Higgs Hunter lines
-
is it normal to get one line with different colors.
Is it normal that the lines present a curvature?
ThanksPosted
-
Science team I'm not getting any younger, any answer? Even we don't have the slightest idea?
Posted
-
This is dry and boring and I doubt you will make science in this desert.
Posted
-
by
DZM
admin
@lovethetropics, the science team is not a 24/7 help line or an instant-chat! 😃 This project is brand new and is still growing. The team will be checking back to answer questions, I'm sure.
Posted
-
by
andy.haas
scientist
in response to Lovethetropics's comment.
Hi! The colors indicate when the computer thinks tracks belong to the same vertex. But you should mostly ignore them and count the vertex tracks yourself, no matter the color.
The curvature is because the detector is in a (solenoidal) magnetic field and the particles are electrically charged. The higher the particle momentum, the less the curvature. This is how we measure particle energies.
Thanks for the great questions!Posted
-
by
Rob
Is there a chance to be able to magnify some of the images to count the tracks. I find some s close together that I'm not sure if it is 1,2 or 3.
CheersPosted
-
by
andy.haas
scientist
If you make it a "favorite", or discuss it in talk, you can zoom in and see other views. For the sake of consistency of users that don't do a careful time of zooming, etc., we don't make this functionality the default during classification.
Posted
-
by
Rob
Thanks! But it is difficult to complete some classifications as the tracks are so close together.
Posted
-
by
DZM
admin
Even the normal zoom-in tricks (command and +, for instance) don't seem to work. I guess the science team really doesn't want us zooming in on the classification interface. Okay!
Posted
-
by
Rob
Guess your right. I do like to be accurate though, especially if I am expected to count things.
Posted
-
by
dbuck53
Often lines will start, cross each other somewhere along the central section then depart each other. I have been counting these, but should I? Also if a line has originated at one vertex already, I have not been counting it where it crosses another. Is this correct. Thanks
Posted
-
by
andy.haas
scientist
Right on both! Thanks!
Posted
-
by
MWPALMER
@andy.haas, thanks for the explanation of the colors! But there are some colors that seem to behave differently - especially green lines and red dashed lines. They must mean something different from a computer guess as to what shares vertices. What are these?
Another question: As I understand it, the visible tracks are estimated based on imperfect data, and sometimes little segments protrude on the 'wrong' side of the vertex because of overzealous extrapolation by the computer. Correct? If so, is this an attribute of both normal and slice views?Posted
-
by
andy.haas
scientist
in response to MWPALMER's comment.
Right. Muons are always drawn as green lines. (Sometimes normal tracks are also green, if they are grouped together on a green vertex, sorry. But the muons extend beyond the tracker into the calorimeters and muon system.) There are almost always 2 muons in each event, since we've selected the events to have a Z boson decay to 2 muons!
The red dashed line is the direction of the missing transverse momentum. The momentum of the proton collision is ~0 in the directions transverse to the proton beams. Thus the final particles should also add to ~0 momentum in these directions. (Conservation of momentum!) But it never does add to 0, since particles are slightly mismeasured and there can also be invisible particles, like neutrinos, or new particles like dark matter. The red dashed line shows which direction the missing particle(s) are headed in.
Yes, if the tracks are not grouped onto a vertex by the computer, they are drawn starting from the point closest to 0,0, the center of the detector (near the collision point). This is true for all views, though it's most obvious in the normal/zoom views.
Posted
-
by
MWPALMER
in response to andy.haas's comment.
Thanks!
Posted
-
by
Mark_..._a_physicist_of_sorts
Are yellow lines photons? I thought so, until I saw some curved lines. Surely a photon cannot be made to curve in a B field?
Posted
-
by
peterwatkins
scientist
in response to Mark ... a physicist of sorts's comment.
The lines are all due to charged particles (not photons) whatever their colour
Posted
-
by
DZM
admin
Thanks to the scientists for some excellent info on the colors. I've alerted @jokergirl to this and another thread, and she's going to update the FAQs!
Posted
-
by
MWPALMER
What are the blue bars in the muon detector ring? And what are the opaque white boxes that tend to appear on the rim when there are a lot of trajectories?
