10/26/2006 JSPS Meeting @ KEK 1

Recent PFA Performance and Higgs Study using Kinematical Fit

JSPS Creative Scientific ResearchMonthly Meeting @ KEKOct. 26th, 2006

Tamaki Yoshioka ICEPP, Univ. of TokyoOn behalf of GLD Colleagues

10/26/2006 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.

10/26/2006 JSPS Meeting @ KEK 3

Geometry in Jupiter

Muon Detector

Solenoid

Hadron Calorimeter (HCAL)

Electromagnetic Calorimeter (ECAL)

TPC

VTX, IT

As of August 06

10/26/2006 JSPS Meeting @ KEK 4

229.8cm

349.4cm

299.8cm419.4cm

Readout Line =10cm

270cm

Endcap.InnerRadius=40cm

BarrelHD

BarrelEM

EndcapEM

EndcapHD

Barrel.InnerRadius=210cm

Barrel.HalfZ=280cm

210cm

280cm

Calorimeter Geometry in Jupiter

IP

10/26/2006 JSPS Meeting @ KEK 5

Calorimeter Structure

ECALW/Scinti./Gap

3/2/1 (mm) x 33 layers

HCALFe/Scinti./Gap

20/5/1 (mm) x 46 layers

Absorber

Active Layer

Current cell size :2x2cm

Can be changed.

10/26/2006 JSPS Meeting @ KEK 6

Realistic PFA

10/26/2006 JSPS Meeting @ KEK 7

Z-pole Event Display

End View Side View

- 2cm x 2cm tile (GLD backup solution) is used in this study.

10/26/2006 JSPS Meeting @ KEK 8

Particle Flow Algorithm for GLD

Flow of GLD-PFA

1.Photon Finding 2.Charged Hadron Finding3.Neutral Hadron Finding4.Satellite Hits Finding *Satellite hits = calorimeter hit cell which does not belong

to a cluster core

Note : Monte-Carlo truth information is used for muonand neutrino.

10/26/2006 JSPS Meeting @ KEK 9

Photon Likelihood

trkdis velocity meanlay

Edep/nhits chi2

- Five variables are selected to form the photon likelihood function.

Photon

Other

Output

PhotonOther

10/26/2006 JSPS Meeting @ KEK 10

Particle Flow Algorithm for GLD

Flow of GLD-PFA

1.Photon Finding 2.Charged Hadron Finding3.Neutral Hadron Finding4.Satellite Hits Finding *Satellite hits = calorimeter hit cell which does not belong

to a cluster core

Note : Monte-Carlo truth information is used for muonand neutrino.

10/26/2006 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).

Charged TrackCalorimeter input position

Hit Cellsdistance

ECAL

HCAL

- Tube radius for ECAL and HCAL can be changed separately.

- Calculate the distance for any track/calorimeter cell combination.

Extrapolated Track

Tube Radius

10/26/2006 JSPS Meeting @ KEK 12

Particle Flow Algorithm for GLD

Flow of GLD-PFA

1.Photon Finding 2.Charged Hadron Finding3.Neutral Hadron Finding4.Satellite Hits Finding *Satellite hits = calorimeter hit cell which does not belong

to a cluster core

Note : Monte-Carlo truth information is used for muonand neutrino.

10/26/2006 JSPS Meeting @ KEK 13

Neutral Hadron Likelihood- Four variables are selected to form the NHD likelihood function.

Neutral Hadron

Satellite Hits

velocity Edensity

Edep/nhits meanlayer

Output

Neutral Hadron

Satellite Hits

10/26/2006 JSPS Meeting @ KEK 14Next: 電子、陽電子衝突

e+

e-

Event Display

Yellow : Photon

Red, Green : Charged Hadron

Black, Blue : Neutral Hadron Z → qqbar @ 91.2GeV

10/26/2006 JSPS Meeting @ KEK 15

Yellow : Photon

Red, Green : Charged Hadron

Black, Blue : Neutral Hadron

Event Display

Gamma Finding

10/26/2006 JSPS Meeting @ KEK 16

Yellow : Photon

Red, Green : Charged Hadron

Black, Blue : Neutral Hadron

Event Display

Charged Hadron Finding

10/26/2006 JSPS Meeting @ KEK 17

Yellow : Photon

Red, Green : Charged Hadron

Black, Blue : Neutral Hadron

Event Display

Satellite Hits Finding

10/26/2006 JSPS Meeting @ KEK 18

Yellow : Photon

Red, Green : Charged Hadron

Black, Blue : Neutral Hadron

Event Display

Remaining : Neutral Hadron

10/26/2006 JSPS Meeting @ KEK 19

- Performance in the EndCap region is remarkably improved recently.- Almost no angular dependence : 31%/√E for |cos|<0.9.

