arXiv subjects
Publications and source records attributed to N. Paver.
We review several aspects of the phenomenology of P-wave $\bar q Q$ mesons: mass splittings, effective strong couplings and leptonic constants. We also describe a QCD sum rule determination to order $α_s$ of the form factor $τ_{1/2}(y)$ governing the semileptonic $B$ decays to the charm doublet with $J^P=(0^+_{1/2},1^+_{1/2})$.
Fermion compositeness, and other types of new physics that can be described by the exchange of very massive particles, can manifest themselves as the result of an effective four-fermion contact interaction. In the case of the processes $e^+e^-\to μ^+μ^-,τ^+τ^-,\bar{b}b$ and $\bar{c}c$ at future $e^+e^-$ colliders with $\sqrt{s}=0.5-1$ TeV, we examine the sensitivity to four-fermion contact interactions of two new integrated observables, $σ_+$ and $σ_-$, conveniently defined for such kind of analysis. We find that, if longitudinal polarization of the electron beam were available, these observables would offer the opportunity to separate the helicity cross sections and, in this way, to derive model-independent bounds on the relevant parameters.
We use QCD sum rules, in the framework of the Heavy Quark Effective Theory, to calculate the universal form factor $τ_{1/2}(y)$ parameterizing the semileptonic transitions $B \to D_0 \ell \bar ν$, $B \to D_1^* \ell \bar ν$, where $D_0$ and $D^*_1$ are the members of the excited charmed doublet with $J^P=(0^+_{1/2},1^+_{1/2})$. We include two-loop corrections in the perturbative contribution to the sum rule, and present a complete next-to-leading order result. As a preliminary part of our analysis we also compute, up to order $α_s$, the leptonic constant $F^+$ of the doublet $D_0$, $D_1^*$. Finally, we discuss the phenomenological implications of this calculation.
In the case of the process $e^+e^-\toμ^+μ^-$, we study the sensitivity to either $Z^\prime$ or anomalous gauge coupling effects of two new observables, $σ_+$ and $σ_-$, conveniently defined for such kind of analysis. We discuss general properties of the deviations of these observables from the Standard Model predictions, and derive the model-independent bounds on the relevant parameters allowed by present and foreseeable LEP2 data. We also discuss the possibility of separating the two kinds of effect.
By means of a model-independent analysis, we discuss the constraints on anomalous trilinear gauge-boson couplings that can be obtained from the study of electron-positron annihilation into $W$ pairs at LC with \sqrt{s}=0.5 TeV and 1 TeV. We consider the general CP conserving anomalous effective Lagrangian, as well as some specific models with reduced number of independent couplings. The analysis is based on combinations of observables with initial and final state polarizations, that allow to separately constrain the different couplings and to improve the corresponding numerical bounds.
We show that the availability of longitudinally polarized electron beams at a 500 GeV Linear Collider would allow, from an analysis of the reaction e^+e^-\to W^+W^-, to set stringent bounds on the couplings of a Z' of the most general type. In addition, to some extent, it would be possible to disentangle observable effects of the Z' from analogous ones due to competitor models with anomalous trilinear gauge couplings.
In the QCD Sum Rule determination of $m_s$ using the two-point correlator of divergences of $ΔS=1$ vector currents, the final uncertainty on $m_s$ is mainly due to the hadronic spectral function. Using a specific parameterization which fully takes into account the available experimental data on the $K π$ ($I=1/2, J^P=0^+)$ system, characterized by the presence of a relevant nonresonant component in addition to the resonant one, we find ${\bar m_s}(1 GeV)\ge 120 MeV$. In particular, varying only the parameters describing the nonresonant $K π$ component and $Λ_{\bar {MS}}^{n_f=3}$ we obtain ${\bar m_s}(1 GeV)=125 - 160 MeV$. This result is smaller than analogous ones obtained by using a parameterization in terms of only resonant states. We discuss how to systematically improve the determination of $m_s$ by this method.
We discuss the potential of NLC500 and NLC1000 to probe Z-Z' mixing and mass by the reaction e^+e^- -> W^+W^- with longitudinally polarized electrons. We perform a model-independent analysis of the deviations from the Standard Model, and apply it to a specific class of extended weak gauge models. Results indicate that the corresponding bounds at the NLC500 complement the present ones obtained from LEP1, and rapidly become quite stringent at the higher energy of the NLC1000. Also, we emphasize the importance of initial beam polarization in improving the sensitivity to mixing.
