Narrow Results

The charmonium mass spectrum is considered in the framework of the constituent quark model with the relativistic treatment of the c quark. The obtained masses are in good agreement with the existing experimental data including the mass of η_c(2S).

The masses of the S-wave mesons consisting of the light (u, d, s) quarks are calculated within the constituent quark model. The relativistic Schrödinger-like equation with a confining potential is numerically solved for the complete relativistic potential including both spin-independent and spin-dependent terms. The obtained masses of the ground state π, ρ, K, K* and ϕ mesons and their first radial excitations are in a reasonably good overall agreement with experimental data.

We study the SL(2,R) WZWN string model describing bosonic string theory in AdS₃ spacetime as a deformed oscillator together with its mass spectrum and the string modified SL(2,R) uncertainty relation. The SL(2,R) string oscillator is far more quantum (with higher quantum uncertainty) and more excited than the non-deformed one. This is accompassed by the highly excited string mass spectrum which is drastically changed with respect to the low excited one. The highly excited quantum string regime and the low excited semiclassical regime of the SL(2,R) string model are described and shown to be the quantum-classical dual of each other in the precise sense of the usual classical-quantum duality. This classical-quantum realization is not assumed nor conjectured. The quantum regime (high curvature) displays a modified Heisenberg's uncertainty relation, while the classical (low curvature) regime has the usual quantum mechanics uncertainty principle.

I study indirect CP violation for neutral kaons, and extend it to large values of the CP-violating parameter (taken to be real). I show how and at which condition there can exist a continuous set of basis in which the kinetic and mass terms in the Lagrangian can be diagonalized simultaneously. An ambiguity results for the mass spectrum, which then depends on the basis. In particular, for fixed (positive) (mass)² of the CP eigenstates , and for certain ranges of values of the CP-violating parameter, a negative (mass)² can arise in the CP-violating basis. Under certain conditions, even a small perturbation, lifting the ambiguity, can drastically affect the pattern of masses.

These investigations extend in a natural way to indirect CP violation among a set of Higgs-like doublets.

The C-odd commutator , or its equivalent for Higgs multiplets, plays an important role. The condition for its vanishing and its consequences are among the main concerns of this work.

Key issues and essential features of classical and quantum strings in gravitational plane waves, shock waves and space–time singularities are synthetically understood. This includes the string mass and mode number excitations, energy–momentum tensor, scattering amplitudes, vacuum polarization and wave-string polarization effect. The role of the real pole singularities characteristic of the tree level string spectrum (real mass resonances) and that of the space–time singularities is clearly exhibited. This throws light on the issue of singularities in string theory which can be thus classified and fully physically characterized in two different sets: strong singularities (poles of order ≥ 2, and black holes) where the string motion is collective and nonoscillating in time, outgoing states and scattering sector do not appear, the string does not cross the singularities; and weak singularities (poles of order < 2, (Dirac δ belongs to this class) and conic/orbifold singularities) where the whole string motion is oscillatory in time, outgoing and scattering states exist, and the string crosses the singularities.

Common features of strings in singular wave backgrounds and in inflationary backgrounds are explicitly exhibited.

The string dynamics and the scattering/excitation through the singularities (whatever their kind: strong or weak) is fully physically consistent and meaningful.

We calculate the mass spectrum, the splitting values and some other properties in the framework of the semirelativistic equation by applying the shifted large-N expansion technique. We use seven different central potentials together with an improved QCD-motivated interquark potentials calculated to two loops in the modified minimal-subtraction scheme. The parameters of these potentials are fitted to generate the semirelativistic bound states of quarkonium system in close conformity with the experimental and the present available calculated center-of-gravity (c.o.g.) data. Calculations of the energy bound states are carried out up to third order. Our results are in excellent fit with the results of the other works.

We give a review and present a comprehensive calculation for the leptonic constant f_Bc of the low-lying pseudoscalar and vector states of B_c-meson in the framework of static and QCD-motivated nonrelativistic potential models taking into account the one-loop and two-loop QCD corrections in the short distance coefficient that governs the leptonic constant of B_c quarkonium system. Further, we use the scaling relation to predict the leptonic constant of the nS-states of the system. Our results are compared with other models to gauge the reliability of the predictions and point out differences.

We show that for a λϕ⁴ theory having many components, the solution with all equal components in the infrared regime is stable with respect to our expansion given by a recently devised approach to analyze strongly coupled quantum field theory. The analysis is extended to a pure Yang–Mills theory showing how, in this case, the given asymptotic series exists. In this way, many components theories in the infrared regime can be mapped to a single component scalar field theory obtaining their spectrum.

