Interaction point analysis Judgment  /  March 10, 2009 Yoshiaki Nonoyama Nagoya Univ.

3D Event Viewer : demo

x z beam x y Neutrino beam Event: Brick: Type: CC

X-Z projection Y-Z projection

e-pair  Event: Brick: Type: CC Minimum-distance = 1.4  m x z

e-pair x 4  Event: Brick: Type : CC x z Vertex

Minimum-distance of any two tracks all electrons from  0 Under analysis(measure momentum..) mm 17 events 119 combinations It is possible to separate origin of  0, where from 1ry or kink point.

 Topology -- Kink  → e- → e ％  → μ- → μ ％   → h -   →  - ) 49.5 ％ (25 ％ ) Trident   → h - h - h ％ Principle of detecting tau neutrino   -, e -, h - h h cτ = 87 micron Tau life time short  impact parameter to vertex is small  nuclear emulsion (sub um resolution)  nuclear emulsion (sub um resolution) Feature of neutrino tau event -No lepton except tau at 1ry vertex -A decay candidate consistent with tau

τ detection category Long flight decay ：３ ０％ Short flight decay ：７ ０％ θ kink > 20mrad pt > 250Mev IP > 5um Min_pt > 250Mev  IP

OPERACHORUS OPERACHORUS Momentum measurement YesNo  0 detection GoodBad Kink point NoYes Lead (1mm) Film(300  m) Film(700  m) kink OPERA ECC can be measure momentum itself and detecting  0. -> It is possible to reject 2ry interaction by Pt cut and detecting 

Summary OPERA ECC can confirm tau-neutrino interaction if the tau decay impact-parameter more than 5  m. OPERA ECC has high-power for detecting hadronic decay channel. Because… The momentum can be measured by MCS. –> reject 2ry interaction Possible to judge the origin of  0 (1ry vertex or kink). –> High potential  detection