595 research outputs found
Neutrino-induced deuteron disintegration experiment
Cross sections for the disintegration of the deuteron via neutral-current
(NCD) and charged-current (CCD) interactions with reactor antineutrinos are
measured to be 6.08 +/- 0.77 x 10^(-45) cm-sq and 9.83 +/- 2.04 x 10^(-45)
cm-sq per neutrino, respectively, in excellent agreement with current
calculations. Since the experimental NCD value depends upon the CCD value, if
we use the theoretical value for the CCD reaction, we obtain the improved value
of 5.98 +/- 0.54 x 10^(-45) for the NCD cross section. The neutral-current
reaction allows a unique measurement of the isovector-axial vector coupling
constant in the hadronic weak interaction (beta). In the standard model, this
constant is predicted to be exactly 1, independent of the Weinberg angle. We
measure a value of beta^2 = 1.01 +/- 0.16. Using the above improved value for
the NCD cross section, beta^2 becomes 0.99 +/- 0.10.Comment: 22pages, 9 figure
Initial Results from the CHOOZ Long Baseline Reactor Neutrino Oscillation Experiment
Initial results are presented from CHOOZ, a long-baseline reactor-neutrino
vacuum-oscillation experiment. Electron antineutrinos were detected by a liquid
scintillation calorimeter located at a distance of about 1 km. The detector was
constructed in a tunnel protected from cosmic rays by a 300 MWE rock
overburden. This massive shielding strongly reduced potentially troublesome
backgrounds due to cosmic-ray muons, leading to a background rate of about one
event per day, more than an order of magnitude smaller than the observed
neutrino signal. From the statistical agreement between detected and expected
neutrino event rates, we find (at 90% confidence level) no evidence for
neutrino oscillations in the electron antineutrino disappearance mode for the
parameter region given approximately by deltam**2 > 0.9 10**(-3) eV**2 for
maximum mixing and (sin(2 theta)**2) > 0.18 for large deltam**2.Comment: 13 pages, Latex, submitted to Physics Letters
Limits on Neutrino Oscillations from the CHOOZ Experiment
We present new results based on the entire CHOOZ data sample. We find (at 90%
confidence level) no evidence for neutrino oscillations in the anti_nue
disappearance mode, for the parameter region given by approximately Delta m**2
> 7 x 10**-4 eV^2 for maximum mixing, and sin**2(2 theta) = 0.10 for large
Delta m**2. Lower sensitivity results, based only on the comparison of the
positron spectra from the two different-distance nuclear reactors, are also
presented; these are independent of the absolute normalization of the anti_nue
flux, the cross section, the number of target protons and the detector
efficiencies.Comment: 19 pages, 11 figures, Latex fil
Search for neutrino oscillations on a long base-line at the CHOOZ nuclear power station
This final article about the CHOOZ experiment presents a complete description
of the electron antineutrino source and detector, the calibration methods and
stability checks, the event reconstruction procedures and the Monte Carlo
simulation. The data analysis, systematic effects and the methods used to reach
our conclusions are fully discussed. Some new remarks are presented on the
deduction of the confidence limits and on the correct treatment of systematic
errors.Comment: 41 pages, 59 figures, Latex file, accepted for publication by
Eur.Phys.J.
Search for electron antineutrino interactions with the Borexino Counting Test Facility at Gran Sasso
Electron antineutrino interactions above the inverse beta decay energy of
protons (E_\bar{\nu}_e>1.8) where looked for with the Borexino Counting Test
Facility (CTF). One candidate event survived after rejection of background,
which included muon-induced neutrons and random coincidences. An upper limit on
the solar flux, assumed having the B solar neutrino energy
spectrum, of 1.1 cm~s (90% C.L.) was set with a 7.8
ton year exposure. This upper limit corresponds to a solar neutrino
transition probability, , of 0.02 (90% C.L.).
