# IOP 2014 Joint HEPP & APP Group Meeting

7-9 April 2014
Royal Holloway, University of London
Europe/London timezone
Institute of Physics 2014 Joint High Energy Particle Physics and Astro Particle Physics Groups Annual Meeting

## ATLAS results on the Higgs boson properties in the decay channel $H\rightarrow ZZ\rightarrow 4\ell$

8 Apr 2014, 16:15
15m
Room C (Windsor Building)

### Room C

#### Windsor Building

contributed talk The Energy Frontier Programme

### Speaker

Ludovica Aperio Bella (University of Birmingham (GB))

### Description

This contribution will review the latest ATLAS results on the properties of the Higgs boson in the decay channel $H\rightarrow ZZ\rightarrow 4\ell$ using approximately 25 fb-1 of pp collision data collected during the LHC Run1 at 7 TeV and 8 TeV. The measurements of the mass and the couplings of the newly discovered boson are presented together with the spin-parity analysis results.

### Summary

Since the discovery of a Higgs-like boson by the ATLAS and
CMS experiments at the LHC, the emphasis has shifted towards
measurements of its properties. A review of the latest ATLAS results on the properties of the Higgs boson in the decay channel H—>ZZ—>4l channel using approximately 25 fb-1 of pp collision data collected during the LHC Run1 at 7 TeV and 8 TeV, is presented.
In the four lepton final state a clear excess of events over the background is observed at mH = 124.3 GeV with a significance of 6.6 standard deviations.
Thanks to the very good lepton's energy resolution was possible to perform a mass measurement which is found to be mH = 124.3+0.6-0.5 (stat)+0.5-0.3 (syst) GeV, and the signal strength (the ratio of the observed cross section to the expected SM cross section) at this mass is found to be μ = 1.7+0.5-0.4.
Moreover, a study of Higgs boson production mechanisms allows a first measurement of couplings with this channel. A spin-parity analysis is also performed on the events with reconstructed four-lepton invariant mass m4l satisfying 115 GeV < m4l < 130 GeV. The Higgs-like boson is found to be compatible with the SM expectation of 0+ when compared pair-wise with 0− , 1+ , 1− , 2+ , and 2− . The 0− and 1+ states are excluded at the 97.8% confidence level or higher using CLS in favour of 0+.

### Primary author

Ludovica Aperio Bella (University of Birmingham (GB))

 Slides