In this report we review recent developments in perturbation theory methods for gauge theories. We present techniques and results that are useful in the calculation of cross sections for processes with many final state partons which have applications in the study of multi-jet phenomena in high-energy Colliders.

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The production cross section and distributions of the top quark are sensitive to new physics; e.g., the t i system can be a probe of new resonances or gauge bosons that are strongly coupled to the top quark, in analogy with Drell-Yan production. The existence of such new physics is expected in dynamical electroweak symmetry-breaking schemes, and associated with the large mass of the top quark. The total top quark production cross section can be more than doubled, and distributions significantly distorted with a chosen scale of new physics of -1 TeV in the vector color singlet or octet s channel. New resonance physics is most readily discernible in the high-pT distributions of the single top quark and of the W boson, and the mass distribution of the tipair. PACS numberh): 14.65. Ha, 13.85.Ni

We show how to observe sizable angular correlations between the decay products of the top quark and those of the anti-top quark in top quark pair production and decay at hadron colliders. These correlations result from the large asymmetry in the rate for producing like-spin versus unlike-spin top quark pairs provided the appropriate spin axes are used. The effects of new physics at production or decay on these correlations are briefly discussed.

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Abstract. We present a comprehensive review of keV-scale sterile neutrino Dark Matter, collecting views and insights from all disciplines involved -cosmology, astrophysics, nuclear, and particle physics -in each case viewed from both theoretical and experimental/observational perspectives. After reviewing the role of active neutrinos in particle physics, astrophysics, and cosmology, we focus on sterile neutrinos in the context of the Dark Matter puzzle. Here, we first review the physics motivation for sterile neutrino Dark Matter, based on challenges and tensions in purely cold Dark Matter scenarios. We then round out the discussion by critically summarizing all known constraints on sterile neutrino Dark Matter arising from astrophysical observations, laboratory experiments, and theoretical considerations. In this context, we provide a balanced discourse on the possibly positive signal from X-ray observations. Another focus of the paper concerns the construction of particle physics models, aiming to explain how sterile neutrinos of keV-scale masses could arise in concrete settings beyond the Standard Model of elementary particle physics. The paper ends with an extensive review of current and future astrophysical and laboratory searches, highlighting new ideas and their experimental challenges, as well as future perspectives for the discovery of sterile neutrinos.

As is well-known, comparison of the solar neutrino fluxes measured in SuperKamiokande (SK) by ν + e − → ν + e − and in the Sudbury Neutrino Observatory (SNO) by νe + d → e − + p + p can provide a "smoking gun" signature for neutrino oscillations as the solution to the solar neutrino puzzle. This occurs because SK has some sensitivity to all active neutrino flavors whereas SNO can isolate electron neutrinos. This comparison depends crucially on the normalization and uncertainty of the theoretical charged-current neutrino-deuteron cross section. We address a number of effects which are significant enough to change the interpretation of the SK-SNO comparison. 26.65.+t, 13.15.+g, 14.60.Pq Both SK and SNO are sensitive to solar neutrinos with energies above about 5 MeV. In SK, these are detected by ν +e − → ν +e − , with possible (indistinguishable) contributions from all active flavors. In particular, if there are ν e → ν µ , ν τ oscillations, then the latter contribute to the measured flux with a cross section 6-7 times smaller than for ν e . In SNO, on the other hand, the detection reaction ν e + d → e − + p + p can isolate the ν e flux. . This measured flux may or may not include a contribution from ν µ , ν τ (in any linear combination, since they interact via the neutral current). In an energy-independent (as suggested by the absence of any distortion in the SK recoil electron spectrum [2]) twoflavor oscillation scenario, there are two extreme cases [3]. First, for ν e → ν s , the ν e flux in these units is 0.45, and the undetectable ν s (sterile neutrino) flux is 0.55. Second, for ν e → ν µ , ν τ , the ν e flux is 0.34, and the ν µ , ν τ flux 0.66, so that the measured flux in SK is 0.34 + 0.66/6 = 0.45. In the first case, SNO will measure 0.45, and in the second case, 0.34. More generally, these arguments can be rephrased as a ratio to eliminate the SSM flux normalization and its ≃ 20% uncertainty, since the total incident flux is the same for both SK and SNO. Also, a small correction is necessary for the hep neutrinos [1,4] that add to the dominant 8 B neutrinos. This possible difference of 0.11 is small enough that the uncertainties must be scrutinized closely. Below, we closely follow the analogous results for the percent-level corrections to the theoreticalν e + p → e + + n cross section [5,6] that are necessary to achieve agreement with experiment [7].While results from SNO [8,9] have not yet been reported, they have said at conferences [10] that they expect their flux measurement uncertainty to be dominated by the ∼ 3% theoretical uncertainty [11,12] on the neutrino-deuteron cross section, at least eventually.In the SNO proposal [8], the uncertainty on the neutrino-deuteron cross sections was assumed to be about 10% (for comparison, the experimental measurements of neutrino-deuteron cross sections have uncertainties of 10 -40% [13]). Since that time, the calculations have been redone by a number of authors, with decreasing quoted uncertainties. The most refined recent calculations are those of Butler,...

We review the basic mechanisms of neutrino mass generation and the corresponding structure of the lepton mixing matrix. We summarize the status of three-neutrino oscillation parameters as determined from current observations, using state-of-the-art solar and atmospheric neutrino fluxes, as well as latest experimental data as of September 2007. We also comment on recent attempts to account for these results and to understand flavour from first principles. We discuss extensively the prospects for probing the strength of CP violation in two near term accelerator neutrino oscillation experiments, T2K and NOνA, as well as possible extensions such as T2KK and a second large off-axis detector near the NOνA detector. We also briefly discuss the possibility of probing the effect of Majorana phases in future neutrinoless double beta decay searches and discuss other implications of leptonic CP violation such as leptogenesis. Finally we comment on the issue of robustness of the current oscillation interpretation and possible ways of probing for non-standard neutrino interactions in precision oscillation studies.