119205456
Supersymmetric Higgs Production in Vector-Boson Fusion
We present a full calculation of the supersymmetric NLO corrections to Higgs boson production via vector-boson fusion. The supersymmetric QCD corrections turn out to be significantly smaller than the electroweak ones. These higher-order corrections are an important ingredient to a precision analysis of the Higgs sector at the LHC.
123906099
Helmholtz Alliance Linear Collider Forum
Supersymmetric scenarios with a very weakly interacting lightest superpartner (LSP) - like the gravitino or axino - naturally give rise to a long-lived next-to-LSP (NLSP). If the NLSP is a charged slepton it leaves a very distinct signature in a collider experiment. At the ILC/CLIC it will be possible to capture a significant fraction of the produced charged sleptons and observe their decays. These decays potentially reveal the nature of the LSP and thus provide a unique possibility to measure the properties of a very weakly interacting LSP which otherwise is most likely hidden from any other observation, like direct or indirect dark matter searches. We review the proposals that have been made to measure the LSP properties at the ILC/CLIC and compare its potential to the capability of the LHC.
119114605
Physics beyond the standard model: supersymmetry
This collection of studies on new physics at the LHC constitutes the report of the supersymmetry working group at the Workshop 'Physics at TeV Colliders', Les Houches, France, 2007. They cover the wide spectrum of phenomenology in the LHC era, from alternative models and signatures to the extraction of relevant observables, the study of the MSSM parameter space and finally to the interplay of LHC observations with additional data expected on a similar time scale. The special feature of this collection is that while not each of the studies is explicitly performed together by theoretical and experimental LHC physicists, all of them were inspired by and discussed in this particular environment.
119257516
Di-boson and Tri-boson production at the LHC
The status of di-boson and tri-boson production is shortly review. Using the VBFNLO and the LOOPSIM package, approximated results at NNLO QCD are given for WZ production. Results for waa + jet at NLO QCD are also shown.
116260923
NLO QCD corrections to $W^\pm Z\gamma$ production with leptonic decays
We present a computation of the O(alpha_s) QCD corrections to W^\pm Z \gamma production at the Large Hadron Collider. The photon is considered as real, and we include full leptonic decays for the W and Z bosons. Based on the structure of the VBFNLO program package, we obtain numerical results through a fully flexible Monte Carlo program, which allows to implement general cuts and distributions of the final-state particles. The NLO QCD corrections are sizable and strongly exceed the theory error obtained by a scale variation of the leading-order result. Also, the shapes of relevant observables are significantly altered.
246159
Complete one-loop calculation of the T-violating D-parameter in neutron decay in the MSSM
Abstract.We investigate the violation of time reversal invariance in the decay of the free neutron in the framework of the minimal supersymmetric standard model (MSSM). The coefficient of the triple product of the neutron spin and the momenta of electron and neutrino, the so-called D parameter, is computed at one-loop order including all diagrams. We find that D is mainly sensitive to the trilinear A coupling in the squark sector and to the phase of the coefficient $\mu$ which mixes the two Higgs superfields. The maximal MSSM contribution using parameters still allowed by experiment is however at $D \approx 10^{-7}$, while QED final state interactions give a value of $D_{\mathrm {fsi}} = - 2.3 \cdot 10^{-5}$. Explicit expressions for all relevant diagrams are given in an appendix.
13952549
The thermal history of the intergalactic medium
At redshifts z≳2, most of the baryons reside in the smooth intergalactic medium which is responsible for the low column density Lyα forest. This photoheated gas follows a tight temperature–density relation which introduces a cut-off in the distribution of widths of the Lyα absorption lines (b-parameters) as a function of column density. We have measured this cut-off in a sample of nine high-resolution, high signal-to-noise ratio quasar spectra and determined the thermal evolution of the intergalactic medium in the redshift range 2.0–4.5. At a redshift z∼3, the temperature at the mean density shows a peak and the gas becomes nearly isothermal. We interpret this as evidence for the reionization of He ii.
16922508
KECK HIRES Spectroscopy of APM 08279+52551
ABSTRACT With an optical R‐band magnitude of 15.2, the recently discovered \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $z=3.911$ \end{document} broad absorption line quasar APM 08279+5255 is an exceptionally bright high‐redshift source. Its brightness has allowed us to acquire a high signal‐to‐noise ratio (∼80), high‐resolution (∼6 km s−1) spectrum using the HIRES echelle spectrograph on the 10 m Keck I telescope. Given the quality of the data, these observations provide an unprecedented view of associated and intervening abs...
