Measurement of Neutrino-electron elastic scattering with a CsI(Tl) crystal array at the Kuo-Sheng Reactor Neutrino Laboratory
Date Issued
2006
Date
2006
Author(s)
Shin-Ted, Lin
DOI
en-US
Abstract
Reactors are well suited to study ee scattering. Both charged current (CC) and neutral weak currents (NC) are involved in the Standard Model. A measurement of the differential cross section allows to determine the Weinberg angle sin2 W. and to observe the interference which is expected to be destructive for reasonable values of sin2 W. This thesis will focus on untested few MeV range.
To measure the ee⣵76; scattering, the strategy is to choose on high (>3 MeV) recoil energy above those from natural radioactivity, with the additional merits of having good accuracies in the knowledge of the reactor anti-neutrino spectra. The large target mass compensates the drop in the cross-sections. Selecting lone events,basically neutrino ones, adopted veto of cosmic ray,"Single Hit" and pulse shape discrimination(PSD). According to the PSD capabilities of the crystal, as well as the temporal and spatial correlation of the events, allow a sensitive measurement of intrinsic radio-purity of 235U, 238U and 232Th series. Their concentration gradients with the crystal growth axis, and uniformity among di erent crystal samples, are discovered. This analysis not only provides in the measurement of the detector performance parameters, such as spatial resolution and quenching factors, but also reduces the background due to the contamination with 0.0085 kg⣵76;1day⣵76;1 at 3 5 MeV.
A preliminary background level of 0.412 kg⣵76;1day⣵76;1 at 3 8 MeV, were achieved based on 5592 and 2079 kg-day of reactor ON and OFF data in Period II 1. After subtracting ON and OFF data, we got the e event rate level of 0:0320 0:0167 kg⣵76;1day⣵76;1 at 3 8 MeV. The best t of sin2 w,0:37+- 0:13 at 3 8 MeV, 0:30+- 0:22 at 3.5 8 MeV respectively have been carried out.
The possibilities of reducing background further can be the PSD as thefunction of 2 related to r/e reference pulses, global- t method, more data accumulated which already has another 27000 kg-day 2 on hand and the coming Period IV 3 On the other hand, background understanding corresponding to the 2-hit and 3-hit analysis, including the pair production e ect, 208Tl contamination and ine cient cosmic ray, the preliminary data has been able to explain the dominating background. The expect result of the interaction of e-e Scattering cross section can achieve better than 5 measurement, <8% accuracy of sin2 w, and 4 measurement of destructive interference
term.
Subjects
核電廠微中子
電子微中子散射面積
溫伯格角度
鈾釷衰變
碘化銫晶體
Reactor neutrino
neutrino and electron scattering
Weinberg anglel
radiopurity U and Th
CsI crystal
Type
thesis
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