Session J2: Invited Session: Standard Model Higgs Boson Searches

Higgs Theory and Phenomenology in the Standard Model

Particle physics has entered an exciting era: The CERN Large Hadron Collider (LHC) performed exceptionally well since its start of operation at an energy of 3.5 TeV per beam in 2010 and is exploring the new energy regime where we hope to find answers to some of the most fundamental questions in particle physics and cosmology. Soon, the LHC may reveal the origin of electroweak symmetry breaking, discover physics beyond the Standard Model, and may even identify a candidate for dark matter. The Standard Model (SM) has been immensely successful in describing electroweak and strong interactions of fundamental particles, surviving all experimental tests since its formulation in the 1970s. Nevertheless, it leaves many questions unanswered, not the least of which concerns the origin of mass. The experimental fact that weak gauge bosons, the $W^\pm$ and $Z^0$ bosons, are massive has been accommodated within the SM by spontaneously breaking the electroweak symmetry via the Higgs-Kibble mechanism. As a consequence of this mechanism, the SM requires the existence of a spin-0, neutral, massive particle, the Higgs boson. We know from comparing very precise measurements of properties of SM particles, such as the $W$ and $Z$ bosons, to their SM predictions (which depend on the Higgs boson mass through quantum-loop effects), that the Higgs boson is relatively light. So light, in fact, that it should not escape detection at the LHC, if it exists. The search for the Higgs boson and the measurement of its properties, once discovered, requires excellent theoretical control of predictions for its production and decay processes. Since the very rare Higgs event has to be extracted from a much larger background of processes that do not include a Higgs, these background processes have to be very well understood, as well. I will review recent theoretical advances in providing precise predictions of observables of Higgs production and background processes that are crucial in the search for the SM Higgs boson at the LHC.   

Standard model Higgs boson search results with the full Tevatron dataset

The Tevatron's program of colliding protons and anti-protons at a center-of-mass energy of 1.96 TeV ended in September of 2011 after more than 25 years of data collection. I will describe the recent efforts of the CDF and D0 collaborations to maximize their sensitivity to the Higgs boson using the complete dataset. The sensitivity of the LHC experiments at CERN is quickly surpassing the Tevatron in most new physics searches; however, in some Higgs decay channels, such as searches in the b b-bar final state, the Tevatron results will remain competitive for quite some time. I will focus the talk on the Tevatron results with the full dataset, but will also discuss the complementarity of the information that will be provided by the Tevatron and LHC experiments.   

Standard Model Higgs Search

The outstanding performance of the Large Hadron Collider in 2011 set the grounds for the final hunt for the Standard Model Higgs boson. ATLAS and CMS, the two largest all-purpose High Energy Physics detectors, collected about 5 fb-1 of high quality data each at 7 TeV center-of-mass energy of proton-proton collisions. This was sufficient to set the limits on the Higgs boson production cross section well below its Standard Model expectation in most of the region of interest (between 115 and 600 GeV/c2). Nevertheless the most theoretically favorable interval of masses, 115 - 127 GeV/c2, remains open for searches. In the report we will summarize strategy and results of multiple channel search for the Standard Model Higgs boson of the two collaborations.