Higgs Physics at Sheffield

The Sheffield High Energy Physics group is an active participant in the ATLAS experiment, one of the general purpose detectors being built to exploit the exciting physics potential of the Large Hadron Collider (LHC) at CERN. ATLAS has been designed to search for signals that will enable physicists to understand the fundamental laws of nature and in particular the acquisition of mass through the so-called Higgs mechanism. Thus, data from the ATLAS experiment are probing the basic forces that have shaped our Universe since the beginning of time and that will eventually determine its fate.

The group played a leading role in direct discovery of the Higgs boson announced in July 2012 by the ATLAS and CMS collaborations. This discovery led to the award of the 2013 Nobel Prize to Peter Higgs and Francois Englert “for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles”.

The main interest of the group is the study of the properties of the Higgs boson via its decays into two Z bosons which in turn each decay into an oppositely charged pair of electrons or muons. These decays are so-called the "golden" channel as they have the lower level of background noise.

Additionally, the Sheffield group is heavily involved in the search of SM Higgs boson or a new resonances with mass larger than 250 GeV (BSM), decaying to a Z boson and a photon. The Z bosons are identified through their decays either to charged, light lepton pairs.

Searching for the Higgs

4l Animation

Evolution of the 4-leptons invariant mass spectrum in 2011 and 2012 data

The distributions of the four-lepton invariant mass, m4l, for the selected candidates compared to the background expectation for the combined sqrt(s)=8 TeV and sqrt(s)=7 TeV data sets .The signal expectation for a Higgs boson with mass 125 GeV is shown.
4e

Event display of a Higgs Candidate decaying to 4 electrons

4mu

Event display of a Higgs Candidate decaying to 4 muons

2e2mu

Event display of a Higgs Candidate decaying to 2 electrons and 2 muons

Public ATLAS Higgs results (link)

Research Interests

Selected Publications

Search for heavy resonances decaying to a Z boson and a photon in p p collisions at sqrt(s) = 13 TeV with the ATLAS detector
By ATLAS Collaboration (Georges Aad et al.).
ATLAS-CONF-2016-010
Phys. Lett. B in preparation.

Search for the Standard Model Higgs boson decay to a photon and a Z boson in pp collisions at √s = 7 and 8 TeV with the ATLAS detector
By ATLAS Collaboration (Georges Aad et al.).
[arXiv:1402.3051 [hep-ex]].
10.1016/j.physletb.2014.03.015.
Phys. Lett. B 732C (2014), pp. 8-27

Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC.
By ATLAS Collaboration (Georges Aad et al.).
[arXiv:1207.7214 [hep-ex]].
10.1016/j.physletb.2012.08.020.
Phys.Lett. B716 (2012) 1-29.

Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC.
By ATLAS Collaboration (Georges Aad et al.).
[arXiv:1307.1427 [hep-ex]].
10.1016/j.physletb.2013.08.010.
Phys.Lett. B726 (2013) 88-119.

Evidence for the spin-0 nature of the Higgs boson using ATLAS data.
By ATLAS Collaboration (Georges Aad et al.).
[arXiv:1307.1432 [hep-ex]].
10.1016/j.physletb.2013.08.026.
Phys.Lett. B726 (2013) 120-144.

Measurement of the Higgs boson mass from the H → γ γ and H → ZZ(*) → 4l channels with the ATLAS detector using 25 fb-1 of pp collision data.
By ATLAS Collaboration (Georges Aad et al.).
[arXiv:1406.3827 [hep-ex]].
10.1103/PhysRevD.90.052004.
Phys.Rev. D90 (2014) 052004.

A 2D fit with background measurement constraints to boost the Higgs to 4l discovery potential at the LHC.
By Christos Anastopoulos, Nicolas Kerschen, Stathes Paganis.
[arXiv:1109.2178 [hep-ex]].
10.1140/epjc/s10052-011-1746-7.
Eur.Phys.J. C71 (2011) 1746.



Department of Physics and Astronomy, University of Sheffield, Hounsfield Road, Sheffield S3 7RH, UK

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