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Poster part C: 1 – Reactor Neutrino Signals On the Earth; 2 – Target Tracker of Opera

March 14, 2013

Here are three more poster summaries.

1 – Barbara Ricci: Reactor Neutrino Signals All Over The World

Antineutrinos from terrestrial 238U and 232Th decay chains (the so called geo-neutrinos) have been recently detected both by Kamland [1] and by Borexino [2] experiments. Future experiments for geo-neutrinos dectection have been proposed in  several location in the world (e.g. Lena project in Europe, Dusel detector in USA and Hawaii Anti-Neutrino Observatory).

The main source of background of such experiments is given by antineutrino produced by nuclear plants. For instance, in Borexino the expected reactor  signal, assuming a 100% detection efficiency, is 17.2 (1 +-5.4%) events/300ton/yr, comparable to geo neutrino signal. So a detailed calculation of such antineutrino flux in mandatory for an accurate measuraments of geo-neutrinos.

With this aim, we performed a calculation of reactor antineutrinos flux all over the world. A first analysis has been presented at Neutrino Geoscience 2010 [3] and now we will show an updated estimate of reactor antineutrino signal, with  particular attention to the sites proposed for the new geo-neutrino experiments. In our calculation we take into account the most updated data on Thermal Power for each nuclear plant [4], on reactor antineutrino spectra [5] and three neutrino oscillation mechanism [6].

We also perform a detailed analysis on the sources of uncertainty in reactor signal prediction: the total uncertainty is of the order of 5-6%, the main contribution given by mixing angle, antineutrino spectrum, fuel composition and thermal power.

We  report below one of the most  representative result of our analysis: a worldwide map of reactor antineutrino signal, measured in TNU. The figure  corresponds  to the reactor and neutrino data as available at Summer  2012.

Image 

References:

[1] Kamland coll. Nature 436, 499-503 (2005), Nature Geoscience 4, 647 (2011)

[2] Borexino coll. Phys. Lett. B 687, 299-304 (2010).

[3] B. Ricci et al, Talk at Neutrino Geoscience 2010, LNGS, 6-8 Oct. 2010 http://geoscience.lngs.infn.it/Program/Pdf_presentations/Ricci.pdf

[4] Power Reactor Information System (IAEA-PRIS database),  http://www.iaea.org/pris/ and J. Mandula, Nuclear Power Engineering Section, IAEA, Vienna, private communication 2012.

[5] Th. A. Mueller et al, Phys.Rev.C83:054615,2011

[6] G. Fogli et al. , arXive:1205.5254v3.

 

2 – Sergey Dmitrievsky: Target Tracker detector of the OPERA experiment.

The Target Tracker (TT) is the most important electronic detector of the hybrid setup of the OPERA experiment. Each of 62 TT planes (shown in the picture) is composed of a pair of orthogonal arrays of 256 plastic scintillator strips 6.8 m long, 1 cm thick, and 2.6 cm wide, read on both sides using WLS fibres and Hamamatsu multi-anode PMTs.

The main role of the TT is to provide a neutrino interaction trigger for the readout of the whole detector and to locate the lead/emulsion blocks of target (ECC “bricks”) where neutrino interactions occurred. In the neutrino velocity analysis TT hits information was used for independent determination of the neutrino arrival time.

Image

Before TT assembly all scintillator strips had been tested and calibrated with electrons from a beta source using a compact magnetic spectrometer simulating energy lost by a minimum ionizing particle (m.i.p.) in 1 cm of plastic scintillator. PMT signals expressed in terms of the number of photoelectrons (p.e.) were obtained for 9 points along each strip. Determined parameters of attenuation of the signal along the strip fibre are used to reconstruct energy deposition when detecting neutrino events. TT detection efficiency is monitored using cosmic ray data. The efficiency (which is ~99% for a m.i.p.) is stable since TT installation in 2006, that shows no significant ageing of scintillator.

Detailed description of the detector, its main characteristics, methods and algorithms used for the data processing are also presented in the poster.

 

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