Pion/Muon separation
1: Threshold Pressures

Diagram showing the \v{C}erenkov pressure thresholds for particles of various momenta using CO$_{2}$. The areas above each line are the regions of space where the particle is above the triggering threshold of the \v{c}erenkov detectors. When the beam is set to select particles of say 3 GeV, it can be seen that at 2 atm, muons will fire the detector and pions will not.

2: Raw Events at 1.8 GeV

Plots of particle range for events selected by the \v{c}erenkov counters at 1.8 GeV. Top Left: events that fired both \v{c}erenkovs; these are muons, but a significant amount of contamination from PS muons is seen. Top Right: events that fired neither \v{c}erenkov counter. Bottom Left: events that fired the first counter but not the third. Bottom Right: events that fired the third counter but not the first.

3: Raw Events at 2.0 GeV

Plots of particle range for events selected by the \v{c}erenkov counters at 2.0 GeV with fits to the peaks. Top Left: events that fired both \v{c}erenkovs. Top Right: events that fired neither \v{c}erenkov counter. Bottom Left: events that fired the first counter but not the third. Bottom Right: events that fired the third counter but not the first.

4:

Range verses \v{c}erenkov adc for events that fired the first counter (left) and the third counter (right). Low range, high deposition events are electrons, long ranged events are muons. The high concentration of events with a range of 60 are caused by PS muons. Note the significant number of events where the adc is zero.

5:
The effect of the fiducial cut and low range cuts is to produce a cleaner beam muon selection. PS muons and electrons are shown in red and beam muons in blue. A fit is made to the cleaned sample.

MuonEnergy kov1Efficiency kov3Efficiency
1.8 74% 89%
2.0 88% 90%

5:

Range verses \beta for muons and pions. The distance that a muon travels through the detector is proportional to its energy. This is not the case for pions. Below plane 40, muons and pions have the same beta and so cannot be distinguished by the \v{c}erenkovs.

6:

The efficiency of the \v{c}erenkov detectors on a plane-by-plane basis. Below plane 50 the efficiency is poor.

7:

1/1-$\beta^{2}$ verses the number of photoelectrons. The x-intercept of a straight line fit should give a minimum below which muons are not travelling fast enough to trigger the \v{c}erenkov counters.

8:

cov one chi squared to get best fit

9:

cov three chi squared to get best fit

10:

Straight line fit to 1/1-$\beta^{2}$ verses the number of photoelectrons, for counter one. $\beta$(0) is the threshold velocity, p($\pi$) is the momentum required by a pion to fire the \v{c}erenkov, p($\mu$ is the momentum required by a muon to fire the \v{c}erenkov and Range($\mu$) is the nominal range of a muon at the threhold velocity.

11:


12:

The distribution of muon momenta at 1.8 GeV, showing the 1.65 and 1.77 Gev muon cut-off points. At a higher pressure, significantly more muons are seen in one \v{c}erenkov than another.

13:

Corrected plane-by-plane efficiencies

14:

Corrected range plots. Top Left: Events that fired both \v{c}erenkov detectors. Top Right: Events that fired neither \v{c}erenkovs. Bottom Left: Events that fired only the first \v{c}erenkov. Bottom Right: Events that fired only the third \v{c}erenkov.

15:

Corrected range plots. The original data is shown in blue, the correction in red and the final result in black. The description of the various plots is the same as the previous plot.

Measurement of Muon dE/dX 16:

The energy spectra distributions for all hit strips are truncated at 90%.

17:

Average energy deposition on a plane-by-plane basis. 1.8 and 2.0 GeV data is shown.

18:

dE/dX using the number of planes from the track end. 1.8 and 2.0 GeV data are overlaid. A bethe-bloch fit to the data is then applied.

19:

Residuals from the bethe-bloch fit.