Resonances in QCD

Multiquark resonances are undoubtedly experimentally observed. The number of states and the amount of details on their properties have been growing over the years. It is very recent the discovery of two pentaquarks and the confirmation of four tetraquarks, two of which had not been observed before. We mainly review the theoretical understanding of this sector of particle physics phenomenology and present some considerations attempting a coherent description of the so called X and Z resonances. The prominent problems plaguing theoretical models, like the absence of selection rules limiting the number of states predicted, motivate new directions in model building. Data are reviewed going through all of the observed resonances with particular attention to their common features and the purpose of providing a starting point to further research.

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“…Prospects for future searches have been recently exposed in [296,297]. X(3872) to stress its mysterious nature.…”

Section: A Travel Guide To Experimental Resultsmentioning

confidence: 99%

Multiquark resonances

2017

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“…have calculated the contribution of radiative interaction in the decay of singly charmed baryons. The future experiments at J-PARC,P AN DA [40,41,42,43,44] and LHCb are expected to give further information on charmed baryons.…”

Section: Introductionmentioning

confidence: 99%

Decay properties of singly charmed baryons

2018

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The magnetic moments, transition magnetic moments and the radiative decay widths of singly charmed baryons are calculated with J P = 1 2 + and J P = 3 2 + in the constitute quark model. Further, the strong decay rates for S, P and D wave transitions are also presented. The singly charmed baryon masses used in the calculations were obtained from the hypercentral Constitute Quark Model (hCQM) without and with first order relativistic correction. Obtained results are compared with experimental observation as well as with the other theoretical predictions.

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“…Many nucleon resonances, referred as N * , have been observed [1], the properties of nucleon resonances are the important issues in hadron physics, and attract lots of attentions [2][3][4]. For the nucleon resonances with masses below 2 GeV, their properties have been widely investigated in literature.…”

Section: Introductionmentioning

confidence: 99%

Study on the reaction of γp→f1(1285)p in Regge-effective Lagrangian approach

et al. 2017

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The production of the f1(1285) resonance in the reaction of γp → f1(1285)p is investigated within a Regge-effective Lagrangian approach. Besides the contributions of the t-channel ρ and ω trajectories exchanges, we also take into account the contributions of s/u-channel N (2300) terms, s/u-channel nucleon terms, and the contact term. By fitting to the CLAS data, we find that the s-channel N (2300) term plays an important role in this reaction. We predict the total cross section for this reaction, and find a clear bump structure around W = 2.3 GeV, which is associated with the N (2300) state. The reaction of γp → f1(1285)p could be useful to further study of the N (2300) experimentally.PACS numbers: 13.60. Le, 14.20.Gk, 11.10.Ef I. INTRODUCTIONIt has been known that the nucleon is a bound state of three valence quarks since 1970s. Many nucleon resonances, referred as N * , have been observed [1], the properties of nucleon resonances are the important issues in hadron physics, and attract lots of attentions [2][3][4]. For the nucleon resonances with masses below 2 GeV, their properties have been widely investigated in literature. However, the current knowledge on the properties of excited nucleon states with masses above 2 GeV is scarce. On the other hand, many missing N * s, predicted by the constituent quark models are not yet found [5].Recently, the CLAS Collaboration has measured the f 1 (1285) meson for the first time in photoproduction from a proton target, and presented the f 1 (1285) differential photoproduction cross section into ηπ + π − final states from the threshold up to a center-of-mass (c.m.) energy of W = 2.8 GeV [6]. A cross section comparison for γp → η ′ (958)p → ηπ + π − p and γp → f 1 (1285)p → ηπ + π − p at W = 2.55 GeV in Fig. 10 of Ref. [6] shows that the η ′ (958) cross section exhibits much stronger tand u-channel signatures in the angle dependence than dose the one of f 1 (1285), which is quite flat. This may imply that the f 1 (1285) photoproduction mechanism is not dominated alone by t-channel production processes.Before the experimental study on γp → f 1 (1285)p [6], there are several theoretical works on this reaction. Within the Regge-model, considering the exchanges of t-channel ρ and ω trajectories, Kochelev et al. calculated the differential cross sections of γp → f 1 (1285)p [7]. Comparison of the Regge-model calculations and the CLAS data shows the t-channel production process alone does not reproduce the CLAS measurements.

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Resonances in QCD

Cited by 31 publications

References 59 publications

Multiquark resonances

Multiquark resonances

Decay properties of singly charmed baryons

Study on the reaction of γp→f1(1285)p in Regge-effective Lagrangian approach

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