5,584 research outputs found
Three Flavour Majorana Neutrinos with Magnetic Moments in a Supernova
The resonant transition effects MSW and NSFP for three flavour Majorana
neutrinos in a supernova are considered, where the transition magnetic moments
are likely to play a relevant role in neutrino physics. In this scenario, the
deformed thermal neutrino distributions are obtained for different choices of
the electron-tau mixing angle. Detailed predictions for the future large
neutrino detectors are also given in terms of the ratio between the spectra of
recoil electrons for deformed and undeformed spectra.Comment: 20 pages, LaTeX, 5 figures.p
Radiative quarkonium decays and the NMSSM Higgs interpretation of the HyperCP Sigma+ --> p mu+mu- events
We study the potential of radiative decays of the Upsilon(1S) and of the phi
mesons to search for a light pseudoscalar Higgs boson, proposed as a possible
interpretation of Sigma+ --> p mu+mu- events observed by the HyperCP
collaboration at Fermilab. We conclude that the detection of this signal should
certainly be possible with the current CLEO Upsilon(1S) data, and is within the
reach of KLOE in at least part of the range of couplings suggested by the
HyperCP findings.Comment: 6 pages, no figure
Investigating Supergiant Fast X-ray Transients with LOFT
Supergiant Fast X-ray Transients (SFXT) are a class of High-Mass X-ray
Binaries whose optical counterparts are O or B supergiant stars, and whose
X-ray outbursts are ~ 4 orders of magnitude brighter than the quiescent state.
LOFT, the Large Observatory For X-ray Timing, with its coded mask Wide Field
Monitor (WFM) and its 10 m^2 class collimated X-ray Large Area Detector (LAD),
will be able to dramatically deepen the knowledge of this class of sources. It
will provide simultaneous high S/N broad-band and time-resolved spectroscopy in
several intensity states, and long term monitoring that will yield new
determinations of orbital periods, as well as spin periods. We show the results
of an extensive set of simulations performed using previous observational
results of these sources obtained with Swift and XMM-Newton. The WFM will
detect all SFXT flares within its field of view down to a 15-20 mCrab in 5ks.
Our simulations describe the outbursts at several intensities
(F_(2-10keV)=5.9x10^-9 to 5.5x10^-10 erg cm^-2 s^-1), the intermediate and most
common state (10^-11 erg cm^-2 s^-1), and the low state (1.2x10^-12 to 5x10^-13
erg cm^-2 s^-1). We also considered large variations of N_H and the presence of
emission lines, as observed by Swift and XMM-Newton.Comment: Proceedings of the 5th International Symposium on High-Energy
Gamma-Ray Astronomy (Gamma2012), Heidelberg. 4 pages, 3 figures, 1 tabl
Swift monitoring of IGR J16418-4532
We report on the Swift observations of the candidate supergiant fast X-ray
transient (SFXT) IGR J16418-4532, which has an orbital period of ~3.7 d. Our
monitoring, for a total of ~43 ks, spans over three orbits and represents the
most intense and complete sampling along the orbital period of the light curve
of this source. If one assumes a circular orbit, the X-ray emission from this
source can be explained by accretion from a spherically symmetric clumpy wind
from a blue supergiant, composed of clumps with different masses, ranging from
~5x10^16 g to 10^21g.Comment: 4 pages; Proceedings, 5th International Symposium on High-Energy
Gamma-Ray Astronomy, (Gamma2012) Heidelberg, Germany, July 9-13th, 201
Color-flow decomposition of QCD amplitudes
We introduce a new color decomposition for multi-parton amplitudes in QCD,
free of fundamental-representation matrices and structure constants. This
decomposition has a physical interpretation in terms of the flow of color,
which makes it ideal for merging with shower Monte-Carlo programs. The
color-flow decomposition allows for very efficient evaluation of amplitudes
with many quarks and gluons, many times faster than the standard color
decomposition based on fundamental-representation matrices. This will increase
the speed of event generators for multi-jet processes, which are the principal
backgrounds to signals of new physics at colliders.Comment: 23 pages, 11 figures, version to appear on Phys. Rev.
A paradigmatic autistic phenotype associated with loss of PCDH11Y and NLGN4Y genes
Background: Most studies relative to Y chromosome abnormalities are focused on the sexual developmental disorders. Recently, a few studies suggest that some genes located on Y chromosome may be related to different neurodevelopment disorders. Case presentation: We report a child with sexual developmental disorder associated with a peculiar phenotype characterized by severe language impairment and autistic behaviour associated with a mosaicism [45,X(11)/46,XY(89)] and a partial deletion of the short and long arm of Y chromosome (del Yp11.31q11.23) that also involves the loss of both PCDH11Y and NLGN4Y genes. To our knowledge no study has ever reported the occurrence of the lack of both PCDH11Y and NLGN4Y located in the Y chromosome in the same patient. Conclusions: We hypothesized a functional complementary role of PCDH11Y and NLGN4Y within formation/maturation of the cerebral cortex. The impairment of early language development may be mainly related to the lack of PCDH11Y that underlies the early language network development and the later appearance of the autistic behaviour may be mainly related to deficit of inhibitory glicinergic neurotransmission NLGN4Y-linked
Soft X-ray characterisation of the long term properties of Supergiant Fast X-ray Transients
We perform the first high-sensitivity soft X-ray long-term monitoring with
Swift/XRT of three relatively unexplored Supergiant Fast X-ray Transients
(SFXTs), IGR J08408-4503, IGR J16328-4726, and IGR J16465-4507, whose hard
X-ray duty cycles are the lowest measured among the SFXT sample, and compare
their properties with those of the prototypical SFXTs. The behaviour of J08408
and J16328 resembles that of other SFXTs, and it is characterized by a
relatively high inactivity duty cycle (IDC) and pronounced dynamic range (DR)
in the X-ray luminosity. Like the SFXT prototypes, J08408 shows two distinct
populations of flares, the first one associated with the brightest outbursts
( erg s), the second one comprising less
bright events with 10 erg s. This
double-peaked distribution seems to be a ubiquitous feature of the extreme
SFXTs. The lower DR of J16328 suggests it is an intermediate SFXT. We find
J16465 is characterized by IDC5% and DR40, reminiscent of classical
supergiant HMXBs. The duty cycles measured with XRT are found to be comparable
with those reported previously by BAT and INTEGRAL, when the higher limiting
sensitivities of these instruments are taken into account and sufficiently long
observational campaigns are available. We prove that no clear correlation
exists between the duty cycles of the SFXTs and their orbital periods, which
makes it difficult to interpret the SFXT peculiar variability by only using
arguments related to the properties of supergiant star winds. Our findings
favour the idea that a correct interpretation of the SFXT phenomenology
requires a mechanism to strongly reduce the mass accretion rate onto the
compact object during most of its orbit around the companion, as proposed in a
number of theoretical works. [Abridged]Comment: Accepted for publication in Astronomy and Astrophysics. 18 pages, 8
figures, 8 table
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