Search results for "Tree"
showing 10 items of 1841 documents
Cranked Relativistic Hartree-Bogoliubov Theory: Formalism and Application to the Superdeformed Bands in the $A\sim 190$ region
2000
Cranked Relativistic Hartree-Bogoliubov theory without and with approximate particle number projection by means of the Lipkin-Nogami method is presented in detail as an extension of Relativistic Mean Field theory with pairing correlations to the rotating frame. Pairing correlations are taken into account by a finite range two-body force of Gogny type. The applicability of this theory to the description of rotating nuclei is studied in detail on the example of superdeformed bands in even-even nuclei of the $A\sim 190$ mass region. Different aspects such as the importance of pairing and particle number projection, the dependence of the results on the parametrization of the RMF Lagrangian and …
Measurement of the interference structure functionRLTfor the12C(e,e′p)reaction in the quasielastic region
1998
The coincidence cross section and the interference structure function, ${R}_{\mathrm{LT}},$ were measured for the ${}^{12}\mathrm{C}{(e,e}^{\ensuremath{'}}p){}^{11}\mathrm{B}$ reaction at quasielastic kinematics and central momentum transfer of $|\stackrel{\ensuremath{\rightarrow}}{q}|=400\mathrm{M}\mathrm{e}\mathrm{V}/\mathrm{c}.$ The measurement was at an opening angle of ${\ensuremath{\theta}}_{\mathrm{pq}}=11\ifmmode^\circ\else\textdegree\fi{},$ covering a range in missing energy of ${E}_{m}=0$ to 65 MeV. The ${R}_{\mathrm{LT}}$ structure function is found to be consistent with zero for ${E}_{m}g50\mathrm{MeV},$ confirming an earlier study which indicated that ${R}_{L}$ vanishes in this…
Tri-bimaximal neutrino mixing and neutrinoless double beta decay
2008
We present a tri-bimaximal lepton mixing scheme where the neutrinoless double beta decay rate (bb0v) has a lower bound which correlates with the ratio alpha = Dmsol/Dmatm well determined by current data, as well as with the unknown Majorana CP phase phi12 characterizing the solar neutrino sub-system. For the special value phi12 = pi/2 (opposite CP-sign neutrinos) the bb0v rate vanishes at tree level when Dmsol/Dmatm = 3/80, only allowed at 3 sigma. For all other cases the rate is nonzero, and lies within current and projected experimental sensitivities close to phi12=0. We suggest two model realizations of this scheme in terms of an A4xZ2 and A4xZ4 flavour symmetries.
Bounds on neutral and charged Higgs from the LHC
2014
After the discovery of a Standard Model-like boson with mass of about 125 GeV the possibility of an enlarged scalar sector arises naturally. Here we present the current status of the phenomenology of the two-Higgs-doublet models with a special focus on the charged Higgs sector. If one considers a fermiophobic charged Higgs (it does not couple to fermions at tree level), all present experimental bounds are evaded trivially, therefore one needs to consider other decay and production channels. In this work we also present some of the interesting features of this specific scenario.
Radiative decay intoγPof the low lying axial-vector mesons
2008
We evaluate the radiative decay into a pseudoscalar meson and a photon of the whole set of the axial-vector mesons dynamically generated from the vector-pseudoscalar meson interaction. We take into account tree level and loop diagrams coming from the axial-vector decay into a vector and a pseudoscalar meson. We find a large span for the values of the radiative widths of the different axial-vector mesons. In particular, we evaluate the radiative decay into K{gamma} of the two K{sub 1}(1270) states, recently claimed theoretically, and discuss the experimental values quoted so far on the assumption of only one state.
Oscillations, neutrino masses and scales of new physics
1999
We show that all the available experimental information involving neutrinos can be accounted for within the framework of already existing models where neutrinos have zero mass at tree level, but obtain a small Dirac mass by radiative corrections.
A time dependent RPA-theory for heavy ion reactions
1980
The time dependent Hartree Fock theory (TDHF) is generalized by incorporating 2p-2h correlations into the TDHF Slater determinant in order to improve the description of two-body observables. To this end a time dependent RPA theory (TDRPA) is formulated using the quasi boson approximation. The approach turns out to be readily applicable requiring only minor changes in the present time TDHF codes. The theory is exemplified by considering the spreading width of the fragment particle number in a nucleus-nucleus collision. The TDRPA states are furthermore used to formulate a scattering theory for heavy ion collisions which incorporates the quantum corrections of orderh2 by means of a gaussian pa…
Equilibrium properties of self-interacting neutrinos in the quasi-particle approach
2004
In this work a neutrino gas in equilibrium is studied both at T=0 and at finite temperature. Neutrinos are treated as massive Dirac quasi-particles with two generations. We include self-interactions among the neutrinos via neutral currents, as well as the interaction with a background of matter. To obtain the equilibrium properties we use Wigner function techniques. To account for corrections beyond the Hartree approximation, we also introduce correlation functions. We prove that, under the quasi-particle approximation, these correlation functions can be expressed as products of Wigner functions. We analyze the main properties of the neutrino eigenmodes in the medium, such as effective mass…
Relativistic Wigner function approach to neutrino propagation in matter
1999
In this work we study the propagation of massive Dirac neutrinos in matter with flavor mixing, using statistical techniques based on Relativistic Wigner Functions. First, we consider neutrinos in equilibrium within the Hartree approximation, and obtain the corresponding relativistic dispersion relations and effective masses. After this, we analyze the same system out of equilibrium. We verify that, under the appropiate physical conditions, the well known equations for the MSW effect are recovered. The techniques we used here appear as an alternative to describe neutrino properties and transport equations in a consistent way.
Quadrupole variation of projected spectra of even Ti isotopes
1975
In the present work we study the dependence of projected good $J$ states on the quadrupole moment. In order to achieve this, the quadrupole-moment-depenent generalized deformed BCS (DBCS) wave functions have been computed after minimizing the constrained Hamiltonian ${H}_{q}=H\ensuremath{-}\ensuremath{\lambda}N\ensuremath{-}\ensuremath{\mu}Q$. The calculation assumes the existence of a $^{40}\mathrm{Ca}$ spherical core. The two body residual interaction between the valence nucleons is determined by using the $^{42}\mathrm{Sc}$ spectrum for the $T=0$ force and the $^{49}\mathrm{Ca}$ spectrum for the $T=1$ force. The result of the calculation shows that the projected spectra in general cannot…