PDD - Time Resolution
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6 Experimental Requirements- 6.1 Time Resolution
- 6.2 Waveforms
- 6.3 Dynamic Range and Linearity
- 6.4 Absolute Amplitude Calibration and Stability
- 6.5 Dead time
- 6.6 Sensitivity of optical modules
- 6.7 Noise Rate and Noise Rate Stability
- 6.8 Failure Rate
- 6.9 IceTop
6.1 Time Resolution
From operation and Monte Carlo simulations of the AMANDA detector we have learned that event rates and angular resolution of atmospheric neutrinos, as well as the efficiency for rejecting the background of atmospheric muons, do not depend on the accuracy of time calibration (t0) and on time resolution (σt) provided they do not exceed 10 ns. Deterioration of the detector performance becomes apparent only above 15 ns because below this scale scattering in the bulk ice is the dominant effect. For the higher energy PeV–EeV neutrino signals in IceCube, the requirement may even be looser because the average distances over which photons are collected are increased and so are the effects of scattering. For electromagnetic showers, waveform digitization will be important, but a timing accuracy similar to the one required for muon tracks should be adequate.
A resolution of ≤ 5 ns is a well-motivated requirement. Better resolution results in better performance in rare cases. For instance, science requiring low thresholds, or the detection of short muon tracks very close to strings, may benefit from better time resolution because the effect of scattering is suppressed. Examples are the detection of neutrinos from the annihilation of dark matter particles in the center of the Earth (producing short, nearly vertical muons) and the detection of oscillating beams from an accelerator at a northern site. One may also be able to argue for improved time resolution on the basis of better reconstruction of the direction of electromagnetic showers induced by electron-neutrinos, or to separate close showers from the production and decay of tau-neutrinos (double bang events). One should keep in mind that time resolution is ultimately limited by the PMT at 1–2 ns for multi-PE signals.
