Calorimeter in front of Calorimeter in front of MUChMUCh

Mikhail ProkudinMikhail Prokudin

OverviewOverview

►Geometry and acceptanceGeometry and acceptance►Reconstruction procedureReconstruction procedure

Cluster finder algorithmsCluster finder algorithms Preliminary reconstruction qualityPreliminary reconstruction quality

►Conclusions Conclusions

GeometryGeometry

► Size: 2.5Size: 2.5××2.0 m2.0 m22

2020××16 modules16 modules 25 readout channels per 25 readout channels per

modulemodule►2.52.5××2.5 cm2.5 cm22 cell size cell size

7900 channels total7900 channels total

► 1.5 m distance from 1.5 m distance from targettarget 5 5 ̶ ̶ 4545°° angular acceptance angular acceptance

GeometryGeometry

► 70 layers70 layers 1.0 mm tungsten1.0 mm tungsten 1.5 mm plastic1.5 mm plastic

►175 mm total thickness175 mm total thickness►Space for readout?Space for readout?

20X20X00

0.95 nuclear interaction 0.95 nuclear interaction lengthlength

Energy resolutionEnergy resolution

►non zero constant term non zero constant term because calorimeter a little bit because calorimeter a little bit short for 16 GeV photonsshort for 16 GeV photons

%4.1%6.7

EE

dE

Reconstruction procedure.Reconstruction procedure.A problemA problem

►5 5 ̶ ̶ 4545°° angular acceptance angular acceptance►2.52.5××2.5 cm2.5 cm22 cell size cell size

Common reconstruction algorithms will not work.

Reconstruction procedureReconstruction procedureA roadmapA roadmap

► Cluster formationCluster formation Maximum locationMaximum location

►Exclude ones due to Exclude ones due to charged trackscharged tracks

Formation of Formation of preclusterprecluster►number of cells near number of cells near

local maximumlocal maximum

Cluster=preclusters Cluster=preclusters with common cellswith common cells

► Cluster fittingCluster fitting First approximationFirst approximation

►calibrationcalibration►S-curves libraryS-curves library

Fitting procedureFitting procedure►showershower librarylibrary►Fitting algorithmFitting algorithm

LegendLegend► Can use currentCan use current► Easy to doEasy to do

technical issuetechnical issue

► Hard to doHard to do impossible?impossible?

► RemoveRemove

Precluster formation. Precluster formation. RequirementsRequirements

►High occupancy environmentHigh occupancy environment Minimize use of energy dependent conditionsMinimize use of energy dependent conditions

►Huge variation of occupancy over Huge variation of occupancy over calorimeter surfacecalorimeter surface

►Different cluster sizes for different impact Different cluster sizes for different impact anglesangles

►small clusters for low impact angles, large for high small clusters for low impact angles, large for high impact anglesimpact angles

Ideal case: cluster size as a parameterIdeal case: cluster size as a parameter

► Should use shower shapeShould use shower shape but without any librarybut without any library

► Fast!Fast!

Precluster formationPrecluster formation► ProcedureProcedure

► several other algorithms several other algorithms was analyzedwas analyzed

local maximumlocal maximum 2x2 maximum matrix2x2 maximum matrix center of gravity of 2x2 center of gravity of 2x2

maximum matrix (maximum matrix (☆☆)) ellipseellipse

► center of ellipse located center of ellipse located on line from center of on line from center of calorimeter to found calorimeter to found center of gravitycenter of gravity

sort all cells on square sort all cells on square intersect with ellipseintersect with ellipse

preclusterpreclustern cells with n cells with

maximum intersection maximum intersection square square X, cm

Y, cm

Ephoton=16 GeV, Angle=35°

Precluster formationPrecluster formation

► ParametersParameters cluster sizecluster size

►keep as low as possiblekeep as low as possible

semiaxes of ellipsesemiaxes of ellipse distance from center distance from center

of mass to ellipse of mass to ellipse centercenter

X, cm

Y, cm

9 cell cluster

2×2 cluster

Ephoton=16 GeV, Angle=35°

Cluster sizeCluster size

16 GeV photons

2x2 7 9

Calibration is Calibration is completecomplete

will not discuss a technical will not discuss a technical issuesissues

Reconstruction quality.Reconstruction quality.A procedureA procedure

►Need an estimation of reconstruction quality Need an estimation of reconstruction quality for understanding of physics performancefor understanding of physics performance How heavy may be a system for which we still How heavy may be a system for which we still

have acceptable reconstruction quality?have acceptable reconstruction quality?► ProcedureProcedure

For each MC photon on calorimeter surfaceFor each MC photon on calorimeter surface►photon born near primary vertexphoton born near primary vertex►with energy > 0.5 GeVwith energy > 0.5 GeV

Find appropriate maximumFind appropriate maximum► invert procedure for maximum exclusioninvert procedure for maximum exclusion

Build a preclusterBuild a precluster and find its energyand find its energy Reconstructed: |EReconstructed: |Erecoreco-E-EMCMC|<2*(Energy resolution)|<2*(Energy resolution)

Reconstruction qualityReconstruction quality

C+C 25 GeV

GeVAverage energy deposition per event

Preliminary

GeVAverage energy deposition per event

GeVAverage energy deposition per eventC

u+

Cu

25

GeV

Au

+A

u 2

5 G

eV

GeVAverage energy deposition per event

GeVAverage energy deposition per eventA

u+

Au 8

GeV

Au

+A

u 2

5 G

eV

ConclusionsConclusions

►Proposal of calorimeter in front of Proposal of calorimeter in front of MUCh is presentedMUCh is presented

►A cluster finder algorithm is developedA cluster finder algorithm is developed small cell size and large impact anglesmall cell size and large impact angle

►Calibration is completeCalibration is complete►Estimation of reconstruction quality is Estimation of reconstruction quality is

presentedpresented Au+Au 25AGev: (very) limited Au+Au 25AGev: (very) limited

performanceperformance Cu+Cu 25AGeV and lighter: worksCu+Cu 25AGeV and lighter: works