Abstract
The particle flux increase (pile-up) at the HL-LHC with luminosities of L = 7.5 × 1034 cm−2 s−1 will have a significant impact on the reconstruction of the ATLAS detector and on the performance of the trigger. The forward region and the end-cap where the internal tracker has poorer longitudinal track impact parameter resolution, and where the liquid argon calorimeter has coarser granularity, will be significantly affected. A High Granularity Time Detector (HGTD) is proposed to be installed in front of the LAr end-cap calorimeter for the mitigation of the pileup effect, as well as measurement of luminosity. It will have coverage of 2.4 to 4.0 from the pseudo-rapidity range. Two dual-sided silicon sensor layers will provide accurate timing information for minimum-ionizing particles with a resolution better than 30 ps per track (before irradiation), for assigning each particle to the correct vertex. The readout cells are about 1.3 mm × 1.3 mm in size, which leads to a high granular detector with 3 million channels. The technology of low-gain avalanche detectors (LGAD) with sufficient gain was chosen to achieve the required high signal-to-noise ratio. A dedicated ASIC is under development with some prototypes already submitted and evaluated. The requirements and general specifications of the HGTD will be maintained and discussed. R&D campaigns on the LGAD are carried out to study the sensors, the related ASICs and the radiation hardness. Both laboratory and test beam results will be presented.
Highlights
The HL-LHC [1] is an upgrade of the LHC project, which will deliver an integrated luminosity of up to 4 000 fb−1 over the subsequent decade, and achieve an instantaneous luminosity of L = 7.5x1034 cm−2s−1, compared to the current value of L = 2.5x1034 cm−2s−1
The timing information of the High Granularity Time Detector (HGTD) [3] reduces the density of vertices for a given track, and allows the effective separation of the hard scatter vertex from pile-up vertices surrounding it in the Z direction, the improvement of the ATLAS [4] performance in the forward region
The signals of the trigger were combined in the Trigger Logic Unit (TLU), whose output was used by the telescope and connected to the oscilloscope, ensuring a perfect match between the events recorded by the telescope and the oscilloscope(s)
Summary
The HL-LHC [1] is an upgrade of the LHC project, which will deliver an integrated luminosity of up to 4 000 fb−1 over the subsequent decade, and achieve an instantaneous luminosity of L = 7.5x1034 cm−2s−1, compared to the current value of L = 2.5x1034 cm−2s−1 This will increase the pileup interactions to an average of 200 simultaneous proton-proton interaction within the same bunch crossing interval (< μ > = 200),which is 6 times higher than the current pileup rate. The timing information of the HGTD [3] reduces the density of vertices for a given track, and allows the effective separation of the hard scatter vertex from pile-up vertices surrounding it in the Z direction, the improvement of the ATLAS [4] performance in the forward region
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