Revisiting T2KK and T2KO physics potential and ${\nu }_{\mu }$ - ${\bar{\nu }}_{\mu }$ beam ratio

Abstract

We revisit the sensitivity study of the Tokai-to-Kamioka-and-Korea (T2KK) and Tokai-to-Kamioka-and-Oki (T2KO) proposals where a water Cerenkov detector with the 100 kton fiducial volume is placed in Korea ($L=1000$ km) and Oki island ($L=653$ km) in Japan, respectively, in addition to the Super-Kamiokande for determination of the neutrino mass hierarchy and leptonic CP phase (${\delta }_{CP}$). We systematically study the running ratio of the ${\nu }_{\mu }$ and ${\bar{\nu }}_{\mu }$ focusing beams with dedicated background estimation for the ${\nu }_e$ appearance and ${\nu }_{\mu }$ disappearance signals, especially improving treatment of the neutral current ${\pi }^0$ backgrounds. Using a ${\nu }_{\mu }$ - ${\bar{\nu }}_{\mu }$ beam ratio between 3 : 2 and 2.5 : 2.5 (in unit of $10^{21}$POT with the proton energy of 40 GeV), the mass hierarchy determination with the median sensitivity of 3 - 5 $\sigma$ by the T2KK and 1 - 4 $\sigma$ by the T2KO experiment are expected when ${\sin }^2{\theta }_{23}=0.5$, depending on the mass hierarchy pattern and CP phase. These sensitivities are enhanced (reduced) by $30\%$ - $40\%$ in $\Delta {\chi }^2$ when ${\sin }^2{\theta }_{23}=0.6(0.4)$. The CP phase is measured with the uncertainty of $20^{\circ }$ - $50^{\circ }$ by the T2KK and T2KO using the ${\nu }_{\mu }$ - ${\bar{\nu }}_{\mu }$ focusing beam ratio between 3.5 : 1.5 and 1.5 : 3.5. These findings indicate that inclusion of the ${\bar{\nu }}_{\mu }$ focusing beam improves the sensitivities of the T2KK and T2KO experiments to both the mass hierarchy determination and leptonic CP phase measurement simultaneously with the preferred beam ratio being between 3 : 2 - 2.5 : 2.5 ($\times 10^{21}$POT).

33 pages, 16 figures, 5 tables

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• Improved Measurement of Electron Antineutrino Disappearance at Daya Bay
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• On the impact of systematical uncertainties for the CP violation measurement in superbeam experiments
• Physics potential of T2KK: An extension of the T2K neutrino oscillation experiment with a far detector in Korea
• New measurement of ${\theta }_{13}$ via neutron capture on hydrogen at Daya Bay
• Reassessing the sensitivity to leptonic CP violation
• Solving the degeneracy of the lepton-flavor mixing angle theta_atm by the T2KK two detector neutrino oscillation experiment
• Re-evaluation of the T2KK physics potential with simulations including backgrounds
• Further study of neutrino oscillation with two detectors in Kamioka and Korea

Cited by in corpus (4)

• Non-standard interactions and the CP phase measurements in neutrino oscillations at low energies
• Physics potential of the ESS$\nu$SB
• Heavy neutrino mixing in the T2HK, the T2HKK and an extension of the T2HK with a detector at Oki Islands
• On ${\theta }_{23}$ Octant Measurement in $3+1$ Neutrino Oscillations in T2HKK