北京頻譜合作團隊於2003 年透過北京電子正子對撞機首次在J/ψ介子衰變成1顆光子、1 顆質子與1 顆反質子之事件中由2 顆質子衰變模式重建的質量分布上大約1.859 GeV/c^2質量單位的位置發現1 個未知且接近數據邊界的訊號，第3代北京頻譜合作團隊(Beijing Spectrometer III)與CLEO合作組織的結果被認為這一結構是由X(1835)導致，但結果依然有爭議。某些理論指出X(1835)可能為一種質子與反質子的束縛態（Protonium）。因此，在該質量區間研究反質子氫可能將會為探索新物理提供一條途徑。這項研究將演示利用位於相對論性重離子對撞機(RHIC)上的STAR 探測器於質心能量為200 GeV 的2018年Zr+Zr和Ru+Ru粒子對撞數據中尋找來自J/ψ → e^+e^-X(p￣p)事件的X(1835)衰變為2顆質子的進展。

The Beijing Spectrometer (BES) collaboration first discovered an unknown near threshold signal at about 1.859 GeV/c^2 in the mass distribution for the 2 protons decay mode in J/ψ decaying to one photon, one proton, and one antiproton in the Beijing Electron–Positron Collider during 2003. The results from Beijing Spectrometer III (BESIII) and CLEO collaborations suggested this structure as X(1835), however, the results are still controversial. Some theories indicated that X(1835) might be a pp bound state (Antiprotonic hydrogen). Therefore, studying the antiprotonic hydrogen in this mass region might provide a way to explore new physics. This study will present the progress of the search for X(1835) decaying to 2 protons in J/ψ decaying to e^+e^-X(p￣p) channel using the Zr+Zr and Ru+Ru collisions at 200 GeV data collected in 2018 by the STAR detector at the Relativistic Heavy Ion Collider (RHIC).

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