Speaker
Dr
Kei Ieki
(University of Tokyo)
Description
The MEG experiment searches for the muon lepton flavor violating
decay, $\mu^+\to e^+\gamma$. An upgrade of the experiment is ongoing,
aiming to reach a sensitivity of Br($\mu^+\to e^+ \gamma$) =
$5\times10^{-14}$, an order of magnitude better than the sensitivity of
the current MEG. To achieve this goal, all of the detectors are being
upgraded.
In MEG, the energy, position and timing of the gamma ray were measured
by a liquid Xe calorimeter, which consists of 900 $l$ of liquid Xe and
846 2-inch round-shaped photo-multiplier tubes (PMTs). In the upgrade,
the granularity at the gamma ray incident face will be improved by
replacing 216 PMTs with 4092 SiPMs (MPPCs) with an active area of
12$\times$12 mm$^2$ each. The energy resolution for the gamma ray is
expected to improve by a factor of 2, because the efficiency to
collect scintillation light will become more uniform. The position
resolution is also expected to improve by a factor of 2.
In collaboration with Hamamatsu Photonics K. K., we have successfully
developed a high performance MPPC for our detector. It has excellent
photon detection efficiency for the liquid xenon scintillation light
in VUV range. The size of the chips is large so that it can cover
large area with a manageable number of readout channels. The
characteristics of the MPPCs are being tested in liquid Xe, and also
at the room temperature. The results of the tests will be presented,
together with the expected performance of the upgraded detector.
Collaboration
MEG-II collaboration
Primary author
Dr
Kei Ieki
(University of Tokyo)
