Download presentation

Presentation is loading. Please wait.

Published byAnna Buckley Modified over 3 years ago

1
DIS-Parity 12 GeV Physics opportunities in PVeS with a Solenoidal Spectrometer Many slides liberated from: P. Souder, K. Kumar (… and their sources) Kent Paschke University of Massachusetts

2
June 14, 2006DIS Parity at 12 GeV Kent Paschke 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 Electrons Scattering off Unpolarized Fixed Targets

3
June 14, 2006DIS Parity at 12 GeV Kent Paschke PVeS and Physics Beyond the SM: 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

4
June 14, 2006DIS Parity at 12 GeV Kent Paschke 1% 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

5
June 14, 2006DIS Parity at 12 GeV Kent Paschke Parity Violating Electron DIS e-e- N X e-e- Z*Z* * as x gets large, the sea is negligible For an isoscalar target like 2 H, structure functions largely cancel in the ratio:

6
June 14, 2006DIS Parity at 12 GeV Kent Paschke New Physics: measuring sin 2 ( W ) Note that each of the C iq are sensitive to different possible S.M. extensions. Hall C Standard Upgrade

7
June 14, 2006DIS Parity at 12 GeV Kent Paschke Exp. Constraints on C 1u, C 1d, C 2u and C 2d Combined result significantly constrains 2C 2u –C 2d. PDG 2C 2u –C 2d = –0.08 ± 0.24 Combined (2C 2u –C 2d ) = ± From P. Reimer, describing PV-DIS possible with standard upgrade

8
June 14, 2006DIS Parity at 12 GeV Kent Paschke What happened to NuTeV? Hall C Standard Upgrade NuTeV result on sin 2 W is 3 from standard model… why isnt everyone more excited? Various problems in interpretation, mostly in the hadronic physics … PV-DIS will have the same problem! Too bad if you want to test the Standard Model … … but very cool if you like hadronic physics! PV-DIS Standard Model test interpretation might be clouded by: Isospin-symmetry violation for PDFs Contributions from higher twist The silver lining: one can study the clouds!

9
June 14, 2006DIS Parity at 12 GeV Kent Paschke In principle, PV-DIS is sensitive to: Contributions from higher twist Isospin-symmetry violation for PDFs d/u PDF ratio as x->1 Nuclear effects (parton shadowing, EMC, ….) PV-DIS and hadronic physics What is needed: Large kinematic range (Q 2 range at fixed, moderate x Bj ) Large acceptance High luminosity Excellent background suppression

10
June 14, 2006DIS Parity at 12 GeV Kent Paschke Higher Twist Coefficients in parity conserving (D i ) and nonconserving (C i ) Scattering Evolves according To DGLAP equations Higher Twist is what is left over (Does not Evolve) Higher Twist is any Q 2 -dependent deviation From the SM prediction Remember: for 2 H at moderate x, structure functions largely cancel in A PV

11
June 14, 2006DIS Parity at 12 GeV Kent Paschke 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 Clean observation of a higher twist operator may be possible.

12
June 14, 2006DIS Parity at 12 GeV Kent Paschke Probing Higher Twist with PVeS Sacco, R-M preliminary Looking beyond the parton descriptionPV Deep Inelastic eD (J Lab 12 GeV) ~0.4% E=11 GeV = Different PDF fits x ~ 0.2 Slide from Ramsey-Mulsolf

13
June 14, 2006DIS Parity at 12 GeV Kent Paschke Higher Twist unlikely at (moderately) low x, possible at high x xD(x)Q 2 min D/Q 2 min (%) LONNNLOLONNNLO 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 C(x) acts like D(x), PVeS might show higher twist at high x without needing QCD evolution. MRST 04

14
June 14, 2006DIS Parity at 12 GeV Kent Paschke Charge Symmetry Violation Charge symmetry quark mass difference: n-p mass difference: Charge symmetry Violation (CSV) Sather: Analytic Quark Model Approximation for Valence Parton CSV. Leads to analytic results (model-dependent) Londergan,Murdock,Thomas hep-ph/ MRST, Eur.Phys.J. 39, 155 (05); Glueck, Jimenez-Delgado, Reya, PRL95, (05) Contributes even if m u = m d and M n = M p add to quark model CSV term MRST incorporate QED splitting with PDFs in global fit to high energy data Figures from T.Londergan QED Splitting

