624 research outputs found
Neutral Plasma Oscillations at Zero Temperature
We use cold plasma theory to calculate the response of an ultracold neutral
plasma to an applied rf field. The free oscillation of the system has a
continuous spectrum and an associated damped quasimode. We show that this
quasimode dominates the driven response. We use this model to simulate plasma
oscillations in an expanding ultracold neutral plasma, providing insights into
the assumptions used to interpret experimental data [Phys. Rev. Lett. 85, 318
(2000)].Comment: 4.3 pages, including 3 figure
Superposition effect and clan structure in forward-backward multiplicity correlations
The main purpose of this paper is to discuss the link between
forward-backward multiplicity correlations properties and the shape of the
corresponding final charged particle multiplicity distribution in various
classes of events in different collisions. It is shown that the same mechanism
which explains the shoulder effect and the H_n vs. n oscillations in charged
particle multiplicity distributions, i.e., the weighted superposition of
different classes of events with negative binomial properties, reproduces
within experimental errors also the forward-backward multiplicity correlation
strength in e+e- annihilation at LEP energy and allows interesting predictions
for pp collisions in the TeV energy region, to be tested at LHC, for instance
with the ALICE detector. We limit ourselves at present to study substructures
properties in hadron-hadron collisions and e+e- annihilation; they are examined
as ancillary examples in the conviction that their understanding might be
relevant also in other more complex cases.Comment: 16 page
Higgs Boson Flavor-Changing Neutral Decays into Bottom Quarks in Supersymmetry
We analyze the maximum branching ratios for the Flavor Changing Neutral
Current (FCNC) decays of the neutral Higgs bosons of the Minimal Supersymmetric
Standard Model (MSSM) into bottom quarks, h -> b\bar{s} (h=h^0,H^0,A^0). We
consistently correlate these decays with the radiative B-meson decays (b->
s\gamma). A full-fledged combined numerical analysis is performed of these
high-energy and low-energy FCNC decay modes in the MSSM parameter space. Our
calculation shows that the available data on B(b->s \gamma) severely restricts
the allowed values of B(h->b\bar{s}). While the latter could reach a few
percent level in fine-tuned scenarios, the requirement of naturalness reduces
these FCNC rates into the modest range B(h->b\bar{s}) ~ 10^{-4}-10^{-3}. We
find that the bulk of the MSSM contribution to B(h->b\bar{s}) could originate
from the strong supersymmetric sector. The maximum value of the FCNC rates
obtained in this paper disagree significantly with recent (over-)estimates
existing in the literature. Our results are still encouraging because they show
that the FCNC modes h->b\bar{s} can be competitive with other Higgs boson
signatures and could play a helpful complementary role to identify the
supersymmetric Higgs bosons, particularly the lightest CP-even state in the
critical LHC mass region m_{h^0} ~= 90-130 GeV.Comment: LaTeX, 19 pages, 4 tables, 7 figures. Clarifications and discussions
added, references added. Slight changes in Figs2b,6b and 7b. Version accepted
in JHE
Electroweak Radiative Corrections to Associated WH and ZH Production at Hadron Colliders
Higgs-boson production in association with W or Z bosons, p pbar -> WH/ZH +
X, is the most promising discovery channel for a light Standard Model Higgs
particle at the Fermilab Tevatron. We present the calculation of the
electroweak O(alpha) corrections to these processes. The corrections decrease
the theoretical prediction by up to 5-10%, depending in detail on the
Higgs-boson mass and the input-parameter scheme. We update the cross-section
prediction for associated WH and ZH production at the Tevatron and at the LHC,
including the next-to-leading order electroweak and QCD corrections, and study
the theoretical uncertainties induced by factorization and renormalization
scale dependences and by the parton distribution functions.Comment: 32 pages, LaTeX, 21 figures. Uses axodraw.sty and feynarts.sty. Added
reference
Introductory clifford analysis
In this chapter an introduction is given to Clifford analysis and the underlying Clifford algebras. The functions under consideration are defined on Euclidean space and take values in the universal real or complex Clifford algebra, the structure and properties of which are also recalled in detail. The function theory is centered around the notion of a monogenic function, which is a null solution of a generalized CauchyâRiemann operator, which is rotation invariant and factorizes the Laplace operator. In this way, Clifford analysis may be considered as both a generalization to higher dimension of the theory of holomorphic functions in the complex plane and a refinement of classical harmonic analysis. A notion of monogenicity may also be associated with the vectorial part of the CauchyâRiemann operator, which is called the Dirac operator; some attention is paid to the intimate relation between both notions. Since a product of monogenic functions is, in general, no longer monogenic, it is crucial to possess some tools for generating monogenic functions: such tools are provided by Fueterâs theorem on one hand and the CauchyâKovalevskaya extension theorem on the other hand. A corner stone in this function theory is the Cauchy integral formula for representation of a monogenic function in the interior of its domain of monogenicity. Starting from this representation formula and related integral formulae, it is possible to consider integral transforms such as Cauchy, Hilbert, and Radon transforms, which are important both within the theoretical framework and in view of possible applications