21579630
THE LYMAN ALPHA FOREST IN THE SPECTRA OF QUASISTELLAR OBJECTS
Observations of redshifted Lyman alpha (Ly alpha) forest absorption in the spectra of quasistellar objects (QSOs) provide a highly sensitive probe of the distribution of gaseous matter in the universe. Over the past two decades, optical spectroscopy with large ground-based telescopes, and more recently ultraviolet (UV) spectroscopy from space, have yielded a wealth of information on what appears to be a gaseous, photoionized intergalactic medium (IGM), partly enriched by the products of stellar nucleosynthesis, residing in coherent structures over many hundreds of kiloparsecs. 
Recent progress with cosmological hydro-simulations based or hierarchical structure formation models has led to important insights into the physical structures giving rise to the forest. If these ideas are correct, a truly inter- and protogalactic medium [at high redshift (z similar to 3), the main repository of baryons] collapses under the influence of dark matter gravity into flattened or filamentary structures, which are seen in absorption against background QSOs. With decreasing redshift, galaxies forming in the denser regions may contribute an increasing part of the Ly alpha absorption cross section. Comparisons between large data samples from the new generation of telescopes and artificial Ly alpha forest spectra from cosmological simulations promise to become a useful cosmological tool.
14687651
Metallicity of the Intergalactic Medium Using Pixel Statistics. II. The Distribution of Metals as Traced by C IV
We measure the distribution of carbon in the intergalactic medium as a function of redshift z and overdensity δ. Using a hydrodynamical simulation to link the H I absorption to the density and temperature of the absorbing gas, and a model for the UV background radiation, we convert ratios of C IV to H I pixel optical depths into carbon abundances. For the median metallicity this technique was described and tested in Paper I of this series. Here we generalize it to reconstruct the full probability distribution of the carbon abundance and apply it to 19 high-quality quasar absorption spectra. We find that the carbon abundance is spatially highly inhomogeneous and is well described by a lognormal distribution for fixed δ and z. Using data in the range log δ = -0.5-1.8 and z = 1.8-4.1, and a renormalized version of the 2001 Haardt & Madau model for the UV background radiation from galaxies and quasars, we measure a median metallicity of [C/H] = -3.47 + 0.08(z - 3) + 0.65(log δ - 0.5) and a lognormal scatter of σ([C/H]) = 0.76 + 0.02(z - 3) - 0.23(log δ - 0.5). Thus, we find significant trends with overdensity but no evidence for evolution. These measurements imply that gas in this density range accounts for a cosmic carbon abundance of [C/H] = -2.80 ± 0.13 (ΩC ≈ 2 × 10-7), with no evidence for evolution. The dominant source of systematic error is the spectral shape of the UV background, with harder spectra yielding higher carbon abundances. While the systematic errors due to uncertainties in the spectral hardness may exceed the quoted statistical errors for δ < 10, we stress that UV backgrounds that differ significantly from our fiducial model give unphysical results. The measured lognormal scatter is strictly independent of the spectral shape, provided the background radiation is uniform. We also present measurements of the C III/C IV ratio (which rule out temperatures high enough for collisional ionization to be important for the observed C IV) and of the evolution of the effective Lyα optical depth.
990490
AN HST SEARCH FOR SUPERNOVAE ACCOMPANYING X-RAY FLASHES
We present the results from a Hubble Space Telescope ACS search for supernovae associated with X-ray flashes 020903, 040701, 040812, and 040916. We find strong evidence that XRF 020903 (z = 0.25) was associated with a SN 1998bw-like supernova and confirm this using optical spectroscopy at t ~ 25 days. We find no evidence, however, for SN 1998bw-like supernovae associated with the other three events. In the case of XRF 040701 (z = 0.21), we rule out even a faint supernova similar to SN 2002ap, using template light curves for several local Type Ic supernovae. For the two cases in which the redshift is not known, XRFs 040812 and 040916, we derive robust redshift limits, assuming that they were accompanied by supernovae similar to SN 1998bw, and compare these limits with photometric redshift constraints provided by their host galaxies. We supplement this analysis with results for three additional events (XRFs 011030, 020427, and 030723) and discuss the observed diversity of supernovae associated with X-ray flashes and gamma-ray bursts. We conclude that XRF-SNe exist but can be significantly fainter than SN 1998bw, possibly consistent with the observed spread in local Type Ibc supernovae.