Precision Measurement of
Parity-violation in Deep Inelastic
Scattering Over a Broad
Kinematic Range
JLab Proposal PR12-10-07
Jan 25, 2010
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1
P. 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 Lab
P. A. Souder, R. Holmes
Syracuse University
K. Kumar, D. McNulty,
L. Mercado, R. Miskimen
U. Massachusetts
H. 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 Virginia
J. Arrington, K. Hafidi,
P. E. Reimer, P. Solvignon
Argonne
D. Armstrong, T. Averett,
J. M. Finn
William and Mary
P. Decowski
Jan 25,College
2010
Smith
Collaboration
L. El Fassi, R. Gilman,
R. Ransome, E. Schulte
P. Markowitz
Florida International
Rutgers
K. Grimm, K. Johnston,
N. Simicevic, S. Wells
X. Jiang
Louisiana Tech
W. Chen, H. Gao, X. Qian,
Y. Qiang, Q. Ye
Los Alamos
O. Glamazdin, R. Pomatsalyuk
Duke University
University of Kentucky
K. A. Aniol
California State
G. M. Urciuoli
INFN, Sezione di
Roma
A. Lukhanin, Z. E. Meziani,
B. Sawatzky
W. Korsch
J. Erler
Universidad Autonoma
de Mexico
M. J. Ramsey-Musolf
University of Wisconsin
Temple University
E. Beise
University of Maryland
Benmokhtar, G. Franklin,
B. Quinn
Carnegie Mellon
G. Ron
J.-C. Peng
University of Illinois
H. P. Cheng, R. C. Liu,
H. J. Lu, Y. Shi
Huangshan University
S. Choi, Ho. Kang, Hy. Kang B.
Lee, Y. Oh
Tel Aviv University
T. Holmstrom
Longwood UniversitySolid
Beijing University
China Institute of
Atomic Energy
Virginia Tech
MIT
B.-Q. Ma, Y. J. Mao
Hampton University
N. Morgan, M. Pitt
W. Bertozzi, S. Gilad,
W. Deconinck, S. Kowalski,
B. Moffit
Tsinghua University
C. Keppel
University of Science
and Technology of
China
Ohio University
Z. G. Xiao
X. M. Li, J. Luan, S. Zhou
H. Lu, X. Yan, Y. Ye, P. Zhu
P. M. King, J. Roche
NSC Kharkov Institute
for Physics and
Technology
Seoul National
University
J. Dunne, D. Dutta
Mississippi State
B. T. Hu, Y. W. Zhang,
Y. Zhang
Lanzhou University
C. M. Camacho, E. Fuchey,
C. Hyde, F. Itard
LPC Clermont,
Université Blaise
Pascal
A. Deshpande
SUNY Stony Brook
A. T. Katramatou,
G. G. Petratos
Kent State University
J. W. Martin
University of Winnipeg
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Outline
• Physics potential
– Standard Model Test
– Charge Symmetry Violation (CSV)
– Higher Twist
– d/u for the Proton
• New Solenoidal Spectrometer (SoLID)
• Polarimetry
Jan 25, 2010
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PV Asymmetries: Any Target
and Any Scattering Angle
Forward
Backward
(gAegVT + gVegAT)
•The couplings gT depend on electroweak physics as well as on the
weak vector and axial-vector hadronic current
•For PVDIS, both new physics at high energy scales as well as
interesting features of hadronic structure come into play
•A program with a broad kinematic range can untangle the physics
Jan 25, 2010
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PVDIS: Electron-Quark Scattering
Many new physics models give rise to neutral ‘contact’ (4-Fermi) interactions:
Heavy Z’s, compositeness, extra dimensions…
Consider f1 f1  f 2 f 2 or
f1 f 2  f1 f 2
gij’s for all f1f2
combinations and L,R
combinations


A
V
V
A
Moller PV is insensitive to the Cij
C2u and C2d are small and poorly known:
one combination can be accessed in PV DIS
C1u and C1d will be determined to high precision by Qweak, APV Cs
Jan 25, 2010
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Deep Inelastic Scattering
eZ*
N
GF Q 2

a(x)  Y (y) b(x)

