Roberto Chierici CNRS (Lyon) Top physics in France Roberto Chierici CNRS (Lyon)

Outline ATLAS CMS Top physics at the LHC and the impact of France Top-LHC France Collaboration and synergies Main areas of contribution A glance to the main physics topics Outlook and future venues CMS LPC Clermont LPSC Grenoble IPNL Lyon CPPM Marseille IPHC Strasbourg LPNHE Paris IRFU Saclay

Top physics in the year(s) of a scalar boson Direct constraints on the SM The t, W and H masses are linked at loop level Direct access to parameters of the SM (mt, Vtb) Other stringent tests of SM (QCD in d/dX, couplings, CPT invariance,…) Vacuum stability very sensitive to mt A particle with unique characteristics No bound states, EWK+flavour physics at best ! τ(had)~h/QCD~2 10-24 s, τ(top)~h/top~5 10-25 s The Higgs boson couples preferentially to top (yt ~1) Fantastic window for direct searches of new physics t~t~→tt+X, g~g~→tt(tt)+X, t’t’→bbWW, ZZtt, b’b’→ttWW, tttt, … Important to study total/differential cross sections and the “environment” of top production Direct indication of NP possible (e.g. charge asymmetries)

The impact of France in top physics at the LHC The impact/involvement of France in the top physics program at the LHC in the last years has been tremendous Top group convenership: [2011-2012] [2008-2009] Coordination of physics subgroups Mass: [2009/10] [2008/9] Properties: [2013-] [2011/12] Single top: [2008/11] Cross section: [2011] Top resonances: [2012/13] LHC combinations (+creation of the TOPLHCWG): [2011-] Single top LHC combination: Coordination of/contribution to tools/objects (for the top group) Trigger for top: B-tagging : Jet/MET: e/μ: Monte Carlos: SW/Validation : Lyon Clermont Physics coordination activities (ATLAS+CMS) Saclay Clermont Saclay Strasbourg Grenoble Lyon Strasbourg Lyon Lyon LHC Clermont Lyon Marseille Strasbourg Tools’ development in ATLAS+CMS Clermont Lyon Paris Marseille Paris Lyon Saclay Grenoble Paris

First top-LHC France meeting https://indico.in2p3.fr/conferenceTimeTable.py?confId=7693#20130321

First top-LHC France meeting The aim is to bring together the French scientific community working on the subject Precision measurements Search for new physics in the top sector Why? The project is many-fold Find synergies and form collaborations, if possible, among labs Find a natural forum where EXP and TH can discuss and collaborate in France Essential for the physics program of both searches and measurements Increase the visibility of the French labs working on top physics in the HEP French community Contribute together to the LHC combination activities Create a collaborative “top community”, get to know each other, form students The format of the venue is chosen to be very informal (friendly !), and talks go beyond the mere presentation of a result Direct comparisons of results (ATLAS vs CMS) Interactive sessions (ATLAS vs CMS vs TH) A lot of discussion time !

First top-LHC France meeting Format was 1.5 days, with ample time left for discussion in between presentations

Statistics and analyses’ strategy since 2010 Recorded O(10 M) top quarks Improvements in: Trigger Luminosity JES B-tagging Object reconstruction 2012 Analyzed O(1 M) top pair events 2011 2010 Top-pair “environment” …+searches Rare processes tt+X Evidence Inclusive quantities Differential cross sections …+searches …+searches …+searches Structure of the Wtb vertex Charge asymmetries Spin structure Total cross sections

Top pair cross section All top pair final states are investigated ℓ(e,μ,)+jets, ℓℓ(all but )+jets and fully hadronic final states Combined experimental uncertainty now below 5% Challenging approximate NNLO computations (TH error: 5-9%) Cross section is used to either extract the top pole mass or the value of S. Full NNLO predictions for top-pair production now available Contributions from France are very important See talks in this session Czakon, Fiedler, Mitov, arXiv:1303.6254 arXiv:1208.2671 PRD 85 112007 (2012) 7 TeV 7 TeV Saclay Strasbourg Paris Strasbourg Marseille Clermont Paris 9

Top pair differential cross sections Marseille Test top physics in different portion of phase space Important test of pQCD, test MC models Sensitive to the presence of new physics Control systematics for searches/other measurements Check simple variables (leptons, jets) but also more complex ones, with full reconstruction of the events pT(t), m(tt), pT(tt), y(tt),… Fully unfolded results via migration matrices EPJC (2013) 73:2261 Particularly relevant: charge asymmetry Check the Tevatron disagreement on fwd-bkw asymmetry Different definition at the LHC Non zero SM asymmetry induced by interferences between ISR and FSR Use fully leptonic events Asymmetry can be measured by just using leptons Saclay Strasbourg ATLAS CONF 2012-057 CMS PAS TOP-12-010 AC = 0.057  0.024(stat)  0.015(syst) ASM = 0.006  0.002

Spin structure in tt JHEP 1206 (2012) 088 Marseille The spin structure of the top decay is transmitted to its daughters By investigating the helicity of Ws from top we can test the V-A structure of the coupling. Use d/dcosθ*ℓ: While top quarks are produced individually unpolarized in top pair production, their spins are correlated Can be studied via the angular distributions of the leptons from W decay Saclay Marseille Strasbourg CMS PAS TOP-12-004 The polarization of W and top is also studied in single top production ATLAS-CONF-2012-133 Grenoble

