Searcharxiv⌕ Search

arXiv subjects

J. Koponen

Publications and source records attributed to J. Koponen.

65 records · Page 4Linked to original sources
arXiv2004

Excited S- and P-wave B mesons from the lattice

The energies of different angular momentum states of a heavy-light meson were measured on a lattice in Michael and Peisa, Phys. Rev. D 58, 34506 (1998). We have now repeated this study using several different lattices, quenched and unquenched, that have different physical lattice sizes, clover coefficients and quark-gluon couplings. The heavy quark is taken to be infinitely heavy, whereas the light quark mass is approximately that of the strange quark. By interpolating and extrapolating in the light quark mass we can thus compare the lattice results with B and B_s meson experiments. Most interesting is the lowest P-wave B_s state, since it is possible that it lies below the $BK$ threshold and hence is very narrow. Unfortunately, there are no experimental results on P-wave B or B_s mesons available at present. In addition to the energy spectrum, we measured earlier also vector (charge) and scalar (matter) radial distributions of the light quark in the S-wave states of a heavy-light meson on a lattice (Phys. Rev. D 65, 014512 (2002) and Eur. Phys. J. C 28, 79 (2003)). Now we are extending the study of radial distributions to P-wave states.

hep-lat↗
arXiv2003

Excited B mesons from the lattice

We determine the energies of the excited states of a heavy-light meson $Q\bar{q}$, with a static heavy quark and light quark with mass approximately that of the strange quark from both quenched lattices and with dynamical fermions. We are able to explore the energies of orbital excitations up to L=3, the spin-orbit splitting up to L=2 and the first radial excitation. These $b \bar{s}$ mesons will be very narrow if their mass is less than 5775 MeV -- the $BK$ threshold. We investigate this in detail and present evidence that the scalar meson (L=1) will be very narrow and that as many as 6 $b \bar{s}$ excited states will have energies close to the $BK$ threshold and should also be relatively narrow.

hep-lat↗
arXiv2003

Energy spectrum of a Heavy-Light meson

The energies of different angular momentum states of a heavy-light meson were measured on a lattice by Michael and Peisa in Phys. Rev. D 58, 34506 (1998). We have now repeated this study using a larger, quenched lattice to check that there the finite size effects are under control. Also the effect of quenching is studied by using dynamical fermion configurations. In the latter case the lattice spacing a is smaller, which allows one to make an estimate of a -> 0 corrections. The new measurements confirm the earlier calculated energy spectrum. From some theoretical considerations it is expected that, for high angular momentum states, the multiplets should be inverted compared with the Coulomb spectrum, i.e. L- should lie higher than L+ (see H. J. Schnitzer Phys. Lett. B 226, 171 (1989)). This happens when a pure scalar confining potential is present. Here the notation L+(-) means that the light quark spin couples to angular momentum L giving the total j=L+/- 1/2. Experimentally this inversion is not seen for P-wave mesons, and lattice measurements now suggest that there is no inversion in the D-wave either. Indeed we find that the spin-orbit splitting is very small for both values L=1 and 2. This almost exact cancellation need not be a coincidence, and could probably be understood by using straightforward symmetry arguments (P.R. Page, T. Goldman and J.N. Ginocchio, Phys. Rev. Lett. 86, 204 (2001)).

hep-lat↗
arXiv2002

The measurement, fitting and interpretation of the radial distributions of Heavy-Light mesons calculated on a lattice with dynamical fermions

In our earlier work, the charge and matter radial distributions of heavy-light mesons were measured on a 16^3 times 24 lattice with a lattice spacing of a = 0.17 fm and a light quark mass about that of the strange quark. Several major improvements have now been made: 1) Dynamical fermions are used with a approximately 0.14 fm; 2) More gauge configurations are included (78 vs 20); 3) Off-axis, in addition to on-axis, insertions are made; 4) The data analysis is much more complete. In particular, distributions involving excited states are extracted.

