In this talk, we review the most recent progress in the searching for the exotic hadrons, including hybrids, multi-quark states, molecules and so on. We only focus on the studies with a charmonium and one or more light mesons in the final states. This covers the X(3872), the $XYZ$ states at around 3.940 GeV, the Y(4140) and X(4350) in two-photon collisions, the $Y$ states from $ISR$ processes, and the charged $Z$ states.
D0 presents results on the hadronic production of $X(3872)$, $ψ(2S)$, $Z_c^\pm(3900)$, and the inclusive production of pentaquarks $P_c \rightarrow J/ψp$.
Recent results from the proton-proton collision data taken by the ATLAS experiment on exotic resonances are presented. A search for $J/ψp$ resonances in $Λ_{b}\rightarrow J/ψp K$ decays with large $p K$ invariant masses is reported. A search for exotic resonances in the four-muon final state is shown.
Recent results on studies of exotic hadrons at the LHCb experiment are summarised. These are the observation of new resonances decaying to J/$ψK^{+}$ and J/$ψϕ$, evidence of a J/$ψΛ$ structure and observation of excited $Ξ^{-}$ states in the $Ξ_{b}^{-}\to J/ψΛK^{-}$ decay and the study of $B_{s}^{0}\to J/ψπ^{+}π^{-}K^{+}K^{-}$ decays.
Many new exotic hadrons, that do not fit into the existing naming scheme for hadrons, have been discovered over the past few years. A new scheme is set out, extending the existing protocol, in order to provide a consistent naming convention for these newly discovered states, and other new hadrons that may be discovered in future.
We investigate the semi-inclusive production of hidden-charm exotic states, including $X(3872)$, $Z_c$, $Z_{cs}$ and the pentaquark $P_c$ states, in lepton-proton scattering processes. These hadrons are close to the thresholds of a pair of charm and anticharm hadrons, and are assumed to have hadronic molecular structure as their main components. In order to give order-of-magnitude estimates of the cross sections, we use Pythia to simulate the short-distance productions of the constituent hadrons, which then rescatter to form the exotic hadrons. The estimates for the $X(3872)$ and $Z_c(3900)^\p…
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.
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_…
Prompt and nonprompt productions of exotic multiquark states are studied using the $\sim$10.4 fb$^{-1}$ data sample collected by the D0 experiment in Tevatron $p\bar{p}$ collisions at $\sqrt{s}$ = 1.96 TeV. The recent D0 results on the prompt and nonprompt production of the $X(3872)$ and $Z_c^+(3900)$ states and the $P_c$ pentaquarks at the 4450 MeV region are reported. Signals corresponding to these states are found in the nonprompt production, whereas only the $X(3872)$ state is seen in the prompt production. The ratio of prompt to nonprompt $X(3872)$ production is about three times larger i…
Hadronisation of in-medium $c\bar c$ pairs to the exotic $X(3872)$
Tsinghua University（清华大学）；Laboratório de Instrumentação e Física Experimental de Partículas (LIP)（粒子实验仪器与物理实验室）；Instituto Superior Técnico, Universidade de Lisboa（里斯本大学高等技术学院）；Centro de Física e Engenharia de Materiais Avançados (CeFEMA)（先进材料物理与工程中心）
Starting from 2003, a large number of the so-called exotic hadrons, such as $X(3872)$ and $D_{s0}^*(2317)$, were discovered experimentally. Since then, understanding the nature of these states has been a central issue both theoretically and experimentally. As many of these states are located close to two hadron thresholds, they are believed to be molecular states or at least contain large molecular components. We argue that if they are indeed molecular states, in the way that the deuteron is a bound state of proton and neutron, then molecular states of three or more hadrons are likely, in the …
The quark model was formulated in 1964 to classify mesons as bound states made of a quark-antiquark pair, and baryons as bound states made of three quarks. For a long time all known mesons and baryons could be classified within this scheme. Quantum Chromodynamics (QCD), however, in principle also allows the existence of more complex structures, generically called exotic hadrons or simply exotics. These include four-quark hadrons (tetraquarks and hadronic molecules), five-quark hadrons (pentaquarks) and states with active gluonic degrees of freedom (hybrids), and even states of pure glue (glueb…
The standard model of particle physics is an extremely successful theory of fundamental interactions, but it has many known limitations. It is therefore widely believed to be an effective field theory that describes interactions near the TeV scale. A plethora of strategies exist to extend the standard model, many of which contain predictions of new particles or dynamics that could manifest in proton-proton collisions at the Large Hadron Collider (LHC). As of now, none have been observed, and much of the available phase space for natural solutions to outstanding problems is excluded. If new phy…
Hadron spectroscopy provides direct physical measurements that shed light on the non-perturbative behavior of quantum chromodynamics (QCD). In particular, various exotic hadrons such as the newly observed $T_{cc}^+$ by the LHCb collaboration, offer unique insights on the QCD dynamics in hadron structures. In this letter, we demonstrate how heavy ion collisions can serve as a powerful venue for hadron spectroscopy study of doubly charmed exotic hadrons by virtue of the extremely charm-rich environment created in such collisions. The yields of $T_{cc}^+$ as well as its potential isospin partners…
Tsinghua University（清华大学）；Southeast University（东南大学）；Universität Bonn, Helmholtz-Institut für Strahlen- und Kernphysik（波恩大学，亥姆霍兹辐射与核物理研究所）；Instituto de Física Corpuscular (centro mixto CSIC-UV)（粒子物理研究所（CSIC-UV联合中心））；Fudan University（复旦大学）；School of Physics, Zhengzhou University（郑州大学物理学院）
本文综述了与 $b$ 夸克相关的奇特强子（如 $Z_b$、$X_b$、$Y_b$ 态）的实验和理论研究，强调了重底夸克在理论计算中的优势，并介绍了 Belle、Belle II 和 LHCb 实验的最新成果。
The last decade of hadron spectroscopy has unveiled a wealth of states that do not have the properties expected of particles composed of two or three valence quarks. Among the most intriguing of these exotics is the $χ_{c1}(3872)$, which various models attempt to describe as a hadronic molecule, a compact tetraquark, an unexpected charmonium state, or their mixtures. To date, most experimental studies of the $χ_{c1}(3872)$ have focused on its production through $B$ meson decays. Heavy ion collisions, as well as high multiplicity $pp$ collisions, offer a new window on the properties of this poo…
Internal structure of exotic hadron candidate $f_0$(980) by using fragmentation functions
Quark Matter Research Center, Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所夸克物质研究中心）；Southern Center for Nuclear Science Theory, Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所南方核科学理论中心）；KEK Theory Center, Institute of Particle and Nuclear Studies, KEK（高能加速器研究机构粒子与核研究本部理论中心）
