Electroproduction of lightest nucleon resonances up to Q*2=12 GeV*2 in quark models at light front

Obukhovsky, I. T.; Faessler, Amand; Gutsche, Th.; Fedorov, D. K.; Lyubovitskij, Valery E.

doi:10.1051/epjconf/201713804003

Cited by 1 publication

(1 citation statement)

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“…Previously we have used another important ingredient of our approach -the hadron molecule model [18,51,63], which allows to represent effectively a hadronic component of the resonance. The corresponding technique has been firstly sugested and thereafter developed in Refs.…”

Section: Results and Conclusionmentioning

confidence: 99%

Transition form factors and helicity amplitudes for electroexcitation of negative and positive parity nucleon resonances in a light-front quark model

et al. 2019

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A workable basis of quark configurations s 3 , s 2 p and sp 2 at light front has been constructed to describe the high-Q 2 behavior of transition form factors and helicity amplitudes in the electroproduction of the lightest nucleon resonances, N 1/2 − (1535) and N 1/2 + (1440). High-quality data of the CLAS Collaboration are described in the framework of a model which takes into account mixing of the quark configurations and the hadron-molecular states. The model allows for a rough estimate of the quark core weight in the wave function of the resonance in a comparison with high momentum transfer data on resonance electroproduction. I. INTRODUCTIONNew data on the electroproduction of low-lying nucleon resonances (J P = 1 2 ± , 3 2 ± , 5 2 ± ) at large momentum transfer provide important complementary information on the inner structure of hadron resonances [1]- [13]. These data provide evidence in support of the dominance of quark degrees of freedom in the process of electroproduction and allow to evaluate the weight of the quark component in the resonance wave function. The resonance spectrum is remarkably consistent with the quark-model predictions [14], but the traditional quark model refers only to the rest frame, whereas processes at large momentum transfer require a description of baryons in the moving frame. There are many theoretical approaches to the problem which start from the first principles [15]-[35], e.g., light-front QCD [15], lattice QCD [16], quark models [17]-[20], light-cone sum rules [21], approaches based on solution of Dyson-Schwinger and Bethe-Salpeter equations [22, 23], approaches based on chiral dynamics [24], AdS/QCD [26]-[35].The LF wave functions have the advantage that they undergo interaction-independent transformations under the action of "front boosts". In the front form of dynamics [36] the generators of front boosts are kinematical and the front boosts itself are elements of a kinematical subgroup of the Poincaré group. The price to pay is that the space rotations are not kinematical transformations. The light front t−z = 0 is not invariant under space rotations except for rotations about the z axis. Thus the generators of rotations should depend on the interaction given at the light front. By contrast, in the instant form of dynamics the "instant" (t = 0), or canonical, boosts depend on the interaction and do not generate a kinematical subgroup. Then the rotation group (together with the spatial translation group) can be considered as a kinematical subgroup of the Poincaré group.In spite of difficulties associated with the rotational symmetry, the LF approach to the description of the transition form factors implies the construction of a good basis of quark configurations possessing definite values of the orbital (L) and total (J = L + S) angular momenta and satisfying the Pauli exclusion principle. The challenge has been to modify the standard shell-model (normally harmonic oscillator) basis to describe the LF three-quark configurations with simple properties about the relativi...

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Section: Results and Conclusionmentioning

confidence: 99%