Tetraquarks in holographic QCD

Gutsche, Thomas; Lyubovitskij, Valery E.; Schmidt, Iván

doi:10.1103/physrevd.96.034030

Cited by 32 publications

(45 citation statements)

References 102 publications

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“…[315] explain the observation using the Drell-Hiida-Deck mechanism [316,317] assisted with resonant final state interactions, which can lead to one a 1 resonance to peak at different energies in the S-wave ρπ and P -wave f 0 (980)π final states. There are also works proposing the a 1 (1420) [318][319][320][321][322][323][324] to be a tetraquark resonance.…”

Section: A 1 (1420)mentioning

confidence: 99%

Threshold cusps and triangle singularities in hadronic reactions

Guo

Liu

Sakai

2020

Progress in Particle and Nuclear Physics

273

183

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The spectrum of hadrons is the manifestation of color confinement of quantum chromodynamics. Hadronic resonances correspond to poles of the S-matrix. Since 2003, lots of new hadron resonant structures were discovered in the mass regions from light mesons to hadrons containing a pair of a heavy quark and an antiquark. Many of them are candidates of exotic hadrons, and they are usually observed as peaks in invariant mass distributions. However, the S-matrix also has kinematical singularities due to the on-shellness of intermediate particles for a process, such as two-body thresholds and triangle singularities (TSs), and they can produce peaks as well. On the one hand, such singularities may be misidentified as resonances; on the other hand, they can be used as tools for precision measurements. In this paper, we review the threshold cusps and various triangle singularities in hadronic reactions, paying attention to their manifestations in phenomena related to exotic hadron candidates. * fkguo@itp.ac.cn † xiaohai.liu@tju.edu.cn ‡ shsakai@itp.ac.cn 1 The X(3872) is named χ c1 (3872) according to its quantum numbers I G (J P C ) = 0 + (1 ++ ) by the PDG [10]. Similarly, the vector charmonium-like states Y (4260) and Y (4660) mentioned below are called ψ(4260) and ψ(4660), respectively. This naming scheme does not mean that the PDG assumes them to be normal cc charmonium states. Here we follow the XY Z naming scheme that is still used in most of the relevant publications.2 A conventional explanation of the observed peaks was given in Refs. [26,27].3 region Z c (4430) [30], Z c (3900) [31,32] and Z c (4020) [33], the charged bottomonium-like structures Z b (10610) and Z b (10650) [34], and the pentaquark candidates with hidden charm P c (4312), P c (4440) and P c (4457) [35,36]. Most of these new structures were observed in the heavy-flavor sector. In particular, the heavy quarkonium-like ones are often called XY Z states in the literature due to the undetermined internal structure. On the one hand, these discoveries enlarged the known QCD spectrum to a large extent; on the other hand, they became a nice showcase of the intricate nonperturbative nature of QCD at low energies 3 : most of them fall off the expectations from quark model, which despite being just a model had provided useful guidance in classifying a large amount of hadrons into various multiplets. Therefore, they are regarded as prominent candidates of exotic hadrons. However, how the spectrum of exotic hadrons should be organized and even what types of exotic hadrons can be well defined are still unclear. Partly because of this, the observation of each of these new structures leads to different models such as compact tetraquarks (or pentaquarks), hadronic molecules, hybrid states, hadro-charmonia, and kinematic effects, etc. Nevertheless, a deeper understanding of how the hadron spectrum, in particular that of the excited hadrons above (or at least close to) strong decay thresholds, is organized can shed light on the color confinement problem of QCD. For th...

