7/13/2005The 8th ACFA Daegu, Korea 1 T.Yoshioka (ICEPP), M-C.Chang(Tohoku), K.Fujii (KEK), T.Fujikawa (Tohoku), A.Miyamoto (KEK), S.Yamashita (ICEPP), on behalf of ACFA-SIM-J Group Realistic Particle Flow Algorithm for GLD Contents : 1. Introduction 2. Procedure of PFA - Small Clustering - Gamma Finding - Track Matching 3. Results 4. Summary

7/13/2005The 8th ACFA Daegu, Korea 2 Introduction - Most of the important physics processes studied in the future linear collider experiments have multi-jets in the final state. → Precise Jet reconstruction is essential. - Since the momentum resolution of the charged particle is much better than the energy resolution of the calorimeter, we use Trackers for charged particles Calorimeters for neutral particles for Jet reconstruction. → Particle Flow Algorithm (PFA) - In this talk, we present a performance of the PFA using a full simulator of GLD named Jupiter.

7/13/2005The 8th ACFA Daegu, Korea 3 - End view Thanks to Y.Yamaguchi (Tsukuba) - Side view Barrel Tower Front : 210cm Endcap Inner R : 40cm Endcap Tower Front Z : 270cm Calorimeter Geometry in Jupiter 40 cm 270 cm 210 cm - Consists of tower structure.

7/13/2005The 8th ACFA Daegu, Korea 4 Thanks to Y.Yamaguchi (Tsukuba) - Tower - # of Layers ECAL : 38 HCAL : Side view Barrel Tower Front : 210cm Endcap Inner R : 40cm Endcap Tower Front Z : 270cm Calorimeter Geometry in Jupiter 40 cm 270 cm 210 cm Full One Tower ECAL + HCAL ECAL HCAL

7/13/2005The 8th ACFA Daegu, Korea 5 Thanks to Y.Yamaguchi (Tsukuba) - Cell - Cell Size EM : 4cm x 4cm HD : 12cm x 12cm Can be changed easily. - Tower - # of Layers ECAL : 38 HCAL : Side view Barrel Tower Front : 210cm Endcap Inner R : 40cm Endcap Tower Front Z : 270cm Calorimeter Geometry in Jupiter 40 cm 270 cm 210 cm Full One Tower ECAL + HCAL 27 X 0 6.1λ ECAL HCAL

7/13/2005The 8th ACFA Daegu, Korea 6 Energy Deposit in a Cell ECALHCAL - Z → qq-bar(q =

7/13/2005The 8th ACFA Daegu, Korea 7 PFA Procedure 1.Small Clustering (collect fired cells with its neighbors) → Define thrust and broadening for each small cluster. 2. Gamma Finding (Separate gamma/e to hadron) → Small Cluster based. 3. Cluster-Track Matching (Separate charged to neutral) → Calorimeter Cell based. Note: → Cheating method is used for charged hadrons in the Endcap region. → Assuming the remaining clusters be neutral hadrons. Flow to make PFObject - Current Scheme of the PFA

7/13/2005The 8th ACFA Daegu, Korea 8 Small Clustering (1) Find the “starting cell” among those “fired cell” in ECAL and HCAL which contains the highest energy deposition. (2) From the “starting cell”, find its “fired” neighbor cells to form a small cluster. Starting Cell (Highest energy cell) Neighbor Cells “Fired” = edep>50keV If the cluster energy exceeds 50MeV(before calibration), the clustering is stopped.

7/13/2005The 8th ACFA Daegu, Korea 9 Small Cluster Distributions Number of hits in a small cluster Small Cluster Energy - Z → qq-bar(q =

7/13/2005The 8th ACFA Daegu, Korea 10 Variables for Small Cluster - Energy-weighted Thrust & Broadening Center of the small cluster Thrust axis (n) Direction from the center to each hit (Xi) - Thrust axis n is defined as to maximize the T. Small Cluster

7/13/2005The 8th ACFA Daegu, Korea 11 Thrust and Broadening ThrustBroadening - Z → qq-bar(q =

7/13/2005The 8th ACFA Daegu, Korea 12 Gamma Finding Procedure (1)Fit the longitudinal profile of the energy deposit of a small cluster as an electromagnetic cascade. (2) Make a cut on the distance from the nearest track. (3) Compare energy sum between HCAL/ECAL within a tube. Details of the gamma finding algorithm/performance are described by next speaker (T.Fujikawa) So far, we achieved Efficiency : 60%, Purity : 99%.

