arXiv subjects

M. G. Olsson

Publications and source records attributed to M. G. Olsson.

At least 19 recordsLinked to original sources

arXiv2004

Direct experimental test of scalar confinement

The concept of Lorentz scalar quark confinement has a long history and is still widely used despite its well-known theoretical faults. We point out here that the predictions of scalar confinement also conflict directly with experiment. We investigate the dependence of heavy-light meson mass differences on the mass of the light quark. In particular, we examine the strange and non-strange D mesons. We find that the predictions of scalar confinement are in considerable conflict with measured values.

hep-ph↗

arXiv2003

Universal light quark mass dependence and heavy-light meson spectroscopy

Clean predictions are presented for all the spin-averaged heavy-light meson spectroscopies. A new symmetry is identified wherein the energy eigenstates have a universal dependence on both the light and heavy quark masses. This universality is used in an efficient analysis of these mesons within the QCD string/flux tube picture. Unique predictions for all the D, D_s, B, and B_s type mesons in terms of just four measured quantities.

hep-ph↗

arXiv2003

QCD strings with spinning quarks

We construct a consistent action for a massive spinning quark on the end of a QCD string that leads to pure Thomas precession of the quark's spin. The string action is modified by the addition of Grassmann degrees of freedom to the string such that the equations of motion for the quark spin follow from boundary conditions, just as do those for the quark's position.

hep-ph↗

arXiv2003

Reduction of the QCD string to a time component vector potential

We demonstrate the equivalence of the relativistic flux tube model of mesons to a simple potential model in the regime of large radial excitation. We make no restriction on the quark masses; either quark may have a zero or finite mass. Our primary result shows that for fixed angular momentum and large radial excitation, the flux tube/QCD string meson with a short-range Coulomb interaction is described by a spinless Salpeter equation with a time component vector potential V(r) = ar - k/r.

hep-ph↗

arXiv2003

QCD String Structure in Vector Confinement

We demonstrate that the Nambu-Goto string spectroscopy with massless quarks is replicated in highly excited states of the linear vector confinement potential. For deep radial excitations we observe that the Regge slope, spacing between daughter trajectories, and absolute state energies agree with those of the QCD string.

hep-ph↗

arXiv2002

A Roadmap For Meson Spectroscopy

An efficient classification of light quark meson states is discussed based on the dominance of angular and radial quark excitation. A synthesis of Regge and quark dynamics allows a natural unification of light quark-antiquark spectroscopies and indicates the states that fall outside this category such as molecules, hybrids, and glueballs.

hep-ph↗

arXiv2001

Analytic Quantization of the QCD String

We perform an analytic semi-classical quantization of the straight QCD string with one end fixed and a massless quark on the other, in the limits of orbital and radial dominant motion. We compare our results to the exact numerical semi-classical quantization. We observe that the numerical semi-classical quantization agrees well with our exact numerical canonical quantization.

hep-ph↗

arXiv2000

Semileptonic form factors - a model-independent approach

We demonstrate that the B->D(*) l nu form factors can be accurately predicted given the slope parameter rho^2 of the Isgur-Wise function. Only weak assumptions, consistent with lattice results, on the wavefunction for the light degrees of freedom are required to establish this result. We observe that the QCD and 1/m_Q corrections can be systematically represented by an effective Isgur-Wise function of shifted slope. This greatly simplifies the analysis of semileptonic B decay. We also investigate what the available semileptonic data can tell us about lattice QCD and Heavy Quark Effective Theory. A rigorous identity relating the form factor slope difference rho_D^2-rho_A1^2 to a combination of form factor intercepts is found. The identity provides a means of checking theoretically evaluated intercepts with experiment.

hep-ph↗

arXiv2000

Remark on the computation of mode sums

The computation of mode sums of the types encountered in basic quantum field theoretic applications is addressed with an emphasis on their expansions into functions of distance that can be interpreted as potentials. We show how to regularize and calculate the Casimir energy for the continuum Nambu-Goto string with massive ends as well as for the discrete Isgur-Paton non-relativistic string with massive ends. As an additional example, we examine the effect on the interquark potential of a constant Kalb-Ramond field strength interacting with a QCD string.

