1. May 20, 2006 DIS Parity at 12 GeV P. A. Souder DIS-Parity 12 GeV How to reach high x: Prospects with a High-Lumonosity Solenoidal Spectrometer P. A. Souder Syracuse University Thanks to Bosted, Brodsky, Chudakov, Kumar, Londergan, Meziani, Michaels, Reimer, Ramsey-Musolf, Paschke, Pitt, Zheng

2. May 20, 2006 DIS Parity at 12 GeV P. A. Souder OUTLINE DIS-Parity and the Standard Model Discovering new hadronic physics Requirements for a new spectrometer Solution: Solenoidal Spectrometer

3. May 20, 2006 DIS Parity at 12 GeV P. A. Souder The couplings g T depend on electroweak physics as well as on the weak vector and axial-vector hadronic current For DIS-Parity, 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 (g A e g V T +  g V e g A T ) PV Asymmetries Weak Neutral Current (WNC) Interactions at Q 2 << M Z 2 Longitudinally Polarized Electron Scattering off Unpolarized Fixed Targets

4. May 20, 2006 DIS Parity at 12 GeV P. A. Souder New Physics Reach: Q weak and Møller Examples: Kurylov, Ramsey-Musolf, Su To be relevant, new SM tests must have small enough errors to show up on plots like this

5. May 20, 2006 DIS Parity at 12 GeV P. A. Souder 3% 10% -10% Add DIS-Parity: ± DIS-Parity requires a factor of 5-10 improvement In δA/A to be competitive with Q weak, Møller No 1-4sin 2 θ W suppression of A PV 1.0%

6. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Hadronic Structure for Parity Violating Electron DIS f i (x) are quark distribution functions For an isoscalar target like 2 H, structure functions largely cancel in the ratio: e-e- N X e-e- Z*Z* ** Especially for x>0.5 or so A PV becomes independent of x, Q 2, W, and depends only on y

7. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Quark Distribution Functions vs x JLab can explore the Valance region 0.5<x<0.8 What can possibly go wrong?

8. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Why should we believe DISparity when no one Believes NuTeV?

9. May 20, 2006 DIS Parity at 12 GeV P. A. Souder PW Ratio depends on the following assumptions: Isoscalar target (N=Z) include only light (u, d) quarks neglect heavy quark masses assume isospin symmetry for PDFs no nuclear effects (parton shadowing, EMC, ….) no higher twist effects radiative corrections OK? (γ-W boxes?) no contributions outside Standard Model Assumptions for the Paschos-Wolfenstein Ratio Nobody believes that this is the problem JLab 12 GeV issues

10. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Use PV To Study hadronic structure? PV might have the smallest errors:<1% –PV: Systematics are P e and –Cross sections: Systematics are target length, solid angle, etc.

11. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Search for CSV in PV DIS Sensitivity will be further enhanced if u+d falls off more rapidly than  u-  d as x  1 measure or constrain higher twist effects at x ~ 0.5-0.6 precision measurement of A PV at x → 0.8 to search for CSV Strategy: 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 A PV in electron- 2 H DIS:

12. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Phenomenological Parton CSV PDFs MRST Phenomenological PDFs include CSV for 1 st time: Martin, Roberts, Stirling, Thorne (03): Choose restricted form for parton CSV: Best fit: κ = -0.2, large uncertainty ! Best fit remarkably similar to model CSV predictions MRST ADEL [f(x): 0 integral; matches to valence at small, large x] 90% conf limit (κ)

13. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Higher Twist Coefficients in parity conserving (D i ) and nonconserving (C i ) Scattering (Does not Evolve) Evolves according To DGLAP equations Higher Twist is what is left over Higher Twist is any Q2-dependent deviation From the SM prediction

14. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Going from LO to NNNLO Greatly Reduces the Extracted Higher Twist Coefficients xD(x) Q 2 min D/Q 2 min (%) LONNNLOLONNNLO 0.1-0.2-.0070.0010.5-142 0.2-0.3-.110.0031.0-110.0 0.3-0.4-.06-0.0011.7-3.5-0.5 0.4-0.5.220.112.684 0.5-0.6.850.393.82210 0.6-0.72.61.45.84524 0.7-0.87.34.49.47847 F 2 (x,Q 2 )=F 2 (x)(1+D(x)/Q 2 ) Q 2 =(W 2 -M 2 )/(1/x-1)Q 2 min =Q 2 (W=2) If D(x)~C(x), Parity might show higher twist At high x without needing QCD evolution.

15. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Interpretation of Higher Twist A PV 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/Q 4 effects On the other hand, some higher twist effects may cancel in ratio, so A PV may have little dependence on Q 2.  Observing a clean higher twist operator has recently become very interesting.

16. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Probing Higher Twist with PV Sacco, R-M preliminary Looking beyond the parton descriptionPV Deep Ineslastic eD (J Lab 12 GeV) ~0.4% E=11 GeV  =12.5 0 Different PDF fits

17. May 20, 2006 DIS Parity at 12 GeV P. A. Souder A PV in DIS on 1 H Determine that higher twist is under control Determine standard model agreement at low x Obtain high precision at high x Allows d/u measurement on a single proton! Vector quark current! (electron is axial-vector) + small corrections

18. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Uncertainties in d/u at High x, and the Errors we Would Like to Achieve with PV Measurements Deuteron analysis has nuclear corrections A PV for the proton has no such corrections Must simultaneously constrain higher twist effects The challenge is to get statistical and systematic errors ~ 2%

19. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Complete PV DIS Program (Including 12 GeV) Hydrogen and Deuterium targets Better than 2% errors –It is unlikely that any effects are larger than 10% x-range 0.25-0.75 W 2 well over 4 GeV 2 Q 2 range a factor of 2 for each x point –(Except x~0.75) Moderate running times With HMS/SHMS: search for TeV physics With larger solid angle apparatus: higher twist, CSV, d/u…

20. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Scorecard xyQ2Q2 pd Higher twistYesNoYesX IsospinYes?No X d/uYesNo X New PhysicsNoYesNoX

21. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Apparatus Needed for PVDIS

22. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Reaching Large x at 11 GeV 50% azimuthal coverage assumed 6 GeV Need Large θ for large x and Q 2 HMS and SHMS are fine for small θ (and large y) W<2

23. May 20, 2006 DIS Parity at 12 GeV P. A. Souder 2 to 3.5 GeV scattered electrons 20 to 40 degrees Factor of 2 in Q 2 range at moderate x High statistics at x=0.7, with W>2 Range of W and Q 2

24. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Cut on 0.6<y<0.8 Large range in Q2 for HT study High x (>0.7) accessible with W 2 >4 Large acceptance allows feasible runtime requests  /e ratio is not extreme, but cannot integrate Details on Kinematics and π/e Ratio

25. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Large Angle Large Acceptance: Concept CW 90 µA at 11 GeV 40-60 cm liquid H 2 and D 2 targets Luminosity > 10 38 /cm 2 /s JLab Upgrade Need high rates at high x For the first time: sufficient rates to make precision PV DIS measurements solid angle > 200 msr Resolution<2% Count at 100 kHz online pion rejection of 10 2 Need magnet to block γ’s and low energy π’s

26. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Solenoid vs Toroid Solenoid takes advantage of the small beam spot requires less bending Problem: shield detector from line of sight photons B points out of page

27. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Geometry for a Solenoidal Spectrometer

28. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Shielding the detector with baffles Large acceptance in The θ direction Shield in the ø direction

29. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Use Many Slits for Large ø Acceptance Curvature matches trajectories of Scattered particles There are 20 segments

30. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Plan View of the Spectrometer CDF or BaBar Solenoid?

31. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Detector Packages Pb Glass TA Counter (material exists?) Gas Cerenkov (Easy for <4 GeV electrons) Tracking: GEM detectors

32. May 20, 2006 DIS Parity at 12 GeV P. A. Souder The COMPASS GEM Detector Size: 31×31 cm 2 Rate: 25 kH/mm 2

33. May 20, 2006 DIS Parity at 12 GeV P. A. Souder COMPASS GEM Time and Spatial Resolution

34. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Resolution of Spectrometer θ P 2 GeV3 GeV5 GeV 20 o 1.5% 2.4% 30 o 0.7% 1.0% 1.4% 40 o 0.8%

35. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Rates as a function of kinematic bin

36. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Example: d/u of Proton d/u Compare MAD Spectr. to Solenoid Spectr. off shell on shell Curves from Melnithouk and Thomas What Physics is Allowed by New Device? MAD 120 days Solenoid 40 days

37. May 20, 2006 DIS Parity at 12 GeV P. A. Souder EMC effect in Parity Violation ? Cross section data from J. Gomez et.al. PRD 49 (1994) 4348 This study might be done with 8.5 GeV beam, 50 μa beam

38. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Other Users of the Spectrometer 1.A 1 n 2.Charm from H 3.DVCS 4.Two γ A1nA1n x01 0 A 1 n →1 as x→1?? (Show that result is independent of W, Q 2 )

39. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Summary and Outlook Parity-Violating DIS can probe exciting new physics at high x One can start now (at 6 GeV) –Do 2 low Q 2 points (P-05-007, X. Zheng contact) Q 2 ~ 1.1 and 1.9 GeV 2 Either bound or set the scale of higher twist effects –Take data for W<2 (P-05-005, P. Bosted contact) Duality Could help extend range at 11 GeV to higher x A short run to probe TeV physics in PV DIS off 2 H: Hall A or C The bulk of the program requires a dedicated spectrometer/detector CSV can be probed at high x Higher twist can be controlled or exploited Additional physics topics could be addressed by dedicated spectrometer –Transverse (beam-normal) asymmetries in DIS –Polarized targets: g 2 and g 3 structure functions

40. May 20, 2006 DIS Parity at 12 GeV P. A. Souder Conclusion A lot of interesting physics happens at JLab with an 11 GeV beam. Why not build a solenoidal spectrometer to observe it??? (With good precision)