Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Why was the LHC required to find the Higgs?

  1. Oct 19, 2013 #1
    If the Higgs is around 126 GeV, why was the LHC required to find it, when the Tevatron is capable of 1 TeV collisions and had already found the top quark which is quite a bit heavier? Is this because of something special about proton-proton collisions?


    PS Please don't say "they did see the Higgs at the Tevatron!" I'm aware of those results, but clearly there must've been some reason why the LHC was thought to be more effective in discovering this particle.
  2. jcsd
  3. Oct 19, 2013 #2
    It is more difficult to see the Higgs particle in the noise. Identifying the top quark is easier than identifying the Higgs. So you need a collider with higher luminosity, which is the LHC.

    Regarding the Higgs being "found" at the Tevatron: I don't think they had 5 sigma significance to declare a discovery.
  4. Oct 19, 2013 #3
    Also, at the LHC the production is dominated by gluon fusion process via top loop.

    With higher energy hadrons (3.5, 4 TeV) the gluon Parton distribution function is larger and thus the cross section increases.

    Also Lhc detectors are newer technology, so in general better
  5. Oct 19, 2013 #4


    User Avatar
    2017 Award

    Staff: Mentor

    http://pdg3.lbl.gov/atlasblog/wp-content/uploads/2010/04/Picture-1.png [Broken]
    The plot is older than the discovery, so there is no line for 126 GeV, but 150 GeV is close enough. At the LHC, the cross-section is more than an order of magnitude larger (even with 7 and 8 TeV), and at the same time the LHC collected more collisions (25/fb integrated luminosity, while the Tevatron experiments got 10/fb). This means the LHC experiments had ~50 times more Higgs particles, with just ~2.5 times more background.
    And the LHC detectors are better, of course.

    Antiproton-proton collisions would have been even better, but at the LHC energy, that does not matter so much any more.
    Last edited by a moderator: May 6, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook