28345902
Bayesian modeling of source confusion in LISA data
One of the greatest data analysis challenges for the Laser Interferometer Space Antenna (LISA) is the need to account for a large number of gravitational wave signals from compact binary systems expected to be present in the data. We introduce the basis of a Bayesian method that we believe can address this challenge and demonstrate its effectiveness on a simplified problem involving 100 synthetic sinusoidal signals in noise. We use a reversible jump Markov chain Monte Carlo technique to infer simultaneously the number of signals present, the parameters of each identified signal, and the noise level. Our approach therefore tackles the detection and parameter estimation problems simultaneously, without the need to evaluate formal model selection criteria, such as the Akaike Information Criterion or explicit Bayes factors. The method does not require a stopping criterion to determine the number of signals and produces results which compare very favorably with classical spectral techniques.
2702261
LISA source confusion: identification and characterization of signals
The Laser Interferometer Space Antenna (LISA) is expected to detect gravitational radiation from a large number of compact binary systems. We present a method by which these signals can be identified and have their parameters estimated. Our approach uses Bayesian inference, specifically the application of a Markov chain Monte Carlo method. The simulation study that we present here considers a large number of sinusoidal signals in noise, and our method estimates the number of periodic signals present in the data, the parameters for these signals and the noise level. The method is significantly better than classical spectral techniques at performing these tasks and does not use stopping criteria for estimating the number of signals present.
15589153
A time-domain MCMC search and upper limit technique for gravitational waves of uncertain frequency from a targeted neutron star
It is computationally expensive to search the large parameter space associated with a gravitational wave signal of uncertain frequency, such as might be expected from the possible pulsar generated by SN1987A. To address this difficulty we have developed a Markov Chain Monte Carlo method that performs a time-domain Bayesian search for a signal over a 4 Hz frequency band and a spindown of magnitude of up to 1 ? 10?9 Hz s?1. We use Monte Carlo simulations to set upper limits on signal amplitude with this technique, which we intend to apply to a gravitational wave search.
122531619
Measuring the stochastic gravitational-radiation background with laser-interferometric antennas.
A study of the method of detecting a stochastic gravitation-wave background (SGWB) with laser-interferometric gravitational-wave antennas is presented. The SGWB can be measured by correlating the output of two or more detectors. The results in this paper can be applied to the planned new generation of kilometer length interferometers, such as the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the United States, or similar systems in other countries. Advanced detectors will be able to limit the gravity-wave background energy density per logarithmic interval at 100 Hz to 2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}10}$ times the closure density of the Universe. A survey of potential sources indicates that a pair of antennas will be able to confirm or deny the existence of cosmic strings, or may detect the background produced by extragalactic neutron star binaries. Elements of the optimal interferometer design and orientation for detecting the SGWB, or any gravity wave, are given. In particular, the criteria for orienting a pair of antennas, the trade-off between sensitivity and bandwidth, and the effect of antenna separation on the correlation are presented. A procedure for obtaining the correlated signal from two interferometers is given. The statistical basis of the correlation experiment is presented. The cause and effect of correlated noise is examined. Filtering and data analysis issues are also discussed.
15806292
The Age of the Universe and the Cosmological Constant Determined from Cosmic Microwave Background Anisotropy Measurements
If Ωtot = 1 and structure formed from adiabatic initial conditions, then the age of the universe, as constrained by measurements of the cosmic microwave background (CMB), is t0 = 14.0 ± 0.5 Gyr. The uncertainty is surprisingly small given that CMB data alone do not significantly constrain either h or ΩΛ. This small uncertainty is due to the tight (and accidental) correlation in flat adiabatic models of the age with the angle subtended by the sound horizon on the last-scattering surface and, thus, with the well-determined acoustic peak locations. If we assume either the Hubble Space Telescope Key Project result h = 0.72 ± 0.08 or simply that h > 0.55, we find ΩΛ > 0.4 at 95% confidence—another argument for dark energy, independent of supernovae observations. Our analysis is greatly simplified by the Monte Carlo Markov chain approach to Bayesian inference combined with a fast method for calculating angular power spectra.
43905547
Veto studies for LIGO inspiral triggers
LIGO recently conducted its third scientific data run, S3. Here, we summarize the veto and data quality studies conducted by the LIGO Scientific Collaboration in connection with the search for binary inspiral signals in the S3 data. The veto results presented here come from studies on the S3 playground data. LIGO's interferometer channels and physical environmental monitors were monitored, and events in these channels coincident with inspiral triggers were examined.
