Pion contamination in the MICE muon beam

Abstract

A: The international Muon Ionization Cooling Experiment (MICE) will perform a systematic investigation of ionization cooling with muon beams of momentum between 140 and 240 MeV/c at the Rutherford Appleton Laboratory ISIS facility. The measurement of ionization cooling in MICE relies on the selection of a pure sample of muons that traverse the experiment. To make this selection, the MICE Muon Beam is designed to deliver a beam of muons with less than ∼1% contamination. To make the final muon selection, MICE employs a particle-identification (PID) system upstream and downstream of the cooling cell. The PID system includes time-of-flight hodoscopes, threshold-Cherenkov counters and calorimetry. The upper limit for the pion contamination measured in this paper is f π < 1.4% at 90% C.L., including systematic uncertainties. Therefore, the MICE Muon Beam is able to meet the stringent pion-contamination requirements of the study of ionization cooling.

MAUS: the MICE analysis user software

“…The MICE Muon Beam line is described in detail in [4]. There are 5 different detector systems present on the beamline: time-of-flight (TOF) scintillators [6], threshold Cherenkov (Ckov) counters [13], scintillating-fiber trackers [14], a sampling calorimeter (KL) [8,9], and the Electron Muon Ranger (EMR) -a totally active scintillating calorimeter [10,11]. The TOF, Ckov, KL and EMR detectors are used for particle identification (PID), and the scintillating-fiber trackers are used to measure position and momentum.…”

“…Individual PMT hits are unpacked from the DAQ or simulated from MC and the reconstruction associates them to identify the slabs that were hit and calculates the charge and charge-product corresponding to each slab hit. The KL has been used successfully to estimate the pion contamination in the MICE muon beamline [9].…”

Results from Mice Step IV

“…The MICE Muon Beamline delivers a high purity beam with less than 1.4 % pion contamination [9]. The flight time between the first two time-of-flight hodoscopes (TOF0 and TOF1) is used to remove other contamination sources such as decay positrons from the final sample.…”

“…A schematic of the experiment in its Step IV configuration is shown in figure 1. The particles produced in the MICE beam line first pass through the upstream particle identification (PID) apparatus, are sampled upstream and downstream of the absorber by scintillating fibre trackers before being dumped in the downstream PID section [7,8,9,10].…”

The reconstruction software for the MICE scintillating fibre trackers

“…MICE is a staged experiment, built and run in distinct steps. The first step of the programme, consisting of the muon beam line with particle identification, is now complete and results are available in [6][7][8][9]. The present step of the program, which introduced the trackers and the first absorber module, began taking data in 2015.…”