MIP-to-GeV factor
Angela Lucaci-Timoce
Angela Lucaci-Timoce
20th January 2014
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Meaning of MIP-to-GeV factor
• In experimental data:
• consider muons as minimum ionizing particles (MIP)
• measure energy depositions of muons in AHCAL (in ADC counts)
⇒ MIP constants
• measure energy depositions of other particles in AHCAL (in ADC
counts)
• then convert this energy to MIP using the above MIP constants
• In simulated data:
• Use GEANT4 to simulate passage of particles through AHCAL
⇒ energy measured in GeV
• Convert energy in GeV to energy in MIP using corresponding muon
energy ⇒ MIP-to-GeV factor
Angela Lucaci-Timoce
20th January 2014
2/6
History of MIP-to-GeV factor
Values used in CAN-036 and CAN-044: 805 keV
• Given by the maximum (red)
of Landau fit to energy spectra
of generated (raw) muon
→ energy directly from
GEANT4, expressed in GeV
(blue: position of the most
probable value obtained with
ROOT)
• Method described on DESY flc wiki:
http://www-flc.desy.de/flc/flcwiki/MipPerGeV%20and%20Mokka%20rangeCut
• Considered now to be a wrong approach
Angela Lucaci-Timoce
20th January 2014
3/6
History of MIP-to-GeV factor
New method
• Choose MIP to GeV factor such
that energy spectra of
reconstructed muon peaks at
1 MIP
• 840 keV determined by
Clemens with 8 GeV muons
• Plot from Clemens (DESY
AHCAL meeting 1 Oct. 2013)
• Technically, the new method means using an ’educated guess’ for an
initial value of the MIP-to-GeV factor, then running the digitisation
(i.e. conversion from energy in GeV to energy in ADC) and the
reconstruction (i.e. conversion from ADC to MIP, same as in
experimental data), then finally checking that the energy spectra of
reconstructed muon peaks at 1 MIP
Angela Lucaci-Timoce
20th January 2014
4/6
MIP-to-GeV factor for 2011 W-AHCAL data
• Current value: 840 keV
• Example: 40 GeV µ+ in
W-AHCAL
Weuste track finder algorithm
• Muon hits energy spectra has
maximum close to 1 MIP
(AMIP ), as it should
(fit of a Landau convoluted
with a Gaussian, using fitMIP
from the calice calib
software package, used also to
measure MIP constants)
Angela Lucaci-Timoce
Events / ( 0.01125 )
40 GeV µ+ after digitisation and reconstruction
• Muon hits identified with Lars
20000
µ =0.907±0.001
18000
σL=0.108±0.001
L
16000
σG=0.305±0.002
14000
AMIP=0.9979±0.0009
12000
χ2/ndf=6.96
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Energy of muon hits [MIP]
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MIP-to-GeV and cross-talk factors
Note:
• Both factors have a direct impact on simulated data
• Counter-balancing effect: increased MIP-to-GeV factor results into
less energy, increased cross-talk factor results in more energy
Cross-talk factor
• Several measurements available (but not for all SiPMs)
• Original ITEP measurement: 8% for all tiles (i.e. 2% per tile edge),
arXiv:1012:4343
• Measurements by Clemens at DESY: 15-18%
• My choice: cross-talk value of 13% (guess based on comparisons of
positive-polarity data with simulation)
• Note: my choice is just a choice, not a measurement
⇒ large systematic uncertainty
Angela Lucaci-Timoce
20th January 2014
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