Speaker
Description
Several efforts have been recently devoted to develop high-resolution timing
detectors for tracking at the High Luminosity LHC experiments while track triggers,
implemented with dedicated hardware, have been used at hadron colliders to select
heavy-flavour decays. In this R&D project we propose to combine the two methods
to develop an innovative detector, based on accurate time and position particle hit
measurements, for 4D tracking and fast track trigger. The precise measurement of
the hits’ time is the key feature to operate an effective pattern recognition that
guarantees a high tracking efficiency while enhancing the ghost track rejection, and
to perform selective track triggering. We ultimately aim to exploit this detector in
flavour physics experiments, in conditions of a high event pile-up, where sensors and
front-end electronics are required to provide a hit time resolution of the order of 20
ps and a hit position resolution better than 40 μm, and are able to continuously
operate in a harsh radiation environment (up to a total flux of 1017 1-MeV neutrons
equivalent per cm2).
State of the art tracking pixel detectors with precise time-tagging show a time
resolution of about 200 ps [1], and we aim to reduce this by one order of magnitude.
Crucial aspects to achieve this ultimate time resolution are the optimization of pixel
sensor geometries (in both 3D and planar technologies) to achieve the most uniform
electric field, and the design of fast and low noise dedicated front-end ASIC. This
front-end will incorporate a fast current amplifier followed by a discriminator and a
time-to-digital converter, and will be developed in 65 nm CMOS technology with
fault tolerant architecture which matches the radiation hardness requirements.
Feasibility studies of a 4D fast track finding system, using hits’ space and time
information, has been recently presented [2] as a possible solution for the low level
track trigger of the HL-LHC experiments. The system is based on a massively parallel
algorithm implemented in commercial FPGAs using a pipelined architecture and
allows a precise real-time determination of the track parameters (including time)
while maintaining a low fraction of reconstructed fake tracks.
The proposed detector will allow to perform flavour physics at LHC while operating
at instantaneous luminosities more than one order of magnitude larger than the
current ones, while guaranteeing large tracking efficiencies and a negligible ghost
tracks rate.
Bibliography
[1] G. Aglieri Rinella et al., “Test-beam results of a silicon pixel detector with Timeover-
Threshold read-out having ultra-precise time resolution”, JINST 10 P12016 2015
[2] Nicola Neri and Marco Petruzzo, “A novel 4d fast track finding system using
precise space and time information of the hit”, arXiv:1512.09008 (2015
Summary
The proposed detector will allow to perform flavour physics at LHC while operating
at instantaneous luminosities more than one order of magnitude larger than the
current ones, while guaranteeing large tracking efficiencies and a negligible ghost
tracks rate.
