2009.1.10 at KEK FNAL ドレルヤン実験 E906 による陽子のクォーク・反クォーク構造の研究柴田利明東工大日本：東工大、理研、KEK、京大アメリカ、台湾 1 2 陽子の中のsea quark のフレーバー非対称性の起源をさぐる。 u (x)  d (x) Gottfried Sum Rule SG   1 0  F p 2 ( x )  F2n ( x )/ x dx   e q 1 0 2 i p i ( x )  qip ( x )  qin ( x )  qin ( x )dx i 1 1     ei2 2qip ( x )  2qin ( x )dx 3 0 i 1 2 1    u ( x )  d ( x ) dx 3 3 0   Valence quark の積分は2 (u) 1 (d) 3 NMCによる「Gottfried和則の破れ」（NMC,1991) Gottfried和則の破れ－陽子中では反ｄクォークの方が反uクォークより多いことを示している。･ The Gottfried sum from the ratio F2(n) / F2(p) P. Amaudruz et al., Phys.Rev.Lett.66: 2712-2715, 1991 ･ A Reevaluation of the Gottfried sum M. Arneodo et al., Phys.Rev.D50:1-3,1994 Eμ＝90, 280 GeV 0.004 < x < 0.5 SG=0.258 ± 0.017 < 0.333 4 5 Eμ＝90, 280 GeV SG=0.258 ± 0.017 < 0.333 6 Drell-Yan Process E906 Drell-Yan Experiment at FNAL 2010 年スタート 7 陽子ビーム: FNAL Main Injector Ep = 120 GeV ビーム強度：ビームスピル中 2x1012/s, 合計陽子ビーム数： 5.2x1018、標的：液体水素、液体重水素、原子核（C,Fe,W）、ドレル・ヤン過程の仮想光子質量の領域： 4.2－8.8 GeV 8 Earlier Drell-Yan experiments 800 GeV σ ∝ 1/s 9 J. C. Peng et al. [E866/NuSea Collaboration], “anti-d/anti-u asymmetry and the origin of the nucleon sea”, Phys. Rev. D 58, 092004 (1998), [E866] PRL 80 (1998) 3715 10 11 How u is suppressed compared to d in the Proton? u u  dd Meson Cloud ? Chiral Solitons ? u u ud Instantons ? d ud Proton 12 13 14 Sumamry ･ Drell-Yan process has a well defined kinematics. It enables us to determine the Bjorken x event by event. ・ We are preparing an Experiment E906 at FNAL with 120 GeV proton beam to study the flavor asymmetry of antiquarks in the nucleon. ・ Cross section ratios between p-p, p-d reactions will be measured. ・ It will reach higher x region than the earlier experiments. ・ In unpolarized Drell-Yan process, correlation between transverse quark momentum and quark spin can be studied: Boer-Mulders Function ・ Nuclear targets will also be used to study the nuclear medium effect in Drell-Yan process 15