Christian Hambrock
An overview over recent spectroscopy results in comparison with data is given. We focus on the exotica Z_b(10610), Z_b(10650) and Y_b(10890) in the bottom sector and discuss a possible connection to the exotica in the charm sector, namely to the resonances Y_c(4260) and Z_c(3900). Furthermore, future prospects for the determination of the nature of Y_b(10890) are outlined.
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This proceeding broadly overviews the current landscape of heavy exotic spectroscopy. Such work includes the composition of certain X, Y , and Z states, and proceeds to discuss tetraquarks made exclusively of four quarks.
I will report on the recent LHCb results on the evidence for the decay $X(3872)\rightarrowψ(2S) γ$, and on the improved measurement of the mass and width of the $Z(4430)^-$, the determination of its quantum numbers and the observation of its resonant character.
The LHCb experiment is designed to study properties and decays of heavy flavored hadrons produced from $pp$ collisions at the LHC. During Run~1, it has recorded the world's largest data sample of beauty and charm hadrons, enabling precision spectroscopy studies of such particles. Several important results obtained by LHCb, such as the discovery of the first pentaquark states and the first unambiguous determination of the $Z_c(4430)^-$ as an exotic state, have dramatically increased the interest on spectroscopy of heavy hadrons. An overview of the latest LHCb results on the subject, including t…
In this talk I give a short summary of the basics of conventional and exotic meson spectroscopy, and consider in particular those issues in the charmonium and charmonium hybrid sectors which can be addressed by a future antiproton facility at GSI.
The present status of some theoretical interpretations of the atmospheric neutrino deficit is briefly discussed. Specifically, we show the results for the FC mechanism and for the standard oscillation hypothesis, both in the active and in the sterile channels. All these mechanisms are able to fit the present data to a good statistical level. Among them, the nu_mu --> nu_tau oscillation is certainly the best explanation to the atmospheric neutrino deficit, providing a remarkably good agreement with the data.
A spate of remarkable new hadrons reported in 2003 may lead to unequivocal proof of states beyond conventional $q\bar{q}$ and $qqq$ structure. Claimed baryonic states Theta+, Phi, and Theta^0_c would consist of five quarks, and new D_{sJ}-states and/or X(3872) might contain four quarks. I review efforts to search for and study this ``new'' spectroscopy in pbarp-collisions with the CDF II detector. Pentaquark searches are negative, and no evidence for exotic analogs of D_{sJ}-states was found. CDF has confirmed the X(3872). My main focus is the production and decay properties of the X(3872), an…
In addition to well-motivated scenarios like supersymmetric particles, the so-called exotic matter (quirky matter, hidden valley models, etc.) can show up at the LHC and ILC, by exploring the spectroscopy of high mass levels and decay rates. In this paper we use QCD-inspired potential models, though without resorting to any particular one, to calculate level spacings of bound states and decay rates of the aforementioned exotic matter in order to design discovery strategies. We mainly focus on quirky matter, but our conclusions can be extended to other similar scenarios.
The exotic J^{PC}= 1^{-+} resonance π_{1}(1600)is examined in the framework of the Quark Model with Constituent Gluon (QMCG). We report the possibility of interpreting that resonance as quark-antiquark-gluon hybrid meson, with a masse = 1.65+0.05-0.04 GeV and a rho-pi decay width = 0.28+0.14-0.09 GeV.
Spectroscopy at $e^+e^-$ colliders
本文回顾了在 BESIII、Belle/Belle II 等 $e^+e^-$ 对撞机上研究超出传统夸克模型的奇特类重夸克偶素态的最新实验进展。
We investigate theoretical interpretations of the 1.4 GeV J^PC exotic resonance reported by the E852 collaboration. It is argued that interpretation in terms of a hybrid meson is untenable. A K-matrix analysis shows that the 1.4 GeV enhancement in the E852 eta pi data can be understood as an interference of a non-resonant Deck-type background and a resonance at 1.6 GeV. A final state rescattering calculation shows that the 1.6 GeV hybrid has a eta pi width which is bounded above by 57 \pm 14 MeV.
