奇特底夸克共振態之探尋

Abstract

本論文試圖於 Υ(1S)→μ+μ-π+π−衰變途徑中，尋找奇特魅夸克共振態X(3872)的底夸克對應共振態(Xb)。經由分析在質心能量8 TeV條件下，累計亮度20.65/fb的質子--質子對撞事件，在掃描的能量區間10-11 GeV/c^2內並未顯示出任何Xb的存在線索，對應的區域顯著性為2.6個標準差，全域顯著性為0.8個標準差。在95%信心水準下，可以給出在此特定衰變途徑下相對於Υ(2S)的散射截面比值上限為0.8--4.6%(隨Xb的靜止質量變動)。

We report a search for a bottomonium counterpart of exotic charmonium state X(3872), denoted as Xb throughout this thesis. The target decay channel is Xb→Υ(1S)π+π−→μ+μ-π+π−. An integrated luminosity of 20.65/fb at proton-proton collision at sqrt{s}=8 TeV is analyzed. In the search phase space, |y_{Xb}| < 2.0, p_{T,Xb} > 13.5 GeV/c^2, and 10 < M_{Xb} < 11 GeV/c^2, the maximum local significance is 2.6 sigma, which equals to 0.8 sigma global significance. The upper limit at 95% confidence level is settled to be 0.8-4.6% (depend on the mass of Xb) as the cross section of Υ(1S)→Υ(1S)π+π−.