Survival before annihilation in Psi-prime decays

We extend the simple scenario for $\Psi'$ decays suggested a few years ago. The $c\bar c$ pair in the $\Psi'$ does not annihilate directly into three gluons but rather survives before annihilating. An interesting prediction is that a large fraction of all $\Psi'$ decays could originate from the $\Psi' \to \eta_{c} (3\pi)$ channel which we urge experimentalists to identify. Our model solves the problem of the apparent hadronic excess in $\Psi'$ decays as well as the $\rho\pi$ puzzle since, in our view, the two-body decays of the $\Psi'$ are naturally of electromagnetic origin. Further tests of this picture are proposed, e.g. $J/\Psi \to b_{1}\eta$.Comment: 6 pages, no figur

Characters of the W3 algebra

Traces of powers of the zero mode in the W3 Algebra have recently been found to be of interest, for example in relation to Black Hole thermodynamics, and arise as the terms in an expansion of the full characters of the algebra. We calculate the first few such powers in two cases. Firstly, we find the traces in the 3-state Potts model by using null vectors to derive modular differential equations for the traces. Secondly, we calculate the exact results for Verma module representations. We compare our two methods with each other and the result of brute-force diagonalisation for low levels and find complete agreement.Comment: v2: Numerous small changes, version to appear in JHEP, 22 pages. v3: Typos corrected, matches published version, 22 page

Hadronic Phases and Isospin Amplitudes in D(B)→ππD(B) \to \pi \pi and D(B)→KKˉD(B) \to K \bar K Decays

Hadronic phase in $\pi \pi$ and $K \bar K$ channels are calculated a la Regge. At the D mass one finds $\delta_{\pi \pi} \approx \pi/3$ and $\delta_{K \bar K} \approx -\pi/6$ in good agreement with the CLEO data while at the B mass these angles are predicted to be, respectively, $11^\circ$ and $-7^\circ$. With the hadronic phase $e^{i \delta_{K \bar K}}$ taken into account, a quark diagram decomposition of the isospin invariant amplitudes in $D \to K \bar K$ decays fits the data provided the exchange diagram contribution is about 1/3 of the tree level one.Comment: 10pages,late

Controlling the dynamics of a coupled atom-cavity system by pure dephasing : basics and potential applications in nanophotonics

The influence of pure dephasing on the dynamics of the coupling between a two-level atom and a cavity mode is systematically addressed. We have derived an effective atom-cavity coupling rate that is shown to be a key parameter in the physics of the problem, allowing to generalize the known expression for the Purcell factor to the case of broad emitters, and to define strategies to optimize the performances of broad emitters-based single photon sources. Moreover, pure dephasing is shown to be able to restore lasing in presence of detuning, a further demonstration that decoherence can be seen as a fundamental resource in solid-state cavity quantum electrodynamics, offering appealing perspectives in the context of advanced nano-photonic devices.Comment: 10 pages, 7 figure

Electric field sensing with a scanning fiber-coupled quantum dot

We demonstrate the application of a fiber-coupled quantum-dot-in-a-tip as a probe for scanning electric field microscopy. We map the out-of-plane component of the electric field induced by a pair of electrodes by measurement of the quantum-confined Stark effect induced on a quantum dot spectral line. Our results are in agreement with finite element simulations of the experiment. Furthermore, we present results from analytic calculations and simulations which are relevant to any electric field sensor embedded in a dielectric tip. In particular, we highlight the impact of the tip geometry on both the resolution and sensitivity.Comment: 10 pages, 4 figure

Final State Interaction Phases in B→Kπ B \to K \pi Decay Amplitudes

A simple Regge pole model for $K\pi$ scattering explains the large $e^{i \delta}$ between isospin amplitudes which is observed at the D meson mass ($\delta \approx \pi/2$). It predicts $\delta \approx 14^{\circ}- 20^{\circ}$ at the B mass. Implications for ($B \to K \pi$) decays and extensions of the model to other two-body decay channels are briefly discussed.Comment: 8pages,late

Phases and Amplitudes in Inclusive Ψ\Psi and Ψ′\Psi' Decays

In inclusive decays of the $\Psi$ (3097), electromagnetic and gluonic annihilation amplitudes add incoherently, namely they are 90$^\circ$ out of phase. We argue that this incoherence must persist in each exclusive decay channel. For inclusive $\Psi'$ (3686) decays, we suggest the absence of a significant direct annihilation amplitude into three gluons and propose a new amplitude via QCD anomalies and the $h_c$ (3526) off shell. Phenomenological implications for exclusive decay channels are pointed out.Comment: 10 page

Trace anomalies and the ΔI=1/2\Delta I = 1/2 rule

Trace Anomaly Dominance in weak $K$-decays successfully reproduces the $\Delta I = {1\over 2}$ selection rule results, as observed in $K_S \to \pi\pi, K_L \to \pi\pi\pi, K_S \to \gamma\gamma$ and $K_L \to \pi^0 \gamma\gamma$.Comment: 10 pages, no figur

Monitoring stimulated emission at the single photon level in one-dimensional atoms

We theoretically investigate signatures of stimulated emission at the single photon level for a two-level atom interacting with a one-dimensional light field. We consider the transient regime where the atom is initially excited, and the steady state regime where the atom is continuously driven with an external pump. The influence of pure dephasing is studied, clearly showing that these effects can be evidenced with state of the art solid state devices. We finally propose a scheme to demonstrate the stimulation of one optical transition by monitoring another one, in three-level one-dimensional atoms.Comment: 4 pages, 4 figures. Improved introduction; Comments adde