The Plot Of The Week - A Black Hole Candidate
    By Tommaso Dorigo | June 14th 2011 05:39 AM | 7 comments | Print | E-mail | Track Comments
    About Tommaso

    I am an experimental particle physicist working with the CMS experiment at CERN. In my spare time I play chess, abuse the piano, and aim my dobson...

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    CMS has recently produced an updated search for black hole production in the 7 TeV proton-proton collisions delivered by the LHC. The data sample now consists of 190 inverse picobarns of collisions collected in 2011, and the limits set on black hole production are more stringent.

    The search uses a variable called "S_T", which is the sum of transverse energies of all energetic objects detected in the final state: jets, but also, when present, electrons and muons, as well as photons and missing transverse energy. This variable would be sensitive to the production of black holes, which would produce a enhancement in the high-end of the S_T spectrum. In the figure below you can see what I am talking about, for the subset of events having at least six identified bodies with transverse energy above 50 GeV:

    As you can see, the data (black point with error bars) follow the blue background prediction, while enhancements (the dashed curves) would be present at large S_T if black holes existed with the parameter values specified. There are some very high-S_T events in the tail of the distribution, but they are compatible with expected backgrounds; from the agreement, limits can be set on the existence of black holes.

    The figure below shows a nice event display, where ten energetic jets are produced together. Calling this a "black-hole candidate" would appear sensationalistic, but it is actually what the CMS experiment does in its public document.

    The detector in this graph is seen in its transverse view, just as if you were looking at it from the beam line. Charged tracks are emitted in all directions, and they cluster in 10 different jets of hadrons, which produce as many energy deposits in the calorimeter. The latter are displayed as red and blue bars outside the schematized detector view.


    How about the data point at ~ 1.7 TeV? How many sigmas is that away from bkg? Just for curiosity...

    The data point in the 1.6 to 1.7 TeV bin appears to be at 50 events per 100 GeV and thus represents 50 events, so assuming Poisson statistics, would have sigma \simeq 7 events. The background expectation is 30 events in that bin, so that data point is just under 3 sigma above the background.

    Why would a black hole produce jets? I thought these were due to color interactions. Wouldn't it emit a nice isotropic glow?

    Hi Yatima,

    not just jets, but particles of all kinds. In fact the S_T includes leptons and missing ET. I know too little about these models to spend unclarifying words on them.

    here we should just spend some words on how you model a so complex background...


    the bkg is obviously not well modeled. The fact that CMS with 5-fold data published this inconclusive result means CMS internally knows there's nothing serious out there.

    A black hole desintegration could produces Higgs bosons too?