The Higgs boson in the Standard Model theoretical constraints and a direct search in the wh channel at the Tevatron
- Pierre and Marie Curie Univ., Paris (France); Bielefeld Univ. (Germany)
We have presented results in two different yet strongly linked aspects of Higgs boson physics. We have learned about the importance of the Higgs boson for the fate of the Standard Model, being either only a theory limited to explaining phenomena at the electroweak scale or, if the Higgs boson lies within a mass range of 130 < mH < 160 GeV the SM would remain a self consistent theory up to highest energy scales O(mPl). This could have direct implications on theories of cosmological inflation using the Higgs boson as the particle giving rise to inflation in the very early Universe, if it couples non-minimally to gravity, an effect that would only become significant at very high energies. After understanding the immense meaning of proving whether the Higgs boson exists and if so, at which mass, we have presented a direct search for a Higgs boson in associated production with a W boson in a mass range 100 < mH < 150 GeV. A light Higgs boson is favored regarding constraints from electroweak precision measurements. As a single analysis is not yet sensitive for an observation of the Higgs boson using 5.3 fb-1 of Tevatron data, we set limits on the production cross section times branching ratio. At the Tevatron, however, we are able to combine the sensitivity of our analyses not only across channels or analyses at a single experiment but also across both experiments, namely CDF and D0. This yields to the so-called Tevatron Higgs combination which, in total, combines 129 analyses from both experiments with luminosities of up to 6.7 fb-1. The results of a previous Tevatron combination led to the first exclusion of possible Higgs boson masses since the LEP exclusion in 2001. The latest Tevatron combination from July 2010 can be seen in Fig. 111 and limits compared to the Standard Model expectation are listed in Table 23. It excludes a SM Higgs boson in the regions of 100 < mH < 109 GeV as well as 158 < mH < 175 GeV based on the observed final limits at 95% C.L. In the most interesting low mass region between 115 and 135 GeV, even the full Tevatron combination is not yet sensitive enough to exclude a Higgs boson, or to even prove its existence with a meaningful significance. Fig. 112 shows a projection plot for sensitivity to the SM Higgs boson at the Tevatron as a measure of increasing luminosity. The 10 fb-1 projection is a rather conservative outlook for the coming year of data taking as the Tevatron runs smoothly and the run till the end of 2011 is assured. By now, already 9 fb-1 have been recorded by the two experiments. As the extrapolation plot shows, this amount of luminosity will allow to exclude the Higgs boson over a wide mass range at a 95% C.L. With the LHC at CERN now running and successfully collecting first data, it is worth looking at projections of Higgs boson sensitivity at the current center of mass energy of 7 TeV of the LHC accelerator. Fig. 113 shows a projection of a possible SM Higgs boson exclusion using 1 fb-1 of LHC data collected by the ATLAS experiment. An exclusion is expected between 135 and 188 GeV at 95% C.L., combining the three decay channels H → WW, H → ZZ and H → γγ. A combination between LHC experiments would possibly yield an even broader range of excluded Higgs boson mass points. Therefore, whether at the Tevatron or the LHC, exciting times in the exclusion or possible discovery of the SM Higgs boson lie ahead.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-07CH11359
- OSTI ID:
- 988899
- Report Number(s):
- FERMILAB-THESIS-2010-38; TRN: US1007029
- Country of Publication:
- United States
- Language:
- English
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