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Section: A 1 (1420)mentioning

confidence: 99%

Threshold cusps and triangle singularities in hadronic reactions

Guo

Liu

Sakai

2020

Progress in Particle and Nuclear Physics

273

183

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“…[23] within the soft-wall AdS/QCD approach, where Schrodinger-type equation for the tetraquark wave function was derived and solved analytically. The prediction for the mass of the J PC ¼ 1 þþ tetraquark state obtained there agrees with data of Ref.…”

Section: Introductionmentioning

confidence: 99%

New a1(1420) state: Structure, mass, and width

2018

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The structure, spectroscopic parameters and width of the resonance with quantum numbers J PC ¼ 1 þþ discovered by the COMPASS Collaboration and classified as the a 1 ð1420Þ meson are examined in the context of QCD sum rule method. In the calculations the axial-vector meson a 1 ð1420Þ is treated as a fourquark state with the diquark-antidiquark structure. The mass and current coupling of a 1 ð1420Þ are evaluated using QCD two-point sum rule approach. Its observed decay mode a 1 ð1420Þ → f 0 ð980Þπ, and kinematically allowed ones, namely a 1 → K ÃAE K ∓ , a 1 → K Ã0K0 and a 1 →K Ã0 K 0 channels are studied employing QCD sum rules on the light-cone. Our prediction for the mass of the a 1 ð1420Þ state m a 1 ¼ 1416

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“…In Ref. [31] we interpreted the new double charm baryon state found by the LHCb Collaboration in the invariant mass distribution of the set of final state particles (Λ + c K − π + π + ) as being at the origin of the decay chain Ξ ++ cc → Σ ++ c (→ Λ + c π + ) +K * 0 (→ K − π + ). The nonleptonic decay Ξ ++ cc → Σ ++ c +K * 0 belongs to a class of decays where the quark flavor composition is such that the decay proceeds solely via the factorizing tree-graph contribution precluding a contamination from W-exchange.…”

Section: Ibmentioning

confidence: 99%

Novel Ideas in Nonleptonic Decays of Double Heavy Baryons

et al. 2019

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The recent discovery of double charm baryon states by the LHCb Collaborarion and their high precision mass determination calls for a comprehensive analysis of the nonleptonic decays of double and single heavy baryons. Nonleptonic baryon decays play an important role in particle phenomenology since they allow to study the interplay of long and short distance dynamics of the Standard Model (SM). Further, they allow one to search for New Physics effects beyond the SM. We review recent progress in experimental and theoretical studies of the nonleptonic decays of heavy baryons with a focus on double charm baryon states and their decays. In particular, we discuss new ideas proposed by the present authors to calculate the W-exchange matrix elements of the nonleptonic decays of double heavy baryons. An important ingredient in our approach is the compositeness condition of Salam and Weinberg, and an effective implementation of infrared confinement both of which allow one to describe the nonperturbative structure of baryons composed of light and heavy quarks. Further we discuss an ab initio calculational method for the treatment of the so-called W-exchange diagrams generated by W ± boson exchange between quarks. We found that the W ± -exchange contributions are not suppressed in comparison with the tree-level (factorizing) diagrams and must be taken into account in the evaluation of matrix elements. Moreover, there are decay processes such as the doubly Cabibbo-suppressed decay Ξ + c → pφ recently observed by the LHCb Collaboration which is contributed to only by one single W-exchange diagram. ForewordThis paper is written in memory of Garry Efimov . For two of us (Mikhail Ivanov and Valery Lyubovitskij) Garry Efimov was a teacher and subsequently an important collaborator. He significantly contributed to the development of nonlocal quantum field theory and its relation to hadron structure. In particular, he showed that the nonlocal structure of hadron-quark interactions is important for a realistic description of the nonperturbative features of the strong interaction contributions at large distances. Phenomena such as hadronization and confinement can be consistently implemented in field-theoretical approaches based on nonlocal phenomenological Lagrangians. Garry Efimov with his pupils and collaborators developed a series of relativistic quark models based on nonlocal Lagrangians.

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Tetraquarks in holographic QCD

Cited by 32 publications

References 102 publications

Threshold cusps and triangle singularities in hadronic reactions

Threshold cusps and triangle singularities in hadronic reactions

New a1(1420) state: Structure, mass, and width

Novel Ideas in Nonleptonic Decays of Double Heavy Baryons

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