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M. G. Olsson

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

36 records · Page 2Linked to original sources
arXiv1997

On quark confinement dynamics

Starting from Buchmüller's observation that a chromoelectric flux tube meson will exhibit only the Thomas type spin-orbit interaction, we show that a model built upon the related assumption that a quark feels only a constant radial chromoelectric field in its rest frame implies a complete relativistic effective Hamiltonian that can be written explicitly in terms of quark canonical variables. The model yields linear Regge trajectories and exhibits some similarities to scalar confinement, but with the advantage of being more closely linked to QCD.

hep-ph↗
arXiv1996

Universal Behavior in Excited Heavy-Light and Light-Light Mesons

A common pattern of large orbital and radial excitations in heavy-light and light-light mesons is demonstrated. Within a general potential model the Regge slopes of the light degrees of freedom for these mesons are shown to be in the ratio of two. The possibility of ``tower'' degeneracy occurs only with pure scalar confinement.

hep-ph↗
arXiv1996

Confinement, Spin, and QCD

The experimental and theoretical evidence relating spin dependence and long range confinement is reviewed. One of the simplest confinement ideas, the dynamic electric flux tube picture of Buchmüller, can be exploited to yield a complete effective Hamiltonian. In addition to pure Thomas spin-orbit splitting the other relativistic corrections are calculated. It is shown that our effective Hamiltonian is identical to the mechanical relativistic flux tube model and gives relativistic corrections in agreement with QCD predictions.

hep-ph↗
arXiv1996

Semi-leptonic B decays into higher charmed resonances

We apply HQET to semi-leptonic $B$ meson decays into a variety of excited charm states. Using three realistic meson models with fermionic light degrees of freedom, we examine the extent that the sum of exclusive single charmed states account for the inclusive semi-leptonic $B$ decay rate. The consistency of form factors with the Bjorken and Voloshin sum rules is also investigated.

hep-ph↗
arXiv1995

Fermion Confinement by a Relativistic Flux Tube

We formulate the description of the dynamic confinement of a single fermion by a flux tube. The range of applicability of this model extends from the relativistic corrections of a slowly moving quark to the ultra-relativistic motion in a heavy-light meson. The reduced Salpeter equation, also known as the no-pair equation, provides the framework for our discussion. The Regge structure is that of a Nambu string with one end fixed. Numerical solutions are found giving very good fits to heavy-light meson masses. An Isgur-Wise function with a zero recoil slope of $ξ'(1)\simeq -1.26 $ is obtained.

hep-ph↗
arXiv1995

On the validity of the reduced Salpeter equation

We adapt a general method to solve both the full and reduced Salpeter equations and systematically explore the conditions under which these two equations give equivalent results in meson dynamics. The effects of constituent mass, angular momentum state, type of interaction, and the nature of confinement are all considered in an effort to clearly delineate the range of validity of the reduced Salpeter approximations. We find that for $J\not{\hspace*{-1.0mm}=}0$ the solutions are strikingly similar for all constituent masses. For zero angular momentum states the full and reduced Salpeter equations give different results for small quark mass especially with a large additive constant coordinate space potential. We also show that $\frac{1}{m}$ corrections to heavy-light energy levels can be accurately computed with the reduced equation.

hep-ph↗
arXiv1995

S to P wave form factors in semi-leptonic B decays

We apply HQET to semi-leptonic $B$ and $B_{s}$ meson decays into the observed charmed $P$ wave states. In order to examine the sensitivity of the results to the choice of a specific model, we perform all calculations using several different meson models, and find that uncertainty introduced by the choice of a particular model is about 30\%. Specifically, assuming $τ_{B}=1.50ps$ and $V_{cb}= 0.040$, we obtain branching ratios of $(0.27\pm 0.08)\%$ and $(0.45\pm 0.14)\%$ for $B\rar D_{1}l\barν_{l}$ and $B\rar D_{2}^{*}l\barν_{l}$ decays, respectively.

hep-ph↗
arXiv1995

Radiative rare $B$ decays revisited

We reexamine contributions of higher $K$-resonances to the radiative rare decays $b\rar sγ$ in the limit where both $b$- and $s$-quark are considered heavy. Using the non-relativistic quark model, and the form factor definitions consistent with the HQET covariant trace formalism, we find significant disagreement with previous work which also used heavy quark symmetry, and excellent agreement with experimental results. In particular, the two largest fractions of the inclusive $b\rar sγ$ branching ratio are found to be $(16.8\pm 6.4)\%$ for $B\rar K^{*}(892)γ$ and $(6.2\pm 2.9)\%$ for $B\rar K_{2}^{*}(1430)γ$ decays. We also compare the contribution from the radiative decays into the eight $K$-meson states to the inclusive experimental $b\rar sγ$ mass distribution.

