Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA possible Omega-pi molecular state
85
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The structure of Omega-pi state with isospin I=1 and spin-parity J^p=3/2^- are dynamically studied in both the chiral SU(3) quark model and the extended chiral SU(3) quark model by solving a resonating group method (RGM) equation. The model parameters are taken from our previous work, which gave a satisfactory description of the energies of the baryon ground states, the binding energy of the deuteron, the nucleon-nucleon (NN) scattering phase shifts, and the hyperon-nucleon (YN) cross sections. The calculated results show that the Omega-pi state has an attractive interaction, and in the extended chiral SU(3) quark model such an attraction can make for an Omega-pi quasi-bound state with the binding energy of about several MeV.
rate research
Read More
Inspired by the recent observation of a narrow resonance-like structure around 2360 MeV in the p+n to d + pi 0 + pi 0 cross section, the possibility of forming a NN*(1440) quasi-molecular state is investigated by using a meson exchange model in which the pi, sigma, rho and omega exchanges in t- and u-channels are considered. By adopting the coupling constants extracted from the relevant NN scattering and N*(1440) decay data, it is found that a deuteron-like quasi-molecular state of NN*(1440) with a binding energy in the range of from 2 to 67MeV can be formed. Therefore, it is speculated that the observed structure around 2360 MeV might be or may have a large component of the NN*(1440) quasi-molecular state.
Recently, a hint for dibaryon $NDelta(D_{21})$ was observed at WASA-AT-COSY with a mass about $30pm10$ MeV below the $NDelta$ threshold. It has a relatively small binding energy compared with the $d^*(2380)$ and a width close to the width of the $Delta$ baryon, which suggests that it may be a dibaryon in a molecular state picture. In this work, we study the possible $S$-wave molecular states from the $NDelta$ interaction within the quasipotential Bethe-Salpeter equation approach. The interaction is described by exchanging $pi$, $rho$, and $omega$ mesons. With reasonable parameters, a $D_{21}$ bound state can be produced from the interaction. The results also suggest that there may exist two more possible $D_{12}$ and $D_{22}$ states with smaller binding energies. The $pi$ exchange is found to play the most important role to bind two baryons to form the molecular states. An experimental search for possible $NDelta(D_{12})$ and $NDelta(D_{22})$ states will be helpful for understanding the hint of the dibaryon $NDelta(D_{21})$.
Using the production reactions $pdto {}^3mbox{He},omega$ and $ppto ppomega$, the Dalitz plot distribution for the $omega to pi^+ pi^- pi^0$ decay is studied with the WASA detector at COSY, based on a combined data sample of $ (4.408pm 0.042) times 10^4$ events. The Dalitz plot density is parametrised by a product of the $P$-wave phase space and a polynomial expansion in the normalised polar Dalitz plot variables $Z$ and $phi$. For the first time, a deviation from pure $P$-wave phase space is observed with a significance of $4.1sigma$. The deviation is parametrised by a linear term $1+2alpha Z$, with $alpha$ determined to be $+0.147pm0.036$, consistent with the expectations of $rho$-meson-type final-state interactions of the $P$-wave pion pairs.
In this note we review the role of homotopy groups in determining non-perturbative (henceforth `global) gauge anomalies, in light of recent progress understanding global anomalies using bordism. We explain why non-vanishing of $pi_d(G)$ is neither a necessary nor a sufficient condition for there being a possible global anomaly in a $d$-dimensional chiral gauge theory with gauge group $G$. To showcase the failure of sufficiency, we revisit `global anomalies that have been previously studied in 6d gauge theories with $G=SU(2)$, $SU(3)$, or $G_2$. Even though $pi_6(G) eq 0$, the bordism groups $Omega_7^mathrm{Spin}(BG)$ vanish in all three cases, implying there are no global anomalies. In the case of $G=SU(2)$ we carefully scrutinize the role of homotopy, and explain why any 7-dimensional mapping torus must be trivial from the bordism perspective. In all these 6d examples, the conditions previously thought to be necessary for global anomaly cancellation are in fact necessary conditions for the local anomalies to vanish.
Very recently, a new $Omega^{*}$ state was reported by the Belle Collaboration, with its mass of $2012.4 pm 0.7 text{(stat)}pm 0.6 text{(syst)} mathrm{MeV}$, which locates just below the $KXi^*$ threshold and hence hints to be a possible $KXi^*$ hadronic molecule. Using the effective Lagrangian approach as the same as our previous works for other possible hadronic molecular states, we investigate the decay behavior of this new $Omega^*$ state within the hadronic molecular picture. The results show that the measured decay width can be reproduced well and its dominant decay channel is predicted to be the $KpiXi$ three-body decay. This suggests that the newly observed $Omega^*$ may be ascribed as the $J^P={3/2}^-$ $KXi^*$ hadronic molecular state and can be further checked through its $KpiXi$ decay channel.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
