539 research outputs found
Isospin Fluctuations from a Thermally Equilibrated Hadron Gas
Partition functions, multiplicity distributions, and isospin fluctuations are
calculated for canonical ensembles in which additive quantum numbers as well as
total isospin are strictly conserved. When properly accounting for
Bose-Einstein symmetrization, the multiplicity distributions of neutral pions
in a pion gas are significantly broader as compared to the non-degenerate case.
Inclusion of resonances compensates for this broadening effect. Recursion
relations are derived which allow calculation of exact results with modest
computer time.Comment: 10 pages, 5 figure
Binary data corruption due to a Brownian agent
We introduce a model of binary data corruption induced by a Brownian agent
(active random walker) on a d-dimensional lattice. A continuum formulation
allows the exact calculation of several quantities related to the density of
corrupted bits \rho; for example the mean of \rho, and the density-density
correlation function. Excellent agreement is found with the results from
numerical simulations. We also calculate the probability distribution of \rho
in d=1, which is found to be log-normal, indicating that the system is governed
by extreme fluctuations.Comment: 39 pages, 10 figures, RevTe
Atom capture by nanotube and scaling anomaly
The existence of bound state of the polarizable neutral atom in the inverse
square potential created by the electric field of single walled charged carbon
nanotube (SWNT) is shown to be theoretically possible. The consideration of
inequivalent boundary conditions due to self-adjoint extensions lead to this
nontrivial bound state solution. It is also shown that the scaling anomaly is
responsible for the existence of bound state. Binding of the polarizable atoms
in the coupling constant interval \eta^2\in[0,1) may be responsible for the
smearing of the edge of steps in quantized conductance, which has not been
considered so far in literature.Comment: Accepted in Int.J.Theor.Phy
Additional phases induced by the supersymmetric CP phases
The explicit CP violation in the MSSM radiatively induces a finite
unremovable alignment between the Higgs doublets. This additinal phase can be
as large as the original CP phases in certain portions of the MSSM parameter
space. Considering the specific case of the charginos, this additional phase is
shown to induce a conceivable amount of CP violation near the would--be CP
conserving points. Moreover, the CP violation in the absence of this phase is
smaller than the one in the presence of it, and the former can never compete
with the latter, however large is.Comment: 29 pp, 15 fig
Effects of the supersymmetric phases on the neutral Higgs sector
By using the effective potential approximation and taking into account the
dominant top quark and scalar top quark loops, radiative corrections to MSSM
Higgs potential are computed in the presence of the supersymmetric CP-violating
phases. It is found that, the lightest Higgs scalar remains essentially CP-even
as in the CP-invariant theory whereas the other two scalars are heavy and do
not have definite CP properties. The supersymmetric CP-violating phases are
shown to modify significantly the decay rates of the scalars to fermion pairs.Comment: 24 pp, 8 figs, 2 tables, typos and errors correcte
A Detailed Study of the Gluino Decay into the Third Generation Squarks at the CERN LHC
In supersymmetric models a gluino can decay into tb\tilde{\chi}^{\pm}_1
through a stop or a sbottom. The decay chain produces an edge structure in the
m_{tb} distribution. Monte Carlo simulation studies show that the end point and
the edge height would be measured at the CERN LHC by using a sideband
subtraction technique. The stop and sbottom masses as well as their decay
branching ratios are constrained by the measurement. We study interpretations
of the measurement in the minimal supergravity model. We also study the gluino
decay into tb and \tilde{\chi}^{\pm}_2 as well as the influence of the stop
left-right mixing on the m_{bb} distribution of the tagged events.Comment: revtex, 20 pages in PRD format, 35 eps file
On the Spontaneous CP Breaking at Finite Temperature in a Nonminimal Supersymmetric Standard Model
We study the spontaneous CP breaking at finite temperature in the Higgs
sector in the Minimal Supersymmetric Standard Model with a gauge singlet. We
consider the contribution of the standard model particles and that of stops,
charginos, neutralinos, charged and neutral Higgs boson to the one-loop
effective potential. Plasma effects for all bosons are also included. Assuming
CP conservation at zero temperature, so that experimental constraints coming
from, {\it e.g.}, the electric dipole moment of the neutron are avoided, and
the electroweak phase transition to be of the first order and proceeding via
bubble nucleation, we show that spontaneous CP breaking cannot occur inside the
