Z-PATH 2014COMPARISONS TO ATLAS

F. Ould-Saada et al., University of Oslo

‘H’gg

‘H’ZZ*llll

2

Invariant Mass – Overview of student results

zPath@IMC 2014

You have mastered the Invariant Mass concept and applied the technique to:

Rediscover J/y, U, Z particles and measure their masses and decay widths

Search for the Higgs boson (H) decaying to l+l- l+l- and gg

Search for a new, exotic Z’ boson that would decay into l+l-

… in a similar way as ATLAS did

Z’ MC

Z

UJ/y

zPath@IMC 2014 3

Invariant mass M(l+l-): ATLAS vs. IMC students

At the beginning of the LHC physics program, ATLAS rediscovered various standard model particles – J/y, U, Z, etc. – before seeking new phenomena

You have found the J/y (~3GeV), U (~10GeV), and Z (~91GeV) at the right masses!

The Z’ signal at ~1 TeV is Monte Carlo simulated ATLAS searches for such exotic

particles

Z’ MC

Z

UJ/y

4

ATLAS status: Z?: yes Z’? No – not yet

Z’ must be heavier than 2.9 TeV

zPath@IMC 2014

Is there any New Physics out there? For example a new weak interaction mediated by a Z’ boson?

Z (data)e+e-

Z’ MC

Z’ MC

Z (data

)m+m-

With the Invariant Mass technique you could Measure known particles Look for new hypothetical particles – Z’, exactly like

ATLAS does

Invariant mass M(l+l-): ATLAS vs. IMC students

zPath@IMC 2014 5

Higgs search H 4lATLAS vs. IMC Students

ATLAS results H ZZ* llll 25.3 fb-1

M(eemm)=123 GeV

You have searched for Higgs H llll with 2 fb-1

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ATLAS results: H gg 25.5 fb-1 clear signal You have

searched for Higgs H gg with 2 fb-1

You have several candidates at ~125 GeV You don’t have

enough statistics to reproduce the ATLAS result

zPath@IMC 2014

M(gg)=125 GeV

With 25 fb-1, you would clearly observe a signal on top of a large background.

Higgs search H gg: ATLAS vs. IMC Students