PMT calibration S Moriyama for calibration group of

PMT calibration S. Moriyama for calibration group of SK-II 8 th Dec. 2003 @K 2 K conveners meeting • Recent progress of fundamental understanding of the SK-II detector: 1. QE for each PMT 2. gain for each PMT These hardware level of understandings improve MC and raw data. The energy calibration etc. will be discussed by another speaker.

1. QE for each PMT • In SK-I, all PMTs are assumed to have same QE. • In SK-II, we measured (relative) QE for each PMT and put the table into MC. • Method: Ni + Cf neutron source at the center of the tank large number of events with weak Cherenkov light (~30 hits/5000 PMTs) • After corrections of distance, acceptance, water transparency, and reflection from the wall, we obtained a QE table.

QE table • Strong motivation of this table is non-uniformity of the QE distribution. With this table, we can reproduce characteristics our detector well. 1. 3 This structure comes from different production period of PMTs. Barrel 1. 0 0. 7 1. 3 -18 m 1. 3 Top 1. 0 0. 7 r 2 +18 m Bottom r 2

2. Gain for each PMT • In SK-I, PC 2 PE (pico Coulomb to photo electron conversion factor) was thought to be tuned well by applying appropriate HV for all PMTs. • In SK-II, (relative) PC 2 PE value for each PMT is actually measured by laser light source and is applying for raw DATA. • Method: We used a diffuser ball at the center of the tank, and put laser light into the ball. By comparing hit rate by very weak light (~50 PMTs/5000 PMTs) and charge of relatively strong light (~20 p. e. /PMT), we can derive (relative) PC 2 PE value for each PMT.

Gain (PC 2 PE) table • We adjusted HV among PMTs in each part Barrel (Barrel, Top and Bottom) 1. 0 so that each PMT gives same output Q when we give same intensity of 0. 7 0 -1500 Z(cm) light. 1. 3 The PC 2 PE table has Top Bottom anti correlation with the 1. 0 QE table. With this table, we can directly compare # of 0. 7 observed photo electron 0 1 2 3 with MC output. × 106 1. 3 R 2(cm 2)

Conclusion • QE and PC 2 PE table give better understanding of SK-II detector. QE(10% level correction) MC PC 2 PE(RMS 6% level correction) raw data