Charge spectra of dyonic quarks

Considering quarks as dyons, we analyze different possibilities for free fractional electric charges and monopoles to coexist. For nonvanishing vacuum angle, electric charges of dyons are not exactly fractional, but carry extra charges proportional to. The average extra charge vanishes for mesons, but not for baryons.     

Compressibility of hadrons from operator sum rules

Monopole sum rules for ar ² transition operator are discussed for baryons and mesons. From these, the energy of the compression modes can be directly related to the hadronic compressibility. From the systematics of excited hadrons the compressibility of baryons is found to be in the order of 1.3 GeV, quite close to that of mesons in the light and strange quark sector. Experiments will be very important to study the compression modes in different hadron systems.The author is indepted to the Institute of Nuclear Theory (INT Seattle) for the invitation to the program N ^* Excitations and the Structure of the Nucleon where basic ideas of the paper have been discussed. In particular, discussion with O. Bohigas, B.K. Jennings, and J. Wambach is gratefully acknowledged.     

Phenomenology of Large N c QCD

These lectures are designed to introduce the methods and results of large N _c QCD in a presentation intended for nuclear and particle physicists alike. Beginning with definitions and motivations of the approach, we demonstrate that all quark and gluon Feynman diagrams are organized into classes based on powers of 1/N _c. We then show that this result can be translated into definite statements about mesons and baryons containing arbitrary numbers of constituents. In the mesons, numerous well-known phenomenological properties follow as immediate consequences of simply counting powers of N _c, while for the baryons, quantitative large N _c analyses of masses and other properties are seen to agree with experiment, even when large N _c is set equal to its observed value of 3. Large N _c reasoning is also used to explain some simple features of nuclear interactions.     

Fragmentation production of charmed hadrons in electron-positron annihilation

Processes involving the production of D* mesons and Λ _c baryons in electron-positron annihilation at the energies of 10.58 and 91.18 GeV are considered. At the energy of 10.58 GeV, the production of pairs of B mesons that is followed by their decay to charmed particles is analyzed along with direct charm production. The violation of scaling in the respective fragmentation functions is taken into account in the next-to-leading-logarithmic approximation of perturbative QCD. The required nonperturbative fragmentation functions are extracted numerically from experimental data obtained at B factories and are approximated by simple analytic expressions. It is shown that the difference in the nonperturbative fragmentation functions for transitions to mesons and baryons can readily be explained on the basis of the quark-counting rules.     

Two relativistic effects for quarks within hadrons

Quarks within hadrons can have relativistic motions. Here the effect of making their kinetic energies fully relativistic is explored, and the light mesons are compared with the heavy mesons, as a test of flavour-independence for the quark-antiquark potential. For quarks within baryons, it is pointed out that there are important spin-orbit forces of kinematic origin, which cannot be arbitrarily put to zero, and their effects on baryon spectroscopy are illustrated for theL ^P =1^– first excited supermultiplet.Invited talk presented at the International Symposiusm "Selected Topics in Quantum Field Theory and Mathematical Physics", Bechyn, Czechoslovakia, June 14–19, 1981.     

Axial couplings and strong decay widths of heavy hadrons

We calculate the axial couplings of mesons and baryons containing a heavy quark in the static limit using lattice QCD. These couplings determine the leading interactions in heavy hadron chiral perturbation theory and are central quantities in heavy quark physics, as they control strong decay widths and the light quark mass dependence of heavy hadron observables. Our analysis makes use of lattice data at six different pion masses, 227 MeV相似文献   

A string-breaking model of heavy meson decays

Within QCD, heavy quarkonia are viewed as a quark antiquark pair bound by a narrow chromoelectric flux tube. This flux can create light quark antiquark pairs accounting for the decay into mesons with heavy quantum numbers. This model is shown to be as consistent with current data on charmonium decays intoD-meson pairs and upsilon decay to \(B\bar B\) , as is the physically less appealing³ P ₀ model.     

Isospin splittings of doubly heavy baryons

The SELEX Collaboration has reported a very large isospin splitting of doubly charmed baryons. We show that this effect would imply that the doubly charmed baryons are very compact. One intriguing possibility is that such baryons have a linear geometry Q–q–Q$Q\text{–}q\text{–}Q$ where the light quark q oscillates between the two heavy quarks Q  , analogous to a linear molecule such as carbon dioxide. However, using conventional arguments, the size of a heavy-light hadron is expected to be around 0.5 fm, much larger than the size needed to explain the observed large isospin splitting. Assuming the distance between two heavy quarks is much smaller than that between the light quark and a heavy one, the doubly heavy baryons are related to the heavy mesons via heavy quark–diquark symmetry. Based on this symmetry, we predict the isospin splittings for doubly heavy baryons including Ξ_cc${\Xi }_{cc}$, Ξ_bb${\Xi }_{bb}$ and Ξ_bc${\Xi }_{bc}$. The prediction for the Ξ_cc${\Xi }_{cc}$ is much smaller than the SELEX value. On the other hand, the Ξ_bb${\Xi }_{bb}$ baryons are predicted to have an isospin splitting as large as (6.3±1.7) MeV$(6.3\pm 1.7)\text{MeV}$. An experimental study of doubly bottomed baryons is therefore very important to better understand the structure of baryons with heavy quarks.     

