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T2K: Electron Neutrino Analysis At Near Detector ND280
Available online at www.sciencedirect.com
Nuclear Physics B (Proc. Suppl.) 229–232 (2012) 466 www.elsevier.com/locate/npbps
T2K: Electron Neutrino Analysis At Near Detector ND280 Georgios Christodoulou, for the T2K collaboration University Of Liverpool, United Kingdom
Abstract Starting with a νμ beam T2K will search for νe appearance in the Far Detector (Super-Kamiokande) and aims to produce the first measurement of the neutrino mixing angle θ13 . Beam contamination of νe will be one of the main background components. The Near Detector, ND280, is optimized for measuring the νe contamination through the reconstruction of νe interactions. The reconstruction of electron neutrinos at Near Detector and the method to estimate the νe beam contamination at Super-Kamiokande will be reviewed. Keywords: neutrino, T2K, ND280
The ND280 detector, located at 280m from the neutrino source, is designed to measure the neutrino flux, to characterize the beam composition and to measure various neutrino cross sections. The ND280 detector complex consists of a π0 -detector and a Tracker region containing two fine grained scintillation detectors (FGD) and three time projection chambers (TPC). Both the P0D and the Tracker are surrounded by the electromagnetic calorimeter and all are located inside the UA1 magnet providing a magnetic field of 0.2T. A more detailed description of the ND280 can be found in [1]. 2. Electron neutrino analysis at ND280 The νe tracker analysis requires at least one reconstructed track in the TPC. The inclusive charge current (CC) analysis is based on the most energetic negative track for an electron candidate with a reconstructed vertex in the fiducial FGD volume. For the particle identification, the TPC energy loss of the electron candidate has to be consistent with the electron hypothesis [2]. A momentum cut at 200 MeV/c is applied to minimize background coming from π0 and due to the energy loss curves overlapping, for muons and electrons, below 200 MeV/c [3]. Further cuts, such as the calorime0920-5632/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.nuclphysbps.2012.09.103
ter PID and veto the background coming from outside the tracker, have also been applied. The e/μ separation power of the TPC is demonstrated on Figure 1. The poster also reviews methods to extract and fit the νe spectrum and extrapolating techniques from the near to far detector, but a lot of these, as the νe CC inclusive analysis itself, are still work in progress. Energy Loss (keV/cm)
1. Introduction
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Figure 1: Energy loss of muon candidates traversing all 3 TPCs for 0.11 × 1020 protons on target. Expected e/μ curves overlap. [1] A. Ferrero, The ND280 Near Detector of the T2K Experiment, AIP Conference Proceedings 1189 (1) (2009) 77–82. [2] The T2K Collaboration, Particle Identification with the T2K TPC, T2K-TN-001. [3] The T2K Collaboration, Study of the electron neutrino component in the first T2K physics with the ND280 tracker, T2K-TN014.
Nuclear Physics B (Proc. Suppl.) 229–232 (2012) 466 www.elsevier.com/locate/npbps
T2K: Electron Neutrino Analysis At Near Detector ND280 Georgios Christodoulou, for the T2K collaboration University Of Liverpool, United Kingdom
Abstract Starting with a νμ beam T2K will search for νe appearance in the Far Detector (Super-Kamiokande) and aims to produce the first measurement of the neutrino mixing angle θ13 . Beam contamination of νe will be one of the main background components. The Near Detector, ND280, is optimized for measuring the νe contamination through the reconstruction of νe interactions. The reconstruction of electron neutrinos at Near Detector and the method to estimate the νe beam contamination at Super-Kamiokande will be reviewed. Keywords: neutrino, T2K, ND280
The ND280 detector, located at 280m from the neutrino source, is designed to measure the neutrino flux, to characterize the beam composition and to measure various neutrino cross sections. The ND280 detector complex consists of a π0 -detector and a Tracker region containing two fine grained scintillation detectors (FGD) and three time projection chambers (TPC). Both the P0D and the Tracker are surrounded by the electromagnetic calorimeter and all are located inside the UA1 magnet providing a magnetic field of 0.2T. A more detailed description of the ND280 can be found in [1]. 2. Electron neutrino analysis at ND280 The νe tracker analysis requires at least one reconstructed track in the TPC. The inclusive charge current (CC) analysis is based on the most energetic negative track for an electron candidate with a reconstructed vertex in the fiducial FGD volume. For the particle identification, the TPC energy loss of the electron candidate has to be consistent with the electron hypothesis [2]. A momentum cut at 200 MeV/c is applied to minimize background coming from π0 and due to the energy loss curves overlapping, for muons and electrons, below 200 MeV/c [3]. Further cuts, such as the calorime0920-5632/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.nuclphysbps.2012.09.103
ter PID and veto the background coming from outside the tracker, have also been applied. The e/μ separation power of the TPC is demonstrated on Figure 1. The poster also reviews methods to extract and fit the νe spectrum and extrapolating techniques from the near to far detector, but a lot of these, as the νe CC inclusive analysis itself, are still work in progress. Energy Loss (keV/cm)
1. Introduction
2.5 14 12
2
10 1.5
8 6
1
4
muons
0.5
electrons
2
1σ electrons
100
200
300
400
500
600
700
2σ electrons
800
900
1000
p (MeV/c)
0
Figure 1: Energy loss of muon candidates traversing all 3 TPCs for 0.11 × 1020 protons on target. Expected e/μ curves overlap. [1] A. Ferrero, The ND280 Near Detector of the T2K Experiment, AIP Conference Proceedings 1189 (1) (2009) 77–82. [2] The T2K Collaboration, Particle Identification with the T2K TPC, T2K-TN-001. [3] The T2K Collaboration, Study of the electron neutrino component in the first T2K physics with the ND280 tracker, T2K-TN014.