3,035 research outputs found
Atmospheric Chemistry for Astrophysicists: A Self-consistent Formalism and Analytical Solutions for Arbitrary C/O
We present a self-consistent formalism for computing and understanding the
atmospheric chemistry of exoplanets from the viewpoint of an astrophysicist.
Starting from the first law of thermodynamics, we demonstrate that the van't
Hoff equation (which describes the equilibrium constant), Arrhenius equation
(which describes the rate coefficients) and procedures associated with the
Gibbs free energy (minimisation, rescaling) have a common physical and
mathematical origin. We address an ambiguity associated with the equilibrium
constant, which is used to relate the forward and reverse rate coefficients,
and restate its two definitions. By necessity, one of the equilibrium constants
must be dimensionless and equate to an exponential function involving the Gibbs
free energy, while the other is a ratio of rate coefficients and must therefore
possess physical units. We demonstrate that the Arrhenius equation takes on a
functional form that is more general than previously stated without recourse to
tagging on ad hoc functional forms. Finally, we derive analytical models of
chemical systems, in equilibrium, with carbon, hydrogen and oxygen. We include
acetylene and are able to reproduce several key trends, versus temperature and
carbon-to-oxygen ratio, published in the literature. The rich variety of
behavior that mixing ratios exhibit as a function of the carbon-to-oxygen ratio
is merely the outcome of stoichiometric book-keeping and not the direct
consequence of temperature or pressure variations.Comment: Accepted by ApJ. 9 pages, 4 figure
Explanation of the ATLAS Z-peaked excess by squark pair production in the NMSSM
The ATLAS collaboration recently reported a excess in the
leptonic- channel. We intend to interpret this excess by
squark pair production in the Next-to-Minimal Supersymmetric Standard Model
(NMSSM). The decay chain we employ is , where and denote the
lightest and the next-to-lightest neutralinos with singlino and bino as their
dominant components respectively. Our simulations indicate that after
considering the constraints from the ATLAS searches for
signal the central value of the excess can be obtained for , and if the constraint from the CMS on- search is
further considered, more than 10 signal events are still attainable for
. Compared with the interpretation by
gluino pair production, the squark explanation allows for a significantly wider
range of as well as a less compressed SUSY mass spectrum. We
also show that the squark explanation will be readily tested at the initial
stage of the 14 TeV LHC.Comment: 19 pages, 4 figure
Explanation of the ATLAS Z-peaked excess in the NMSSM
Recently the ATLAS collaboration reported a excess in the
leptonic- channel. This may be interpreted in the
Next-to-Minimal Supersymmetric Standard Model (NMSSM) by gluino pair production
with the decay chain , where and denote the
lightest and the next-to-lightest neutralinos with singlino and bino as their
dominant components respectively. After exploring the relevant parameter space
of the NMSSM by considering the constraints from the ATLAS searches for signals, we conclude that the NMSSM is able to explain the excess
at level with the number of the signal events reaching its measured
central value in optimal cases, and the best explanation comes from a
compressed spectrum such as ,
and . We also check the consistency of the ATLAS results with the
null result of the CMS on- search. We find that under the CMS limits at
C.L., the event number of the ATLAS on- signal can still reach 11 in
our scenario, which is about away from the measured central value.Comment: 18 pages, 2 figure
Interpreting the galactic center gamma-ray excess in the NMSSM
In the Next-to-Minimal Supersymmetric Standard Model (NMSSM), all
singlet-dominated particles including one neutralino, one CP-odd Higgs boson
and one CP-even Higgs boson can be simultaneously lighter than about 100 GeV.
Consequently, dark matter (DM) in the NMSSM can annihilate into multiple final
states to explain the galactic center gamma-ray excess (GCE). In this work we
take into account the foreground and background uncertainties for the GCE and
investigate these explanations. We carry out a sophisticated scan over the
NMSSM parameter space by considering various experimental constraints such as
the Higgs data, -physics observables, DM relic desnity, LUX experiment and
the dSphs constraints. Then for each surviving parameter point we perform a fit
to the GCE spectrum by using the correlation matrix that incorporates both the
statistical and systematic uncertainties of the measured excess. After
examining the properties of the obtained GCE solutions, we conclude that the
GCE can be well explained by the pure annihilations and with being the lighter singlet-dominated CP-odd Higgs boson and
denoting the singlet-dominated CP-even Higgs boson or SM-like Higgs
boson, and it can also be explained by the mixed annihilation . Among these annihilation channels,
can provide the best
interpretation with the corresponding -value reaching 0.55. We also discuss
to what extent the future DM direct detection experiments can explore the GCE
solutions and conclude that the XENON-1T experiment is very promising in
testing nearly all the solutions.Comment: 31 pages, 7 figure
Pair Production of a 125 GeV Higgs Boson in MSSM and NMSSM at the LHC
In light of the recent LHC Higgs search data, we investigate the pair
production of a SM-like Higgs boson around 125 GeV in the MSSM and NMSSM. We
first scan the parameter space of each model by considering various
experimental constraints, and then calculate the Higgs pair production rate in
the allowed parameter space. We find that in most cases the dominant
contribution to the Higgs pair production comes from the gluon fusion process
and the production rate can be greatly enhanced, maximally 10 times larger than
the SM prediction (even for a TeV-scale stop the production rate can still be
enhanced by a factor of 1.3). We also calculate the chi-square value with the
current Higgs data and find that in the most favored parameter region the
production rate is enhanced by a factor of 1.45 in the MSSM, while in the NMSSM
the production rate can be enhanced or suppressed (\sigma_{SUSY}/\sigma_{SM}
varies from 0.7 to 2.4).Comment: 15 pages, 5 figure
The Status of RMB Financial Products of Commercial Banks in China: From the Perspective of Homogeneity
With the rapid development of commercial bank financial services in China, some problems arise in the process. This paper focuses on the widely concerned issue of homogeneity, basing on the classification of products, and takes the data from 2007 to 2013 about RMB financial products issued by 17 commercial banks as the sample to analyze the product type, minimum amount, investment period and returns of these products. Reasons for homogeneity will be discussed and recommendations in the aspects of customers, products, marketing channels and financial managers will be made to solve this problem
Interpreting the 750 GeV diphoton excess by the singlet extension of the Manohar-Wise Model
The evidence of a new scalar particle from the 750 GeV diphoton excess,
and the absence of any other signal of new physics at the LHC so far suggest
the existence of new colored scalars, which may be moderately light and thus
can induce sizable and couplings without resorting to
very strong interactions. Motivated by this speculation, we extend the
Manohar-Wise model by adding one gauge singlet scalar field. The resulting
theory then predicts one singlet dominated scalar as well as three kinds
of color-octet scalars, which can mediate through loops the and interactions. After fitting the model to the diphoton data at
the LHC, we find that in reasonable parameter regions the excess can be
explained at level by the process ,
and the best points predict the central value of the excess rate with
, which corresponds to a -value of . We also
consider the constraints from various LHC Run I signals, and we conclude that,
although these constraints are powerful in excluding the parameter space of the
model, the best points are still experimentally allowed.Comment: 19 pages, 3 figure
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