Monday 26th Feb, MICE meeting room, 14:00 GMT
Scattering note: MCSNote.pdf
- Still discussing the analysis not the wording
- Some of the wording was not consistent with plots
- Tackle table/plots first
- Add PID/contamination to systematic uncertainty
- "Total" uses PDG RMS formula and adds in quadrature for each of the materials. Should change to use the sum of the radiation lengths
- Legend is too small; it is (blue) G4 (green) Moliere (red) Cobb
- Should add error bars; consider enhancing statistical sample to make error bars negligible. Chase JHC if JN needs to know bin content/etc to do the calculation.
- Ensure that the Geant4 beam is monoenergetic and axial (don't use a realistic beam or anything). Note beam impurities were already rejected. This is like a "theory" section/discussion.
- Add to the text that models are consistent.
- Note the TOF2 column is number of digit coincidences
- John N should fix the caption; TOF1 is the triggering detector, so TOF2 "triggers" is wrong word.
- Should make comment quantitative
- Should use column density, not volume density
- Comment relates to theory, not to measurement; correct text
- "Spell out" the X_0 calculation
- Decide what the paragraph is trying to say
- Comparison is for sum of momentum settings; should make a comparison on a "setting-by-setting" basis
- Note discrepancy between MC and data in Fig.2a. We don't think it is significant; consider making a comparison of scattering with left hand side of the beam vs right hand side of the beam to determine whether position distribution can contribute to uncertainties/etc.
- Mark \Delta z on the Fig. 3; some dimensions (numbers) would be useful.
- r_0 should be 140 mm not 150 mm.
- Diffuser cut should be between "Upstream track selection" and "TOF timing selection"
- Caption should be changed; more than just 240 MeV/c. Remove "and simulation". Clarify what each row means relative to the previous row.
- Write "overflow bin" rather than 45^degrees in the fiducial cut row.
- Move up towards beginning; e.g. section 1.3
- More dimensions; definition of axes; Lithium Hydride absorber; consider which detectors/etc to include; remove coils
- Discuss why we separate x and y; noting that the tracker mixes x and y but the beamline magnets do treat x and y independently (and deliver interesting correlations accordingly). Should present the logic later on.
- Note that fit line is not used.
- Should check that the uncertainties in the efficiencies are correctly taken into account.
- Should add plot with theta and theta^2
- Should enhance statistical sample in MC
- Needs units
- Note that the electron peak is shifted by 200 ps; concern that there may be impact on momentum validation
- We were confused about what was shown; this is the (x^2+y^2)^0.5 as defined in Table 3 line 4; it seems like a harsh cut. The normalisation is unclear and should be clarified.
- Should explain what an "event" is? What cuts are switched on?
- The "12 mrad" scatter should be described as applying to the absorber and applied at the absorber; and should be 24 mrad
- Nb: it's plotted at the upstream edge of the diffuser; clarify
- Should explain what "track acceptance" is
- Clarify what does RMS really mean? What do the +/- values mean? There is a measurement error and a bin width.
- What z-position do the momentum measurements refer to
- Discuss; how should the momentum bins be presented? Answer: we should just list each bin from the start
- It is worth making more of the momentum measurement; study of different contributions to resolution and their significance (e.g. straggling, TOF resolution, path length discrepancy can all contribute to resolution).
- Note it is a placeholder; more work needed
- Fit could/should use eqn 14
- Note tracks outside the tracker fiducial volume; add a cut rejecting events outside the tracker fiducial volume
- Describe the z-position of the track - where in TKU is this plotted
- Note change of slope at 30 mrad; could be tied to the features of the tracker acceptance fig. 4 (stats/behaviour gets different around 30 mrad; enhanced stats may help)
- Need error bars in Fig. 14b
- Add theta y plots
- Check tracker alignment is correct; speak to Durga and Francois
- Since making the plot, John N discovered that the deconvolution had not yet converged. Work continues
- Add description of the RooUnfold deconvolution algorithm
- Add chi2 and KS test between red and blue plot
- Expect 0.003/0.694 = 0.2 % uncertainty in density; => 0.1 % uncertainty in X_0; how does this tie to the 10^-6 quoted?
- Density is not the interesting value; it is column density (how much material per unit area?); fix.
Note that there can be a systematic bias due to no momentum loss in the (empty) absorber; which produces a different scattering effect in TKD compared to full absorberFig. 17
- This seems a fairly significant effect
- It should be treated as a systematic; that becomes of order the dominant systematic
- Hence worth chasing
- What is normalised residuals? Clarify.
- Why does Moliere not agree better with CC.
Eqn 22 - why not just use the analytical formula?
- Add Geant4 result
- Check effect of "2.61 mrad bin" vs Cobb-Carlisle bin size
- Has the rebinning had an effect?
- Use John Cobb MC binning
- Eq 13 - check expression
Tab. 10/Fig. 19/Fig. 18
Comment:- as it stands, we are claiming an asymmetry in the MCS distribution with large statistical significance. This is clearly not physical and needs to be addressed.
- Check horizontal error bars; what is being plotted? Should be the RMS width of the momentum distribution (not the error on the mean, which has an additional factor of 1/sqrt(N))