1、水质契仑科夫探测器中的中子识别张海兵清华大学2008.4.28, 南京First Study of Neutron Tagging with a Water Cherenkov Detector1Neutrino Detection at Super-KamiokandeneElectron (e)nMuon ()The products are charged particles.The neutrino is observed by “seeing” theproduct of its interaction with water.Charged particles with 1/n em
2、its Cherenkov light 2-All 6 types of neutrino emitted when supernovae explode but only is most likely to observe. - Detection of is the key step to see SRN at SK.Neutrinos from SpacelConfirmed neutrinos from spacelWhos next?Supernova relic neutrino (SRN)?a) Solar neutrinob) SN 1987A3Previous Searche
3、s for SRN SK-I limit : 1.25 /cm2/sSK SRN Limits vs. Theoretical PredictionsThe result can be significantly improved if SK enhanced with neutron tagging capability. 4Why Neutron Tagging?Neutron tagging plays a role in identifying inverse beta decay.A delayed coincidence technique can be used to ident
4、ify reaction chain.5Methods of Tagging Neutron from Inverse Decay6Forced Trigger (FOG)lGenerate 500 additional “forced triggers” at the interval of 1us after primary trigger by e+.lSearch 2.2MeV candidates in the 500 us data pack.Threshold7Test with a Simulated Signal5 cmAm/BeAm/Be neutron source em
5、bedded in BGO crystal 8Experimental Setupn5 cmAm/Be(1)Forced trigger case(2)Gadolinium case9Signal and Background in Forced Trigger Datal Source run (Am/Be+BGO)l BG run (BGO only) for neutron tagging efficiency study Signal FOG: 500 BG events + one 2.2 MeV for cross checking and background estimation BG FOG: 500 BG events# of PMT hits timeThe main difficulty rests with how to extract the weak 2.2 MeV signal from heavy background, e.g. PMT noise and other low energy events . 10
