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Poster Summaries Part F: 1 – Nessie; 2 – CUORE-0 and CUORE Sensitivity to Wimps and SN Neutrinos

March 14, 2013
Two more poster summaries:

1 - Marco Roda: The Nessie Experiment

The NESSiE experiment is designed to solve tensions in several
phenomenological models grew up with experimental results on neutrino
and anti-neutrino oscillations at Short-Baseline (SBL) and with the
recent anti-neutrino fluxes from nuclear reactors. The NESSiE detectors are located in two different sites in a new CERN
short baseline neutrino beam: a "near" and a "far" one with respect to
the proton target. Each one of the similar detectors is situated downstream
an ICARUS-like LAr TPC (Time Projection Chamber). The aim is the
measurement of charge and momentum of the muons coming from the charge
current neutrino interactions. The present configuration, for both the
spectrometers, consists of an Air Core Magnet (ACM) followed by an Iron
Core Magnet (ICM). The ACM is designed to be able to measure the charge of low momentum muons,
in order to distinguish neutrino and anti-neutrinos also at low energies.
The designed magnetic field can reach 0.1 T using a dedicated power supply.
The ICM is composed of 2 arms made of 22 iron slabs. Each of the 44 iron
slabs is 5 cm thick and is magnetized with a current of 1600 A: the
resulting magnetic field in the iron is 1.5 T. The gaps between the slabs
are instrumented with RPCs with a digital readout. Other possibilities are
under investigation, such as the use of two smaller consecutive
spectrometers instead of a bigger one: in this way there is the possibility
of reusing the iron slabs of the OPERA spectrometers. In the kinematic region interested by the new oscillation framework, the
best momentum reconstruction is given by the energy loss of the muon in
the iron slabs of the magnet. Using this method, the muon momentum can
be reconstructed from few hundreds MeV to 3 GeV with an uncertainty less
than 6%. For escaping muons, the momentum can be estimated by the bending
of the muon tracks in the magnetic field. The charge reconstruction efficiency varies a lot as a function of the
incoming muon energy. At low energy, the best efficiency is given by the
ACM: in this case the charge mis-identification is less than 0.5%. From
2 GeV on, the best charge reconstruction is given by the ICM. For both
ACM and ICM the efficiency decreases: at 20 GeV the mis-ID is around 30%
for the ICM and 40% for the ACM. The combined sensitivity of the NESSiE and Icarus can explore various
phenomena with a complete : the oscillation from muon neutrino to electron
neutrino and the electron neutrino disappearance and also the muon
neutrino disappearance, which is expected in case of claim of light
sterile neutrino discovery.
Image Figure Description: Charge mis-ID as a function of the true MC momentum at the entrance of
the ICM. The charge is computed using the ACM digits (blue) and the 1st
arm ICM digit (red). The peculiar design of the spectrometer is well
justified by the performances of the ACM for the charge reconstruction
of low momentum: under 1 GeV the mis-ID is at least one order of
magnitude lower than standart iron spectrometers.


2 - Elena Ferri: Cuore-0 and CUORE Sensitivity to Wimps and Supernova Neutrinos

The Cryogenic Underground Observatory for Rare Events (CUORE) is a 1-ton scale bolometric experiment. CUORE is an array of 988 TeO2 crystals of 750 g each arranged in a cylindrical compact and granular structure of 19 towers. Even if its primary target is the observation of neutrinoless double beta decay of Te-130, different analysis can be performed. Thanks to the high mass, the good energy resolution, and the low background it can also be sensitive to other rare processes. Indeed Dark Matter and neutrinos emitted by core collapse supernovae can be detected via the observation of the target nuclei recoil energy. To improve the performances at low energy, the Optimum Filter  algorithm used in the usual  analysis  has been implemented in an online trigger system, called Optimum Trigger [1]. In this way the threshold is lowered from tens of keV to few keV. 

In order to evaluate CUORE-0 and CUORE sensitivity to DM Toy Montecarlo simulations are performed generating background events according to the fit of the measured distribution [2], and WIMP events according to the theoretical distribution described in [3]. Furthermore, the dependence of the WIMP interaction rate on the time in the year is included.

CUORE could investigate the same parameter space of the DAMA/LIBRA experiment as shown in figure in the right figure, and could be the only experiment other than DAMA/LIBRA looking for an annual modulation of dark matter interactions.

Regarding to Supernova Neutrinos a supernova trigger algorithm is implemented in the official CUORE DAQ system. Since the supernova occurrence probability is extremely small compared with the rate at which its presence is searched for (the rate of low energy interactions in the detector, i.e. about 1Hz), the threshold must be chosen with a fixed false-positive rate criterion. A toy Montecarlo simulation is needed to select the threshold on the fit-derived signal that corresponds to the desired false-positive probability [4]. The discovery power corresponding to a rate of false positive of 1/week is calculated by simulating the signal corresponding to different distances. For example, a Supernova at 6kPc is triggered with 95% efficiency.

Image

[1] S. di Domizio et al 2011 JINST 6 P02007

[2] F. Alessandria et al., JCAP01 (2013) 038

[3] J. D. Lewin and P. F. Smithl, Astrop. Phys. 6 (1996), no. 1 87

[4] M. Biassoni, il NUOVO CIMENTO (2013), 36 C n. 1

 

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