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.
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.
122598875
RESULTS FROM LIGO OBSERVATIONS: STOCHASTIC BACKGROUND AND CONTINUOUS WAVE SIGNALS
The search for gravitational radiation has entered a new era as the Laser Interferom-eter Gravitational Wave Observatory (LIGO) has reached its initial target sensitivity. Other similar interferometric detectors are also approaching their design goals. There is presently vigorous activity in the gravitational radiation community in the search for signals. Here we review the status of the LIGO search for a stochastic background, and continuous wave signals.
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.
15022161
A first comparison of search methods for gravitational wave bursts using LIGO and Virgo simulated data
We present a comparative study of six search methods for gravitational wave bursts using simulated LIGO and Virgo noise data. The simulated data were generated according to the design sensitivity of the two 4 km LIGO interferometers and the 3 km Virgo interferometer. The searches were applied on replicas of the data sets to which eight different signals were injected. Three figures of merit were employed in this analysis: (a) receiver operator characteristic curves, (b) necessary signal-to-noise ratios for the searches to achieve 50% and 90% efficiencies and (c) variance and bias for the estimation of the arrival time of a gravitational wave burst.
13085972
Using Markov chain Monte Carlo methods for estimating parameters with gravitational radiation data
We present a Bayesian approach to the problem of determining parameters for coalescing binary systems observed with laser interferometric detectors. By applying a Markov Chain Monte Carlo (MCMC) algorithm, specifically the Gibbs sampler, we demonstrate the potential that MCMC techniques may hold for the computation of posterior distributions of parameters of the binary system that created the gravity radiation signal. We describe the use of the Gibbs sampler method, and present examples whereby signals are detected and analyzed from within noisy data.
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.
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.
119258873
MSSM Higgs bosons at the LHC
Accepting the existence of a SM-like Higgs boson in the range 123GeV-127GeV as indicated by the observed ga,ga events, there are two distinct regions left in the Minimal Supersymmetric (SUSY) Standard Model (MSSM) Higgs sector: (a) the lighter CP-even Higgs boson SM-like and the non-SM-like Higgs bosons all heavy and nearly degenerate above 300GeV; (b) the heavier CP-even Higgs boson being SM-like and the neutral non-SM-like Higgs bosons all nearly degenerate around 100GeV (a non-decoupling region). Due to the strong correlation between the Higgs decays to W+W- and to ga,ga predicted in the MSSM, the deficit of a W+W- final state signal would be in direct conflict with the ga,ga peak. If we consider W+W- on its own, the absence of the W+W- signal would imply that the SM-like Higgs boson has reduced coupling to W+-, and that the other non-SM-like Higgs bosons should not be too heavy and do not decouple. If both the ga,ga excess and the absence of W+W- continue, new physics beyond the MSSM will be required. A similar correlation exists between the W+W- and tau+tau- channels: a reduced W+W- channel would force the tau+tau- channel to be larger. Future searches for the SM-like Higgs boson at the LHC will provide critical tests for the MSSM prediction. We emphasize the potential importance of the electroweak processes pp->H+H-, H+-A0, which are independent of the SUSY parameters except for their masses. In addition, there may be sizable contributions from pp->H+-h0, A0h0 and W+-H0, ZH0 in the non-decoupling region, which may serve to discriminate the model parameters. We vary the relevant SUSY parameters in a broad range and demonstrate the correlations and constraints on these parameters and associated SUSY particles.
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.
16128170
SLHAplus: A library for implementing extensions of the standard model
We provide a library to facilitate the implementation of new models in codes such as matrix element and event generators or codes for computing dark matter observables. The library contains a SLHA reader routine as well as diagonalisation routines. This library is also available in CalcHEP, micrOMEGAs and LanHEP. In the very near future the LHC will have the opportunity to test the TeV scale relevant to address the outstanding issues in the standard model and its extensions: the symmetry breaking problem and the dark matter problem. Furthermore numerous astroparticle searches will help refine the dark matter properties. Confronting the various extensions of the standard model that have been proposed with observations at colliders and astroparticle searches will therefore provide powerful tests of the new physics model. Sophisticated tools have been developed to compute the predictions for observables such as particle spectra, decay rates or cross sections that are relevant at colliders ( for a repository of available tools see [1]) while other tools explore the implications of new physics models for dark matter observables [2, 3, 4, 5, 6]. The interpretation of a new signature might require extending those tools to adapt them to work with different models. Tools such as LanHEP [7], Feynrules [34] and SARAH [9] have been developed to facilitate the implementation of new models in generic matrix elements and event generators such as Madgraph [10], CompHEP [11, 12], CalcHEP [13], FeynArts/FormCalc [14, 15] and Sherpa [16]. They require mainly the implementation of a new Lagrangian and provide the model file adapted to the chosen generator. While these tools are very powerful they often leave some tedious and repetitive tasks for the user. Here we provide a library that contains some routines to facilitate the implementation of new models. The library first contains a routine for reading a SUSY Les Houches Accord (SLHA) file [17, 18]. An SLHA file is a standardized file format specifying input and output parameters that was developed in the framework of supersymmetry to facilitate the passing of information beween codes as varied as spectrum calculators, matrix element generators or event generators. 1 We have generalised the procedure to take into account an arbitrary number of blocks so that the reader can be used in generic models including non supersymmetric ones. The library also contains routines to diagonalise real mass matrices with either unitary or 1 Another SLHA reader library that can be used with the MSSM and its extensions is available at [19].