Singlet-triplet transitions in highly correlated nanowire quantum dots

We consider a quantum dot embedded in a three-dimensional nanowire with tunable aspect ratio a. A configuration interaction theory is developed to calculate the energy spectra of the finite 1D quantum dot systems charged with two electrons in the presence of magnetic fields B along the wire axis. Fruitful singlet-triplet transition behaviors are revealed and explained in terms of the competing exchange interaction, correlation interaction, and spin Zeeman energy. In the high aspect ratio regime, the singlet-triplet transitions are shown designable by tuning the parameters a and B. The transitions also manifest the highly correlated nature of long nanowire quantum dots.Comment: 4 pages, 4 figure

Is DsJ+(2632)D^{+}_{sJ}(2632) the first radial excitation of Ds∗(2112)D_{s}^{*}(2112)?

We present a quantitative analysis of the $D^{+}_{sJ}(2632)$ observed by SELEX mainly focusing on the assumption that $D^{+}_{sJ}(2632)$ is the first radial excitation of the $1^{-}$ ground state $D^{*}_{s}(2112)$. By solving the instantaneous Bethe-Salpeter equation, we obtain the mass $2658\pm 15$ MeV for the first excited state, which is about 26 MeV heavier than the experimental value $2632\pm 1.7$ MeV. By means of PCAC and low-energy theorem we calculate the transition matrix elements and obtain the decay widths: $\Gamma(D^{+}_{sJ}\to D^{+}_s\eta)=4.07\pm 0.34$ MeV, $\Gamma(D^{+}_{sJ}\to D^{0}K^{+}) \simeq \Gamma(\Gamma(D^{+}_{sJ}\to D^{+}K^{0})=8.9\pm 1.2$ MeV, and the ratio $\Gamma(D^{+}_{sJ}\to D^{0}K^{+})/\Gamma(D^{+}_{sJ}\to D^{+}_{s}\eta)=2.2\pm 0.2$ as well. This ratio is quite different from the SELEX data $0.14\pm 0.06$. The summed decay width of those three channels is approximately 21.7 MeV, already larger than the observed bound for the full width ($\leq 17$ MeV). Furthermore, assuming $D_{sJ}^+(2632)$ is $1^{-}$ state, we also explore the possibility of $S-D$ wave mixing to explain the SELEX observation. Based on our analysis, we suspect that it is too early to conclude that $D^{+}_{sJ}(2632)$ is the first radial excitation of the $1^{-}$ ground state $D^{*}_{s}(2112)$. More precise measurements of the relative ratios and the total decay width are urgently required especially for $S-D$ wave mixing.Comment: 12 pages, 8 figure

Control of ionic selectivity by a pore helix residue in the Kv1.2 channel

Interaction between the selectivity filter and the adjacent pore helix of voltage-gated K+ (Kv) channels controls pore stability during K+ conduction. Kv channels, having their selectivity filter destabilized during depolarization, are said to undergo C-type inactivation. We examined the functionality of a residue at the pore helix of the Kv1.2 channel (V370), which reportedly affects C-type inactivation. A mutation into glycine (V370G) caused a shift in reversal potential from around -72 to -9 mV. The permeability ratios (P-Na/P-K) of the wild type and V370G mutant are 0.04 and 0.76, respectively. In the wild-type, P-Rb/P-K, P-Cs/P-K and P-Li/P-K are 0.78, 0.10 and 0.05, respectively. Kv1.2 V370G channels had enhanced permeability to Rb+ and Cs+ (P-Rb/P-K and P-Cs/P-K are 1.63 and 1.18, respectively); however, Li+ permeability was not significantly augmented (P-Li/P-K is 0.13). Therefore, in addition to its known effect on pore stability, V370 of Kv1.2 is also crucial in controlling ion selectivity

CP violation in B→φKs in a model III two Higgs doublet model

The mixing induced time dependent CP asymmetry, direct CP asymmetry, and branching ratio in B→φKs in a model III 2HDM are calculated, in particular, neutral Higgs boson contributions are included. It is shown that satisfying all the relevant experimental constraints, for time dependent CP asymmetry SφK the model III can agree with the present data, Sφk = −0.39±0.41, within the 1σ error, and the direct CP asymmetry which is zero in SM can be about −8% ∼ −20% in the reasonable regions of parameters

Supersymmetric CP Violation in B→Xsl+l−B \to X_s l^+ l^- in Minimal Supergravity Model

