ϒ(2S)衰變至希格斯粒子之探尋

Abstract

本篇論文為尋找輕質量希格斯波色子(A0 )的存在證據。實 驗地點位於日本高能加速機構,使用了158百萬個Υ(2S)。根據 次最小超對稱模型(NMSSM)的預測,輕質量希格斯波色子可藉 由衰變通道: Υ(2S) → γA0 以及 Υ(2S) → Υ(1S)π + π − ; Υ(1S) → γA0 產生。我們的研究包括 A0 → μ+ μ− 和 A0 → τ + τ − 的結果。 由於並未找到輕質量希格斯波色子的存在證據,我們給予90%信 心水準的衰變機率乘積的上限: B(Υ(2S) → γA0 ) × B(A0 → μ+ μ− ) = (0.02 − 3.11) × 10−6 in the mass range 0.214 ≤ mA0 ≤ 9.00 B(Υ(2S) → γA0 ) × B(A0 → τ + τ − ) = (1.22 − 16.46) × 10−5 in the mass range 3.59 ≤ ma0 ≤ 9.19 B(Υ(1S) → γA0 ) × B(A0 → μ+ μ− ) = (0.005 − 3.54) × 10−6 in the mass range 0.212 ≤ mA0 ≤ 9.0 B(Υ(1S) → γA0 ) × B(A0 → τ + τ − ) = (5.06 − 64.68) × 10−5 in the mass range 3.59 ≤ mA0 ≤ 9.16

We report search for a light Higgs boson (A0 ) using 158 mil lion Υ(2S) events collected with the Belle detector in the KEKB e+ − e− collider. The Higgs boson is identified in the decays Υ(2S) → γA0 and Υ(2S) → Υ(1S)π + π − , Υ(1S) → γA0 . Results from both A0 → μ+ μ− and A0 → τ + τ − decays are presented. We did not find evidence for the existence of A0 , the 90% C.L. upper limit on the product of braching fractions is given: B(Υ(2S) → γA0 ) × B(A0 → μ+ μ− ) = (0.02 − 3.11) × 10−6 in the mass range 0.214 ≤ mA0 ≤ 9.00 B(Υ(2S) → γA0 ) × B(A0 → τ + τ − ) = (1.22 − 16.46) × 10−5 in the mass range 3.59 ≤ ma0 ≤ 9.19 B(Υ(1S) → γA0 ) × B(A0 → μ+ μ− ) = (0.005 − 3.54) × 10−6 in the mass range 0.212 ≤ mA0 ≤ 9.0 B(Υ(1S) → γA0 ) × B(A0 → τ + τ − ) = (5.06 − 64.68) × 10−5 in the mass range 3.59 ≤ mA0 ≤ 9.16