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

2. 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

3. 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~ s, τ(top)~h/top~ 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)

4. 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: [ ] [ ]
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

5. First top-LHC France meeting

6. 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 !

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

8. 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

9. 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:
arXiv:
PRD (2012)
7 TeV
7 TeV
Saclay
Strasbourg
Paris
Strasbourg
Marseille
Clermont
Paris 9

10. 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
CMS PAS TOP
AC =  0.024(stat)  0.015(syst)
ASM =  0.002

11. 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
The polarization of W and top is also studied in single top production
ATLAS-CONF
Grenoble

12. 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)
Phys. Lett. B 716 (2012)
Wt(7 TeV) = 16.8  2.9 (stat)  4.9 (syst) pb
t-channel(7 TeV) = 83  4 (stat) (syst) pb
ATLAS CONF
s-channel (7 TeV)<26.5 CL
Grenoble
Clermont
t-channel(8 TeV) = 95  2 (stat)  18 (syst) pb
Direct involvement in single top LHC combinations CL

13. 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
mt-pole = GeV
contributions from IRFU, LPNHE
Saclay
Clermont
Strasbourg
Paris
Eur Phys J C72 (2012) 2202
mtop =  0.4(stat)+1.5(syst) GeV
ATLAS-CONF
ATLAS-CONF
mtop =  2.1 (stat)  3.8 (syst) GeV
mtop =  1.6(stat) (syst) GeV

14. 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 April !)
Open mailing list: well integrated in the LPCC CERN structure
The French community is very well represented
Coordination and single top combination
Lyon
Clermont

15. 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,….)

16. 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
Clermont
Lyon
Marseille
JHEP12 (2012) 015
ℓ+jets
ℓ+jets
resolved
+ boosted
mZ’(gKK) > 1.7(1.9)

17. 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)
m(W’)> 1130 CL
Marseille
b’, tttt, T5/3, …
Saclay
PLB 718 (2013)
Clermont
t’→Wb
JHEP 1204 (2012) 069
mt'> 656 CL
m(b',T5/3) < % CL

18. 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

19. 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

20. 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

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