# Presentation: 517949

## DIS-Parity: Measuring sin2θW with Parity Violating Deep Inelastic Scattering 

- Introduction: Weinberg-Salam Model and sin2(W)
- Parity NonConserving Electron Deep Inelastic Scattering
- Possibilities at SLAC End Station A

- 9 June 2003

## Weinberg-Salam model and sin2(W)

- Remember—I’m not the expert here.

- Unification of Weak and E&M Force
- SU(2)—weak isospin—Triplet of gauge bosons
- U(1)—weak hypercharge—Single gauge boson
- Electroweak Lagrangian:
*J****, J***Y**isospin and hypercharge currents
- g, g0 couplings between currents and fields

*Gary Larson, The Far Side*

- Standard Model parameters:
- Charge, *e *, em
- g , GF  from  lifetime
- MZ
- sin2(W)

- Vector:  giV= t3L(i) – 2qi sin2(W)
- Axial:    giA = t3L(i)

*Charge*

*Weak isospin*

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## sin2(W) measurements below Z-pole

- sin2(W) measurements below Z-pole

- DIS-Parity:
- Deep Inelastic Scattering Parity Violation on Deuterium
- SLAC LOI now, data in 2006-2007??
** ****h**Q2**i** = 20 GeV2

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## Polarized e- deuterium DIS

- Polarized *e**-** deuterium* DIS

- Q2 =  – q2 = 2(EE**0** –** k****¢** **k**)
-          – m*l*2 – m*l*2
-     **1⁄4** 4EE**0** sin2(/2)
-  = **q****¢** **P**/M = E – E**0**
- x = Q2/2M
- y = **q****¢** **P/k****¢** **P** =  / E
- W2 = (**P** + **q**)2
-       = M2 + 2M – Q2
- s = (**k** + **P**)2
-   = Q2/xy + M2 + m*l*2

- Look for left-right asymmetry in polarized eD deep inelastic scattering
- Asymmetry caused by interference between Z0 and  diagrams.

- Use deuterium target: u(x) ** ́** d(x)
- Large asymmetry:  Ad**1⁄4** 10-4£ Q2
- Cahn and Gilman **PRD** 17, 1313 (1978)

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## Standard Model Extensions

- e

- e

- New Z’

- 4-Fermi Contact

- Heavy short range
- interaction

- e

- e

- gnew

- gnew

- up

- new

- e

- e

- up

- Compositeness

- Leptoquarks

- up

- LQ

- e

- e

- Z’

- gAe

- gVq

- up

- up

- gVq

- Z**0** mass limit of 1.5TeV

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## How does DIS-Parity fit in?

- SLAC DIS-Parity

- NuTeV (Fermilab)

- Isoscaler quark scattering
- (2C1u-C1d)+Y(2C2u-C2d)

- Quark scattering (from nucleus)
- Weak charged and neutral current difference

- Expt. Probe different parts of Lagrangian

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## Textbook Physics:  Polarized e- d scattering

- Repeat SLAC exp. (30 years later) w/better statistics and systematics:
- Beam current 17 A vs. 4 A at SLAC in ’78			£ 4 stat
- 100 cm target vs. 30 cm target					£ 3 stat
- Higher Q2 (beam energy) h18i vs h1.6i GeV			£ 11 stat
- Pe (electron polarization) = 80%  vs. 37%	 			£ 2 stat
-   Pe 1⁄4 0.3% vs. 6%						£ 20 sys
- Better understanding of QCD (parton distributions/higher twist)
- Better control of beam systematics (polarization)

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## DIS Formalism

- Note that each of the Cia are sensitive to *different* possible S.M. extensions.

- Longitudinally polarized electrons on unpolarized isoscaler (deuterium) target (derivation is problem for listener).

- C1q ) NC vector coupling to *q*
-         £ NC axial coupling to *e*
- C2q ) NC axial coupling to *q*
-         £ NC vector coupling to *e*

- Cia provide sensitivity to sin2(W)

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## Sensitivity to sin2(W)

- Look for interference between Large photon term and New Physics

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## Experimental Constraints and Kinematics

- DIS region				**)** Q**2 **> 2.0 GeV2
- 						**)** W2 > 2.0 GeV2
- Small sea quark uncertainties 	**)** x > 0.3
- Minimize higher twist		**)** Q2 > 10 GeV2
- 						**)** x < 0.7
- Better sensitivity to sin**2**(**W**) 	**)** Large Y
- d(x)/u(x) uncertainties 		**)** deuterium target
- Minimize  backgrounds 		**)** E**0**/E>0.3 (y<0.7)
- Reasonable rates			**)** determine Q**2** event by event
- 						**)** realistic run time
- In fact, well matched to available beam at SLAC with spectrometer built from (mostly) pre-existing components.
**	****	****	****h**x**i** = 0.41	 	**h**Q**2****i** = 19.1 GeV**2**
**	****	****	****h**Y**i** = 0.82 		**h**W**2****i** = 29.0 GeV**2**