Posted
-
by
undefined
source: http://talk.higgshunters.org/#/boards/BHH0000001/discussions/DHH000024iby andy.haas scientist
red = muon
blue = jet from bottom quark
yellow = photon
green = electron (?)
Posted
-
by
brownfox
The white boxes. I think, from what Professor Haas said, they mark the boundaries used to calculate the energy of a jet of particles. For something like a quark, which is subject to the strong force, it will generate a jet of particles rather than two or three and the easiest way to work out what caused the jet is to add up the total energy.
Posted
-
by
Mark_..._a_physicist_of_sorts
in response to undefined's comment.
There's some debate over colours here @mwpalmer has photons yellow, whereas @peterwatkins says they're all charged particles, so none are photons ....
Posted
-
by
brownfox
My understanding: photons don't leave tracks (of any colour) in the inner detector but should be marked with yellow squares around the muon detector.
Posted
-
by
jokergirl
moderator
Correct. Photons (and other uncharged particles) don't leave tracks. They do leave energy readings in the green calorimeter. Supposedly yellow rectangles on the outside near the muon detector are also energy level measurements for photons, but I'm not sure about that.
😉
Posted
-
by
MWPALMER
in response to undefined's comment.
Thanks for this repost!
Posted
-
by
peterwatkins
scientist
in response to jokergirl's comment.
You are right to say that photons do give signals in the inner (green) calorimeter but they do not not usually reach the outer calorimeter near the muon chambers. Other neutral particles such as neutrons usually deposit energy in both calorimeters before being stopped.
Posted
-
by
markbakovic
please excuse gravedig, I think this and other threads could use a complete disambiguation, collated from various partial explanations around the discussion forum; correct errors where necessary:
(all in reference to Normal view)
straight green line running centre to edge, with red marker on outside end?
- muon track (can be bent at outside edge when computer gets confused, usually 2 per event), high energy
other line of any colour, even green, yellow etc., usually slightly curved but not always?
- charged particle of any sort in inner detector (including other muons)
lines that start waaay off centre and cross the detector in a very non-radial way?
-particles not from the beam collision (usually muons from cosmic rays, possibly also particles entrained by the beam (beam halo) or in the other parts of the collider cooling system etc.), sometimes just computer error.very curly lines?
-particles with low energy/mass, so not enough momentum to escape the detector's magnetic fieldgreen and red detector rings?
- calorimeters: green interacts primarily via the electromagnetic force, so all charged particles and photons, red interacts via the strong nuclear force as well, which allows it to detect neutral charge hadrons*
yellow rectangles of various sizes in the green and red rings?
- indicate energy deposition in that cell of the relevant calorimeter: bigger rectangle = more energy. They are yellow for contrast, and are always yellow, the colour doesn't indicate particle identity by itsself, that is indicated by the pattern of energy deposits^
red dashed line?
-not a particle track per se, the direction of missingenergymomentum: might be a neutrino, might represent the average of lots of them. might be dark matter etc. etc. Could also just be measurement error 😃(everybody's favourite)
blocks of colour around the edge?
-computer generated indicator: not a signal in the muon detector, not another calorimeter, but the result of computer processing to indicate likely pattern matches in the data (ie it's a guess by the computer based on criteria the scientists define depending on what they want to look for) as follows:red block?
-muon detector hits of sufficient pattern to establish a plausible track to the collision area,and intensity to indicate high energy muons(which is why the green lines lead to them)yellow block?
-photon trajectory indicated by green calorimeter hits of the right intensity without corresponding track or red calorimeter hits (see £ though)green block?
-electron trajectory indicated by green calorimeter hits of the right intensity with corresponding track but no red calorimeter hits (see £ though)blue block?
-"b-jet" or "b-tagged jet" or similar: it indicates a possible bottom quark by analysis of multiple tracks and calorimeter hits, remember that a lot of the tracks in question will be hidden in our views as they are [either] not energetic enough individually [or aren't ocv candidates because they start directly at the collision point], and also that it's only "likely", not "certain"white shaded sectors over the green and red rings?
