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EicRoot status report and calorimeter code development. A. Kiselev BNL, 06/20/2013. Contents. SVN repository Interface to EIC smearing generator Tracking detector “designer” tools. Overall status Update on track resolution studies Calorimeter code development & studies.

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a kiselev bnl 06 20 2013

EicRoot status report


calorimeter code development

A. Kiselev

BNL, 06/20/2013

  • SVN repository
  • Interface to EIC smearing generator
  • Tracking detector “designer” tools
  • Overall status
  • Update on track resolution studies
  • Calorimeter code development & studies


eic in fairroot framework
EIC in FairRoot framework
  • FairRoot is officially maintained by GSI; dedicated developers
  • O(10) active experiments; O(100) users


  • ROOT
  • VMC
  • VGM
  • “Boost” library


FairRoot external

package bundle


C++ classes


  • Interface to GEANT
  • Magnetic fields
  • Parameter database
  • MC stack handling



-> Make best use of FairRoot development

-> Utilize efficiently existing codes developed by EIC taskforce


eicroot availability usage
EicRoot availability & usage
  • SVN -> http://svn.racf.bnl.gov/svn/eic/eicroot
  • eic000* cluster -> /eic/data/FairRoot
  • README & installation hints
  • Few basic usage examples

-> MC points

End user point of view:




“PID” Pass

-> Hits

-> “Short” tracks

-> Clusters

-> “Combined” tracks

-> Vertices @ IP

  • ROOT files for analysis available after each step
  • C++ class structure is (well?) defined at each I/O stage


interface to eic smear
Interface to eic-smear
  • directly uses eic-smear library calls to import ASCII event files after MC generators …
  • … as well as “unified” ROOT format event files
  • EicRoot input
  • EicRoot output
  • is available in eic-smear format with charged particle momentum variables “smeared” by Kalman Filter fit after track reconstruction …
  • … while other variables modified by smearing generator according to its recipes


detector view june 2013
Detector view (June’2013)





  • EMC and tracking detectors ~implemented so far



Update on track

resolution studies

tracking elements
Tracking elements

vertex silicon tracker:

  • 6 MAPS layers at up to of 160mm radius; STAR ladder design
  • digitization: discrete ~20x20mm2 pixels

forward/backward silicon trackers:

  • 2x7 disks with up to 280 mm radius; MAPS pixels assumed
  • N sectors per disk; 200mm silicon-equivalent thickness
  • digitization: same as for vertex tracker


  • ~2m long; gas volume radius [300..800] mm
  • 1.2% X0 IFC, 4.0% X0 OFC; 15.0% X0 aluminum endcaps
  • digitization: idealized, assume 1x5 mm GEM pads

GEM trackers:

  • 3 disks behind the TPC endcap; STAR FGT design
  • digitization: 100mm resolution in X&Y; gaussian smearing


tracker view june 2013
Tracker view (June’2013)








tracking scheme
Tracking scheme
  • So-called ideal PandaRoot track “finding”:
  • PandaRoot track fitting code:
  • Monte-Carlo hits are digitized on a per-track basis
  • Effectively NO track finder

MRS-B1 solenoid

design used

  • Kalman filter
  • Steering in magnetic field
  • Precise on-the-fly accounting of material effects


example plots from tracking code
Example plots from tracking code

1 GeV/c p+ tracks at h=0.5:

<ndf> = 206

32 GeV/c p+ tracks at h=3.0:

<ndf> = 9

-> look very reasonable from statistical point of view


momentum resolution plot 1
Momentum resolution plot#1

p+ track momentum resolution vs. pseudo-rapidity

-> expect 2% or better momentum resolution in the whole kinematic range


momentum resolution plot 2
Momentum resolution plot#2

p+ track momentum resolution at h = 3.0 vs. Silicon thickness

-> ~flat over inspected momentum range because of very small Si pixel size


momentum resolution plot 3
Momentum resolution plot#3

p+ track momentum resolution at h = 3.0 vs. Silicon pixel size

-> 20 micron pixel size is essential to maintain good momentum resolution


tracker designer tools
Tracker “designer” tools
  • Allow to easily add “simple” tracking detector templates to the “official” geometry
  • Require next to zero coding effort

Which momentum resolution for 10 GeV/c pions will I get with 10 MAPS layers at h=3?