Precise predictions for the Higgs production in association with a W-boson pair at ILC
The Higgs-boson production in association with a W-boson pair at
linear colliders is one of the important processes in probing the coupling
between Higgs-boson and vector gauge bosons and discovering the signature of
new physics. We describe the impact of the complete electroweak(EW) radiative
corrections of to this process in the standard
model(SM) at the International Linear Collider(ILC), and investigate the
dependence of the lowest-order(LO) and EW next-to-leading order(NLO) corrected
cross sections on colliding energy and Higg-boson mass. The LO and
NLO EW corrected distributions of the invariant mass of W-boson pair and the
transverse momenta of final - and Higgs-boson are presented. Our numerical
results show that the relative EW radiative correction() varies
from -19.4% to 0.2% when and goes up from to
.Comment: 18 pages, 7 figure
GATA2 deficiency syndrome: a decade of discovery
Accepted: 8 August 2021GATA2 deficiency syndrome (G2DS) is a rare autosomal dominant genetic disease predisposing to a range of symptoms of which myeloid malignancy and immunodeficiency including recurrent infections are most common. In the last decade since it was first reported, there have been over 480 individuals identified carrying a pathogenic or likely pathogenic germline GATA2 variant with symptoms of G2DS, with 240 of these confirmed to be familial and 24 de novo. For those that develop myeloid malignancy (75% of all carriers with G2DS disease symptoms), the median age of onset is 17 years (range 0-78 years) and myelodysplastic syndrome (MDS) is the first diagnosis in 75% of these cases with acute myeloid leukemia (AML) in a further 9%. All variant types appear to predispose to myeloid malignancy and immunodeficiency. Apart from lymphedema in which haploinsufficiency seems necessary, the mutational requirements of the other less common G2DS phenotypes is still unclear. These predominantly loss-of-function variants impact GATA2 expression and function in numerous ways including perturbations to DNA binding, protein structure, protein:protein interactions, and gene transcription, splicing and expression. In this review, we provide the first expert-curated ACMG/AMP classification with codes of published variants compatible for use in clinical or diagnostic settings. This article is protected by copyright. All rights reserved.Claire C. Homan, Parvathy Venugopal, Peer Arts, Nur H. Shahrin, Simone Feurstein, Lesley Rawlings, David M. Lawrence, James Andrews, Sarah L. King, Smith, Natasha L. Harvey, Anna L. Brown, Hamish S. Scott, Christopher N. Hah
Origins of the Ambient Solar Wind: Implications for Space Weather
The Sun's outer atmosphere is heated to temperatures of millions of degrees,
and solar plasma flows out into interplanetary space at supersonic speeds. This
paper reviews our current understanding of these interrelated problems: coronal
heating and the acceleration of the ambient solar wind. We also discuss where
the community stands in its ability to forecast how variations in the solar
wind (i.e., fast and slow wind streams) impact the Earth. Although the last few
decades have seen significant progress in observations and modeling, we still
do not have a complete understanding of the relevant physical processes, nor do
we have a quantitatively precise census of which coronal structures contribute
to specific types of solar wind. Fast streams are known to be connected to the
central regions of large coronal holes. Slow streams, however, appear to come
from a wide range of sources, including streamers, pseudostreamers, coronal
loops, active regions, and coronal hole boundaries. Complicating our
understanding even more is the fact that processes such as turbulence,
stream-stream interactions, and Coulomb collisions can make it difficult to
unambiguously map a parcel measured at 1 AU back down to its coronal source. We
also review recent progress -- in theoretical modeling, observational data
analysis, and forecasting techniques that sit at the interface between data and
theory -- that gives us hope that the above problems are indeed solvable.Comment: Accepted for publication in Space Science Reviews. Special issue
connected with a 2016 ISSI workshop on "The Scientific Foundations of Space
Weather." 44 pages, 9 figure
Evidence of Color Coherence Effects in W+jets Events from ppbar Collisions at sqrt(s) = 1.8 TeV
We report the results of a study of color coherence effects in ppbar
collisions based on data collected by the D0 detector during the 1994-1995 run
of the Fermilab Tevatron Collider, at a center of mass energy sqrt(s) = 1.8
TeV. Initial-to-final state color interference effects are studied by examining
particle distribution patterns in events with a W boson and at least one jet.
The data are compared to Monte Carlo simulations with different color coherence
implementations and to an analytic modified-leading-logarithm perturbative
calculation based on the local parton-hadron duality hypothesis.Comment: 13 pages, 6 figures. Submitted to Physics Letters
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