We consider the problem of determining the matrix element of the heavy quark kinetic energy operator between $Λ_b$ baryonic states by three point function QCD sum rules in the Heavy Quark Effective Theory. We discuss the main features and the uncertainties associated to such an approach. Numerically, we find the result: ${\langle{\cal K}\rangle}_{Λ_b} = - (0.6 \pm 0.1) \; GeV^2$. Within the uncertainty of the method, such result indicates a value of the heavy quark kinetic energy in the baryon similar in size to that in the meson.
We evaluate the constraints on anomalous trilinear gauge-boson couplings that can be obtained from the study of electron-positron annihilation into $W$ pairs at a facility with either the electron beam longitudinally polarized or both electron and positron beams transversely polarized. The energy ranges considered in the analysis are the ones relevant to the next-linear collider and to LEP~200. We discuss the possibilities of a model independent analysis of the general $CP$ conserving anomalous effective Lagrangian, as well as its restriction to some specific models with reduced number of independent couplings. The combination of observables with initial and final state polarizations allows to separately constrain the different couplings and to improve the corresponding numerical bounds.
We propose a number of tests of factorization for the color-suppressed nonleptonic decay channels: $B \to K^{(*)} \; η_c$ and $B \to K^{(*)} \; η^\prime_c$. The relevant leptonic constants and form factors are calculated within the QCD sum rules approach.
We discuss the potential of a $0.5\hskip 2pt TeV$ linear collider to explore manifestations of extended (or alternative) electroweak models of current interest, through measurements of the reaction $e^+e^-\to W^+W^-$ with both initial and final states polarization. Specifically, we consider the possibility to put stringent constraints on lepton mixing (or extended lepton couplings) and $Z-Z^\prime$ mixing, showing in particular the usefulness of polarization in order to disentangle these effects.
We explore the possibility of deriving model independent limits on the anomalous trilinear electroweak gauge boson couplings from high energy $e^+e^-\to W^+W^-$, by combining the cross sections for the different initial and final states polarizations integrated with suitable kinematical cuts. In the case of the CP conserving couplings the limits can be disentangled, and are given by simple mathematical expressions. Numerical results show the advantages of this approach, in particular the important role of polarization in improving the bounds.
Relativistic and non-relativistic ratios of Laplace transform QCD moment sum rules for charmonium are used in order to determine the value of the on-shell charm-quark mass. The validity of the non-relativistic version of QCD sum rules in this particular application is discussed. After using current values of the perturbative and non-perturbative QCD parameters, as well as experimental data on the $J/ψ$ system, we obtain $m_{c}(Q^{2}=m_{c}^{2}) = 1.46 \pm 0.07 \;\mbox{GeV}$.
We present a consistent analysis of final state interactions in ${K\rightarrow 3π}$ decays in the framework of Chiral Perturbation Theory. The result is that the kinematical dependence of the rescattering phases cannot be neglected. The possibility of extracting the phase shifts from future $K_S-K_L$ interference experiments is also analyzed.
We discuss the time dependent interferences between $K_L$ and $K_S$ in the decays in $3π$ and $ππγ$, to be studied at interferometry machines such as the $ϕ$-factory and LEAR. We emphasize the possibilities and the advantages of using interferences, in comparison with width measurements, to obtain information both on $CP$ conserving and $CP$ violating amplitudes. Comparison with present data and suggestions for future experiments are made.
We study the potential of the next-generation $e^+ e^-$ linear colliders with longitudinally polarized beams, to restrict the values of the anomalous trilinear couplings $WWγ$ and $WWZ$ from the measurement of the process $e^+ e^-\to W^+ W^-$. Along with initial $e^+e^-$ polarization, we account also for the possibilities offered by cross sections for polarized final $W$, in order to disentangle the constraints on the various constants. The results show the essential role of the initial beams polarization in improving the bounds obtained from the unpolarized case.
Using a current algebra framework, we discuss the contribution of vector meson exchanges to the CP violating asymmetry in the decay $K^{\pm}\rightarrowπ^{\pm}π^0$, resulting from the interference of the $K\rightarrowππ$ amplitude with the radiative correction $K\rightarrowππγ$.