Amazing dijet event from ATLAS

Via the ICHEP webcast I watched the talk “Early Searches with Jets with the ATLAS Detector at the LHC” by Georgios Choudalakis yesterday afternoon. It included this dijet event with one jet of 1.1 TeV and another of 480 GeV. In fact some of the energy of the lower energy jet was probably lost in the crack between two calorimeters and its real energy may have been just as large, we were told.

Of course one event proves nothing but to have such a high energy diject at such an early stage is nonetheless tantalising. If they had a similar event like this for every 300 inverse nanobarns of data over the next month I think  they would very soon be able to claim a discovery. Events with this much energy could never have been produced at the Tevatron so it is exactly what they need to look for to see new physics that could not have already been discovered.

In the same talk we were shown some other plots placing limits on various high energy resonances to demonstrate that they are already producing new physics results at the LHC, even if they are negative results so far. The integrated luminosity used in these plots was 296 inverse nanobarns, yet they have improved on the best limits set by the Tevatron using about 3000 times as much data.

To get that much they must have used data from runs up until the 18th July, missing just the final run before the conference. Earlier it had been said that they would have to use data up to just the end of June in order to get it approved in time.

5 Responses to Amazing dijet event from ATLAS

  1. Ulla says:
    Zoltan Ligeti, a physicist at the Lawrence Berkeley National Laboratory in California, and his colleagues have calculated that as it ramps up, the LHC will generate enough collisions to produce clear signatures of a hypothetical “diquark” particle proposed by some forms of string theory.

    – Which forms, I wonder? Goldstone (meson) boson?

    a 3.2sigma deviation from the standard model prediction in the like-sign dimuon asymmetry.

  2. Ulla says:
    The simplest supermodels involve s-channel resonances in the quark-antiquark and especially in the quark-quark channels.

    classify the decay modes of new resonances in terms of three basic decay topologies, which often appear in perturbative new physics (topological) scenarios, X
    A. directly to two detectable final state particles.
    B. decays to one detectable final state and one new secondary resonance
    Y .
    C. decays to two new secondary resonances Y1 and Y2, diff. mass?

    A model, but so close? A scaling hierarchy? A quasiparticle with EMD-charachter? Why has it been hiding?

  3. Ulla says:

    From his thesis,

    Related to hierarchy is the the problem of “naturalness” in the Standard Model. A small parameter in a theory is “natural” when setting it to zero increases some symmetry of the theory, therefore its smallness can be attributed to that very symmetry.
    For instance, the masslessness of a vector field such as the photon can be related to the gauge invariance of the theory. However, for a scalar field, such as the Standard Model Higgs, no symmetry is there to protect its mass from acquiring quadratically divergent corrections at the loop level (Fig. 1-3), unless the theory is highly fine-tuned (Fig. 1-2). The required precision of fine-tuning depends on how far one wishes to extend the validity of the Standard Model. If one wishes it account for
    loop corrections up to the Planck scale, while keeping the Higgs lighter than 1 TeV, as required by electroweak measurements, then the required fine-tuning is so precise that it seems unnatural (hence the connection between naturalness and hierarchy).
    A solution to this can be either to abandon the concept of fundamental scalars, as in technicolor models (Sec. 1.2.4), or to search for a theory where quadratic divergences cancel, as in Supersymmetry (Sec. 1.2.2).

    He forget the other types of numbers, as primes.

    The technicolor version:
    …is new strong dynamics. With the introduction of a new non-abelian gauge symmetry and additional fermions (“technifermions”) which have this new interaction, it becomes possible to form a technifermion condensate that can break the chiral symmetry of fermions, in a way analogous to QCD where the q¯q condensate breaks the approximate SU(2) × SU(2) symmetry down to SU(2)isospin. The breaking of global chiral symmetries implies the existence of Goldstone bosons, the “technipions” (πT ), in analogy with QCD pions. Three of the Goldstone bosons are absorbed through the Higgs mechanism to become the longitudinal components of the W and Z, which then acquire mass proportional to the technipion decay constant.

    If quarks and leptons are not elementary, then they are predicted to have excited states

    What is absorbing the energy and how? This is something to think at?

  4. Ulla says:

    If you look at Lubos he talks of course only in favior of the MSSM model.

    He forgets completely all other hierarchies.

  5. philipgibbs says:

    If you see my latest psot you will know that I have some shmpathy for Lubos’s point of view. But yes something else might be the reality. Anyone who can make an equally convincing case for the alternatives should write about it for us.

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