hep-ph↗
arXiv1995

Modelling form factors in HQET

We present a simple and straightforward method for relating the form factors in HQET, as defined by the covariant trace formalism, to the overlaps of the rest frame wave functions of the light degrees of freedom. We also point out several inconsistencies present in recent calculations of the radiative rare $B$ decays, and also show how these can be fixed even within the framework of the non-relativistic quark model.

hep-ph↗
arXiv1995

Flux Tubes in Effective Field Theory

Quark-antiquark bound states are examined in the long-range strong-coupling limit with the minimal area law of lattice gauge theory assumed as input. Matrix element relations are established which in the effective theory obtain dynamical equations equivalent to a formulation of the flux-tube model.

hep-ph↗
arXiv1995

On the instantaneous Bethe-Salpeter equation

We present a systematic algebraic and numerical investigation of the instantaneous Bethe-Salpeter equation. Emphasis is placed on confining interaction kernels of the Lorentz scalar, time component vector, and full vector types. We explore stability of the solutions and Regge behavior for each of these interactions, and conclude that only time component vector confinement leads to normal Regge structure and stable solutions.

hep-ph↗
arXiv1995

On the Interpretation of $πN \to ππN$ Data near Threshold

Near threshold pion production experiments have been recently carried out and used to extract S--wave $ππ$ scattering lengths. We emphasize here that at present these processes are related only at the tree level (and its first correction) in chiral perturbation theory. Higher order corrections (including loops) must be evaluated before rigorous claims concerning S--wave $ππ$ scattering lengths can be made.

hep-ph↗
arXiv1995

A one parameter representation for the Isgur-Wise function

We use a $1S$ lattice QCD heavy-light wavefunction to generate a single parameter, model independent description of the Isgur-Wise function. Using recent data we find the zero-recoil slope to be $ξ'(1)= -1.16\pm 0.17$, while the second derivative turns out to be $ξ''(1)= 2.64\pm 0.74$.

hep-ph↗
arXiv1995

Observations On the Potential Confinement of a Light Fermion

We consider possible dynamical models for a light fermion confined by a potential field. With the Dirac equation only Lorentz scalar confinement yields normalizable wavefunctions, while with the ``no pair'' variant of the Dirac equation only Lorentz vector confinement has normal Regge behaviour. A systematic investigation of Regge properties and phenomenological properties is carried out, including calculations of the Isgur-Wise function. We point out that the Isgur-Wise function provides a sensitive test of confinement models. In particular, the slope of the IW function at zero recoil point is found to be $ξ'(1)\simeq -0.90$ for the Dirac equation with scalar confinement, and $ξ'(1)\simeq -1.20$ for the no pair equation with vector confinement. Using heavy-light data alone we argue against scalar confinement.

hep-ph↗
arXiv1994

Relativistic Flux Tube Model Calculation of the Isgur-Wise Function

The Relativistic Flux Tube model is used to calculate of the Isgur-Wise functions describing the exclusive semileptonic decays of $\bar{B}$ and $\bar{B}_{s}$ mesons. The light quark mass dependence is investigated and the predicted universal function agrees well with the results of lattice simulations, and with the experimental data. Recent experimental measurements of the $\bar{B}\ra D^{*}l\barν_{l}$ decay distribution yield the CKM element $V_{bc}=0.035\pm 0.001$. The IW function slope and second derivative at the zero recoil point are predicted to be $ξ'(1) = -0.93\pm 0.04$ and $ξ''(1)= 1.7\pm 0.1$ for a range of light quark massses. The importance of including higher derivatives in analyses of experiment is emphasized.

hep-ph↗
arXiv1993

Flavor Dependence of Sea Quark Structure Functions

Quark masses are shown to play an important role in the nucleon sea. Our analysis using massive QCD splitting functions demonstrates the existence of two Feynman-$x$ sea regimes. For small $x$ the strange sea is larger while at large $x$ the non-strange light sea is dominant. This crossover effect has been observed in a phenomenological analysis by the CTEQ Collaboration. We also investigate the charm component in the nucleon.

hep-ph↗