利用不同背景估计方法对Mrk421的观察.PPT

查敏，张建立，陈松战 (ARGO-YBJ) 2010.04.18 高能物理分会 * content 工作背景的介绍 方法的简介 结果和讨论 Introduction: Mrk421 single flare: 10ICrab ARGO has seen a 4σ effect 2008/05/02 2010/02/18 Whipple --continued * Multi-wave-length Observation of Flares of Mrk421 Method (D.E. Alexandreas NIMA (1993)) Optimize bin size method Non Nbg estimation + the formula to estimate statistical significance Background estimation Isotropic background from charged cosmic ray; Event rate is constant except when changes in the detector configuration are made A strong function of zenith angle; Event rate may change with experimental conditions Detector threshold / dead time External changes (e.g. local atmospheric pressure) Time-swapping method Direct integral method; Equi-zenith method * Data information * 数据11-13 June 2008； nHit on carpet 100; ??400 时间交换法(time-swapping) Assumption: A(h,?,t) = A(h,?,t0)?(t), where ?(t0) = 1 Effective acceptance map in local coordinate is tabulated within certain time period (Tw) Artificial background events are created with the randomly combination of above map and arriving time within this time period; advantage Keep most properties of background parameters Time-shuffling length （Tw）? Swapping times （Nsw）? Possible correction? 6.4% ? 180 minutes; 6.4% *180./T; limitation Conservative result Not applicable to the investigation of high declination sky. * * Tw Significance (?) 3h + 10 + 3.8? 直接积分法（Direct Integral） E(ha, ?): the acceptance distribution in Local Equatorial Coordinates (LEC) for certain period; R(t): event rate of the detector; ?(ha,ra,t) is 1 if events falls within this special bin or 0 othersize; limitation Time integration period?/ conservative result / Not applicable for the source near the North/South pole; * * 4h + 4.4 ? 24h + 4.6 ? 等天顶角法（Equi-Zenith Method） Minimize the detecting factors from detector and environmental variation See Source/background at the same time; Free from zenith dependence; Free from acceptance/ efficiency changes