1. Upgrading plan of the tagger Current “new” tagger (SciFi) top view PL SFBSFF ……… 1mm-square fiber 6 fibers = 1ch 1mm-step position measurement 1mm ~ 30 MeV  ~ 30/√12 = 8.7 MeV   ~ 13 MeV (assuming 10 MeV for E  ) Problem Estimation of the photon energy resolution is still underway. 13 MeV resolution is not good enough. (for  + study)  Need upgrade… e’

2. Possible to get better resolution with current tagger ? SFBSFF Using SFF-SFB combination Case-1 SFF-CH# = SFB-CH# Case-2 SFF-CH# = SFB-CH# -1 overlapping size is different (# of event: about 10:1) It may be possible to get better position resolution but it will introduce different  components.  not good for practical analysis.  need upgrade with fine position detector It may be used for cross-check of the resolution study.

3. Possible to get better resolution with current tagger ?  p   p events for E  <1.7 GeV from K0 experiment data (no SVTX)

4. Upgrading plan of the tagger To get better position resolution: 0.5mm-SciFiber layer in addition to the current tagger. Design (detector, Readout) is not finished. Detector structure (# of fibers along the beam…, # of plane), mechanical design…etc. Readout 110 ch for one plane. MA-PMT readout. Space for one plane is available in the current radiation shielding box. Discriminator, Logic, TDC… ADC? Current tagger: TDC only  ADC information will make detector tuning and efficiency estimation easier. But the readout cost will be higher…