20,411 research outputs found
The tauola-photos_F environment for versioning the TAUOLA and PHOTOS packages
We present the system for versioning two packages: the TAUOLA of tau lepton
decay and PHOTOS for radiative corrections in decays. The following features
can be chosen in automatic or semi-automatic way: (1) format of the common
block HEPEVT; (2) version of the physics input (for TAUOLA): as published, as
initialized by CLEO collaboration, as initialized by ALEPH collaboration (it is
suggested to use this version only with the help of the collaboration advice);
(3) type of application: stand-alone, universal interface through HEPEVT,
interface for KKMC Monte Carlo; (4) random number generators; (5) compiler
options.Comment: nine pages, late
Next Generation Higgs Bosons: Theory, Constraints and Discovery Prospects at the Large Hadron Collider
Particle physics model building within the context of string theory suggests
that further copies of the Higgs boson sector may be expected. Concerns
regarding tree-level flavor changing neutral currents are easiest to allay if
little or no couplings of next generation Higgs bosons are allowed to Standard
Model fermions. We detail the resulting general Higgs potential and mass
spectroscopy in both a Standard Model extension and a supersymmetric extension.
We present the important experimental constraints from meson-meson mixing,
loop-induced decays and LEP2 direct production limits. We
investigate the energy range of valid perturbation theory of these ideas. In
the supersymmetric context we present a class of examples that marginally aids
the fine-tuning problem for parameter space where the lightest Higgs boson mass
is greater than the Standard Model limit of 114 GeV. Finally, we study collider
physics signatures generic to next generation Higgs bosons, with special
emphasis on signal events, and describe the capability of
discovery at the Large Hadron Collider.Comment: 43 pages, 12 figures; v3: minor corrections, published in Physical
Review
Prospects for Observing an Invisibly Decaying Higgs Boson in the t anti-t H Production at the LHC
The prospects for observing an invisibly decaying Higgs boson in the t anti-t
H production at LHC are discussed. An isolated lepton, reconstructed hadronic
top-quark decay, two identified b-jets and large missing transverse energy are
proposed as the final state signature for event selection. Only the Standard
Model backgrounds are taken into account. It is shown that the t anti-t Z, t
anti-t W, b anti-b Z and b anti-b W backgrounds can individually be suppressed
below the signal expectation. The dominant source of background remains the t
anti-t production. The key for observability will be an experimental selection
which allows further suppression of the contributions from the t anti-t events
with one of the top-quarks decaying into a tau lepton. Depending on the details
of the final analysis, an excess of the signal events above the Standard Model
background of about 10% to 100% can be achieved in the mass range m_H= 100-200
GeV.Comment: Final version as accepted by EPJ
Implementation of liquid culture for tuberculosis diagnosis in a remote setting: lessons learned.
Although sputum smear microscopy is the primary method for tuberculosis (TB) diagnosis in low-resource settings, it has low sensitivity. The World Health Organization recommends the use of liquid culture techniques for TB diagnosis and drug susceptibility testing in low- and middle-income countries. An evaluation of samples from southern Sudan found that culture was able to detect cases of active pulmonary TB and extra-pulmonary TB missed by conventional smear microscopy. However, the long delays involved in obtaining culture results meant that they were usually not clinically useful, and high rates of non-tuberculous mycobacteria isolation made interpretation of results difficult. Improvements in diagnostic capacity and rapid speciation facilities, either on-site or through a local reference laboratory, are crucial
Linear independence of localized magnon states
At the magnetic saturation field, certain frustrated lattices have a class of
states known as "localized multi-magnon states" as exact ground states. The
number of these states scales exponentially with the number of spins and
hence they have a finite entropy also in the thermodynamic limit
provided they are sufficiently linearly independent. In this article we present
rigorous results concerning the linear dependence or independence of localized
magnon states and investigate special examples. For large classes of spin
lattices including what we called the orthogonal type and the isolated type as
well as the kagom\'{e}, the checkerboard and the star lattice we have proven
linear independence of all localized multi-magnon states. On the other hand the
pyrochlore lattice provides an example of a spin lattice having localized
multi-magnon states with considerable linear dependence.Comment: 23 pages, 6 figure
Machine learning classification: case of Higgs boson CP state in H to tau tau decay at LHC
Machine Learning (ML) techniques are rapidly finding a place among the
methods of High Energy Physics data analysis. Different approaches are explored
concerning how much effort should be put into building high-level variables
based on physics insight into the problem, and when it is enough to rely on
low-level ones, allowing ML methods to find patterns without explicit physics
model.
