1. Calorimeter in front of MUCh Mikhail Prokudin

2. Overview ► Geometry and acceptance ► Reconstruction procedure  Cluster finder algorithms  Preliminary reconstruction quality ► Conclusions

3. Geometry ► Size: 2.5 × 2.0 m 2  20 × 16 modules  25 readout channels per module ► 2.5 × 2.5 cm 2 cell size  7900 channels total ► 1.5 m distance from target  5 ̶ 45 ° angular acceptance

4. Geometry ► 70 layers  1.0 mm tungsten  1.5 mm plastic ► 175 mm total thickness ► Space for readout?  20X 0  0.95 nuclear interaction length  Energy resolution ► non zero constant term because calorimeter a little bit short for 16 GeV photons

5. Reconstruction procedure. A problem ► 5 ̶ 45 ° angular acceptance ► 2.5 × 2.5 cm 2 cell size Common reconstruction algorithms will not work.

6. Reconstruction procedure A roadmap ► Cluster formation  Maximum location ► Exclude ones due to charged tracks  Formation of precluster ► number of cells near local maximum  Cluster=preclusters with common cells ► Cluster fitting  First approximation ► calibration ► S-curves library  Fitting procedure ► shower library ► Fitting algorithm Legend ► Can use current ► Easy to do  technical issue ► Hard to do  impossible? ► Remove

7. Precluster formation. Requirements ► High occupancy environment  Minimize use of energy dependent conditions ► Huge variation of occupancy over calorimeter surface ► Different cluster sizes for different impact angles ► small clusters for low impact angles, large for high impact angles  Ideal case: cluster size as a parameter ► Should use shower shape  but without any library ► Fast!

8. Precluster formation ► Procedure ► several other algorithms was analyzed  local maximum  2x2 maximum matrix  center of gravity of 2x2 maximum matrix ( ☆ )  ellipse ► center of ellipse located on line from center of calorimeter to found center of gravity  sort all cells on square intersect with ellipse  precluster n cells with maximum intersection square X, cm Y, cm E photon =16 GeV, Angle=35 °

9. Precluster formation ► Parameters  cluster size ► keep as low as possible  semiaxes of ellipse  distance from center of mass to ellipse center X, cm Y, cm 9 cell cluster 2 × 2 cluster E photon =16 GeV, Angle=35 °

10. Cluster size 16 GeV photons 2x279

11. Calibration is complete will not discuss a technical issues

12. Reconstruction quality. A procedure ► Need an estimation of reconstruction quality for understanding of physics performance  How heavy may be a system for which we still have acceptable reconstruction quality? ► Procedure  For each MC photon on calorimeter surface ► photon born near primary vertex ► with energy > 0.5 GeV  Find appropriate maximum ► invert procedure for maximum exclusion  Build a precluster  and find its energy  Reconstructed: |E reco -E MC |<2*(Energy resolution)

13. Reconstruction quality C+C 25 GeV GeV Average energy deposition per event Preliminary

14. GeV Average energy deposition per event GeV Average energy deposition per event Cu+Cu 25 GeV Au+Au 25 GeV

15. GeV Average energy deposition per event GeV Average energy deposition per event Au+Au 8 GeV Au+Au 25 GeV

16. Conclusions ► Proposal of calorimeter in front of MUCh is presented ► A cluster finder algorithm is developed  small cell size and large impact angle ► Calibration is complete ► Estimation of reconstruction quality is presented  Au+Au 25AGev: (very) limited performance  Cu+Cu 25AGeV and lighter: works