A Typical LHC plot

Here is a typical LHC plot 🙂

As you can see, with 1.1/fb CMS has observed one event in a channel that may give a signal of a Higgs through decay to two Z bosons which in turn decay to two tau leptons and two other leptons. This is consistent with standard model backgrounds shown.

It will require about 100 times as many events for this channel to make any real impact on the search for the Higgs boson. Luckily the LHC will eventually record a few thousand /fb so this channel will be very useful.

There are other channels with better cross sections but results ao far shown have still used just a few events, or they are swamped by thousands of background events. It is possible to combine several channels and compare with what is expected from a particular theoretical model such as a standard model Higgs boson or MSSM supersymmetry, but such models tend to work in a reduced parameter space and may not match reality well. In the case of supersymmetry they look at models where a stable lightest particle is in reach of the LHC so that it shows up in missing energy searches. It would have been nice if this led to a quick discovery but it hasn’t.

Int ime each of these channels will be populated with lots of events and can be compared with standard model backgrounds. Bumps could appear anywhere leading to the discovery of some new particle. Once its properties are mapped through its different decay modes it can be fitted into a new model, which may or may not correspond to a supersymmetric multiplet.

People are starting to say that supersymmetry is in a corner, or even that the LHC seems to be incapable of producing new physics. It is far too early for any such conclusions. We need to be patient.


One Response to A Typical LHC plot

  1. Jesus says:

    Cool, nice post. This is exactly what I always think, when people try to make any conclusions with the available recorded data. It is possible to make exclusions or discoveries, BUT: always only considering the error bars!

    Within every error bar there could always be a signal or none. Also a bump should always be considered as such one when the bars are smaller than the bump itself…

    And by the way also with 1000/fb recorded there could still be a hidden new physics bump in any distribution, which would appear at 1000000/fb and so on…

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