7/13/2005The 8th ACFA Daegu, Korea 13 Track Matching Procedure - 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 Track Calorimeter input position Hit Cells distance 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

7/13/2005The 8th ACFA Daegu, Korea 14 Track Matching Procedure (1)Sum up calorimeter cell energies within a tube for a track (Ecluster). (2) If Ecluster > Etrack x (0.4 x nsigma + 1), stop the clustering for the track. If not, perform (1) for each track. (We assume the calorimeter resolution of 40%.) (3) Widen the tube radius (only a Rstep) and perform (1) and (2) again. (4) Perform (1)-(3) until the tube radius reach the max radius (Rmax). Parameters (nsigma, Rstep and Rmax) should be optimized. - More detail of the procedure…

7/13/2005The 8th ACFA Daegu, Korea 15 Distance Distribution ECALHCAL - Z → qq-bar(q =

7/13/2005The 8th ACFA Daegu, Korea 16 Efficiency/Purity - Efficiency/Purity of Track Matching is checked by cheating method. Efficiency : 86.4% Purity : 82.2%

7/13/2005The 8th ACFA Daegu, Korea 17 Event Display e+e+ e-e- Just in order to get a feeling of current procedure…

7/13/2005The 8th ACFA Daegu, Korea 18 Event Display Z → qq-bar Red : pion Yellow : gamma Blue : neutron e+e+ e-e-

7/13/2005The 8th ACFA Daegu, Korea 19 Event Display At first, charged hadrons in Endcap region are removed by cheating method.

7/13/2005The 8th ACFA Daegu, Korea 20 Event Display After Endcap cheating…

7/13/2005The 8th ACFA Daegu, Korea 21 Event Display In the next, e/gamma like clusters are removed by “Gamma Finding”.

7/13/2005The 8th ACFA Daegu, Korea 22 Event Display After e/gamma finding… Note Efficiency : 60% Purity : 99%

7/13/2005The 8th ACFA Daegu, Korea 23 Event Display Then, Then, calorimeter hits near the extrapolated track are collected by “Track Matching”.

7/13/2005The 8th ACFA Daegu, Korea 24 Event Display Remaining clusters are assumed to be neutral hadrons.

7/13/2005The 8th ACFA Daegu, Korea 25 Z Energy Resolution Sum up Calorimeter EnergyParticle Flow Algorithm

7/13/2005The 8th ACFA Daegu, Korea 26 Change Calorimeter Cell Size EM : 4cm x 4cm HD : 12cm x 12cm EM : 1cm x 1cm HD : 1cm x 1cm - In the current method, the resolution is not improved so much by fine segmentation. → Another method should be considered in this case. (tracking and vertex finding in calorimeter, etc…)

7/13/2005The 8th ACFA Daegu, Korea 27 Can We Improve More? p n K pi KL e/gamma : EC cheating : e/gamma finding : track matching : remaining hits Particle ID of hit cell - Current e/gamma finding efficiency is ~60%. → Improve efficiency while keeping high purity. - There are still ~10% charged hadrons after track matching. → Optimize parameters (Tube radius etc…)

7/13/2005The 8th ACFA Daegu, Korea 28 e/gamma Contamination Track matching purity Track matching purity w/o e/gamma - If e/gamma contamination are removed (by cheating), the track matching purity improve from 82.2% to 92.2%. → Z energy resolution would also be improved.

7/13/2005The 8th ACFA Daegu, Korea 29 Track Matching Performance - Collected calorimeter energy minus track energy - Lower tail indicates that current tube radius is narrow (not efficiently collected energy). 1. Optimize parameters. 2. Energy dependent tube radius?

7/13/2005The 8th ACFA Daegu, Korea 30 Summary and Future - Realistic Particle Flow Algorithm (PFA) for GLD is developed and the performance is checked. - Gamma Finding : Efficiency : 60%, Purity : 99% (Details will be presented by T.Fujikawa) - Track Matching : Efficiency : 86.4%, Purity : 82.2% - Z energy resolution : 40%/sqrt(E) - Goal : 30%/sqrt(E) of Z energy resolution. - Treat Endcap properly. - Improve gamma finding efficiency. - Optimize track matching parameters.