641 research outputs found
An Integrated Tool for Loop Calculations: aITALC
aITALC, a new tool for automating loop calculations in high energy physics,
is described. The package creates Fortran code for two-fermion scattering
processes automatically, starting from the generation and analysis of the
Feynman graphs. We describe the modules of the tool, the intercommunication
between them and illustrate its use with three examples.Comment: 24 pages, 5 figures, 8 table
Automatized calculation of 2-fermion production with DIANA and aITALC
The family of two fermion final states is among the cleanest final states at
the International Linear Collider (ILC) project. The package aITALC has been
developed for a calculation of their production cross sections, and we present
here benchmark numerical results in one loop approximation in the electroweak
Standard Model. We are using packages like QGRAF, DIANA, FORM, LOOPTOOLS for
intermediate steps.Comment: Contribution to the proceedings of the International Conference on
Linear Colliders (LCWS 04), Paris, April 19-23, 2004. 5 pages, 1 figure, 5
table
Automated calculations for massive fermion production with aITALC
The package aITALC has been developed for the automated calculation of
radiative corrections to two-fermion production at colliders. The
package uses Diana, Qgraf, Form, Fortran, FF, LoopTools, and further unix/linux
tools. Numerical results are presented for .Comment: Contribution to the proceedings of "Loops and Legs in Quantum Field
Theory 2004", Zinnowitz, Usedom Island, Germany, April 2004. 5 pages, latex,
espcrc2, 5 figures, 1 tabl
Towards high precision predictions for top quark pair production and decay at a linear collider
We report on the progress in work on improving precision of the standard model theoretical predictions for the top quark pair production and Decay into six fermions at a linear collider. Two programs have been combined
into a single Monte Carlo program: eett6f, a MC program for e+e− ! 6f, and topfit, a program for electroweak radiative corrections to e+e− ! t¯t. The MC program is described and preliminary numerical results are shown
O(alpha) electroweak corrections to the processes e+e- -> tau-tau+, c bar-c, b bar-b, t bar-t: a comparison
We present the electroweak one-loop corrections to the processes e+e- -> f
bar-f, f = tau, c, b, t, at energies relevant for a future linear collider. The
results of two independent calculations are compared and agreement is found at
a technical-precision level of ten to twelve digits.Comment: 14 pages latex, 1 figure, 9 tables, contribution to the LC notes of
the ECFA/DESY Linear Collider Workshop series. Revised version (some eqs.
corrected, one definition added, two references added to text. Results
unchanged
ArCLight - a Compact Dielectric Large-Area Photon Detector
ArCLight is a novel device for detecting scintillation light over large areas
with Photon Detection Efficiency (PDE) of the order of a few percent. Its
robust technological design allows for efficient use in large-volume particle
detectors, such as Liquid Argon Time Projection Chambers (LArTPCs) or liquid
scintillator detectors. Due to its dielectric structure it can be placed inside
volumes with high electric field. It could potentially replace vacuum
PhotoMultiplier Tubes (PMTs) in applications where high PDE is not required.
The photon detection efficiency for a 10x10cm2 detector prototype was measured
to be in the range of 0.8% to 2.2% across the active area
Automated use of DIANA for two-fermion production at colliders
We describe packages for the calculation of radiative corrections to
two-fermion production at colliders. The packages use DIANA, and also QGRAF,
FORM, Fortran, and further unix/linux tools. The one-loop calculations in the
Standard Model are highly automatized with the package aITALC. Further, the
automatic determination of all the matrix elements for two-loop corrections to
massive Bhabha scattering in QED and the classification of their topologies and
prototypes is done with DIANA. A generalization to the Standard Model is
straightforward.Comment: To appear in the proceedings of ACAT03, Dec 2003, KEK, Japa
First order radiative corrections to Bhabha scattering in dimensions
The luminosity measurement at the projected International Linear
Collider ILC is planned to be performed with forward Bhabha scattering with an
accuracy of the order of . A theoretical prediction of the
differential cross-section has to include one-loop weak corrections, with
leading higher order terms, and the complete two-loop QED corrections. Here, we
present the weak part and the virtual one-loop photonic corrections. For the
photonic corrections, the expansions in are derived with
inclusion of the terms of order in order to match the two-loop
accuracy. For the photonic box master integral in dimensions we compare
several different methods of evaluation.Comment: 35 pages, 3 figures, 2 tables, uses feynmp.sty, references update
Brain regions that support accurate speech production after damage to Broca's area
Broca's area in the posterior half of the left inferior frontal gyrus has traditionally been considered an important node in the speech production network. Nevertheless, recovery of speech production has been reported, to different degrees, within a few months of damage to Broca's area. Importantly, contemporary evidence suggests that, within Broca's area, its posterior part (i.e. pars opercularis) plays a more prominent role in speech production than its anterior part (i.e. pars triangularis). In this study, we therefore investigated the brain activation patterns that underlie accurate speech production following stroke damage to the opercular part of Broca's area. By combining functional MRI and 13 tasks that place varying demands on speech production, brain activation was compared in (i) seven patients of interest with damage to the opercular part of Broca's area; (ii) 55 neurologically intact controls; and (iii) 28 patient controls with left-hemisphere damage that spared Broca's area. When producing accurate overt speech responses, the patients with damage to the left pars opercularis activated a substantial portion of the normal bilaterally distributed system. Within this system, there was a lesion-site-dependent effect in a specific part of the right cerebellar Crus I where activation was significantly higher in the patients with damage to the left pars opercularis compared to both neurologically intact and patient controls. In addition, activation in the right pars opercularis was significantly higher in the patients with damage to the left pars opercularis relative to neurologically intact controls but not patient controls (after adjusting for differences in lesion size). By further examining how right Crus I and right pars opercularis responded across a range of conditions in the neurologically intact controls, we suggest that these regions play distinct roles in domain-general cognitive control. Finally, we show that enhanced activation in the right pars opercularis cannot be explained by release from an inhibitory relationship with the left pars opercularis (i.e. dis-inhibition) because right pars opercularis activation was positively related to left pars opercularis activation in neurologically intact controls. Our findings motivate and guide future studies to investigate (i) how exactly right Crus I and right pars opercularis support accurate speech production after damage to the opercular part of Broca's area and (ii) whether non-invasive neurostimulation to one or both of these regions boosts speech production recovery after damage to the opercular part of Broca's area
Scalar field scattering by a Lifshitz black hole under a non-minimal coupling
We study the behavior of a scalar field under a z = 3 Lifshitz black hole
background, in a way that is non-minimally coupled to the gravitational field.
A general analytical solution is obtained along with two sets of quasinormal
modes associated to different boundary conditions that can be imposed on the
scalar field, non-minimal coupling parameter appears explicitly on these
solutions. Stability of quasinormal modes can be studied and ensured for both
cases. Also, the reflection and absorption coefficients are calculated, as well
as the absorption cross section which features an interesting behavior because
of being attenuated by terms strongly dependant on the non-minimal coupling. By
a suitable change of variables a soliton solution can also be obtained and the
stability of the quasinormal modes are studied and ensured
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