Exotic Hadron Spectroscopy in Heavy-Flavor Systems
本文综述了重味强子谱学中发现的各类奇特强子态，包括隐藏粲五夸克态、带电类粲偶素结构、重夸克偶素-重夸克偶素系统中的共振态、双重重四夸克态和开味四夸克态，并讨论了这些态的系统性特征。
This talk summarizes recent developments in quarkonium spectroscopy. I comment on the relation between the Z_b(10610) and Z_b(10650) and recently observed Z_c(3900) and Z_c(4025) states. Then I discuss a number of calculations using non-relativistic effective field theory for the X(3872), Z_b(10610), and Z_b(10650), under the assumption that these are shallow molecular bound states of charm or bottom mesons.
Spectroscopy of heavy exotic mesons using lattice QCD static potentials and the Born-Oppenheimer approximation
本文利用格点QCD静态势与玻恩-奥本海默近似研究重味奇特介子，总结了$\ar{b} \ar{b} q q$四夸克态及不同同位旋底偶素的最新谱学结果。
A selected survey is presented of the recent progress in hadron spectroscopy. This includes spin-singlet charmonium states, excitations of charmonium and open-charm mesons, double-charm baryons, and pentaquark candidates. Models proposing exotic bound states or resonances are reviewed. The sector of exotic mesons with two heavy quarks appears as particularly promising.
Agreement between theoretical calculations of atomic structure and spectroscopic measurements is used to constrain possible contribution of exotic spin-dependent interactions between electrons to the energy differences between states in helium-4. In particular, constraints on dipole-dipole interactions associated with the exchange of pseudoscalar bosons (such as axions or axion-like particles, ALPs) with masses $10^{-2}~{\rm eV} \lesssim m \lesssim 10^{4}~{\rm eV}$ are improved by a factor of $\sim 100$. The first atomic-scale constraints on several exotic velocity-dependent dipole-dipole inte…
We propose a collective stringlike model of pentaquarks with the geometry of an equilateral tetrahedron in which the four quarks are located at the four corners and the antiquark in its center. The nonplanar equilibrium configuration is a consequence of the permutation symmetry of the four quarks. In an application to the spectrum of exotic Theta baryons, we find that the ground state pentaquark has angular momentum and parity J(p)=1/2(-) and a small magnetic moment of 0.382 nuclear magnetons. The decay width is suppressed by the spatial overlap with the decay products.
Recent lattice QCD results on the hadron spectroscopy with beauty and charm quarks is reviewed. The focus of the review are exotic hadrons, while non-lattice approaches and conventional hadrons are reported as well. We discuss the recently discovered $Ω_c^*$, a charmonium state with spin three, $P_c$ pentaquarks, $B_c(2S)$ and $Λ_b^*$, the long-standing challenges for theory $Z_c$, $Z_b$ and $X(3872)$, and we review predictions for yet undiscovered states $bb\bar q\bar q$, $\bar bb\bar bb$, highly excited and hybrid $\bar bb$, baryons with bottom quarks and still-missing $B_{s}$ mesons.
