117791829
Study of Solar and Geo-Neutrinos with the BOREXINO Detector
119380720
Cosmogenic 11C production and sentivity of organic scintillator detectors to pep and CNO neutrinos
Several possible background sources determine the detectability of pep and CNO solar neutrinos in organic liquid scintillator detectors. Among such sources, the cosmogenic {sup 11}C nuclide plays a central role. {sup 11}C is produced underground in reactions induced by the residual cosmic muon flux. Experimental data available for the effective cross section for {sup 11}C by muons indicate that {sup 11}C will be the dominant source of background for the observation of pep and CNO neutrinos. {sup 11}C decays are expected to total a rate 2.5 (20) times higher than the combined rate of pep and CNO neutrinos in Borexino (KamLAND) in the energy window preferred for the pep measurement between 0.8 and 1.3 MeV. This study examines the production mechanism of {sup 11}C by muon-induced showers in organic liquid scintillators with a novel approach: for the first time, we perform a detailed ab initio calculation of the production of a cosmogenic nuclide, {sup 11}C, taking into consideration all relevant production channels. Results of the calculation are compared with the effective cross sections measured by target experiments in muon beams. This article also discusses a technique for reduction of background from {sup 11}C in organic liquid scintillator detectors, which allowsmore » to identify on a one-by-one basis and remove from the data set a large fraction of {sup 11}C decays. The background reduction technique hinges on an idea proposed by Martin Deutsch, who suggested that a neutron must be ejected in every interaction producing a {sup 11}C nuclide from {sup 12}C. {sup 11}C events are tagged by a threefold coincidence with the parent muon track and the subsequent neutron capture on protons.« less
119000964
Measurement of the cosmogenic 11C background with the Borexino Counting Test Facility
Within next year, two organic liquid scintillator detectors, Borexino and KamLAND, will start the measurement of the mono‐energetic 7Be solar neutrino flux in real time. Besides this objective, both of them have the potential to detect neutrinos from the pep fusion reaction and the CNO cycle in the Sun.For this purpose, two conditions are required: an extremely low radioactive contamination level and the efficient identification of the 11C background, produced in reactions induced by the residual cosmic muon flux on 12C. In the process, a free neutron is almost always produced. 11C can be tagged on an event by event basis by looking at the three‐fold coincidence with the parent muon track and the subsequent neutron capture on protons. We tested successfully this coincidence method with the Borexino Counting Test Facility. The results are reported here.Moreover, we discuss on the effective potential of Borexino and KamLAND in detecting pep+CNO neutrinos compared to SNO+, a detector specifically designed fo...
119181847
Positronium signature in organic liquid scintillators for neutrino experiments
Electron antineutrinos are commonly detected in liquid scintillator experiments via inverse {beta} decay by looking at the coincidence between the reaction products: neutrons and positrons. Prior to positron annihilation, an electron-positron pair may form an orthopositronium (o-Ps) state, with a mean lifetime of a few nanoseconds. Even if the o-Ps decay is speeded up by spin-flip or pick-off effects, it may introduce distortions in the photon emission time distribution, crucial for position reconstruction and pulse shape discrimination algorithms in antineutrino experiments. Reversing the problem, the o-Ps-induced time distortion represents a new signature for tagging antineutrinos in liquid scintillator. In this article, we report the results of measurements of the o-Ps formation probability and lifetime for the most used solvents for organic liquid scintillators in neutrino physics (pseudocumene, linear alkyl benzene, phenylxylylethane, and dodecane). We characterize also a mixture of pseudocumene +1.5 g/l of 2,5-diphenyloxazole, a fluor acting as wavelength shifter. In the second part of the article, we demonstrate that the o-Ps-induced distortion of the scintillation photon emission time distributions represent an optimal signature for tagging positrons on an event by event basis, potentially enhancing the antineutrino detection.
