Higgs Hunters Talk
Very interesting one - and in real data. Possibily an interaction with the (grey) slicon detector layer?
Interesting...
FrostBite: yes that's possible. Here there are hits in the muon chambers at about 11 oclock, probably caused by #punchthrough
Computer has still missed most of the tracks for the #ocv at 7 oclock. 😦
May be "beam halo" http://atlas.ch/photos/events-beam-halo.html - meaning particles swept along with the LHC beam.
There's #energy around (yellow blobs in green calorimeter layer) but very few tracks. This is typical of #photon production.
The red dashed lines indicate the direction of momentum imbalance in the collision. It can be an indication of #invisible particles.
The white zones are places where lots of energy has supposedly been found ("jets"). There are an unusually large number of them here.
The fish-eye view we use gives more space to the (small) central part of the detector than to the (big) outer muon detectors (blue).
Hi emor3j, see #oval in the Object FAQ
Possibility 1: the particles are scattering from material in the calorimeter. Possibility 2: the "fish-eye" view distorts them at the edge.
It may be that we're unlucky and they just appear to be ocv because of the 2-d perspective of the 3-d images. This is why we have slice!
This looks like a "beam halo" particle. Charged particles can be carried along parallel to the LHC beam (horizontal, central in slice)
I cant quite tell where this blip is from the description - what colour is it?
Either a particle bounced off some material in the detector, or it's a join-the-dots error in the track-finding algorithm.
Coloured lines are ones that the computer thinks have come from an off-center vertex. But it's not always right.
After some discussion we have an idea. It might be something known as punch-through. I'll put a post on this in the Physics section.
Beautiful example!
Possibly the particle scattered off part of the detector and changed direction.
The ovals are the computer's guess at where #ocv might be. This looks like a bad guess to me. In any case, ignore them!
More than one collision can happen at the same time, at different points along the beam pipe. Slice suggests that there are several here.
The track-finding algorithm has stretched these two tracks right out to the other side of the detector. Unlikely that's where they started!
This one is a real #mess. On a messy image like this one, feel free only to mark places where three or more tracks come together.
For single lines not intersecting there's no need to leave a mark.
The rectangles at the edge show the centers of energy deposits in the detector (little yellow blobs in the shaded regions.)
Neutral particles don't make any lines. This looks like a photon: http://hypatia.phys.uoa.gr/Simplified_Basics/img/atlaslayers.jpg
The yellow rectangle shows there's energy in this area (detected as yellow blobs in the green "calorimeter" layer).
It's a #toughie - narrow track-angles. On zoom I see an interesting #ocv at about 4 o'clock with orange, white and green lines.
Looks to me like the green lines (which are #muon tracks) come from near the center - but the WHITE lines may be #ocv tracks.
Who turned the beam off? 😉
Yes, that should be marked as a 2-particle vertex.
Yep, I agree!
This is a #toughie. In slice view there's a track starting inside the detector, almost parallel to the beam pipe. Beam-related artifact?
You can tell that the green tracks are #muon tracks because they pass right through the outer part of the detector.
A #twostage decay. On zoom, the computer has picked up the blue tracks from the second decay, but not the white ones from the first.
Two look like they come from the center, with the third just a random single-track artifact.
Stray white lines are probably cosmic rays or reconstruction artifacts.
This is really odd, both in normal view and slice. It looks like a jet of muons. #muonjet. How very very odd...
Odd single tracks can happen when stray particles from the LHC beam, or from cosmic rays traverse the detector.
The different colours indicate that the computer has assigned two different vertices, but I agree they look like one single vertex event.
Interesting. The true path of the original out-going particle probably was probably between the two tracks near the center.
I agree. With the narrow angle between the tracks this is a #toughie.
Yes, I agree. Interesting image!
Beautiful example of two off-center vertices!
This one looks a bit better in the slice view, but it's a real mess. I don't think I could beat the computer here!
Wow - this looks like a really tough one. Just have to do our best here!
I agree this is a hard one. The blue lines show tracks the algorithm has selected for an #OCV. I think it has missed one at 11 oclock.
These blue ovals are the computer's suggestions for off-center vertices. In this case they don't look like particularly great suggestions!
Yes, that's normal - charged particles curve in the magnetic field of the detector.
Agreed - that's a prime #OCV.
Curious. That's worth marking as a weird one.
The track with multiple crossings looks like an artifact. But there's a nice #OCV at about ten o'clock, not far from the center.
Spectacular! I'm adding that one to a collection...
There's definitely something at 11 oclock. One to mark for sure!
That's a good one. I can see a good vertex at about 9 oclock and another (messier) one at about 11 oclock. Nice in slice too!
Good spot. Yes, I can see two interesting off-center vertices here: at 5 oclock and 10 oclock.
No need to mark it as "unusual" though - we expect it when the collisions make neutrinos, which are (almost completely) invisible.
The dashed red line is an indication that the event was "unbalanced". It may be that some invisible particle was produced which wasnt seen.
There should be a very small chance of getting the same (not just a similar) image twice in a row. If you see this happening , let us know.
If there's doubt, go ahead and mark any good overlaps.
We're most interested to find the place from which the tracks have first crossed. That means the overlap closest to the center.
Yes in this case you can maybe just about make it out in the slice view!
Yes, I would put a "weird" mark at the point where the track bends.
This is a muon particle, perhaps kicked out of the jet of energy that's next-door. That would indicate it was a heavy-quark-initiated jet.
Possibly the particle has collided with the calorimeter, lost energy and been deflected (red circular layer).
Definitely something interesting going on to the bottom right of the center, where the different coloured tracks come together.
