Abstract
We search for evidence of physics beyond the Standard Model in the production of final states with multiple high transverse momentum jets, using 20.3 fb$^{-1}$ of proton-proton collision data recorded by the ATLAS detector at $\sqrt{s} = 8$ TeV. No excess of events beyond Standard Model expectations is observed, and upper limits on the visible cross-section for non-Standard Model production of multi-jet final states are set. Using a wide variety of models for black hole and string ball production and decay, the limit on the cross-section times acceptance is as low as 0.16 fb at the 95% CL for a minimum scalar sum of jet transverse momentum in the event of about 4.3 TeV. Using models for black hole and string ball production and decay, exclusion contours are determined as a function of the production mass threshold and the gravity scale. These limits can be interpreted in terms of lower-mass limits on black hole and string ball production that range from 4.6 to 6.2 TeV.
Highlights
Background estimation methodEvents are selected if they pass the high-HT trigger and have HT > 1.5 TeV
The different MC contributions are first weighted according to their cross sections, and the total SM contribution is normalised to the number of data events in the region 1.5 < HT < 2.9 TeV for each inclusive jet multiplicity
For Njet ≥ 8, the jet energy scale (JES) uncertainty rises from 21% at the lower edge of the HT range to 34% at the limit of no data, and the jet energy resolution (JER) uncertainty rises from 7% to 11%
Summary
Understanding quantum gravity is one of the main challenges of modern physics. The hierarchy problem (the relative weakness of gravity compared to the electroweak interaction) may be key to that understanding. Two main paradigms for models involving extra dimensions have been formulated: the Arkani-Hamed, Dimopoulos, Dvali (ADD) proposal [1, 2] involving large extra dimensions; and a five-dimensional model with a single highly warped anti-de Sitter space [3, 4]. Most low-scale gravity models assume classical general relativity to predict the production cross section for black holes (σ ∼ πrg2) and string balls, and use semi-classical Hawking evaporation (a completely thermal process due to quantum effects) to describe their decay [20]. When the black hole mass is reduced to approximately MD (or Ms for string balls), the black hole is said to be in a remnant state, which is expected to only be describable by a theory of quantum gravity. Since black hole decay is considered to be a stochastic process, a different number of particles, and jets, can be emitted from black holes with identical kinematics
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