Investigation of neutrino oscillations in the T2k long-baseline accelerator experiment
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EMENTARY PARTICLES AND FIELDS Experiment
Investigation of Neutrino Oscillations in the T2K Long-Baseline Accelerator Experiment1) A. O. Izmaylov∗ , N. V. Yershov, Yu. G. Kudenko, V. A. Matveev, O. V. Mineev, Yu. V. Musienko, M. M. Khabibulliun, A. N. Khotjantsev, and A. T. Shaykhiev (On behalf of the T2K Collaboration) Institute for Nuclear Research, Russian Academy of Sciences, pr. Shestidesyatiletiya Oktyabrya 7a, Moscow, 117312 Russia Received May 28, 2010; in final form, February 4, 2011
Abstract—High-sensitivity searches for transitions of muon neutrinos to electron neutrinos are the main task of the T2K (Тokai-to-Kamioka) second-generation long-baseline accelerator neutrino experiment. The present article is devoted to describing basic principles of Т2К, surveying experimental apparatuses that it includes, and considering in detail the muon-range detector (SMRD) designed and manufactured by a group of physicists from the Institute of Nuclear Research (Russian Academy of Sciences, Moscow). The results of the first measurements with a neutrino beam are presented, and plans for the near future are discussed. DOI: 10.1134/S1063778812010097
1. INTRODUCTION Investigation of neutrino oscillations and a determination of the neutrino mass are fundamental issues of weak-interaction physics. The discovery of the neutrino-oscillation phenomenon in experiments with solar and atmospheric neutrinos and in accelerator neutrino experiments [1–5] became the first unambiguous indication of the existence of new physics beyond the Standard Model, where the neutrino mass is set to zero. The oscillation-parameter values measured to date are listed in Table 1. Despite the advances made in these realms, there have appeared many new fundamental questions that call for a solution. First, there is the question of what value the mixing angle θ13 has. Only the upper limit on this parameter from the CHOOZ experiment (sin2 (2θ13 ) < 0.13 at a 90% C.L.) [6] exists at the present time. Second, there is the question of the degree to which sin2 (2θ23 ) differs from unity. Third, there is the question of whether CP violation exists in the in the lepton sector and, if it exists, what value δCP has. Fourth, there is the question of whether transitions to other sterile neutrinos (not involved in weak interaction) exist. From experiments with 1)
Report presented at the conference Physics of Fundamental Interactions held at the scientific session of Nuclear Physics Section (General Physics Department, Russian Academy of Sciences) at the Institute of Theoretical and Experimental Physics (ITEP, Moscow, November 23–27, 2009). ∗ E-mail: [email protected]
solar neutrinos, we know the sign of Δm212 owing to the medium effect {Mikheev–Smirnov–Wolfenstein (MSW) effect [7]}. For Δm223 , only the absolute value has been measured. Therefore, the question of the hierarchy of neutrino mass eigenstates also remains open. A number of neutrino experiments prepared and performed at the present time—the T2K experiment in Japan is among them—will be helpful in providing answ
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