The best of the best in Higgs bosons to b quarks

The curves show the observed (expected) upper 95% confidence limits as solid dots (dashed line) on the Higgs boson production cross section relative to the Standard Model expectation as a function of the Higgs boson mass.

With the observation of a Higgs-like boson in photon and Z boson states at the Large Hadron Collider, the two questions one should ask next are “How Standard Model-like is it?” and “How can other experiments contribute to our knowledge of this new particle?” If this new particle is the Standard Model Higgs boson, it should decay into a pair of b quarks more often than into any other final state. The most sensitive search to date for a Standard Model Higgs boson decaying to b quarks uses the combined power of the CDF and DZero searches for the production of Higgs bosons in association with Z and W bosons, which was reported two weeks ago. The most sensitive among these searches is the CDF search for a Higgs in association with a W (WH).

At the Tevatron and LHC, b jets are produced in large amounts, drowning out the expected signal of a Standard Model Higgs boson decaying to two b quarks. The most successful way to search for a Higgs boson in this final state is to look for Higgs bosons produced in association with a W boson that decays into a neutrino and an electron or muon. This is because the background for this kind of process is far more favorable. The CDF WH search analysis uses the full data sample from Tevatron Run II. We expect about 40 signal events and 33,000 background events after basic selection requirements. The small signal and large background require that we record every event that is a candidate for a Higgs produced with a W boson, and that the most signal-like events be separated from the rest.

To accomplish this, the CDF WH team separates the events into 26 different categories. Each category has different background compositions, each comprises some fraction of the total signal and each is an analysis in itself. The work of more than a dozen analyzers converged to more than double the expected sensitivity of this analysis in comparison to the same search from CDF in 2007. The results show a signal-like excess over the background-only expectation. The excess is not significant enough to claim discovery, but is suggestive that the particle observed at the LHC is not only Higgs boson-like, but is very Standard Model-Higgs boson-like.

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These physicists were responsible for this analysis.First row from left: Timo Aaltonen (Helsinki, Finland), Barbara Alvarez-Gonzalez (Cantabria, Spain), Adrian Buzatu (McGill University, Montreal, Canada), Giorgio Chiarelli (Pisa, Italy).

Second row: Jay Dittmann (Baylor University), Martin Frank (Baylor University), Craig Group (University of Virginia and Fermilab), Richard Hughes (The Ohio State University).

Third row: Nazim Hussain (Michigan State University) , Tom Junk (Fermilab), Azeddine Kasmi (Baylor University), Ben Kilminster (Fermilab).

Fourth row: Shin-Hong Kim (Tsukuba, Japan), Michael Kirby (Fermilab), Sandra Leone (Pisa, Italy), Luri Oksuzian (University of Virginia).

Fifth row: Yoshikazu Nagai (Tsukuba, Japan), Alberto Ruiz (Cantabria, Spain), Federico Sforza (Pisa, Italy), Rocio Vilar (Cantabria, Spain).

Sixth row: Jesus Vizan (Cantabria, Spain), Andreas Warburton (McGill University, Montreal, Canada), Brian Winer (The Ohio State University).

Last row: Homer Wolfe (The Ohio State University), Wei-Ming Yao (Berkeley, California).