Lepton flavor-changing Scalar Interactions and Muon g−2g-2

A systematic investigation on muon anomalous magnetic moment and related lepton flavor-violating process such as \m\to e\g, \t\to e\g and \t\to \m\g is made at two loop level in the models with flavor-changing scalar interactions. The two loop diagrams with double scalar exchanges are studied and their contributions are found to be compatible with the ones from Barr-Zee diagram. By comparing with the latest data, the allowed ranges for the relevant Yukawa couplings $Y_{ij}$ in lepton sector are obtained. The results show a hierarchical structure of Y_{\m e, \t e} \ll Y_{\m \t} \simeq Y_{\m\m} in the physical basis if $\Delta a_{\mu}$ is found to be $>50\times 10^{-11}$. It deviates from the widely used ansatz in which the off diagonal elements are proportional to the square root of the products of related fermion masses. An alternative Yukawa coupling matrix in the lepton sector is suggested to understand the current data. With such a reasonable Yukawa coupling ansatz, the decay rate of \t\to \m\g is found to be near the current experiment upper bound.Comment: 15 pages, Revtex, 9 figures, published version in EPJ

A Time Evolution Study of the Superhumps of the Dwarf Nova 1RXS J232953.9+062814 by Wavelet Transform

The time evolution behaviour of the superhumps of the dwarf nova 1RXS J232953.9+062814 is investigated with the wavelet analysis method. On the basis of two nights CCD photometry performed during its first superoutburst as well as other published brightness data, we reveal the superhump's time-dependence as a function of periods and time. Our light curves, which phased in the rapid decay ending portion of the superoutburst and in the dawn of a following normal outburst, are important to help trace the superhump evolution for the star. Evident amplitude variations of the superhumps, reflecting the fading of outbursts, are detected. The general profile of brightness fading over the outbursts roughly followed an exponential decay law or a form of a five-order polynomial. Both the superhump period and the orbital period of the binary system are detected in the present data. We obtain P_sh=0.04575(5) d and P_orb=0.04496(5) d. They agree with the existing values based on additional data. The two periods exchanged their roles during the superhump evolution.Comment: 7 pages, 9 figures, submitted to Astronomy & Astrophysic

Is the f0(600)f_0(600) meson a dynamically generated resonance? -- a lesson learned from the O(N) model and beyond

O(N) linear $\sigma$ model is solvable in the large $N$ limit and hence provides a useful theoretical laboratory to test various unitarization approximations. We find that the large $N_c$ limit and the $m_\sigma\to \infty$ limit do not commute. In order to get the correct large $N_c$ spectrum one has to firstly take the large $N_c$ limit. We argue that the $f_0(600)$ meson may not be described as generated dynamically. On the contrary, it is most appropriately described at the same level as the pions, i.e, both appear explicitly in the effective lagrangian. Actually it is very likely the $\sigma$ meson responsible for the spontaneous chiral symmetry breaking in a lagrangian with linearly realized chiral symmetry.Comment: 15 pages, 3 figurs; references added; discussions slightly modified; revised version accepted by IJMP