hep-lat↗
arXiv2002

The radial distributions of a heavy-light meson on a lattice

In an earlier work, the charge (vector) and matter (scalar) radial distributions of heavy-light mesons were measured in the quenched approximation on a 16^3 times 24 lattice with a quark-gluon coupling of 5.7, a lattice spacing of 0.17 fm, and a hopping parameter corresponding to a light quark mass about that of the strange quark. Several improvements are now made: 1) The configurations are generated using dynamical fermions with a quark-gluon coupling of 5.2 (a lattice spacing of 0.14 fm); 2) Many more gauge configurations are included (78 compared with the earlier 20); 3) The distributions at many off-axis, in addition to on-axis, points are measured; 4) The data-analysis is much more complete. In particular, distributions involving excited states are extracted. The exponential decay of the charge and matter distributions can be described by mesons of mass 0.9+-0.1 and 1.5+-0.1 GeV respectively - values that are consistent with those of vector and scalar qqbar-states calculated directly with the same lattice parameters.

hep-lat↗
arXiv2002

The Charge and Matter radial distributions of Heavy-Light mesons calculated on a lattice with dynamical fermions

A knowledge of the radial distributions of quarks inside hadrons could lead to a better understanding of the QCD description of these hadrons and possibly suggest forms for phenomenological models. As a step in this direction, in an earlier work, the charge (vector) and matter (scalar) radial distributions of heavy-light mesons were measured in the quenched approximation on a 16^3x24 lattice with a lattice spacing of 'a' approx. 0.17 fm, and a hopping parameter corresponding to a light quark mass about that of the strange quark. Here several improvements are now made: 1) The configurations are generated using dynamical fermions with a approx 0.14 fm; 2) Many more gauge configurations areincluded; 3) The distributions at many off-axis, in addition to on-axis, points are measured; 4) The data analysis is much more complete. In particular, distributions involving excited states are extracted. The exponential decay of the charge and matter distributions can be described by mesons of mass 0.9 +- 0.1 and 1.5 +- 0.1 GeV respectively -- values that are consistent with those of vector and scalar $q\bar{q}$-states calculated directly with the same lattice parameters.

hep-lat↗
arXiv2001

Radial Correlations between two quarks

In nuclear many-body problems the short-range correlation between two nucleons is well described by the corresponding correlation in the {two}-body problem. Therefore, as a first step in any attempt at an analogous description of many-quark systems, it is necessary to know the two-quark correlation. With this in mind, we study the light quark distribution in a heavy-light meson with a static heavy quark. The charge and matter radial distributions of these heavy-light mesons are measured on a lattice with a light quark mass about that of the strange quark. Both distributions can be well fitted upto r approx 0.7 fm with the exponential form w_i^2(r), where w_i(r)=A exp(-r/r_i). For the charge(c) and matter(m) distributions r_c approx 0.32(2) fm and r_m \approx 0.24(2) fm. We also discuss the normalisation of the total charge (defined to be unity in the continuum limit) and matter integrated over all space, finding 1.30(5) and 0.4(1) respectively for a lattice spacing approx 0.17 fm.

hep-lat↗
arXiv2001

The Charge and Matter radial distributions of Heavy-Light mesons calculated on a lattice

For a heavy-light meson with a static heavy quark, we can explore the light quark distribution. The charge and matter radial distributions of these heavy-light mesons are measured on a 16^3 * 24 lattice at beta=5.7 and a hopping parameter corresponding to a light quark mass about that of the strange quark. Both distributions can be well fitted up to 4 lattice spacings (r approx 0.7 fm) with the exponential form w_i^2(r), where w_i(r)=A exp(-r/r_i). For the charge(c) and matter(m) distributions r_c approx 0.32(2) fm and r_m approx 0.24(2) fm. We also discuss the normalisation of the total charge and matter integrated over all space, finding 1.30(5) and 0.4(1) respectively.

hep-lat↗
arXiv2000

The radial wavefunctions of a heavy-light meson calculated on a lattice

A brief review is given of attempts to understand the energies of four-quark systems calculated on a lattice in terms of nuclear-physics-inspired many-body techniques involving interquark potentials. Results are given for the next stage of this study where the wavefunctions of heavy-light mesons are also calculated on a lattice.

hep-lat↗
arXiv1999

A variational fit to the lattice energy of two heavy-light mesons

Recent lattice calculations on the interaction energy of two heavy-light mesons (Q^2\bar{q}^2) are interpreted in terms of the potential of the corresponding single heavy-light meson (Q\bar{q}). This model leads to a large overestimate of the binding compared with the lattice data -- unless the basic Q\bar{q} potential is modified to become a four-quark potential.

hep-ph↗