High-precision analyses of supersymmetry parameters aim at reconstructing the fundamental supersymmetric theory and its breaking mechanism. A well defined theoretical framework is needed when higher-order corrections are included. We propose such a scheme, Supersymmetry Parameter Analysis SPA, based on a consistent set of conventions and input parameters. A repository for computer programs is provided which connect parameters in different schemes and relate the Lagrangian parameters to physical observables at LHC and high energy e + e- linear collider experiments, i.e., masses, mixings, decay widths and production cross sections for supersymmetric particles. In addition, programs for calculating high-precision low energy observables, the density of cold dark matter (CDM) in the universe as well as the cross sections for CDM search experiments are included. The SPA scheme still requires extended efforts on both the theoretical and experimental side before data can be evaluated in the future at the level of the desired precision. We take here an initial step of testing the SPA scheme by applying the techniques involved to a specific supersymmetry reference point.
Abstract High-resolution Hubble Space Telescope (HST) imaging observations of star cluster systems provide a very interesting and useful alternative to spectroscopic studies for stellar population analyses with 8-m class telescopes. Here, we assess the systematic uncertainties in (young) cluster age, mass and (to a lesser extent) extinction and metallicity determinations, based on broad-band imaging observations with the HST. Our aim here is to intercompare the results obtained using a variety of commonly used modelling techniques, specifically with respect to our own extensively tested multidimensional approach. Any significant differences among the resulting parameters are due to the details of the various, independently developed, modelling techniques used, rather than to the stellar population models themselves. Despite the model uncertainties and the selection effects inherent to most methods used, we find that the peaks in the relative age and mass distributions of a given young (≲109 yr) cluster system can be derived relatively robustly and consistently, to accuracies of σ t ≡Δ〈log(age/yr)〉≤ 0.35 and σ M ≡Δ〈log(M cl/M⊙)〉≤ 0.14, respectively, assuming Gaussian distributions in cluster ages and masses for reasons of simplicity. The peaks in the relative mass distributions can be obtained with a higher degree of confidence than those in the relative age distributions, as exemplified by the smaller spread among the peak values of the mass distributions derived. This implies that mass determinations are mostly insensitive to the approach adopted. We reiterate that as extensive a wavelength coverage as possible is required to obtain robust and internally consistent age and mass estimates for the individual objects, with reasonable uncertainties. Finally, we conclude that the actual filter systems used for the observations should be used for constructing model colours, instead of using conversion equations, to achieve more accurate derivations of ages and masses.
A general analysis of the sensitivities of neutron beta-decay experiments to manifestations of possible interaction beyond the standard model is carried out. In a consistent fashion, we take into account all known radiative and recoil corrections arising in the standard model. This provides a description of angular correlations in neutron decay in terms of one parameter, which is accurate to the level of similar to 10(-5). Based on this general expression, we present an analysis of the sensitivities to new physics for selected neutron decay experiments. We emphasize that the usual parametrization of experiments in terms of the tree-level coefficients a,A, and B is inadequate when the experimental sensitivities are at the same or higher level relative to the size of the corrections to the tree-level description.
Starting from a (new physics independent) tree level determination of (p) over bar and (eta) over bar, we perform the Unitarity Triangle analysis in general extensions of the Standard Model with arbitrary new physics contributions to loop-mediated processes. Using a simple parameterization, we determine the allowed ranges of non-standard contributions to vertical bar Delta F vertical bar = 2 processes. Remarkably, the recent measurements from B factories allow us to determine with good precision the shape of the Unitarity Triangle even in the presence of new physics, and to derive stringent constraints on nonstandard contributions to vertical bar Delta F vertical bar = 2 processes. Since the present experimental constraints favour models with Minimal Flavour Violation, we present the determination of the Universal Unitarity Triangle that can be defined in this class of extensions of the Standard Model. Finally, we perform a combined fit of the Unitarity Triangle and of new physics contributions in Minimal Flavour Violation, reaching a sensitivity to a new physics scale of about 5TeV. We also extrapolate all these analyses into a "year 2010" scenario for experimental and theoretical inputs in the flavour sector. All the results presented in this paper are also available at the URL http://www.utfit.org, where they are continuously updated.
