Many extensions of the Standard Model of particle physics predict the existence of a pair of charged Higgs bosons H+ and H-. We search for charged Higgs bosons decaying into a tau lepton and a neutrino.  

People: Joakim Gradin, Alexander Madsen, Johann Collot

Public results of studies using 2011 data

  • Search for charged Higgs bosons decaying via H+->tau nu in ttbar events using 4.6 fb^-1 of collision data at sqrt(s)=7 TeV with the ATLAS detector ATLAS-CONF-2012-011 (Moriond 2012)
  • Search for a charged Higgs boson decaying via H+ to tau(lep)+nu in ttbar events with one or two light leptons in the final state using 1.03/fb of pp collision data recorded at sqrt(s) = 7 TeV with the ATLAS detector ATLAS-CONF-2011-151 (HCP 2011)

 

 
 

 

W and Z associated Higgs production, H decaying to 2 photons

NO MORE ACTIVITIES in this field since 2008

  • Fairouz Malek
  • Bertrand Brelier (PhD)
  • Georges Azuelos (Université de Montréal)


We search for a SM Higgs boson, in the mass range 110-140 GeV, decaying to two photons, produced in association with a Z or a W boson. This channel is used to enhance the significance of the Standard Model Higgs discovery potential and to improve the precision in the evaluation of the ZZH and WWH couplings.
Three distinct signal topologies are considered separately, where H -> photon photon  is accompanied by:

  • (i) a lepton, resulting mostly from the WH channel; 
  • (ii) high missing transverse momentum, largely due to the ZH channel;  
  • (iii) dijets with invariant mass in the range 70-100 GeV, when the gauge bosons decay hadronically.  

The main backgrounds are prompt photon photon , Wphoton  -> e nu photon , and photon  + jet. Therefore, electron/photon discrimination, photon-jet rejection and missing E_T reconstruction are of outmust importance in our analyzes. For good statistical precision, the study is performed for an integrated luminosity of 100 fb-1, but low instantaneous luminosity of 1033 cm-2 s-1 is assumed and the statistical significance is evaluated for 30 fb-1.

CP violation and B-Physics studies

NO MORE ACTIVITIES in this field since 2005

Fairouz Malek et Sébastien Viret (now permanent position  at IPN-Lyon)

B Physics - CP violation

Reconstruction and analysis of B(s,d) --> J/psi eta 

 

Reconstruction and analysis of Bd --> J/psi K*0 
  • Reconstruction in Bd --> J/psi (mu mu) K*0 (Ks, pi0) and ATLAS Calorimeter performance for identification of gamma, pi0 and eta particles at low transverse momentum : ATL-PHYS-2001-023

The ATLAS group at LPSC exists since November 1991.presambler

Initially, it worked mainly on the R&D and then on the buiding of the (barrel) presampler of the LAr calorimeter. This activity ended up in 2003 after 3 years of production, tests and integration of the expected 64 modules. Starting from 1998, the group activities were enriched with the study, and later the building, of the proximity cryogenic system of the electromagnetic calorimeter. The integration and comissioning of this infrastructure ended up in 2007.

Starting in 1998, Johann Collot was the LAr calorimeter software coordinator for 4 years. This lead to a lot of software and computing activities in the group, which are still developing nowadays.

presampler1The physics topics studied by the group members over the years are numerous. Among those which are not active any more: Majorana neutrinos, B physics, Higgs search and  Z', W' decaying leptonically search.

There are also discontinued activities on the software side: the calorimeter identifiers and the simulation of the LAr LVL1 trigger.

On the other hand, Fairouz Malek, designed in 2004 by IN2P3, has been the scientific responsible of the LCG-France project for ten years.

 

The group had been created by Johann Collot who remained its leader until 2003, when he became the LPSC director. It was then Fairouz Malek who took the leadership of the group, until 2012.

