Reconstruction neutral decay modes (E391) Doroshenko M.(KEK) E391 collaboration Outlines: Data summary Analysis strategy Reconstruction K3p,K2p,Kgg decays Example of veto study Conclusion

Data summary  Beam time: 18 Feb – 1 July 2004  Big amount of data ~110 Gb per one day run ~6 Tb – full statistics (~57 days)  Phys. trigger (N>=2)- 6 Tb (~57 days)  Cosmic- all time in off spill  Muon beam- ~300 Gb  Pi0 calibration- ~500 Gb

Data analysis strategy  Separation of the data One-day  Identifying of the main sources of background One week  Make a clear the sources of background  Test our MC  Test skimming procedure 1/3 data  Background estimation  Big statistic of MC Full data  Open signal box Blind analysis

Strategy for veto study  Try to use data sample for study veto-cut instead MC Correct ADC, TDC information Contain all effects  Pure signal and bgr samples Acc. loss + rejection power The same behavior is expected for K3p,K2p,Kgg  But… Back-splash, shower leakage, shower overlapping… depends on decay process (next order correction)

Reconstruction of the n-gamma event  Solve equations relative Z for each 2-clusters assuming mass of origin particle:  Choose combination with minimum  Error estimated on the base of the resolution

K π3 reconstruction (Raw spectrum) Mass K0, GeV Zdecay point,cm Pt,Gev/c P,Gev/c

K π3 :Combinatorial error Mass,GeV/c^2 Z1 – vertex with best (Err1 – error of vertex) Z2 – vertex with second (Err2 – error of vertex) 0.5

Pure K π3 signal sample  Cut points Zdecay – cm Pt K0<20 MeV/c < 3 Err1/z1<0.028 Err2/z2>0.029 Mass,GeV/c^2

K π2 reconstruction (Raw spectrum) Mass,GeV/c^2 Pt K0,GeV/c Pt pi0,GeV/c Zdec,cm

K π2 reconstruction(2) Pt pi0,GeV/c Zdecay,cm K3p MC K2p MC Zdecay,cm

K π2 pure signal sample  < 1.5 (best)  > 10 (second)  > 100 (third)  Err(Z1)/Z1<0.035  0.1<(E 1 -E 2 )/(E 1 +E 2 )<0.9  No border hit  Zdecay :  Pt K0 < 15 MeV/c  Beam size R<3.5 Background contamination ~4% mass K0,Gev/c^2

K π2 pure background sample  < 5 (best)  > 10 (second)  - exist (third)  No border hit Background contamination ~4% mass K0,Gev/c^2 DATA Kπ2 MC

Kgg reconstruction (Raw spectrum) Pt,Gev/c Zdec,cm Pt,Gev/c Angle, degree 11 22 

Kgg pure signal sample  No border hit  Pt < 50MeV/c  Zdecay : cm  Theta <20 degree  Dist g-g >40cm  Balance Egam < 0.5  Egam: 0.2-2GeV  Diff gamma timing<2ns DATA Kgg MC K3p MC K2p MC DATA Kgg MC K3p MC K2p MC Zdecay,cm Pt,Gev/c

Kgg pure background sample  No border hit  Pt>100MeV/c  Theta >25 deg  Diff gamma timing<2ns  Balance Egam <0.5  Dist g-g > 40cm DATA K3p MC K2p MC Kgg MC Theta,degree Pt,Gev/c Zdec,cm 100MeV/c 25 0

Example veto study: CC03 K3p K2p Kgg Cut point, MeV Acceptance lossS/N ratio

Conclusion  We can reconstruct good K3p,K2p,Kgg decay modes K3p decays  The missing the true pairing of the gammas led to bad reconstruction mass K2p  Lower mass tail comes from K3p decays. Kgg  Background near Charge veto from neutrons (see next report) For comparison of BR the further study is needed  Pure signal and bgr sample of K3p,K2p,Kgg decays can be used for further veto study Purity w/o veto-cut on a level a few%  In future Study the acc. loss and bgr. rejection of the veto system using pure samples