ScienceAsia 27 (2001) : 251-259 |doi: 10.2306/scienceasia1513-1874.2001.27.251

NN Scattering and Nucleon Quark Core

Y Yan^a,* and R Tegen^b

ABSTRACT: We review here nucleon-nucleon elastic and charge exchange scattering with special emphasis on the quark hard core inside the nucleon. It is found that total cross sections are sensitive only to the total hadronic size of the proton, which has two components, the quark core and the surrounding meson cloud. At higher energies differential cross sections are found to reveal, for larger -t, a hard core size of order ~ 0.3 fm. We present model calculations for unpolarized cross sections and find that a meson exchange model with QCD vertex functions reflecting the quark/antiquark structure of the nucleon is well capable of reproducing existing data. A quark core size of order 0.3 fm is found in our model and a preference for certain meson exchanges. As expected the pion exchange supplemented with , , ₀, ₂, a₂ dominates the t-dependence of the elastic cross sections while isovector exchanges , , a₂ with a background field dominate the charge exchange n-p reaction.

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a School of Physics, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand.
b Permanent address: Nuclear and Particle Theory Group, Physics Department, University of the Witwatersrand, P.O. WITS, Johannesburg 2050, South Africa.
e-mail: tegen@physnet,phys, wits.ac.za

* Corresponding author, E-mail: yupeng@ccs.sut.ac.th

Received 8 Feb 2000, Accepted 25 May 2001