Description
Belle II experiment was successfully started. The first data for physics with full Belle II detector were taken in 2019 and 50ab$^{-1}$ data will be accumulated by 2027. A discussion of an upgrade plan for Belle II and SuperKEKB is started. The instantaneous luminosity by the upgraded SuperKEKB is 5 times larger than current design luminosity for SuperKEKB (8x10$^{35}$cm$^{-2}$s$^{-1}$) and the upgraded Belle II will collect data sample of 250ab$^{-1}$. In such high luminosity environment, current DEPFET pixel detector is hard to operate due to too high occupancy since the readout scheme of DEPFET is rolling shutter mode with a 20$\mu$s frame.
We have invented a new pixel detector concept 'DuTiP' (Dual Timer Pixel) which is a binary pixel detector with a trigger signal based global shutter readout scheme. A binary hit information is stored in a down counting timer inside a pixel whose initial value is set as trigger latency plus 1 clock (around 5$\mu$s). If the trigger signal is recieved when the timer is 1 (0 or 2), the hit information is readout as current (previous or next) timing. To take into account for multiple hits during trigger latency, two timers are equipped in a pixel. The clock speed is important parameter for the occupancy and data size . We tentatively decided the clock speed as 15.9MHz (62.9ns). The requirement of spacial resolution at Belle II is around 10$\mu$m for both z and r-phi directions, thus 35$\mu$m pixel size is selected. This pixel detector can be also used for layer 7 and 8 of ILC vertex detector which requires single bunch (554ns) time stamping capability and moderate spatial resolution of 10$\mu$m in r-phi direction.
We report the concept of 'DuTiP' and the status of development of the pixel detector with an SOI technology for Belle II upgrade.
| Submission declaration | Original and unpublished |
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