- Email: [email protected]
The Double Chooz simulation strategy
Available online at www.sciencedirect.com
Nuclear Physics B (Proc. Suppl.) 221 (2011) 378 www.elsevier.com/locate/npbps
The Double Chooz simulation strategy Dario Motta1 , Anatael Cabrera2 1 2
DAPNIA/SPP, CEA/Saclay, 91191 Gif-sur-Yvette CEDEX, France APC, Collge de France, 11 place Marcelin Berthelot, 75231 PARIS CEDEX 05, France
E-mail: [email protected], [email protected]
The Double Chooz experiment (DC hereafter) aims to search for a non-vanishing PMNS θ13 neutrino oscillation parameter from precise comparison of ν e fluxes and spectra measured by two identical detectors at different distances from the Chooz reactors (France). Details in [1, 2]. The design of the DC experiment has been based on detailed simulation studies aimed at optimizing the detector performance, while reducing the systematics and backgrounds. Details of all sub-systems and of the calibration devices are now being worked out with the aid of simulations to assess the accuracy within which the two detectors need to be identical. The DC Monte Carlo simulation is based on GLG4sim [3], a public simulation package built on Geant4 (G4) [4]. Major extensions have been developed to implement a detailed micro-physical optical model of both scintillators and photomultiplier tubes (PMTs) [1]. This model accounts for the details of light production, wavelength-shift, absorption, reflection and refraction at all interfaces, including PMTs. The model is used to predict the intrinsic detector response, investigate the impact of detector-to-detector variations, set the calibration strategy, optimize the scintillator formulation and study possible aging scenarios. A full read-out system simulation converts the photon-hits into digitized signals, including charge and time smearing. The simulated DC signals can then be reconstructed like real data. The reconstruction algorithm uses the signals from all PMTs to maximize a charge and time likelihood function. Understanding the response to neutrons is critical in DC, hence a new model has been developed to improve the G4 description of the radiative emission upon n-capture by Gd [1]. Substantial efforts have been devoted to the simulation of backgrounds, in particular the μinduced ones. For the latter, an accurate (E, θ, φ) resolved μ flux at far and near site (overburden of 300 and 80 mwe respectively) has been calculated [5, 6]. The generated fluxes are used to predict the μ-induced fast neutron background; the production of long-lived, (β/n)-decaying nuclei (9 Li, 8 He) by showering muons; the Bremsstrahlung gammas from δ/knock-on e− by near-miss muons. These studies are combined with the Monte Carlo of the inner and outer veto systems to evaluate their performance and hence optimize the design with respect to the μ detection efficiency and background rejection. References [1] [2] [3] [4] [5] [6]
Ardellier F, et al, 2006, Double Chooz: a search for the neutrino mixing angle θ13 Preprint hep-ex/0606025 Reyna D, these proceedings Horton-Smith G, http://neutrino.phys.ksu.edu/˜GLG4sim/ Agostinelli S, et al., Nucl. Instr. Meth. A 506 (2003), 250 Tang A, Horton-Smith G, Kudryavtsev V A and Tonazzo A, these proceedings, (Preprint hep-ph/0604078) Reyna D. 2006 Preprint hep-ph/0604145
0920-5632/$ – see front matter © 2011 Published by Elsevier B.V. doi:10.1016/j.nuclphysbps.2011.10.027
Nuclear Physics B (Proc. Suppl.) 221 (2011) 378 www.elsevier.com/locate/npbps
The Double Chooz simulation strategy Dario Motta1 , Anatael Cabrera2 1 2
DAPNIA/SPP, CEA/Saclay, 91191 Gif-sur-Yvette CEDEX, France APC, Collge de France, 11 place Marcelin Berthelot, 75231 PARIS CEDEX 05, France
E-mail: [email protected], [email protected]
The Double Chooz experiment (DC hereafter) aims to search for a non-vanishing PMNS θ13 neutrino oscillation parameter from precise comparison of ν e fluxes and spectra measured by two identical detectors at different distances from the Chooz reactors (France). Details in [1, 2]. The design of the DC experiment has been based on detailed simulation studies aimed at optimizing the detector performance, while reducing the systematics and backgrounds. Details of all sub-systems and of the calibration devices are now being worked out with the aid of simulations to assess the accuracy within which the two detectors need to be identical. The DC Monte Carlo simulation is based on GLG4sim [3], a public simulation package built on Geant4 (G4) [4]. Major extensions have been developed to implement a detailed micro-physical optical model of both scintillators and photomultiplier tubes (PMTs) [1]. This model accounts for the details of light production, wavelength-shift, absorption, reflection and refraction at all interfaces, including PMTs. The model is used to predict the intrinsic detector response, investigate the impact of detector-to-detector variations, set the calibration strategy, optimize the scintillator formulation and study possible aging scenarios. A full read-out system simulation converts the photon-hits into digitized signals, including charge and time smearing. The simulated DC signals can then be reconstructed like real data. The reconstruction algorithm uses the signals from all PMTs to maximize a charge and time likelihood function. Understanding the response to neutrons is critical in DC, hence a new model has been developed to improve the G4 description of the radiative emission upon n-capture by Gd [1]. Substantial efforts have been devoted to the simulation of backgrounds, in particular the μinduced ones. For the latter, an accurate (E, θ, φ) resolved μ flux at far and near site (overburden of 300 and 80 mwe respectively) has been calculated [5, 6]. The generated fluxes are used to predict the μ-induced fast neutron background; the production of long-lived, (β/n)-decaying nuclei (9 Li, 8 He) by showering muons; the Bremsstrahlung gammas from δ/knock-on e− by near-miss muons. These studies are combined with the Monte Carlo of the inner and outer veto systems to evaluate their performance and hence optimize the design with respect to the μ detection efficiency and background rejection. References [1] [2] [3] [4] [5] [6]
Ardellier F, et al, 2006, Double Chooz: a search for the neutrino mixing angle θ13 Preprint hep-ex/0606025 Reyna D, these proceedings Horton-Smith G, http://neutrino.phys.ksu.edu/˜GLG4sim/ Agostinelli S, et al., Nucl. Instr. Meth. A 506 (2003), 250 Tang A, Horton-Smith G, Kudryavtsev V A and Tonazzo A, these proceedings, (Preprint hep-ph/0604078) Reyna D. 2006 Preprint hep-ph/0604145
0920-5632/$ – see front matter © 2011 Published by Elsevier B.V. doi:10.1016/j.nuclphysbps.2011.10.027