With currently available XMM- Newton EPIC pn observations spanned over about 3 yr, we present a detailed spectral and temporal variability of the 0.2 - 10 keV X- ray emission from the X- ray- bright BL Lac object PKS 2155 - 304. The spectral variability is examined with a model- independent hardness ratio method. We find that the spectral evolution of the source follows the light curves well, indicating that the spectra harden when the fluxes increase. The plots of hardness ratios versus count rates show that the spectral changes are particularly significant during flares. The cross- correlation functions ( CCFs) show that the light curves in the different energy bands are well correlated at different time lags. The CCF peaks ( i. e., the maximum correlation coefficients) tend to become smaller with larger energy differences, and the variabilities in the different energy bands are more correlated for the flares than for the other cases. In most cases the higher energy band variations lead the lower energy band, but in two cases we observed the opposite behavior, that the lower energy variability possibly leads the higher energy variability. The time lags increase with the energy differences between the two cross- correlated light curves. The maximum lag is found to be up to about 1 hr, supporting the findings obtained with previous low Earth orbit X- ray missions. We discuss our results in the context of the particle acceleration, cooling, and light- crossing timescales.
To be a formation mechanism of such large-scale structures as giant molecular clouds (GMCs) and H I superclouds, the classical Parker instability driven by external gravity has to overcome three major obstacles: The convective motions accompanying the instability would generate thin sheets rather than large condensations. The degree of density enhancement achieved by the instability turns out too low to make even diffuse interstellar clouds. The time and the length scales of the instability are longer and larger than the estimated formation time and the observed mean separation of the GMCs, respectively. This study examines whether a replacement of the driving agent from the external to the self-gravity might remove these obstacles by activating the gravitational instability in the Galactic ISM disk. Self-gravitating, magnetized, gas disk bound by a hot halo medium is subject to a Parker-type instability, the usual Jeans gravitational instability, and convection. Under the external gravity growth rate of the convection triggered by interchange mode perturbations increases without bound as the perturbation wavelength decreases; however, under the self-gravity, it reaches a finite value asymptotically. The presence of self-gravity can suppress the convective motions and enhance the density sufficiently high to form clouds. However, the mass and mean separation of the structures resulting from odd-parity undular mode perturbations under the self-gravity are consistent with the H I superclouds rather than the GMCs. To have structures of both scales, it seems necessary to consider a sum of the self and external gravities as the driving agent of the Parker instability.
It is a recurrent issue in astronomical data analysis that observations are unevenly sampled or incomplete maps with missing patches or intentionaly masked parts. In addition, many astrophysical emissions are non stationary processes over the sky. Hence spectral estimation using standard Fourier transforms is no longer reliable. Spectral matching ICA (SMICA) is a source separation method based on covariance matching in Fourier space which is successfully used for the separation of diffuse astrophysical emissions in Cosmic Microwave Background observations. We show here that wavelets, which are standard tools in processing non stationary data, can profitably be used to extend SMICA. Among possible applications, it is shown that gaps in data are dealt with more conveniently and with better results using this extension, wSMICA, in place of the original SMICA. The performances of these two methods are compared on simulated CMB data sets, demonstrating the advantageous use of wavelets.
Abundances of about 18 elements including the heavy elements Y and Zr are determined from Hubble Space Telescope Space Telescope Imaging Spectrograph ultraviolet spectra of seven extreme helium stars (EHes): LSE 78, BD + 10 2179, V1920 Cyg, HD 124448, PV Tel, LS IV-12, and FQ Aqr. New optical spectra of BD + 10 2179, V1920 Cyg, and HD 124448 were analyzed, and published line lists of LSE 78, HD 124448, and PV Tel were analyzed afresh. The abundance analyses are done using LTE line formation and LTE model atmospheres especially constructed for these EHes. The stellar parameters derived from an EHe's UV spectrum are in satisfactory agreement with those derived from its optical spectrum. Adopted abundances for the seven EHes are from a combination of the UV and optical analyses. Published results for an additional 10 EHes provide abundances obtained in a nearly uniform manner for a total of 17 EHes, the largest sample on record. The initial metallicity of an EHe is indicated by the abundance of elements from Al to Ni; Fe is adopted to be the representative of initial metallicity. Iron abundances range from approximately solar to about 1/100 solar. Clues to EHe evolution are contained within the H, He, C, N, O, Y, and Zr abundances. Two novel results are (1) the O abundance for some stars is close to the predicted initial abundance yet the N abundance indicates almost complete conversion of initial C, N, and O to N by the CNO cycles; and (2) three of the seven stars with UV spectra show a strong enhancement of Y and Zr attributable to an s-process. The observed compositions are discussed in light of expectations from accretion of an He white dwarf by a C-O white dwarf. Qualitative agreement seems likely except that a problem may be presented by those stars in which the O abundance is close to the initial O abundance.