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Home page > Research topics > ATLAS > Research topics > La Nouvelle Physique

Search for new physics beyond the Standard Model

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The LAPP group is involved in two exotic analyses: one with di-photon final state, the other with di-electron final state

Di-photon resonance searches

Since 2013 our group is the leading driving force behind the ATLAS search for high-mass diphoton resonances. This analysis is a spin-off of the commitment to the measurement of the Higgs boson properties in its diphoton decay. This analysis was first performed using 8 TeV data, with a complete and exclusive implication of the LAPP group that developed all steps of the search, result and publication. In the first 13 TeV data an intriguing excess at a mass of about 750 GeV was observed, which caused a lot of excitement in theoretical community as well as public. Unfortunately in the 2016 data the 750 GeV excess was not confirmed. The group currently maintains an open activity in this area, especially planning the extension of the search in the mass region below 125 GeV, where the presence of additional resonances has a strong theoretical motivation in the context of models with extended Higgs sectors (NMSSM, 2HDM).

Contacts: Nicolas Berger, Rémi Lafaye

Relevant publications:

  • ATLAS Collaboration, Search for Scalar Diphoton Resonances in the Mass Range 65-600 GeV with the ATLAS Detector in pp Collision Data at sqrt(s) = 8 TeV, Phys. Rev. Lett. 113, 171801
  • ATLAS Collaboration, Search for resonances in diphoton events at sqrt(s)=13 TeV with the ATLAS detector, JHEP 09 (2016) 1
  • ATLAS Collaboration, Search for scalar diphoton resonances with 15.4 fb-1 of data collected at sqrt(s)=13 TeV in 2015 and 2016 with the ATLAS detector, ATLAS-CONF-2016-059
  • Movie: Inside CERN BBC Horizon

Dielectron resonance searches

Since the beginning of the data-taking in 2009 our group has participated in the searches for new resonances in the dielectron final state. No excess over the standard model predictions is found in the current dataset but increasingly stringent limits were set, raising from 1 TeV in 2009 to 4.5 TeV for the SSM Z’ (a heavier cousin of the SM Z bozon) in the latest Run-2 results. We also are working on reinterpretaion of these and other related exotics searches (e.g. lepton+MET, dibosons, dijets etc. final states) in a wider framework of models with extended gauge symmetries.

Contact: Tetiana Hryn’ova

Relevant publications:

  • Search for new high-mass resonances in the dilepton final state using proton-proton collisions at sqrt(s)=13 TeV with the ATLAS detector, ATLAS-CONF-2016-045
  • Search for high-mass new phenomena in the dilepton final state using proton-proton collisions at sqrt(s) =13 TeV with the ATLAS detector, PLB 761 (2016) 372-392
  • Search for high-mass dilepton resonances in pp collisions at sqrt(s) = 8 TeV with the ATLAS detector, PRD 90, 052005 (2014)
  • Search for high-mass resonances decaying to dilepton final states in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector JHEP 1211 (2012) 138
  • Search for dilepton resonances in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector, Phys.Rev.Lett. 107 (2011) 272002
  • Search for high mass dilepton resonances in pp collisions at sqrt(s)=7 TeV with the ATLAS experiment Phys.Lett.B700:163-180,2011

Combinaison de recherches exotiques

New phenomena could occur in more than one final state. Individual analyses only constrain a subset of the model parameters or have a limited sensitivity to them, but combination of channels leads to much stronger simultaneous constraints, exploiting their complementarity as shown in Figure.

Contact: Tetiana Hryn’ova

Relevant publications:

  • Combination of searches for heavy resonances decaying into bosonic and leptonic final states using 36  fb−1 of proton-proton collision data at √s=13  TeV with the ATLAS detector; Phys. Rev. D 98 (2018) 052008