ATLAS ACC/CEA collaboration (on particle physics) Eric Lançon (CEA-Saclay/Irfu)

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1 ATLAS ACC/CEA collaboration (on particle physics) Eric Lançon (CEA-Saclay/Irfu)

2 ATLAS ACC/CEA collaboration since beginning of FCPPL Beijing Dec Pr. H. Chen Pr. F. Le Diberder B. Mansoulié 2

3 The ATLAS group of CEA-Saclay/Irfu ~40 people (physicists & postdocs) One of the founder institutes of ATLAS Involved in design and construction of Electromagnetic calorimeter Muon spectrometer Torroidal magnet Physics with leptons

4 ATLAS activities at CEA-Saclay/Irfu Standard Model Electromagnetic calorimeter trigger Muon reconstruction software Magnetic field map Muon alignment Grid & computing LHC upgrade B tagging W,Z bosons : mass, cross-section Di-boson couplings Higgs searches 4-leptons WW Top quark physics Common tools for analysis t quark mass, ttbar cross-section Exotics (Z, l*,...)

5 ATLAS thesis at CEA-Saclay/Irfu Since 2008, 3 Chinese students joined the group YU Jie/ 俞 : XU Chao/ : XIAO Meng/ :

6 Top quark pair production cross-section measurement Co-Thesis of YU Jie/ 俞 (Nanjing University), Oct to May 2011 Supervisors : S. Chen (Nanjing), B. Mansoulié (CEA-Saclay) Advisor : J. Schwindling (CEA- Saclay) Subject: Measurement of Top Pair Production Cross-Section in lepton + jets Channels in ATLAS at 7 TeV Original work : simultaneous b- tagging efficiency / σttbar measurement using 20 data Detailed presentation at 20 & 2011 FCPPL workshops Contributions to 3 internal and 2 conference ATLAS notes

7 YU Jie s PhD thesis Now postdoc position with Oklahoma State University Thesis defended on May 15th, 2011, at Nanjing University, first PhD thesis of China-CEA cooperation Available at: cdsweb.cern.ch/record/

8 W/Z + Jets production Co-Thesis of XU Chao/ (USTC), Started Feb., 2009 Advisers : Z. Zhao (USTC), E. Lançon (CEA-Saclay) Chao s presentation at FCPPL 2011 I. What is R jets Introduction of R jets Measurement of W/Z production ratio (RJets) as a function of Jet transverse energy Analysis of μ-decay channel II. Why R jets interesting By measuring R many systematic uncertainties present in the V+jets analyses cancel or are significantly reduced, small errors allow precise comparison with theoretical predictions Measurment of R in various kinematics and topological regimes, such as jet p is also sensitive to new physics Thesis defense : beg. June 2012 at USTC 3

9 RJets analysis status XU Chao key player of the analysis based on 20 data One conference note σ(w ( µ ν) + 1-jet) σ(z ( µ µ ) + 1-jet) η µ < 2.4, p Data Muon Channel Syst. uncertainty Total syst. stat. uncertainty MCFM µ T > 20 GeV 20 data only Ldt = 33 pb ATLAS Paper published Theory / Data ratio 1.5 PYTHIA MCFM ALPGEN Jet p Threshold [GeV] T 9

10 Search for exited leptons - I For excited lepton masses below compositeness scale, 3Wbody%mass(leptons+photon)%gives Λ = 2 TeV production dominated by contact interaction followed by subsequent electroweak decay of excited lepton into an ordinary lepton and a photon Production Cross section depends on compositeness scale Λ and Ml* Signature: 2 leptons + 1 photon ositeness%

11 Search for exited leptons - II Analysis strategy : 2-body mass (lepton+photon) narrow signal width 3-body mass (leptons+photon) excess if signal exist Events / 0 GeV 3 2 ATLAS s Preliminary -1 L dt = 4.8 fb = 7 TeV Data 2011 Z + γ Z + jets Bkg. uncertainty (m, Λ) = (0.2, ) TeV µ* (m (m, Λ) = (0.5, 9) TeV µ*, Λ) = (0.8, 8) TeV µ* 1 Distribution used: 3-body mass to set limit -1 avoid deciding which lepton to be paired with the photon m µ µ γ [GeV] still efficient to set limit when Ml* is close to Λ in which case the signal width method is more significant anti-z selection but main backgrounds Z+ɣ!and Z+jets 11

12 μ μ ɣ Persint event display (CEA-Saclay) Figure 4: Display of the event containing the highest µ + µ invariant mass: 890 GeV. The p T of the muons and photon are: 91, 84 and 165 GeV, respectively. The dimuon mass is 165 GeV, m µ1 = 721 GeV, and m µ2 = 491 GeV. 12

13 Search for exited leptons - Status Full 2011 data set analyzed (μ channel) 2 conference notes σ B(µ* µγ) [fb] 2 ATLAS Preliminary -1 L dt = 4.8 fb s = 7 TeV Observed limit Expected limit Expected ±1 σ Expected ±2 σ Λ = 2.1 TeV Λ = 5.0 TeV Λ = 8.0 TeV 1 paper m µ* [TeV] Λ [TeV] ATLAS Preliminary -1 L dt = 4.8 fb s = 7 TeV Observed limit Expected limit Expected ±1σ m µ* > Λ 8-1 CDF 370 pb m µ* [TeV] 13

14 Muon detector description & Higgs search Thesis of XIAO Meng/ (Nanjing University), CEA grant, started Oct. 20 Thesis adviser : S. Hassani (CEA-Saclay) Detailed presentation on Muon Final State radiation in Drell-Yann process by Meng next talk 14

15 Summary Very healthy 5 years collaboration : visits, post-docs., PhD thesis First common thesis submitted spring 2011, another to come in spring 2012 Wish to expand the collaboration through more integrated cooperations at group level 15