409 research outputs found
Probing New Physics through mu-e Universality in K->lnu
The recent NA48/2 improvement on R_K=Gamma(K->e nu_e)/Gamma(K->mu nu_mu)
emphasizes the role of K_l2 decays in probing the mu-e universality.
Supersymmetric (SUSY) extensions of the Standard Model can exhibit mu-e
non-universal contributions. Their origin is twofold: those deriving from
lepton flavor conserving couplings are subdominant with respect to those
arising from lepton flavor violating (LFV) sources. We show that mu-e
non-universality in K_l2 is quite effective in constraining relevant regions of
SUSY models with LFV (for instance, supergravities with a see-saw mechanism for
neutrino masses). A comparison with analogous bounds coming from tau LFV decays
proves the relevance of the measurement of R_K to probe LFV in SUSY.Comment: v2: 5 pages, 1 figure. Comments and 2 references adde
The CMCC-INGV Global Ocean Data Assimilation System (CIGODAS)
This report summarizes the technical structure and main
characteristics of the CMCCINGV Global Ocean Data Assimilation System (CIGODAS) based on a Reduced Order Optimal Interpolation scheme and a coarse resolution Global Ocean Model for the assimilation of temperature and salinity observations. It is intended to be a reference guide for new users who are interested in setting up and running an experiment using this approach and producing estimates of the timevarying, threedimensional state of the global ocean
Gamma Ray Constraints on Flavor Violating Asymmetric Dark Matter
We show how cosmic gamma rays can be used to constrain models of asymmetric
Dark Matter decaying into lepton pairs by violating flavor. First of all we
require the models to explain the anomalies in the charged cosmic rays measured
by PAMELA, FERMI and HESS; performing combined fits we determine the allowed
values of the Dark Matter mass and lifetime. For these models, we then
determine the constraints coming from the measurement of the isotropic
gamma-ray background by FERMI for a complete set of lepton flavor violating
primary modes and over a range of DM masses from 100 GeV to 10 TeV. We find
that the FERMI constraints rule out the flavor violating asymmetric Dark Matter
interpretation of the charged cosmic ray anomalies.Comment: 11 pages, 3 figures. v2: constraints derivation slightly modified,
conclusions unchanged; some clarifications and some references added; matches
version published on JCA
Global ocean re-analyses for climate applications
One of the main objectives of the global ocean modelling activities
at Centro Euro-Mediterraneo per i Cambiamenti Climatici (CMCC)
is the production of global ocean re-analyses over multidecadal
periods to reconstruct the state of the ocean and the large scale cir-
culation over the recent past. The re-analyses are used for climate applications
and for the assessment of the beneïŹts of assimilating
ocean
observations on seasonal and longer predictions.
Here
we present the main characteristics of an optimal interpola-
tion
based assimilation system used to produce a set of global ocean
re-analyses
validated against a set of high quality in situ observa-
tions
and independent data. Differences among the experiments
of
the set are analyzed in terms of improvements in the method
used
to assimilate the data and the quality of observations them-
selves.
For example, the integrated ocean heat content, which can
be
taken as an indicator of climate changes, is examined to detect
possible
sources of uncertainty of its long-term changes. Global and
basin
scale upper ocean heat content exhibits warming trends over
the
last few decades that still depend in a signiïŹcant way on the
assimilated
observations and the formulation of the background
covariances.
However, all the re-analyses show a global warming
trend
of the oceanic uppermost 700 m over the last ïŹve decades
that
falls within the range of the most recent observation-based
estimates.