Predictions for antineutrino detection with Borexino, including geoneutrinos,
are discussed on the basis of background measurements performed with the CTF.Comment: 10 pages, 9 figures, 5 table
Measurement of the solar 8B neutrino rate with a liquid scintillator target and 3 MeV energy threshold in the Borexino detector
We report the measurement of electron neutrino elastic scattering from 8B
solar neutrinos with 3 MeV energy threshold by the Borexino detector in Gran
Sasso (Italy). The rate of solar neutrino-induced electron scattering events
above this energy in Borexino is 0.217 +- 0.038 (stat) +- 0.008 (syst) cpd/100
t, which corresponds to the equivalent unoscillated flux of (2.4 +- 0.4 (stat)
+- 0.1 (syst))x10^6 cm^-2 s^-1, in good agreement with measurements from SNO
and SuperKamiokaNDE. Assuming the 8B neutrino flux predicted by the high
metallicity Standard Solar Model, the average 8B neutrino survival probability
above 3 MeV is measured to be 0.29+-0.10. The survival probabilities for 7Be
and 8B neutrinos as measured by Borexino differ by 1.9 sigma. These results are
consistent with the prediction of the MSW-LMA solution of a transition in the
solar electron neutrino survival probability between the low energy
vacuum-driven and the high-energy matter-enhanced solar neutrino oscillation
regimes.Comment: 10 pages, 8 figures, 6 table
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Spectroscopy of geo-neutrinos from 2056 days of Borexino data
We report an improved geo-neutrino measurement with Borexino from 2056 days
of data taking. The present exposure is
protonyr. Assuming a chondritic Th/U mass ratio of 3.9, we obtain geo-neutrino events. The null
observation of geo-neutrinos with Borexino alone has a probability of (5.9). A geo-neutrino signal from the mantle is
obtained at 98\% C.L. The radiogenic heat production for U and Th from the
present best-fit result is restricted to the range 23-36 TW, taking into
account the uncertainty on the distribution of heat producing elements inside
the Earth.Comment: 4 pages, 4 figure
The Main Results of the Borexino Experiment
The main physical results on the registration of solar neutrinos and the
search for rare processes obtained by the Borexino collaboration to date are
presented.Comment: 8 pages, 8 figgures, To be published as Proceedings of the Third
Annual Large Hadron Collider Physics Conference, St. Petersburg, Russia, 201
Recent Borexino results and prospects for the near future
The Borexino experiment, located in the Gran Sasso National Laboratory, is an
organic liquid scintillator detector conceived for the real time spectroscopy
of low energy solar neutrinos. The data taking campaign phase I (2007 - 2010)
has allowed the first independent measurements of 7Be, 8B and pep fluxes as
well as the first measurement of anti-neutrinos from the earth. After a
purification of the scintillator, Borexino is now in phase II since 2011. We
review here the recent results achieved during 2013, concerning the seasonal
modulation in the 7Be signal, the study of cosmogenic backgrounds and the
updated measurement of geo-neutrinos. We also review the upcoming measurements
from phase II data (pp, pep, CNO) and the project SOX devoted to the study of
sterile neutrinos via the use of a 51Cr neutrino source and a 144Ce-144Pr
antineutrino source placed in close proximity of the active material.Comment: 8 pages, 11 figures. To be published as proceedings of Rencontres de
Moriond EW 201
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Solar neutrino with Borexino: results and perspectives
Borexino is a unique detector able to perform measurement of solar neutrinos
fluxes in the energy region around 1 MeV or below due to its low level of
radioactive background. It was constructed at the LNGS underground laboratory
with a goal of solar Be neutrino flux measurement with 5\% precision. The
goal has been successfully achieved marking the end of the first stage of the
experiment. A number of other important measurements of solar neutrino fluxes
have been performed during the first stage. Recently the collaboration
conducted successful liquid scintillator repurification campaign aiming to
reduce main contaminants in the sub-MeV energy range. With the new levels of
radiopurity Borexino can improve existing and challenge a number of new
measurements including: improvement of the results on the Solar and terrestrial
neutrino fluxes measurements; measurement of pp and CNO solar neutrino fluxes;
search for non-standard interactions of neutrino; study of the neutrino
oscillations on the short baseline with an artificial neutrino source (search
for sterile neutrino) in context of SOX project.Comment: 15 pages, 4 figure
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