pp̄ annihilation in an S-wave quark rearrangement model

The S-wave annihilation contribution to the pp? inelastic cross section at low energies is calculated in a quark-antiquark rearrangement model which includes the effect of NΔ̄ + N?Δ and ΔΔ̄ intermediate states. This mechanism, which leads automatically to a separable interaction, is able to account for about 15% of the observed cross section. The extension of the model to P-waves is also outlined.     

Charge symmetry breaking in np-->dpi(0)

The forward-backward asymmetry in np-->dpi(0), which must be zero in the center-of-mass system if charge symmetry is respected, has been measured to be [17.2+/-8.0(stat)+/-5.5(syst)]x10(-4), at an incident neutron energy of 279.5 MeV. This observable is compared to recent chiral effective field theory calculations, with implications regarding the du quark mass difference.     

Optimal multiqubit operations for Josephson charge qubits

We introduce a method for finding the required control parameters for a quantum computer that yields the desired quantum algorithm without invoking elementary gates. We concentrate on the Josephson charge-qubit model, but the scenario is readily extended to other physical realizations. Our strategy is to numerically find any desired double- or triple-qubit gate. The motivation is the need to significantly accelerate quantum algorithms in order to fight decoherence.     

Parity nonconservation in deuteron photoreactions

We calculate the asymmetries in parity-nonconserving deuteron photodisintegration due to circularly polarized photons $ \vec \gamma d \to np $ \vec \gamma d \to np with the photon laboratory energy ranging from the threshold up to 10MeV and the radiative capture of thermal polarized neutrons by protons $ \vec np \to \gamma d $ \vec np \to \gamma d . We use the leading-order electromagnetic Hamiltonian neglecting the smaller nuclear exchange currents. Comparative calculations are done by using the Reid93 and Argonne v₁₈ potentials for the strong interaction and the DDH and FCDH “best” values for the weak couplings in a weak one-meson exchange potential. A weak NΔ transition potential is used to incorporate also the Δ(1232) -isobar excitation in the coupled-channels formalism.     

Complex refractive index of turbid liquids

We present a multifunction spectrophotometer for the measurement of light reflection from thick and transmission from very thin turbid liquid samples. Moreover, we present a method to get the complex refractive index of such turbid liquids. As an example of the high performance of the device and the method, we present data on inks that are used in offset printing.     

Tests of charge symmetry in few-body systems

Tests of fundamental symmetries offer the promise of possibly unique insights into the nature of the strong interaction. We review the current status of selected experimental and theoretical investigations of charge symmetry in fewbody systems.     

The effect of resonances in 8Be on α-α bremsstrahlung

The effect of the quadrupole transition between the ⁸Be 4⁺(11.4 MeV) and 2⁺(2.9 MeV) states is included in low energy α-α bremsstrahlung (E_1ab < 30 MeV). In the equal-angle Harvard geometry this dominates for θ < 30°, and so enables an estimate to be made of B(E2, 4⁺ → 2⁺, ⁸Be). The problem of non-coplanarity is also discussed.     

Decoherence of flux qubits due to 1/f flux noise

We have investigated decoherence in Josephson-junction flux qubits. Based on the measurements of decoherence at various bias conditions, we discriminate contributions of different noise sources. We present a Gaussian decay function extracted from the echo signal as evidence of dephasing due to 1/f flux noise whose spectral density is evaluated to be about (10(-6)Phi0)2/Hz at 1 Hz. We also demonstrate that, at an optimal bias condition where the noise sources are well decoupled, the coherence observed in the echo measurement is limited mainly by energy relaxation of the qubit.