First particle-by-particle measurement of emittance in the Muon Ionization Cooling Experiment


Published in: Eur. Phys. J. C (2019) 79:257
RAL Preprint: RAL-P-2018-005


The Muon Ionization Cooling Experiment (MICE) collaboration seeks to demonstrate the feasibility of ionization cooling, the technique by which it is proposed to cool the muon beam at a future neutrino factory or muon collider. The emittance is measured from an ensemble of muons assembled from those that pass through the experiment. A pure muon ensemble is selected using a particleidentification system that can reject efficiently both pions and electrons. The position and momentum of each muon are measured using a high-precision scintillating-fibre tracker in a 4T solenoidal magnetic field. This paper presents the techniques used to reconstruct the phase-space distributions in the upstream tracking detector and reports the first particle-by-particle measurement of the emittance of the MICE Muon Beam as a function of muon-beam momentum.


MICE note: Note 498

Citation: BibTeX
References: inSPIRE


Figure 1. Schematic diagram of the MICE experiment. The red rectangles represent the coils of the spectrometer solenoids and focus-coil module. The individual coils of the spectrometer solenoids are labelled E1, C, E2, M1 and M2. The various detectors (time-of-flight hodoscopes (TOF0, TOF1), Cherenkov counters, scintillating-fibre trackers, KLOE-Light (KL) calorimeter, and Electron Muon Ranger (EMR)) are also represented. The Partial Return Yoke (PRY) is not shown. (PDF, jpg)

Figure 2. a Top and b side views of the MICE Muon Beam line, its instrumentation, and the experimental configuration. A titanium target dipped into the ISIS proton synchrotron and the resultant spill of particles was captured with a quadrupole triplet (Q1–3) and transported through momentum-selecting dipoles (D1,D2). The quadrupole triplets (Q4–6, Q7–9) transported particles to the upstream spectrometer module. The time-of-flight of particles, measured between TOF0 and TOF1, was used for particle identification. (PDF, jpg)

Figure 3. Distribution of the quantities that were used to select the sample used to reconstruct the emittance of the beam: a) the number of spacepoints in TOF0 plotted against the number of space-points in TOF1 for reconstructed data, and b) reconstructed simulation; c) distribution of the relative time-of-flight, trel; d) distribution of χ2/NDOF; and e distribution of Rdiff. The 1D distributions show reconstructed data as solid (black) circles and reconstructed MAUS simulation as the solid (yellow) histogram. The solid (black) lines indicate the position of the cuts made on these quantities. Events enter these plots if all cuts other than the cut under examination are passed. (PDF, jpg)

Figure 4. Time of flight between TOF0 and TOF1 (t01) plotted as a function of the muon momentum, p, measured in the upstream tracker. All cuts other than the muon hypothesis have been applied. Particles within the black lines are selected. The white dotted line is the trajectory of a muon that loses the most probable momentum (20MeV/c) between TOF1 and the tracker in a reconstructed data, and b reconstructed Monte Carlo. (PDF, jpg)

Figure 5. Position and momentum distributions of muons reconstructed at the reference surface of the upstream tracker: a) x, b) y, c) px, d) py, e) pz, and f) p, the total momentum. The data are shown as the solid circles while the results of the MAUS simulation are shown as the yellow histogram. (PDF, jpg)

Figure 6. Transverse phase space occupied by selected muons transported through the MICE Muon Beam line to the reference plane of the upstream tracker. a) (x, px), b) (x, py). c) (y, px), d (y, py). e) (x, y), and f (px, py). (PDF, jpg)

Figure 7. The effect of dispersion, the dependence of the components of transverse phase space on the momentum, p, is shown at the reference surface of the upstream tracker: a) (x, p); b) (px , p); c) (y, p); d) (py , p). (PDF, jpg)

Figure 8. The systematic bias and uncertainty on the reconstructed emittance under different magnetic field model assumptions. The bias estimate (open triangles) includes the non-uniformity bias (open squares). The variation between the models (see text) is indicated by the shaded bands. (PDF, jpg)

Figure 9. Normalised transverse emittance as a function of total momentum, p, for data (black, filled circle) and reconstructed MonteCarlo (red, open triangle). The inner error bars show the statistical uncertainty. The outer error bars show the quadratic sum of the statistical and systematic uncertainties. (PDF, jpg)


Table 1. The number of particles that pass each selection criterion. A total of 24660 particles pass all of the cuts. (PDF, jpg, LaTeX)

Table 2. The number of reconstructed electrons, muons, and pions at the upstream tracker that survive each cut in the Monte Carlo simulation. Application of all cuts removes almost all positrons and pions in the re constructed Monte Carlo sample. A total of 253 504 particles pass all of the described cuts in the Monte Carlo simulation. (PDF, jpg, LaTeX)

Table 3. Emittance together with the statistical and systematic uncertainties and biases as a function of mean total momentum, <p>. (PDF, jpg, LaTeX)

Updated by Long, Kenneth almost 5 years ago · 77 revisions