6,070 research outputs found
Implication of the proton-deuteron radiative capture for Big Bang Nucleosynthesis
The astrophysical -factor for the radiative capture He in
the energy-range of interest for Big Bang Nucleosynthesis (BBN) is calculated
using an {\it ab-initio} approach. The nuclear Hamiltonian retains both two-
and three-nucleon interactions - the Argonne and the Urbana IX,
respectively. Both one- and many-body contributions to the nuclear current
operator are included. The former retain for the first time, besides the
leading order contribution ( is the nucleon mass), also the next-to-leading
order term, proportional to . The many-body currents are constructed in
order to satisfy the current conservation relation with the adopted Hamiltonian
model. The hyperspherical harmonics technique is applied to solve the
bound and scattering states. A particular attention is used in this second case
in order to obtain, in the energy range of BBN, an uncertainty on the
astrophysical -factor of the order or below 1 %. Then, in this energy
range, the -factor is found to be 10 % larger than the currently
adopted values.Part of this increase (1-3 %) is due to the one-body
operator, while the remaining is due to the new more accurate scattering wave
functions. We have studied the implication of this new determination for the
He -factor on deuterium primordial abundance. We find that
the predicted theoretical value for H/H is in excellent agreement with its
experimental determination, using the most recent determination of baryon
density of Planck experiment, and with a standard number of relativistic
degrees of freedom during primordial nucleosynthesis.Comment: 5 pages, 2 figures, submitted to Phys. Rev. Let
The astrophysical -factor and its implications for Big Bang Nucleosynthesis
The \alpha+d\rightarrow\, ^6{\rm Li}+\gamma radiative capture is studied in
order to predict the Li primordial abundance. Within a two-body framework,
the particle and the deuteron are considered the structureless
constituents of Li. Five potentials are used to solve the
two-body problem: four of them are taken from the literature, only one having
also a tensor component. A fifth model is here constructed in order to
reproduce, besides the Li static properties as binding energy, magnetic
dipole and electric quadrupole moments, also the -state asymptotic
normalization coefficient (ANC). The two-body bound and scattering problem is
solved with different techniques, in order to minimize the numerical
uncertainty of the present results. The long-wavelength approximation is used,
and therefore only the electric dipole and quadrupole operators are retained.
The astrophysical -factor is found to be significantly sensitive to the ANC,
but in all the cases in good agreement with the available experimental data.
The theoretical uncertainty has been estimated of the order of few % when the
potentials which reproduce the ANC are considered, but increases up to % when all the five potential models are retained. The effect of this
-factor prediction on the Li primordial abundance is studied, using the
public code PArthENoPE. For the five models considered here we find H, with the baryon density parameter in
the 3- range of Planck 2015 analysis, .Comment: 26 pages, 9 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
Modernization of Manufacturing with Cybersecurity at the Forefront
With the proliferation of Industrial Control Systems (ICSs), manufacturing processes have improved over the last 30 years, however, the organizational focus to securely exchange and process information to/from integrated systems has been consistently lacking. These environments continue to be susceptible to security vulnerabilities, despite history [15] showing that cybersecurity exposures in manufacturing have largely gone unaddressed and continue to rise [52]. This study evaluates cybersecurity challenges in the industry and proposes recommendations for practical and fiscally responsible defense-in-depth cybersecurity protections for manufacturing environments. The business operating model, how ICSs became pervasive, as well as the major components that enable the operational technology (OT) were evaluated. With an understanding of the traditional network architecture for the industry [37], the rapidly evolving challenges facing the industry were examined. These challenges are impactful to the traditional and slow to change manufacturing operating model that has not focused on the necessary cyber protections for their OT environments. In addition, the industry is now facing game-changing technological concepts such as advanced manufacturing and Industry 4.0 that bring new complex challenges and cyber threats, unfamiliar to