96477885
ZZ + jet production via gluon fusion at the LHC
A bstractPair production of Z bosons in association with a hard jet is an important background for new physics searches at the LHC. The loop-induced gluon-fusion process $ gg $ → ZZg contributes formally only at the next-to-next-to-leading order. Nevertheless, it can get enhanced by the large gluon flux at the LHC, and thus should be taken into account in relevant experimental searches. We provide the details and results of this calculation, which involves the manipulation of rank-5 pentagon integrals. Our results show that the gluon-fusion process can contribute more than 10% to the next-to-leading order QCD result and increases the overall scale uncertainty. Moreover, interference effects between Higgs and non-Higgs contributions can become large in phase-space regions where the Higgs is far off-shell.
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.
118581500
Measuring supersymmetry
If new physics is found at the LHC (and the ILC) the reconstruction of the underlying theory should not be biased by assumptions about high-scale models. For the mapping of many measurements onto high-dimensional parameter spaces we introduce SFitter with its new weighted Markov chain technique. SFitter constructs an exclusive likelihood map, determines the best-fitting parameter point and produces a ranked list of the most likely parameter points. Using the example of the TeV-scale supersymmetric Lagrangian we show how a high-dimensional likelihood map will generally include degeneracies and strong correlations. SFitter allows us to study such model-parameter spaces employing Bayesian as well as frequentist constructions. We illustrate in detail how it should be possible to analyze high-dimensional new-physics parameter spaces like the TeV-scale MSSM at the LHC. A combination of LHC and ILC measurements might well be able to completely cover highly complex TeV-scale parameter spaces.
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.
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.
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.
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.
59355894
Direct integration and non-perturbative effects in matrix models
We show how direct integration can be used to solve the closed amplitudes of multicut matrix models with polynomial potentials. In the case of the cubic matrix model, we give explicit expressions for the ring of nonholomorphic modular objects that are needed to express all closed matrix model amplitudes. This allows us to integrate the holomorphic anomaly equation up to holomorphic modular terms that we fix by the gap condition up to genus four. There is an onedimensional submanifold of the moduli space in which the spectral curve becomes the Seiberg-Witten curve and the ring reduces to the nonholomorphic modular ring of the group Γ(2). On that submanifold, the gap conditions completely fix the holomorphic ambiguity and the model can be solved explicitly to very high genus. We use these results to make precision tests of the connection between the large order behavior of the 1/N expansion and nonperturbative effects due to instantons. Finally, we argue that a full understanding of the large genus asymptotics in the multicut case requires a new class of nonperturbative sectors in the matrix model.
15226196
QSO Metal Absorption Systems at High Redshift and the Signature of Hierarchical Galaxy Formation
In a hierarchical cosmogony, galaxies build up by continuous merging of smaller structures. At z = 3, the matter content of a typical present-day galaxy is dispersed over several individual clumps embedded in sheetlike structures, often aligned along filaments. We have used hydrodynamical simulations to investigate the spatial distribution and absorption properties of metal-enriched gas in such regions of ongoing galaxy formation. The metal and hydrogen absorption features produced by the collapsing structures closely resemble observed QSO absorption systems over a wide range in H I column density. Strong C II and Si IV absorption occurs for lines of sight passing the densest regions close to the center of the protogalactic clumps, while C IV is a good tracer of the prominent filamentary structures and O VI becomes the strongest absorption feature for lines of sight passing through low-density regions far away from fully collapsed objects. The observed column density ratios of the different ionic species at z = 3 can be well reproduced if a mean metallicity [Z/H] = -2.5, relative abundances as found in metal-poor stars, a UV background with intensity J-22 = 3 at the Lyman limit, and either a power-law spectrum (J ∝ ν-1.5) or the spectral shape proposed by Haardt & Madau are assumed. The observed scatter in [C/H] is about a magnitude larger than that in the simulations, which suggests an inhomogeneous metal distribution. Observed and simulated Doppler parameter distributions of H I and C IV absorption lines are in good agreement, which indicates that shock heating due to gravitational collapse is a second important heating agent in addition to photoionization heating. The large velocity spreads seen in some C IV systems may be due to the occasional alignments of the observer's line of sight with expanding large-scale filaments. Both high-ionization multicomponent heavy-element absorbers and damped Lyα systems can arise from groups of moderately sized protogalactic clumps (Mbaryon ~ 109 M☉). Recent detections of star-forming galaxies at similar redshifts are consistent with this picture.
119165718
Wall-Crossing Holomorphic Anomaly and Mock Modularity of Multiple M5-Branes
Using wall-crossing formulae and the theory of mock modular forms we derive a holomorphic anomaly equation for the modified elliptic genus of two M5-branes wrapping a rigid divisor inside a Calabi–Yau manifold. The anomaly originates from restoring modularity of an indefinite theta-function capturing the wall-crossing of BPS invariants associated to D4-D2-D0 brane systems. We show the compatibility of this equation with anomaly equations previously observed in the context of $${{\mathcal{N}}=4}$$N=4 topological Yang–Mills theory on $${{\mathbbm{P}}^2}$$P2 and E-strings obtained from wrapping M5-branes on a del Pezzo surface. The non-holomorphic part is related to the contribution originating from bound-states of singly wrapped M5-branes on the divisor. We show in examples that the information provided by the anomaly is enough to compute the BPS degeneracies for certain charges. We further speculate on a natural extension of the anomaly to higher D4-brane charge.