The reconstruction method for GLD PFA Tomoaki Fujikawa (Tohoku Univ.) Keisuke Fujii (KEK), Akiya Miyamoto (KEK), Satoru Yamashita (ICEPP), Tamaki Yoshioka (ICEPP) on behalf of acfa-sim-j members 15/Nov./2005 ECFA ILC Workshop @ Vienna

ECFA ILC Workshop @ Vienna Introduction So far, we have been concentrating on the understanding about PFA and on the development of reconstruction tools. We would like to introduce some of the PFA tools in our algorithm, especially Photon finder and Satellite hits finder. (The cut values/combination of these tools have not been optimized yet) 15/Nov./2005 ECFA ILC Workshop @ Vienna

ECFA ILC Workshop @ Vienna Flow of GLD PFA MIP & IL position finding m finding (cheated) Small clustering & Photon finding Electron finding (not implemented yet) CHD finding (track matching) NHD clustering Throwing away satellite hits Summarized by T.Yoshioka (previous speaker) 15/Nov./2005 ECFA ILC Workshop @ Vienna

ECFA ILC Workshop @ Vienna Small clustering Merge hits with its fired neighbors. (Energy density is considered in this method.) We call it “small cluster”  see T.Yohioka’s slides 15/Nov./2005 ECFA ILC Workshop @ Vienna

ECFA ILC Workshop @ Vienna Photon finding Photon finding is based on collected small clusters (take r = 5.7cm, h = 30cm tube region). Use following information to choose photon clusters: Distance from the nearest track Shower longitudinal energy profile TOF information Shower length (NHits vs. Energy correlation) We prepared 2 types of cut combination for “Large” photon clusters (E larger than ~1.5GeV) and for “Small” one. (It is difficult to use information 2. to find “Small” photon clusters) 15/Nov./2005 ECFA ILC Workshop @ Vienna

Distance from the nearest track Reject (small) clusters if distance from the nearest track is close. This cut reject large number of charged particle origin clusters. Yellow: photon Red: others ECAL small clusters in Z -> qqbar @ 91.2GeV 15/Nov./2005 ECFA ILC Workshop @ Vienna

Shower longitudinal energy profile 3 GeV 10 GeV 5 GeV 1 GeV Take projection of total energy deposit along longitudinal axis (IP to cluster position) and fit it by Gamma-distribution function. The result of chi-square/ndf is used to choose photon clusters. This method cannot work well for low momentum particles. Chi2/ndf single track test (yellow:photon, red:pion) 15/Nov./2005 ECFA ILC Workshop @ Vienna

ECFA ILC Workshop @ Vienna TOF information Calculate temporary velocity using cluster position and TOF information (R/TOF). This cut can reject slow neutral hadrons, low momentum charged particles and satellite hits. (TOF information of each hit are being smeared by =1.3nsec Gaussian-distribution in our current simulator.) Yellow: photon Red: others ECAL small clusters in Z -> qqbar @ 91.2GeV 15/Nov./2005 ECFA ILC Workshop @ Vienna

Shower length (NHits vs. Energy) EM shower length proportional to Log(E) while HD shower length proportional to E. In addition, because of transverse EM shower size is not so different for each energy and layer thickness is much thinner than transverse cell size, correlation between NHits and Energy can be used to choose EM shower. Blue: photon Red: others ECAL clusters in Z -> qqbar @ 91.2GeV 15/Nov./2005 ECFA ILC Workshop @ Vienna

Treatment of satellite hits Hadron particles make many satellite hits… charged hadron satellites  should be thrown away (tracker information is used) neutral hadron satellites  can be thrown away if it is not “core” Use TOF and energy density information to find satellite hits (clusters). 15/Nov./2005 ECFA ILC Workshop @ Vienna

TOF of remaining clusters Use temporary velocity. Charged hadron satellites make a peak at slow velocity region. (Left peak in red one consists of charged hadron hits (clusters) and right one consists of remaining photons.) Light blue: n,K0L Red : others Remaining clusters in Z -> qqbar @ 91.2GeV 15/Nov./2005 ECFA ILC Workshop @ Vienna

ECFA ILC Workshop @ Vienna Energy density Calculate the density of energy deposition around cluster center (taking a r=20cm sphere, this is not optimized) We regard low energy density clusters as satellites. Light blue: n,K0L Red : others Remaining clusters in Z -> qqbar @ 91.2GeV 15/Nov./2005 ECFA ILC Workshop @ Vienna

ECFA ILC Workshop @ Vienna Summary Current total energy efficiencies are photon=85.2%, chd=84.4%(94.9% with including satellites), nhd=60.5% and cluster purities are Pphoton=92.2%, Pchd=91.9% (89.0% with including satellites), Pnhd=62.2%. (chd  pi,p,K, nhd  n,K0L)  Pink one should be higher and blue one should be lower xx  (total xx E in xx clusters)/(“true” total xx E in CAL) (efficiency) Pxx  (total xx E in a cluster)/(total E of cluster) (purity) (both  and P values are E-weighted one) 15/Nov./2005 ECFA ILC Workshop @ Vienna

ECFA ILC Workshop @ Vienna Next plan The combination of cut values should be optimized  use Likelihood method Study good neutral hadron clustering method Energy, position, cluster feature dependent energy calibration for (neutral) hadron clusters. Implementation of electron finder. 15/Nov./2005 ECFA ILC Workshop @ Vienna

ECFA ILC Workshop @ Vienna Back up slides 15/Nov./2005 ECFA ILC Workshop @ Vienna

Clustering efficiency and purity Our definition of “clustering” efficiency and purity is: xx  (energy deposit by a xx particle in this cluster)/(“total” energy deposit by “this” xx particle in CAL) Pxx  (total energy deposit by a xx particle in this cluster)/(total energy deposit of this cluster) for each “truly xx-like” clusters. (“truly xx-like” means “xx particle’s energy fraction in this cluster is dominant in this cluster”) For example, “truly photon-like” clusters in our “reconstructed” photon clusters are used in the estimation of photon of photon clusters. (results are energy weighted one) 15/Nov./2005 ECFA ILC Workshop @ Vienna

Statistical correction in TOF cut TOF (velocity) error decreases by const./Sqrt(nhits) in statistically. Its effect is considered in our method. Blue: photon Red: others ECAL small clusters in Z -> qqbar @ 91.2GeV 15/Nov./2005 ECFA ILC Workshop @ Vienna

Clustering efficiency vs. TOF This plot shows the result of clustering efficiency vs. temporary velocity of reconstructed NHD + Satellite clusters. (NHD origin energy deposit is weighted) Slow velocity clusters are satellite-like (low clustering efficiency) even if it is NHD origin one. Can regard as “satellites” Remaining clusters in Z -> qqbar @ 91.2GeV 15/Nov./2005 ECFA ILC Workshop @ Vienna

Clustering efficiency vs. E-density Can regard as “satellites” Remaining clusters in Z -> qqbar @ 91.2GeV 15/Nov./2005 ECFA ILC Workshop @ Vienna