The largest discrepancies between our estimates and
observational
based ones are conïŹned in the upwelling regions of
the
PaciïŹcandAtlanticOceans.Finally,theresultsshow that the climatological
heat and salt transports as a function of latitude also
fall
within the range of the estimates based on observations and
atmospheric
re-analyses
A Theory of a Spot
We present a simple inflationary scenario that can produce arbitrarily large
spherical underdense or overdense regions embedded in a standard Lambda cold
dark matter paradigm, which we refer to as bubbles. We analyze the effect such
bubbles would have on the Cosmic Microwave Background (CMB). For super-horizon
sized bubble in the vicinity of the last scattering surface, a signal is
imprinted onto CMB via a combination of Sach-Wolfe and an early integrated
Sach-Wolfe (ISW) effects. Smaller, sub-horizon sized bubbles at lower redshifts
(during matter domination and later) can imprint secondary anisotropies on the
CMB via Rees-Sciama, late-time ISW and Ostriker-Vishniac effects. Our scenario,
and arguably most similar inflationary models, produce bubbles which are
over/underdense in potential: in density such bubbles are characterized by
having a distinct wall with the interior staying at the cosmic mean density. We
show that such models can potentially, with only moderate fine tuning, explain
the \emph{cold spot}, a non-Gaussian feature identified in the Wilkinson
Microwave Anisotropy Probe (WMAP) data by several authors. However, more
detailed comparisons with current and future CMB data are necessary to confirm
(or rule out) this scenario.Comment: 19 pages, 19 figures, added references and explanations, JCAP in
pres
The INGV-CMCC Seasonal Prediction System: improved ocean initial conditions
The development of the INGV (Istituto Nazionale di Geofisica e Vulcanologia)-CMCC (Centro
Euro-Mediterraneo per i Cambiamenti Climatici) Seasonal Prediction System (SPS) is
documented. In this SPS the ocean initial conditions estimation includes a Reduced Order
Optimal Interpolation procedure for the assimilation of temperature and salinity profiles
at the global scale. Nine member ensemble forecasts have been produced for the period
1991-2003 for two starting dates per year in order to assess the impact of the subsurface
assimilation in the ocean for initialization.
Comparing the results with control simulations (i.e.: without assimilation of subsurface
profiles during ocean initialization), we showed that the improved ocean initialization increases
the skill in the prediction of tropical Pacific SSTs in our system for boreal winter
forecasts. Considering the forecast of the El NiËno 1997-1998, the data assimilation in the
ocean initial conditions leads to a considerable improvement in the representation of its onset
and development.
Our results indicate a better prediction of global scale surface climate anomalies for the
forecasts started in November, probably due to the improvement in the tropical Pacific. For
boreal winter, in both tropics and extra tropics, we show significant increases in the capability
of the system to discriminate above normal and below normal temperature anomalies
Evaluation of the CMCC global eddying ocean model for the Ocean Model Intercomparison Project (OMIP2)
This paper describes the global eddying oceanâsea ice simulation produced at the Euro-Mediterranean Center on Climate Change (CMCC) obtained following the experimental design of the Ocean Model Intercomparison Project phase 2 (OMIP2). The eddy-rich model (GLOB16) is based on the NEMOv3.6 framework, with a global horizontal resolution of 1/16â and 98 vertical levels and was originally designed for an operational short-term ocean forecasting system. Here, it is driven by one multi-decadal cycle of the prescribed JRA55-do atmospheric reanalysis and runoff dataset in order to perform a long-term benchmarking experiment.
To assess the accuracy of simulated 3D ocean fields and highlight the relative benefits of resolving mesoscale processes, the GLOB16 performances are evaluated via a selection of key climate metrics against observational datasets and two other NEMO configurations at lower resolutions: an eddy-permitting resolution (ORCA025) and a non-eddying resolution (ORCA1) designed to form the oceanâsea ice component of the fully coupled CMCC climate model.
The well-known biases in the low-resolution simulations are significantly improved in the high-resolution model. The evolution and spatial pattern of large-scale features (such as sea surface temperature biases and winter mixed-layer structure) in GLOB16 are generally better reproduced, and the large-scale circulation is remarkably improved compared to the low-resolution oceans. We find that eddying resolution is an advantage in resolving the structure of western boundary currents, the overturning cells, and flow through key passages. GLOB16 might be an appropriate tool for ocean climate modeling efforts, even though the benefit of eddying resolution does not provide unambiguous advances for all ocean variables in all regions.</p
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