111 research outputs found
Scalar form factors and nuclear interactions
The scalar-isoscalar term in the two-pion exchange potential is
abnormally large and does not respect the hierarchy of effects predicted by
chiral perturbation theory. We argue that this anomaly is associated with
non-perturbative effects, which are also present in the scalar form
factor.Comment: Talk given at the 20EFB, Pisa, Italy, September 2007. 3 pages and 4
figure
User embracement and risk classification at obstetric emergency: evaluating operationalization in a maternity hospital school
Final results of Borexino Phase-I on low energy solar neutrino spectroscopy
Borexino has been running since May 2007 at the LNGS with the primary goal of
detecting solar neutrinos. The detector, a large, unsegmented liquid
scintillator calorimeter characterized by unprecedented low levels of intrinsic
radioactivity, is optimized for the study of the lower energy part of the
spectrum. During the Phase-I (2007-2010) Borexino first detected and then
precisely measured the flux of the 7Be solar neutrinos, ruled out any
significant day-night asymmetry of their interaction rate, made the first
direct observation of the pep neutrinos, and set the tightest upper limit on
the flux of CNO neutrinos. In this paper we discuss the signal signature and
provide a comprehensive description of the backgrounds, quantify their event
rates, describe the methods for their identification, selection or subtraction,
and describe data analysis. Key features are an extensive in situ calibration
program using radioactive sources, the detailed modeling of the detector
response, the ability to define an innermost fiducial volume with extremely low
background via software cuts, and the excellent pulse-shape discrimination
capability of the scintillator that allows particle identification. We report a
measurement of the annual modulation of the 7 Be neutrino interaction rate. The
period, the amplitude, and the phase of the observed modulation are consistent
with the solar origin of these events, and the absence of their annual
modulation is rejected with higher than 99% C.L. The physics implications of
phase-I results in the context of the neutrino oscillation physics and solar
models are presented
Measurement of neutrino flux from the primary proton--proton fusion process in the Sun with Borexino detector
Neutrino produced in a chain of nuclear reactions in the Sun starting from
the fusion of two protons, for the first time has been detected in a real-time
detector in spectrometric mode. The unique properties of the Borexino detector
provided an oppurtunity to disentangle pp-neutrino spectrum from the background
components. A comparison of the total neutrino flux from the Sun with Solar
luminosity in photons provides a test of the stability of the Sun on the
10 years time scale, and sets a strong limit on the power production in
the unknown energy sources in the Sun of no more than 4\% of the total energy
production at 90\% C.L.Comment: 15 pages, 2 tables, 3 figure
Expression of a rice chitinase gene in transgenic banana ('Gros Michel', AAA genome group) confers resistance to black leaf streak disease
Peer reviewe
Extração de DNA a partir de sangue humano coagulado para aplicação nas técnicas de genotipagem de antígenos leucocitários humanos e de receptores semelhantes à imunoglobulina
Secreted phospholipase A2 of Clonorchis sinensis activates hepatic stellate cells through a pathway involving JNK signalling
Identification of the cosmogenic 11C background in large volumes of liquid scintillators with Borexino
Cosmogenic radio-nuclei are an important source of background for low-energy neutrino experiments. In Borexino, cosmogenic 11C decays outnumber solar pep and CNO neutrino events by about ten to one. In order to extract the flux of these two neutrino species, a highly efficient identification of this background is mandatory. We present here the details of the most consolidated strategy, used throughout Borexino solar neutrino measurements. It hinges upon finding the space-time correlations between 11C decays, the preceding parent muons and the accompanying neutrons. This article describes the working principles and evaluates the performance of this Three-Fold Coincidence (TFC) technique in its two current implementations: a hard-cut and a likelihood-based approach. Both show stable performances throughout Borexino Phases II (2012–2016) and III (2016–2020) data sets, with a 11C tagging efficiency of ∼90 % and ∼ 63–66 % of the exposure surviving the tagging. We present also a novel technique that targets specifically 11C produced in high-multiplicity during major spallation events. Such 11C appear as a burst of events, whose space-time correlation can be exploited. Burst identification can be combined with the TFC to obtain about the same tagging efficiency of ∼90% but with a higher fraction of the exposure surviving, in the range of ∼ 66–68 %
Cosmogenic Backgrounds in Borexino at 3800 m water-equivalent depth
The solar neutrino experiment Borexino, which is located in the Gran Sasso
underground laboratories, is in a unique position to study muon-induced
backgrounds in an organic liquid scintillator. In this study, a large sample of
cosmic muons is identified and tracked by a muon veto detector external to the
liquid scintillator, and by the specific light patterns observed when muons
cross the scintillator volume. The yield of muon-induced neutrons is found to
be Yn =(3.10+-0.11)10-4 n/({\mu} (g/cm2)). The distance profile between the
parent muon track and the neutron capture point has the average value {\lambda}
= (81.5 +- 2.7)cm. Additionally the yields of a number of cosmogenic
radioisotopes are measured for 12N, 12B, 8He, 9C, 9Li, 8B, 6He, 8Li, 11Be, 10C
and 11C. All results are compared with Monte Carlo simulation predictions using
the Fluka and Geant4 packages. General agreement between data and simulation is
observed for the cosmogenic production yields with a few exceptions, the most
prominent case being 11C yield for which both codes return about 50% lower
values. The predicted {\mu}-n distance profile and the neutron multiplicity
distribution are found to be overall consistent with data.Comment: 26 pages, 13 figures (in 14 files), 4 tables. 3 extra data files.
accepted by JCA
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