Eli PiasetzkyTel Aviv University, Israel

Free neutron structure function

Work done in collaboration with:

L. B. Weinstein (ODU) D. Higinbotham, J. Gomez (JLab) O. Hen, R. Shneor (TAU)

Newport News, VA, USA, April 2011

•No ‘free’ neutron target (life time ~ 12 minutes)

d4He12C56Fe197Au4%22% 20% 14%

The ‘evolution parameter’ is the amount of 2N-SRC in nuclei

The probability to find 2N-SRC in the nucleus

d distribution at large x Uncertainty due to nuclear effects

Adapted from J. F. Owens talk in this conference

d distribution at large x Uncertainty due to nuclear effects

Adapted from J. F. Owens talk in this conference

Toy models for large x

Nucleon Model F2n/F2

p d/u

SU(6) 2/3 1/2

Scalar diquark 1/4 0

pQCD (p↑ q↑) 3/7 1/5

Proton Wavefunction (Spin and Flavor Symmetric)

11

110

)(3

2)(

3

1

)(3

1)(

18

1)(

2

1

SS

SSS

uuduud

uduuduudup

Adapted from J.P. Chen

EMC

Slo

pes

0.3

5 ≤

XB

≤ 0

.7

SRC Scaling factors XB ≥ 1.4

See previous talk by Or HenPhys. Rev. Lett. 106, 052301, 2011

0.079±0.06

Deuteron is not a free np pair

SRC=0 free nucleons

d

He

np

d

3

npd

)/(2 dFea N A

EMC

SRC

bound to free n p pairs (as opposed to bound to deuteron)

The slopes for 0.35 ≤ XB ≤ 0.7

Conclusion:

One should not neglect the EMC effect using deuteron and proton data to extract free neutron properties

Phys. Rev. Lett. 106, 052301, 2011

The free neutron DIS cross section

Gessman, Saito,Thomas,Annu. Rev. Nucl. Part. Sci. 1995. 45:337

M

RFxF

21

12 12

Where is the ratio of cross sections for absorbing a longitudinal to that for a transverse photon.

/ RLR

See talk by Patricia Solvignon

For 0.35 ≤ XB ≤ 0.7

The free neutron structure function

SLAC Data, J. Arrington et al. JPG 36(2009)205005.

Extracted from this work

Fermi smearing using relativistic deuteron momentum density

With medium correction

Phys. Rev. Lett. 106, 052301, 2011

The free neutron structure functionCompared to CT calculations

SLAC Data,

Preliminary calculation by :H. l. Lai, P. Nadolsky, J. Pumplin, .P.Yuan

See talk by Heidi Schellman in this conference

Fh07b / fh02c are CT10 / CT10W like Chebyshev fits

See talk by J.Pumplin in this conference

SU6

pQCD

Scalar qq

Compared to CT calculations

SLAC Data,

Preliminary calculation by :H. l. Lai, P. Nadolsky, J. Pumplin, .P.Yuan

Fh07b / fh02c are CT10 / CT10W like Chebyshev fits

See talk by J.Pumplin in this conference

SU6

pQCD

Scalar qq

The d / u ratio

Summary We employ a phenomenological procedure to extract the free F2

n/F2p structure function ratio from proton and deuteron DIS.

At large Bjorken x, we obtain a substantially different F2n/F2

p ratio compared to using the standard smearing model to account for the Fermi motion of the nucleons in the deuteron.

Better agreement with W charge and W lepton asymmetries.

Narrow uncertainties in PDFs at large x due tonuclear effects in deuteron structure function. Sharpen theoretical understanding of nuclear modifications of nucleons in nuclei.

arXiv:1003.4497 [hep-ph]

Phys. Rev. Lett. 106, 052301, 2011