18677949
Separating Signals from Non-Interfering Backgrounds using Probabilistic Event Weightings
A common situation in experimental physics is to have a signal which can not be separated from a non-interfering background through the use of any cut. In this paper, we describe a procedure for determining, on an event-by-event basis, a quality factor (Q-factor) that a given event originated from the signal distribution. This Q-factor can then be used as an event weight in subsequent analysis procedures, allowing one to more directly access the true spectrum of the signal.
106656211
User analysis of LHCb data with Ganga
GANGA (http://cern.ch/ganga) is a job-management tool that offers a simple, efficient and consistent user analysis tool in a variety of heterogeneous environments: from local clusters to global Grid systems. Experiment specific plug-ins allow GANGA to be customised for each experiment. For LHCb users GANGA is the officially supported and advertised tool for job submission to the Grid. The LHCb specific plug-ins allow support for end-to-end analysis helping the user to perform his complete analysis with the help of GANGA. This starts with the support for data selection, where a user can select data sets from the LHCb Bookkeeping system. Next comes the set up for large analysis jobs: with tailored plug-ins for the LHCb core software, jobs can be managed by the splitting of these analysis jobs with the subsequent merging of the resulting files. Furthermore, GANGA offers support for Toy Monte-Carlos to help the user tune their analysis. In addition to describing the GANGA architecture, typical usage patterns within LHCb and experience with the updated LHCb DIRAC workload management system are presented.
10836022
Numerical object oriented quantum field theory calculations
The qft++ package is a library of C++ classes that facilitate numerical (not algebraic) quantum field theory calculations. Mathematical objects such as matrices, tensors, Dirac spinors, polarization and orbital angular momentum tensors, etc. are represented as C++ objects in qft++. The package permits construction of code which closely resembles quantum field theory expressions, allowing for quick and reliable calculations.
118827257
Who you gonna call? Runaway ghosts, higher derivatives and time-dependence in EFTs
A bstractWe briefly review the formulation of effective field theories (EFTs) in timedependent situations, with particular attention paid to their domain of validity. Our main interest is the extent to which solutions of the EFT capture the dynamics of the full theory. For a simple model we show by explicit calculation that the low-energy action obtained from a sensible UV completion need not take the restrictive form required to obtain only secondorder field equations, and we clarify why runaway solutions are nevertheless typically not a problem for the EFT. Although our results will not be surprising to many, to our knowledge they are only mentioned tangentially in the EFT literature, which (with a few exceptions) largely addresses time-independent situations.
119159946
Inflating with Large Effective Fields
We re-examine large scalar fields within effective field theory, in particular focussing on the issues raised by their use in inflationary models (as suggested by BICEP2 to obtain primordial tensor modes). We argue that when the large-field and low-energy regimes coincide the scalar dynamics is most effectively described in terms of an asymptotic large-field expansion whose form can be dictated by approximate symmetries, which also help control the size of quantum corrections. We discuss several possible symmetries that can achieve this, including pseudo-Goldstone inflatons characterized by a coset G/H (based on abelian and non-abelian, compact and non-compact symmetries), as well as symmetries that are intrinsically higher dimensional. Besides the usual trigonometric potentials of Natural Inflation we also find in this way simple large-field power laws (like V ∝ φ{sup 2}) and exponential potentials, V(φ) = ∑{sub k}V{sub x}e{sup −kφ/M}. Both of these can describe the data well and give slow-roll inflation for large fields without the need for a precise balancing of terms in the potential. The exponential potentials achieve large r through the limit |η| || e and so predict r ≅ (8/3)(1-n{sub s}); consequently n{sub s} ≅ 0.96 gives r ≅ 0.11 but not much larger (and so could be ruled out as measurements on r and n{sub s} improve).more » We examine the naturalness issues for these models and give simple examples where symmetries protect these forms, using both pseudo-Goldstone inflatons (with non-abelian non-compact shift symmetries following familiar techniques from chiral perturbation theory) and extra-dimensional models.« less
53692432
