High quality 5ps pulse generation at 10 Gbit/s using a fibre Bragg grating compensated gain-switched laser diode

A fibre Bragg grating is designed to spectrally filter and perfectly compensate the chirped pulses from a gain-switched laser diode. This design is based on the exact characterisation of the intensity and phase profiles using an electro-optic pulse characterisation technique. This results in a compact pulse source that should produce high quality 5 ps duration pulses with a 50 dB pedestal suppression

Measurement of the Gluino Mass via Cascade Decays for SPS 1a

If R-parity conserving supersymmetry is realised with masses below the TeV scale, sparticles will be produced and decay in cascades at the LHC. In the case of a neutral LSP, which will not be detected, decay chains cannot be fully reconstructed, complicating the mass determination of the new particles. In this paper we extend the method of obtaining masses from kinematical endpoints to include a gluino at the head of a five-sparticle decay chain. This represents a non-trivial extension of the corresponding method for the squark decay chain. We calculate the endpoints of the new distributions and assess their applicability by examining the theoretical distributions for a variety of mass scenarios. The precision with which the gluino mass can be determined by this method is investigated for the mSUGRA point SPS 1a. Finally we estimate the improvement obtained from adding a Linear Collider measurement of the LSP mass.Comment: 40 pages; extended discussion of error

Measuring Pancharatnam's relative phase for SO(3) evolutions using spin polarimetry

In polarimetry, a superposition of internal quantal states is exposed to a single Hamiltonian and information about the evolution of the quantal states is inferred from projection measurements on the final superposition. In this framework, we here extend the polarimetric test of Pancharatnam's relative phase for spin$-{1/2}$ proposed by Wagh and Rakhecha [Phys. Lett. A {\bf 197}, 112 (1995)] to spin $j\geq 1$ undergoing noncyclic SO(3) evolution. We demonstrate that the output intensity for higher spin values is a polynomial function of the corresponding spin$-{1/2}$ intensity. We further propose a general method to extract the noncyclic SO(3) phase and visibility by rigid translation of two $\pi /2$ spin flippers. Polarimetry on higher spin states may in practice be done with spin polarized atomic beams.Comment: New title, minor corrections, journal reference adde

Invariant mass distributions in cascade decays

We derive analytical expressions for the shape of the invariant mass distributions of massless Standard Model endproducts in cascade decays involving massive New Physics (NP) particles, D -> Cc -> Bbc -> Aabc, where the final NP particle A in the cascade is unobserved and where two of the particles a, b, c may be indistinguishable. Knowledge of these expressions can improve the determination of NP parameters at the LHC. The shape formulas are composite, but contain nothing more complicated than logarithms of simple expressions. We study the effects of cuts, final state radiation and detector effects on the distributions through Monte Carlo simulations, using a supersymmetric model as an example. We also consider how one can deal with the width of NP particles and with combinatorics from the misidentification of final state particles. The possible mismeasurements of NP masses through `feet' in the distributions are discussed. Finally, we demonstrate how the effects of different spin configurations can be included in the distributions.Comment: 39 pages, 14 figures (colour), JHEP clas

Spin Measurements in Cascade Decays at the LHC

We systematically study the possibility of determining the spin of new particles after their discovery at the LHC. We concentrate on angular correlations in cascade decays. Motivated by constraints of electroweak precision tests and the potential of providing a Cold Dark Matter candidate, we focus on scenarios of new physics in which some discrete symmetry guarantees the existence of stable neutral particles which escape the detector. More specifically, we compare supersymmetry with another generic scenario in which new physics particles have the same spin as their Standard Model partners. A survey of possibilities of observing spin correlations in a broad range of decay channels is carried out, with interesting ones identified. Rather than confining ourselves to one "collider friendly" benchmark point (such as SPS1a), we describe the parameter region in which any particular decay channel is effective. We conduct a more detailed study of chargino's spin determination in the decay channel $\tilde{q}\to q + \tilde{C}^\pm \to q + W^\pm + LSP$. A scan over the chargino and neutralino masses is performed. We find that as long as the spectrum is not too degenerate the prospects for spin determination in this channel are rather good.Comment: 36 pages, references added, 1 figure modifie