We propose that the recently discovered Θbaryon is a bound state of four quarks and an antiquark, containing two highly correlated ud-pairs. If so, the Θbaryon has positive parity, and it lies in an near-ideally mixed SU(3)_{f} \mathbf{\bar{10}}_{f} oplus \mathbf{8}_{f}. The Roper resonance and the P_{11}(1710) fit naturally into this classification. We predict an isospin 3/2 multiplet of Ξ's (S=-2) with J^Π=\half^{+} around 1750 MeV. A search for manifestly exotic Ξ^{+} and Ξ^{--} in this mass range could provide a sharp test of our proposal. We predict that charm and bottom analogues of the …
Since nine years experiments have been observing a host of exotic states decaying into heavy quarkonia. The interpretation of most of them still remains uncertain and, in some cases, controversial, notwithstanding a considerable progress has been made on the quality of the experimental information available and a number of ideas and models have been put forward to explain the observations. In this mini-review we will summarize the measurements, with the most recent updates, and list the useful ones yet to be done. We will discuss the problem of the spin of the X, which could hide some major su…
The Belle II experiment at the SuperKEKB energy-asymmetric $e^+e^-$ collider is an upgrade of the B factory facility at KEK in Tsukuba, Japan. The experiment began operation in 2019 and aims to record a factor of 50 times more data than its predecessor. Belle II is uniquely capable of studying the so-called "XYZ" particles: heavy exotic hadrons consisting of more than three quarks. First discovered by Belle, these now number in the dozens, and represent the emergence of a new category within quantum chromodynamics. We present recent results obtained from Belle II data, and the future prospects…
In this manuscript we study the vector - vector interaction within the hidden gauge formalism in a coupled channel unitary approach. In the sector $C=1,S=1,J=2$ we get a pole in the T-matrix around $2572$ MeV that we identify with the $D^*_{s2}(2573)$, coupling strongly to the $D^*K^*$($D^*_sϕ$($ω$)) channels. In addition we obtain resonances in other exotic sectors which have not been studied before such as $C=1,S=-1$, $C=2,S=0$ and $C=2,S=1$. This 'flavor-exotic' states are interpreted as $D^*\bar{K^*}$, $D^*D^*$ and $D^*_sD^*$ molecular states but have not been observed yet. In total we obt…
Exotic spectroscopy in a diquark model with a little help from AdS/QCD
本文借助AdS/QCD在双夸克势模型中计算了重介子、四夸克和五夸克的质量，并给出了$Qs\ar Q \ar q$和$QQ\ar Q \ar Q$四夸克态的新结果。
We use the chiral quark-soliton model to interpret five excited $Ω_c$ states recently reported by the LHCb collaboration and confirmed by Belle. We briefly recapitulate the model and its application to light baryons. We then show how the model can be extended to the case of baryons with one heavy quark. We test the model against ground state heavy baryons and then examine possible excitations. We argue that it is not possible to accommodate all five $Ω_c$'s within five parity minus excitations predicetd by the model and propose to interpret two narrowest states split by 70 MeV as pentaquarks b…
Supersymmetric Light Front Holographic QCD is a holographic theory, which not only describes the spectroscopy of mesons and baryons, but also predicts the existence and spectroscopy of tetraquarks. A discussion of the limitations of the theory is also presented.
The observation of many unexpected states decaying into heavy quarkonia has challenged the usual QQbar interpretation. One of the most studied exotic states, the X(3872), happens to be copiously produced in high-energy hadron collisions. We discuss how this large prompt production cross-section disfavors a loosely-bound molecule interpretation for this particle. This is supported by Monte Carlo simulations, and by a comparison with extrapolated light nuclei data by ALICE.
The first evidence for Quantum Chromodynamics (QCD), the theory of the strong interactions, came from the systematics of baryon and meson spectroscopy. An important early observation was the apparent absence of exotics, baryons requiring more than three quarks or mesons requiring more than quark-antiquark. Years later, QCD is well established, hadron spectroscopy has been relatively inactive, but the absence of exotics remains poorly understood. The recent observation of narrow, prominent exotic baryons has stirred up new interest in hadron spectroscopy. At present the experimental situation i…
Hadron spectroscopy represented in the past a major tool for understanding the fundamental symmetries of strong forces. More recently, the interest on this topic has been revitalized by the discovery of new quarkonium-like resonances, that do not fit in the standard picture and whose understanding could improve our mastery of quantum chromodynamics. I review here the experimental signatures of these exotic hadrons, at present and future e+e- and hadron collider experiments.
