770 research outputs found
Automation of NLO processes and decays and POWHEG matching in WHIZARD
We give a status report on the automation of next-to-leading order processes
within the Monte Carlo event generator WHIZARD, using GoSam and OpenLoops as
provider for one-loop matrix elements. To deal with divergences, WHIZARD uses
automated FKS subtraction, and the phase space for singular regions is
generated automatically. NLO examples for both scattering and decay processes
with a focus on e+e- processes are shown. Also, first NLO-studies of
observables for collisions of polarized leptons beams, e.g. at the ILC, will be
presented. Furthermore, the automatic matching of the fixed-order NLO
amplitudes with emissions from the parton shower within the POWHEG formalism
inside WHIZARD will be discussed. We also present results for top pairs at
threshold in lepton collisions, including matching between a resummed threshold
calculation and fixed-order NLO. This allows the investigation of more
exclusive differential observables.Comment: 5 pages, 3 figures, Talk presented at ACAT 2016 at UTFSM,
Valpara\'iso, Chil
Top Physics in WHIZARD
In this talk we summarize the top physics setup in the event generator
WHIZARD with a main focus on lepton colliders. This includes full six-, eight-
and ten-fermion processes, factorized processes and spin correlations. For
lepton colliders, QCD NLO processes for top quark physics are available and
will be discussed. A special focus is on the top-quark pair threshold, where a
special implementation combines a non-relativistic effective field theory
calculation augmented by a next-to-leading threshold logarithm resummation with
a continuum relativistic fixed-order QCD NLO simulation.Comment: 6 pages, 2 figures, Talk presented at the International Workshop on
Future Linear Colliders (LCWS15), Whistler, Canada, 2-6 November 201
Light dark forces at flavor factories
SuperB experiment could represent an ideal environment to test a new U (1)
symmetry related to light dark forces candidates. A promising discovery channel
is represented by the resonant production of a boson U, followed by its decay
into lepton pairs. Beyond approximations adopted in the literature, an exact
tree level calculation of the radiative processes and corresponding QED
backgrounds is performed, including also the most important higher-order
corrections. The calculation is implemented in a release of the generator
BabaYaga@NLO useful for data analysis and interpretation. The distinct features
of U boson production are shown and the statistical significance is analysed
Status of KLOE-2
In a few months the KLOE-2 detector is expected to start data taking at the
upgraded DANE -factory of INFN Laboratori Nazionali di
Frascati. It aims to collect 25 fb at the peak, and about 5
fb in the energy region between 1 and 2.5 GeV. We review the status and
physics program of the projectComment: 6 pages, 5 figures, to appear in the Proceedings of the PHIPSI09
Workshop, Oct 13-16, 2009, Beijing, Chin
Hadronic light-by-light scattering contribution to the muon g-2
We review recent developments concerning the hadronic light-by-light
scattering contribution to the anomalous magnetic moment of the muon. We first
discuss why fully off-shell hadronic form factors should be used for the
evaluation of this contribution to the g-2. We then reevaluate the numerically
dominant pion-exchange contribution in the framework of large-N_C QCD, using an
off-shell pion-photon-photon form factor which fulfills all QCD short-distance
constraints, in particular, a new short-distance constraint on the off-shell
form factor at the external vertex in g-2, which relates the form factor to the
quark condensate magnetic susceptibility in QCD. Combined with available
evaluations of the other contributions to hadronic light-by-light scattering
this leads to the new result a_{\mu}(LbyL; had) = (116 \pm 40) x 10^{-11}, with
a conservative error estimate in view of the many still unsolved problems. Some
potential ways for further improvements are briefly discussed as well. For the
electron we obtain the new estimate a_{e}(LbyL; had) = (3.9 \pm 1.3) x
10^{-14}.Comment: 6 pages, 1 figure, to be published in the proceedings of the PhiPsi09
workshop, Oct. 13-16, 2009, Beijing, Chin
Transport properties of heterogeneous materials derived from Gaussian random fields: Bounds and Simulation
We investigate the effective conductivity () of a class of
amorphous media defined by the level-cut of a Gaussian random field. The three
point solid-solid correlation function is derived and utilised in the
evaluation of the Beran-Milton bounds. Simulations are used to calculate
for a variety of fields and volume fractions at several different
conductivity contrasts. Relatively large differences in are observed
between the Gaussian media and the identical overlapping sphere model used
previously as a `model' amorphous medium. In contrast shows little
variability between different Gaussian media.Comment: 15 pages, 14 figure
Growth and shape of indium islands on molybdenum at micro-roughened spots created by femtosecond laser pulses
Indium islands on molybdenum coated glass can be grown in ordered arrays by surface structuring using a femtosecond laser. The effect of varying the molybdenum coated glass substrate temperature and the indium deposition rate on island areal density, volume and geometry is investigated and evaluated in a physical vapor deposition (PVD) process. The joined impact of growth conditions and spacing of the femtosecond laser structured spots on the arrangement and morphology of indium islands is demonstrated. The results yield a deeper understanding of the island growth and its precise adjustment to industrial requirements, which is indispensable for a technological application of such structures at a high throughput, for instance as precursors for the preparation of Cu(In,Ga)Se2 micro concentrator solar cells
Constraining the Hadronic Contributions to the Muon Anomalous Magnetic Moment
The mini-proceedings of the Workshop on "Constraining the hadronic
contributions to the muon anomalous magnetic moment" which included the "13th
meeting of the Radio MonteCarLow WG" and the "Satellite meeting R-Measurements
at BES-III" held in Trento from April 10th to 12th, 2013, are presented. This
collaboration meeting aims to bring together the experimental e+e- collider
communities from BaBar, Belle, BESIII, CMD2, KLOE, and SND, with theorists
working in the fields of meson transitions form factors, hadronic contributions
to (g-2)_\mu and effective fine structure constant, and development of Monte
Carlo generator and Radiative Corrections for precision e+e- and tau physics.Comment: 45 pages, 17 contributions. Editors: P. Masjuan and G. Venanzon
Regularly arranged indium islands on glass/molybdenum substrates upon femtosecond laser and physical vapor deposition processing
A bottom-up approach is presented for the production of arrays of indium
islands on a molybdenum layer on glass, which can serve as micro-sized
precursors for indium compounds such as copper-indium-gallium-diselenide used
in photovoltaics. Femtosecond laser ablation of glass and a subsequent
deposition of a molybdenumfilm or direct laser processing of the
molybdenumfilm both allow the preferential nucleation and growth of indium
islands at the predefined locations in a following indium-based physical vapor
deposition(PVD) process. A proper choice of laser and deposition parameters
ensures the controlled growth of indium islands exclusively at the laser
ablated spots. Based on a statistical analysis, these results are compared to
the non-structured molybdenumsurface, leading to randomly grown indium islands
after PVD
Steady State of microemulsions in shear flow
Steady-state properties of microemulsions in shear flow are studied in the
context of a Ginzburg-Landau free-energy approach. Explicit expressions are
given for the structure factor and the time correlation function at the one
loop level of approximation. Our results predict a four-peak pattern for the
structure factor, implying the simultaneous presence of interfaces aligned with
two different orientations.
Due to the peculiar interface structure a non-monotonous relaxation of the
time correlator is also found.Comment: 5 pages, 3 figure
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