Direct CP asymmetries and the CP violating normal polarization of lepton in inclusive decay B \to X_s l^+ l^- are investigated in minimal supergravity model with CP violating phases. The contributions coming from exchanging neutral Higgs bosons are included. It is shown that the direct CP violation in branching ratio, A_{CP}^1, is of {\cal{O}}(10^{-3}) for l=e, \mu, \tau. The CP violating normal polarization for l=\mu can reach 0.5 percent when tan\beta is large (say, 36). For l=\tau and in the case of large \tan\beta, the direct CP violation in backward-forward asymmetry, A_{CP}^2, can reach one percent, the normal polarization of \tau can be as large as a few percent, and both are sensitive to the two CP violating phases, \phi_\mu and \phi_{A_0}, and consequently it could be possible to observe them (in particular, the normal polarization of \tau) in the future B factories.Comment: 14 pages, latex, 5 figure

Exclusive semileptonic rare decays B−>(B ->_ (K,K^*) \ell^+ \ell^- in supersymmetric theories

The invariant mass spectrum, forward-backward asymmetry, and lepton polarizations of the exclusive processes $B\to K(K^*)\ell^+ \ell^-, \ell=\mu, \tau$ are analyzed under supersymmetric context. Special attention is paid to the effects of neutral Higgs bosons (NHBs). Our analysis shows that the branching ratio of the process \bkm can be quite largely modified by the effects of neutral Higgs bosons and the forward-backward asymmetry would not vanish. For the process \bksm, the lepton transverse polarization is quite sensitive to the effects of NHBs, while the invariant mass spectrum, forward-backward asymmetry, and lepton longitudinal polarization are not. For both \bkt and \bkst, the effects of NHBs are quite significant. The partial decay widths of these processes are also analyzed, and our analysis manifest that even taking into account the theoretical uncertainties in calculating weak form factors, the effects of NHBs could make SUSY shown up.Comment: Several references are added, typo are correcte

Charm multiplicity and the branching ratios of inclusive charmless b quark decays in the general two-Higgs-doublet models

In the framework of general two-Higgs-doublet models, we calculate the branching ratios of various inclusive charmless b decays by using the low energy effective Hamiltonian including next-to-leading order QCD corrections, and examine the current status and the new physics effects on the determination of the charm multiplicity $n_c$ and semileptonic branching ratio $B_{SL}$. Within the considered parameter space, the enhancement to the ratio $BR(b \to s g)$ due to the charged-Higgs penguins can be as large as a factor of 8 (3) in the model III (II), while the ratio $BR(b \to no charm)$ can be increased from the standard model prediction of 2.49% to 4.91% (2.99%) in the model III (II). Consequently, the value of $B_{SL}$ and $n_c$ can be decreased simultaneously in the model III. The central value of $B_{SL}$ will be lowered slightly by about 0.003, but the ratio $n_c$ can be reduced significantly from the theoretical prediction of $n_c= 1.28 \pm 0.05$ in the SM to $n_c= 1.23 \pm 0.05$, $1.18 \pm 0.05$ for $m_{H^+}=200, 100$ GeV, respectively. We find that the predicted $n_c$ and the measured $n_c$ now agree within roughly one standard deviation after taking into account the effects of gluonic charged Higgs penguins in the model III with a relatively light charged Higgs boson.Comment: 25 pages, Latex file, axodraw.sty, 6 figures. Final version to be published in Phys.Rev.

Renormalization Group Running of Lepton Mixing Parameters in See-Saw Models with S4S_4 Flavor Symmetry

We study the renormalization group running of the tri-bimaximal mixing predicted by the two typical $S_4$ flavor models at leading order. Although the textures of the mass matrices are completely different, the evolution of neutrino mass and mixing parameters is found to display approximately the same pattern. For both normal hierarchy and inverted hierarchy spectrum, the quantum corrections to both atmospheric and reactor neutrino mixing angles are so small that they can be neglected. The evolution of the solar mixing angle $\theta_{12}$ depends on $\tan\beta$ and neutrino mass spectrum, the deviation from its tri-bimaximal value could be large. Taking into account the renormalization group running effect, the neutrino spectrum is constrained by experimental data on $\theta_{12}$ in addition to the self-consistency conditions of the models, and the inverted hierarchy spectrum is disfavored for large $\tan\beta$. The evolution of light-neutrino masses is approximately described by a common scaling factor.Comment: 23 pages, 6figure

b -> s gamma in the left-right supersymmetric model

The rare decay $b \to s \gamma$ is studied in the left-right supersymmetric model. We give explicit expressions for all the amplitudes associated with the supersymmetric contributions coming from gluinos, charginos and neutralinos in the model to one-loop level. The branching ratio is enhanced significantly compared to the standard model and minimal supersymmetric standard model values by contributions from the right-handed gaugino and squark sector. We give numerical results coming from the leading order contributions. If the only source of flavor violation comes from the CKM matrix, we constrain the scalar fermion-gaugino sector. If intergenerational mixings are allowed in the squark mass matrix, we constrain such supersymmetric sources of flavor violation. The decay $b \to s \gamma$ sets constraints on the parameters of the model and provides distinguishing signs from other supersymmetric scenarios.Comment: 12 figure