P. Agnes et al. (DarkSide Collaboration) M. Wójcik, G. Zuzel & K. Pelczar

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http://dx.doi.org/10.1103/PhysRevD.93.081101

Abstract

Liquid argon is a bright scintillator with potent particle identification properties, making it an attractive target for direct-detection dark matter searches. The DarkSide-50 dark matter search here reports the first WIMP search results obtained using a target of low-radioactivity argon. DarkSide-50 is a dark matter detector, using a two-phase liquid argon time projection chamber, located at the Laboratori Nazionali del Gran Sasso. The underground argon is shown to contain Ar39 at a level reduced by a factor (1.4±0.2)×103 relative to atmospheric argon. We report a background-free null result from (2616±43)  kg d of data, accumulated over 70.9 live days. When combined with our previous search using an atmospheric argon, the 90% C.L. upper limit on the WIMP-nucleon spin-independent cross section, based on zero events found in the WIMP search regions, is 2.0×10−44  cm2 (8.6×10−44  cm2, 8.0×10−43  cm2) for a WIMP mass of 100  GeV/c2 (1  TeV/c2, 10  TeV/c2).

1. Research project objectives/ Research hypothesis

The scientific goal of this project is the search for signals on non-standard particle physics by looking for neutrino oscillations into sterile neutrinos. It is proposed to realize an experiment sensitive to a large fraction of the parameter space for short distance neutrino flavor oscillations into sterile components. The experiment, named SOX (Short distance Oscillations with boreXino), aims at the complete confirmation or at a clear disproof of the so called neutrino anomalies, a set of circumstantial evidences of electron neutrino disappearance observed at LSND, MiniBoone, with nuclear reactors and with solar neutrino Gallium detectors. The SOX project has been awarded by ERC Advanced Grant (Project Reference: 320873).

If new generations of particles do exist, it is plausible that new neutrino species exist as well, and mixing with known active neutrinos might occur. This scenario, though speculative, is supported by a set of non-conclusive but very significant experimental evidences coming both from particle physics and from cosmology. On one side, several experiments probing neutrino and anti-neutrino oscillations at relatively small values of L/E have observed a systematic lack of events in their detectors, a fact which might be explained in terms of neutrino oscillations into an unknown very weakly interacting component. On the other side, Cosmic Microwave Background Radiation (CMBR) experiments and Large Scale Structure (LSS) studies, when interpreted in the framework of standard cosmology, indicate that the total number of neutrinos in the Universe might be bigger than three.

2. Research project methodology

The BOREXINO detector, originally designed for precision study of low energy solar neutrinos and for the detection of anti-neutrinos originating from the Earth or from unknown astrophysical sources, is an ideal apparatus for the search of sterile neutrinos, both in neutrino and anti-neutrino mode. The experiment will be done by placing a well-designed artificial neutrino sources (⁵¹Cr, ¹⁴⁴Ce-¹⁴⁴Pr) close or inside the BOREXINO solar neutrino detector at the Laboratori Nazionali del Gran Sasso. The superb BOREXINO sensitivity, its large size, and very low radioactive background will be the key elements of the experiment. The well proved capability to detect both low energy electron neutrinos and anti-neutrinos make an ideal case for the study of short distance neutrino oscillations with artificial sources. ⁵¹Cr decays via electron capture into ⁵¹V, emitting two neutrino lines of 750 keV (90%) and 430 keV (10%), while ¹⁴⁴Pr decays β into ¹⁴⁴Nd with an end-point of 3 MeV. SOX will yield additional physics. The electroweak angle θ_W can be directly measured at MeV scale from the ν_e-e⁻ cross-section with an expected precision of 2.6%.

3. Expected impact of the research project on the development of science, civilization and society

SOX project has the potential to discover hypothetical sterile neutrinos. The discovery of the fourth family of neutrinos may be of fundamental importance for the theory of particles and for cosmological models. The precise measurements of the electroweak theory parameters at low energies will be performed.

Agostini M., et al. (Borexino Collaboration) M. Wójcik, G. Zuzel, M. Misiaszek, K. Jędrzejczak

See Synopsis: Still Waiting For Electron Decay

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http://dx.doi.org/10.1103/PhysRevLett.115.231802

Abstract

Borexino is a liquid scintillation detector located deep underground at the Laboratori Nazionali del Gran Sasso (LNGS, Italy). Thanks to the unmatched radio purity of the scintillator, and to the well understood detector response at low energy, a new limit on the stability of the electron for decay into a neutrino and a single monoenergetic photon was obtained. This new bound, τ≥6.6×1028  yr at 90% C.L., is 2 orders of magnitude better than the previous limit.

Agnes P., et al. (Dark-Side Collaboration) M. Wójcik, G. Zuzel, K. Pelczar

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http://dx.doi.org/10.1016/j.physletb.2015.03.012

Abstract

We report the first results of DarkSide-50, a direct search for dark matter operating in the underground Laboratori Nazionali del Gran Sasso (LNGS) and searching for the rare nuclear recoils possibly induced by weakly interacting massive particles (WIMPs). The dark matter detector is a Liquid Argon Time Projection Chamber with a (46.4±0.7) kg(46.4±0.7) kg active mass, operated inside a 30 t organic liquid scintillator neutron veto, which is in turn installed at the center of a 1 kt water Cherenkov veto for the residual flux of cosmic rays. We report here the null results of a dark matter search for a View the MathML source(1422±67) kgd exposure with an atmospheric argon fill. This is the most sensitive dark matter search performed with an argon target, corresponding to a 90% CL upper limit on the WIMP-nucleon spin-independent cross section of 6.1×10−44 cm26.1×10−44 cm2 for a WIMP mass of 100 Gev/c2100 Gev/c2.

