Abstract:

After years of anticipation and preparation, CERN's Large Hadron Collider (LHC) enjoyed a successful year of proton-proton operations in 2010 at 7 TeV center-of-mass energy. An unexpectedly long commissioning period left the ATLAS detector and collaboration well prepared to take advantage of the first data. Commissioning of the detector, data handling, and data preparation machinery with cosmic rays and first beams has quickly transformed into physics analysis. Abundantly produced at hadron colliders, samples of jets from quark and gluon production were used for several of the first ATLAS physics publications. These included measurements in the Standard Model context like the inclusive jet cross section, but also early searches for new physics using events featuring two highly energetic jets. These TeV scale dijet events quickly surpassed the reach of earlier colliders and offer one of the highest energy probes for new physics available in the laboratory. We analyzed these events using complementary sources of information: the dijet invariant mass and angular distributions. Unfortunately, the first searches, using a small portion of the 2010 dataset, yielded no evidence for new physics. So, we proceeded to set limits on various postulated phenomena including quark substructure and quantum black hole production in the presence of large extra dimensions. After a brief review of the ATLAS detector and preparations for physics, I will describe jet physics measurements in the Standard Model context, and searches for new physics using dijet invariant mass and angular distributions. These include the first search at the LHC to exceed the reach of the Tevatron - with less than one thousandth the Tevatron luminosity. The energy frontier has certainly moved to the LHC. Pending approval, I will present updated results from the dijet searches - among the first ATLAS results with the full 2010 dataset.