118442865
Determining the dark matter particle mass through antler topology processes at lepton colliders
We study the kinematic cusps and endpoints of processes with the ``antler topology'' as a way to measure the masses of the parity-odd missing particle and the intermediate parent at a high energy lepton collider. The fixed center-of-mass energy at a lepton collider makes many new physics processes suitable for the study of the antler decay topology. It also provides new kinematic observables with cusp structures, optimal for the missing mass determination. We also study realistic effects on these observables, including initial state radiation, beamstrahlung, acceptance cuts, and detector resolution. We find that the new observables, such as the reconstructed invariant mass of invisible particles and the summed energy of the observable final state particles, appear to be more stable than the commonly considered energy endpoints against realistic factors and are very efficient at measuring the missing particle mass. For the sake of illustration, we study smuon pair production and chargino pair production within the framework of the minimal supersymmetric standard model. We adopt the log-likelihood method to optimize the analysis. We find that at the 500 GeV international linear collider (ILC), a precision of approximately 0.5 GeV can be achieved in the case of smuon production with a leptonic final state, and approximately 2 GeV in the case of chargino production with a hadronic final state.
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].
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.
206997636
CalcHEP 3.4 for collider physics within and beyond the Standard Model
We present version 3.4 of the CalcHEP software package which is designed for effective evaluation and simulation of high energy physics collider processes at parton level. The main features of CalcHEP are the computation of Feynman diagrams, integration over multi-particle phase space and event simulation at parton level. The principle attractive key-points along these lines are that it has: (a) an easy startup and usage even for those who are not familiar with CalcHEP and programming; (b) a friendly and convenient graphical user interface (GUI); (c) the option for the user to easily modify a model or introduce a new model by either using the graphical interface or by using an external package with the possibility of cross checking the results in different gauges; (d) a batch interface which allows to perform very complicated and tedious calculations connecting production and decay modes for processes with many particles in the final state. With this features set, CalcHEP can efficiently perform calculations with a high level of automation from a theory in the form of a Lagrangian down to phenomenology in the form of cross sections, parton level event simulation and various kinematical distributions. In this paper we report on the new features of CalcHEP 3.4 which improves the power of our package to be an effective tool for the study of modern collider phenomenology
119223957
Introducing an interface between WHIZARD and FeynRules
While Monte Carlo event generators like WHIZARD have become indispensable tools in studying the impact of new physics on collider observables over the last decades, the implementation of new models in such packages has remained a rather awkward and error-prone process. Recently, the FeynRules package was introduced which greatly simplifies this process by providing a single unified model format from which model implementations for many different Monte Carlo codes can be derived automatically. In this note, we present an interface which extends FeynRules to provide this functionality also for the WHIZARD package, thus making WHIZARD's strengths and performance easily available to model builders.
118577263
Vector Bosons Signals of Electroweak Symmetry Breaking
We study the physics potential of the 8 TeV LHC to discover signals of extended gauge models or extra dimensional models whose low energy behavior is well represented by an SU(2) x SU(2) x U(1) electroweak gauge structure. We find that with a combined integrated luminosity of 40 fb^(-1), the first new Kaluza-Klein mode of the W gauge boson can be discovered up to a mass of about 400 GeV, when produced in association with a Z boson.
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.
7900933
Improving the timing precision for inspiral signals found by interferometric gravitational wave detectors
As they take data and improve their sensitivities, interferometric gravitational wave detectors will eventually detect signals emitted by inspiralling compact binary systems. Determining the sky position of the source will require that the signal be recorded in several detectors. The precision of the source direction determination will be driven by that of the time-of-flight measurements between detectors, and ultimately by the timing precision at the level of each detector. The latter is limited by the noise of the detector and the use of template banks, which introduce some mismatches between the parameters of the signal and the parameters of the template used to detect it. The standard way for signal timing is based on referring to the end time of the signal. In this paper we show that this is not an optimal choice and the timing precision can be improved referring to a time when the signal crosses some reference frequency, whose optimal value depends on the detector sensitivity.
9176350
Inference on inspiral signals using LISA MLDC data
In this paper, we describe a Bayesian inference framework for the analysis of data obtained by LISA. We set up a model for binary inspiral signals as defined for the Mock LISA Data Challenge 1.2 (MLDC), and implemented a Markov chain Monte Carlo (MCMC) algorithm to facilitate exploration and integration of the posterior distribution over the nine-dimensional parameter space. Here, we present intermediate results showing how, using this method, information about the nine parameters can be extracted from the data.
30537390
Status of coalescing binaries search activities in Virgo
The interferometric gravitational wave detector Virgo is undergoing an advanced phase of its commissioning, during which short runs are routinely performed, in which data are analyzed online and offline, searching for signals from coalescing binary systems. In this report we present the progress of the coalescing binaries search activities in Virgo, and we describe details of the detection pipeline including hardware injections, vetoes, and parameter estimation, using recent data taking.
26080010
LIGO S6 detector characterization studies
LIGO recently commenced its sixth science run (S6) simultaneously with Virgo starting its second science run (VSR2). Because of differing interferometer configurations with respect to S5, much effort has been invested understanding new sources of noise in the LIGO S6 interferometers. The LIGO Scientific Collaboration's detector characterization working group is actively investigating the origin of noise in the LIGO interferometers and determining the periods of good, bad or questionable data quality. We describe the instrumental issues found to affect the data quality in S6 and the vetoes developed for burst and inspiral searches. The methods used to search for and identify periodic noise lines are also presented. A summary of other noise search efforts in S6 is also given.