-> see tutorials/designer/tracking directory for details


tracker designer tools1
Tracker “designer” tools

-> workflow sequence:

  • Create geometry file (few dozens of lines ROOT C script)
  • Include few lines in “standard” sim/digi/reco scripts:
  • Analyze output ROOT file


  • Code written from scratch
  • Unified interface (geometry definition, digitization, clustering) for all EIC calorimeter types
  • Rather detailed digitization implemented:
  • configurable light yield
  • exponential decay time; light collection in a time window
  • attenuation length; possible light reflection on one “cell” end
  • SiPM dark counting rate; APD gain, ENF, ENC
  • configurable thresholds


backward em calorimeter bemc
Backward EM Calorimeter (BEMC)
  • PWO-II, layout a la CMS & PANDA
  • -2500mm from the IP
  • both projective and non-projective geometry implemented
  • digitization based on PANDA R&D

10 GeV/c electron hitting one

of the four BEMC quadrants

Same event (details of shower development)


bemc energy resolution plot 1
BEMC energy resolution plot#1

electrons at h = 2.0

-> projective geometry may lag behind in terms of resolution?


bemc energy resolution plot 2
BEMC energy resolution plot#2

non-projective geometry; h = 2.0

  • “Realistic” digitization: light yield 17pe/MeV; APD gain 50, ENF 2.0, ENC 4.2k; 10 MeV single cell threshold;

-> would be interesting to check sensitivity to all settings in detail


forward em calorimeter femc
Forward EM Calorimeter (FEMC)

tower (and fiber) geometry

described precisely

  • tungsten powder scintillating fiber sampling calorimeter technology
  • +2500mm from the IP; non-projective geometry
  • sampling fraction for e/m showers ~2.6%
  • “medium speed” simulation (up to energy deposit in fiber cores)
  • reasonably detailed digitization; “ideal” clustering code


femc energy resolution study
FEMC energy resolution study

3 degree track-to-tower-axis incident angle

  • “Realistic” digitization: 40MHz SiPM noise in 50ns gate; 4m attenuation length; 5 pixel single tower threshold; 70% light reflection on upstream fiber end;

-> good agreement with original MC studies and measured data


femc tower optimization
FEMC tower “optimization”

original mesh

-> optimized mesh design can probably decrease

“constant term” in energy resolution

optimized mesh


barrel em calorimeter cemc
Barrel EM Calorimeter (CEMC)

-> barrel calorimeter collects less light, but

response (at a fixed 3o angle) is perfectly linear

  • same tungsten powder + fibers technology as FEMC, …
  • … but towers are tapered
  • non-projective; radial distance from beam line [815 .. 980]mm


cemc energy resolution plot 1
CEMC energy resolution plot#1

3 degree track-to-tower-axis incident angle

-> simulation does not show any noticeable difference in energy

resolution between straight and tapered tower calorimeters


cemc energy resolution plot 2
CEMC energy resolution plot#2

8 GeV/c electrons

-> energy response goes down with polar angle because of

effectively decreasing sampling fraction; quite reasonable


cemc energy resolution plot 3
CEMC energy resolution plot#3

8 GeV/c electrons

-> energy resolution degrades with polar angle because of

effectively decreasing sampling frequency (?)


calorimeter designer tools
Calorimeter “designer” tools
  • Allow to easily add “simple” calorimeter detector templates to the “official” geometry
  • Require next to zero coding effort

Which energy resolution for 1 GeV/c electrons will I get with a “basic” PWO calorimeter?


calorimeter designer tools1
Calorimeter “designer” tools
  • your dream calorimeter is a logical 2D matrix …
  • … composed of “long cells” as elementary units,
  • all the game is based on (known) light output per energy deposit,
  • energy resolution after “ideal” digitization suffices as a result
  • As long as the following is true:
  • … one can with a moderate effort (99% of which is writing a ROOT C macro with geometry and mapping description) build custom EicRoot-friendly calorimeter which can be used for both standalone resolution studies and/or as an optional EIC device (and internal cell structure does not matter)

-> see tutorials/designer/calorimetry directory for details