We present a spectrum of highly excited charmonium mesons up to around 4.5 GeV calculated using dynamical lattice QCD. Employing novel computational techniques and the variational method with a large basis of carefully constructed operators, we extract and reliably identify the continuum spin of an extensive set of excited states, states with exotic quantum numbers (0+-, 1-+, 2+-) and states with high spin. Calculations are performed on two lattice volumes with pion mass approximately 400 MeV and the mass determinations have high statistical precision even for excited states. We discuss the re…
Exotic Hadrons at LHCb
本文综述了LHCb探测器五年间在奇特强子谱学上的重大发现及相关唯象学解释，并探讨了2024年升级后该项目在奇特强子物理领域的研究潜力。
We explore the spectrum of excited and exotic bottomonia using lattice QCD. Highly excited states are identified with masses up to 11,000 MeV, many of which can be grouped into supermultiplets matching those of the quark model while exotic spin--parity--charge-conjugation quantum numbers $J^{PC}=0^{+-},\,1^{-+},\,2^{+-}$ that cannot be formed from $\bar{q}q$ alone are also identified. Single-meson operator constructions are used that have good $J^{PC}$ in the continuum, these are found to overlap well onto heavy quark states with $J\le4$. A continuum $J^{PC}$ is assigned to each level, based o…
We review the most recent experimental progress in the hadron spectroscopy, up to bottomonium mass. This covers the search for the J^PC=1^-+ exotic state, the states in J/psi decays, the spin-singlets of heavy quarkonium, and the charmoniumlike XYZ states.
I review highlights of recent results in quark-flavor physics and heavy-quark spectroscopy from lattice QCD, with emphasis on $B$-meson decays and excited and exotic charmonium states.
We employ the chiral quark-soliton model to describe excited baryons with one heavy quark. Identifying known charmed baryons with multiplets allowed by the model, we argue that apart from regular excitations of the ground state multiplets, some of recently reported by the LHCb collaboration narrow $Ω^{0}_{c}$ states, may correspond to the exotic pentaquarks. This interpretation can be easily verified experimentally, since exotic $Ω^{0}_{c}$ states -- contrary to the regular excitations -- form isospin triplets, rather than singlets.
I review here the most recent results about the observation and the study of hadronic bound states that do not fit well in the standard quarkonium picture. Several new states have been observed in the last few years, at B-, tau-Factories and hadron colliders. For most of them, quantum number determinations are available and allow to develop the basis of a new spectroscopy based on exotic compounds like tetraquarks or meson molecules. Nonetheless, there is still a lot of work to do to complete the picture.
A Brief Guide to Exotic Hadrons
针对现有奇异强子综述均为进阶水平的问题，本文面向领域新入门者提供奇异强子的简明介绍，重点聚焦实验研究，助力推进非微扰量子色动力学认知。
The dynamical diquark picture asserts that exotic hadrons can be formed from widely separated colored diquark or triquark components. We use the Born-Oppenheimer (BO) approximation to study the spectrum of states thus constructed, both in the basis of diquark spins and in the basis of heavy quark-antiquark spins. We develop a compact notation for naming these states, and use the results of lattice simulations for hybrid mesons to predict the lowest expected BO potentials for both tetraquarks and pentaquarks. We then compare to the set of exotic candidates with experimentally determined quantum…
I report on the state of hadronic physics and spectroscopy as reflected in contributions to the HEP2005 Europhysics Conference. Topics of interest include lattice field theory calculations of the hadron spectrum, the continuing quest to account for the proton's spin, pentaquarks, high-statistics Dalitz-plot analyses, excited charmed--strange mesons, quarkonium spectroscopy, and the new levels associated with the charmonium spectrum. I also reflect on the goals of hadronic physics and assess the current state of the art.
Two topics are briefly reviewed in this talk: the decay of flavored hadrons or quarkonium states involving a baryon--antibaryon pair, and the spectroscopy of heavy baryons containing one, two or three heavy quarks. Some prospects for exotic heavy baryons are also discussed.
