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

Ordering multiple soft gluon emissions

We present an expression for the QCD amplitude for a general hard scattering process with any number of soft gluon emissions, to one-loop accuracy. The amplitude is written in two different but equivalent ways: as a product of operators ordered in dipole transverse momentum and as a product of loop-expanded currents. We hope that these results will help in the development of an all-orders algorithm for multiple emissions that includes the full colour structure and both the real and imaginary contributions to the amplitude.Comment: v4: 3 pages; 1 figure, 4 references and small clarifications added. Version accepted for publication in Physical Review Letter

Coulomb gluons and the ordering variable

We study in detail the exchange of a Coulomb (Glauber) gluon in the first few orders of QCD perturbation theory in order to shed light on their accounting to all orders. We find an elegant cancellation of graphs that imposes a precise ordering on the transverse momentum of the exchanged Coulomb gluon.Comment: 28 pages, 12 figure

On the breaking of collinear factorization in QCD

We investigate the breakdown of collinear factorization for non-inclusive observables in hadron-hadron collisions. For pure QCD processes, factorization is violated at the three-loop level and it has a structure identical to that encountered previously in the case of super-leading logarithms. In particular, it is driven by the non-commutation of Coulomb/Glauber gluon exchanges with other soft exchanges. Beyond QCD, factorization may be violated at the two-loop level provided that the hard subprocess contains matrix element contributions with phase differences between different colour topologies.Comment: Version 2: minor improvements for journal publicatio

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

The period gene encodes a predominantly nuclear protein in adult Drosophila

The period gene of Drosophila melanogaster (per) is important for the generation and maintenance of biological rhythms. Previous light microscopic observations indicated that per is expressed in a variety of tissues and cell types and suggested that the per protein (PER) may be present in different subcellular compartments. To understand how PER influences circadian rhythms, it is important to define its subcellular location, especially in adult flies where inducible promoter experiments suggested that it is most relevant to circadian locomotor activity rhythms. To this end, we report the results of an immunoelectron microscopic analysis of wild-type flies and per-beta- galactosidase (beta-gal) fusion gene transgenics using a polyclonal anti-PER antibody or an anti-beta-gal antibody, respectively. Most of the PER antigen and the fusion gene product were located within nuclei, suggesting that PER acts in that subcellular compartment to affect circadian rhythms. The results are discussed in terms of per's possible biochemical functions

Soft gluon evolution and non-global logarithms

We consider soft-gluon evolution at the amplitude level. Our evolution includes Coulomb exchanges and applies to generic hard-scattering processes involving any number of coloured partons. We emphasise the special role played by a Lorentz-invariant evolution variable, which coincides with the transverse momentum of the latest emission in a suitably defined dipole zero-momentum frame. We also relate the evolution algorithm, which was used originally in the derivation of super-leading logarithms, to renormalization group evolution equations that have been encountered recently. Handling large colour matrices presents the most significant challenge to numerical implementations and we present a means to expand systematically about the leading colour approximation.Comment: 34 pages, 6 figure

Increased Th2 activity and diminished skin barrier function cooperate in allergic skin inflammation

Atopic dermatitis (AD) is a chronic inflammatory skin disease induced by a complex interaction between susceptibility genes encoding skin barrier components and environmental allergen exposure that results in type 2 cytokine production. Although genetic lesions in either component can be risk factors for disease in patients, whether these pathways interact in the development of AD is not clear. To test this, we mated mice with T-cell specific expression of constitutively active Stat6 (Stat6VT) that spontaneously develop allergic skin inflammation with Flaky tail (Ft) mice that have mutations in Flg and Tmem79 genes that each affect skin barrier function. Our results demonstrate that over 90% of the Stat6VT transgenic mice carrying the Ft alleles (Stat6VTxFt−/−) develop severe atopic dermatitis lesions by 3-5 months of age, compared with only 40% of Stat6VT mice that develop disease by 6-7 months of age. Further, histopathological analysis of skin tissues from Stat6VTxFt−/− mice revealed extensive thickening of the dermis with increased inflammatory infiltrates as compared with Stat6VT mice. Our study suggests that skin barrier defects and altered Th2 responses independently cooperate in the pathogenesis of allergic skin inflammation, similar to effects observed in patients with AD