Models of particle states

Two different types of particle state models are discussed. In the first type, particles are considered to be dynamically bound systems of a small set of physical constituents. In the second type, particle states are constructed from tensor products of symmetry constituents, i.e., states that are the basis elements of finite irreducible representations of an internal algebra. These states need not represent physical particles. We present three models of the first type. For the second type, we discuss in detail the main thrust of this paper, a new version of the quark-lepton model based on the algebrasu(4)_flaourXsu(6)_flavour. The quark color-triplet and a lepton color-singlet are united by a single irreducible representation of su(4)_colour. Thesu(6)_colour algebra is an extension of the originalsu(3)_flavor. All observed ground-state hadron multiplets are in full accord with the predictions of this model. The numbers of hadron ground states it predicts are 36 spin-0 mesons, 36 spin-1 mesons, 70 spin-1/2 baryons, and 56 spin-3/2 baryons.Professor Barut passed away suddenly on December 5, 1994.     

Investigation of the high-p<Subscript>T</Subscript> strange baryon anomalies at RHIC

Results from RHIC have shown that there is an enhanced baryon/meson ratio in the intermediate transverse momentum range (2<p_T<6 GeV/c) in Au+Au collisions at both  =130 and 200 GeV. This was initially demonstrated by measurements of the p̄/π^- ratio which was then extended in p_T by the Λ/K⁰ _S ratio. The data were successfully described by models utilising different hadronization mechanisms: those having recombination of quarks and others having an interplay between flow, jet quenching and incorporating baryon junction loops. The strange particle data from the first Au+Au run at  =200 GeV gave tantalising hints that the observed enhancement of baryons compared to mesons was diminished by a p_T of 6 GeV/c, but a lack of statistics in this range made a definitive statement impossible. Here we present an extended analysis of identified strange baryons and mesons in Au+Au collisions at  =200 GeV using data obtained by the STAR experiment from the 2004 running period. The increase in statistics extends the measurement of Λ hyperons out to at least 7 GeV/c and K⁰ _S mesons out to 9 GeV/c. This data allows us to place limits on the range where in-vacuum fragmentation functions are applicable and the effect of baryon dominance is reduced. We also discuss the prospects for making these measurements using multiply-strange baryons and mesons (Ω and ϕ).     

Radiative weak decay of baryons within the Bethe-Salpeter formalism

The Nishijima-Mandelstam formula for the transition amplitude of radiative weak decay of baryons is derived within the Bethe-Salpeter formalism in a manner parallel to the Lehmann-Synanzik-Zimmermann reduction procedure. Feynaman rules for bound quarks are discussed. Employing a Gaussian Bethe-Salpeter amplitude for baryons used by other authors, the transition amplitude for ⁺ p has been calculated. Due to the use of a phenomenological Bethe-Salpeter wave function, the resulting amplitude turns out to be non-gauge invariant. Gauge invariance is imposed by hand and the asymmetry parameter calculated. Normalization of the decay amplitude and calculation of the absolute rate is not attempted. Two serious problems remain in this calculation: First, the lack of gauge invariance, and, second, the calculated amplitudes turn out to be complex.     

A perturbative approach toB decays into two π mesons

The modified perturbative approach in which transverse degrees of freedom as well as Sudakov suppressions are taken into account, is applied toB decays into two mesons. The influence of various model parameters (CKM) matrix elements,B decay constant, mesonic wave functions) on the results as well as short distance corrections to the weak Hamiltonian are discussed in some detail. The perturbative contributions to theB decays yield branching ratios of the order of 10^–7–10^–6 which values are well below the upper limit for the branching ratio as measured by CLEO.Supported by the Deutsche Forschungsgemeinschaft     

Flavor mixing in the low energy hadron dynamics: Interplay of theSU f (3) breaking and theU A (1) anomaly