most in the industry. This is all underpinned by an organizational divide where the personnel most knowledgeable with the modern technology and cyber risks, in the majority of cases, are not responsible for the OT architecture and security. These headwinds impact an industry which spends the least on IT and cyber security than any other industry, globally [22]. The cyber risks and challenges in the industry are diverse, spanning technological and organizational competencies, stemming from purpose built components which operate in an ecosystem where cybersecurity is an afterthought. As a means to close the gap, practical and reasonable recommendations to address these problems are discussed; some specific and unique to the manufacturing industry while others are fundamental applications discussed with a manufacturing industry lens, which are commonly ignored due to perceived complexity, cost or simply lack of awareness. Lastly, a number of these recommendations were selected for further evaluation and implementation; challenges, approach, benefits and outcomes are shared showing measureable improvements to the cybersecurity posture of the organization.Master of ScienceComputer and Information Science, College of Engineering & Computer ScienceUniversity of Michigan-Dearbornhttps://deepblue.lib.umich.edu/bitstream/2027.42/147433/1/49698122_CIS699 - Mangano Thesis - Modernization of Manufacturing with Cybersecurity at the Forefront - Final 121018-v4.pdfDescription of 49698122_CIS699 - Mangano Thesis - Modernization of Manufacturing with Cybersecurity at the Forefront - Final 121018-v4.pdf : Thesi
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
Minimal Gauge Invariant Classes of Tree Diagrams in Gauge Theories
We describe the explicit construction of groves, the smallest gauge invariant
classes of tree Feynman diagrams in gauge theories. The construction is valid
for gauge theories with any number of group factors which may be mixed. It
requires no summation over a complete gauge group multiplet of external matter
fields. The method is therefore suitable for defining gauge invariant classes
of Feynman diagrams for processes with many observed final state particles in
the standard model and its extensions.Comment: 13 pages, RevTeX (EPS figures
MadEvent: Automatic Event Generation with MadGraph
We present a new multi-channel integration method and its implementation in
the multi-purpose event generator MadEvent, which is based on MadGraph. Given a
process, MadGraph automatically identifies all the relevant subprocesses,
generates both the amplitudes and the mappings needed for an efficient
integration over the phase space, and passes them to MadEvent. As a result, a
process-specific, stand-alone code is produced that allows the user to
calculate cross sections and produce unweighted events in a standard output
format. Several examples are given for processes that are relevant for physics
studies at present and forthcoming colliders.Comment: 11 pages, MadGraph home page at http://madgraph.physics.uiuc.ed
Disentangling neutrino-nucleon cross section and high energy neutrino flux with a km^3 neutrino telescope
The energy--zenith angular event distribution in a neutrino telescope
provides a unique tool to determine at the same time the neutrino-nucleon cross
section at extreme kinematical regions, and the high energy neutrino flux. By
using a simple parametrization for fluxes and cross sections, we present a
sensitivity analysis for the case of a km^3 neutrino telescope. In particular,
we consider the specific case of an under-water Mediterranean telescope placed
at the NEMO site, although most of our results also apply to an under-ice
detector such as IceCube. We determine the sensitivity to departures from
standard values of the cross sections above 1 PeV which can be probed
independently from an a-priori knowledge of the normalization and energy
dependence of the flux. We also stress that the capability to tag downgoing
neutrino showers in the PeV range against the cosmic ray induced background of
penetrating muons appears to be a crucial requirement to derive meaningful
constraints on the cross section.Comment: 10 pages, 28 figure
High Energy Neutrinos with a Mediterranean Neutrino Telescope
The high energy neutrino detection by a km^3 Neutrino Telescope placed in the
Mediterranean sea provides a unique tool to both determine the diffuse
astrophysical neutrino flux and the neutrino-nucleon cross section in the
extreme kinematical region, which could unveil the presence of new physics.
Here is performed a brief analysis of possible NEMO site performances.Comment: 4 pages, 3 figures, Proceedings of the 30th ICRC 200
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