Main highlights in top physics group status since PRC:

- DESY-Hamburg:

  * A joint DESY-Aachen TopDilepton group has just been created. The idea is 
    to have a German working group for the dileptonic ttbar decay channel 
    towards a common physics note on cross section measurement with early data.

    People involved so far:
    From DESY: Achim Geiser, Dirk Dammann, Markus Marienfeld, Wolf Berenhoff, 
               Maria Aldaya

    From Aachen (IIIb): Heiko Geenen, Achim Stahl, Daiske Tornier, 
                        Martina Davids, Bastian Kargoll   



   * M. Marienfeld: Online/Offline ttbar dilepton monitoring 
      
     (1) The main goal is to have a muon trigger monitoring module 
         ('TopHLTDimuon') implemented as soon as possible, both for online 
         and offline DQM. A first version of the analyzer has been completed:
         - It works on HLT muon objects (L1&L3). 
         - Could operate at Online DQM *AS WELL AS* at Offline DQM level. 
         - The code has been successfully tested, but is NOT YET implemented.
         - Requested including it into the Offline DQM sequence as soon 
           as possible (BEFORE 2 TeV collisions..).
         - Since the code is working, the HLT muon group will be contacted 
           for the possibility of operation at Online level.

      (2) The 'TopDilepton' module, which runs within the Offline DQM sequence 
          since few weeks successfully, has been updated, but it is ot yet 
          clear when the changes will be applied in CMSSW.  


   * Dirk Dammann: Analysis towards the ttbar cross-section determination in 
     dimuon channel.

     - The analysis presented at the PRC has been updated for L=50pb-1 at
        sqrt(s)=7 TeV (*).         
     - It was presented at the Helmholtz Alliance workshop last week (12 Nov),
       as part of the talk given by Jasmin Gruschke on "Top-quark 
       pair-production cross-section measurement using early CMS data at 10 
       TeV".


   * Alex Flossdorf: 
     Analysis note on "Higher Order QCD Radiation in Top Pair Production" 
     just posted (19 Nov) on iCMS.



- DESY-Zeuthen:

  * Igor Marfin: Analysis towards the measurement of ttbar cross-section in the
    semileptonic channel and the calibration of btagging algorithms.

    First studies were presented at the HH Top Meeting (4 Nov): 
    - Event selection criteria was developed
    - Top candidate is reconstructed as the combination of the 3 reco jets with
      maximal total pT.
    - Investigating the use of two methods for cross-section determination:
      * simple counting of the events surviving the selection cuts
      * fit to the S+B 3-jet invariant mass distribution to obtain the number
        of signal events 

   
 


(*) As a reminder:

        - Event selection: 2 high-pT isolated muons, >= 2 high-pT jets, 
          Z-veto for ee, mumu, no cut on MET, no btagging
        - Kinematic reconstruction of ttbar events, making use of the fact that
          MET is due to the unobserved neutrinos and taking into account the 
          Wmass constraint.
        - Use of data-driven methods for background determination: 
          "Wrong-charge method": QCD and fake background for large invariant 
          masses can be described by looking into the equally-charged 
          distribution for muon pairs.
        - Prospects of validating btagging efficiency using reconstructed jets
          from ttbar events.