Forward instrumentation for ILC detectors

Abstract

Two special calorimeters are foreseen for the instrumentation of the very forward region of the ILC detector, a luminometer designed to measure the rate of low angle Bhabha scattering events with a precision better than 10 −3 and a low polar angle calorimeter, adjacent to the beam-pipe. The latter will be hit by a large amount of beamstrahlung remnants. The amount and shape of these depositions will allow a fast luminosity estimate and the determination of beam parameters. The sensors of this calorimeter must be radiation hard. Both devices will improve the hermeticity of the detector in the search for new particles. Finely segmented and very compact calorimeters will match the requirements. Due to the high occupancy fast front-end electronics is needed. The design of the calorimeters developed and optimised with Monte Carlo simulations is presented. Sensors and readout electronics ASICs have been designed and prototypes are available. Results on the performance of these major components are summarised.

The International Linear Collider Technical Design Report - Volume 4: Detectors

“…First, there is the so-called LumiCal to measure the luminosity with a precision of better than 10 ≠3 using Bhabha scattering as reference process, e + e ≠ ae e + e ≠ ("). Then there is the BeamCal, positioned adjacent to the beampipe, to provide a bunch-by-bunch luminosity estimate and a determination of the beam parameters [22]. A third calorimeter, GamCal, about 100 m downstream of the detector, will assist in beam-tuning.…”

“…Two special calorimeters are foreseen in the very forward regions of the detector [324], denoted hereafter as LumiCal and BeamCal. LumiCal will measure the luminosity with a precision of better than 10 ≠3 at 500 GeV centre-of-mass energy 1 , and BeamCal will perform a bunch-by-bunch estimate of the luminosity and, supplemented by a pair monitor, assist beam tuning when included in a fast feedback system [325].…”

“…In both calorimeters a robust electron and photon shower measurement is essential, making a small Molière radius preferable. Compact, cylindrical sandwich calorimeters using tungsten absorber disks of one radiation length thickness, interspersed with finely segmented silicon (LumiCal) or GaAs (BeamCal) sensor planes, as sketched in Figure III -3.24, are found to match the requirements [324]. For the innermost part of BeamCal, adjacent to the beam-pipes, also Chemical Vapour Deposition (CVD) diamond sensors are considered.…”

Physics and detector studies with the very forward calorimeters at a future linear collider

“…With the same selection, the fraction of the lost events due to the beamstrahlung and ISR gets reduced ≤ 0.5‰ [4] since this type of isolation cuts prefer events with the smaller energy losses (smaller β coll ). Taking into account other systematic effects as in [12], we prove that the overall uncertainty of the integral luminosity is ≤ 3‰ at ILC energies taking into account simulation dependent corrections and ≤ 5 ‰ if one corrects in a simulation independent manner.…”

Physics potential for the measurement of $${\sigma (H\nu \bar{\nu })\times \text {BR}(H\rightarrow \mu ^+\mu ^-)}$$ σ ( H ν ν ¯ ) × BR ( H → μ + μ - ) at the 1.4 TeV CLIC collider

“…The region between 0.6°and 6.3°is instrumented with the two silicontungsten sampling calorimeters, LumiCal and BeamCal [27], for the luminosity measurement, beam-parameter control, as well as for the tagging of high-energy electrons escaping the main detector at low angles. Together with the very forward segments of the electromagnetic calorimeter covering the polar-angle region between 6.3°and 8°, it is possible to suppress the four-fermion SM background with the characteristic low-angle electron signature.…”