-also an indicator; in this case more generally number and intensity of calorimeter hits. Dr. Andy says it means "lots of energy" which I interpret (perhaps incorrectly) to mean it's an indicator of a jet other than a b-jet. Hadron colliders produce lots of quarks, not just bottom ones.The problem the science team likely faces with all our questions of "what does x mean?" is how much to tell us, given that most of the background, to most of the answers, to most of these questions is pretty arcane, even by the standards of "other science", and sure some of you know a thing or two about quarks, leptons, SUSY and prime bosons, but plenty of us don't: interest does not equal necessary background understanding and at the end of the day, we're here to spot V-shapes in pictures 😃 I say this as one of the "interested beyond my education", and offer these explanations not as one who knows, but one who has collected from various sources 😃 Read on for a few extended gleanings that might be of interest if, like me, you wouldn't mind a little more detail on a few of the above points. A little 😃
£ I base this directly on comments by Dr. Andy (cited earlier in this thread) although I've never seen a green block on here. The Atlantis visualisation software for ATLAS that I've seen assigns yellow blocks as indicators for both photons and electrons by default, but that setting is freely configurable.
*this is a slightly simplified version of how the calorimeters work, but its easiest to think of the inner calorimeter as detecting charged particles, pretty much stopping light ones like electrons and photons, leaving only hadrons (protons, neutrons, various mesons) to hit the outer calorimeter. Non-hadrons can still interact with the "hadronic calorimeter" (eg.
tau leptons, muons), and vice versa, but the ratio of interactions points toward what sort of particle it is.^eg lots of yellow in the green ring but none in the red one in line with a track pointing at it in the inner detector is likely an electron, without the track it's more likely a photon, the energy amount (which we don't see) can indicate the likelihood of these cases. Notice there are several layers of cells in the calorimeters, which allow assessment of whether the particle has expended all of its energy inside the calorimeter or continued on through it with energy left over: this alone can point the way to identification, as particles like electrons and photons are unlikely to make it though the green calorimeter, and most hadrons get stopped in the red one, which is how their total momentum can be measured, even if they're electrically neutral (and thus don't leave tracks whose curvature in the inner detector can be assessed)...
...although the "T" in "ATLAS" stands for "toroidal" I haven't yet found a convincing explanation for what that ginormous 2-4T field in the muon detectors should do to the muons, other than just deflect them at 90 degrees to their deflection by the field inside the inner detector. Why? [this]More accurate momentum measurement?
or is it just a cosmic ray shield??[this post has been edited in light of comments (see below) but I've left original text "struck through" etc. so those comments make sense]
Posted
-
by
brownfox
in response to markbakovic's comment.
I am not a scientist but I will try to add my 2c. (I've cut out the bits where I have nothing to add.
straight green line running centre to edge, with red marker on outside end? - muon track (can be bent at outside edge when computer gets confused, usually 2 per event), high energy
Not necessarily that high energy. Muons are quite light in the grand scheme of things so even if they're travelling fast their energy won't be so high.
other line of any colour, even green, yellow etc., usually slightly curved but not always? - charged particle of any sort in inner detector (including other muons)
Not usually muons as they don't interact that much with the material of the detector.
red dashed line? -not a particle track per se, the direction of missing energy: might be a neutrino, might represent the average of lots of them. might be dark matter etc. etc. Could also just be measurement error 😃
Technically momentum rather than energy. Energy is a scalar quantity - it doesn't have a direction.
white shaded sectors over the green and red rings? -also an indicator; in this case more generally number and intensity of calorimeter hits. Dr. Andy says it means "lots of energy" which I interpret (perhaps incorrectly) to mean it's an indicator of a jet other than a b-jet. Hadron colliders produce lots of quarks, not just bottom ones.
Actually b-jets are usually more energetic than most other jets as the b quark is one of the heavier quarks.
...although the "T" in "ATLAS" stands for "toroidal" I haven't yet found a convincing explanation for what that ginormous 2-4T field in the muon detectors should do to the muons, other than just deflect them at 90 degrees to their deflection by the field inside the inner detector. Why? More accurate momentum measurement? or is it just a cosmic ray shield? ?
Actually, I think the magnetic field extends across the whole detector - certainly across the ECAL. Its main purpose, as you say, is to deflect the charged particles. This allows their charge to be calculated (because the sideways force is proportional to the charge) and so is another way to identify which sort of particle we're talking about.
I'd be grateful if a real scientist could correct any misunderstandings please.
