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  • pg 1
									      Model ID @ 500 GeV



             Taikan Suehara
         ICEPP, The Univ. of Tokyo


Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 1
                      Three models
1. Inert Higgs
  – WIMP: hI (scalar)
  – Visible: h± (scalar)
2. SUSY
  – WIMP: c0 (fermion)
  – Visible: c± (fermion)
3. LHT
  – WIMP: AH (vector)
  – Visible: WH± (vector)
All give 2W + 2WIMP fs.
      Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 2
                 Analysis overview
•   √s = 500 GeV, 500 fb-1
•   full simulation
•   NO Initial polarization
•   Use same masses for all the models
    m(visible) = 231.57 GeV, m(WIMP)=44.03 GeV
•   Cross section is normalized (200fb & 40fb).
•   Use W hadronic decay (cut leptonic events)
•   Mass -> production angle calculation
•   Full SM background included
    Weighted to 500fb-1
       Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 3
          ILD detector & framework
                                        Event generation
                                    (signal, SM background)
                                               Stdhep event files
                                      Full-MC simulation              • Gridによる
                                           (GEANT4)                   大量のjob投入
                                               Hit, MC info(LCIO file)

                                           Event                • Tracking
                                                                • Particle Flow
  ILD detector (ILD00)                 reconstruction           • Flavor tagging etc.
• Vertex: Si pixel (3x2 layers)
                                               Particle information (ROOT tree)
• Silicon Tracker: 4 layers
• TPC(main tracker)                     Analysis          • Event weighting
• ECAL (0.5x0.5 cm tile, Si/W)                            • Separation cuts
• HCAL (3x3 cm tile, Sci/Fe)                              • Analysis (mass, angle…)
• Solenoid (3.5Tesla)
• Muon detector
          Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 4
                 Event generation
• Signal: JSF/physsim
  Structure
      • HELAS for helicity amp. calculation
      • BASES for numerical integration
      • SPRING for event generation
          – Pythia for quark fragmentation
  – ISR/Beamstrahlung included
  – ~0.1 M events for each process generated
• Background: SLAC (ILC standard sample)
  – whizard/pythia for all SM processes
  – ~14 M events in total (80-200 fb-1 for 2/4/6 fermion
    events, 0.1-1 fb-1 for eg/gg events)


      Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 5
                       Selection cuts
    BG suppression cuts “qqqq (non-b) + missing”

•   4-jet clustering (Durham)                •   each jet has >= 2tracks
•   # Track >= 20                            •   no > 25 GeV leptons
•   160 < Evis < 400 GeV                     •    |cosq|miss < 0.9
•   each Ejet > 5GeV                         •   sum |cosq| < 2.6
•   |cosq|jet < 0.99                         •   sum b-quark prob. < 1
•   unlike 3jet (yth,3 > 0.001)              •   kinematic fit converged
                                             •   65 < mW < 95 GeV




        Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 6
            Selection efficiency




• IH   eff: 59.8%, pur (200 fb): 78.6%, pur (40 fb): 42.3%
• SUSY eff: 58.3%, pur (200 fb): 77.7%, pur (40 fb): 41.0%
• LHT eff: 58.9%, pur (200 fb): 78.2%, pur (40 fb): 41.8%
Acceptable selection performance
    Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 7
   W energy distribution (for mass)




    MC truth (signal only)
                      Reco (kin-fitted)
MC & reco have a good correlation.
Difference of shapes (esp.WH) is not
used for the discrimination
in this analysis.
         Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 8
          Mass determination




Fitting: 3rd polynomial x Voigt function (10 params)

1.All 10 params free
2.Fix 8 params (except edge positions):
obtain errors of the edge positions

  Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 9
                    Mass resolution
• Edge positions from the fit: (MC: 96.32/174.78)
                      Low edge        High edge        Low edge        High edge
                      (200 fb)        (200 fb)         (40 fb)         (40 fb)

     IH               97.00 ± 0.13    174.22 ± 0.19 97.86 ± 0.38       176.22 ± 0.84
                      GeV             GeV           GeV                GeV