12180176
FeynRules - Feynman rules made easy
In this paper we present FeynRules, a new Mathematica package that facilitates the implementation of new particle physics models. After the user implements the basic model information (e.g. particle content, parameters and Lagrangian), FeynRules derives the Feynman rules and stores them in a generic form suitable for translation to any Feynman diagram calculation program. The model can then be translated to the format specific to a particular Feynman diagram calculator via FeynRules translation interfaces. Such interfaces have been written for CalcHEP/CompHEP, FeynArts/FormCalc, MadGraph/MadEvent and Sherpa, making it possible to write a new model once and have it work in all of these programs. In this paper, we describe how to implement a new model, generate the Feynman rules, use a generic translation interface, and write a new translation interface. We also discuss the details of the FeynRules code. Comment: 63 pages, 3 figures, 17 tables, elsart
51806520
New developments in FEYNRULES
The program FeynRules is a Mathematica package developed to facilitate the implementation of new physics theories into high-energy physics tools. Starting from a minimal set of information such as the model gauge symmetries, its particle content, parameters and Lagrangian, FeynRules provides all necessary routines to extract automatically from the Lagrangian (that can also be computed semi-automatically for supersymmetric theories) the associated Feynman rules. These can be further exported to several Monte Carlo event generators through dedicated interfaces, as well as translated into a Python library, under the so-called UFO model format, agnostic of the model complexity, especially in terms of Lorentz and/or color structures appearing in the vertices or of number of external legs. In this work, we briefly report on the most recent new features that have been added to FeynRules, including full support for spin- 3 fermions, a new module allowing for the automated diagonalization of the particle spectrum and a new set of routines dedicated to decay width calculations.
53470475
Implications of dynamical generation of standard-model fermion masses
We point out that if quark and lepton masses arise dynamically, then in a wide class of theories the corresponding running masses m{sub f{sub j}}(p) exhibit the power-law decay m{sub f{sub j}}(p){proportional_to}{lambda}{sub j}{sup 2}/p{sup 2} for Euclidean momenta p>>{lambda}{sub j}, where f{sub j} is a fermion of generation j, and {lambda}{sub j} is the maximal scale relevant for the origin of m{sub f{sub j}}. We estimate resultant changes in precision electroweak quantities and compare with current data. It is found that these data allow the presence of such corrections. We also note that this power-law decay renders primitively divergent fermion mass corrections finite.
119230543
Pair production of MSSM Higgs bosons in the nondecoupling region at the LHC
We consider the Higgs boson signals from pair production at the LHC within the framework of the MSSM in the non-decoupling (low-m_A) region. In light of the recent observation of a SM-like Higgs boson, we argue that the exploration for Higgs pair production at the LHC is a crucial next step to probe the MSSM Higgs sector. We emphasize that the production of H^\pm A^0 and H^{+}H^{-} depends only on the electroweak gauge couplings while all the leading Higgs production channels via gluon fusion, vector-boson fusion, and Higgsstrahlung depend on additional free Higgs sector parameters. In the non-decoupling region, the five MSSM Higgs bosons are all relatively light and pair production signals may be accessible. We find that at the 8 TeV LHC, a 5\sigma signal for H^\pm A^0, H^\pm h^0 -> \tau^{\pm}\nu b\bar b and H^{+}H^{-} -> \tau^{+}\nu \tau^{-}\nu are achievable with an integrated luminosity of 7 (11) fb^{-1} and 24 (48) fb^{-1}, respectively for m_A=95 (130) GeV. At the 14 TeV LHC, a 5\sigma signal for these two channels would require as little as 4 (7) fb^{-1} and 10 (19) fb^{-1}, respectively.
118524954
Deconstructed Higgsless Models at LHC: The Top Triangle Moose
We describe a deconstructed Higgsless model in which electroweak symmetry breaking results largely from a Higgsless mechanism while the top quark mass is generated by a topcolor mechanism. The top quark mass arises from a Yukawa coupling to an effective top-Higgs which develops a small vacuum expectation value. Both the heavy partners of the electoweak gauge bosons and those for the SM fermions can be light enough to be visible at LHC.