165 research outputs found
Mossbauer neutrinos in quantum mechanics and quantum field theory
We demonstrate the correspondence between quantum mechanical and quantum
field theoretical descriptions of Mossbauer neutrino oscillations. First, we
compute the combined rate of Mossbauer neutrino emission, propagation,
and detection in quantum field theory, treating the neutrino as an internal
line of a tree level Feynman diagram. We include explicitly the effect of
homogeneous line broadening due to fluctuating electromagnetic fields in the
source and detector crystals and show that the resulting formula for
is identical to the one obtained previously (Akhmedov et al., arXiv:0802.2513)
for the case of inhomogeneous line broadening. We then proceed to a quantum
mechanical treatment of Mossbauer neutrinos and show that the oscillation,
coherence, and resonance terms from the field theoretical result can be
reproduced if the neutrino is described as a superposition of Lorentz-shaped
wave packet with appropriately chosen energies and widths. On the other hand,
the emission rate and the detection cross section, including localization and
Lamb-Mossbauer terms, cannot be predicted in quantum mechanics and have to be
put in by hand.Comment: LaTeX, 16 pages, 1 figure; v2: typos corrected; matches published
versio
Probing Non-Standard Couplings of Neutrinos at the Borexino Detector
The present experimental status does not exclude weak-strength non-standard
interactions of neutrinos with electrons. These interactions can be revealed in
solar neutrino experiments. Our discussion covers several aspects related to
this issue. First, we perform an analysis of the Super Kamiokande and SNO data
to investigate their sensitivity to such interactions. In particular, we show
that the \nu_e oscillation into sterile neutrinos can be still allowed if \nu_e
has extra interactions of the proper strength. Second, we suggest that the
Borexino detector can provide good signatures for these non-standard
interactions. Indeed, in Borexino the shape of the recoil electron spectrum
from the \nu e \to \nu e scattering essentially does not depend on the solar
neutrino conversion details, since most of the signal comes from the
mono-energetic ^7Be neutrinos. Hence, the partial conversion of solar \nu_e
into a a nearly equal mixture of \nu_\mu and \nu_\tau, as is indicated by the
atmospheric neutrino data, offers the chance to test extra interactions of
\nu_\tau, or of \nu_e itself.Comment: 17 LaTeX pages, 15 postscript figures, uses epsfig.sty. More extended
discussion about the spectral deformation for both Super-Kamiokande and
Borexino; new figures are adde
Low Energy Solar Neutrinos and Spin Flavour Precession
The possibility that the Gallium data effectively indicates a time modulation
of the solar active neutrino flux in possible connection to solar activity is
examined on the light of spin flavour precession to sterile neutrinos as a
subdominant process in addition to oscillations. We distinguish two sets of
Gallium data, relating them to high and low solar activity. Such modulation
affects principally the low energy neutrinos ( and ) so that the
effect, if it exists, will become most clear in the forthcoming Borexino and
LENS experiments and will provide evidence for a neutrino magnetic moment.
Using a model previously developed, we perform two separate fits in relation to
low and high activity periods to all solar neutrino data. These fits include
the very recent charged current spectrum from the SNO experiment. We also
derive the model predictions for Borexino and LENS experiments.Comment: 20 pages, 5 ps figures, 1 eps figure, final version to be published
in JHE
Neutrino Signal Variation in KamLAND
Large Mixing Angle (LMA) neutrino oscillation is the main solution for the
long-standing Solar Neutrino Problem (SNP). Whether there is any subdominant
effect accompanying the dominant LMA solution can not be ruled out at the
moment, but will be settled by the forthcoming data from highly skilled real
time experiments targeting essentially the low energy domain of solar
neutrinos. Assuming a subdominant effect converting one of the active neutrinos
into a sterile partner in the varying solar field with changing sunspot
activity, we performed field-profile-independent predictions for
neutrino signal variation, which might be tested in the KamLAND's future solar
neutrino detection program. We found that after a substantial reduction of
background and running of KamLAND solar mode through the sunspot maximum period
(around 2010 - 2012), when the solar field at the resonance may vary from few
to , the subdominant time variation effect might be clearly
visible (more than ) for neutrinos.Comment: 12 pages, 4 figures, typos corrected. To appear in JHE
Insights into the Mind of a Trojan Designer: The Challenge to Integrate a Trojan into the Bitstream
The threat of inserting hardware Trojans during the design, production, or
in-field poses a danger for integrated circuits in real-world applications. A
particular critical case of hardware Trojans is the malicious manipulation of
third-party FPGA configurations. In addition to attack vectors during the
design process, FPGAs can be infiltrated in a non-invasive manner after
shipment through alterations of the bitstream. First, we present an improved
methodology for bitstream file format reversing. Second, we introduce a novel
idea for Trojan insertion
Can the Zee Model Explain the Observed Neutrino Data?
