AHH00004o - clarification of ocv criteria
Regarding AHH00004o – I have marked the point of convergence of the three white lines at 3 o’clock (in the normal view) as a possible 3 leg ocv. The slice view shows two white lines crossing at 11 o’clock close to the centre, a separate cross a little further out and a cross at 6 o’clock, had I been presented with the slice view alone would have marked all three as possible 2 leg ocvs.
In all of these cases the white lines all fall to one side of a radial line.
Could you clarify whether these points should be marked, specifically,
i) does the fact that the lines fall on the same side of a radial line rule them out (momentum not conserved?)
ii) is there a minimum distance from the centre to qualify as an ocv
Is there a more detailed guide beyond the examples on the opening page? I have found many of the simulation examples in particular to be more complex than those examples and I would find it helpful if a few of these could be marked up to show the ‘real’ answer and with mark up by an expert with an explanation as to why crossing points should be included or excluded.
I'm no expert, but according to what I've seen and read, I may be able to help. Question i : No. There are a lot of particles that aren't shown (low energy) or not detected(nuetral/negative charge). OCVs may appear anywhere. Question ii: As long as there's some visible space between the center (where the green muon lines meet) and the vertex, it's off-center. There may be lines going back toward the center, but if the vertex itself is away from the center, I would mark it.
Another thing I've learned from reading these topics: Don't worry! All data is valuable. Mark it as you see fit.
Sometimes people see different things in the images. In this image, I would probably have marked it the same as you. But, on taking a closer look, I think there's actually 2 OCVs, one of them inside a larger one, the outer one not drawn all the way to a vertex. Some people might mark it that way. (and slice view suggests that, perhaps, this is indeed the case)
A pattern that I've noticed from the obvious ocvs is that when there is a vertex, the particles will move in similar or opposite ways, are often of similar length, and appear as though they are part of the same event. That's one thing I look for in the toughies to spot vertexes. I learn as I go.
Based on what I've seen, I would not mark any ocv here. The thee white lines do not originate from the same place and thus are not a"vertex". Its possible that they could be computer mapped backward tracks but I don't know how to discern that from the data we have.
Hi Turkwise, thanks for the response.
I agree with all you have said. Like you, I generally look for similarities in curvature and your 2 ocv interpretation also seems the best to me as there is a mirrored similarity in the curvature of the two outer white lines even though, as you point out, the image does not show them as quite meeting. I think it’s clear that although my mark up of a three legged ocv might have been legitimate based solely on the normal view, it does not reflect the reality as there is no convergence of three white lines in the slice view.
I would be interested to see if experts, solely reading the normal view would have rejected a three-legged ocv and whether they would mark one, or two, two-legged ocvs. I guess the project expects to collect all of these interpretations but nevertheless I would still like some expert guidance as to which one(s) is/are the best.
Hi lreiswig, thanks for the response.
Although the lines don’t start at the same point, all three seem to cross at a single pixel in the zoom view. My interpretation is that the lines have been extended by the computer, although as I have posted in reply to Turkwise above I have been persuaded that two of them form a vertex and the third just happens to be superimposed through the same point in the normal view.
I think the fact that between the three of us we have arrived at four possible interpretations supports the case for further expert guidance being made available. Both Turkwise and myself are basing our guesses on whether the lines through a point appear to curve in similar ways and maybe have similar lengths although I don’t think there is anything in the existing examples that says we are correct to do so.