▁around ▁ 2 . 1 ▁m ▁× ▁ 2 . 2 ▁m ▁× ▁ 2 . 4 ▁m ▁( X × Y × Z ) ▁and ▁its ▁mass ▁with ▁and ▁without ▁water ▁is ▁ 1 5 . 8 ▁and ▁ 1 2 . 9 ▁tons ▁respectively . ▁ ▁The ▁main ▁goal ▁of ▁the ▁Pi - Zero ▁Det ector ▁is ▁measurement ▁neutral ▁p ions ▁production ▁in ▁neutral ▁current ▁neut r ino ▁interactions ▁on ▁water : ▁▁ ▁+ ▁N ▁→ ▁ ▁+ ▁N ’ ▁+ ▁ ▁This ▁reaction ▁can ▁m im ic ▁electron ▁neut r ino ▁interactions ▁because ▁phot ons ▁from ▁ ▁decay ▁can ▁be ▁mis - re construct ed ▁as ▁an ▁electron ▁in ▁the ▁Super - K ami ok ande ▁det ector , ▁thus ▁this ▁reaction ▁can ▁m im ic ▁electron ▁neut r ino ▁interactions ▁and ▁const itute ▁an ▁important ▁background ▁in ▁electron ▁neut r ino ▁appearance ▁measurement . ▁ ▁Time ▁projection ▁ch amb ers ▁ ▁Three ▁time ▁projection ▁ch amb ers ▁( TP C s ) ▁are ▁gas - t ight ▁rect angular ▁boxes , ▁with ▁a ▁c ath ode ▁plane ▁in ▁the ▁centre ▁and ▁read out ▁Micro M eg as ▁modules ▁at ▁both ▁sides ▁parallel ▁to ▁the ▁c ath ode . ▁T PC s ▁are ▁filled ▁with ▁arg on - based ▁dr ift ▁gas ▁under ▁atmos pher ic ▁pressure . ▁Ch arg ed ▁particles ▁crossing ▁T PC ▁ion ise ▁the ▁gas ▁along ▁their ▁track . ▁The ▁ion isation ▁electrons ▁dr ift ▁from ▁the ▁c ath ode ▁to ▁the ▁sides ▁of ▁the ▁T