The eigenvalues and mixing angles in the Zee model are investigated
parameter-independently. When we require |\Delta m^2_{12}/\Delta m^2_{23}| \ll
1 in order to understand the solar and atmospheric data simultaneously, the
only solution is one which gives bi-maximal mixing. It is pointed out that the
observed values \sin^2 2\theta_{solar} \simeq 0.66 in the MSW LMA solution
cannot be explained within the framework of the Zee model, because we derive a
severe constraint on the value of \sin^2 2 \theta_{solar}, \sin^2 2
\theta_{solar} \geq 1 -(1/16)(\Delta m^2_{solar}/\Delta m^2_{atm})^2.Comment: Latex file, 10 pages, 1 figure, explanations and references added,
typos corrected, to be published in Phys.Rev.
A New Approach to Background Subtraction in Low-Energy Neutrino Experiments
We discuss a new method to extract neutrino signals in low energy
experiments. In this scheme the symmetric nature of most backgrounds allows for
direct cancellation from data. The application of this technique to the Palo
Verde reactor neutrino oscillation experiment allowed us to reduce the
measurement errors on the anti-neutrino flux from % to %. We
expect this method to substantially improve the data quality in future low
background experiments such as KamLAND and LENS.Comment: 7 pages, 2 figure
Discriminating among Earth composition models using geo-antineutrinos
It has been estimated that the entire Earth generates heat corresponding to
about 40 TW (equivalent to 10,000 nuclear power plants) which is considered to
originate mainly from the radioactive decay of elements like U, Th and K,
deposited in the crust and mantle of the Earth. Radioactivity of these elements
produce not only heat but also antineutrinos (called geo-antineutrinos) which
can be observed by terrestrial detectors. We investigate the possibility of
discriminating among Earth composition models predicting different total
radiogenic heat generation, by observing such geo-antineutrinos at Kamioka and
Gran Sasso, assuming KamLAND and Borexino (type) detectors, respectively, at
these places. By simulating the future geo-antineutrino data as well as reactor
antineutrino background contributions, we try to establish to which extent we
can discriminate among Earth composition models for given exposures (in units
of kt yr) at these two sites on our planet. We use also information on
neutrino mixing parameters coming from solar neutrino data as well as KamLAND
reactor antineutrino data, in order to estimate the number of geo-antineutrino
induced events.Comment: 24 pages, 10 figures, final version to appear in JHE
Performances and stability of a 2.4 ton Gd organic liquid scintillator target for antineutrino detection
In this work we report the performances and the chemical and physical
properties of a (2 x 1.2) ton organic liquid scintillator target doped with Gd
up to ~0.1%, and the results of a 2 year long stability survey. In particular
we have monitored the amount of both Gd and primary fluor actually in solution,
the optical and fluorescent properties of the Gd-doped liquid scintillator
(GdLS) and its performances as a neutron detector, namely neutron capture
efficiency and average capture time. The experimental survey is ongoing, the
target being continuously monitored. After two years from the doping time the
performances of the Gd-doped liquid scintillator do not show any hint of
degradation and instability; this conclusion comes both from the laboratory
measurements and from the "in-tank" measurements. This is the largest stable
Gd-doped organic liquid scintillator target ever produced and continuously
operated for a long period
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