arXiv subjects

Marina-Aura Dariescu

Publications and source records attributed to Marina-Aura Dariescu.

26 records · Page 2Linked to original sources

arXiv2011

Static charged double-black rings in five dimensions

Using a solution generating technique based on the symmetries of the dimensionally reduced Lagrangian we derive two exact solutions of the Einstein-Maxwell-Dilaton field equations in five dimensions. More specifically, these solutions describe general systems of non-extremally charged static asymptotically flat black bi/di-ring. We compute their conserved charges and investigate some of their properties. As expected, we find that in general there are conical singularities in between the black rings and for the static solutions considered here they cannot be completely eliminated.

gr-qc↗

arXiv2007

B \to K^{*} γDecay within MSSM

The paper deals with a next-to-leading order analysis of the radiative $B \to K^* γ$ decay. Working in a PQCD approach, we compute the correction to the essential form factor, coming from a single gluon exchange with the spectator. We investigate the supersymmetry effects on the branching ratio and direct CP asymmetry and constrain the squark mixing parameter $(δ_{23}^d)_{LR}$.

hep-ph↗

arXiv2004

Alternative Approach to $B^- \to η^{\prime} K^-$ Branching Ratio Calculation

Since the calculation of $BR(B^- \to η^{\prime} K^-)$ in the framework of QCD improved factorization method, developed by Beneke et al., leads to numerical values much below the experimental data, we include two different contributions, in an alternative way. First, we find out that the spectator hard-scattering mechanism increases the $BR$ value with almost 50%, but the predictions depend on the combined singularities in the amplitude convolution. Secondly, by adding SUSY contributions to the Wilson coefficients, we come to a $BR$ depending on three parameters, whose values are constrained by the experimental data.

hep-ph↗

arXiv2003

Branching Ratio and direct CP Asymmetry for $B \to K^{*} γ$ Decay in MSSM

The present paper deals with a next-to-leading order analysis of the radiative $B \to K^* γ$ decay. Working in the PQCD approach developed by Szczepaniak {\it et al.}, we compute the correction, coming from a single gluon exchange with the spectator, to the essential form factor. Since the branching ratio gets much above the experimental data, although in agreement with other theoretical models predictions, we take into consideration the effects of complex flavour couplings in the squark sector. Finally, we discuss these SUSY implications on the branching ratio and direct CP asymmetry values and impose bounds on the squark mixing parameter $(δ_{23}^d)_{LR}$.

hep-ph↗

arXiv2003

First-Order Transitions in Charged Boson Nebulae

Using the first-order approximating solutions to the Einstein-Maxwell-Klein-Gordon system of equations for a complex scalar field minimally coupled to a spherically symmetric spacetime, we study the feedback of gravity and electric field on the charged scalar source. Within a perturbative approach, we compute, in the radiation zone, the transition amplitudes and the coherent source-field regeneration rate.

gr-qc↗

arXiv1996

Perturbative QCD analyses of the nonleptonic $B$ meson decays

Based on Brodsky-Lepage approach, the nonleptonic $B$ meson decay branching ratio is derived in terms of three parameters and is geometrically analysed as the 3-surface embedded in the 4-dimensional (abstract) Euclidean space generated by the three parameters and $BR$. Investigating its 2-dimensional sections, we find ranges for these parameters imposed by a comparison with experimental data.

hep-ph↗

arXiv1995

Perturbative QCD estimation of the $B \to K^{*} + γ$ branching ratio

Working in a perturbative QCD model approach, we obtain the essential form factor of the radiative transition $B \rightarrow V^{*} γ$ and estimate the branching ratio $BR(B \rightarrow K^{*} γ)$. The results are determined by a parameter expressing the momentum distribution in the $B$ - meson wave function. Our estimations are compared to other theoretical predictions as well as to experimental data.

hep-ph↗

arXiv1995

A Toy Model Approach to the Canonical Non-perturbative Quantization of the Spatially Flat Robertson-Walker Spacetimes with Cosmological Constant

We present a toy model approach to the canonical non-perturbative quantization of the spatially-flat Robertson-Walker Universes with cosmological constant, based on the fact that such models are exactly solvable within the framework of a simple Lagrangian formulation. The essential quantum dynamical metric-field and the corresponding Hamiltonian, explicitly derived in terms of annihilation and creation operators, point out that the Wheeler - DeWitt equation is a natural (quantum) generalization of the $G_{44}$ - Einstein equation for the classical De Sitter spacetime and selects the physical states of the quantum De Sitter Universe. As a result of the exponential universal expansion, the usual Fock states (defined as the eigenstates of the number-operator) are no longer invariant under the derived Hamiltonian. They exhibit quantum fluctuation of the energy and of the metric field which lead to a (geometrical) volume quantization.

gr-qc↗