118389357
Precision Measurements of Higgs Couplings: Implications for New Physics Scales
The measured properties of the recently discovered Higgs boson are in good agreement with predictions from the Standard Model. However, small deviations in the Higgs couplings may manifest themselves once the currently large uncertainties will be improved as part of the LHC program and at a future Higgs factory. We review typical new physics scenarios that lead to observable modications of the Higgs interactions. They can be divided into two broad categories: mixing eects as in portal models or extended Higgs sectors, and vertex loop eects from new matter or gauge elds. In each model we relate coupling deviations to their eective new physics scale. It turns out that with percent level precision the Higgs couplings will be sensitive to the multi-TeV regime.
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.
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.
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.
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.
116980402
Omega (baryon) and the geometry of intermediate redshift Lyman alpha absorption systems
Estimates of Omega_baryon from primordial nucleosynthesis together with standard assumptions about the ionization state of low column density Lyman alpha forest clouds can be used to determine an upper limit for the cloud thickness along the line of sight. This upper limit provides significant constraints on the axis ratio of the absorbers and on the overall fraction of the baryonic matter contained in these objects if the recently measured large values for their transversal size are representative. The absorbers have to be considerably flattened structures and may possibly contain a substantial fraction of the baryonic matter at high redshift.
119354809
Small-Scale Structure at High Redshift. II. Physical Properties of the C IV Absorbing Clouds
Keck HIRES spectra with a resolution of 6.6 or 4.3 km s-1 were obtained of the separate images of three gravitationally lensed QSOs, namely, Q0142-0959 A,B (UM 673 A,B; zem = 2.72), HE 1104-1805 A,B (zem = 2.32), and Q1422+231 A,C (zem = 3.62). The typical separation of the images on the sky is ~1''. The corresponding transverse distances between the lines of sight range from a few tens of kiloparsecs at the redshift of the lens to a few parsecs at the source. We studied the velocity differences and column density differences in C IV doublets in each QSO, including single isolated doublets, complex clumps of doublets, and subclumps. Unlike the low-ionization gas clouds typical of the interstellar gas in the Galaxy or damped Lyα galaxies, the spatial density distribution of C IV absorbing gas clouds turns out to be mostly featureless on scales up to a few hundred parsecs, with column density differences rising to 50% or more over separations beyond a few kiloparsecs. Similarly, velocity shear becomes detectable only over distances larger than a few hundred parsecs, rising to ~70 km s-1 at a few kiloparsecs. The absorption systems become more coherent with decreasing redshift distance to the background QSO; this finding confirms that all three QSOs used are indeed lensed, as opposed to being genuine QSO pairs. The amount of turbulence in C IV gas along and across each line of sight was measured and a crude estimate of the energy input rate obtained. The energy transmitted to the gas is substantially less than in present-day star-forming regions, and the gas is less turbulent on a given spatial scale than, e.g., local H II regions. The quiescence of C IV clouds, taken with their probable low density, implies that these objects are not internal to galaxies. The C IV absorbers could be gas expelled recently to large radii and raining back onto its parent galaxy, or pre-enriched gas from an earlier (Population III?) episode of star formation, falling into the nearest mass concentration. However, while the metals in the gas may have been formed at higher redshifts (z > 5?), the residual turbulence in the clouds and the minimum coherence length measured here imply that the gas was stirred more recently, possibly by star formation events recurring on a timescale on the order of 107-108 yr.
124794055
The Z(abs) approximately Z(cm) approximately 2 QSO absorption line systems: Evidence for abundances in excess of solar
16974679
A Population of Faint Extended Line Emitters and the Host Galaxies of Optically Thick QSO Absorption Systems
We have conducted a long-slit search for low surface brightness Lyα emitters at redshift 2.67 < z < 3.75. A 92 hr long exposure with the ESO VLT FORS2 instrument down to a 1σ surface brightness detection limit of 8 × 10^(−20) erg cm^(−2) s^(−1) arcsec^(−2) per arcsec^2 aperture yielded a sample of 27 single line emitters with fluxes of a few × 10^(−18) erg s^(−1) cm^(−2). We present arguments that most objects are indeed Lyα. The large comoving number density, 3 × 10^(−2) h^3_(70) Mpc^(−3), the large covering factor, dN/dz ~ 0.2–1, and the often extended Lyα emission suggest that the emitters can be identified with the elusive host population of damped Lyα systems (DLAS) and high column density Lyman limit systems (LLS). A small inferred star formation rate, perhaps supplemented by cooling radiation, appears to energetically dominate the Lyα emission, and is consistent with the low metallicity, low dust content, and theoretically inferred low masses of DLAS, and with the relative lack of success of earlier searches for their optical counterparts. Some of the line profiles show evidence for radiative transfer in galactic outflows. Stacking surface brightness profiles, we find emission out to at least 4". The centrally concentrated emission of most objects appears to light up the outskirts of the emitters (where LLS arise) down to a column density where the conversion from UV to Lyα photon becomes inefficient. DLAS, high column density LLS, and the emitter population discovered in this survey appear to be different observational manifestations of the same low-mass, protogalactic building blocks of present-day L_* galaxies.
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.