2
e-
APV
X
x  x Bjorken
*
 C Q f (x)
a(x) =
 Q f (x)
+
1i
y 1 E / E
fi   fi  f i
i
2 +
i i
i

For an isoscalar target like 2H, structure
 in the ratio at high x
functions largely cancel
At high x, APV becomes independent of x, W,
with well-defined SM prediction for Q2 and y
New combination of:
Vector quark couplings C1q
Also axial quark couplings C2q

 C Q f (x)
b(x) 
 Q f (x)

2i
i
i
i
2 
i i
i
at high x
 0.62s  
3
a(x)  (2C1u  C1d )  1  
10
u  d  

0
3
 u v  dv 
b(x)  (2C2u  C2d ) 




10
u d
1
Sensitive to new physics at the TeV scale
PVDIS: Only way to measure C2q
Jan 25, 2010
i i
a(x) and b(x)
contain quark
distribution functions
fi(x)
Solid
Unknown radiative corrections
for coherent processes
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Sensitivity: C1 and C2 Plots
6 GeV
World’s data
PVDIS
Precision Data
Qweak
PVDIS
Cs
Jan 25, 2010
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Search for CSV in PV DIS
u (x)  d (x)?
p
n
d (x)  u (x)?
p
n
u(x)  u p (x)  d n (x)
•u-d mass difference
•electromagnetic effects
d(x)  d p (x)  u n (x)
•Direct observation of parton-level CSV would be very exciting!
•Important implications for high energy collider pdfs

•Could explain significant portion of the NuTeV anomaly
For APV in
electron-2H
DIS:
APV
APV
 0.28
u  d
ud
Sensitivity will be further enhanced if u+d falls off more rapidly than u-d as x  1
Strategy:
•measure or constrain higher twist effects at x ~ 0.5-0.6
•precision measurement of APV at x → 0.8 to search for CSV
Jan 25, 2010
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Sensitivity with PVDIS
RCSV 
Jan 25, 2010
 APV x 
APV x 
 0.28
 u x   d x 
u x  d x 
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Need Full Phenomenology
 d 2 
2
xyM 

) F2

  2 xyF1  (1  y 
y
2E
 dxdy  EM
L
F1  F2 (1  R )  R 
T


V
d  
G
2
xyM Z
Z
[ g A{2 xyF1  (1  y 
) F2 }]

 
y
2E
 dxdy  Z 2 2
2
A
d  
G

[ gV x(2  y ) F3Z ]


 dxdy  Z 2 2
2
ABPV
 VZ   AZ

 EM
Jan 25, 2010
 VZ
a( x) 
 EM
BIG
Solid
There are 5
relevant structure
functions
 AZ
f ( y )b( x) 
 EM
Small; use ν data
(Higher twist workshop
at Madison, Wisconsin)
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Why HT in PVDIS is Special
Bjorken,
PRD 18, 3239 (78)
Start with Lorentz Invariance
A
Wolfenstein,
NPB146, 477 (78)


l  D | j  ( x) J  (0)  J  ( x) j (0) | D eiq x d 4 x

V  u  u  d  d  S   u  u  d  d
Next use CVC
(deuteron only)
l  D | j  ( x) j (0) | D eiqx d 4

VV  l  D | V  ( x)V  (0) | D eiq x d 4 x
1
(C1u  C1d ) VV  (C1u  C1d ) SS
3
A
1
VV  SS
3
Zero in QPM
VV  SS  (V  S )(V  S )  l  D | u ( x)  u ( x)d (0)  d (0) eiqx d 4 x
HT in F2 may be dominated
by quark-gluon correlations
Higher-Twist valance
quark-quark correlations
Vector-hadronic piece only
Jan 25, 2010
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Quark-Quark vs Quark-Gluon
Parton Model
or
leading twist
What is a true
quark-gluon
operator?
Quark-gluon
diagram
u
u
d
Quark-gluon operators
correspond to
Might be computed transverse momentum
on the lattice
Di-quarks
Jan 25, 2010
u
Solid
QCD equations
of motion
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Statistical Errors (%) vs Kinematics
Strategy: sub-1% precision over broad kinematic range for sensitive
Standard Model test and detailed study of hadronic structure contributions
Error bar σA/A (%)
shown at center of bins
in Q2, x
4 months at 11 GeV
2 months at 6.6 GeV
Jan 25, 2010
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Coherent Program of PVDIS Study
Strategy: requires precise kinematics and broad range
Fit data to: A  A1  
HT

