Higgs Hunters Talk

The ATLAS "Ridge"

  • Whoandwhatitis by Whoandwhatitis moderator

    There seems to be a lot of collaboration and modeling going on around the recently-discovered "ridge" from ATLAS.

    I first learned about this phenomenon here on July 30, 2015:
    Physics and Performance With 13 TeV Proton Collisions

    ATLAS physicists also measured the angular correlation among pairs of
    the produced charged particles, confirming the appearance of a
    so-called "ridge" phenomenon in events with large particle
    multiplicity at a centre-of-mass energy of 13 TeV. The "ridge"
    consists of long-range particle–particle correlations not predicted by
    any of the established theoretical models describing inelastic
    proton–proton collisions.

    Now I see that a paper was published on Oct 1, 2015 on this topic:
    Observation of long-range elliptic anisotropies in s√=13 and 2.76 TeV pp collisions with the ATLAS detector

    As I understand this, these are saying that pairs of similar particles are being produced at a higher rate than is expected with our current models?

    From the paper:

    The ridge has also been observed in proton-lead (p+Pb) collisions
    [2–7], where it is found to result from a global sinusoidal modulation
    of the per-event single-particle azimuthal angle distributions [3–6].

    Does this mean that there could be some physics that is causing a second particle to be produced where only one would normally be expected?
    Since sinusoidal modularity is mentioned, could this be the result of some underlying function of what we refer to as space-time?

    I'm no expert with this stuff, so I might be asking some odd questions here. Fill me in! 😃

    Thank you!


  • alanbarr by alanbarr scientist

    I've not been involved in this analysis directly, but there's a nice write-up back in:

    "Such double-ridge structures are typically found in collisions of heavy ions and have their origins in collective phenomena occurring in the quark–gluon plasma that is created. However, these phenomena are not generally thought to occur in proton–lead collisions, where the size of the collision region is expected to be too small to allow the development of significant collective effects."

    So it seems like we are seeing collective effects in proton-proton collisions