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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:21 |
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Conference: Bucharest University Faculty of Physics 2001 Meeting
Section: Nuclear and Elementary Particles Physics
Title:
Colour-spin interactions and colour three-body forces in QCD and hadrons spectroscopy
Authors:
Ionel Lazanu
Affiliation:
Faculty of Physics, University of Bucharest
E-mail
Keywords:
Abstract:
The spectrum and interactions of hadrons present regularities, which can be correlated with simple symmetry properties of the fundamental quark and gluon interactions.
Historically, many of the hadron spectra and their properties are explained considering effects of flavour - spin interactions as . The colour interactions are included in the frame of group with the imposed condition to obtain colour singlet states for the hadrons as real particles. Thus the state function may be written as:
In reality, one gluon exchange between quarks is the simplest interaction mechanism that can be imagined in relation with QCD. In this physical field, the spin-dependent part of this interaction, in the lowest state of some unspecified mean field, represent the generalisation of the classical Breit interaction. It is summarised by an effective Hamiltonian acting on the quark`s spin and colour quantum number,
where are the spin and colour operators of the i (j)-th quark.
Based of the colour - spin interaction, the state function of the hadron (in the particular case of S-wave) can be expressed as:
and many qualitative and quantitative features of the hadron spectra can be explained or predicted in a different manner in rapport with the `standard` flavour - spin interaction. The colour three-body forces included in the interaction permit a correct ordering of the colour states; the singlet colour states are the lowest, the next lying the octet states and higher the decuplet.
In this one gluon exchange phenomenology, the only fundamental baryons multiplets allow are and respectively , where -plet is the lowest in mass and is more stable than the -plet, the next. The most attractive colour-spin channel, the multiplet, is not a physical state because it does not contain a colour singlet. The predictions about the existence and physical characteristics of the multiquark hadrons (dibaryons, pentaquarks and exotic scalar mesons) are also done.
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