119188732
Multi-boson Production in Weak Boson Fusion
The production of multiple gauge bosons via weak boson fusion is an important process at the LHC. It is relevant as a background process appearing in many searches and measurements, but also serves as a signal process when studying new-physics contributions to triple and in particular quartic gauge boson vertices. 
We first review the theoretical status of multi-boson production in weak boson fusion and present the current state of the art. In the second part, the impact of anomalous gauge couplings on this class of processes is discussed.
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.
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.
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.
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.
118595197
Faint Resonantly Scattered Lyman Alpha Emission from the Absorption Troughs of Damped Lyman Alpha Systems at z ~ 3
We demonstrate that the Lyman alpha emission in the absorption troughs of a large sample of stacked damped Lyman alpha absorption systems (DLAS) presented by Rahmani et al (2010) is consistent with the spectral profiles and luminosities of a recently detected population of faint Lyman alpha emitters at z ~ 3. This result supports the suggestion that the faint emitters are to be identified with the host galaxies of DLAS at these redshifts.
17692963
The Detection of Oxygen in the Low-Density Intergalactic Medium
The abundances of metals in the intergalactic medium (IGM) can be used to constrain the amount of star formation at high redshift and the spectral shape of the ionizing background radiation. For both purposes, it is essential to measure the abundances in regions of low density, away from local sources of metals and ionizing photons. Here we report the first detection of O VI in the low-density IGM at high redshift. We perform a pixel-by-pixel search for O VI absorption in eight high-quality quasar spectra spanning the redshift range z = 2.0-4.5. At 2 z 3, we clearly detect O VI in the form of a positive correlation between the H I Lyα optical depth and the optical depth in the corresponding O VI pixel, down to τ ~ 10-1. This is an order of magnitude lower in τ than the best C IV measurements can probe, and it constitutes the first clear detection of metals in underdense gas. The nondetection of O VI at z > 3 is consistent with the enhanced photoionization from a hardening of the UV background below z ~ 3 but could also be caused by the high level of contamination from Lyman series lines.
16125751
First comparison of ionization and metallicity in two lines of sight toward HE 1104-1805 AB at z=1.66
Using new Nubble Space Telescope Faint Object Spectrograph, the New Technology Telescope ESO Multi Mode Instrument, and Keck HIRES spectra of the gravitationally lensed double QSO HE 1104-1805 AB (z(em) = 2.31) and assuming UV photoionization by a metagalactic radiation held, we derive physical conditions (ionization levels, metal abundances, and cloud sizes along the lines of sight) in five C IV + Mg II absorption systems clustered around z = 1.66 along the two lines of sight. Three of these systems are associated with a damped Ly alpha (DLA) system with log N(N I)= 20.85, which is observed in the UV spectra of the bright QSO image, A. The other two systems are associated with a Lyman-limit system with log N(H I)= 17.57 seen in the fainter image, B. The Cry and Mg II line profiles in A resemble those in the B spectra and span Delta v approximate to 360 km s(-1). The angular separation, theta = 3.195 ", between A and B corresponds to a transverse proper separation of S-perpendicular to = 8.3 h(50)(-1) kpc for q(0) = 0.5 and a lens at z = 1. Assuming that the relative metal abundances in these absorption systems are the same as those observed in the DLA system, we find that the observed N(C IV)/N(Mg II) ratios imply ionization parameters of log Gamma = -2.95 to - 2.35. Consequently, these clouds should be small (0.5-1.6 kpc with a hydrogen density of n(H) less than or similar to 0.01 cm(-3)) and relatively highly ionized. The absorption systems to B are found to have a metallicity 0.63 times lower than the metallicity of the gas giving rise to the DLA system, Z(DLA) similar or equal to 1/10 Z(circle dot). We detect O vr at z = 1.66253 in both QSO spectra but no associated N v. Our model calculations lead us to conclude that the C Iv clouds should be surrounded by large (similar to 100 kpc), highly ionized low-density clouds (n(H) similar to 10(-4) cm(-3)) in which O vr, but only weak C IV, absorption occurs. In this state, log Gamma greater than or equal to -1.2 reproduces the observed ratio of N(O vr)/N(N v)> 60. These results are discussed in view of the disk/halo and hierarchical structure formation models.
118217379
Small Scale Structure in the Universe and the Distribution of Baryons at High Redshift
We briefly discuss the relevance of Lyman alpha forest observations for measuring cosmological parameters, comparing the properties of high z QSO spectra with those of artifical spectra from hydrodynamic simulations, based on hierarchical cosmologies. In particular, we describe a measurement of the baryon content of the universe obtained by matching the average opacity of the Lyman alpha forest from simulations to the observed one from a new dataset observed with the Keck telescope. We then report on a search for possible small scale structure in the intergalactic medium which could be unresolved by current cosmological simulations. Observing column density gradients in the spectra of lensed QSOs we find the typical intergalactic gas cloud to be structureless down to at least the 4 % level, on scales of 0.1 kpc. Extending the study of lensed absorption to higher column densities we begin to sample the velocity field internal to high redshift galaxies. Remarkable differences in column density (of order 50 %) and projected velocity (tens of km/s) between lines of sight separated by only a few hundred parsecs are found, and we may be observing structure in the early interstellar medium.
8380751
The afterglow of GRB 050709 and the nature of the short-hard gamma-ray bursts.
The final chapter in the long-standing mystery of the gamma-ray bursts (GRBs) centres on the origin of the short-hard class of bursts, which are suspected on theoretical grounds to result from the coalescence of neutron-star or black-hole binary systems. Numerous searches for the afterglows of short-hard bursts have been made, galvanized by the revolution in our understanding of long-duration GRBs that followed the discovery in 1997 of their broadband (X-ray, optical and radio) afterglow emission. Here we present the discovery of the X-ray afterglow of a short-hard burst, GRB 050709, whose accurate position allows us to associate it unambiguously with a star-forming galaxy at redshift z = 0.160, and whose optical lightcurve definitively excludes a supernova association. Together with results from three other recent short-hard bursts, this suggests that short-hard bursts release much less energy than the long-duration GRBs. Models requiring young stellar populations, such as magnetars and collapsars, are ruled out, while coalescing degenerate binaries remain the most promising progenitor candidates.