- Introduction
- Average of Charge Response
- Distribution of sq0/q0 obtained from the 118 PMTs
- Distribution of qtau/q0 obtained from the 118 PMTs
- Distribution of pe obtained from the 118 PMTs
- Why we do not use data at low gain?
- Conclusion

The analytical function shown below has been used to represent the PMT charge response and implemented in the PMT simulation "ROMEO". The implementation was made when the calibration data was statistically limited, however. It is now over 4 years since Chiba started the PMT calibration and the present data is rich enough to picture "average" behavior of the IceCube PMT response. Here we describe the results of the systematic study on the charge response based upon the calibration data of 118 PMTs. The distributions of values of the coefficients in the analytical response function are plotted in various gains. We also build a hypothetical "average" IceCube PMT response model by averaging those values. This is to be implemented in ROMEO to represent the default IceCube PMT in the detector simulations.

See also.

- Charge Response Function study in the IceCube WIKI
- Measurement and analysis methods in the Chiba PMT webpage.

Plotted below are the average charge response functions for three different gain settings. In order to see the fluctuation of the response function, the lower panels shows the curves of the function with the higher and lower values of the coefficients by 1 sigma. Red curves correspond to the case when pe is shifted by ±1 sigma. Blue for qtau/q0, green for sq0/q0.

Average | |||
---|---|---|---|

Fluctuation | |||

Gain | 5.0e+7 | 7.0~8.0e+7 | 10.0~12.0e+7 |

fitting histogram | |||
---|---|---|---|

gain | 5.0e+7 | 7.0~8.0e+7 | 10.0~13.0e+7 |

This parameter corresponds to the charge resolution of PMT. Most of an individual PMT has been measured in five different gains. It is found that no obvious gain dependences have been observed. This implies that the parameterization of the response function is valid in the gain range of the IceCube operation.

Graph before the cut.

Table1 [1D Histogram by projection of 2D Graphs in three groups of gain ]

Histogram | |||
---|---|---|---|

Gain | 5.0e+7 gain | 7.0~8.0e+7 gain | 10.0~12.0e+7 gain |

Average | 0.2828 ± 0.0095 | 0.2937 ± 0.0099 | 0.2717 ± 0.0204 |

Sigma | 0.0325 | 0.0349 | 0.0574 |

"qtau" corresponds to decay time of exponential term of fit function

Graph befor the cut.

Table2 [1D Histogram by projection of 2D Graphs in three groups of gain ]

Histogram | |||
---|---|---|---|

Gain | 5.0e+7 gain | 7.0~8.0e+7 gain | 10.0~12.0e+7 gain |

Avarage | 0.4390 ± 0.0144 | 0.5226 ± 0.0172 | 0.5463 ± 0.0196 |

Sigma | 0.0479 | 0.0645 | 0.0883 |

Graph befor the cut

Table3 [1D Histogram by projection of 2D Graphs in three groups of gain ]

Histogram | |||
---|---|---|---|

Gain | 5.0e+7 gain | 7.0~8.0e+7 gain | 10.0~12.0e+7 gain |

Avarage | 0.3656 ± 0.0095 | 0.2705 ± 0.0096 | 0.2719 ± 0.0090 |

Sigma | 0.0604 | 0.0477 | 0.0676 |

sq0/q0 | ||
---|---|---|

qtau/q0 | ||

pe | ||

Gain | 2.0~3.0e+7 | 5.0+7 |

Charge Response can be described in PMT gain independent way within our resolution of the present measurements. For the reference, shown below is the average charge response function curve in comparison with the 2006 ROMEO default model.

Red solid line : AVERAGE charge response all PMT (>5e+7 gain)

Black dotted line : ROMEO charge response

- ROMEO
- Mean = 0.759
- integ below 0.2 pe = 0.2309
- integ below 0.3 pe = 0.2706

Table4 [1D Histogram by projection of 2D Graphs (>5e+7 gain) ]

Histogram | |||
---|---|---|---|

Parameter | sq0/q0 | qtau/q0 | pe |

Avarage | 0.2916 ± 0.0091 | 0.5057 ± 0.0162 | 0.2987 ± 0.0102 |

ROMEO | 0.3650 | 0.1219 | 0.2765 |

mailto:Y.Hasegawa Last modified: Tue Jun 5 18:28:06 JST 2007