3,178 research outputs found
QED challenges at FCC-ee precision measurements
The expected experimental precision of the rates and asymmetries in the
Future Circular Collider with electron positron beams (FCC-ee) in the centre of
the mass energy range 88-365GeV considered for construction in CERN, will be
better by a factor 5-200. This will be thanks to very high luminosity, factor
up to higher than in the past LEP experiments. This poses the
extraordinary challenge of improving the precision of the Standard Model
predictions by a comparable factor. In particular the perturbative calculations
of the trivial QED effects, which have to be removed from the experimental
data, are considered to be a major challenge for almost all quantities to be
measured at FCC-ee. The task of this paper is to summarize on the "state of the
art" in this class of the calculations left from the LEP era and to examine
what is to be done to match the precision of the FCC-ee experiments -- what
kind of technical advancements are necessary. The above analysis will be done
for most important observables of the FCC-ee like the total cross sections near
and threshold, charge asymmetries, the invisible width of boson,
the spin asymmetry from lepton decay and the luminosity measurement.Comment: Corrected author's name in ref. [106
Perturbiner Methods for Effective Field Theories and the Double Copy
Perturbiner expansion provides a generating function for all Berends-Giele
currents in a given quantum field theory. We apply this method to various
effective field theories with and without color degrees of freedom. In the
colored case, we study the U(N) non-linear sigma model of Goldstone bosons
(NLSM) in a recent parametrization due to Cheung and Shen, as well as its
extension involving a coupling to the bi-adjoint scalar. We propose a
Lagrangian and a Cachazo-He-Yuan formula for the latter valid in multi-trace
sectors and systematically calculate its amplitudes. Furthermore, we make a
similar proposal for a higher-derivative correction to NLSM that agrees with
the subleading order of the abelian Z-theory. In the colorless cases, we
formulate perturbiner expansions for the special Galileon and Born-Infeld
theories. Finally, we study Kawai-Lewellen-Tye-like double-copy relations for
Berends-Giele currents between the above colored and colorless theories. We
find that they hold up to pure gauge terms, but without the need for further
field redefinitions.Comment: 44 page
Exact solutions of the QCD evolution equations using Monte Carlo method
We present the exact and precise (~0.1%) numerical solution of the QCD
evolution equations for the parton distributions in a wide range of and
using Monte Carlo (MC) method, which relies on the so-called Markovian
algorithm. We point out certain advantages of such a method with respect to the
existing non-MC methods. We also formulate a challenge of constructing
non-Markovian MC algorithm for the evolution equations for the initial state
QCD radiation with tagging the type and of the exiting parton. This seems
to be within the reach of the presently available computer CPUs and the
sophistication of the MC techniques
Non-Markovian Monte Carlo Algorithm for the Constrained Markovian Evolution in QCD
We revisit the challenging problem of finding an efficient Monte Carlo (MC)
algorithm solving the constrained evolution equations for the initial-state QCD
radiation. The type of the parton (quark, gluon) and the energy fraction x of
the parton exiting emission chain (entering hard process) are predefined, i.e.
constrained throughout the evolution. Such a constraint is mandatory for any
realistic MC for the initial state QCD parton shower. We add one important
condition: the MC algorithm must not require the a priori knowledge of the full
numerical exact solutions of the evolution equations, as is the case in the
popular ``Markovian MC for backward evolution''. Our aim is to find at least
one solution of this problem that would function in practice. Finding such a
solution seems to be definitely within the reach of the currently available
computer CPUs and the sophistication of the modern MC techniques. We describe
in this work the first example of an efficient solution of this kind. Its
numerical implementation is still restricted to the pure gluon-strahlung. As
expected, it is not in the class of the so-called Markovian MCs. For this
reason we refer to it as belonging to a class of non-Markovian MCs. We show
that numerical results of our new MC algorithm agree very well (to 0.2%) with
the results of the other MC program of our own (unconstrained Markovian) and
another non-MC program QCDnum16. This provides a proof of the existence of the
new class of MC techniques, to be exploited in the precision perturbative QCD
calculations for the Large Hadron Collider
Constrained non-Markovian Monte Carlo modelling of the evolution equation in QCD
A new class of the constrained Monte Carlo (CMC) algorithms for the QCD
evolution equation was recently discovered. The constraint is imposed on the
type and the total longitudinal energy of the parton exiting QCD evolution and
entering a hard process. The efficiency of the new CMCs is found to be
reasonable.Comment: Contribution to HERA-LHC worksho
How to Generate Four-Fermion Phase Space
We present a scheme for integrating the matrix element of an arbitrary
e^+e^-\to f_1f_2\bar f_3\bar f_4 process over the complete four-fermion phase
space, or its any part, by means of the Monte Carlo technique. The presented
algorithm has been successfully implemented in the KORALW Monte Carlo code.Comment: 16 page
Solving constrained Markovian evolution in QCD with the help of the non-Markovian Monte Carlo
We present the constrained Monte Carlo (CMC) algorithm for the QCD evolution.
The constraint resides in that the total longitudinal energy of the emissions
in the MC and in the underlying QCD evolution is predefined (constrained). This
CMC implements exactly the full DGLAP evolution of the parton distributions in
the hadron with respect to the logarithm of the energy scale. The algorithm of
the CMC is referred to as the non-Markovian type. The non-Markovian MC
algorithm is defined as the one in which the multiplicity of emissions is
chosen randomly as the first variable and not the last one, as in the Markovian
MC algorithms. The former case resembles that of the fixed-order matrix element
calculations. The CMC algorithm can serve as an alternative to the so-called
backward evolution Markovian algorithm of Sjostrand, which is used for
modelling the initial-state parton shower in modern QCD MC event generators. We
test practical feasibility and efficiency of our CMC implementation in a series
of numerical exercises, comparing its results with those from other MC and
non-MC programs, in a wide range of Q and x, down to the 0.1% precision level.
In particular, satisfactory numerical agreement is found with the results of
the Markovian MC program of our own and the other non-MC program. The
efficiency of the new constrained MC is found to be quite good
Conditions and methods of intellectual capital measurement
Rozpatrywano cechy wyceny firmy. Uzasadniano konieczność pomiaru kapitału intelektualnego w skali makroekonomicznej. Przedstawiono proces pomiaru kapitału intelektualnego na poziomie organizacji. Sprawdzone korzyści z pomiaru kapitału intelektualnego. Udowodniono zależność produktywności kapitału intelektualnego od efektywności zastosowania wiedzy. Przeanalizowane narzędzie weryfikujące silne i słabe strony w drodze prowadzącej do tworzenia gospodarki opartej na wiedzę. Udowodniono, że pomiar kapitału intelektualnego jest kluczowym elementem procesu zarządzania kapitałem intelektualnym. Sprawdzone, że kapitał intelektualny jest źródłem przewagi konkurencyjnej.Characteristics of the company evaluation are considered. The necessity of measuring intellectual capital at the macroeconomic level is justified. The process of measuring intellectual capital at the level of an organization is presented in the article. Advantages of measuring intellectual capital are proved. The intellectual capital productivity dependence on the efficiency of knowledge use is proved. A tool for testing the strengths and weaknesses of the way resulting in the creation of a knowledge economy is considered. It is proved that the measurement of intellectual capital is a key element in the management of intellectual capital. It is verified that intellectual capital is a source of competitive advantage
- …