Single top Studied in the all the decay channels MVA employed, use of data whenever possible to constrain all backgrounds Strategy: likelihood fit to an NN discriminant (t-channel) or a BDT output (Wt) Cut based for the s-channel Clermont Grenoble PLB 717 (2012) 330-350 Phys. Lett. B 716 (2012) 142-159 Wt(7 TeV) = 16.8  2.9 (stat)  4.9 (syst) pb t-channel(7 TeV) = 83  4 (stat)+20-19 (syst) pb ATLAS CONF-2011-118 s-channel (7 TeV)<26.5 pb @95% CL Grenoble Clermont t-channel(8 TeV) = 95  2 (stat)  18 (syst) pb Direct involvement in single top LHC combinations |Vtb|>0.75 @95% CL

Top mass Indirect determination: exploit the dependence of tt on mt to extract the top pole mass Direct methods: leptonic final states Neutrino method: calculate the probability of each neutrino pair configuration, then use MC templates ME method: use full kinematic info available Hadronic channels (l+jets , all-jets ) Minimize global chi2 to associate light and b jets to form candidate top Template fit to extract the top mass Saclay ATLAS-CONF-2011-054 mt-pole = 166.4+7.8-7.3 GeV contributions from IRFU, LPNHE Saclay Clermont Strasbourg Paris Eur Phys J C72 (2012) 2202 mtop = 172.5  0.4(stat)+1.5(syst) GeV ATLAS-CONF-2012-030 ATLAS-CONF-2012-082 mtop = 174.9  2.1 (stat)  3.8 (syst) GeV mtop = 175.2  1.6(stat)+3.1-2.8(syst) GeV

Combining precision measurements The TOPLHCWG was started for combining precision measurements in top physics at the LHC, but also as the natural forum for discussion with the TH community Define observables to combine and a common language to present the measurements Agree on method for performing the combination, and the way results are presented Document the work in correspondence of major updates and conferences Natural forum at the LHC for discussing ideas/issues on top physics Natural bridge to the theory community and the TeVEWWG for world averages First combinations we agreed to perform… Top pair and single top t-channel cross sections, top mass, W helicities in top-pair …and topics for discussion and common agreements Cross-experiment efforts on JetMET, radiation and b-tag systematics Common definition of particle level quantities (leptons/jets/acceptances/top quarks!) The group is very active by now A few preparatory closed meetings, at least two open sessions per year (Next one 18-19 April !) Open mailing list: lhc-toplhcwg@cern.ch, well integrated in the LPCC CERN structure The French community is very well represented Coordination and single top combination Lyon Clermont

Some highlights Top mass NEW ! tt cross section W helicities, |V|tb Single top t-channel in the works…. Other quantities under discussion and study (differential distributions, spin correlation, tt+V, Wt channel, helicities in single top,….)

Resonant top-pair production Several new physics models predict the presence of new heavy particles decaying into top-pairs Need to reconstruct the top pair system Event’s kinematics strongly depend on the mass of the intermediate state Low mass analyses: standard tt reconstruction High mass analyses: no lepton isolation, top tagging techniques Combine the two Resolved Boosted ATLAS-CONF-2012-136 Clermont Lyon Marseille JHEP12 (2012) 015 ℓ+jets ℓ+jets resolved + boosted mZ’(gKK) > 1.7(1.9) TeV @95%CL

Other searches in top physics Clermont Grenoble t+b resonances Just a few examples List likely non exhaustive. Other searches in t/tt+MET also ongoing… PRL109 (2012) 081801 m(W’)> 1130 GeV @95% CL Marseille b’, tttt, T5/3, … Saclay PLB 718 (2013) 1284-1302 Clermont t’→Wb JHEP 1204 (2012) 069 mt'> 656 GeV @95% CL m(b',T5/3) <0.67 TeV @ 95% CL

New projects for the near future Groups will continue their efforts in the current analyses and prepare/refine at best for the re-start at an higher energy New activities are anyway emerging Higgs and top ! ttH is a fundamental benchmark for the SM Interest in ttbb, ttWW/ZZ, ttττ, tt Searches ! Differential distributions/NP in single top ANR Grenoble+Clermont+Lyon(TH) Inclusive searches for new physics (e.g. by using effective theory approaches) ANR Strasbourg Precision measurements ! Constrain systematic sources with data New methods for making precision physics with a much larger amount of data (e.g. top mass with J/Ψ+l) Clermont Lyon Marseille Saclay Strasbourg Clermont Grenoble Saclay Strasbourg Lyon

Conclusions The top physics program at the LHC is very vibrant and extremely important to complete our understanding of the SM (also after the confirmation of the Higgs boson) or to find hint of physics beyond it The French community has contributed a lot to this physics program in the last years in both the ATLAS and the CMS Collaborations The impact has been large both at analysis and coordination level We are working to form a real top community in France who can share ideas/projects and set-up long-term national collaborations among experimentalists and theorists

TOP2014 The top-LHC France community will propose France as host for the organization of the TOP2014 Conference (as we did for 2013) Most important yearly topical conference on top physics New appealing proposals are in the works Hopefully with a very good chance to get it this year… Proposals made for 2013 20

Example of input for discussion: systematic errors JES uncert.s: use the same classification Tevatron used TH uncert.s Method specific differences are acceptable