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The Hunt for the Higgs

Where do the masses come from?

The key question: Where is the Higgs?

Scalar field with at least one scalar particle

We do not know the mass of the Higgs Boson

It could be anywherefrom 114 to 700 GeV

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The Compact Muon Solenoid

Searches for the Higgs Particle

But two Z bosons can also be produced in LHC collisions, without involving a Higgs!We cannot say for on event by event (we can use the total invariant mass of the 4 muons)

Example: Higgs(?) decays into ZZ and each Z boson decays into μμ

A Higgs particle will decay immediately, eg in two heavy quarks or two heavy (W,Z) bosons

So we look for 4 muons in the detector

A Collision with two Photons

A Higgs or a ‘background’ process without a Higgs?

CMS Higgs Studies

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Expected exclusion 114.5 - 543 GeVObserved exclusion 127.5 - 600 GeV

The 2011 Data Combination

Standard Model Higgs should be above the red line

Dashed line: expected sensitivitySolid line: actual data

What did we learn from the data last year?

So, where is the Higgs Boson?

• The experiments analysed the data for the full year of 2011 • They can exclude an even larger range, and restrict the

region for the Higgs to 115-130 GeV• But.. they see a tantalizing excess in the “Higgs” mass

range of 120-126 GeV. This is exciting!• The significance of this excess is still too low to claim a

discovery, but a Higgs signal could just start to be seen just like that. The excess could still go away with more data.

• The Higgs boson could well be showing signs of life already in the 2011 data…

• The LHC 2012 data will be the referee…

LHC is doing very wellLast year: luminosity 3 . 1033 cm-2 s-1 5.7 fb-1 collected in totalThis year: luminosity 6.5 . 1033 cm-2 s-1 6.2 fb-1 collected so far Luminosity = number of events/cross section/time

What about the 2012 data?The ZZ and γγevents are there in 2012!Will they be at a similar rate as for the 2012 data? Will the 2012 confirm the 2011 excess?

->A discovery is possible…The 2012 data will be disclosed today at CERN and ICHEP/Melbourne

2 photon eventZZ-> μμee event

The Higgs