Double exotic state productions in pion and kaon induced reactions

In the present work, we investigate the pion/kaon induced $$P_c/P_{cs}$$ P c / P cs productions with $$Z_c$$ Z c state off proton target with an effective Lagrangian approach. Our estimations indicate that the cross sections depend on the model parameters and beam energies, in particular, the cross sections for $$\pi p \rightarrow Z_c(3900) P_c(4312)$$ π p → Z c ( 3900 ) P c ( 4312 ) and $$\pi p \rightarrow Z_c(3900) P_c(4440)$$ π p → Z c ( 3900 ) P c ( 4440 ) are similar and can reach up to 10 nb, while those for $$\pi p \rightarrow Z_c(3900) P_c(4457)$$ π p → Z c ( 3900 ) P c ( 4457 ) can be 30 nb. As for $$Kp \rightarrow Z_{cs}(3985)P_c$$ K p → Z cs ( 3985 ) P c , the cross sections are about 2.5 times smaller than those for $$\pi p \rightarrow Z_c(3900) P_c$$ π p → Z c ( 3900 ) P c . The discussed processes in the present work, especially $$\pi p \rightarrow Z_c(3900) P_c(4457)$$ π p → Z c ( 3900 ) P c ( 4457 ) process, may be accessible by the high-energy pion and kaon beams in the facilities of J-PARC and COMPASS.

Exciton Condensation in an Atomically-thin MoS2 Semiconductor

Condensation of a dilute Bose gas of excitons (coupled electron-hole pairs) in a direct bandgap semiconductor was first theoretically predicted in 19681. This exotic state of matter is expected to exhibit spectacular non-linear properties, such as superradiance and superfluidity. However, direct experimental observation of condensation of optically active excitons in conventional semiconductors has been hindered by their short lifetimes and weak collective excitonic interactions. Here, we have experimentally realized the condensation of short-lived excitons in a direct-bandgap, atomically-thin MoS2 semiconductor. The signature is the anomalous transport of the fast-expanding exciton density, originating from a thermalized dilute gas generated under the laser spot. Below the critical temperature Tc~150 K, the exciton liquid propagates over ultra-long distances (at least 60 micrometers) with record speed in a solid-state system of 1.8*10^7 m/s (~6% the speed of light), fuelled by the unconventionally strong repulsions among excitons. The condensation is controlled by many-body interactions in the gas mixture of excitons (bosons) and free-carriers (fermions) via an electrical backgate. Our results demonstrate electrostatic doping as a simple approach for the investigation of correlated states of matter at high-temperatures, excitonic circuitry and spin-valley Hall devices mediated by exciton superfluids in semiconducting monolayers.

Observation of an exotic narrow doubly charmed tetraquark

Conventional hadronic matter consists of baryons and mesons made of three quarks and quark-antiquark pairs, respectively. The observation of a new type of hadronic state, a doubly charmed tetraquark containing two charm quarks, an anti-u and an anti-d quark, is reported using data collected by the LHCb experiment at the Large Hadron Collider. This exotic state with a mass of about 3875 MeV/c 2 manifests itself as a narrow peak in the mass spectrum of D0D0π + mesons just below the D∗+D0 mass threshold. The near-threshold mass together with a strikingly narrow width reveals the resonance nature of the state.

Investigation of exotic state X(3872) in pp collisions at $$\sqrt{s}=7$$, 13 TeV

We have used the dynamically constrained phase space coalescence model to study the production of the exotic state X(3872) based on the hadronic final states generated by the parton and hadron cascade model (PACIAE) with $$|y|<1$$ | y | < 1 and $$p_T < 15.5$$ p T < 15.5 GeV/c in pp collisions at $$\sqrt{s}=7$$ s = 7 and 13 TeV, respectively. Here the X(3872) is assumed to consist of bound state $$D\bar{D^*}$$ D D ∗ ¯ , which can form three possible structures for the tetraquark state, the nucleus-like state, and the molecular state. The yields of three different structures X(3872) were predicted. The transverse momentum distribution and the rapidity distribution of three different structures X(3872) are also presented. Sizable difference can be found in the transverse momentum and rapidity distributions for the three different X(3872) structures.

Production cross sections of tetraquark states in elementary hadronic collisions

Inclusive production cross sections of the possible exotic state X(3872) in proton–proton, pion-proton and proton–antiproton collisions are calculated using a statistical based model, which is previously used to describe inclusive charmed and bottomed hadron production cross sections in the low energy region. With the extensions made here the model is capable to include tetraquarks as well, using the diquark picture of tetraquarks. The evaluated cross section ratio of $$\varPsi (2S)$$ Ψ ( 2 S ) and X(3872) at $$\sqrt{s}=7$$ s = 7 TeV agrees well with the measured value.

Gapped magnetic ground state in quantum spin liquid candidate κ-(BEDT-TTF)2Cu2(CN)3

Geometrical frustration, quantum entanglement, and disorder may prevent long-range ordering of localized spins with strong exchange interactions, resulting in an exotic state of matter. κ-(BEDT-TTF)2Cu2(CN)3 is considered the prime candidate for this elusive quantum spin liquid state, but its ground-state properties remain puzzling. We present a multifrequency electron spin resonance (ESR) study down to millikelvin temperatures, revealing a rapid drop of the spin susceptibility at 6 kelvin. This opening of a spin gap, accompanied by structural modifications, is consistent with the formation of a valence bond solid ground state. We identify an impurity contribution to the ESR response that becomes dominant when the intrinsic spins form singlets. Probing the electrons directly manifests the pivotal role of defects for the low-energy properties of quantum spin systems without magnetic order.

The study of exotic state $$Z_c^{\pm }(3900)$$ decaying to $$J/\psi \pi ^{\pm }$$ in the pp collisions at $$\sqrt{s}$$ = 1.96, 7, and 13 TeV

A dynamically constrained phase-space coalescence model and PACIAE model are used to predict the exotic resonant state $$Z_c^{\pm }(3900)$$ Z c ± ( 3900 ) yield in pp collisions at $$\sqrt{s} = 1.96, 7$$ s = 1.96 , 7 and 13 TeV, respectively, which are estimated to be around $$10^{-6}$$ 10 - 6 to $$10^{-5}$$ 10 - 5 based on the $$J/\psi \pi ^{\pm }$$ J / ψ π ± bound state in the decay chain of b hadrons. The energy dependence of the transverse momentum distributions and rapidity distributions with $$|y|<6$$ | y | < 6 and $$p_{T}<10$$ p T < 10 GeV/c are also calculated for $${Z_c^{+}(3900)}$$ Z c + ( 3900 ) and $${Z_c^{-}(3900)}$$ Z c - ( 3900 ) . The production of $${Z_c^{+}(3900)}$$ Z c + ( 3900 ) and its anti-particle $${Z_c^{-}(3900)}$$ Z c - ( 3900 ) are found to be quite similar to each other.