Accuracy of the geometric-mean method for determining spatial resolutions of tracking detectors in the presence of multiple Coulomb scattering

Abstract

The geometric-mean method is often used to estimate the spatial resolution of a position-sensitive detector probed by tracks. It calculates the resolution solely from measured track data without using a detailed tracking simulation and without considering multiple Coulomb scattering effects. Two separate linear track fits are performed on the same data, one excluding and the other including the hit from the probed detector. The geometric mean of the widths of the corresponding exclusive and inclusive residual distributions for the probed detector is then taken as a measure of the intrinsic spatial resolution of the probed detector: σ = √ σ ex · σ in . The validity of this method is examined for a range of resolutions with a stand-alone Geant4 Monte Carlo simulation that specifically takes multiple Coulomb scattering in the tracking detector materials into account. Using simulated as well as actual tracking data from a representative beam test scenario, we find that the geometric-mean method gives systematically inaccurate spatial resolution results. Good resolutions are estimated as poor and vice versa. The more the resolutions of reference detectors and probed detector differ, the larger the systematic bias. An attempt to correct this inaccuracy by statistically subtracting multiple-scattering effects from geometric-mean results leads to resolutions that are typically too optimistic by 10-50%. This supports an earlier critique of this method based on simulation studies that did not take multiple scattering into account.

ATHENA detector proposal — a totally hermetic electron nucleus apparatus proposed for IP6 at the Electron-Ion Collider

“…In general, MPGDs are gaseous devices for electron amplification with a high granularity strip or pad anode readout to provide good 2-D space point resolution (< 100 μm), fast signals (∼ 10 ns), high rate capability (up to 1 MHz cm −2 ), low material budget, radiation hardness and large area coverage. Through the EIC generic detector R&D program (eRD3/eRD6 [11][12][13][14][15][16][17][18][19][20][21][22]) advancements towards low material and large-area MPGD detectors with low channel counts and high granularity readout structures have been made. Each Micromegas layer in the barrel and each of the forward/backward triple-GEM disks has a material thickness well below 1% 𝑋/𝑋 0 .…”

Snowmass 2021 Instrumentation Frontier (IF5 - MPGDs) -- White Paper 2: Micro Pattern Gaseous Detectors for Nuclear Physics

“…In January 2011, Brookhaven National Laboratory (BNL), in association with Jefferson Lab and the DOE Office of Nuclear Physics established a generic detector R&D program [3] to address the requirements for measurements at the EIC. From this program, the eRD3 and eRD6 projects were formed to focus on EIC compatible MPGD detectors, whose efforts have contributed greatly towards realizing high-resolution, large-area, and low-mass tracking detectors [4,5,6,7,8,9,10,11,12,13,14]. Current experiments such as Jefferson Lab's Super Bigbite Spectrometer (SBS) and CLAS12 experiments have already benefitted from this R&D work.…”

“…Some sub-detectors may not necessitate the use of FEPs, such as MAPS, as these may interface directly to switches, servers or link exchange modules (e.g., FELIX). The FEPs make extensive use of FPGAs for data processing, providing an opportunity to decrease the available output data bandwidth requirements by a factor of ten (10). This can be accomplished by various methods or algorithms, such as zero suppression or via ML and AI filtering.…”

ATHENA Detector Proposal -- A Totally Hermetic Electron Nucleus Apparatus proposed for IP6 at the Electron-Ion Collider

“…In general, MPGDs are gaseous devices for electron amplification with a high granularity strip or pad anode readout to provide good 2-D space point resolution (< 100 𝜇m), fast signals (∼ 10 ns), high rate capability (up to 1 MHz cm −2 ), low material budget, radiation hardness and large area coverage. Through the EIC generic detector R&D program (eRD3/eRD6 [11][12][13][14][15][16][17][18][19][20][21][22]) advancements towards low material and large-area MPGD detectors with low channel counts and high granularity readout structures have been made. Each Micromegas layer in the barrel and each of the forward/backward triple-GEM disks has a material thickness well below 1% 𝑋/𝑋 0 .…”