Dr Christos Anastopoulos

Department of Physics and Astronomy

Royal Society University Research Fellow

c.anastopoulos@sheffield.ac.uk
+44 114 222 4523

Full contact details

Dr Christos Anastopoulos
Department of Physics and Astronomy
F42
Hicks Building
Hounsfield Road
Sheffield
S3 7RH
Profile

I am a Royal Society University Research Fellow at the University of Sheffield and a member of the ATLAS collaboration

My research focuses on the understanding of fundamental particles and forces of nature, in particular the origin of mass.

I played a crucial role to the analysis that led to the discovery of the Higgs boson at the LHC, for which The Nobel Prize in Physics 2013 was awarded.

Research interests

My primary research interests are on experimental particle physics as a member of the ATLAS collaboration. ATLAS is a multi-purpose detector operating at the Large Hadron Collider at CERN in Europe.

It 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.

I made substantial contributions to the 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 François Englert “for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles”.

Over time I have also worked on the reconstruction of electrons in ATLAS by combining the information from the ATLAS tracker and electromagnetic calorimeter. This constituted the ground-work for the discovery of the Higgs boson via its decays to four leptons which I was involved in.

The discovery of the Higgs boson opens the way to a new phase of particle physics in which the study of its properties will allow an examination of the nature of the Higgs in detail and perhaps will also provide the means for new discoveries.

We know that the particle we have discovered is a brand new boson. Even though it fulfils the basic requirements of a Higgs boson, it is not clear that its properties correspond exactly to those predicted for the Higgs boson by the standard model of particle physics, which is currently the best theory we have for describing the fundamental particles and their interactions.

The ongoing LHC RUN II is expected to produce four times more Higgs boson candidates that will allow us to further study the new particle properties.

The most promising way to study the properties of the Higgs boson is via its decays to into two Z bosons which in turn each decay into an oppositely charged pair of electrons or muons, as they have the lower level of background noise.

In the standard model the Higgs and its associated field are predicted to have a spin of 0. This means that, unlike electomagnetism, they lack directionality. Further Higgs production will allow us to confirm this hypothesis.

A more powerful LHC could also reveal whether the Higgs has siblings. For example one popular way to extend the standard model is a theory called supersymmetry, which specifies a minimum of five types of Higgs boson.

Another open question is the determination of the rate with which the Higgs boson is produced via different mechanisms, and its comparison with the standard model predictions.

We currently stand at the cross roads of either achieving a more thorough understanding of the SM Higgs mechanism, or the perhaps more exciting prospect of discovering new physics phenomena, and is to this questions that my research will be addressed.

As such it will have a profound and lasting impact on our understanding of the fundamental nature of matter and expand humanity’s understanding of the fundamental laws of nature.


Higgs 4 lepton

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.

I 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 François 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.


Electron Reconstruction

The remarkable discovery of the Higgs boson in the experimentally harsh LHC environment would not have been possible without the deep understanding of the detector performance and optimisation of the reconstruction and identification algorithms.

An electron is reconstructed using energy deposits in the calorimeter (clusters), matched with tracks that provide information on the particle’s origin and direction and therefore of its momentum

I have been playing a leading role in the area electron performance and co-ordinated the development of the new electron reconstruction algorithm used by the ATLAS experiment in the Higgs discovery.

This improved electron reconstruction resulted of 30% in the expected sensitivity for the Higgs discovery in the H → ZZ(*) → 4l channel.

Publications

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Journal articles

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Journal articles

Conference proceedings papers

  • Aaboud M, Aad G, Abbott B, Abdinov O, Abeloos B, Abhayasinghe DK, Abidi SH, AbouZeid OS, Abraham NL, Abramowicz H , Abreu H et al (2019) ATLAS Collaboration. Nuclear Physics A, Vol. 982 (pp 985-1009) RIS download Bibtex download
  • Aaboud M, Aad G, Abbott B, Abdallah J, Abdinov O, Abeloos B, Abidi SH, AbouZeid OS, Abraham NL, Abramowicz H , Abreu H et al (2017) ATLAS Collaboration. Nuclear Physics A, Vol. 967 (pp 942-964) RIS download Bibtex download
  • Angerami A (2017) Measurements of photo-nuclear jet production in Pb + Pb collisions with ATLAS. Nuclear Physics A, Vol. 967 (pp 277-280) View this article in WRRO RIS download Bibtex download
  • Aad G, Abbott B, Abdallah J, Abdinov O, Abeloos B, Aben R, Abolins M, AbouZeid OS, Abramowicz H, Abreu H , Abreu R et al (2016) ATLAS Collaboration. Nuclear Physics A, Vol. 956 (pp 922-944) RIS download Bibtex download
  • Anduaga X (2013) Search for new signals in lepton pairs and photon pairs with the ATLAS detector. Proceedings of Science, Vol. 2012-July RIS download Bibtex download
  • Anduaga X (2011) Search for resonances in the diphoton channel at the ATLAS experiment of the Large Hadron Collider. Proceedings of Science, Vol. 2011-July RIS download Bibtex download
  • Anduaga X (2010) Commissioning and performance of the ATLAS muon, electron, tau and B-physics triggers with 7 TeV collisions at the LHC. 30th Physics in Collision Symposium, PIC 2010 RIS download Bibtex download
  • Abolins M, Adragna P, Aleksandrov E, Aleksandrov I, Amorim A, Anderson K, Anduaga X, Aracena I, Asquith L, Avolio G , Backlund S et al (2008) Integration of the trigger and data acquisition systems in ATLAS. Journal of Physics: Conference Series, Vol. 119(2) (pp 022001-022001) RIS download Bibtex download
  • F-Martin T, Abolins M, Adragna P, Aleksandrov E, Aleksandrov I, Amorim A, Anderson K, Anduaga X, Aracena I, Asquith L , Avolio G et al (2008) Event reconstruction algorithms for the ATLAS trigger. Journal of Physics: Conference Series, Vol. 119(2) (pp 022022-022022) RIS download Bibtex download
  • Dos Anjos A, Abolins M, Achenbach R, Adorisio C, Adragna P, Aharrouche M, Aielli G, Al-Shabibi A, Aleksandrov I, Alexandre G , Aloisio A et al (2008) The DAQ/HLT system of the ATLAS experiment. Proceedings of Science, Vol. 70 RIS download Bibtex download
  • Krepouri A, Bachas K, Anastopoulos C, Nicolaidou R, Petridou C & Sampsonidis D (2006) The performance of the ATLAS innermost MDT muon precision tracker in cosmic rays and in positron and muon beams. 2006 IEEE Nuclear Science Symposium Conference Record, 29 October 2006 - 1 November 2006. RIS download Bibtex download
Research group
Professional activities
  • Holder of the Royal Society University Research Fellowship at the University of Sheffield.  2015-Today
  • Holder of the Leverhulme Trust Early Career Fellowship at the University of Sheffield.  2013-2015