal fluctuaDons
• Electronic noise and density fluctuaDons < 10‐5
• Pulse‐to‐pulse beam ji0er ~ 10s of microns at 1 kHz
• Pulse‐to‐pulse beam monitoring resoluDon ~ few micron at 1 kHz
• 1 nm control of beam centroid on target– Modest improvement on control of polarized source laser transport elements
– Improved methods of “slow helicity reversal”
• > 10 gm/cm2 target needed to achieve desired luminosity– 1.5 meter Liquid Hydrogen target: ~ 5 kW @ 85 μA
• Full Azimuthal acceptance with θlab ~ 5 mrad– novel two‐toroid spectrometer
– radiaDon hard integraDng detectors
• Robust and Redundant 0.4% beam polarimetry– Plan to pursue both Compton and Atomic Hydrogen techniques
Two Toroid Spectrometer
x (m)−0.1 −0.05 0 0.05 0.1
y (
m)
−0.1
−0.05
0
0.05
0.1
0.006
0.008
0.01
0.012
0.014
0.016
0.018
z=6.00 m
x (m)−0.2 −0.15 −0.1 −0.05 0 0.05 0.1 0.15 0.2
y (
m)
−0.2
−0.15
−0.1
−0.05
0
0.05
0.1
0.15
0.2
0.006
0.008
0.01
0.012
0.014
0.016
0.018
z=9.00 m
x (m)−0.4 −0.3 −0.2 −0.1 0 0.1 0.2 0.3 0.4
y (
m)
−0.4
−0.3
−0.2
−0.1
0
0.1
0.2
0.3
0.4
0.006
0.008
0.01
0.012
0.014
0.016
0.018
z=14.50 m
x (m)−0.6 −0.4 −0.2 0 0.2 0.4 0.6
y (
m)
−0.6
−0.4
−0.2
0
0.2
0.4
0.6
0.006
0.008
0.01
0.012
0.014
0.016
0.018
z=20.00 m
x (m)−0.8 −0.6 −0.4 −0.2 0 0.2 0.4 0.6 0.8
y (
m)
−0.8
−0.6
−0.4
−0.2
0
0.2
0.4
0.6
0.8
0.006
0.008
0.01
0.012
0.014
0.016
0.018
z=24.00 m
x (m)−1 −0.8 −0.6 −0.4 −0.2 0 0.2 0.4 0.6 0.8 1
y (
m)
−1
−0.8
−0.6
−0.4
−0.2
0
0.2
0.4
0.6
0.8
1
0.006
0.008
0.01
0.012
0.014
0.016
0.018
z=28.25 m
Radial Fields (edge effect) creates azimuthal defocussing which populates the full ring at the detector
1 meter radial focus, 30 meters from targetClean separa+on from backgrounds
PMTs
Air Light-guides
straggled primary beam to 5*theta_mscatt
shield
Lead
beam of neutrals from target
e+p
e+e
Target & Detectors
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parameter value
length 150 cm
thickness 10.7 gm/cm2
X0 17.5%
p,T 35 psia, 20K
power 5000 WE158 scaNeringchamber
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MOLLER collabra+on
The Parity Program at 11 GeV
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Each experiment is a significant technical challenge•MOLLER: high rate, low noise, beam asymmetries, backgrounds•PVDIS: fast coun+ng, backgrounds, detector development•BOTH: polarimetryBoth Experiments will have a big impact with important physics•Endorsed by NSAC Long Range Plan
Proposals were submiHed for each to the last PAC
APPROVED!
Next steps: Technical Design Review in late 2009 / early 2010 for MOLLER~1 year later for PVDIS
Moller and PVDIS apparatus in Hall A
These are big projects• 100+ authors on each proposal• Beam +me ~2 years each• Earliest +me to run 2015• Es+mated construc+on cost (together) ~25M$• Not part of the original JLab upgrade
Requires independent funding
Summary
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0.001 0.01 0.1 1 10 100 1000
[GeV]
0.225
0.230
0.235
0.240
0.245
0.250
sin
2!
W
^ APV(Cs)
Qweak [JLab]
Moller [SLAC]
"-DIS
ALR
(had) [SLC]
AFB
(b) [LEP]
AFB
(lep) [Tevatron]
screening
antiscreening
Moller [JLab]
PV-DIS [JLab]
SM
current
future
µ
(µ)Precision electroweak physics is already being
done at Jefferson Lab.
Future measurements in the 11 GeV JLab erawill be challenging but feasible, and present a tremendous opportunity to play a role in discovery in the LHC era.
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29
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Sensi+vity of proposed 11 GeV program
Cs
PVDIS
Qweak
6 GeV
PVDIS
Polarimetry
Compton Polarimetry
Need major effort to establish unimpeachable credibility for 0.4% polarimetry = two separate measurements, with separate techniques, which can be cross‐checked.
