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R. Roncaglia

Publications and source records attributed to R. Roncaglia.

7 recordsLinked to original sources
arXiv1996

Diquark model of exotic mesons

This is a conference mostly devoted to diquarks. Although an exotic meson can in principle be composed of a diquark and an antidiquark, such an exotic is unlikely to be experimentally observable in the near future. The reason, according to the model, is that diquark-antidiquark exotics have masses well above the threshold for decay into two mesons, and are likely to have widths too large to make them observable. A possible exception is a $ u d \bar b \bar b$ exotic, but it will be a long time before such a state can be observed even if it is stable against strong decay.

hep-ph↗
arXiv1996

Diquark model of dibaryons

A diquark model previously formulated to describe exotic mesons is extended to dibaryons. In the model, dibaryons containing only light quarks are unbound. The $H$ dibaryon, consisting of $uuddss$ quarks, is unstable by about 90 MeV or more, and should decay strongly into two $Λ$ baryons. A charmed dibaryon $H_c$, composed of $uuddsc$, is unstable by about 60 MeV or more and should decay strongly into $Λ+ Λ_c$. On the other hand, we find that a bottom dibaryon $H_b$, made of $uuddsb$, may be just bound by about 10 MeV with respect to $Λ+ Λ_b$. If so, it should decay weakly into various final states with a charmed hadron. A possible two-body decay would be into $Λ+ Λ_c$.

hep-ph↗
arXiv1995

Mass sum rules for singly and doubly heavy-flavored hadrons

Regularities in the hadron interaction energies are used to obtain formulas relating the masses of ground-state hadrons, most of which contain heavy quarks. Inputs are the constituent quark model, the Feynman-Hellmann theorem, and the structure of the colormagnetic interaction of QCD. Some of the formulas can also be obtained from heavy quark effective theory or from diquark-antiquark supersymmetry. It is argued that the sum rules are more general than the model from which they are obtained. Where data exist, the formulas agree quite well with experiment, but most of the sum rules proposed provide predictions of heavy baryon masses that will be useful for future measurements.

hep-ph↗
arXiv1995

NEW FORMULAS RELATING THE MASSES OF SOME BARYONS AND MESONS

Sum rules relating the masses of ground-state baryons and mesons are obtained in a constituent quark model. The interaction is assumed to be independent of quark spins except for a spin-dependent part that can be treated as a perturbation. Where data are available, the sum rules agree with experiment to better than 1\%.

hep-ph↗
arXiv1994

Predicting the Masses of Heavy Hadrons without an Explicit Hamiltonian

There are striking regularities in the masses and mass differences of known hadrons. Some of these regularities can be understood from known general properties of the interactions of quarks without a need to specify the explicit form of the Hamiltonian. The Feynman--Hellmann theorem is one of the tools providing this understanding. If the mass regularities are exploited, predictions can be made of the masses of as yet undiscovered hadrons. In particular, it is found that the mass of the $B_c^*$ is $6320\pm 20$ MeV. Predictions concerning i) excited vector mesons, ii) pseudoscalar mesons, iii) $P$-wave mesons, and iv) ground-state spin 1/2 and 3/2 baryons are also made.

hep-ph↗
arXiv1994

A New Method to Predict Meson Masses

The Feynman--Hellmann theorem is used to show that vector meson energy eigenvalues are monotonically decreasing functions of the reduced masses of their constituent quarks. The experimental meson masses are used to put constraints on the values of quark masses and to predict the masses of some as yet undiscovered mesons. The mass of the $B_c^*$ meson is predicted to be $6320\pm 10$ MeV, and, with less precision, the masses of a number of excited vector mesons are also predicted.

hep-ph↗