Sigma meson cloud and Proton’s light flavor sea quarks. Peking University, China ( 北京大学 ) Feng Huang ( 黄 峰） Supervisor: Bo-Qiang Ma （马伯强）. outline. Introduction Meson cloud model Adding sigma meson in this model Summary. Introduction. Gottfried sum rule (GSR)
Peking University, China (北京大学)
Feng Huang (黄 峰）
Supervisor: Bo-Qiang Ma （马伯强）
Meson cloud model
(directly including mesons)
Lattice gauge approach
Instanton induced interaction
Chiral quark soliton model
(not directly including mesons)Explanations for this asymmetry
the splitting function is
with the splitting function convolution
In a full calculation, we should include all kinds of mesons and baryons. While the probability of baryon-meson fluctuation should decrease with the invariant mass of the baryon-meson Fock state increasing, we can neglect the effects of Fock states with higherinvariant mass
Pion, the lightest meson, plays the dominant role. Difference between u_bar and d_bar in virtual pion clouds can provide the large lightflavor asymmetry in proton naturally
The dominant role is played by the pion, while itprovides the ratio either increases monotonically with x or turns back towards unity too slowly.
(M. Alberg, E. M. Henley, Nucl. Phys. A663 (2000) 301)
(M. Alberg, E. M. Henley, G. A. Miller, Phys. Lett. B471 (2000) 396)
Comparison of a harder bare nucleon sea quarks (thick solid line) with a traditional bare sea quarks (dashed line) .
The thin solid line is only Pi contribution to the ratio
a) isoscalar scalar meson
b) chiral partner of Pi
c) not well established in experiment
We assume the valence and sea quark distribution of mesons related here are the same.
Our calculations illustrate that the larger value of tends to give small values of the ratio and decreasing causes the maximum value of the ratio to be large and to appear at higher value of x