For scaHered electrons in chicane:two Points of well‐defined energy
• Asymmetry zero crossing• Compton Edge
Integrate between to minimize error on analyzing power
“independent” Photon analysis also normalizable at ~0.5%
0 500 1000 1500 2000 2500 30000
0.1
0.2
0.3
0.4
0.5
0.6
0.7 Ee=11GeVλ=532nm
k (MeV)
Cross‐sec+on
(barn)
0 500 1000 1500 2000 2500 3000
−5
0
5
10
15
20
25
30
Asymmetry (%
)
k (MeV)
Ee=11GeVλ=532nm
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High Precision ComptonAt high energies, SLD achieved 0.5%.
Why do we think we can do beHer?
•SLD polarimeter near interac+on region ‐ background heavy•No photon calorimeter for produc+on
•Hall A has “coun+ng” mode (CW)•Efficiency studies•Tagged photon beam
• Greater electron detector resolu+on
So why haven’t we done beHer before?
0 10 20 30 40
−5
0
5
10
15
20
25
30
Design (4.5GeV)
PREX
H‐III
PV‐DIS
11 GeV
Distance from primary beam [mm]
Asymmetry
•Small asymmetries = long +me to precision = cross‐checks are difficult
•No one tried zero‐crossing technique (zero crossing gets hard near the beam)
•photon calorimetry gets tricky at small Eγ
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High Precision ComptonAt high energies, SLD achieved 0.5%.
Why do we think we can do beHer?
•SLD polarimeter near interac+on region ‐ background heavy•No photon calorimeter for produc+on
•Hall A has “coun+ng” mode (CW)•Efficiency studies•Tagged photon beam
• Greater electron detector resolu+on
So why haven’t we done beHer before?
0 10 20 30 40
−5
0
5
10
15
20
25
30
Design (4.5GeV)
PREX
H‐III
PV‐DIS
11 GeV
Distance from primary beam [mm]
Asymmetry
•Small asymmetries = long +me to precision = cross‐checks are difficult
•No one tried zero‐crossing technique (zero crossing gets hard near the beam)
•photon calorimetry gets tricky at small Eγ
Its a major effort and a full +me job, but there is no obvious fundamental show‐stopper
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�
n+
n−= e−2µB / kT ≈ 10−14
Atomic Hydrogen For Moller TargetMoller polarimetry from polarized atomic hydrogen gas, stored in an ultra-cold magnetic trap
• 100% electron polarization
• tiny error on polarization
• thin target (sufficient rates but no dead time)
• Non-invasive
• high beam currents allowed
• no Levchuk effectE. Chudakov and V. Luppov, IEEE Transactions on Nuclear Science, v 51, n 4, Aug. 2004, 1533‐40Brute force polarization
10 cm, ρ = 3x1015/cm3 in B = 7 T at T=300 mK
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CSV Theory and Data
MRST PDF global with fit of CSVMar+n, Roberts, S+rling, Thorne [Eur Phys J C35, 325 (04)]:
90% conf limitBroad minimum
(90% C.L.)
fully explains NuTeV
doubles NuTeV deviation
Analy+c calcula+on similar to global fit
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Analysis ofBlumlein and
Botcher
F2 dominates the cross sec+on
Best HT Data
Higher twist is clearlyseen at the PVDIS
kinema+cs.
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QWeakMeasuring the proton form-factor weak charge
Small angle, low Q2 ∼ 0.03 GeV2 to suppress target structureProton structure F, constrained by strange quark program, contributes ~30% to asymmetry, ~2% to δ(QW
p)/ QWp
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QWeakMeasuring the proton form-factor weak charge
Small angle, low Q2 ∼ 0.03 GeV2 to suppress target structureProton structure F, constrained by strange quark program, contributes ~30% to asymmetry, ~2% to δ(QW
p)/ QWp
�
APV ≈ −230 ± 5 ± 4 ppb
�
δ QWp = ± 4% ⇒ δ(sin2θW ) = ± 0.3%
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QWeakMeasuring the proton form-factor weak charge
Small angle, low Q2 ∼ 0.03 GeV2 to suppress target structureProton structure F, constrained by strange quark program, contributes ~30% to asymmetry, ~2% to δ(QW
p)/ QWp
A new standard in precision• New Spectrometer system• Control and correction for beam systematics• Polarimetry approaching 1% (new)• Low system noise - 6.5 GHz rate!• High rate, radiation hard readout• Background and calibration precision
mid‐2010 through 2011
�
APV ≈ −230 ± 5 ± 4 ppb
�
δ QWp = ± 4% ⇒ δ(sin2θW ) = ± 0.3%
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PVDIS on the Proton: d/u at High x
Deuteron analysis has largenuclear corrections (Yellow)
APV for the proton has no such corrections
(complementary to BONUS)
The challenge is to get statistical and systematic errors ~ 2%
3-month run
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CSV in Heavy Nuclei: EMC Effect
Addi+onal possible
applica+on of SoLID
Isovector‐vector mean
field. (Cloet, Bentz,
and Thomas)
5%