Studying Mechanism Of High Energy Proton-Proton Elastic Scattering In QCD

Proton-proton elastic scattering at high energies is an important issue in understanding of QCD - the fundamental theory of strong interaction and in searching for new physics. The process is a purely diffractive process since no quantum numbers exchange between the two colliding particles. It is a common belief that the Pomeron exchange is responsible for this diffractive process. However,the origin and nature of the Pomeron is still unknown. There is no any theoretical argument for the existence of the Pomeron. The Pomeron is hypothetical object. No physical particle or resonance lies on its Regge trajectory ap(t) = 1.08 + 0.20/ ,which was required by fitting high energies experimental data. With the development of Quantum Chromodynamics(QCD),people started to investigate the origin and nature of the Pomeron from QCD viewpoint. For very high energy,the proton-proton scattering is a short range. Phenomena where the proton-proton interaction takes place through the interaction between the constituent quarks inside the projectile and target proton by exchanging gluon which is a mediator of strong interaction described by QCD. It is natural to suppose that Pomeron exchange is just the exchange of several gluons,at least two,and these gluons couple to a same single quark. For high energy process,the quark-gluon degrees of freedom predominately show up,since it is a short distance phenomenon. Therefore,we can study these short distance phenomena by use of multigluon exchange among the quarks,which carries quantum numbers of vacuum. In QCD description,PP elastic scattering is a gluon exchange process. In the other words,PP elastic scattering is a high energy multiple scattering of two quark-composite system. Therefore,one can describe proton-proton elastic scattering by quark multiple scattering theory,such as Glauber theory,although this mechanism cannot have vacuum quantum numbers requested by experiments. Consideration of the role of gluon degrees of freedom in PP elastic scattering are based on the more recent developments in high energy physics,we believe that the Pomeron used in high energy diffractive process could be a tensor glueball (2230) with quantum numbers of = 0+2 ++ ,since the two gluons could be bounded together to form a glueball due to gluon self-interaction.. In this article the Pomeron exchange theory,multigluon exchange theory,tensor glueball exchange theory and multiple scattering of quarks in the two different protons theory are elaborated. The role of gluon degrees of freedom inside two protons is stressed. For high energy proton-proton elastic scattering,the cross section has been calculated from exchanging Pomeron theory,such asThese calculations have been performed for differential cross section at the energy of = 53GeV and the total cross section,for differential cross section,below the momentum transform and for total cross section at s > 10 the Pomeron exchange theory reproduce the experimental data very well. Considering that it may be a Reggeon exchange process at lower energy,we modified the total cross section,and the theoretcal prediction fit the experimental data better.For tensor glueball exchange theory,we get the differntial cross section and total cross section from the decay width of experimental data. The theoretical prediction fit the experimental data very well.For high energy proton-proton multiple scattering,we get the scattering matrix element for singe gluon exchange.From these calculations,we find that both the predictions fit the experimental data well. Therefore,the results support the idea that the Pomeron could be a tensor glueball with quantum numbers of IGJPC = 0+2++ .