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D. B. Lichtenberg

Publications and source records attributed to D. B. Lichtenberg.

13 recordsLinked to original sources
arXiv2004

Pentaquark in a supersmmetric quark-diquark model

According to QCD, there exists a broken dynamical supersymmetry between an antiquark and a diquark. This supersymmetry can be used to relate the mass of a pentaquark to the mass of an antibaryon by replacing two antiquarks in an antibaryon by two diquarks to form a pentaquark. Using this technique, we find that the mass of an exotic pentaquark with strangeness plus 1 is greater than 1.74 GeV, or at least 200 MeV larger than that of the reported $Θ^+$ pentaquark. Furthermore, there is no reason for the pentaquark to be narrow; on the contrary, it is expected to be so broad that it will be difficult to observe.

hep-ph↗
arXiv1999

Whither Hadron Supersymmetry?

A dynamically broken hadron supersymmetry appears to exist as a consequence of QCD. The reasons for the supersymmetry appear most transparently in the framework of the constituent quark model with a diquark approximation to two quarks. Applications of the supersymmetry have led to relations between meson and baryon masses and to predictions that certain kinds of exotic hadrons should not be observed. I summarize the successful applications and discuss possible future directions for this research.

hep-ph↗
arXiv1998

Spin-dependent forces between quarks in hadrons

Different mechanisms have been proposed to account for the spin-dependent interaction between quarks in ground-state hadrons. The first mechanism is the chromomagnetic interaction arising from one-gluon exchange, a second mechanism is an interaction arising from meson exchange, and a third from instanton effects. Some lattice calculations favor the first mechanism for heavy quarks and the third for light quarks. An argument is presented in favor of the one-gluon exchange mechanism. However, thus far, nobody has performed a crucial experiment that can definitively distinguish between these mechanisms.

hep-ph↗
arXiv1998

Are there quasistable strange baryons with anticharm or antibeauty?

In some models, exotic baryons with strangeness and anticharm or antibeauty should exist and even be stable against strong decay. We consider the stability of such possible exotic baryons, which in the constituent quark picture are called pentaquarks (each is composed of four quarks and an antiquark). Our model is based on diquark clustering and supersymmetry in hadrons, and assumes that the spin-dependent force between quarks arises from one-gluon exchange. In the model, a pentaquark with strangeness and anticharm can decay strongly, but an analogous pentaquark with an antibeauty quark is stable except for weak decay.

hep-ph↗
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

Quantitative corrections to mass sum rules involving baryons containing heavy quarks

Quantitative corrections are estimated to three of Franklin's sum rules involving the masses of baryons containing at least one charmed quark and to three analogous sum rules for baryons containing at least one bottom quark. The corrections arise from three-body contributions to baryon interaction energies and are calculated from a semiempirical formula for the colormagnetic contributions to baryon masses.

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↗