     SUSY             97.12 ± 0.15    173.46 ± 0.21 96.10 ± 0.54       176.02 ± 0.85
                      GeV             GeV           GeV                GeV
     LHT              96.94 ± 0.16    174.39 ± 0.10 99.56 ± 0.48       174.67 ± 0.34
                      GeV             GeV           GeV                GeV
• Masses (MC: 231.57/44.03)
                      Visible         WIMP             Visible         WIMP
                      (200 fb)        (200 fb)         (40 fb)         (40 fb)

     IH               232.28 ± 0.12 43.41 ± 0.58       232.40 ± 0.37 35.42 ± 2.78
                      GeV (0.12)    GeV (0.57)         GeV (0.39)    GeV (2.23)

     SUSY             232.59 ± 0.13 44.84 ± 0.63       231.04 ± 0.51 41.64 ± 2.63
                      GeV (0.14)    GeV (0.64)         GeV (0.50)    GeV (2.50)
      LHT             232.18 ± 0.13 43.18 ± 0.52        234.06 ± 0.35 33.91 ± 2.07
     Taikan Suehara, 15 th general meeting of ILC physics (Asia) wg., 2010/05/15 page 10
                      GeV (0.13)        GeV (0.50)      GeV (0.41)        GeV (1.56)
                    Production angle
• Production angle of the visible
  new particle can be calculated
  from W directions with masses
  of new particles and
  back-to-back assumption.
• The angle has spin info.
  but two-fold ambiguity (solution of 2nd equation) exists.




       Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 11
        Discriminant distribution




• The distribution looks reasonable.
• ~30% of the events cannot be used.
  (discriminant > 0 events selected)

    Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 12
                    1D distribution
                                                                       200fb




• MC & reco have reasonable correlation.
• Three models seem to be discriminated.

    Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 13
 2D distribution (2 solutions)
    IH                                        SUSY




     LHT                                      SMBG




Chi-square can be derived using these distributions.
 Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 14
                  Chi-square value
• One of the [IH, SUSY, LHT] + SMBG
   -> ‘Template’ (not randomized)
• One of the [IH, SUSY, LHT] +
  (SMBG with Poisson randomization)
  -> ‘Data’ (for other sample than template)
• (One of the [IH, SUSY, LHT] + SMBG)
  with Poisson randomization
  -> ‘Data (for the same sample as template)
• Normalization (needed or not?)
• Obtain difference/sqrt(template) bin by bin
• Square sum of them -> Chi-square value
     Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 15
  Chi-square result (200fb)
                          Number of bin = 210
    Data             IH               SUSY             LHT
    Template              preliminary
    IH               218              1009             1135


    SUSY             955              233              1144


    LHT              944              1323             268




Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 16
   Chi-square result (40 fb)
                          Number of bin = 210
    Data             IH               SUSY             LHT
    Template              preliminary
    IH               198              219              227


    SUSY             203              216              261


    LHT              198              311              211




Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 17
                           To Do




Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 18
Mass error on angle - MCvsReco




           IH, reco                                    IH, MCTruth

• chi-square value: 392 (w/o stat fluctuation)
  (cf. 210 bins) after normalization
• ‘Coefficient’ can be derived?
  (need comparison with other models)
    Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 19
Difference of distribution on masses?
• Plan to make 25 mass points
  (5 visible mass x 5 DM mass)
• m(visible): 231.57± 0.1x (error in 200fb)
                      ± 0.xx (error in 40fb)
• m(DM): 44.03 ± … same
• Possible in generator level
  almost impossible in full simulation
  -> use the ‘Coefficient’ (MC-reco ratio)?


    Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 20
                  Threshold scan
• Toy-MC?




   Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 21
          Summary (schedule?)
• Distribution of production angle looks
  reasonable.
• Three models can be separated well in 200fb
  – some separation in 40 fb
• Mass error should be considered
  – Need some more work (several days?)
• Threshold scan
  – Need some more work (a day?)
• Write a paper (several days?)
• A dedicated week means a calendar month??
    Taikan Suehara, 15th general meeting of ILC physics (Asia) wg., 2010/05/15 page 22

								
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