Abstract
The ATLAS Forward Proton (AFP) detector is intended to measure protons scattered at small angles from the ATLAS interaction point. To this end, a combination of 3D Silicon pixel tracking modules and Quartz-Cherenkov time-of-flight (ToF) detectors is installed 210 m away from the interaction point at both sides of ATLAS. Beam tests with an AFP prototype detector combining tracking and timing sub-detectors and a common readout have been performed at the CERN-SPS test-beam facility in November 2014 and September 2015 to complete the system integration and to study the detector performance. The successful tracking-timing integration was demonstrated. Good tracker hit efficiencies above 99.9% at a sensor tilt of 14°, as foreseen for AFP, were observed. Spatial resolutions in the short pixel direction with 50 μm pitch of 5.5 ± 0.5 μm per pixel plane and of 2.8 ± 0.5 μm for the full four-plane tracker at 14° were found, largely surpassing the AFP requirement of 10 μm. The timing detector showed also good hit efficiencies above 99%, and a full-system time resolution of 35±6 ps was found for the ToF prototype detector with two Quartz bars in-line (half the final AFP size) without dedicated optimisation, fulfilling the requirements for initial low-luminosity AFP runs.
Highlights
The ATLAS collaboration [1] at the Large Hadron Collider (LHC) at the European Laboratory for Particle Physics (CERN) is installing the ATLAS Forward Proton (AFP) detector to measure very forward protons (p) scattered at small angles from the ATLAS interaction point (IP) [2]
The common data format of tracking and timing detectors allowed the event-by-event use of track information to predict independently whether a certain L-shaped Cherenkov-radiating Quartz bars (LQbars) was traversed by a particle, which was crucial for the studies of efficiency, cross talk, noise and timeresolution
Beam tests with a first unified AFP prototype detector combining pixel tracking and LQbar ToF sub-detectors and a common readout and data format have been performed at the CERN-Super Proton Synchrotron (SPS) in November 2014 and September 2015
Summary
The ATLAS collaboration [1] at the Large Hadron Collider (LHC) at the European Laboratory for Particle Physics (CERN) is installing the ATLAS Forward Proton (AFP) detector to measure very forward protons (p) scattered at small angles from the ATLAS interaction point (IP) [2] To this end, a combination of high-resolution pixel tracking modules for fractional-energy loss and momentum measurements and fast time-of-flight (ToF) detectors for event pile-up removal is placed at about 210 m from the IP at both sides of ATLAS and only 2–3 mm away from the outgoing Large Hadron Collider (LHC) beam. It is critical to demonstrate that the separate detector components can be operated together as an integrated system To this end, a first unified AFP prototype has been developed, which combines tracking and ToF prototype detectors and a common trigger and readout (excluding the Roman-pot housing at this stage).
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