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

DIS-Parity 12 GeV 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

June 14, 2006 DIS Parity at 12 GeV Kent Paschke

• The couplings gT 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

(gAegV

T + gV

egAT)

PV AsymmetriesPV AsymmetriesWeak Neutral Current (WNC) Interactions at Q2 << MZ

2

Longitudinally-Polarized Electrons Scattering off Unpolarized Fixed Targets


PVeS and Physics Beyond the PVeS and Physics Beyond the SM: QSM: Qweakweak and M and Møøllerller

Kurylov, Ramsey-Musolf, Su

To be relevant, new SMtests must have smallenough errors to show

up on plots like this


1%1%Add DIS-Parity: ± Add DIS-Parity: ±

DIS-Parity requires a factor of 5-10 improvementIn δA/A to be competitive with Qweak, Møller

No 1-4sin2θW suppression of APV


)()(

)(

15

4)2(

10

3)( 11 xdxu

xsCCxa du

Parity Violating Electron DISParity Violating Electron DIS

)()()(2

2

xbyfxaQG

A FPV

)(

)()(

21

xqQ

xqQCxa

ii

iii)(

)()(

22

xqQ

xqQCxb

ii

iii

iV

eAi ggC 21 i

AeVi ggC 22

e-

N X

e-

Z* *

EEy /1 Bjorkenxx

)()(

)()()2(

10

3)( 22 xdxu

xdxuCCxb VV

du

as x gets large, the sea is negligible

For an isoscalar target like 2H, structure functions largely cancel in the ratio:


)2(10

3)( 11 du CCxa

New Physics: measuring New Physics: measuring sinsin22((WW))

)2(10

3)( 22 du CCxb

Note that each of the Ciq are sensitive to different possible S.M. extensions.

Hall C “Standard” Upgrade


Exp. Constraints on CExp. Constraints on C1u1u, C, C1d1d, C, C2u2u and C and C2d2d

Combined result significantly constrains 2C2u–C2d. PDG 2C2u–C2d = –0.08 ± 0.24 Combined (2C2u–C2d) = ±

0.014

From P. Reimer, describing PV-DIS possible with “standard” upgrade


What happened to NuTeV?What happened to NuTeV?

Hall C “Standard” Upgrade

NuTeV result on sin2W is 3 from standard model…

why isn’t 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 The silver lining: one can study the clouds!clouds!


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 physicsPV-DIS and hadronic physics

What is needed:• Large kinematic range (Q2 range at fixed, moderate xBj)• Large acceptance• High luminosity• Excellent background suppression


Higher Twist Coefficients in parity Higher Twist Coefficients in parity conserving (Dconserving (Dii) and nonconserving (C) and nonconserving (Cii) )

ScatteringScattering

F2(x,Q2) F2(x)(1 D(x) /Q2)

Evolves accordingTo DGLAP equations

Higher Twist iswhat is left over

APV (x,Q2) APV (x)(1 C(x) /Q2)

(Does not Evolve)

Higher Twist is anyQ2-dependent deviationFrom the SM prediction

)()(

)(

15

4)2(

10

3)( 11 xdxu

xsCCxa du

)()(

)()()2(

10

3)( 22 xdxu

xdxuCCxb VV

du

Remember: for 2H at moderate x, structure functions largely cancel in APV


Interpretation of Higher Twist Interpretation of Higher Twist

• 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

Clean observation of a higher twist operator may be possible.


Higher Twist unlikely at (moderately) Higher Twist unlikely at (moderately) low x, possible at high xlow x, possible at high x

x D(x) Q2min D/Q2

min(%)

LOLO NNNLONNNLO LOLO NNNLONNNLO

0.1-0.2 -.007 0.01 0.5 -14 2

0.2-0.3 -.11 0.003 1.0 -11 0.0

0.3-0.4 -.06 -0.01 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

F2(x,Q2)=F2(x)(1+D(x)/Q2) Q2=(W2-M2)/(1/x-1) Q2min=Q2(W=2)

If C(x) acts like D(x), PVeS might show higher twist at high x without needing QCD evolution.

