Recent PFA Performance and Higgs Study using Kinematical Fit

1. Recent PFA Performance and Higgs Study using Kinematical Fit JSPS Creative Scientific Research Monthly Meeting @ KEK Oct. 26th, 2006 Tamaki Yoshioka ICEPP, Univ. of Tokyo On behalf of GLD Colleagues JSPS Meeting @ KEK

2. Introduction • Most of the important physics processes to be studied in the ILC • experiment have multi-jets in the final state. • → Jet energy resolution is the key in the ILC physics. • The best energy resolution is obtained by reconstructing • momenta of individual particles avoiding double counting among • Trackers and Calorimeters. • - Charged particles (~60%) measured by Tracker. • - Photons (~30%) by electromagnetic CAL (ECAL). • - Neutral hadrons (~10%) by ECAL + hadron CAL (HCAL). • → Particle Flow Algorithm (PFA) • In this talk, general scheme and performance of the GLD-PFA, • using the GEANT4-based full simulator (Jupiter),will be presented. JSPS Meeting @ KEK

3. Geometry in Jupiter Solenoid TPC Hadron Calorimeter (HCAL) VTX, IT Muon Detector Electromagnetic Calorimeter (ECAL) As of August 06 JSPS Meeting @ KEK

4. Calorimeter Geometry in Jupiter Readout Line =10cm 349.4cm BarrelHD 229.8cm BarrelEM 210cm 270cm EndcapHD Barrel.InnerRadius=210cm EndcapEM Endcap.InnerRadius=40cm IP Barrel.HalfZ=280cm 419.4cm 280cm 299.8cm JSPS Meeting @ KEK

5. Calorimeter Structure Active Layer Absorber Current cell size : 2x2cm Can be changed. ECAL W/Scinti./Gap 3/2/1 (mm) x 33 layers HCAL Fe/Scinti./Gap 20/5/1 (mm) x 46 layers JSPS Meeting @ KEK

6. Realistic PFA JSPS Meeting @ KEK

7. Z-pole Event Display End View Side View - 2cm x 2cm tile (GLD backup solution) is used in this study. JSPS Meeting @ KEK

8. Particle Flow Algorithm for GLD Flow of GLD-PFA • Photon Finding • Charged Hadron Finding • Neutral Hadron Finding • Satellite Hits Finding • *Satellite hits = calorimeter hit cell which does not belong • to a cluster core Note : Monte-Carlo truth information is used for muon and neutrino. JSPS Meeting @ KEK

9. Photon Likelihood - Five variables are selected to form the photon likelihood function. velocity meanlay trkdis Photon Other Output chi2 Edep/nhits Other Photon JSPS Meeting @ KEK

10. Particle Flow Algorithm for GLD Flow of GLD-PFA • Photon Finding • Charged Hadron Finding • Neutral Hadron Finding • Satellite Hits Finding • *Satellite hits = calorimeter hit cell which does not belong • to a cluster core Note : Monte-Carlo truth information is used for muon and neutrino. JSPS Meeting @ KEK

11. Charged Hadron Finding • Basic Concept : • Extrapolate the charged track and calculate a distance between • a calorimeter hit cell and the extrapolated track. Connect the cell • that in a certain tube radius (clustering). Extrapolated Track • Calculate the distance • for any track/calorimeter • cell combination. HCAL Tube Radius Hit Cells • Tube radius for ECAL • and HCAL can be changed • separately. distance ECAL Calorimeter input position Charged Track JSPS Meeting @ KEK

12. Particle Flow Algorithm for GLD Flow of GLD-PFA • Photon Finding • Charged Hadron Finding • Neutral Hadron Finding • Satellite Hits Finding • *Satellite hits = calorimeter hit cell which does not belong • to a cluster core Note : Monte-Carlo truth information is used for muon and neutrino. JSPS Meeting @ KEK

13. Neutral Hadron Likelihood - Four variables are selected to form the NHD likelihood function. Output velocity Edensity Neutral Hadron Satellite Hits Edep/nhits meanlayer Neutral Hadron Satellite Hits JSPS Meeting @ KEK

14. e+ e- Yellow : Photon Red,Green : Charged Hadron Black,Blue : Neutral Hadron Z → qqbar @ 91.2GeV Event Display JSPS Meeting @ KEK Next: 電子、陽電子衝突

15. Event Display Yellow : Photon Red,Green : Charged Hadron Black,Blue : Neutral Hadron Gamma Finding JSPS Meeting @ KEK

16. Event Display Yellow : Photon Red,Green : Charged Hadron Black,Blue : Neutral Hadron Charged Hadron Finding JSPS Meeting @ KEK