Cheers
StevePosted
-
by
peterwatkins
scientist
in response to brownfox's comment.
Thanks for responding to the very long message from Mark (which I will read later) but just a few comments on your shorter message.
I agree with many of your comments except|| Not necessarily that high energy. Muons are quite light in the grand scheme of things so even if they're travelling fast their energy won't be so high.
The energy of particles can be high independent of their mass - eg the photon !
|| white shaded sectors over the green and red rings? -also an indicator; in this case more generally number and intensity of calorimeter hits. Dr. ||Andy says it means "lots of energy" which I interpret (perhaps incorrectly) to mean it's an indicator of a jet other than a b-jet.
||Actually b-jets are usually more energetic than most other jets as the b quark is one of the heavier quarks.
These white shaded sectors can indicate any jet including b jet.
Notice again that energy of jet can be high for any type of jet and does not depend on fact that b quark mass is high.||Actually, I think the magnetic field extends across the whole detector - certainly across the ECAL
The solenoidal magnetic field is just in the tracking chambers and not the calorimeter. The toroidal magnetic field is in the region of the muon detectors.
For muons this means that their charge and momentum can be measured in two detectors which improves the precision of these measurements and gives some redundancy for these important measurements.Hope this helps
Posted
-
by
peterwatkins
scientist
in response to markbakovic's comment.
Mark,
Thanks for summarising many useful points in your long message which will help others.
The only minor points I would make on your text are given below
|| red block sentence - muon detector hits ..... intensity to indicate high energy muons
The signals in the muon detector only detect a charged particle and do not measure its energy (except by deflection in magnetic field)
|| blue block sentence -"b-jet" ..... remember that a lot of the tracks in question will be hidden in our views as they are not energetic enough
Some tracks are omitted because they have low energy but most are omitted because they appear to come precisely from the collision point.
|| Non-hadrons can still interact with the "hadronic calorimeter" (eg. tau leptons
Tau leptons decay very close to the collision point and so its only their decay products that interact with calorimeters
Hope this helpsPosted
-
by
markbakovic
in response to peterwatkins's comment.
Thanks for those clarifications Peter indeed they do help. My intention was to cover most of the frequent questions well enough to satisfy non-experts, leaving you guys only inaccuracies to correct or details to add. Glad I got most of it right 😃
Posted
-
by
DZM
admin
Helpful thread is really, really helpful! 😃
Posted
-
Question about; "muon" dashed red line, passing trough the detector's outer layer. Is it a glitch?
Just curious!Leonie van Vliet...
Posted
-
by
Whoandwhatitis
moderator
in response to leonie_van_vliet's comment.
Hello Leonie van Vliet,
The red dashed line indicates a measured imbalance of energy, or "missing energy". This is typically associated with neutrinos, rather than muons.
Neutrinos are capable of passing through a lot of matter without interacting because they have no electric charge. Neutrinos will go all the way through the detectors most of the time, so the red dashed line continues beyond the edge of the last layer.
Muons are charged like an electron and so they are easily tracked and typically show up as green lines with a red rectangle on the outside of the ATLAS detector. Muons typically go all the way to the last layer of the detectors, where you see the red rectangle.
Posted
-
Hi, I just started helping on this project for the second time. I was helping out for about 9 months, off and on, every so often, until about a year ago. It would be really cool if anyone on the project teams made a video(once a year) explaining some things; even if it was only 5 minutes, it would be a huge help. Maybe even a tutorial. You don't really learn much from the click-through they give you. I understand it might be useful for the limited tasks they need us for, but some of us want to learn what we're doing. I'm a senior Engineering student in my 3rd year of physics. I don't think it's too much to ask(not being a smart ass) for them to make a quick video once a year or even once a project. Aren't they saving a lot of time by getting all these people to help? I know they have a lot to do, but if they can find the time or get somebody lower on the totem pole who understands things well enough, maybe they could do it. I'm just trying to get as much as I can out of this. I think people will stay on the projects and spend more time doing the projects if they really grasp what is going on. Clicking around without really being fully engaged gets boring really fast. Sorry if this is the wrong place to put this. Maybe somebody can copy/paste it in the right spot or point me in the right direction.
Posted
-
by
ElisabethB
moderator
Hi Kenny,
See my reply to your pm.
Posted