In this paper we continue the discussion of previous publications on the CP
state of the Higgs boson measurement of the H to tau tau decay channel with the
consecutive tau^pm to rho^pm nu; rho^pm to pi^pm pi^0 and tau^pm to a_1^pm nu;
a_1^pm to rho^0 pi^pm to 3 pi^pm cascade decays. The discrimination of the
Higgs boson CP state is studied as a binary classification problem between
CP-even (scalar) and CP-odd (pseudoscalar), using Deep Neural Network (DNN).
Improvements on the classification from the constraints on directly
non-measurable outgoing neutrinos are discussed. We find, that once added, they
enhance the sensitivity sizably, even if only imperfect information is
provided. In addition to DNN we also evaluate and compare other ML methods:
Boosted Trees (BT), Random Forest (RF) and Support Vector Machine (SVN).Comment: 1+20 pages, 9 figures, 6 tables, extended content and improved
readabilit
Localized-magnon states in strongly frustrated quantum spin lattices
Recent developments concerning localized-magnon eigenstates in strongly
frustrated spin lattices and their effect on the low-temperature physics of
these systems in high magnetic fields are reviewed. After illustrating the
construction and the properties of localized-magnon states we describe the
plateau and the jump in the magnetization process caused by these states.
Considering appropriate lattice deformations fitting to the localized magnons
we discuss a spin-Peierls instability in high magnetic fields related to these
states. Last but not least we consider the degeneracy of the localized-magnon
eigenstates and the related thermodynamics in high magnetic fields. In
particular, we discuss the low-temperature maximum in the isothermal entropy
versus field curve and the resulting enhanced magnetocaloric effect, which
allows efficient magnetic cooling from quite large temperatures down to very
low ones.Comment: 21 pages, 10 figures, invited paper for a special issue of "Low
Temperature Physics " dedicated to the 70-th anniversary of creation of
concept "antiferromagnetism" in physics of magnetis
Frustrated Heisenberg antiferromagnet on the honeycomb lattice: Spin gap and low-energy parameters
We use the coupled cluster method implemented to high orders of approximation
to investigate the frustrated spin- ----
antiferromagnet on the honeycomb lattice with isotropic Heisenberg interactions
of strength between nearest-neighbor pairs, between
next-nearest-neighbor pairs, and between next-next-neareast-neighbor
pairs of spins. In particular, we study both the ground-state (GS) and
lowest-lying triplet excited-state properties in the case , in the window of the frustration
parameter, which includes the (tricritical) point of maximum classical
frustration at . We present GS results for the
spin stiffness, , and the zero-field uniform magnetic susceptibility,
, which complement our earlier results for the GS energy per spin, ,
and staggered magnetization, , to yield a complete set of accurate
low-energy parameters for the model. Our results all point towards a phase
diagram containing two quasiclassical antiferromagnetic phases, one with N\'eel
order for , and the other with collinear striped order
for . The results for both and the spin gap
provide compelling evidence for a quantum paramagnetic phase that is
gapped over a considerable portion of the intermediate region , especially close to the two quantum critical points
at and . Each of our fully independent sets of
results for the low-energy parameters is consistent with the values
and , and with
the transition at being of continuous (and probably of the
deconfined) type and that at being of first-order type
A solvable model of a random spin-1/2 XY chain
The paper presents exact calculations of thermodynamic quantities for the
spin-1/2 isotropic XY chain with random lorentzian intersite interaction and
transverse field that depends linearly on the surrounding intersite
interactions.Comment: 14 pages (Latex), 2 tables, 13 ps-figures included, (accepted for
publication in Phys.Rev.B
О влиянии свойств инструментального материала на усадку стружки при резании сталей
The exploitation of solar power for energy supply is of increasing importance. While technical development mainly takes place in the engineering disciplines, computer science offers adequate techniques for simulation, optimisation and controller synthesis. In this paper we describe a work from this interdisciplinary area. We introduce our tool for the optimisation of parameterised solar thermal power plants, and report on the employment of genetic algorithms and neural networks for parameter synthesis. Experimental results show the applicability of our approach
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