Very interesting one - and in real data. Possibily an interaction with the (grey) slicon detector layer?
Interesting...
FrostBite: yes that's possible. Here there are hits in the muon chambers at about 11 oclock, probably caused by #punchthrough
Computer has still missed most of the tracks for the #ocv at 7 oclock. 😦
May be "beam halo" http://atlas.ch/photos/events-beam-halo.html - meaning particles swept along with the LHC beam.
There's #energy around (yellow blobs in green calorimeter layer) but very few tracks. This is typical of #photon production.
The red dashed lines indicate the direction of momentum imbalance in the collision. It can be an indication of #invisible particles.
The white zones are places where lots of energy has supposedly been found ("jets"). There are an unusually large number of them here.
The fish-eye view we use gives more space to the (small) central part of the detector than to the (big) outer muon detectors (blue).
Hi emor3j, see #oval in the Object FAQ
Possibility 1: the particles are scattering from material in the calorimeter.
Possibility 2: the "fish-eye" view distorts them at the edge.
It may be that we're unlucky and they just appear to be ocv because of the 2-d perspective of the 3-d images. This is why we have slice!
This looks like a "beam halo" particle. Charged particles can be carried along parallel to the LHC beam (horizontal, central in slice)
I cant quite tell where this blip is from the description - what colour is it?
Either a particle bounced off some material in the detector, or it's a join-the-dots error in the track-finding algorithm.
Coloured lines are ones that the computer thinks have come from an off-center vertex. But it's not always right.
After some discussion we have an idea. It might be something known as punch-through. I'll put a post on this in the Physics section.
Beautiful example!
Possibly the particle scattered off part of the detector and changed direction.
The ovals are the computer's guess at where #ocv might be. This looks like a bad guess to me. In any case, ignore them!
More than one collision can happen at the same time, at different points along the beam pipe. Slice suggests that there are several here.
The track-finding algorithm has stretched these two tracks right out to the other side of the detector. Unlikely that's where they started!
This one is a real #mess. On a messy image like this one, feel free only to mark places where three or more tracks come together.
For single lines not intersecting there's no need to leave a mark.
The rectangles at the edge show the centers of energy deposits in the detector (little yellow blobs in the shaded regions.)
Neutral particles don't make any lines. This looks like a photon:
http://hypatia.phys.uoa.gr/Simplified_Basics/img/atlaslayers.jpg
The yellow rectangle shows there's energy in this area (detected as yellow blobs in the green "calorimeter" layer).
It's a #toughie - narrow track-angles. On zoom I see an interesting #ocv at about 4 o'clock with orange, white and green lines.
Looks to me like the green lines (which are #muon tracks) come from near the center - but the WHITE lines may be #ocv tracks.
Who turned the beam off? 😉
Yes, that should be marked as a 2-particle vertex.
Yep, I agree!
This is a #toughie. In slice view there's a track starting inside the detector, almost parallel to the beam pipe. Beam-related artifact?
You can tell that the green tracks are #muon tracks because they pass right through the outer part of the detector.
A #twostage decay. On zoom, the computer has picked up the blue tracks from the second decay, but not the white ones from the first.
Two look like they come from the center, with the third just a random single-track artifact.
Stray white lines are probably cosmic rays or reconstruction artifacts.
This is really odd, both in normal view and slice. It looks like a jet of muons. #muonjet. How very very odd...
Odd single tracks can happen when stray particles from the LHC beam, or from cosmic rays traverse the detector.
The different colours indicate that the computer has assigned two different vertices, but I agree they look like one single vertex event.
Interesting. The true path of the original out-going particle probably was probably between the two tracks near the center.
I agree. With the narrow angle between the tracks this is a #toughie.
Yes, I agree. Interesting image!
Beautiful example of two off-center vertices!
This one looks a bit better in the slice view, but it's a real mess. I don't think I could beat the computer here!
Wow - this looks like a really tough one. Just have to do our best here!
I agree this is a hard one. The blue lines show tracks the algorithm has selected for an #OCV. I think it has missed one at 11 oclock.
These blue ovals are the computer's suggestions for off-center vertices. In this case they don't look like particularly great suggestions!
Yes, that's normal - charged particles curve in the magnetic field of the detector.
Agreed - that's a prime #OCV.
Curious. That's worth marking as a weird one.
The track with multiple crossings looks like an artifact. But there's a nice #OCV at about ten o'clock, not far from the center.
Spectacular! I'm adding that one to a collection...
There's definitely something at 11 oclock. One to mark for sure!
That's a good one. I can see a good vertex at about 9 oclock and another (messier) one at about 11 oclock. Nice in slice too!
Good spot. Yes, I can see two interesting off-center vertices here: at 5 oclock and 10 oclock.
No need to mark it as "unusual" though - we expect it when the collisions make neutrinos, which are (almost completely) invisible.
The dashed red line is an indication that the event was "unbalanced". It may be that some invisible particle was produced which wasnt seen.
There should be a very small chance of getting the same (not just a similar) image twice in a row. If you see this happening , let us know.
If there's doubt, go ahead and mark any good overlaps.
We're most interested to find the place from which the tracks have first crossed. That means the overlap closest to the center.
Yes in this case you can maybe just about make it out in the slice view!
Yes, I would put a "weird" mark at the point where the track bends.
This is a muon particle, perhaps kicked out of the jet of energy that's next-door. That would indicate it was a heavy-quark-initiated jet.
Possibly the particle has collided with the calorimeter, lost energy and been deflected (red circular layer).
Definitely something interesting going on to the bottom right of the center, where the different coloured tracks come together.