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## Experimental Setup/Electron Beam

- Experiment located at SLAC End Station A
*Helicity related beam problems are already solved for E-158 M**øller*
- 35.6, 38.8 GeV beam— rotation in (g-2) precession in beam line.
- 9£1011 e-/spill at 120 Hz; 5£108 spills
- 80-85% Beam polarization; unpolarized deuterium target

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## DIS-Parity Spectrometer

- Pair of identical spectrometers at 12o
- Electron focus of 9-20 GeV
-  Acceptance:
**§**8 mr at 9 GeV
**§**12 mr at 20 GeV
- Lead-glass array
-  E/E **1⁄4** 4.5%
- Used in E155
- Rates require new flash ADC system
- (Kamland/Berkeley design)

- Use existing magnets/spectrometer design

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## SLAC DIS-Parity Collaboration

- S. Kuhn
*Old Dominion University*
- P. Decowski
*Smith College*
- F.J. Decker, R. Erickson, T. Fieguth, M. Olson, J.L. Turner, D. Walz, M. Woods
*Stanford Linear Accelerator Center*
- R. Holmes, P.A. Souder
*Syracuse University*
- D. Crabb, D. Day, P. McKee, O. Rondon, F.R. Wesselmann
*University of Virginia*
- D. Armstrong, T. Averett, K. Griffioen, M. Finn
*College of William and Mary*
- N. Akopov, A. Apyan, R. Avakian, A. Avetisian, K. Dallakyan S. Darbinian, K. Ispirian, T. Navasardyan, S. Taroyan
*Yerevan Physics Institute*
- and others. . .

- J.R. Arrington, K. Hafidi, R.J. Holt, H.E. Jackson, D.H. Potterveld, P.E. Reimer, E. Schulte, X. Zheng
*Argonne National Laboratory*
- Y. Kolomensky
*University of California, Berkeley*
- R. Carr, B. Filippone, R. McKeown, M.J. Ramsey-Musolf
*California Institute of Technology*
- E. Chudakov, D. Mack, R. Michaels
*Jefferson Laboratory*
- S. Penttila
*Los Alamos National Laboratory*
- E.J. Beise
*University of Maryland, College Park*
- R. Arnold, P.E. Bosted, R. Hicks, S.E. Rock
*University of Massachusetts, Amherst*
- J. Erler
*Universidad Nacional Autonoma de Mexico*

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## Uncertainties in Ad and sin2(W)

| Theoretical Systematic Uncertainties | sin2(W)
(abs £ 10-3) |
| --- | --- |
| Dynamic Higher Twist | 0.1 |
| Electroweak Radiative Corrections | 0.2 |
| Quark distributions | 0.2 |
| Charge Symmetry Violation | 0.2 |
|  R (=L/T) | 0.1 |
| Total | 0.4 |

| Experimental Syst. Uncertainties | Ad/Ad
(%) | sin2(W)
(abs £ 10-3) |
| --- | --- | --- |
| Beam polarization | 0.3% | 0.3 |
| Q2 | 0.3% | 0.3 |
| Electromagnetic
Radiative Corrections | 0.3% | 0.3 |
| False Asymmetries | 0.1% | 0.1 |
| Pion Contamination | 0.1% | 0.1 |
| Pair symmetric bkg | 0.1% | 0.1 |
| Target Purity/Density | 0.1% | 0.1 |
| Electronics/pile up | 0.1% | 0.1 |
| Total | 0.6% | 0.6 |

|  | Ad/Ad
(%) | sin2(W)
(abs £ 10-3) |
| --- | --- | --- |
| Statistical | 0.6% | 0.6 |

- Total Uncertainty:
- A/A = **§**0.8%
- sin2(W) = **§**0.0009

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## Beam Polarization Measurement

- Based on SLD polarimeter (0.5%—we want 0.3%)
- Detect both scattered electron and photon (independent measurement)
- High Power Laser:  P = 99.8§ 0.1%, 1017 photons/pulse (50mJ)
- Small (< 0.1%) radiative corrections

*Compton Polarimeter*

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## Q2 Uncertainty

- Spectrometer Focus

- Q2 = 4 EE**0** sin2(/2)
- E:
-  E < 0.1%—calibration of beam line magnets
- Zero point of longitudinal beam polarization defines 37.22 GeV
- E**0** sin2(/2)
- Optics Measurements for E**0** (0.2%) and  (0.2mr)
- Floating Wire calibration in E140 achieved this
- Central angle **§** 0.05 mr
- Central Momentum (E**0**/E**0**)** ****§** 0.03

