arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2005.02242physics.ins-dethep-ex
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MEG II跟踪器系统的调试

Commissioning of the MEG II tracker system

M. Chiappini, A. M. Baldini, G. Cavoto, F. Cei, G. Chiarello, A. Corvaglia, M. Francesconi, L. Galli, F. Grancagnolo, M. Grassi, M. Hildebrandt, M. Meucci, A. M… 展开作者

M. Chiappini, A. M. Baldini, G. Cavoto, F. Cei, G. Chiarello, A. Corvaglia, M. Francesconi, L. Galli, F. Grancagnolo, M. Grassi, M. Hildebrandt, M. Meucci, A. Miccoli, D. Nicolò, M. Panareo, A. Papa, F. Raffaelli, F. Renga, P. Schwendimann, G. Signorelli, G. F. Tassielli, C. Voena

摘要:

Paul Scherrer研究所(PSI)的MEG实验代表了研究带电轻子变味(cLFV)$μ^+ \rightarrow e^+ γ$衰变的最新技术水平。在第1阶段,MEG为$\mbox{BR}(μ^+ \rightarrow e^+ γ) < 4.2 \times 10^{-13}$设定了新的世界最佳上限(90% C.L.)。在第二阶段MEG II中,实验的目标是与之前的MEG结果相比,达到大约一个数量级的灵敏度增强。新型圆柱漂移室(CDCH)是MEG II的关键探测器。CDCH是具有高粒度的低质量单体积检测器:9层192个漂移单元,几mm宽,由立体配置中的$\sim 12000$线限定,用于纵向命中定位。填充气体混合物为氦气:异丁烷(90:10)。总辐射长度为$1.5 \times 10^{-3}$ $\mbox{X}_0$,从而使多重库仑散射(MCS)贡献最小化,并允许单击分辨率$< 120$ $μ$ m以及分别为6 mrad和90 keV/c的角和动量分辨率。本文介绍了在INFN莱切的布线阶段和INFN比萨的组装阶段之后,PSI的CDCH调试活动。介绍了端盖的制备、高压试验和真空室的调节,以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$μ^+$束进行的首次数据采集,描述了MEG II实验装置的集成。还示出了第一气体增益结果。所有升级的探测器和完整的DAQ电子设备的完整工程运行预计将于2020年开始,随后是三年的物理数据采集。

英文摘要:

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.

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