Laboratoire d'Annecy-le-Vieux de Physique des Particules (LAPP), Université de Savoie, CNRS/IN2P3, F-74941 Annecy-Le-Vieux, France.
Phys Rev Lett. 2009 Dec 18;103(25):251801. doi: 10.1103/PhysRevLett.103.251801. Epub 2009 Dec 16.
We search for invisible decays of the Upsilon(1S) meson using a sample of 91.4 x 10(6) Upsilon(3S) mesons collected at the BABAR/PEP-II B factory. We select events containing the decay Upsilon(3S) --> pi(+)pi(-)Upsilon(1S) and search for evidence of an undetectable Upsilon(1S) decay recoiling against the dipion system. We set an upper limit on the branching fraction B(Upsilon(1S) --> invisible) < 3.0 x 10(-4) at the 90% confidence level.
我们使用在 BABAR/PEP-II B 工厂收集的 91.4 x 10(6)个Upsilon(3S)介子样本,寻找 Upsilon(1S)介子的不可见衰变。我们选择包含衰变 Upsilon(3S) --> pi(+)pi(-)Upsilon(1S)的事件,并寻找与双介子系统反冲的不可检测 Upsilon(1S)衰变的证据。我们在 90%置信水平下将 Upsilon(1S) --> 不可见分支比 B(Upsilon(1S) --> 不可见)设置为 < 3.0 x 10(-4)的上限。