 

 

 

 

 

Update: August 12th, 2016

Members

  • Fairouz Malek, Elisabeth Petit, Jan Stark, senior physicistes
  • Thomas Meideck, PhD (2015)
  • Jonathan Brown,Post-Doc (2012-2014). Now in Lyon.
  • Alex Chauvin,  M2 internship (mars-june 2014)
  • Quentin Buat (PhD until July 31st,2013). Now in Vancouver.
  • Bao Tran Le (PhD until 19 March, 2013). Now in Vietnam

What is it about?

The Standard Model of particle physics has been very successful so far but leaves some questions open, one of them being the huge difference between the energy scales of gravitation and the three other fondamental forces. A way to solve this issue would be the addition of extra space dimensions. A possible signature probing their existence at high energy colliders is by virtual exchange of gravitons. The production would occur through gluon fusion or quark-antiquark annihilation and the decay in pairs of leptons or photons (gg/qqbar -> G -> leptons/gamma gamma). Notes, publications, theses  and talks are given below.

Publications

  • Search for resonances in diphoton events at sqrt(s)=13 TeV with the ATLAS detector, arXiv :1606.03833 [hep-ex], submitted to JHEP (2016).
  • Search for high-mass diphoton resonances in pp collisions at sqrt(s) = 8 TeV with the ATLASdetector. Phys. Rev. D 92,032004.
  • Search for extra dimensions in diphoton events from proton–proton collisions at sqrt(s)= 7 TeV in the ATLAS detector at the LHC, New J. Phys. 15 043007 (2013).
  • Search for extra dimensions using diphoton events in 7 TeV proton-proton collisions with the ATLAS detector, Phys. Lett. B710, 538 (2012)
  • Courrier CERN, Octobre 2012.

Public and Internal Notes

  • Search for scalar diphoton resonances with 15.4 ifb of data collected at sqrt(s)=13 TeV in 2015 and 2016 with the ATLAS detector, ATLAS-CONF-2016-059 :https ://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLASCONF-2016-059.
  • Search for resonances in diphoton events with the ATLAS detector at sqrt(s)=13 TeV, ATLASCONF-2016-018 : https ://cds.cern.ch/record/2141568
  • Search for resonances in diphoton events at sqrt(s)=13 TeV with the ATLAS detector, CERNEP-2016-120
  • Search for resonances in diphoton events with the ATLAS detector at sqrt(s)=13 TeV, ATLASCONF-2016-018 (2015 data) : https ://cds.cern.ch/record/2141568.
  • Search for high-mass diphoton resonances in pp collisions at sqrt(s)= 8 TeV with the ATLAS detector. CERN-PH-EP-2015-043.
  • Search for high-mass diphoton resonances in pp collisions at sqrt(s)= 8 TeV with the ATLAS detector. ATL-COM-PHYS-2014-870
  • Search for Extra Dimensions in the Diphoton Final State using 20.3 fb−1 of pp Collisions recorded by the ATLAS detector at the LHC. ATL-COM-PHYS-2013-740.
  • Search for Extra Dimensions in the Diphoton Channel using 4.9 fb−1 of Proton-Proton Collisions recorded at 7 TeV with the ATLAS Detector. ATLAS-CONF-2012-08 :
    https ://cds.cern.ch/record/1460399.

Conferences

  • F. Malek, Search for a high mass diphoton resonance using the ATLAS detector, 5th International Conference on New Frontiers in Physics (ICNFP2016), Crete-Kolymbari, 6-14 July 2016.European Physical Journal Web of Conferences.
  • F. Malek, Non-SUSY Beyond Standard Model Searches : Recent Results from ATLAS and CMS, 4th Symposium on Prospects in the Physics of Discrete Symmetries (DISCRETE2014), 2-6 December 2014, London, UK.JoP : Conference Series 631 (2015) 01204 ATL-PHYS-PROC-2015-005.

Theses

  • Search for new phenomena in diphoton events with the ATLAS detector, Quentin Buat, defense: July 31st, 2013. TeL-00876625
  • Search for extra dimensions in diphoton channel with ATLAS experiment at LHC, Bao Tran Le, defense: March 19th,  2013, TeL-00805474