MRST ‘04


Charge Symmetry ViolationCharge Symmetry Violation

)()(

)()(

xuxd

xdxunp

np

)()()(

)()()(

xuxdxd

xdxuxunp

np

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/0603208MRST, Eur.Phys.J. 39, 155 (05); Glueck, Jimenez-Delgado, Reya, PRL95, 022002 (05)

Contributes even if mu = md and Mn= Mp • 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”


Phenomenological Parton CSV PDFsPhenomenological Parton CSV PDFsMRST PDFs from global fits include CSV for 1st 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


Search for CSV in PV DISSearch 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 ~ 0.5 - 0.6• precision measurement of APV 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 APV in electron-2H DIS: du

du

A

A

PV

PV

3.0

MRST fit suggests ~1% effect at x = 0.7

(QED + bag) says ~6%

effect!


AAPVPV in DIS on in DIS on 11HH

APV GFQ2

2a(x) f (y)b(x)

a(x) u(x) 0.91d(x)

u(x) 0.25d(x)

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!

a(x) 3

2

2C1uu(x) C1d (d(x) s(x))

4u(x) d(x) s(x)

b(x) 3

2

2C2uuv (x) C2d dv (x)

4u(x) d(x) s(x)

+ small corrections


d/u at High xd/u at High x

Deuteron analysis has nuclearcorrections

APV for theproton has no such

corrections

Must simultaneously constrain higher twist effects

The challenge is to get statistical and systematic errors ~ 2%


ScorecardScorecard

x y Q2 p d

Higher twist Yes No Yes X

Isospin Yes? No No X

d/u Yes No No X

New Physics No Yes No X


Coherent PV DIS Program (Including 12 Coherent PV DIS Program (Including 12 GeV)GeV)

• Hydrogen and Deuterium targets• Better than 2% errors• x-range 0.25-0.75• W2 well over 4 GeV2

• Q2 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…

EMC effect in PVeSEMC effect in PVeS

Cross section data from J. Gomez et.al. PRD 49 (1994) 4348

This study mightbe done with

8.5 GeV beam,50 μa beam

50 days running. Targets:

15 cm LD2 0.17 mm Fe Targets1% RL C12 Targets


Summary and OutlookSummary and Outlook• Parity-Violating DIS can probe exciting new physics at high x• One can start now (at 6 GeV)

– Do 2 low Q2 points (P-05-007, X. Zheng contact)• Q2 ~ 1.1 and 1.9 GeV2

• 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

• Probe TeV physics in PV DIS off 2H: 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: g2 and g3 structure functions


0.4<y<0.8, E’<7GeV

• Large range in Q2 for HT study• High x (>0.7) accessible with W2>4• Large acceptance allows feasible runtime requests• /e ratio is not extreme, but cannot integrate

Details on KinematicsDetails on Kinematics

0.4<y<0.8, E’<5GeV

Solenoid SHMS


0.4<y<0.8, E’<7GeV

• Large range in Q2 for HT study• High x (>0.7) accessible with W2>4• Large acceptance allows feasible runtime requests• /e ratio is not extreme, but cannot integrate

Details on Kinematics and Details on Kinematics and ππ/e /e Ratio Ratio

0.4<y<0.8, E’<5GeV

Solenoid SHMS


Reaching Large x Reaching Large x at 11 GeVat 11 GeV

22

/

4

8.06.0

4

4020

GeVW

y

GeVE

50% azimuthal coverage assumed

6 GeV

Need Largeθ for largex and Q2

HMS and SHMSare fine for

small θ

(and large y)

W<2


•2 to 3.5 GeV scattered electrons•20 to 40 degrees•Factor of 2 in Q2 range at moderate x•High statistics at x=0.7, with W>2

Range of W and QRange of W and Q22


Charge Symmetry ViolationCharge Symmetry Violation

)()(

)()(

xuxd

xdxunp

np

)()()(

)()()(

xuxdxd

xdxuxunp

np

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)


MRST, Eur.Phys.J. 39, 155 (05); Glueck, Jimenez-Delgado, Reya, PRL95, 022002 (05)

“QED evolution”, quark radiates photonEvolve in Q2

• qualitatively similar to quark model CSV • QED varied while quarks “frozen”• contributes even if mu = md and Mn= Mp

• 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 ViolationQED Splitting”: a New Source of Isospin Violation

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

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