Higher%20Twist%20in%20PVDIS

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Higher Twist in PVDIS
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Outline

• PVDIS
• SM goals
• SOLID vs Hall C
• CSV
• Higher twist
• Other nuclei

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Parity-Violating Electron Scattering
Weak Neutral Current (WNC) Interactions at Q2 ltlt
MZ2
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First Electron Parity Experiment
This experiment convinced the world that the
Z-boson violated parity
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PV Asymmetries Any Target
(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

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Electron-Quark Phenomenology
Moller PV is insensitive to the Cij
C1u and C1d will be determined to high precision
by Qweak, APV Cs
C2u and C2d are small and poorly known one
combination can be accessed in PV DIS
New physics such as compositeness, leptoquarks
Deviations to C2u and C2d might be fractionally
large
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Deep Inelastic Scattering
a(x) and b(x) contain quark distribution
functions fi(x)
For an isoscalar target like 2H, structure
functions largely cancel in the ratio at high x
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
Sensitive to new physics at the TeV scale
C2q inaccessible in elastic scattering
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Comprehensive Search for New Neutral Current
Interactions
Important component of indirect signatures of
new physics
Many new physics models give rise to neutral
contact (4-Fermi) interactions Heavy Zs,
compositeness, extra dimensions
One goal of neutral current measurements at low
energy AND colliders Access ? gt 10 TeV for as
many f1f2 and L,R combinations as possible
LEPI, SLC, LEPII HERA accessed some
parity-violating combinations but precision
dominated by Z resonance measurements
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DIS at high x (Approved)
at large x
0.5 fractional precision on the asymmetry is
needed!
Feasible (in narrow kinematics) with existing
JLab spectrometers.
Hall C HMS / SHMS spectrometers
JLab 11 GeV proposal Conditional approval
Paschke, Reimer, Zheng et al.

• Experimental systematic errors challenging
• Averaged over large Q2, W, and x range

Exploratory measurements at 2 precision will be
made at 6 GeV (2009)
Michaels, Reimer Zheng et al.
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A Design for Precision PV DIS Physics

• High Luminosity on LH2 LD2
• Better than 1 errors for small bins
• x-range 0.25-0.75
• W2 gt 4 GeV2
• Q2 range a factor of 2 for each x
• (Except x0.75)
• Moderate running times

• Solenoid (from BaBar, CDF or CLEOII )
• contains low energy backgrounds (Moller, pions,
  etc)
• trajectories measured after baffles
• Fast tracking, particle ID, calorimetry, and
  pipeline electronics
• Precision polarimetry (0.4)

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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
PAC34
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Sensitivity C1 and C2 Plots
6 GeV
Worlds data
PVDIS
PVDIS
Precision Data
Qweak
Cs
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Precision on sin2?W
Impressive precision on sin2?w (comparable to
Qweak) but real value is in sensitivity to
different combination of couplings
fig from J. Erler
Compare precise sin2?W both with and without
quarks
Constraint on contact interactions
Jan. 27, 2009
PAC34
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Search for CSV in PV DIS

• u-d mass difference
• electromagnetic effects

• 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
Sensitivity will be further enhanced if ud falls
off more rapidly than ?u-?d as x ? 1
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Charge Symmetry Data

• Broad minimum
• (90 C.L.)

90 conf limit
fully explains NuTeV
Analytic calculation similar to global fit
doubles NuTeV deviation
MRST PDF global with fit of CSV Martin, Roberts,
Stirling, Thorne Eur Phys J C35, 325 (04)
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Sensitivity with PVDIS
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Phenomenology
There are 5 relevant structure functions
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Basic Questions for the Workshop

• Can the higher twist effects be sufficiently
  controlled for the SM test?
• Are the higher twist effects in themselves of
  sufficient interest to merit their own bullet in
  the proposal?

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Basic Questions for Workshop

• Are hadronic effects so small that the Hall C
  program is sufficient for the SM test?
• Are hadronic effects so large and complicated
  that SM physics is impossible?
• Can SOLID untangle reasonable hadronic effects
  and SM violations?

