327 research outputs found
Dipole nanolaser
A "dipole" laser is proposed consisting of a nanoparticle and a two-level system with population inversion. If the threshold conditions are fulfilled, the dipole interaction between the two-level system and the nanoparticle leads to coherent oscillations in the polarization of the particles, even in the absence of an external electromagnetic field. The emitted radiation has a dipolar distribution. It does not need an optical cavity, and has a very small volume, 0.1 mu m(3), which can be important for applications in microelectronics. Estimates of the threshold conditions are carried out for a dipole laser composed of a quantum dot and a silver nanoparticle
Contribution of higher meson resonances to the electromagnetic -meson mass difference
Modifications of the DGMLY relation for calculation of electromagnetic
-meson mass difference based on the Chiral Symmetry Restoration phenomenon
at high energies as well as the Operator Product Expansion of quark densities
for vector () and axial-vector () meson fields difference are
proposed. In the calculations higher meson resonances in vector and
axial-vector channels are taken into account. It is shown that the inclusion of
the first and radial excitations improves the results for
electromagnetic -meson mass difference as compared with the previous ones.
Estimations on the electromagnetic and -meson decay constants and
the constant of effective chiral Lagrangian are obtained from the
generalized Weinberg sum rules.Comment: Latex2e, 10 pages, submitted to Yad. Phy
On the possiblity of detecting Solar pp-neutrino with a large volume liquid organic scintillator detector
It is shown that a large volume liquid organic scintillator detector with an
energy resolution of 10 keV at 200 keV 1 sigma will be sensitive to solar
pp-neutrino, if operated at the target radiopurity levels for the Borexino
detector, or the solar neutrino project of KamLAND.Comment: 18 pages, 2 figures, 4 tables. Contributed paper to the
Nonaccelerating New Neutrino Physic. NANP-2003, Dubna. To be published in
Phys.At.Nucl.(2004
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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
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
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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Search for Solar Axions Produced in Reaction with Borexino Detector
A search for 5.5-MeV solar axions produced in the reaction was performed using the Borexino detector. The Compton
conversion of axions to photons, ; the
axio-electric effect, ; the decay of axions into
two photons, ; and inverse Primakoff conversion on
nuclei, , are considered. Model independent
limits on axion-electron (), axion-photon (), and
isovector axion-nucleon () couplings are obtained: and at 1 MeV (90% c.l.). These limits are
2-4 orders of magnitude stronger than those obtained in previous
laboratory-based experiments using nuclear reactors and accelerators.Comment: 11 pages, 7 figures, submitted to Phys.Rev.
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Measurement of geo-neutrinos from 1353 days of Borexino
We present a measurement of the geo--neutrino signal obtained from 1353 days
of data with the Borexino detector at Laboratori Nazionali del Gran Sasso in
Italy. With a fiducial exposure of (3.69 0.16) proton
year after all selection cuts and background subtraction, we detected
(14.3 4.4) geo-neutrino events assuming a fixed chondritic mass Th/U
ratio of 3.9. This corresponds to a geo-neutrino signal = (38.8
12.0) TNU with just a 6 probability for a null geo-neutrino
measurement. With U and Th left as free parameters in the fit, the relative
signals are = (10.6 12.7) TNU and =
(26.5 19.5) TNU. Borexino data alone are compatible with a mantle
geo--neutrino signal of (15.4 12.3) TNU, while a combined analysis with
the KamLAND data allows to extract a mantle signal of (14.1 8.1) TNU. Our
measurement of a reactor anti--neutrino signal =
84.5 TNU is in agreement with expectations in the presence of
neutrino oscillations.Comment: 9 pages, 6 figure
Low-energy (anti)neutrino physics with Borexino: Neutrinos from the primary proton-proton fusion process in the Sun
The Sun is fueled by a series of nuclear reactions that produce the energy
that makes it shine. The primary reaction is the fusion of two protons into a
deuteron, a positron and a neutrino. These neutrinos constitute the vast
majority of neutrinos reaching Earth, providing us with key information about
what goes on at the core of our star. Several experiments have now confirmed
the observation of neutrino oscillations by detecting neutrinos from secondary
nuclear processes in the Sun; this is the first direct spectral measurement of
the neutrinos from the keystone proton-proton fusion. This observation is a
crucial step towards the completion of the spectroscopy of pp-chain neutrinos,
as well as further validation of the LMA-MSW model of neutrino oscillations.Comment: Proceedings from NOW (Neutrino Oscillation Workshop) 201
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