hep-th↗

arXiv2000

The Nucleon Sigma Term from Threshold Parameters

A new sum rule determines the nucleon sigma term by the πN elastic scattering threshold parameters alone. This "threshold" value of σ(2μ^2) provides an independent check of existing values obtained from global dispersive analyses, and also provides a realistic error assignment. Employing a recent analysis of low energy (T_π< 100 MeV) πN data our sum rule implies σ(2μ^2) = 71\pm 9 MeV.

hep-ph↗

arXiv2000

From scalar to string confinement

We outline a connection between scalar quark confinement, a phenomenologically successful concept heretofore lacking fundamental justification, and QCD. Although scalar confinement does not follow from QCD, there is an interesting and close relationship between them. We develop a simple model intermediate between scalar confinement and the QCD string for illustrative purposes. Finally, we find the bound state masses of scalar, time-component vector, and string confinement analytically through semi-classical quantization.

hep-ph↗

arXiv1999

Curved QCD string dynamics

We consider the effects of going beyond the approximation of a straight string in mesons by using a flexible flux tube model wherein a Nambu-Goto string bends in response to quark accelerations. The curved string is dynamically identical to the straight string even for ultra-relativistic mesons except for a small additional radial momentum. We numerically solve the curved string model in the case where both ends have equal mass quarks and also the case where one end is fixed. No approximation of non-relativistic motion is made. We note some small but interesting difference from the straight string.

hep-ph↗

arXiv1999

Adiabatic string shape for non-uniform rotation

It is well known that a straight Nambu-Goto string is an exact solution of the equations of motion when its end moves in a circular orbit. In this paper we investigate the shape of a confining relativistic string for a general motion of its end. We determine analytically the shape of the curved string to leading order in deviation from straightness, and show that it reduces to an expected non-relativistic result. We also demonstrate numerically that in realistic meson models this deviation is always small. We further find that the angular momentum and energy are the same as for the straight string, but that the curved string has a small radial momentum not present in a straight string. Our results justify the common assumption of straight strings usually made in hadron models.

hep-ph↗

arXiv1998

Excited glue and the vibrating flux tube

Recent lattice results for the energy of gluonic excitations as a function of quark separation are shown to correspond to transverse relativistic flux tube vibration modes. For large quark separations all states appear to degenerate into a few categories which are predicted uniquely, given the ground state.

hep-ph↗

arXiv1997

Rigorous pion-pion scattering lengths from threshold pi N --> pi pi N data

A new evaluation of the universal $ππ$ scattering length relation is used to extract the $ππ$ $s$-wave scattering lengths from threshold pion production data. Previous work has shown that the chiral perturbation series relating threshold pion production to $ππ$ scattering lengths appears to converge well only for the isospin-2 case, giving $a_2 = -0.031\pm 0.007 m_π^{-1}$. A model-independent and data-insensitive universal curve then implies $a_0 = 0.235\pm 0.03 m_π^{-1}$ for the isospin-0 scattering length.

hep-ph↗

arXiv1997

Semi-Leptonic B Decay

The definitions and properties of elastic and inelastic Isgur-Wise form factors are reviewed. The nature of the "missing" exclusive semi-leptonic decay fraction is identified. The role that completeness sum rules play in relating form factors, spectroscopy, and model building is outlined.

hep-ph↗

arXiv1997

On the bounds for the curvature and higher derivatives of the Isgur-Wise function

We discuss constraints imposed on the zero-recoil curvature and higher derivatives of the Isgur-Wise function by a general quark model. These constraints are expressed as bounds for a given slope parameter, and compared with those based upon analyticity properties of QCD spectral functions. Our results also indicate that in the analysis of the experimental data for semileptonic $B\rar D^{(*)}$ decays it may be important to include at least the third term in the form factor expansion about the zero recoil point.

hep-ph↗

arXiv1997

The anomalous threshold, confinement, and an essential singularity in the heavy-light form factor

The analytic behavior of the heavy-light meson form factor is investigated using several relativistic examples including unconfined, weakly confined, and strongly confined mesons. It is observed that confinement erases the anomalous threshold singularity and also induces an essential singularity at the normal annihilation threshold. In the weak confinement limit, the "would be" anomalous threshold contribution is identical to that of the real singularity on its space-like side.

hep-ph↗