Tau polarization in tau-neutrino nucleon scattering

• Published in: Nuclear physics. B Vol. 668; no. 1; pp. 364 - 384
• Main Authors: Hagiwara, K., Mawatari, K., Yokoya, H.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 22-09-2003
• Subjects: 13.88.+e; 14.60.Fg; 13.15.+g
• ISSN: 0550-3213; 1873-1562
• DOI: 10.1016/S0550-3213(03)00575-3

We investigate the spin polarization of
τ
± leptons produced in
ν
τ
and
ν
̄
τ
nucleon scattering via charged currents. Quasi-elastic scattering,
Δ resonance production and deep inelastic scattering processes are studied. The polarization information is essential for measuring the
τ
± appearance rate in long baseline neutrino oscillation experiments, because the decay particle distributions depend crucially on the
τ
± spin. In this article, we calculate the spin density matrix of each process and estimate the spin polarization vector in medium and high neutrino energy interactions. We find that the produced
τ
±'s have high degree of polarization, and their spin direction depends non-trivially on the energy and the scattering angle of
τ
± in the laboratory frame.