Center for Particles and Fields Seminar

Dr. Robert Harrington, The University of Edinburgh & CERN

"From Discovery to Understanding: Higgs Physics, Muon Detection and Beyond"

2:00pm, RLM 9.222

Abstract:
The Large Hadron Collider (LHC) at CERN is a powerful tool for answering some of the most fundamental questions about nature. With the discovery of a new particle consistent with a Higgs boson in July 2012, a new chapter has begun with new unanswered questions. Perhaps the most important of these is whether the new particle is the Higgs boson expected by the Standard Model (SM), or just one of a number of Higgs bosons expected by beyond-SM (BSM) theories. With data from the next few years of running at the LHC, the picture is expected to be more complete as we measure additional properties of the Higgs boson. We may, on the other hand, find something new and even more exciting!

I will focus on measurements of Higgs boson properties in the important 4-lepton decay channel (H->ZZ->4l), called the "golden channel" because of the excellent mass resolution and the large signal-background ratio (about 2:1). I will describe some of the measurements done in Run-1 with the ATLAS detector using 7 and 8 TeV data, including the measurement of the Higgs boson mass. In Run-2, for which the LHC expects to produce 7-8 times the Higgs bosons produced in Run-1, measurements in the 4-lepton channel will continue to be important. At higher center-of-mass energies, searches for additional Higgs bosons above 125 GeV are interesting with much less data and will be important early in Run-2. Equally important, however, will be observation of Higgs decay directly to muons. Although it is expected to be out of reach using Run-2 data alone for a SM Higgs boson, I will describe a new method which could put observation of Higgs decay to muons within reach. These measurements rely on the ATLAS muon detector and charged particle tracking, so muon detection for Run-1 and plans for the upgrade for the High Luminosity LHC (HL-LHC) will be presented as well.