Gottfried Sum from the Ratio ( 比に よる Gottfried の 和則の 検証 )

1. Gottfried Sum from the Ratio ( 比によるGottfriedの和則の検証) P. Amaudruz et al., New Muon Collaboration Phys. Rev. Lett. 66(1991)2712 [Contents] Introduction Deep inelastic scattering Experiment Results Summary Shibata lab. Ogoshi Shun

2. 1. Introduction Valence Quarks and Sea Quarksin the Proton ・Valence Quarks u : up quark d : down quark determine the quantum number (Baryon number, charge, isospin…) ・Sea Quarks quark-antiquark pair generated from gluon dissociation (, , …) u gluon u d proton Are sea quarks flavor symmetric or asymmetric ? q

3. 2. Deep inelastic scattering Lepton Beam (electron , muon) p p’ P is a Lorentz invariant mass, total hadron mass after scattering. Elastic Scattering ( ) Inelastic Scattering ( ) : Bjorken scaling variable

4. Structure Function(構造関数) Structure Functionin the partonmodel Structure Functionin the proton Structure Functionin the neutron

5. IsospinSymmetry between proton and neutron Gottfried Sum If sea quarks areflavor symmetric,

6. 3. Experiment NMC at CERN ( Deep inelastic scattering ) 90 or 280 GeV The method of determining the value of (1) (2) (3) From the world data 6 Measured

7. 4. Results Fig.2 Fig.1 7 Measured x region

8. Extrapolation to Extrapolation to is different from ! Sea quarks are flavor–asymmetric. There is more than in the proton.

9. 5. Summary ・ Gottfried sum is under assumption of parton model and isospinsymmetry between a proton and a neutron. ・ Experiment is adeep inelastic muon scattering on and in NMC at CERN. ・ The experimental results shows ・ Extrapolation to x=0(x=1) ・ The value for the Gottfried sum estimated in this experiment is ・A flavor asymmetric sea is a likely explanation. There is more than in the proton. 9

10. 以下、補足スライド

11. Flavor-asymmetric sea There is more than in the proton. Neutron u, d, d Proton u, u, d Pion u,