Search for Extra Dimensions in Jets+Missing Energy in RunII


Introduction:

Events with large missing transverse energy and one or more energetic jets can be produced in many models of new physics, in addition to standard model production from electroweak and QCD processes. One model of new physics that can produce such a signature is the compactified Large Extra Dimensions (LED) model of Arkani-Hamed, Dimopoulos, and Dvali (ADD). In such a model, gravitons are produced directly in processes such as qqbar->gG, qg->qG, or gg->gG, where G is the emitted graviton. The emitted graviton will be undetected, leaving the final state quark or gluon to produce a jet. In all cases, the signature will be jets plus missing energy.
We present results of a search for direct graviton production using 368 pb-1 of data from the Jet100 sample. A comparison is made of the data to the expected backgrounds, and in the absence of a signal, limits are obtained.

Kevin Burkett, Eric James, Avi Yagil
Fermilab
Pierre-Hughes Beauchemin, Pierre Savard
University of Toronto

  • Contact people : Eric, Hugo, Kevin, Pierre

  • Documentation:

  • Talks:

  • Blessed Plots:





  • Measured W,Z+Jet Cross-Sections:


    Cross-sections for W and Z plus jets as a function of the leading jet ET.





    Data vs SM Predictions:


    These plots show a comparison of the predicted events in our sample coming from Standard Model sources and the events seen in the data. The plot on the left shows the leading jet ET distribution while the plot on the right shows the Missing ET distribution.





    QCD Background Estimation:


    The plot on the left shows the results of the method used to estimate the number of QCD events in our final sample. The plot on the right shows that the delta(phi) distribution is well-modeled in Monte Carlo.





    Limits on MD:



    We can convert the limit on the number of events into a limit on MD. The limits on MD (in TeV/c2) for n=2-6 with K factors of 1.0 and 1.3 are shown in the table below.
    n
    MD (K=1.0)
    MD (K=1.3)
    2
    1.09
    1.16
    3
    0.93
    0.98
    4
    0.87
    0.90
    5
    0.82
    0.85
    6
    0.80
    0.83


    The limits are compared graphically with limits from D0 and LEP in the plot shown below.


    We can also convert the limit on MD to a limit on the size of the extra dimensions (assuming here compacitification on a torus). The limits on MD(in TeV/c2) for K=1.3 and the corresponding limits on R (in mm) are shown in the table below.
    n
    MD (TeV/c2)
    R(mm)
    2
    > 1.16
    < 0.36
    3
    > 0.98
    < 3.7 x 10-6
    4
    > 0.90
    < 1.1 x 10-8
    5
    > 0.85
    < 3.5 x 10-10
    6
    > 0.83
    < 3.4 x 10-11




    Event Displays:


    The following event displays are from the two highest MET events.


    Run 155313, Event 273486: Et(1) = 384 GeV, MET= 390 GeV

    Run 177315, Event 842753: Et(1) = 361 GeV, MET= 350 GeV



    Last updated : November 21, 2005