MINOS

lp is truth and lpt is tracked. I wasn't expecting this! I thought that crosstalk hits must be getting tracked by accident but this would have the reverse effect.

The discrepancy is mainly being caused by events in the high-energy tail.
So either the tracker is somehow losing hits at the end of the track...
Or maybe photons produced at the end of the track are getting removed as crosstalk. I was hoping that photons are largely 'track-like' in location and appearance and not 'crosstalk-like'. The crosstalk energy cut is very lax at the moment, so I shouldn't be calling any photons crosstalk just because they deposit low energy.

Mon Jun 09 Update...

So here might be part of the reason....

Those two blue hits at the end of the track (plane 46 & 50) are NOT crosstalk hits - they are genuine parts of the track!

This muon seems to slow down a lot just before it stops and curves off to the left going along the gap between planes and consequently hitting a strip quite a way off to the left.

So the tracker doesn't really think this is a track hit because it's too far away from the main track and hence outside the search window.

The hit spectra for Plane 39 strip 15 and Plane 3 strip 12. Only tracked hits are used.

Zoom of above graphs ( 0 -> 3 pe )

Even closer up with finer binning. You can see that ~10% of hits are below 1 pe.

Crosstalk hits only. The mean looks a bit low to me... Maybe I picked two bad locations.

This is plane 9 strip 1, a location that receives a lot of crosstalk hits from the central track core ( ~strips 11-13 )
I was expecting more higher energy crosstalk hits here but I guess it seems reasonable. Have to double check with Mike that optical as well as electrical crosstalk is implemented in the monte carlo.

Latest Truth/Tracked De/Dx plot. Things look a bit better.

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Final de/dx comparison between tracked and truth

If you ignore >plane52, the comparison is good to 1%

plane>=54 -> 0.32%

Some photons skip a number of planes ( N.B. Jun25 - not photons, photocathode noise! )

A strange hit appears after the track

The hit does not appear here: It has a HitBit of zero!

Data - there is a peak at plane 20 in lph, presumably PS muons and other such oddities. They distort the dedx profile seen here. Also could do with more statistics.

********************** Overexuberant Tracking! 1/4

The top plot is tracked. The bottom is truth, weighted by HitBit. A red HitBit means crosstalk. The last two hits in the second and third views turn out to be crosstalk!

HitBit breakdown (normal scale)

HitBit breakdown (as above) on logarithmic x scale. Note: 30 events have HitBit=0!

Table: comparison of tracked to truth
Plane No.	MC Tracked	MC Truth	Ratio	Comment
19	9802	9868	1.007	Typical plane
48	6163	6267	1.017	Lph mean here
49	4208	4332	1.03
50	2267	2357	1.04
51	881	931	1.058
52	236	289	1.22
53	73	104	1.42
54	23	40	1.74
55	6	25	4.15
56	3	24	8
57	0	12	-
58	0	12	-
59	0	6	-
60	0	6	-

This is Truth. Look at the last view: the last hit is a photon which has jumped 4 planes! Luckily the tracker doesn't call this part of the track... but I'm starting to wonder exactly how I should treat things like this.

We have now established that HitBits=0 is noise...

Shouldn't it be evenly distributed in the detector?
OK, so Ryan rightly points out that if there are any hits on a pmt, then by definition the HitBit can't be zero so this plot is biased against planes that see lots of hits...
However, if this is the case, wouldn't we expect to see the number of noise hits increasing after lph max? And certainly not decreasing from plane 56 as this appears to do.

The same thing for photocathode noise...

This seems correlated with hits. Should I be removing this (like noise) or handling it, maybe even attempting to fold it back ( a la crosstalk )

To be fair, these plots are of *only* photocathode noise. In fact, the majority of hits are some summation of real hit, crosstalk and noise. I assume that the *only* photocathode noise hits are some random sub-set of this. I haven't decided yet whether this is true or not or whether I'm introducing a bias.

This is the distribution of *only* crosstalk in the detector.

Tracked dedx

Truth dedx

You can see that for the most part there is overwhelming agreement. There are a few extraneous hits in the truth just up to plane 60: these are caused by (photocathode) noise that doesn't get tracked. A bit more energy is seen in the tracked in the high energy dip after the lph mean. This is caused by crosstalk hits close to the track being included in the track. This should decrease when the crosstalk hits are folded back into tracks in both tracked and truth.