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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
Un-ki Yang, Manchester 5
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)
Un-ki Yang, Manchester 7
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
Un-ki Yang, Manchester 14
Nuclear effect in Resonance and DIS
Comparison of resonance (JLAB) & DIS (SLAC/NMC)
Good agreement in ξ
carbon iron
Un-ki Yang, Manchester 15
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
Un-ki Yang, Manchester 16
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)