Quest for the Higgs boson (and beyond !)

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Back to UZH CMS Physics analyses

The Higgs boson provides mass to fundamental particles.  It does this by flipping left-handed particles into right-handed particles and vice-versa.  For a primer on handedness,        see my page "The sun is left-handed". 
 

Starting around 2005, I started searching for the Higgs boson.  At the time, we knew we would need more data and better techniques to discover it.  In 2012, simultaneously, the CMS and ATLAS experiments observed the Higgs boson in Europe, while the CDF and D0 experiments found evidence for it in the U.S. 

In my first year at CMS, with my experience as the leader of the Higgs boson search group at CDF, I was on the Analysis Review Committee for 5 different combined searches to observe the Higgs boson.  Finally, we announced the observation of the Higgs boson on July 4, 2012.  This publication has been cited almost 10000 times. 

After the excitement of the discovery, my UZH group worked on some outstanding problems related to the Higgs boson : 

Observation of the Higgs boson coupling to fermions (tau leptons)

Higgs decaying to tau leptons included in CMS combination

Searching for additional Higgs boson (supersymmetric)

Searching for gravitons interacting with Higgs bosons

Searching for extended Higgs boson structure

We also searched for new heavy boosted particles decaying to Higgs bosons : 

• W' -> WH (lvbb)
• WH and ZH (all-jets)
• X -> Higgs+leptons
• X-> VH (all-hadronic)
• X-> VH -> leptons+bb

And we even looked for a light, Higgs-like particle decaying to tau leptons : 

• Search for a low-mass τ−τ+ resonance with a b quark

From 2000 until 2012, I searched for the Higgs boson with the CDF experiment at the Tevatron at Fermilab. I contributed novel techniques to three different methods of searching for the Higgs boson, and led the group for several years. 

Here are some publications over this journey, starting with some hope in 2000, and finally culminating in evidence for the Higgs boson at the Fermilab Tevatron in July 2012. 

The hope (2000)

Higgs boson first meets Machine Learning in 2008 (ZH->llbb 1fb^-1)

First Combined Higgs exclusion

The invention of trackMet and the trackMET Neural Network (ZH->MET+bb)

The invention of Neural Network b-jet energy corrections

ZH-llbb 4.2fb-1

Neural networks for triggering, lepton selection, energy corrections, b-tagging, and signal discrimination (ZH->llbb 8fb-1)

Adding b-jet corrections to WH->lvbb with 7.5 fb-1

The final word WH-> lvbb 9.5 fb-1

The final word ZH->llbb 9.5 fb-1

The final word WH/ZH -> METbb 9.5 fb-1

CDF Combining H->bb (2.5 Sigma excess)

Combining H->bb at the Tevatron (3.3 Sigma evidence for Higgs boson July 2012)

Final total Tevatron combination (Significance drops to 3.0 Sigma evidence)

Watch a documentary called "The Atom Smashers" that I was featured in (when I was younger and cooler) about our search for the Higgs boson before we found it.    It was on PBS Independent Lens. You can find more here and here.