Neutrino beam properties of T2K experiment
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Neutrino Beam Properties of T2K Experiment T. A. Ovsyannikovaa, b, * and Yu. G. Kudenkoa, b, c a
Institute for Nuclear Research, Russian Academy of Sciences, pr. 60letiya Oktyabrya 7a, Moscow, 117312 Russia b National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Kashirskoe sh. 31, Moscow 115409 Russia c Moscow Institute of Physics and Technology (State University), Institutskii per. 9, Dolgoprudnyi, Moscow oblast, 141700 Russia *email: [email protected] Received January 23, 2015
Abstract—The neutrino onaxis and offaxis beam was studied in the near neutrino detector of the long baseline experiment T2K: beam composition, longterm stability, and spatial asymmetry. Keywords: muon neutrino beam, longterm stability, experiment T2K. DOI: 10.1134/S1063778815130268
1. INTRODUCTION The main objectives of the acceleratorbased long baseline neutrino experiment T2K are the study of neutrino oscillations and the search for CP violation in the lepton sector [1, 2]. The 30GeV proton beam of the JPARC accelerator is used in the experiment; hit ting a graphite target, it generates charged pions and kaons. Pions are focused by the system of three pulsed magnets and then decay in the decay channel with a length of about 100 m [3]. The Cherenkov detector SuperKamiokande situated at a distance of 295 km from the accelerator registers muon and electron neu trinos. The near detector ND280 situated at a distance of 280 m from the pionproducing target is used for measuring and monitoring the neutrino beam close to the target, i.e., before possible oscillations. The near detector consists of the INGRID detector [4] on the beam axis and an offaxis detector at an angle of 2.5 degrees with respect to the proton beam axis. The off axis detector is designated for measuring the flux and
energy spectrum of muon neutrinos; it also measures the admixture of electron neutrinos in the beam of muon neutrinos [3]. In this study, we discuss the requirements on the neutrino beam for precision mea surement of oscillation parameters. The schematic diagram of the experiment is shown in Fig. 1. The INGRID detector [4] consists of alternating iron and scintillator layers and serves for monitoring the beam stability. The offaxis detector is situated in the magnetic field and consists of several detectors: the P∅ Dwater 0 scintillation detector identifying π from neutrino– nucleon interactions via neutral currents; the track detector consisting of alternating timeprojection chambers (TPCs); FGD detectors designated for the study of charged currents; and ECal, an electromag netic calorimeter. The offaxis detector is placed inside a magnet consisting of eight sections (yoke) within which the SMRD detector is situated [5]. a
ND 280 Offaxis p
π
SK
Decay volume ν ν Muon monitor Onaxis
0
140 m
280 m
2 km
Fig. 1. Schematic diagram of the T2K experiment.
1610
295 km
Events/1014 POT
NEUTRINO BEAM PROPERTIES OF T2K EXPERIMENT 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4
Event rate
Horn 250 kA Horn 205 kA Horn25
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