Agostini M. et al. (GERDA Collaboration) M. Wójcik, G. Zuzel, K. Pelczar, K. Panas, M. Misiaszek, N. Frodyma, D. Borowicz

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http://dx.doi.org/10.1140/epjc/s10052-015-3627-y

Abstract

A search for neutrinoless ββ decay processes accompanied with Majoron emission has been performed using data collected during Phase I of the GERmanium Detector Array (GERDA) experiment at the Laboratori Nazionali del Gran Sasso of INFN (Italy). Processes with spectral indices n=1,2,3,7 were searched for. No signals were found and lower limits of the order of 1023 yr on their half-lives were derived, yielding substantially improved results compared to previous experiments with 76Ge. A new result for the half-life of the neutrino-accompanied ββ decay of 76Ge with significantly reduced uncertainties is also given, resulting in T2ν1/2=(1.926±0.094)×1021 yr.

M Agostini et al., (GERDA Collaboration), N. Frodyma, M. Misiaszek, K. Pelczar, M. Wojcik, G. Zuzel

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http://arxiv.org/abs/1306.5084
http://link.aps.org/doi/10.1103/PhysRevLett.111.122503

Abstract

Neutrinoless double beta decay is a process that violates lepton number conservation. It is predicted to occur in extensions of the Standard Model of particle physics. This Letter reports the results from Phase I of the GERmanium Detector Array (GERDA) experiment at the Gran Sasso Laboratory (Italy) searching for neutrinoless double beta decay of the isotope 76Ge. Data considered in the present analysis have been collected between November 2011 and May 2013 with a total exposure of 21.6 kgyr. A blind analysis is performed. The background index is about 1.10^{-2} cts/(keV kg yr) after pulse shape discrimination. No signal is observed and a lower limit is derived for the half-life of neutrinoless double beta decay of 76Ge, T_1/2 > 2.1 10^{25} yr (90% C.L.). The combination with the results from the previous experiments with 76Ge yields T_1/2 > 3.0 10^{25} yr (90% C.L.).

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http://dx.doi.org/10.1007/JHEP08(2013)038

Abstract

Physics Letters B 716 (2012) 401–405

P. Alvarez Sanchez et al. (Borexino Collaboration) M. Wójcik, G. Zuzel, M. Misiaszek

Download: http://www.sciencedirect.com/science/article/pii/S0370269312009185

Abstract
We have measured the speed of muon neutrinos with the Borexino detector using short-bunch CNGS beams. The final result for the difference in time-of-flight between an 〈E〉=17 GeV muon neutrino and a particle moving at the speed of light in vacuum is δt=0.8±0.7_stat±2.9_sys ns, well consistent with zero.

Physics Letters B
Volume 713, Issue 3, 9 July 2012, Pages 258–263

Download: http://www.sciencedirect.com/science/article/pii/S037026931200634X

Abstract
In this Letter, we indicate the possibility of using the decay of polarized muons at rest (DPMaR) as a source of the transversely polarized electron antineutrino beam. Such a beam could be used to probe new effects beyond standard model such as: time reversal violation, existence of right-chirality (anti)neutrinos. The (anti)neutrinos are assumed to be Dirac fermions with non-zero mass. We analyze a scenario with the participation of the complex exotic vector, scalar and tensor couplings of the right-chirality electron antineutrinos in addition to the standard vector coupling of the left-chirality ones. We show that the energy–angle distribution of the electron antineutrinos from the DPMaR depends on the interference terms between standard and exotic couplings, which are proportional to the transverse components of the antineutrino spin polarization and independent of a antineutrino mass. It allows to calculate the flux of electron antineutrinos and the expected number of recoil electrons in the elastic antineutrino–electron scattering ve, where the incoming antineutrino beam comes from the DPMaR and is transversely polarized. Our analysis is model-independent and consistent with the current upper limits on the non-standard couplings. The results are presented in a limit of infinitesimally small mass for all particles produced in the muon decay.

G. Bellini et al. (Borexino Collaboration) M. Wójcik, G. Zuzel, M. Misiaszek

Download: http://prd.aps.org/abstract/PRD/v85/i9/e092003

Abstract

A search for 5.5 MeV solar axions produced in the p+d→3He+A (5.5 MeV) reaction was performed using the Borexino detector. The Compton conversion of axions to photons, A+e→e+γ; the axioelectric effect, A+e+Z→e+Z; the decay of axions into two photons, A→2γ; and inverse Primakoff conversion on nuclei, A+Z→γ+Z, are considered. Model-independent limits on axion-electron (gAe), axion-photon (gAγ), and isovector axion-nucleon (g3AN) couplings are obtained: |gAe×g3AN|≤5.5×10-13 and |gAγ×g3AN|≤4.6×10-11  GeV-1 at mA