17. Event Display Yellow : Photon Red,Green : Charged Hadron Black,Blue : Neutral Hadron Satellite Hits Finding JSPS Meeting @ KEK

18. Event Display Yellow : Photon Red,Green : Charged Hadron Black,Blue : Neutral Hadron Remaining : Neutral Hadron JSPS Meeting @ KEK

19. Jet Energy Resolution (Z-pole) - Z → uds @ 91.2GeV, tile calorimeter, 2cm x 2cm tile size All angle • Performance in the EndCap region is remarkably improved recently. • Almost no angular dependence : 31%/√E for |cosq|<0.9. JSPS Meeting @ KEK

20. Performance - Energy-weighted Efficiency and Purity Definition Efficiency : xxx  (total xx E in collected hits)/(true xxx total E in CAL) Purity : Pxxx (total xxx E in a cluster)/(total E in a cluster) xxx = Photon, CHD, NHD, Satellite both  and P values are energy-weighted JSPS Meeting @ KEK

21. Jet Energy Resolution - Energy dependence of jet energy resolution. - Jet energy resolution linearly degrades. (Fitting region : |cosq|<0.9) JSPS Meeting @ KEK

22. Linearity - Good linearity. Jet energy can be corrected. JSPS Meeting @ KEK

23. Zh Study JSPS Meeting @ KEK

24. Typical Event Display • ZH → nnh : Two jets from Higgs can be seen. JSPS Meeting @ KEK

25. Zh → nn h @ 350GeV - Fast MC • w/o correction • w/ correction Higgs Mass Visible Energy • - Jet energy is corrected by an empirical • formula obtained by Z → qqbar studies. • - Selection Criteria • 90 < Evis < 200 GeV • pt >20 GeV/c Missing Mass JSPS Meeting @ KEK

26. Kinematical Fit (2jet) • - 6 Measured Variables • Jet1 : Ej1, qj1, jj1 • Jet2 : Ej2, qj2, jj2 (Note : Ej1 >Ej2) • - 3 Unmeasured Variables • Z0 : Ez, qz, jz • 4 Constraints • pj1cosjj1sinqj1 + pj2cosjj2sinqj2 + pZcosjZsinqZ = 0 • pj1sinjj1sinqj1 + pj2sinjj2sinqj2 + pZsinjZsinqZ = 0 • pj1cosqj1 + pj2cosqj2 + pZcosqZ = 0 • Ej1 + Ej2 + Ez – Ecm = 0 • (Note: jet mass is fixed : pfit = √{Efit2– (Emeas2 – pmeas2)} ) • → 1C-fit can be performed. JSPS Meeting @ KEK

27. Fitted Results (2jet) Prob > 0.02 • Higgs mass resolution is slightly improved. … But, • Peak at prob=1 indicates the fitting didn’t work well. JSPS Meeting @ KEK

28. Fitted Results (2jet) JSPS Meeting @ KEK

29. Kinematical Fit (4jet) - 12 Measured Variables Jet1 : Ej1, qj1, jj1, Jet2 : Ej2, qj2, jj2 (Higgs pair) Jet3 : Ej3, qj3, jj3, Jet4 : Ej4, qj4, jj4 (Z0 pair) - 5 Constraints pj1cosjj1sinqj1 + pj2cosjj2sinqj2 + pj3cosjj3sinqj3 + pj4cosjj4sinqj4 = 0 pj1sinjj1sinqj1 + pj2sinjj2sinqj2 + pj3sinjj3sinqj3 + pj4sinjj4sinqj4 = 0 pj1cosqj1 + pj2cosqj2 + pj3cosqj3 + pj4cosqj4 = 0 Ej1 + Ej2 + Ej3 + Ej4 – Ecm = 0 Ej3 + Ej4 – √{(pfit,j3+ pfit,j4) 2 + Mz2} = 0 (Note: jet mass is fixed (OPAL method) pfit = √{Efit2– (Emeas2 – pmeas2)} ) → 5C-fit can be performed. JSPS Meeting @ KEK

30. Fitted Results (4jet) Prob > 0.02 • Higgs mass resolution is slightly improved. … But, • Peak at prob=1 indicates the fitting didn’t work well. JSPS Meeting @ KEK

31. Fitted Results (4jet) JSPS Meeting @ KEK

32. Summary • Realistic PFA has been developed using the GEANT-4 based full simulator of the GLD detector. • Jet energy resolution is studied by using Z->qq events. ILC goal of 30% has been achieved for Z-pole events. • ZH study based on current PFA performance is now ongoing. Kinematical fitting is employed to get a better performance, but it didn’t work well so far. JSPS Meeting @ KEK