1,251 research outputs found
The study of the extended Higgs boson sector within 2HDM model
Consideration of the latest experimental data on the searches for extended
sector of Higgs bosons produced at the LHC at a center-of-mass energy of 13
TeV, allows for computer modeling of the properties of supersymmetric particles
within 2HDM model. The experimental restrictions on model parameters accounted
in FeynHiggs code that is implemented in SusHi program, gave us the possibility
to calculate the cross sections and branching fractions for three mechanisms of
production and decay of Higgs bosons: 1) pp,
2) pp, 3) pp at a center-of-mass energy of 14 TeV.
The considered computer modelling make it possible to draw conclusions about
the need to take into account the b-associated production process of Higgs
bosons for fermionic decay channel at large values of tan. Differential
cross sections with respect to the Higgs transverse momentum and
pseudorapidity are calculated and the peculiarities of the kinematics of
the Higgs boson decay products are recognized.Comment: 18 pages, 14 figures, presented at XV Conference of High energy
physics, Kharkov, 21-24 March, 201
The Two-Screen Measurement Setup to Indirectly Measure Proton Beam Self-Modulation in AWAKE
The goal of the first phase of the AWAKE \cite{AWAKE1,AWAKE2} experiment at
CERN is to measure the self-modulation \cite{SMI} of the long SPS proton bunch into microbunches after traversing
of plasma with a plasma density of
. The two screen measurement setup
\cite{Turner2016} is a proton beam diagnostic that can indirectly prove the
successful development of the self-modulation of the proton beam by imaging
protons that got defocused by the transverse plasma wakefields after passing
through the plasma, at two locations downstream the end of the plasma. This
article describes the design and realization of the two screen measurement
setup integrated in the AWAKE experiment. We discuss the performance and
background response of the system based on measurements performed with an
unmodulated Gaussian SPS proton bunch during the AWAKE beam commissioning in
September and October 2016. We show that the system is fully commissioned and
adapted to eventually image the full profile of a self-modulated SPS proton
bunch in a single shot measurement during the first phase of the AWAKE
experiment.Comment: 5 pages 8 figure
Field-Driven Transitions in the Dipolar Pyrochlore Antiferromagnet GdTiO
We present a mean-field theory for magnetic field driven transitions in
dipolar coupled gadolinium titanate GdTiO pyrochlore system. Low
temperature neutron scattering yields a phase that can be regarded as a 8
sublattice antiferromagnet, in which long-ranged ordered moments and
fluctuating moments coexist. Our theory gives parameter regions where such a
phase is realized, and predicts several other phases, with transitions amongst
them driven by magnetic field as well as temperature. We find several instances
of {\em local} disorder parameters describing the transitions.Comment: 4 pages, 5 figures. v2: longer version with 2 add.fig., to appear in
PR
Indirect Self-Modulation Instability Measurement Concept for the AWAKE Proton Beam
AWAKE, the Advanced Proton-Driven Plasma Wakefield Acceleration Experiment,
is a proof-of-principle R&D experiment at CERN using a 400 GeV/c proton beam
from the CERN SPS (longitudinal beam size sigma_z = 12 cm) which will be sent
into a 10 m long plasma section with a nominal density of approx. 7x10^14
atoms/cm3 (plasma wavelength lambda_p = 1.2mm). In this paper we show that by
measuring the time integrated transverse profile of the proton bunch at two
locations downstream of the AWAKE plasma, information about the occurrence of
the self-modulation instability (SMI) can be inferred. In particular we show
that measuring defocused protons with an angle of 1 mrad corresponds to having
electric fields in the order of GV/m and fully developed self-modulation of the
proton bunch. Additionally, by measuring the defocused beam edge of the
self-modulated bunch, information about the growth rate of the instability can
be extracted. If hosing instability occurs, it could be detected by measuring a
non-uniform defocused beam shape with changing radius. Using a 1 mm thick
Chromox scintillation screen for imaging of the self-modulated proton bunch, an
edge resolution of 0.6 mm and hence a SMI saturation point resolution of 1.2 m
can be achieved.Comment: 4 pages, 4 figures, EAAC conference proceeding
Extreme 13C depletion of CCl2F2 in firn air samples from NEEM, Greenland
A series of 12 high volume air samples collected from the S2 firn core during the North Greenland Eemian Ice Drilling (NEEM) 2009 campaign have been measured for mixing ratio and stable carbon isotope composition of the chlorofluorocarbon CFC-12 (CCl2F2). While the mixing ratio measurements compare favorably to other firn air studies, the isotope results show extreme 13C depletion at the deepest measurable depth (65 m), to values lower than d13C = -80‰ vs. VPDB (the international stable carbon isotope scale), compared to present day surface tropospheric measurements near -40‰. Firn air modeling was used to interpret these measurements. Reconstructed atmospheric time series indicate even larger depletions (to -120‰) near 1950 AD, with subsequent rapid enrichment of the atmospheric reservoir of the compound to the present day value. Mass-balance calculations show that this change is likely to have been caused by a large change in the isotopic composition of anthropogenic CFC-12 emissions, probably due to technological advances in the CFC production process over the last 80 yr, though direct evidence is lacking
Vibration resistance, vibration testing, vibration monitoring and diagnostics of gyroscopes and other rotary systems
This article is devoted to the presentation in a historical development of the results achieved, founded by M.A. Pavlovsky scientific directions related to the
study of vibration processes in rotary systemsДана стаття присвячена викладенню в історичному розвитку досягнутих
результатів, започаткованих М.А.Павловським наукового напряму,
пов’язаного з вивченням коливальних процесів в обертових системах
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