We prove the existence of a strong coupling expansion for a classical λϕ⁴ field theory in agreement with the duality principle in perturbation theory put forward in a paper: M. Frasca, Phys. Rev. A58, 3439 (1998). The leading order solution is a snoidal wave taking the place of plane waves of the free theory. We compute the first-order correction and show that higher-order terms do renormalize the leading order solution.

Recent progress is presented on higher-order calculations for the mass spectrum of Higgs particles in the CP-conserving and CP-violating MSSM, covering diagrammatic two-loop calculations for neutral and charged Higgs bosons as well as all-order resummation of large logarithms arising from the strong and Yukawa coupling sectors.

In the framework of static and QCD-motivated model potentials for heavy quarkonium, we present a further comprehensive calculation of the mass spectrum of system and its ground state spin-dependent splittings in the context of the shifted l-expansion technique. We also predict the leptonic constant f_Bc of the lightest pseudoscalar B_c, and of the vector states taking into account the one-loop and two-loop QCD corrections. Furthermore, we use the scaling relation to predict the leptonic constant of the nS-states of the system. Our predicted results are generally in high agreement with some earlier numerical methods. The parameters of each potential are adjusted to obtain best agreement with the experimental spin-averaged data (SAD).

In this paper, we study the mass spectrum and decay constants of ground state (1S) and radially excited states (2S and 3S) of heavy equal mass pseudoscalar mesons, η_c and η_b. We have employed the framework of Bethe–Salpeter equation (BSE) under Covariant Instantaneous Ansatz (CIA). Our predictions are in reasonable agreement with the data on available states and results of other models.

In this paper, we calculate the mass spectrum, weak decay constants, two photon decay widths, and two-gluon decay widths of ground ($1S$) and radially excited ($2S,3S,\dots$) states of pseudoscalar charmoniuum and bottomonium such as ${\eta }_c$ and ${\eta }_b$, as well as the mass spectrum and leptonic decay constants of ground state ($1S$), excited ($2S,1D,3S,2D,4S,\dots ,5D$) states of vector charmonium and bottomonium such as $J/\psi$, and $\mathrm{{\rm Y}}$, using the formulation of Bethe–Salpeter equation under covariant instantaneous ansatz (CIA). Our results are in good agreement with data (where ever available) and other models. In this framework, from the beginning, we employ a $4\times 4$ representation for two-body ($q\overline{q}$) BS amplitude for calculating both the mass spectra as well as the transition amplitudes. However, the price we have to pay is to solve a coupled set of equations for both pseudoscalar and vector quarkonia, which we have explicitly shown get decoupled in the heavy-quark approximation, leading to mass spectral equation with analytical solutions for both masses, as well as eigenfunctions for all the above states, in an approximate harmonic oscillator basis. The analytical forms of eigenfunctions for ground and excited states so obtained are used to evaluate the decay constants and decay widths for different processes.

In protein identification by tandem mass spectrometry, it is critical to accurately predict the theoretical spectrum for a peptide sequence. To date, the widely-used database searching methods adopted simple statistical models for predicting. For some peptide, these models usually yield a theoretical spectrum with a significant deviation from the experimental one. In this paper, in order to derive an improved predicting model, we utilized a non-linear programming model to quantify the factors impacting peptide fragmentation. Then, an iterative algorithm was proposed to solve this optimization problem. Upon a training set of 1803 spectra, the experimental result showed a good agreement with some known principles about peptide fragmentation, such as the tendency to cleave at the middle of peptide, and Pro's preference of the N-terminal cleavage. Moreover, upon a testing set of 941 spectra, comparison of the predicted spectra against the experimental ones showed that this method can generate reasonable predictions. The results in this paper can offer help to both database searching and de novo methods.

One presents an exact solution of the Frampton-Pisano-Pleitez three-generation 331 gauge model equipped with a special Higgs mechanism and a new kind of Yukawa couplings in unitary gauge. It is shown that the resulting boson mass spectrum depends on a real parameter. There exists a critical value of this parameter for which the different gauge bosons carrying the same charge get the same mass.

Recent progress is presented on higher-order calculations for the mass spectrum of Higgs particles in the CP-conserving and CP-violating MSSM, covering diagrammatic two-loop calculations for neutral and charged Higgs bosons as well as all-order resummation of large logarithms arising from the strong and Yukawa coupling sectors.