SOLID is very expensive
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Summary of Phenomenology
Question is Higher Twist dominated by a(x),
or is higher twist in the small terms in b(x) or
R(x) important?
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Higher Twist
Does higher twist fully cancel from the asymmetry?
At higher x, a more interesting higher twist
effect may be evident
For 12C, APVelasticgt0, APVDISlt0 KKs Thesis

• APV sensitive to diquarks ratio of weak to
  electromagnetic charge depends on amount of
  coherence
• Do diquarks have twice the x of single quarks?
• If Spin 0 diquarks dominate, likely only 1/Q4
  effects

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R for ? vs Z
From Kulagin and Petti, PRD 76, 094023 (07)
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Data on R vs x
R is 20 ?10 in f(y) ?1 in f(y)b(x)
Large x bins
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Parton Distribution Functions
Sea quarks that contribute to a(x) and s quarks
that contribute to a(x) vanish rapidly for xgt0.5
CAUTION PDFs use as input 40 years of precise
data plus reasonable guesses. One must
distinguish which features are data and which
features are guesses.
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Higher Twist without the QPM
Bjorken, PRD 18, 3239 (78)
Wolfenstein, NPB146, 477 (78)
Zero in QPM
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Blumlein and Botcher
F2 is sort of the cross section
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Higher Twist Coefficients in parity conserving
(Di) and nonconserving (Ci) Scattering
Evolves according To DGLAP equations
Higher Twist is what is left over
Higher Twist is any Q2-dependent deviation From
the SM prediction
(Does not Evolve)
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Going from LO to NNNLO Greatly Reduces Higher
Twist Coefficients
F2(x,Q2)F2(x)(1D(x)/Q2)
Q2(W2-M2)/(1/x-1)
Q2minQ2(W2)
x D(x) D(x) Q2min D/Q2min() D/Q2min()
LO NNNLO LO NNNLO
0.1-0.2 -.007 0.001 0.5 -14 2
0.2-0.3 -.11 0.003 1.0 -11 0.0
0.3-0.4 -.06 -0.001 1.7 -3.5 -0.5
0.4-0.5 .22 0.11 2.6 8 4
0.5-0.6 .85 0.39 3.8 22 10
0.6-0.7 2.6 1.4 5.8 45 24
0.7-0.8 7.3 4.4 9.4 78 47
MRST, PLB582, 222 (04)
APVAPV(1C(x)/Q2)
If D(x)C(x), Parity might show higher twist At
high x without needing QCD evolution.
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D(x) versus x
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F2D(x) All x on Same Scale
Are moments dominated by large x?
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Higher Twist without the QPM
Bjorken, PRD 18, 3239 (78)
Wolfenstein, NPB146, 477 (78)
Zero in QPM
Higher-Twist quark-quark correlations
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Quark-Quark and Quark-Gluon
What is a true quark-gluon operator?
Parton Model or leading twist
Quark-gluon diagram
Di-quarks
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NLO Diagrams
DGLAP Evolution
Diagrams (a)-(c) cancel in APV
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Coherent Program of PVDIS Study
Strategy requires precise kinematics and broad
range
Fit data to
C(x)ßHT/(1-x)3

• 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 xgt0.4, high Q2, and to measure a
  combination of the Ciqs

x y Q2
New Physics no yes no
CSV yes no no
Higher Twist yes no yes
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Fits
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APV in DIS on 1H
small corrections

• Allows d/u measurement on a single proton!
• Vector quark current! (electron is axial-vector)

• Determine that higher twist is under control
• Determine standard model agreement at low x
• Obtain high precision at high x

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PVDIS on the Proton d/u at High x
Deuteron analysis has large nuclear corrections
(Yellow)
APV for the proton has no such corrections (comple
mentary to BONUS)
3-month run
The challenge is to get statistical and
systematic errors 2
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CSV in Heavy Nuclei EMC Effect
Isovector-vector mean field. (Cloet, Bentz, and
Thomas)
Additional possible application of SoLID
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Collaboration

