Un-ki Yang, Manchester 1

Nuclear Effects Nuclear Effects in Electron Scatteringin Electron Scattering

Arie BodekUniversity of Rochester

Un-ki YangUniversity of Manchester

NuFact 2008, Valencia, Spain, Jun 30 - July 5, 2008

Un-ki Yang, Manchester 2

Nuclear Effect in Electron Scattering

Of theoretical interest• Shadowing• Binding• Fermi motion

exp. (osc. / non-osc.) with all heavy targets wants:• (A)• (A)/ (d)

This is what electron data can offer using with light & heavy target as a good reference

(A)/ (d ): EMC effect

Un-ki Yang, Manchester 3

Neutrino Cross Sections

Quasi-Elastic / elastic (W=M): + n - + p

• by form factors Resonance (low Q2, W< 2): + p - + p +

• by Rein and Seghal model (overlap with DIS) Deep Inelastic Scattering: + p - + X

• by quark-parton model (non-pQCD effect, high x PDFs)

Describe DIS, resonance within quark-parton model: with PDFS, it is easy to convert (e) into () () for deuterium (d): (d,e)

• Nuclear effect in d : d/u issue at high x (A,) = (d,) * [ (A,e) / (d,e)]

• Good reference to study nuclear effect

• vs e, vector vs axial-vector, F2 vs xF3

Un-ki Yang, Manchester 4

Modeling on (e) for p and d

Describe all processes, even photo-production (Q2=0) within quark-parton model

Challenge:• High x PDFs (d/u)• Non-pert. QCD at low Q2

• Nuclear effect in the deuterium?• Resonance scattering

in terms of quark-parton model? (duality)

GRV

F2

q

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Unified Approach

NNLO pQCD +TM approach:describes the DIS and resonance data very well:• A phenomenological HT

from the NLO analysis: ~ NNLO pQCD term

Effective LO approach: (pseudo NNLO for MC) Use a LO PDFs with a new

scaling variable to absorb TM, HT, higher orders

ξW =Q2 + B

{Mν [1+ (1+Q2 / ν 2 )] + A}

Q2

Q2 +CF2 (ξw ,Q2 )[LO]

mf=M*(final state)

P=M

q

Un-ki Yang, Manchester 6

Use GRV98 LO ξ w= [Q2+B ] / [ M (1+(1+Q2/2)1/2 ) +A]

Different K factors for valence and sea

Ksea = Q2/[Q2+Csea] Kval = [1- GD

2 (Q2) ] *[Q2+C2V] / [Q2+C1V], GD

2 (Q2) = 1/ [ 1+Q2 / 0.71 ] 4

(separate u, d val. ?)

Freeze the evolution at Q2 = 0.8

Very good fits are obtained using SLAC/NMC/BCDMS p, d

with low x HERA/NMC F2

A=0.418, B=0.222, Csea = 0.381

C1V = 0.604, C2V= 0.485 2/DOF= 1268 / 1200

Fit with ξw DIS F2(d)

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F2(d) resonance

Photo-production (p)

-proton) = 4Q2 * F2(ξw, Q2)

where F2(ξw, Q2)

= Q2 /(Q2 +C) * F2(ξw )

Resonance and photo-production data

Not included in the fit

Un-ki Yang, Manchester 8

DIS at low x

2xF1 data?

All DIS F2 at high/low x e/ data are well described

Photo-production data (Q2=0) also work: thus included in the latest fit

2xF1 data (Jlab/SLAC) also work:

using F2(ξw)+R1998

Comparison with high E () data

Assume vector = axial Apply nuclear corrections

using e/ scattering data Use R=Rworld fit for 2xF1

But total (anti-neutrino) appear to be higher by 5%, xF3 issue?

(ξw) ---- (x)

E= 55 GeV

Un-ki Yang, Manchester 11

NLO Correction to xF3?

Scaling variable, ξw absorbs higher order effect on F2

Higher order effect on F2 and xF3 : not same

Check double ratio

=> not 1 but indep. of Q2

xF3(NLO)

xF3(LO)/F2 (NLO)

F2 (LO)

NLO VFS

Un-ki Yang, Manchester 12

NLO Correction to xF3

(anti-neutrino): up by 3% while (neutrino): down by 1% for all energy range.

fNLO(x)=0.914 + 0.296x

−0.374x2 + 0.165x3

Un-ki Yang, Manchester 13

Nuclear Effect in Electron Scattering

(A)/ (D ): EMC effect

Nuclear effect (x) in DIS at high Q2:

Do we see the same nuclear effect(x) in the resonance region?

Jlab data: yes but using Nachtmann variable

ξ

x

F2

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Nuclear effect in Resonance and DIS

Comparison of resonance (JLAB) & DIS (SLAC/NMC)

Good agreement in ξ

carbon iron

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A-dependence of Nuclear Effect

Is nuclear effect scaled up with A number?

Carbon and 4He Jlab data results favor density dep. nuclear effect• Need to be careful

about non-iso target correction

4He 12C

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Nuclear Effect in the Deuterium?

Nuclear effect in d can be 4%, extrapolated using nuclear density• Agree with Melinichouk &

Thomas calculation• Consistent with all DIS

with all DIS e/ F2 ,

Tevatron W asym.

Correlated with d/u issue

PRL 1998 Bodek-Yang

Un-ki Yang, Manchester 17

d/u at high x

Large change in d/u at high x due to nuclear effect in d• Larger impact on (d,)• Same conclusion from Thomas

&, Mel. and CTEQ in 1998 Indep. measurements need;

• HERA CC (e-/e+)• Tevatron W asym. at high-

with larger lepton pt cut or LHC?

• Jlab measure of nearly on-shell n by tagging slow p: ed->epX?

Interesting results from NuTeV and E866 DY data: See Morfin’s talk• NuTeV: u+d (higher?)• E866 DY: 4u+d (lower?)

Un-ki Yang, HQL 2008 18

Dedicated efforts to prove d/u at high x from Jlab (reference)

Measure SF of nearly on-shell n by detecting slow spectator p in semi-inclusive ed -> ep X reaction : JLab CLAS++,

BONUS exp. (almost scattering off free nucleon)

Parity violation in DIS on 1H: very sensitive to d/u

€

APV =GFQ

2

2παa(x) + f (y)b(x)[ ]

€

a(x) =u(x) + 0.91d(x)

u(x) + 0.25d(x)

Un-ki Yang, Manchester 19

Summary and Discussions

Effective LO model with ξw describe all DIS and resonance data as well as photo-production data:

• Provide a good reference for (,d)

• With (A)/ (d) from e/, provide (,A), (A)/ (d) for ; any deviation => different nuclear effect (vector vs axial: valence vs sea) in scattering

(A)/ (d) from e/

• Scaling with Nachtman variable, ξ regardless of DIS and resonance

• Favors scaling with nucleon density, instead of A

Need to understand nuclear effect in d or d/u at high x

More Jalb data are coming, and neutrino data are absolutely needed (K2K, SciBooNE, MiniBooNE, and Minerva etc)

Un-ki Yang, Manchester 20

Nuclear effect from Jlab (backup)