arXiv subjects

Ciprian Dariescu

Publications and source records attributed to Ciprian Dariescu.

26 records · Page 2Linked to original sources

arXiv2007

Improved Factorization Method in Studying B-meson Decays

B decays are a subject of active research since they provide useful information on the dynamics of strong and electroweak interactions for testing the Standard Model (SM) and models beyond and are ideally suited for a critical analysis of CP violation phenomena. Within the standard model, there exist certain relations between CP violating rate differences in B decays in the SU(3) limit, as for example $Δ(\bar{B}^0 \to π^+ π^-) = - Δ(\bar{B}^0 \to π^+ K^-)$. The goal of this letter is to study the direct CP violation asymmetry in a class of processes where there has been recent theoretical progress, as for example the B decays into two light pseudoscalars mesons and into a light pseudoscalar and a light vector meson. We identify relations between rate asymmetries which are valid in the SU(3) limit in the standard model and we compute SU(3) breaking corrections to them, going beyond the naive factorization by using the QCD improved factorization model of Beneke {\it et al.}. Finally, in some processes as for example $BR(B^- \to η^{\prime} K^-)$, we claim that one has to add SUSY contributions to the Wilson coefficients. In these cases, we end with a $BR$ depending on three parameters, whose values are constrained by the experimental data.

hep-ph↗

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↗

arXiv2003

Evolving Maximally Symmetric Spacetime Bubbles from Spontaneous Z_2-Violation at Electroweak Symmetry Breaking Scale

The Einstein-Gordon equations for Friedmann-Robertson-Walker (FRW) geometries in feedback reaction with the quartically self-interacting physical field, arisen from the "inner parity" spontaneous breaking, are explicitly formulated. The Hamiltonian density non-positive extrema would classically forbid both spatially closed and flat homogeneous and isotropic worlds if these were to allow the physical field to (repeatedly) go through and to (finally) settle down in a ground state. In this respect, the fixed point exact solutions of the spontaneous Z_2-symmetry breaking Einstein-Gordon equations (mandatory) describe (k=-1)-FRW manifolds which actually are either Milne or anti-de Sitter Universes. Setting the Z_2-invariance breaking scale at the one of the electroweak symmetry, we speculate on the cosmological implications of the Higgs-anti-de Sitter bubbles and derive a set of particular closed-form solutions to the S_2-cobordism with a spatially flat FRW Universe.

gr-qc↗

arXiv1996

Planary Symmetric Static Worlds with Massless Scalar Sources

Motivated by the recent wave of investigations on plane domain wall spacetimes with nontrivial topologies, the present paper deals with (probably) the most simple source field configuration which can generate a spatially planary symmetric static spacetime, namely a minimally coupled massless scalar field that depends only upon a spacelike coordinate, $z$. It is shown that the corresponding exact solutions $({\cal M}, {\bf{\rm g}}_{\pm})$ are algebraically special, type $D - [S - 3T]_{(11)}$, and represent globally pathologic spacetimes with a $G_{4}$ - group of motion acting on ${\bf{\rm R}}^{2} \times {\bf{\rm R}}$ orbits. In spite of the model simplicity, these $ϕ$ - generated worlds possess naked timelike singularities (reached within a finite universal time by normal non-spacelike geodesics), are completely free of Cauchy surfaces and contain into the $t$ - leveled sections points which can not be jointed by ${\rm C}^{1}$ - trajectories images of oblique non-spacelike geodesics. Finally, we comment on the possibility of deriving from $({\cal M}, {\bf{\rm g}}_{\pm})$ two other physically interesting ^^ ^^ $ϕ$ - generated'' spacetimes, by appropiate jonction conditions in the $(z = 0)$ - plane.

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↗