MuCh layout optimization studies

1. MuCh layout optimization studies • Outline • Geometries studied • Reconstruction and analysis software • Analysis results • Summary Evgeny Kryshen (PNPI) Mikhail Ryzhinskiy (PNPI)

2. Studied geometries Compact geometry for LMVM studies 5 GEM-like stations 3 layers per station 1 cm active gas volume Modules Modules Monolithic 25.6x25.6 cm2 51.2x51.2 cm2 15th CBM Collaboration Meeting, 13 April 2010

3. Segmentations 15th CBM Collaboration Meeting, 13 April 2010

4. Polarized meson generator Generates polarized vector mesons assuming Gaussian rapidity shape and termal pt distribution. Both dielectron and dimuon channels are available. Helicity and Collins-Soper reference frames for polarization. Possibility to use box distribution in rapidity and pt. • Available methods: • SetPDGType (Int_t pdg) • SetMultiplicity (Int_t mult) • SetDistributionPt (Double_t T=0.176) • SetDistributionY (Double_t y0=1.987, • Double_t sigma=0.228) • SetRangePt (Double_t ptMin=0, Double_t ptMax=3) • SetRangeY (Double_t yMin=0, Double_t yMax=4) • SetAlpha (Double_t alpha=0) • SetRefFrame (Frame_t frame=kColSop) • SetDecayMode (DecayMode_t decayMode=kDiMuon) • SetBox (Bool_t box) Developed by Evgeny Kryshen This generator can be used instead of Pluto input file.  production in central Au+Au @ 25 AGeV 10000 events with embedded 15 +- per event STS:8 hits MuCh:(Nst – 2) hits (3 hits on the last station) 2 to primary vertex < 3.0 15th CBM Collaboration Meeting, 13 April 2010

5. Reconstruction & analysis software • Reconstruction software: • Ideal STS digitizer; • Ideal STS hit finder; • L1 STS track finder and fitter • Realistic MuCh digitizer with spot size 1.5 mm; • MuCh hit finder with simple clustering for a set of charge thresholds (R=0.00; 0.05; 0.10; 0.15; 0.20); • MUCH tracking type: branching • MUCH tracking merger type: nearest hit Qthr = RQmax • Analysis library cbmroot/analysis/much (Developed by E. Kryshen): • CbmPolarizedGenerator – generation of polarized vector mesons with Pluto-like kinematics • CbmAnaMuonCandidate – particles which passed trigger selection criteria • CbmAnaDimuonCandidate – pairs of CbmAnaMuonCandidates • CbmAnaDimuonAnalysis – selection of CbmAnaMuonCandidates • CbmAnaDimuonHisto – invariant mass analysis and event mixing 15th CBM Collaboration Meeting, 13 April 2010

6. Analysis results Monolithic: 15th CBM Collaboration Meeting, 13 April 2010

7. Analysis results Modules 51.2x51.2 cm2: 15th CBM Collaboration Meeting, 13 April 2010

8. MuCh hit finder results No threshold Threshold = 0.20 Some improvements in hit finder needed 15th CBM Collaboration Meeting, 13 April 2010

9. Absorber thickness study • Simulation features: • module dimensions: 51.2 x 51.2 cm • module thickness: 1 cm (3GEM-like) • spot radius: 1.5 mm (3GEM-like) • fine segmentation: • 1 station: r<50 cm: 2x2 mm; r>50 cm: 4x4 mm • 2 station: 4x4 mm • 3-5 station: 16x16 mm • simple cluster deconvolution algorithm with 10% threshold Variation of individual absorber thickness Variation of total thickness Variation of individual thicknesses (4 station option) Done by Evgeny Kryshen 15th CBM Collaboration Meeting, 13 April 2010

10. Conclusions and next steps 15th CBM Collaboration Meeting, 13 April 2010 Conclusions: • First steps towards MuCh layout optimization were performed; • 48 options of the layout were studied and values for  reconstruction efficiency and S/B ratio were obtained for all studied layouts; • Threshold of 0.2Qmax seems to be the best option in all cases; this value allows to decrease the station inefficiency by 9-10%; • It is possible to reduce number of channels by factor of 2 for module geometry keeping efficiency and S/B on the same level; • From the efficiency point of view the current absorber thicknesses seems to the best option; • However, the increase of total absorber thickness causes raise of S/B by factor of 2 compared to the current version; Next steps: • Perform much more accurate study (make comparison to the ideal cases); • Study geometries with straws; • Investigate TRD as a last MuCh station; • Study other LMVM and charmonium production; • Realistic straw digitization and hit finding algorithms (in collaboration with A. Zinchenko); • Further investigation of cluster deconvolution algorithms; • Parameter tuning;