15
June 14, 2006DIS Parity at 12 GeV Kent Paschke Phenomenological Parton CSV PDFs MRST PDFs from global fits include CSV for 1 st time: Martin, Roberts, Stirling, Thorne [Eur Phys J C35, 325 (04)]: Choose restricted form for parton CSV: Best fit: κ = -0.2, large uncertainty ! Best fit remarkably similar to quark model CSV calculations MRST (2004) ADEL (1994) [f(x): 0 integral; matches to valence PDFs at small, large x] 90% conf limit (κ) Slide from T.Londergan

16
June 14, 2006DIS Parity at 12 GeV Kent Paschke Search for CSV in PV DIS Sensitivity will be further enhanced if u+d falls off more rapidly than u- d as x 1 Strategy: constrain higher twist effects at x ~ precision measurement of A PV at x 0.7 to search for CSV 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: MRST fit suggests ~1% effect at x = 0.7 (QED + bag) says ~6% effect!

17
June 14, 2006DIS Parity at 12 GeV Kent Paschke A PV in DIS on 1 H Strategy: 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! + small corrections

18
June 14, 2006DIS Parity at 12 GeV Kent Paschke d/u at High x 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
June 14, 2006DIS Parity at 12 GeV Kent Paschke Scorecard xyQ2Q2 pd Higher twistYesNoYesX IsospinYes?No X d/uYesNo X New PhysicsNoYesNoX

20
June 14, 2006DIS Parity at 12 GeV Kent Paschke Coherent PV DIS Program (Including 12 GeV) Hydrogen and Deuterium targets Better than 2% errors x-range 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…

21
EMC effect in PVeS 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 50 days running. Targets: 15 cm LD mm Fe Targets 1% RL C12 Targets

22
June 14, 2006DIS Parity at 12 GeV Kent Paschke 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 , 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 , P. Bosted contact) Duality Could help extend range at 11 GeV to higher x Probe TeV physics in PV DIS off 2 H: Hall C at 12 GeV The bulk of this coherent program requires a dedicated spectrometer/detector Higher twist must be controlled (or exploited) CSV can be probed at high x Standard Model test is interpretable when coupled with hadronic studies Uniquely clean d/u at high x EMC effect in PVeS Additional physics topics could be addressed by dedicated spectrometer –Transverse (beam-normal) asymmetries in DIS –Polarized targets: g 2 and g 3 structure functions

23
June 14, 2006DIS Parity at 12 GeV Kent Paschke 0.4

24
June 14, 2006DIS Parity at 12 GeV Kent Paschke 0.4

25

26
June 14, 2006DIS Parity at 12 GeV Kent Paschke 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

27
June 14, 2006DIS Parity at 12 GeV Kent Paschke 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

28
June 14, 2006DIS Parity at 12 GeV Kent Paschke Charge Symmetry Violation Charge symmetry We know the origins of parton CSV: o quark mass difference: o n-p mass difference: Charge symmetry Violation (CSV) Sather: Analytic Quark Model Approximation for Valence Parton CSV. Leads to analytic results (model-dependent)

29
June 14, 2006DIS Parity at 12 GeV Kent Paschke MRST, Eur.Phys.J. 39, 155 (05); Glueck, Jimenez-Delgado, Reya, PRL95, (05) QED evolution, quark radiates photon Evolve in Q 2 qualitatively similar to quark model CSV QED varied while quarks frozen contributes even if m u = m d and M n = M p add to quark model CSV term increase CSV ~ factor 2 MRST incorporate QED splitting with PDFs in global fit to high energy data Slide from T.Londergan QED Splitting : a New Source of Isospin Violation QED Splitting : a New Source of Isospin Violation

Similar presentations

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google