- Other:
- “Point” Targets/masks
- Quad off measurements

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## Expected sin2(W) Results

- Expected sin2(W) Results

- Ad/Ad = **§**0.6% (stat)
-                **§**0.6% (syst)
-               (**§** 0.8% combined)
-  sin2(W) = **§** 0.0003 (stat)
-                      **§ **0.0003 (sys)
-                      **§** 0.0004 (theory)
-                    (**§** 0.0009 combined)

*What about C**iq**’s?*

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## Exp. Constraints on C1u, C1d, C2u and C2d

- Present experimental constraints are wide open, except for APV
- (1 standard deviation limits shown)

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## Extracted Signal—It’s all in the binning

- Fit Asymmetry data as fn. of Y
- 	intercept = 2C1u – C1d
- 	slope      = 2C2u – C2d

- Note—Polarization uncertainty enters in slope and intercept
- Aobs = PAd **/** P(2C1u–C1d) + P(2C2u–C2d)Y] but is correlated

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## DIS-Parity determines 2C2u-C2d

- Combined result significantly constrains 2C2u–C2d.
- PDG 2C2u–C2d = –0.08 **§** 0.24  Combined (2C2u–C2d) = **§** 0.009
- £ 27 improvement (S.M 2C2u – C2d = 0.0986)

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## Additional Possibilities with H2 

- Asymmetry in d-2p
- Interpretation does not require knowledge of parton distributions (except charge symmetry).
- Ratio of asymmetries: Ap/Ad
- If C1a’s are known, measures r(x) **1⁄4** d(x)/u(x) at large x.
- Polarization cancels out.

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## DIS-Parity: Conclusions

- Measurements of sin2(W) below MZ provide strict tests of the Standard Model.
- Parity NonConserving DIS provides complimentary sensitivity to other planned measurements.
- DIS-Parity Violation measurements can be carried out in at SLAC in the near term future.

******sin****2****(********W****) = 0.0009******
******(2C****2u**** – C****2d****) = 0.009**

- Status:
- LOI submitted to SLAC EPAC
- Presentation to EPAC on 12 June
- Full Proposal in Fall 2003

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## Aside:  Renormalizations Schemes

- Definition of sin2(W) depends on renormalization scheme which is used.
- Well defined relationships for converting between schemes depending on mt and mH.

- Familiar, simple
- Large *m**t*, *M*H dependence

- Most precise—No *m**t*, *M*H dependence
*m**t*, *M*H reenter w/other observables

- Based on coupling constants—theorist’s definition
- Not conceptually simple
- Determined through global fits

- Simple
- Phenomenological definition

*See PDB “Electroweak Model” (J. Erler and P. Langacker) for a better discussion.*

*Gary Larson, The Far Side*

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003

## Detector and Expected Rates

|  | x | E0
(GeV) | Y | Q2
(GeV2) | W2
(GeV2) | /e | Rate
(/spill) | Ad/Ad
(%) | sin2(W)
(£ 100) |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  | 0.31 | 15.8 | 0.89 | 9.8 | 36.1 | 3.10 | 4.4 | 1.39 | 0.14 |
|  | 0.36 | 17.5 | 0.86 | 10.8 | 32.4 | 0.40 | 3.6 | 1.41 | 0.15 |
|  | 0.41 | 19.3 | 0.83 | 11.9 | 28.7 | 0.10 | 2.9 | 1.47 | 0.16 |
|  | 0.47 | 21.0 | 0.79 | 13.0 | 25.0 | 0.03 | 2.2 | 1.58 | 0.17 |
|  | 0.53 | 22.7 | 0.76 | 14.0 | 21.3 | 0.00 | 1.5 | 1.76 | 0.20 |
|  | 0.59 | 24.4 | 0.72 | 15.1 | 17.6 | 0.00 | 1.0 | 2.06 | 0.24 |
|  | 0.67 | 26.1 | 0.69 | 16.2 | 13.9 | 0.00 | 0.5 | 2.60 | 0.30 |
|  | 0.75 | 27.8 | 0.65 | 17.2 | 10.2 | 0.00 | 0.2 | 3.68 | 0.44 |
| Average | 0.41 | 19.1 | 0.82 | 11.82 | 28.97 | 0.94 |  |  |  |
| Total |  |  |  |  |  |  | 16.3 | 0.6 | 0.09 |

- Paul E. Reimer, Argonne National Laboratory

- 9 June 2003