The COMPASS experiment at the CERN-SPS studies the spectrum and the structure of hadrons by scattering high energy hadrons and polarised muons off various fixed targets. Recent results for the hadron programme comprise highlights from different topics. A selective overview is given and, among others, the following results are discussed. The precise determination of the pion polarisability, a long standing puzzle that has been solved now, is presented as well as measurements of radiative widths. The observation of a new narrow axial-vector state, the $a_1(1420)$, as well as deeper insights into…
In the past decade, exotic hadrons with charm and bottom flavors have been extensively studied both in experiments and in theories. In this review, we provide topical discussions by selecting $X,Y,Z$ particles, to which Belle has made important contributions. These are $X(3872)$, $Y(4260)$, $Z_c(4430)^+$, $Z_c(3900)^+$, $Z_{b}(10610)^+$ and $Z_{b}(10650)^+$. Based on the current experimental observations, we discuss those states with emphasis on hadronic molecule whose dynamics is governed by chiral symmetry and heavy-quark symmetry of QCD. We also mention briefly various interpretations and s…
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 pa…
The bottom-charmed ($B_c$) mesons are more stable than their charmonium ($c\bar c$) and bottomium ($b\bar b$) partners because they cannot annihilate into gluons. However, the low production cross-sections and signal-to-background ratios avoided until now their clear identification. The recent experimental results reported by CMS and LHCb at CERN open the possibility of having a $B_c$ spectrum as complete as the ones of charmonium and bottomonium. Motivated by this expectation, we compute bottom-charmed meson masses in the region energies in which decay meson-meson thresholds are opened, looki…
We extract to high statistical precision an excited spectrum of single-particle isoscalar mesons using lattice QCD, including states of high spin and, for the first time, light exotic JPC isoscalars. The use of a novel quark field construction has enabled us to overcome the long-standing challenge of efficiently including quark-annihilation contributions. Hidden-flavor mixing angles are extracted and while most states are found to be close to ideally flavor mixed, there are examples of large mixing in the pseudoscalar and axial sectors in line with experiment. The exotic JPC isoscalar states a…
Lattice QCD approach to study the hadronic resonances and exotic hadrons is described at an introductory level. The main challenge is that these states decay strongly via one or more decay channels, and they often lie near thersholds. Specific results for conventional and exotic hadrons are shown to illustrate the current status.
We study the spectroscopy of the states which defy conventional $c\bar{c}$ charmonium and $b\bar{b}$ bottomonium interpretation respectively, and are termed as exotic states. In August 2003 a state X(3872), was discovered [K. Abe\textit{\ et al.} (Belle Collaboration), Phys. Rev. Lett. \textbf{91}, 262001 (2003) [arXiv:hep-ex/0309032]] and in December 2007 a state Y(10890) was reported [K. F. Chen \textit{et. al.} [Belle Collaboration], Phys. Rev. Lett. \textbf{100}, 112001 (2008) [arXiv:0710.2577]. One possible interpretation of such exotic state is that they are tetraquark (diquark-antiquark…
The experiments at LHC have shown that the SUSY (exotic) bound states are likely to form bound states in an entirely similar fashion as ordinary quarks form bound states, i.e., quarkonium. Also, the interaction between two squarks is due to gluon exchange which is found to be very similar to that interaction between two ordinary quarks. This motivates us to solve the Schrödinger equation with a strictly phenomenological static quark-antiquark potential: $V(r)=-Ar^{-1}+κ\sqrt{r}+V_{0}$ using the shifted large $N$-expansion method to calculate the low-lying spectrum of a heavy quark with anti-sb…
Recent issues in heavy flavour physics are reviewed. Anomalies in charmonium, $B$, and $Υ(5S)$ decays and production are highlighted. New results concerning exotic heavy quark states are also briefly reviewed.
Probing new hadronic forces with heavy exotic atoms
本文提出利用负强子取代电子的重奇特原子精密谱学探测强子耦合新力载体，并结合两类跃迁提取核偶极极化率，给出0.1–10 MeV媒介子质量的领先限制。
Systematic study of exotic $1^{-+}$ tetraquark spectroscopy
本文基于构成夸克模型计算了 exotic $1^{-+}$ 紧致四夸克态的质量，并讨论了其衰变宽度比及可能的搜索通道，发现 $η_1(1855)$ 不太可能是紧致四夸克态。
The 1999 precision electroweak data from LEP and SLC persist in showing some slight discrepancies from the assumed standard model, mostly regarding $b$ and $c$ quarks. We show how their mixing with exotic heavy quarks could result in a more consistent fit of all the data, including two unconventional interpretations of the top quark.
