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Homework Help: Roughly estimate the probability that 2 photons are from Higgs

  1. Dec 9, 2017 #1
    1. The problem statement, all variables and given/known data
    Make a very rough estimate of the probability that two high energy photons with an invariant mass of 126GeV are decay products of the Higgs. Use information found elsewhere (so I need to find this info preferably on the internet).

    2. Relevant equations


    3. The attempt at a solution
    I'm not really sure what I need for my estimate! Would it work if I find the number of background events at 126GeV and the number of Higgs events then do Higgs / (Higgs + background) ? That sort of data is proving hard to find, so I suspect I should be looking for some other information... I did think the table on page 4 http://inspirehep.net/record/1257018/files/ICHEP2012_045.pdf here might be useful, if I knew how to interpret it.

    I'd really appreciate any pointers on where I might find data on the number of events, or whether that's completely the wrong approach. Thanks for any help! :)

    Edit: I could maybe very crudely read the values off this graph, I think it's about 400 Higgs events in the 5000 total events? But I could be horribly misinterpreting the meaning of the graph.
    http://www.particleadventure.org/the-data-for-higgs-boson-decaying-to-two-photons.html
     
    Last edited: Dec 9, 2017
  2. jcsd
  3. Dec 9, 2017 #2

    Orodruin

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    This question is very very vague as it does not specify where those two photons are found and what the procedure to find them was.

    Assuming that you want it at CMS after all cuts etc, you could use the references you provided (figure 3 in the first one is essentially equivalent to the image in the blog post). I would reference the original papers instead of an online blog or a conference proceeding though.
     
  4. Dec 9, 2017 #3
    I'm not sure from which collaboration the data should come, but I think CMS would be acceptable. It is very vague, I might ask for clarification! Thanks for your help. :)
     
  5. Dec 10, 2017 #4

    mfb

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    Well, you just have two options for the source, ATLAS and CMS. Both are fine.
    The fraction depends on the collision energy, the transverse momentum of the photons and various other things, so taking a random publication should be fine - you won’t get more than a very rough approximation anyway.

    126 GeV is an outdated mass calue, by the way. There are probably nearly no Higgs events there, although the experiments see some based on their finite resolution.
     
  6. Dec 10, 2017 #5

    Orodruin

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    That is assuming that the setting is a particle collider experiment that is looking for the Higgs, which is not specified by the question itself. It may be specified in the actual assignment, but this is not something we can know. I can go looking for photon pairs with an invariant mass of 126 GeV in my living room and none of the ones I find (if any) will be due to Higgs decays. My point is that just specifying "two high energy photons" tells us nothing of the setting in which they are to be looked for. I agree that it might be reasonable to assume one of the LHC experiments, but the question itself really does not tell us.
     
  7. Dec 10, 2017 #6

    mfb

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    Technically correct, but I’m sure this is in the context of the LHC.
     
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