b至s夸克變換電荷宇稱不對稱性與極化測量

Abstract

利用運行於Upsilon(4S)共振態之KEKB非對稱正負電子對撞機來製造、並藉由Belle偵測器所收集之兩億七千五百萬B介子對，我們量測了B0->phi K0、K+K-Ks、eta'Ks、omega Ks 等衰變之電荷宇稱(CP)破壞參數。其中一個中性B介子事例被完全重建，隨伴而來的另一B介子被用來鑑定其電荷屬性。CP破壞參數則是依靠雙B介子的原時差分佈測量而得。使用底夸克(b)至奇異(s)夸克轉換相關衰變通道，我們獲得之合併測量值偏離標準模型預測值達2.4個標準差。 我們亦利用B->phi K*衰變，提供衰變振幅以及三重乘積的測量。從末態粒子角度分佈可以測得三種不同極化螺旋態下的衰變振幅。而縱向極化振幅於中性衰變phi K*0被量測為0.45 +- 0.05 +- 0.02, 於非中性衰變phi K*+被量測為0.52 +- 0.08 +- 0.03。我們並未發現相關的CP不對稱性以及時間反轉奇態不對稱性。

We present measurements of CP-violating parameters in B0 -> phi K0, K+K-Ks, eta'Ks, and omegaKs decays based on a sample of 275 x 10^6 BBbar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB energy-asymmetric e+e- collider. One neutral B meson is fully reconstructed in one of the specified decay channels, and the flavor of the accompanying B meson is identified from its decay products. CP-violation parameters for each of the decay modes are obtained from the asymmetries in the distributions of the proper-time intervals between the two B decays. The combined result for decays sensitive to the b->s transition differs from the Standard Model expectation by 2.4 standard deviations. We also provide measurements of decay amplitudes and triple-product correlations in B -> phi K* decays. The decay amplitudes for the three different helicity states are determined from the angular distributions of final state particles. The longitudinal polarization amplitudes are found to be 0.45 +- 0.05 +- 0.02 for B0 -> phi K*0 and 0.52 +- 0.08 +- 0.03 for B+ -> phi K*+ decays. CP- and T-odd CP-violating triple-product asymmetries are measured and found to be consistent with zero.