All angle

- Z → uds @ 91.2GeV, tile calorimeter, 2cm x 2cm tile size

Jet Energy Resolution (Z-pole)

10/26/2006 JSPS Meeting @ KEK 20

cluster type e photon e chd e nhd Pphoton Pchd PnhdPhoton 93.6 1.88 18.5 87.21 3.57 7.53

CHD 2.44 85.8 12.8 1.31 93.8 3NHD 1.07 3.6 52.8 3.28 22.7 70.7

Satellite 2.86 8.74 15.8 10.20 63.9 24.8

Definition

Efficiency : exxx (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 e and P values are energy-weighted

Performance

- Energy-weighted Efficiency and Purity

10/26/2006 JSPS Meeting @ KEK 21

Jet Energy Resolution

- Jet energy resolution linearly degrades. (Fitting region : |cos|<0.9)

- Energy dependence of jet energy resolution.

10/26/2006 JSPS Meeting @ KEK 22

Linearity

- Good linearity. Jet energy can be corrected.

10/26/2006 JSPS Meeting @ KEK 23

Zh Study

10/26/2006 JSPS Meeting @ KEK 24

Typical Event Display

- ZH → h : Two jets from Higgs can be seen.

10/26/2006 JSPS Meeting @ KEK 25

Zh → h @ 350GeV

- Jet energy is corrected by an empirical formula obtained by Z → qqbar studies.- Selection Criteria

- 90 < Evis < 200 GeV - pt >20 GeV/c

Higgs Mass Visible Energy

Missing Mass

- Fast MC• w/o correction• w/ correction

10/26/2006 JSPS Meeting @ KEK 26

Kinematical Fit (2jet)- 6 Measured Variables

Jet1 : Ej1, j1, j1

Jet2 : Ej2, j2, j2 (Note : Ej1 > Ej2)- 3 Unmeasured Variables

Z0 : Ez, z, z

- 4 Constraintspj1cosj1sinj1pj2cosj2sinj2pZcosZsinZpj1sinj1sinj1pj2sinj2sinj2pZsinZsinZpj1cosj1pj2cosj2pZcosZEj1 + Ej2 + Ez – Ecm = 0

(Note: jet mass is fixed : pfit = √{Efit2

– (Emeas2 – pmeas

2)} )

→ 1C-fit can be performed.

10/26/2006 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.

10/26/2006 JSPS Meeting @ KEK 28

( × Br(h→bb)) Mh (GeV) Mh (MeV)

w/o kinfit 2.04% 117.5 124.8

w/ kinfit 1.89% 119.9 85.6

Fitted Results (2jet)

10/26/2006 JSPS Meeting @ KEK 29

Kinematical Fit (4jet)- 12 Measured Variables

Jet1 : Ej1, j1, j1, Jet2 : Ej2, j2, j2 (Higgs pair)

Jet3 : Ej3, j3, j3, Jet4 : Ej4, j4, j4 (Z0 pair) - 5 Constraintspj1cosj1sinj1pj2cosj2sinj2pj3cosj3sinj3pj4cosj4sinj4pj1sinj1sinj1pj2sinj2sinj2pj3sinj3sinj3pj4sinj4sinj4pj1cosj1pj2cosj2pj3cosj3pj4cosj4Ej1 + Ej2 + Ej3 + Ej4 – Ecm = 0Ej3 + Ej4 – √{(pfit,j3

+ pfit,j4) 2 + Mz2} = 0

(Note: jet mass is fixed (OPAL method)pfit = √{Efit

2 – (Emeas

2 – pmeas2)} )

→ 5C-fit can be performed.

10/26/2006 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.

10/26/2006 JSPS Meeting @ KEK 31

( × Br(h→bb)) Mh (GeV) Mh (MeV)

w/o kinfit

w/ kinfit

Fitted Results (4jet)

10/26/2006 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.