122582401
Monte Carlo evaluation of the muon-induced background in the GERDA double beta decay experiment
Abstract The new generation of experiments searching for neutrinoless double beta decay is aiming at a background level of 10 - 3 counts / ( kg keV y ) or better at the respective Q -values. Cosmic ray muons can be a significant contribution due to a number of physics processes. The GERmanium Detector Array, GERDA, located at the Gran Sasso underground laboratory in Italy, uses germanium enriched in 76 Ge as source and detector material. Germanium is submerged into liquid nitrogen or argon that acts as cooling medium and radiation shield simultaneously. A detailed G eant 4-based Monte Carlo simulation was performed to calculate the photon and neutron fluxes induced by cosmic ray muons. The prompt background contributions from γ -ray and neutron interactions as well as the delayed contributions due to the production of radioactive isotopes within the setup are given. The background can be reduced to the desired level with the muon veto system incorporated in the GERDA design.
120536446
Performances and calibrations of the Borexino detector
Borexino is a real-time detector for low energy Solar neutrino spectroscopy installed in the underground laboratories (3800 mwe depth) at Gran Sasso, Italy (LNGS). Borexino is specifically designed to measure the mono-energetic (866 keV) 7Be flux via neutrino-electron elastic scattering in ultra-pure organic scintillation liquid. The separation of signal and background relies on the identification of the Compton-like edge in the recoil electron energy spectrum at 667 keV. The physics potential of Borexino strongly depends on the unprecedented requirements of low level background. The exceptional radio-purity reached by the Borexino, in order to guarantee the success of the experiment, must be complemented with the identification and discrimination of the residual intrinsic contaminants, as well as of the external and cosmogenic backgrounds. Crucial in this respect are the energy and spatial reconstruction capabilities of the detector, which thus require a careful and precise assessment. We report on the Borexino performances after 1 year of data taking in reconstructing event energy and position, in discriminating on the nature of the contaminant with the pulse shape analysis and in the identification of fast coincidences looking at time and space correlations.
17124386
Exact scale invarianmce of the BF-Yang-Mills theory in three dimensions
The ``extended'' BF-Yang-Mills theory in 3 dimensions, which contains a minimally coupled scalar field, is shown to be ultraviolet finite. It obeys a trivial Callan-Symanzik equation, with all β-functions and anomalous dimensions vanishing. The proof is based on an anomaly-free trace identity valid to all orders of perturbation theory.
17954300
A note on Fourier–Laplace transform and analytic wave front set in theory of tempered ultrahyperfunctions
Abstract In this paper we study the Fourier–Laplace transform of tempered ultrahyperfunctions introduced by Sebastiao e Silva and Hasumi. We establish a generalization of Paley–Wiener–Schwartz theorem for this setting. This theorem is interesting in connection with the microlocal analysis. For this reason, the paper also contains a description of the singularity structure of tempered ultrahyperfunctions in terms of the concept of analytic wave front set.
119528722
Gauge independence of the effective potential revisited
We apply the formalism of extended BRS symmetry to the investigation of the gauge dependence of the effective potential in a spontaneously symmetry broken gauge theory. This formalism, which includes a set of Grassmann parameters defined as the BRS variations of the gauge-fixing parameters, allows us to derive in a quick and unambiguous way the related Nielsen identities, which express the physical gauge independence, in a class of generalized 't Hooft gauges, of the effective potential. We show in particular that the validity of the Nielsen identities does not require any constraint on the gauge-fixing parameters, contrary to some claims found in the literature. We use the method of algebraic renormalization, which leads to results independent of the particular renormalization scheme used.
118943031
Comment on ``On spin-1 massive particles coupled to a Chern-Simons field''
In this comment we discuss some serious inconsistencies presented by Gomes, Malacarne and da Silva in their paper, Phys.Rev. D60 (1999) 125016 (hep-th/9908181).
119307919
Finite one-loop radiative corrections in the Lorentz- and CPT-violating QED extension
We report on our current progress in the study of finite one-loop radiative corrections in the minimal Lorentz- and CPT-violating QED extension.