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Correction of the energy scale nonlinearity in electromagnetic calorimeters with the pi0 two-photon decays
| Content Provider | Semantic Scholar |
|---|---|
| Author | Bogolyubsky, M. Yu. Kharlov, Yu. V. Patalakha, D. I. Polishchuk, B. V. Sadovsky, S. A. Soloviev, A. S. Stolpovskiy, M. V. |
| Copyright Year | 2011 |
| Abstract | M.Yu.Bogolyubsky et al. Correction of the energy scale nonlinearity in electromagnetic calorimeters with the π two-photon decays: IHEP Preprint 2010-15. – Protvino, 2010. – p. 6, figs. 4, refs.: 4. The method to calculate the non-linearity correction of the electromagnetic calorimeter response, based on minimisation of the deviation of the measured neutral meson mass on the energies of it decay photons, is described in this paper. This method was developed for the electromagnetic calorimeter LGD2 in the Hyperon-M experiment at U70 accelerator of IHEP. The found correction allowed to reduce significantly variations of the reconstructed π and η masses on the minimal energy of the mesons. c © Государственный научный центр Российской Федерации Институт физики высоких энергий, 2010 Introduction Photons and electrons due to interaction with a medium of the cell-type electromagnetic calorimeter produce electromagnetic showers which spreads over several calorimeter cells called a shower cluster, i.e. the group of affected cells with common edges. The read-out electronics for such kind of calorimeters reads the signal amplitudes from calorimeter cells. These amplitudes are used to estimate the real energy deposition of electromagnetic shower in the calorimeter cells by using the independent on energy calibration coefficients. The sum of the deposited energies in the cluster cells defines the energy of the incident photon or electron. This direct energy estimation of electromagnetic showers might be satisfactory in the energy range used for the calorimeter calibration but could lead to energy shifts at different energies which results in the calorimeter response nonlinearities caused by the physical processes, readout electronics and shower reconstruction program. The longitudinal electromagnetic shower profile (electromagnetic cascade in the calorimeter radiators) [1] allows to determine the shower energy deposition in the calorimeter radiators for the case of its finite longitudinal thickness. The position of the energy maximum moves further into the calorimeter with the logarithm of the photon energy, that increases the shower energy leakage out of the calorimeter. Another phenomenon of the measured shower energy loss is related to the finite attenuation length for Cherenkov or scintillation light in the calorimeter cells. The average light path from a radiation point to a photo-detector depends on the energy of the incident photon and reveals itself also as the nonlinear dependence with energy of the light pulse produced by shower. The shower energy leakage is possible in the transversal directions as well, for instance, due to energy loss in gaps between calorimeter cells. Chosen calorimeter design could bring the nonlinearity effects as well. For instance, the used photodetectors could have a nonlinear scale. The read-out electronics (including the analog to digit converters, ADC) could be too noisy, and the noise has to be suppressed by applying the relevant threshold on recorded amplitudes in the calorimeter cells. This threshold leads sometimes to a significant distortion of measured amplitudes of the incident photons at low energies. The enumeration could be continued. But it is important to note that all these effects are unlikely possible to take into account with a high accuracy using Monte Carlo simulations only. Anyway this is sufficiently difficult. The typical task solving by electromagnetic calorimeters in high energy physics experiments is the mass spectra measurement of neutral mesons decaying into photons, for instance, π → γγ, η → γγ, ω → πγ and so on. The calorimeter energy scale nonlinearity have an impact on dependence of the measured neutral meson masses on their energies which leads, in turn, to systematic uncertainties in the meson spectra measurement. Therefore the correction of the calorimeter non-linearity response is relevant in the case. At the same time the possibility of solving this problem directly is no means always the case, i.e. the experimental study of the calorimeter response to photons or electrons at different energies cannot be carried out, for example, at collider experiments or for other reasons. However the correction factor of energy scale of electromagnetic calorimeters could be found as the result of inverse problem solution, i.e. by using experimentally measured mass dependence of neutral mesons on the energy of decay photons. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://arxiv.org/pdf/1102.3649v1.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
