论文标题
MEG II跟踪器系统的调试
Commissioning of the MEG II tracker system
论文作者
论文摘要
Paul Scherrer Institut（PSI）的MEG实验代表了寻找违反带电的Lepton风味（CLFV）$μ^+ \ rightArrow E^+γ$衰减的最新状态。使用阶段1，MEG将新世界最佳上限设置在$ \ mbox {br}（μ^+ \ rightarrow e^+γ）<4.2 \ times 10^{ - 13} $（90％c.l.）。与先前的MEG结果相比，借助第2阶段的MEG II，该实验旨在达到敏感性提高约一个数量级。新的圆柱漂移室（CDCH）是MEG II的关键检测器。 CDCH是一种低质量单量检测器，具有高粒度：9层的192个漂移电池，几乎没有毫米宽，由$ \ sim 12000 $的电线定义为立体声构型，用于纵向命中的定位。填充气体混合物是氦气：异丁烷（90:10）。总辐射长度为$ 1.5 \ times 10^{ - 3} $ $ \ mbox {x} _0 $，从而最大程度地减少了多个库仑散射（MCS）贡献，并允许单击分辨率$ <120 $ $ $ $ m $ m，并分别为6 mrad和90 kev/c/c/c kev/c。本文在INFN LECCE的接线阶段和INFN PISA的装配阶段介绍了PSI的CDCH调试活动。描述了腔室的末端准备，HV测试和调节室的旨在达到最终的稳定工作点。鉴于在2018年和2019年工程运行期间，使用宇宙射线和$μ^+$ beam的第一批数据进行了描述。还显示了第一个气体增益结果。完整的工程运行，所有升级的检测器和完整的DAQ电子设备预计将于2020年开始，然后进行三年的物理数据。
The MEG experiment at the Paul Scherrer Institut (PSI) represents the state of the art in the search for the charged Lepton Flavour Violating (cLFV) $μ^+ \rightarrow e^+ γ$ decay. With the phase 1, MEG set the new world best upper limit on the $\mbox{BR}(μ^+ \rightarrow e^+ γ) < 4.2 \times 10^{-13}$ (90% C.L.). With the phase 2, MEG II, the experiment aims at reaching a sensitivity enhancement of about one order of magnitude compared to the previous MEG result. The new Cylindrical Drift CHamber (CDCH) is a key detector for MEG II. CDCH is a low-mass single volume detector with high granularity: 9 layers of 192 drift cells, few mm wide, defined by $\sim 12000$ wires in a stereo configuration for longitudinal hit localization. The filling gas mixture is Helium:Isobutane (90:10). The total radiation length is $1.5 \times 10^{-3}$ $\mbox{X}_0$, thus minimizing the Multiple Coulomb Scattering (MCS) contribution and allowing for a single-hit resolution $< 120$ $μ$m and an angular and momentum resolutions of 6 mrad and 90 keV/c respectively. This article presents the CDCH commissioning activities at PSI after the wiring phase at INFN Lecce and the assembly phase at INFN Pisa. The endcaps preparation, HV tests and conditioning of the chamber are described, aiming at reaching the final stable working point. The integration into the MEG II experimental apparatus is described, in view of the first data taking with cosmic rays and $μ^+$ beam during the 2018 and 2019 engineering runs. The first gas gain results are also shown. A full engineering run with all the upgraded detectors and the complete DAQ electronics is expected to start in 2020, followed by three years of physics data taking.