Distributed SUSY breaking: dark energy, Newton’s law and the LHC
A bstractWe identify the underlying symmetry mechanism that suppresses the low-energy effective 4D cosmological constant within some 6D supergravity models, generically leading to results suppressed by powers of the KK scale, mK K2, relative to the much larger size, m4, associated with mass-m particles localized in these models on codimension-2 branes. These models are examples for which the local conditions for unbroken supersymmetry can be satisfied locally everywhere within the extra dimensions, but are obstructed only by global conditions like flux quantization or by the mutual inconsistency of the boundary conditions required at the various branes. Consequently quantities (like vacuum energies) forbidden by supersymmetry cannot become nonzero until wavelengths of order the KK scale are integrated out, since only such long wavelength modes can see the entire space and so ‘know’ that supersymmetry has broken. We verify these arguments by extending earlier rugby-ball calculations of one-loop vacuum energies within these models to more general pairs of branes within two warped extra dimensions. For the Standard Model confined to one of two otherwise identical branes, the predicted effective 4D vacuum energy density is of order ρvac ⋍ C(mMg/4πMp)4 = C(5.6 × 10−5 eV)4, where Mg ≳ 10 TeV (corresponding to extra-dimensional size r ≲ 1 μm) and Mp = 2.44 × 1018 GeV are the 6D and 4D rationalized Planck scales, and m is the heaviest brane-localized particle. (For numerical purposes we take m to be the top-quark mass and take Mg as small as possible, consistent with energy-loss bounds from supernovae.) C is a constant depending on the details of the bulk spectrum, which could easily be of order 500 for each of hundreds of fields in the bulk. The value C ∼ 6 × 106 would give the observed Dark Energy density.
110521797
Ganga: User-friendly Grid job submission and management tool for LHC and beyond
Ganga has been widely used for several years in ATLAS, LHCb and a handful of other communities. Ganga provides a simple yet powerful interface for submitting and managing jobs to a variety of computing backends. The tool helps users configuring applications and keeping track of their work. With the major release of version 5 in summer 2008, Ganga's main user-friendly features have been strengthened. Examples include a new configuration interface, enhanced support for job collections, bulk operations and easier access to subjobs. In addition to the traditional batch and Grid backends such as Condor, LSF, PBS, gLite/EDG a point-to-point job execution via ssh on remote machines is now supported. Ganga is used as an interactive job submission interface for end-users, and also as a job submission component for higher-level tools. For example GangaRobot is used to perform automated, end-to-end testing of distributed data analysis. Ganga comes with an extensive test suite covering more than 350 test cases. The development model involves all active developers in the release management shifts which is an important and novel approach for the distributed software collaborations. Ganga 5 is a mature, stable and widely-used tool with long-term support from the HEP community.
118724352
Gravitational forces on a codimension-2 brane
A bstractWe compute the gravitational response of six dimensional gauged, chiral supergravity to localized stress energy on one of two space-filling branes, including the effects of compactifying the extra dimensions and brane back-reaction. We find a broad class of exact solutions, including various black-brane solutions. Several approximate solutions are also described, such as the near-horizon geometry of a small black hole which is argued to be approximately described by a 6D Schwarzschild (or Kerr) black hole, with event horizon appropriately modified to encode the brane back-reaction. The general linearized far-field solutions are found in the 4D regime very far from the source, and all integration constants are related to physical quantities describing the branes and the localized energy source. The localized source determines two of these, corresponding to the source mass and the size of the strength of a coupling to a 4D scalar mode whose mass is parametrically smaller than the KK scale. At large distances the solutions agree with those of 4D general relativity, but for an intermediate range of distances (larger than the KK scale) the solutions better fit a Brans-Dicke theory. For a realistic choice of parameters the KK scale could lie at a micron, while the crossover to Brans-Dicke behaviour could occur at around 10 microns. While allowed by present data this points to potentially measurable changes to Newton’s Law arising at distances larger than the KK scale.