We extend our previous investigation about the flavor mixing or the OZI violating process in the light quark systems with the use of the generalized Nambu-Jona-Lasinio model incorporating theU _A (1) anomaly. The OZI breaking effects newly studied in the meson sector include the and meson decay constants, their couplings with nucleon as well as the masses and the mixing property of the scalar mesons. As for the baryon sector, we reexamine the strangeness content of the proton and the -N sigma term _N by taking into account the interactions between the constituent quarks. It is found that the short-range spin-spin interaction between the quarks gives anO(10 MeV)-enhancement for the theoretical value of the sigma term. Anomalous quark contents of other octet and decuplet baryons (hyperons) are also examined. It is shown that the axial anomaly induces the anomalous quark contents which are not expected in the naive quark model, while the short-range interaction between the quarks acts to suppress (enhance) the quark contents of the decuplet (octet) baryons. All the results indicate that the following picture holds systematically:m _s is so large that (i) the strangeness mixing induced by the anomaly is considerably suppressed and that (ii) the naive chiral perturbation does not work in the strange sector even in the tree level of the meson fields (largeN _c limit). The spin problem of nucleon, which is another subject related to the flavor mixing, is also examined with the use of our effective model.This paper is a modified version of the paper SUNY-NTG-89-49, RYU-THP-89-2 (August 1989)     

Hadronic three-body decays of light vector mesons

The decays of light vector mesons into three pseudoscalar mesons are calculated to leading order in the recently proposed counting scheme that is based on the hadrogenesis conjecture. Fully differential as well as integrated decay widths are presented. Since the required parameters have been fixed by other processes, the considered three-body decays are predictions of the presented approach. The decay width of the omega meson into three pions agrees very well with the experiment. The partial decay widths of the K^* into its three K channels are predicted.     

Evidence for the alpha decay of108I

A Residue Implantation Detection System has been used in conjunction with the Daresbury Recoil Mass Separator in a search for radioactivity from the unknown nuclides¹⁰⁸I and¹⁰⁵Te. In the reaction of 260 MeV⁵⁸Ni ions with a⁵⁴Fe target two new decay lines at energies of 3.730±0.025 MeV and 3.885±0.025 MeV corresponding to cross sections of approximately 0.3 b and 0.4 b respectively were identified in theA=108 region of the separator's focal plane. These decay lines are tentatively assigned to the alpha decays of¹⁰⁸I. No evidence for a proton decay branch of this nuclide could be found. In a second reaction in which a⁵⁰Cr target was bombarded with 230 MeV⁵⁸Ni ions, no alpha decay peak from¹⁰⁵Te could be identified. Cross section dependent half life limits were determined from which correspondingQ-value limits were deduced.RDP, SJB and MF would like to thank the SERC for financial support during the course of this work and all of us would like to thank the crews at Daresbury for providing the⁵⁸Ni beams.     

A new hadron spectroscopy

QCD-motivated models for hadrons predict an assortment of “exotic” hadrons that have structures that are more complex than the quark-antiquark mesons and three-quark baryons of the original quark-parton model. These include pentaquark baryons, the six-quark H-dibaryon, and tetraquark, hybrid and glueball mesons. Despite extensive experimental searches, no unambiguous candidates for any of these exotic configurations have been identified. On the other hand, a number of meson states, one that seems to be a proton-antiproton bound state, and others that contain either charmed-anticharmed quark pairs or bottom-antibottom quark pairs, have been recently discovered that neither fit into the quark-antiquark meson picture nor match the expected properties of the QCD-inspired exotics. Here I briefly review results from a recent search for the H-dibaryon, and discuss some properties of the newly discovered states -the proton-antiproton state and the so-called XY Z mesons- and compare them with expectations for conventional quark-antiquark mesons and the predicted QCD-exotic states.     

Hadrons as collective excitations of a superfluid coloured — Quark liquid

We investigate the excitation spectrum of a non-relativistic many-body system of coloured quarks in the presence of various Cooper-pair condensate fields. While the spin zeroqq colourless condensate within QCD is known to be responsible for the existence of pions, we argue non-relativistically that the spin — 1qq colourless condensate implies the existence of mesons, and the colour-tripletqq condensate implies the existence of baryons.Presented at the symposium Mesons and Light Nuclei, Bechyn, Czechoslovakia, May 7–June 1, 1985.     

The leptonic decay constants of $$\bar Qq$$ mesons and the lattice resolution

We present a high statistics study of the leptonic decay constantf _P of heavy pseudoscalar mesons using propagating heavy Wilson quarks within the quenched approximation, on lattices covering sizes from about 0.7 fm to 2 fm. Varying between 5.74 and 6.26 we observe a sizeablea dependence off _P when one uses the quark field normalization that was suggested by Kronfeld and Mackenzie, compared with the weaker depence observed for the standard relativistic norm. The two schemes come into agreement when one extrapolates toa0. The extrapolations needed to reach the continuum quantityf _B introduce large errors and lead to the valuef _B =0.18(5) GeV in the quenched approximation. This suggests that much more effort will be needed to obtain an accurate lattice prediction forf _B .work supported in part by DFG grant Schi 257/3-1