Electronic spectra of polyatomic molecules with resolved individual rotational transitions

The density of rotational transitions for a polyatomic molecule is so large that in general many such transitions are hidden under the Doppler profile, this being a fundamental limit of conventional high resolution electronic spectroscopy. We present here the first Doppler-free cw two-photon spectrum of a polyatomic molecule. In the case of benzene, 400 lines are observed of which 300 are due to single rotational transitions, their spacing being weil below the Doppler profile. The resolution so achieved is 1.5 X 10'. Benzene is a prototype planar molecule taken to have D •• symmetry in the ground as weil as in the first excited state. From our ultra-high resolution results it is found that benzene in the excited SI state i8 a symmetrical rotor to a high degree. A negative inertial defect is found for the excited state. The origin of this inertial defect is discused

QCD sum rules for D and B mesons in nuclear matter

QCD sum rules for D and B mesons embedded in cold nuclear matter are evaluated. We quantify the mass splitting of D - D-bar and B - B-bar mesons as a function of the nuclear matter density; extrapolated to saturation density it is in the order of 60 and 130 MeV driven essentially by the condensates , and . The genuine chiral condensate , amplified by heavy-quark masses, enters the Borel transformed sum rules for the mass splitting beyond linear density dependence. Including strange quark condensates reveals a umerically smaller and opposite effect for the Ds - Ds-bar mass splitting.Comment: 16 pages, 8 figures, to be published; a broader range of condensate values is discussed (v2

Instabilities for a relativistic electron beam interacting with a laser irradiated plasma

The effects of a radiation field (RF) on the unstable modes developed in relativistic electron beam--plasma interaction are investigated assuming that $\omega_{0} >\omega_{p}$, where $\omega_{0}$ is the frequency of the RF and $\omega_{p}$ is the plasma frequency. These unstable modes are parametrically coupled to each other due to the RF and are a mix between two--stream and parametric instabilities. The dispersion equations are derived by the linearization of the kinetic equations for a beam--plasma system as well as the Maxwell equations. In order to highlight the effect of the radiation field we present a comparison of our analytical and numerical results obtained for nonzero RF with those for vanishing RF. Assuming that the drift velocity $\mathbf{u}_{b}$ of the beam is parallel to the wave vector $\mathbf{k}$ of the excitations two particular transversal and parallel configurations of the polarization vector $\mathbf{E}_{0}$ of the RF with respect to $\mathbf{k}$ are considered in detail. It is shown that in both geometries resonant and nonresonant couplings between different modes are possible. The largest growth rates are expected at the transversal configuration when $\mathbf{E}_{0}$ is perpendicular to $\mathbf{k}$. In this case it is demonstrated that in general the spectrum of the unstable modes in $\omega$--$k$ plane is split into two distinct domains with long and short wavelengths, where the unstable modes are mainly sensitive to the beam or the RF parameters, respectively. In parallel configuration, $\mathbf{E}_{0} \parallel \mathbf{k}$, and at short wavelengths the growth rates of the unstable modes are sensitive to both beam and RF parameters remaining insensitive to the RF at long wavelengths.Comment: 23 pages, 5 figure

Unparticle effects in rare (t -> c g g) decay

Rare (t -> c g g) decay can only appear at loop level in the Standard Model (SM), and naturally they are strongly suppressed. These flavor changing decays induced by the mediation of spin-0 and spin-2 unparticles, can appear at tree level in unparticle physics. In this work the virtual effects of unparticle physics in the flavor-changing (t -> c g g) decay is studied. Using the SM result for the branching ratio of the (t -> c g g) decay, the parameter space of d_U and Lambda_U, where the branching ratio of this decay exceeds the one predicted by the SM, is obtained. Measurement of the branching ratio larger than 10^(-9) can give valuable information for establishing unparticle physics.Comment: 15 pages, 7 figures, LaTeX formatte

Lepton polarization correlations in B→K∗τ−τ+B \to K^* \tau^- \tau^+

In this work we will study the polarizations of both leptons ($\tau$) in the decay channel $B\to K^* \tau^- \tau^+$. In the case of the dileptonic inclusive decay $B\to K^* \ell^- \ell^+$, where apart from the polarization asymmetries of single lepton $\ell$, one can also observe the polarization asymmetries of both leptons simultaneously. If this sort of measurement is possible then we can have, apart from decay rate, FB asymmetry and the six single lepton polarization asymmetries (three each for $\ell^-$ and $\ell^+$), nine more double polarization asymmetries. This will give us a very useful tool in more strict testing of SM and the physics beyond. We discuss the double polarization asymmetries of $\tau$ leptons in the decay mode $B\to K^* \tau^- \tau^+$ within the SM and the Minimal Supersymmetric extensions of it.Comment: 21 pages, 21 figures; version to match paper to appear in PR

Semileptonic Dq→K1ℓνD_{q}\to K_{1}\ell \nu and nonleptonic D→K1πD\to K_1 \pi decays in three--point QCD sum rules and factorization approach

We analyze the semileptonic $D_{q}\to K_1 \ell\nu$ transition with $q=u, d, s$, in the framework of the three--point QCD sum rules and the nonleptonic $D\to K_1 \pi$ decay within the QCD factorization approach. We study $D_{q}$ to $K_1(1270)$ and $K_1(1400)$ transition form factors by separating the mixture of the $K_1(1270)$ and $K_1(1400)$ states. Using the transition form factors of the $D\to K_1$, we analyze the nonleptonic $D\to K_1 \pi$ decay. We also present the decay amplitude and decay width of these decays in terms of the transition form factors. The branching ratios of these channel modes are also calculated at different values of the mixing angle $\theta_{K_1}$ and compared with the existing experimental data for the nonleptonic case.Comment: 28 Pages, 20 Figures and 9 Table