We study theoretically and experimentally a novel type of metamaterial with hybrid elements composed of twisted pairs of cross-shaped meta-atoms and their complements. We reveal that such two-layer metasurfaces demonstrate large, dispersionless optic
al activity at the transmission resonance accompanied by very low ellipticity. We develop a retrieval procedure to determine the effective material parameters for this structure, which has lower-order symmetry ($mathrm {C}_4$) than other commonly studied chiral structures. We verify our new theoretical approach by reproducing numerical and experimental scattering parameters.
Measurements of the coherence factors (R_Kpipi0 and R_K3pi) and the average strong-phase differences (delta^Kpipi0_D and delta^K3pi_D) for the decays D0-> K-pi+pi0 and D0->K-pi+pi+pi- are presented. These parameters are important inputs to the determ
ination of the unitarity triangle angle gamma in B+/- -> DK+/- decays, where D designates a D0 or D0bar meson decaying to a common final state. The measurements are made using quantum correlated DDbar decays collected by the CLEO-c experiment at the psi(3770) resonance, and augment a previously published analysis by the inclusion of new events in which the signal decay is tagged by the mode D-> K0Spi+pi-. The measurements also benefit from improved knowledge of external inputs, namely the D0D0bar mixing parameters, r_D^Kpi and several D-meson branching fractions. The measured values are R_Kpipi0 = 0.82 +- 0.07, delta_D^Kpipi0 = (164+20-14) deg., R_K3pi = 0.32+0.20-0.28 and delta^K3pi_D = (225+21_-78) deg. Consideration is given to how these measurements can be improved further by using the larger quantum-correlated data set collected by BESIII.
We propose and verify experimentally a new concept for achieving strong nonlinear coupling between the electromagnetic and elastic properties in metamaterials. This coupling is provided through a novel degree of freedom in metamaterial design: intern
al rotation within structural elements. Our meta-atoms have high sensitivity to electromagnetic wave power, and the elastic and electromagnetic properties can be independently designed to optimise the response. We demonstrate a rich range of nonlinear phenomena including self-tuning and bistability, and provide a comprehensive experimental demonstration of the predicted effects.
We introduce a chiral metamaterial with strong, non-resonant optical activity, and very low polarization ellipticity. We achieve this by combining a meta-atom and its complementary structure into a meta-molecule, resulting in the coupling of magnetic
and electric dipole responses. In contrast to either a pair of crosses, or complementary crosses, this structure has low dispersion in the optical activity at the transmission resonance. We also study the excitation mechanism in this structure, and optimize the optical activity through changing the twist angle.
We introduce the concept of controlling the nonlinear response of the metamaterial by altering its internal structure. We experimentally demonstrate tuning of the nonlinear response of two coupled split-ring resonators by changing their mutual positi
on. This effect is achieved through modification of the structure of the coupled resonant modes, and their interaction with the incident field. By offsetting the resonators we control the maximum currents through the nonlinear driving elements, which affects the nonlinear response of the system.
We present the first search for the decay $D^+_{s}to omega e^{+} u$ to test the four-quark content of the $D^+_{s}$ and the $omega$-$phi$ mixing model for this decay. We use 586 $mathrm{pb}^{-1}$ of $e^{+}e^{-}$ collision data collected at a center-o
f-mass energy of 4170 MeV. We find no evidence of a signal, and set an upper limit on the branching fraction of $mathcal{B}(D^+_{s}toomega e^+ u)<$0.20% at the 90% confidence level.
We experimentally observe the tuning of metamaterials through the relative rotation of the elements about their common axis. In contrast to previous results we observe a crossing of resonances, where the symmetric and anti-symmetric modes become dege
nerate. We associate this effect with an interplay between the magnetic and electric near-field interactions and verify this by calculations based on the interaction energy between resonators.
We present projections for reconstruction of the inflationary potential expected from ESAs upcoming Planck Surveyor CMB mission. We focus on the effects that tensor perturbations and the presence of non-Gaussianities have on reconstruction efforts in
the context of non-canonical inflation models. We consider potential constraints for different combinations of detection/null-detection of tensors and non-Gaussianities. We perform Markov Chain Monte Carlo and flow analyses on a simulated Planck-precision data set to obtain constraints. We find that a failure to detect non-Gaussianities precludes a successful inversion of the primordial power spectrum, greatly affecting uncertainties, even in the presence of a tensor detection. In the absence of a tensor detection, while unable to determine the energy scale of inflation, an observable level of non-Gaussianities provides correlations between the errors of the potential parameters, suggesting that constraints might be improved for suitable combinations of parameters. Constraints are optimized for a positive detection of both tensors and non-Gaussianities.
