Arie Bodek, Univ. of Rochester 1

http://www.aps.org/meet/APR03/baps/abs/S3530011.html [P13.011] Modeling Neutrino Quasi-elastic Cross Sections Using Up to Date Nucleon Form Factors Howard Budd, Arie Bodek (Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627), John Arrington (Argronne National Laboratory, Argonne,

IL)

Arie Bodek, Howard Budd, Univ. of Rochester

and

John ArringtonArgonne National Laboratory

http://www.pas.rochester.edu/~bodek/FormFactors-DPF03.ppt

A Review of Weak and Electromagnetic Form Factors

Arie Bodek, Univ. of Rochester 2

Need to update - Axial Form Factor extraction

• This Talk (What is the difference in the quasi-elastic cross sections if:

1. We use the most recent very precise value of gA = FA (Q2) = 1.263 (instead of 1.23 used in earlier analyses.) Sensitivity to gA and mA,

2. Use the most recent Updated GEP.N (Q2) and GM

P.N ((Q2) from Electron Scattering (instead of the dipole form assumed in earlier analyses) In addition There are new precise measurments of GE

P.N (Q2) Using polarization transfer experiments

3. How much does mA, measured in previous experiments change if current up to date form factors are used instead --- Begin updating mA

e +i k2 . r

e +i k1.r

Mp Mp

Arie Bodek, Univ. of Rochester 3

They implemented

The Llewellyn-Smith

Formalism for NUMI

Non zero

Arie Bodek, Univ. of Rochester 4

Fp important for

Muon neutrinos only at

Very Low Energy

Q2=-q2

UPDATE: Replace by

GEV= GE

P-GEN

gA,MA need to

Be updated

UPATE: Replace by GM

V = GMP-GM

N

From C.H. Llewellyn Smith (SLAC). SLAC-PUB-0958 Phys.Rept.3:261,1972

Arie Bodek, Univ. of Rochester 5

Neutron GMN is negative Neutron (GM

N / GM

N dipole )

At low Q2 Our Ratio to Dipole similar to that nucl-ex/0107016 G. Kubon, et alPhys.Lett. B524 (2002) 26-32

Neutron (GMN

/ GMN

dipole )

Arie Bodek, Univ. of Rochester 6

Neutron GEN is positive New

Polarization data gives Precise non

zero GEN hep-ph/0202183(2002)

Neutron, GEN

is positive -

Imagine N=P+pion cloud

Neutron (GEN

/ GEP

dipole )

Krutov

(GEN)2

show_gen_new.pict

Galster fit Gen

Arie Bodek, Univ. of Rochester 7

Extract Correlated Proton GMP

, GEP

simultaneously from e-p Cross Section Data with and without Polarization Data

Proton GMP

Compare Rosenbluth Cross section Form Factor

Separation Versus new Hall A Polarization

measurements

Proton GEP/GM

P

Proton GMP

/ GMP

-DIPOLE

Arie Bodek, Univ. of Rochester 8

Effect of GMN + (GM

P ,GEP using POLARIZATION data

AND non zero GEN Krutov) - Versus Dipole Form

-> Discrepancy between GEP Cross Section and Polarization

Data Not significant for Neutrino Cross Sections

GMP ,GE

P extracted With

e-p Cross Section data only

GMP ,GE

P extracted with both e-p

Cross section and Polarization data

ratio_JhaKJhaJ_D0DD.pict ratio_JKJJ_D0DD.pict

using cross section data

AND GEN Krutov

Using Polarization Transfer

data AND GEN Krutov

+n->p+-+p->n++

+n->p+-+p->n++

Arie Bodek, Univ. of Rochester 9

quasi-elastic neutrinos on Neutrons-( - Calculated

quasi-elastic Antineutrinos on Protons - Calculated

From H. Budd -U of Rochester (NuInt02) (with Bodek and Arrington) DATA -

FLUX ERRORS ARE 10% With the most

Up to date

Form Factors

The agreement

With data is not

spectacular

Antineutrino datamostly on nuclear targets

Arie Bodek, Univ. of Rochester 10

Reanalysis of

Arie Bodek, Univ. of Rochester 11

Type in their d/dQ2 histogram. Fit with our best

Knowledge of their parameters : Get MA=1.11+-0.05

(A different central value, but they do event likelihood fit

And we do not have their the event, just the histogram.

If we put is best knowledge of form factors, then we get

MA=1.085+-0.05 or MA= -0.025. So all their

Values for MA. should be reduced by 0.025

12Arie Bodek, Univ. of Rochester

Hep-ph/0107088 (2001)

For updated MA expt. need to be reanalyzed with new gA, and GEN

Difference

In Ma between

Electroproduction

And neutrino

Is understoodMA from neutrino expt. No theory corrections needed

1.11=MA

-0.025

Arie Bodek, Univ. of Rochester 13

Using these data we get MA to update to for latest ga+form factors.(note different experiments have different neutrino energySpectra, different fit region, different targets, so each experiment requires its own study).

A Pure Dipole analysis, with ga=1.23 (Shape analysis)

- if redone with best know form factors --> MA = -0.055

(I.e. results need to be reduced by 0.055)

for different experiments can get MA from -0.025 to -0.060

1.Change ga=1.23 to best known ga= 1.267 (shape analysis)

---> MA = + 0.005

2. Dipole-> better Gmn, Gep, Gmp --> MA = -0.025

3. Gen=0-> non zero Gen ---> MA = -0.035

Total -0.055

Arie Bodek, Univ. of Rochester 14

Low-Q2 suppression or Larger MA?T.Ishida’s talk @NuInt01From Ito NuInt02

K2K fits this

With larger

Ma=1.11 instead

Of nominal 1.02

GeV

First result done at NuInt02

Arie Bodek, Univ. of Rochester 15

Effect is Low Q2 suppression from non Zero Gen

Wrong Gen /Best Form Factors (Ratio)

Wrong Ma=1.1 (used by K2K) Over Ma=1.02 (Ratio)

If One Uses Both wrong Form Factors (used in K2K MC)

( Wrong Gen =0 +Wrong Ma=1.1)

Over Best Form Factors (Ratio)

--> Get right shape

But wrong normalization of 10%

ANSWER - Neutrino Community Using Outdated Form Factors

For E=1 GeV