Precise Predictions for Higgs Production in Neutralino Decays in the Complex MSSM

Complete one-loop results are obtained for the class of processes chi^0_i->chi^0_j h_a in the MSSM where all parameters entering this process beyond lowest order are allowed to have arbitrary CP-violating phases. An on-shell renormalisation scheme is worked out for the chargino-neutralino sector that properly takes account of imaginary parts arising from complex parameters and from absorptive parts of loop integrals. The genuine vertex contributions to the neutralino decay amplitudes are combined with two-loop propagator-type corrections for the outgoing Higgs boson. In this way the currently most precise prediction for this class of processes is obtained. The numerical impact of the genuine vertex corrections is studied for several examples of CP-conserving and CP-violating scenarios. We find that significant effects on the decay widths and branching ratios are possible even in the CP-conserving MSSM. In the CP-violating CPX benchmark scenario the corrections to the decay width are found to be particularly large, namely, of order 45% for a Higgs mass of 40 GeV. This parameter region of the CPX scenario where a very light Higgs boson is unexcluded by present data is analysed in detail. We find that in this parameter region, which will be difficult to cover by standard Higgs search channels at the LHC, the branching ratio for the decay chi^0_2->chi^0_1 h_1 is large. This may offer good prospects to detect such a light Higgs boson in cascade decays of supersymmetric particles.Comment: 24 pages, 6 figure

The Real Corrections to the Gamma* Impact Factor: First Numerical Results

We have performed analytically the transverse momentum integrations in the real corrections to the longitudinal \gamma^*_L impact factor and carried out numerically the remaining integrations. I outline the analytical integration and present the numerical results: we have performed a numerical test and computed those parts of the impact factor that depend upon the energy scale s_0.Comment: 4 pages, 3 figures, to appear in proceedings of "DIS 2004", XII International Workshop on Deep Inelastic Scattering (April 2004, Strbske Pleso, Slovakia

Gaps between Jets in the High Energy Limit

We use perturbative QCD to calculate the parton level cross section for the production of two jets that are far apart in rapidity, subject to a limitation on the total transverse momentum Q0 in the interjet region. We specifically address the question of how to combine the approach which sums all leading logarithms in Q/Q0 (where Q is the jet transverse momentum) with the BFKL approach, in which leading logarithms of the scattering energy are summed. This paper constitutes progress towards the simultaneous summation of all important logarithms. Using an "all orders" matching, we are able to obtain results for the cross section which correctly reproduce the two approaches in the appropriate limits.Comment: 29 pages, 9 figures, minor corrections to text and improved figure

Evolution of crack-bridging and crack-tip driving force during the growth of a fatigue crack in a Ti/SiC composite

High spatial resolution diffraction and imaging using synchrotron X-rays are combined to monitor the incremental growth of a fatigue crack through the matrix of a Ti-6Al-4V/SCS-6 SiC monofilament metal matrix composite. X-ray tomography is used to quantify the crack opening displacement (COD) and diffraction to measure the crack-tip stress field in each phase, the wear degraded interfacial strengths, as well as the crack face tractions applied by the bridging fibres, at maximum () and minimum () loading as a function of crack length. In this way, it has been possible to quantify the crack-tip driving force (the stress intensity range effective at the crack-tip) in three ways: from the COD, the bridging stresses and the crack-tip stress field. The fibre stresses act to prop open the crack atand shield the crack atsuch that the change in COD is small over the fatigue cycle. Consequently, the effective stress intensity range at the crack tip remains around 10 MPa√m as the crack lengthens, as more and more fibres bridge the crack despite the normally applied stress intensity rising to 60 MPa√m. The implications of the derived fracture mechanics parameters are assessed and the wider potential of X-ray diffraction and imaging for crack-tip microscopy is discussed.</jats:p

OPTIMISATION OF CRITICALITY AND BURNUP CALCULATIONS IN MONK

The primary goal of this paper is to increase the efficiency of criticality and burnup calculations in the ANSWERS MONK® Monte Carlo code [1]. Two ways of achieving this goal are investigated as part of the H2020 McSAFE Project: creating a unified energy grid for all materials in the model, and reducing the spread in variances of fluxes for depletable materials using a generated optimised importance map. The average tracking speedup factor across all cycles of all burnup calculations ran using the unified energy grid, at base temperature, was found to be 1.96. For criticality calculations at 400K with runtime Doppler broadening, the unified grid approach gave a total speedup factor of 7.32. This demonstrates the potential importance of this method to reduce the calculation time with models with runtime Doppler broadening. The use of the generated optimised importance map has been demonstrated to significantly reduce the variance in the standard deviations on the fluxes in the fuel pins across two different test cases. If a solution is required in which the standard deviation in none of the fuel pins exceeds 5% it was found that the number of scoring stages required was more than halved, highlighting the potential for the outlined methodology to speedup burnup credit calculations

OPTIMISATION OF CRITICALITY AND BURNUP CALCULATIONS IN MONK®

The primary goal of this paper is to increase the efficiency of criticality and burnup calculations in the ANSWERS MONK® Monte Carlo code [1]. Two ways of achieving this goal are investigated as part of the H2020 McSAFE Project: creating a unified energy grid for all materials in the model, and reducing the spread in variances of fluxes for depletable materials using a generated optimised importance map. The average tracking speedup factor across all cycles of all burnup calculations ran using the unified energy grid, at base temperature, was found to be 1.96. For criticality calculations at 400K with runtime Doppler broadening, the unified grid approach gave a total speedup factor of 7.32. This demonstrates the potential importance of this method to reduce the calculation time with models with runtime Doppler broadening. The use of the generated optimised importance map has been demonstrated to significantly reduce the variance in the standard deviations on the fluxes in the fuel pins across two different test cases. If a solution is required in which the standard deviation in none of the fuel pins exceeds 5% it was found that the number of scoring stages required was more than halved, highlighting the potential for the outlined methodology to speedup burnup credit calculations