17,051 research outputs found
Z boson production in proton-lead collisions at the LHC accounting for transverse momenta of initial partons
We perform a calculation of inclusive boson production in proton-lead
collisions at the LHC taking into account the transverse momenta of the initial
partons. We use the framework of -factorization combining transverse
momentum dependent parton distributions (TMDs) with off-shell matrix elements.
In order to do it we need to construct appropriate TMDs for lead nuclei which
is done using the parton branching method. Our computations are compared with
data from CMS taken at TeV. The results are in good agreement
with the measurements especially the transverse momentum distribution of the
boson.Comment: 17 pages, 12 figure
Unified formulation of a family of iterative solvers for power systems analysis
This paper illustrates the construction of a new class of iterative solvers for power flow calculations based on the method of Alternating Search Directions. This method is fit to the particular algebraic structure of the power flow problem resulting from the combination of a globally linear set of equations and nonlinear local relations imposed by power conversion devices, such as loads and generators. The choice of the search directions is shown to be crucial for improving the overall robustness of the solver. A noteworthy advantage is that constant search directions yield stationary methods that, in contrast with Newton or Quasi-Newton methods, do not require the evaluation of the Jacobian matrix. Such directions can be elected to enforce the convergence to the high voltage operative solution. The method is explained through an intuitive example illustrating how the proposed generalized formulation is able to include other nonlinear solvers that are classically used for power flow analysis, thus offering a unified view on the topic. Numerical experiments are performed on publicly available benchmarks for large distribution and transmission systems.Peer ReviewedPostprint (author's final draft
Bubbles from Nothing
Within the framework of flux compactifications, we construct an instanton
describing the quantum creation of an open universe from nothing. The solution
has many features in common with the smooth 6d bubble of nothing solutions
discussed recently, where the spacetime is described by a 4d compactification
of a 6d Einstein-Maxwell theory on S^2 stabilized by flux. The four-dimensional
description of this instanton reduces to that of Hawking and Turok. The choice
of parameters uniquely determines all future evolution, which we additionally
find to be stable against bubble of nothing instabilities.Comment: 19 pages, 6 figure
Differential elastic electron scattering cross sections for CClâ by 1.5â100 eV energy electron impact
We report absolute elastic differential, integral and momentum transfer cross sections for electron interactions with CClâ. The incident electron energy range is 1.5-100 eV, and the scattered electron angular range for the differential measurements varies from 15°-130°. The absolute scale of the differential cross section was set using the relative flow technique with helium as the reference species. Comparison with previous total cross sections shows good agreement. Atomic-like behaviour in this scattering system is shown here for the first time, and is further investigated by comparing the CClâ elastic cross sections to recent results on the halomethanes and atomic chlorine at higher impact energies [H. Kato, T. Asahina, H. Masui, M. Hoshino, H. Tanaka, H. Cho, O. IngĂłlfsson, F. Blanco, G. Garcia, S. J. Buckman, and M. J. Brunger, J. Chem. Phys. 132, 074309 (2010)].This work was conducted under the support of the
Japanese Ministry of Education, Sport, Culture and Technology.
H.K. acknowledges the Japan Society for the Promotion
of Science (JSPS) for his fellowships as grants-in-aid for scientific
research. S.J.B also acknowledges the JSPS Invitation
Fellowship for Research in Japan
Absolute elastic differential cross sections for electron scattering by C6H5CH3 and C6H5CF3 at 1.5â200 eV: a comparative experimental and theoretical study with C6H6
We present absolute differential cross sections DCS for elastic scattering from two benzene derivatives
C6H5CH3 and C6H5CF3. The crossed-beam method was used in conjunction with the relative flow technique
using helium as the reference gas to obtain absolute values. Measurements were carried out for scattering
angles 15° â130° and impact energies 1.5â200 eV. DCS results for these two molecules were compared to
those of C6H6 from our previous study. We found that 1 these three molecules have DCS with very similar
magnitudes and shapes over the energy range 1.5â200 eV, although DCS for C6H5CF3 increase steeply toward
lower scattering angles due to the dipole moment induced long-range interaction at 1.5 and 4.5 eV, and 2 that
the molecular structure of the benzene ring significantly determines the collision dynamics. From the measured
DCS, elastic integral cross sections have been calculated. Furthermore, by employing a corrected form of the
independent-atom method known as the screen corrected additive rule, DCS calculations have been carried out
without any empirical parameter fittings, i.e., in an ab initio nature. Results show that the calculated DCS are
in excellent agreement with the experimental values at 50, 100, and 200 eV
Field theory simulation of Abelian-Higgs cosmic string cusps
We have performed a lattice field theory simulation of cusps in Abelian-Higgs
cosmic strings. The results are in accord with the theory that the portion of
the strings which overlaps near the cusp is released as radiation. The radius
of the string cores which must touch to produce the evaporation is
approximately in natural units. In general, the modifications to the
string shape due to the cusp may produce many cusps later in the evolution of a
string loop, but these later cusps will be much smaller in magnitude and more
closely resemble kinks.Comment: 9 pages, RevTeX, 13 figures with eps
The form of cosmic string cusps
We classify the possible shapes of cosmic string cusps and how they transform
under Lorentz boosts. A generic cusp can be brought into a form in which the
motion of the cusp tip lies in the plane of the cusp. The cusp whose motion is
perpendicular to this plane, considered by some authors, is a special case and
not the generic situation.
We redo the calculation of the energy in the region where the string overlaps
itself near a cusp, which is the maximum energy that can be released in
radiation. We take into account the motion of a generic cusp and the resulting
Lorentz contraction of the string core. The result is that the energy scales as
instead of the usual value of , where is the
string radius and and is the typical length scale of the string. Since for cosmological strings, the radiation is strongly suppressed and could
not be observed.Comment: 15 pages, ReVTex, 2 postscript figures with eps
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