Interpretation of Higgs and SUSY searches in MSUGRA and GMSB models

Higgs and SUSY searches performed by the ALEPH experiment at LEP are interpreted in the framework of two constrained R-parity conserving models: minimal supergravity and minimal gauge mediated supersymmetry breaking. (4 refs)

Higgs limits in the MSSM: beyond the benchmark

Up to now, the ALEPH limits on the MSSM neutral Higgs boson masses have been reported for specific sets of model parameters corresponding to the so-called minimal and maximal mixing configurations. An investigation of the robustness of these results is performed by means of a scan of the parameter space in which more than 30 million sets of m_0, m_1/2, mu, A_t, m_A and tan(beta) values are probed. In the low tan(beta) regime, the m_h limit obtained in the cases of minimal and maximal mixing is found to remain valid for 99.991341f the parameter sets explored. In the case of large tan(beta), and considering the limit on m_h + m_A, this fraction reduces to 99.

Search for Light Higgs Boson in the Yukawa process

The Yukawa process e+e- --> f fbar h/A, where f is a tau lepton or a b quark, is used to search for light scalar or pseudoscalar Higgs bosons in the framework of general two-Higgs-doublet models. The analysis is based on the data sample collected by the ALEPH experiment at LEP at centre-of-mass energies at and around the Z peak. Since no deviation from the standard model expectations has been observed in the data, this search results in a new 95 excluded region of the (mA, tan beta) plane in any two-Higgs-doublet model

Optimal use of time dependent probability density data to extract potential energy surfaces

A novel algorithm was recently presented to utilize emerging time dependent probability density data to extract molecular potential energy surfaces. This paper builds on the previous work and seeks to enhance the capabilities of the extraction algorithm: An improved method of removing the generally ill-posed nature of the inverse problem is introduced via an extended Tikhonov regularization and methods for choosing the optimal regularization parameters are discussed. Several ways to incorporate multiple data sets are investigated, including the means to optimally combine data from many experiments exploring different portions of the potential. Results are presented on the stability of the inversion procedure, including the optimal combination scheme, under the influence of data noise. The method is applied to the simulated inversion of a double well system.Comment: 34 pages, 5 figures, LaTeX with REVTeX and Graphicx-Package; submitted to PhysRevA; several descriptions and explanations extended in Sec. I

Subfemtosecond steering of hydrocarbon deprotonation through superposition of vibrational modes

Subfemtosecond control of the breaking and making of chemical bonds in polyatomic molecules is poised to open new pathways for the laser-driven synthesis of chemical products. The break-up of the C-H bond in hydrocarbons is an ubiquitous process during laser-induced dissociation. While the yield of the deprotonation of hydrocarbons has been successfully manipulated in recent studies, full control of the reaction would also require a directional control (that is, which C-H bond is broken). Here, we demonstrate steering of deprotonation from symmetric acetylene molecules on subfemtosecond timescales before the break-up of the molecular dication. On the basis of quantum mechanical calculations, the experimental results are interpreted in terms of a novel subfemtosecond control mechanism involving non-resonant excitation and superposition of vibrational degrees of freedom. This mechanism permits control over the directionality of chemical reactions via vibrational excitation on timescales defined by the subcycle evolution of the laser waveform

The importance of Rydberg orbitals in dissociative ionization of small hydrocarbon molecules in intense laser fields

Much of our intuition about strong-field processes is built upon studies of diatomic molecules, which typically have electronic states that are relatively well separated in energy. In polyatomic molecules, however, the electronic states are closer together, leading to more complex interactions. A combined experimental and theoretical investigation of strong-field ionization followed by hydrogen elimination in the hydrocarbon series C2D2, C2D4 and C2D6 reveals that the photofragment angular distributions can only be understood when the field-dressed orbitals rather than the field-free orbitals are considered. Our measured angular distributions and intensity dependence show that these field-dressed orbitals can have strong Rydberg character for certain orientations of the molecule relative to the laser polarization and that they may contribute significantly to the hydrogen elimination dissociative ionization yield. These findings suggest that Rydberg contributions to field-dressed orbitals should be routinely considered when studying polyatomic molecules in intense laser fields

Metamaterial-Enhanced Nonlinear Terahertz Spectroscopy

We demonstrate large nonlinear terahertz responses in the gaps of metamaterial split ring resonators in several materials and use nonlinear THz transmission and THz-pump/THz-probe spectroscopy to study the nonlinear responses and dynamics. We use the field enhancement in the SRR gaps to initiate high-field phenomena at lower incident fields. In vanadium dioxide, we drive the insulator-to-metal phase transition with high-field THz radiation. The film conductivity increases by over two orders of magnitude and the phase transition occurs on a several picosecond timescale. In gallium arsenide, we observe high-field transport phenomena, including mobility saturation and impact ionization. The carrier density increases by up to ten orders of magnitude at high fields. At the highest fields, we demonstrate THz-induced damage in both vanadium dioxide and gallium arsenide.United States. Dept. of Energy (DOE-BES, grant DE-FG02- 09ER46643)United States. Office of Naval Research (ONR Grant No. N00014-09-1-1103