• 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,

L. El Fassi, R. Gilman, R. Ransome, E.
Schulte Rutgers W. Chen, H. Gao, X. Qian, Y.
Qiang, Q. Ye Duke University K. A. Aniol
California State G. M. Urciuoli INFN, Sezione di
Roma A. Lukhanin, Z. E. Meziani, B.
Sawatzky Temple University P. M. King, J.
Roche Ohio University E. Beise University of
Maryland W. Bertozzi, S. Gilad, W. Deconinck, S.
Kowalski, B. Moffit MIT Benmokhtar, G.
Franklin, B. Quinn Carnegie Mellon G. Ron Tel
Aviv University T. Holmstrom Longwood University
P. Markowitz Florida International X. Jiang Los
Alamos W. Korsch University of Kentucky J. Erler
Universidad Autonoma de Mexico M. J.
Ramsey-Musolf University of Wisconsin C.
Keppel Hampton University H. Lu, X. Yan, Y. Ye,
P. Zhu University of Science and Technology of
China N. Morgan, M. Pitt Virginia Tech 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 Seoul
National University J. Dunne, D.
Dutta Mississippi State
K. Grimm, K. Johnston, N. Simicevic, S.
Wells Louisiana Tech O. Glamazdin, R.
Pomatsalyuk NSC Kharkov Institute for Physics and
Technology Z. G. Xiao Tsinghua University B.-Q.
Ma, Y. J. Mao Beijing University X. M. Li, J.
Luan, S. Zhou China Institute of Atomic Energy 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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Error Budget in
Statistics 0.3
Polarimetry 0.4
Q2 0.2
Radiative Corrections 0.3
Total 0.6
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How do we know that antiquarks are negligible at
large x?
Drell-Yan production of muon pairs
The small quantity is directly observed. No
subtractions are needed, as is the case for F3
data.
When xF0, x1x2x, and Mx2s. Hence x for both
the quark and anti-quark are known. The cross
section drops rapidly with x
Clean data exist with x0.6 and Mµµ2gt10
Smith et al., PRL 46, 1607(81)
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Compare ? F3 to global parton fitson a linear
scale
Note vertical scale
Useful at x0.5 Problems at x0.7
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0.45
0.55
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0.65
0.75
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Neutrino data on xF3 from NuTeV, CCFR, CDHSW
Nice data set!
But it is shown on a log plot. What does it
look like on a linear scale?
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SoLID Spectrometer
Gas Cerenkov
Shashlyk
Baffles
GEMs
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Kinematics at large x
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Figure of Merit vs Scattering Angle
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Baffles
Rates in detectors reduced by more than 10
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Physics Resolution () vs Detector Resolution and
Angle
p
q
2
Q
x
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Lots of Pions at Low Energies
Need gas Cerenkov plus shower counter with
preradiator
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Pion Rejection Shashlik Detector
Total Pion Signal
Epreshower/Etotal
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Polarimetry
Need major effort to establish unimpeachable
credibility for 0.4 polarimetry with two
separate measurements, with separate techniques,
which can be cross-checked.
Compton Polarimetry

• For scattered 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

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High Precision Compton
So why havent 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
• cross-checks are difficult
• Zero-crossing technique is new. (zero crossing
  gets hard near the beam)
• Photon calorimetry is harder at small E?

• SLD polarimeter near interaction region -
  background heavy
• No photon calorimeter for production
• Hall A has counting mode (CW)
• Efficiency studies
• Tagged photon beam
• Greater electron detector resolution

Its a major effort, but there is no obvious
fundamental show-stopper
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Atomic Hydrogen For Moller Target
Moller polarimetry from polarized atomic hydrogen
gas, stored in an ultra-cold magnetic trap

• Tiny error on polarization
• Thin target (sufficient rates but no dead
  time)
• 100 electron polarization
• Non-invasive
• High beam currents allowed
• No Levchuk effect

10 cm, ? 3x1015/cm3 in B 7 T at T300 mK
E. Chudakov and V. Luppov, IEEE Transactions on
Nuclear Science, v 51, n 4, Aug. 2004, 1533-40
Brute force polarization