Many charmonium-like and bottomonium-like $XYZ$ resonances have been observed by the Belle, Babar, CLEO and BESIII collaborations in the past decade. They are difficult to fit in the conventional quark model and thus are considered as candidates of exotic hadrons, such as multi-quark states, meson molecules, and hybrids. In this talk, we first briefly introduce the method of QCD sum rules and then provide a short review of the mass spectra of the quarkonium-like tetraquark states and the heavy quarkonium hybrids in the QCD sum rules approach. Possible interpretations of the $XYZ$ resonances ar…
Recent experimental data from BNL on the isovector J^PC =1^-+ exotic at 1.6 GeV in ρπindicate the existence of a non-quarkonium state consistent with lattice gauge theory predictions. We discuss how further experiments can strengthen this conclusion. We show that the ρπ, η'πand ηπcouplings of this state qualitatively support the hypothesis that it is a hybrid meson, although other interpretations cannot be eliminated.
In this talk I comment on some theoretical expectations for exotic light meson spectroscopy below 2 GeV and their potential interest for a future energy upgrade of DAFNE.
We perform the first model independent analysis of experimental data using Deep Neural Networks to determine the nature of an exotic hadron. Specifically, we study the line shape of the $P_c(4312)$ signal reported by the LHCb collaboration and we find that its most likely interpretation is that of a virtual state. This method can be applied to other near-threshold resonance candidates.
In this work we study the $QQ\bar{n}\bar{n}$ systems from both four--quark and meson--meson molecule formalisms, arriving to consistent conclusions when the proper bases are chosen. These states are interesting as they are thought to be found in experiments soon at LHC or RHIC. Such a source of experimental information will significantly improve our current understanding of charm spectroscopy.
The LHCb Collaboration has reported resonant activity in the channel $D^+ K^-$, identifying two components: $X_0(2900)$ with $J^P = 0^+$ at $2866 {\pm} 7$ MeV, $Γ_0=57{\pm} 13$ MeV and $X_1(2900)$ with $J^P = 1^-$ at $2904 {\pm} 7$ MeV, $Γ_1=110{\pm} 12$ MeV. We interpret the $X_0(2900)$ component as a $cs \bar u\bar d$ isosinglet compact tetraquark, calculating its mass to be $2863 {\pm} 12$ MeV. This is the first exotic hadron with open heavy flavor. The analogous $bs\bar u\bar d$ tetraquark is predicted at $6213 {\pm} 12$ MeV. We discuss possible interpretations of the heavier and wider $X_…
The current situation for vector meson spectroscopy is outlined, and it is shown that the data are inconsistent with the generally-accepted model for meson decay. A possible resolution in terms of exotic mesons is given. Although this resolves some of the issues, fresh theoretical questions are raised.
We present a generalization of the hyperspherical harmonic formalism to study systems made of quarks and antiquarks of the same flavor. This generalization is based on the symmetrization of the $N-$body wave function with respect to the symmetric group using the Barnea and Novoselsky algorithm. The formalism is applied to study four-quark systems by means of a constituent quark model successful in the description of the two- and three-quark systems. The results are compared to those obtained by means of variational approaches. Our analysis shows that four-quark systems with exotic $0^{+-}$ and…
These are the mini-proceedings of the CHARMEX workshop. The meeting focused on recent developments in charm spectroscopy, especially on the possible role of the states that do not fit into the quark model classification, the so-called exotic states. The goal of this write-up is to provide the community with a short summary of the individual talks as well as a comprehensive, up-to-date list of relevant references.
A theoretical overview of the exotic spectroscopy in the charm and beauty quark sector is presented. These states are unexpected harvest from the $e^+e^-$ and hadron colliders and a permanent abode for the majority of them has yet to be found. We argue that some of these states, in particular the $Y_b(10890)$ and the recently discovered states $Z_b(10610)$ and $Z_b(10650)$, discovered by the Belle collaboration are excellent candidates for tetraquark states $[bq][\bar{b}\bar{q}]$, with $q=u,d$ light quarks. Theoretical analyes of the Belle data carried out in the tetraquark context is reviewed…
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