C(x)=βHT/(1-x)3

1
2
  CSV x 
3 2
(1  x) Q

• 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
Jan 25, 2010
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x
y
Q2
New Physics
no
yes
no
CSV
yes
no
no
Higher Twist
yes
no
yes
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PVDIS on the Proton: d/u at High x
u ( x)  0.91d ( x)
a ( x) 
u ( x)  0.25d ( x)
P
Deuteron analysis has large
nuclear corrections (Yellow)
APV for the proton has no
such corrections
(complementary to BONUS)
3-month run
The challenge is to get statistical and systematic errors ~ 2%
Jan 25, 2010
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CSV in Heavy Nuclei: EMC Effect
Additional
possible
application of
SoLID
Jan 25, 2010
5%
Solid
Isovectorvector mean
field. (Cloet,
Bentz,
and Thomas)
16
SoLID Spectrometer
Gas Cerenkov
Shashlyk
Jan 25, 2010
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Baffles
GEM’s
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Layout of Moller and PVDIS
Jan 25, 2010
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Access to the Detectors
• End Cap rolls
backward along
the beam line on
Hilman Rollers
• 342 metric tons
for both end
caps with baffles
installed
• Must allow for
5% rolling
resistance
Jan 25, 2010
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Baffle geometry and support
Jan 25, 2010
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20
Error Projections for Moller
Polarimetry
F. Maas from
U. Mainz has joined
the collaboration
and will lead this
project.
Mainz has the
infrastructure
and other resources
needed to carry
out this project.
Jan 25, 2010
Table from MOLLER director’s
review by E. Chudakov
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Summary of Compton
Uncertainties
Jan 25, 2010
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Error Budget in %
Statistics
0.3
Polarimetry
0.4
Q2
0.2
Radiative Corrections
0.3
Total
0.6
Jan 25, 2010
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Summary
• The physics is varied and exciting.
– Excellent sensitivity to C2u and C2d.
– Test CSV at quark level.
– Unique window on higher twists.
• We will build a novel apparatus (with many
other possible applications, eg. SIDIS)
Jan 25, 2010
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Atomic Hydrogen For Moller Target
Moller polarimetry from polarized atomic
hydrogen gas, stored in an ultra-cold
magnetic trap
10 cm, ρ = 3x1015/cm3
in B = 7 T at T=300 mK
n
 e 2 B / kT  1014
n
•
Tiny error on polarization
•
Thin target (sufficient rates but
no dead time)
•
100% electron polarization
•
Non-invasive
•
High beam currents allowed
•
No Levchuk effect
E. Chudakov and V. Luppov, IEEE Transactions on
Nuclear Science, v 51, n 4, Aug. 2004, 1533-40
Brute force polarization
Jan 25, 2010
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High Precision Compton
So why haven’t we done
better before?
At high energies, SLD achieved 0.5%.
Why do we think we can do better?
• Small asymmetries
= long time to precision
• SLD polarimeter near interaction
= cross-checks are difficult
region - background heavy
• Zero-crossing technique is new. (zero
• No photon calorimeter for production
crossing gets hard near the beam)
• Photon calorimetry is harder at small Eγ
• Hall A has “counting” mode (CW)
• Efficiency studies
• Tagged photon beam
11 GeV
Its a major effort, but there is no
obvious fundamental showstopper
Jan 25, 2010
Asymmetry
• Greater electron detector resolution
Solid
Design
(4.5GeV)
PV-DIS
H-III
PREX
Distance from primary beam [mm]
26
Layout ofSpectrometer using
CDF coil
• Coil mounting is well
understood from CDF
– Designed to be
supported by end
– Supports allow
radial movement in
both ends for
thermal
– One end fixed
axially
• Will need to check for
decentering forces
due to field asymmetry
(Lorentz forces)
Jan 25, 2010
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