bubble mainly due to large effects coming from the Higgs sector. However,
spontaneous CP breaking can be present in the region of interest for the
generation of the baryon asymmetry, namely inside the bubble wall. The
important presence of very tiny explicit CP violating phases is also commented.Comment: 28 pages, 4 figures available upon request, DFPD 94/TH/38 and SISSA
94/81-A preprint
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Transpacific Transport of Ozone Pollution and the Effect of Recent Asian Emission Increases on Air Quality in North America: An Integrated Analysis Using Satellite, Aircraft, Ozonesonde, and Surface Observations
We use an ensemble of aircraft, satellite, sonde, and surface observations for April–May 2006 (NASA/INTEX-B aircraft campaign) to better understand the mechanisms for transpacific ozone pollution and its implications for North American air quality. The observations are interpreted with a global 3-D chemical transport model (GEOS-Chem). OMI NO2 satellite observations constrain Asian anthropogenic NOx emissions and indicate a factor of 2 increase from 2000 to 2006 in China. Satellite observations of CO from AIRS and TES indicate two major events of Asian transpacific pollution during INTEX-B. Correlation between TES CO and ozone observations shows evidence for transpacific ozone pollution. The semi-permanent Pacific High and Aleutian Low cause splitting of transpacific pollution plumes over the Northeast Pacific. The northern branch circulates around the Aleutian Low and has little impact on North America. The southern branch circulates around the Pacific High and some of that air impacts western North America. Both aircraft measurements and model results show sustained ozone production driven by peroxyacetylnitrate (PAN) decomposition in the southern branch, roughly doubling the transpacific influence from ozone produced in the Asian boundary layer. Model simulation of ozone observations at Mt. Bachelor Observatory in Oregon (2.7 km altitude) indicates a mean Asian ozone pollution contribution of 9±3 ppbv to the mean observed concentration of 54 ppbv, reflecting mostly an enhancement in background ozone rather than episodic Asian plumes. Asian pollution enhanced surface ozone concentrations by 5–7 ppbv over western North America in spring 2006. The 2000–2006 rise in Asian anthropogenic emissions increased this influence by 1–2 ppbv.Earth and Planetary SciencesEngineering and Applied Science
Dark Matter, Light Stops and Electroweak Baryogenesis
We examine the neutralino relic density in the presence of a light top
squark, such as the one required for the realization of the electroweak
baryogenesis mechanism, within the minimal supersymmetric standard model. We
show that there are three clearly distinguishable regions of parameter space,
where the relic density is consistent with WMAP and other cosmological data.
These regions are characterized by annihilation cross sections mediated by
either light Higgs bosons, Z bosons, or by the co-annihilation with the
lightest stop. Tevatron collider experiments can test the presence of the light
stop in most of the parameter space. In the co-annihilation region, however,
the mass difference between the light stop and the lightest neutralino varies
between 15 and 30 GeV, presenting an interesting challenge for stop searches at
hadron colliders. We present the prospects for direct detection of dark matter,
which provides a complementary way of testing this scenario. We also derive the
required structure of the high energy soft supersymmetry breaking mass
parameters where the neutralino is a dark matter candidate and the stop
spectrum is consistent with electroweak baryogenesis and the present bounds on
the lightest Higgs mass.Comment: 24 pages, 8 figures; version published in Phys.Rev.
Counting children with tuberculosis: why numbers matter.
In the last 5 years, childhood tuberculosis (TB) has received increasing attention from international organisations, national TB programmes and academics. For the first time, a number of different groups are developing techniques to estimate the burden of childhood TB. We review the challenges in diagnosing TB in children and the reasons why cases in children can go unreported. We discuss the importance of an accurate understanding of burden for identifying problems in programme delivery, targeting interventions, monitoring trends, setting targets, allocating resources appropriately and providing strong advocacy. We briefly review the estimates produced by new analytical methods, and outline the reasons for recent improvements in our understanding and potential future directions. We conclude that while innovation, collaboration and better data have improved our understanding of the childhood TB burden, it remains substantially incomplete
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