Measurement of SUSY masses via cascade decays for SPS 1a

If R-parity conserving supersymmetry exists below the TeV-scale, new particles will be produced and decay in cascades at the LHC. The lightest supersymmetric particle will escape the detectors, thereby complicating the full reconstruction of the decay chains. In this paper we expand on existing methods for determining the masses of the particles in the cascade from endpoints of kinematical distributions. We perform scans in the mSUGRA parameter space to delimit the region where this method is applicable. From the examination of theoretical distributions for a wide selection of mass scenarios it is found that caution must be exerted when equating the theoretical endpoints with the experimentally obtainable ones. We provide analytic formulae for the masses in terms of the endpoints most readily available. Complications due to the composite nature of the endpoint expressions are discussed in relation to the detailed analysis of two points on the SPS 1a line. Finally we demonstrate how a Linear Collider measurement can improve dramatically on the precision of the masses obtained

Supersymmetry and Generic BSM Models in PYTHIA 8

We describe the implementation of supersymmetric models in PYTHIA 8, including production and decay of superparticles and allowing for violation of flavour, CP, and R-parity. We also present a framework for importing generic new-physics matrix elements into PYTHIA 8, in a way suitable for use with automated tools. We emphasize that this possibility should not be viewed as the only way to implement new-physics models in PYTHIA 8, but merely as an additional possibility on top of the already existing ones. Finally we address parton showers in exotic colour topologies, in particular ones involving colour epsilon tensors and colour sextets.Comment: 20 page

Defining and characterizing team resilience in elite sport

Objectives: The objectives of this study were to develop a definition of team resilience and to identify the resilient characteristics of elite sport teams. Design and Method: Focus groups consisting of a total of 31 participants were conducted with five elite teams from a range of sports. An interpretive thematic analysis using inductive and deductive reasoning was employed to analyze the data. Results and Conclusions: Team resilience was defined as a dynamic, psychosocial process which protects a group of individuals from the potential negative effect of the stressors they collectively encounter. It comprises of processes whereby team members use their individual and combined resources to positively adapt when experiencing adversity. Findings revealed four main resilient characteristics of elite sport teams: group structure, mastery approaches, social capital, and collective efficacy. This study extends resilience research in sport psychology by providing greater conceptual clarity of resilience at a team level. The implications of the findings for those conducting research in this area and for those consulting with elite sport teams are discussed

Advances in high power short pulse fiber laser systems and technology

We review recent advances in Yb fiber lasers and amplifiers for high power short pulse systems. We go on to describe associated recent developments in fiber components for use in such systems. Examples include microstructured optical fibers for pulse compression and supercontinuum generation, and advanced fiber grating technology for chirped-pulse amplifier systems

MgyNi1-y(Hx) thin films deposited by magnetron co-sputtering

In this work we have synthesised thin films of MgyNi1-y(Hx) metal and metal hydride with y between 0 and 1. The films are deposited by magnetron co-sputtering of metallic targets of Mg and Ni. Metallic MgyNi1-y films were deposited with pure Ar plasma while MgyNi1-yHx hydride films were deposited reactively with 30% H2 in the Ar plasma. The depositions were done with a fixed substrate carrier, producing films with a spatial gradient in the Mg and Ni composition. The combinatorial method of co-sputtering gives an insight into the phase diagram of MgyNi1-y and MgyNi1-yHx, and allows us to investigate structural, optical and electrical properties of the resulting alloys. Our results show that reactive sputtering gives direct deposition of metal hydride films, with high purity in the case of Mg~2NiH~4. We have observed limited oxidation after several months of exposure to ambient conditions. MgyNi1-y and MgyNi1-yHx films might be applied for optical control in smart windows, optical sensors and as a semiconducting material for photovoltaic solar cells