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Register a new userThe strange partner of the $Z_{c}$ structures in a coupled-channels model
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The discovery of a new charged structure in the $K^+$ recoil-mass spectrum near the $D^-_s D^{*0}/D^{*-}_sD^0$ threshold, dubbed $Z_{cs}(3985)^-$, reinforce the idea that the structure of hadrons goes beyond the naive $qqq$ and the $qbar q$ structures. The existence of this state, with quark content $cbar c sbar u$, can be expected from the well-established $Z_c(3900)^pm$ and $Z_c(4020)$ states using SU(3) flavor symmetry. The $Z_c$ structures have been explained using the chiral constituent quark model in a coupled-channels calculation and, in this work, we undertake the study of the $Z_{cs}(3985)^-$ using the same model. We are able to reproduce the $K^+$ recoil-mass spectrum without any fine tuning of the model parameters. The study of the analytical structure of the S-matrix allows us to conclude that the structure is due to the presence of one virtual pole. A second state, the SU(3) flavor partner of the $Z_c(4020)$ is predicted at $sim!! 4110$ MeV/$c^2$. New states in the hidden bottom strange sector are also predicted.
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The BESIII Collaboration has observed a candidate for a $c bar c s bar u$ tetraquark $Z_{cs}$ at $(3982.5^{+1.8}_{-2.6} pm 2.1)$ MeV and width $(12.8^{+5.3}_{-4.4} pm 3.0)$ MeV, while the LHCb Collaboration has observed a $Z_{cs}$ candidate in the $jpsi K^-$ channel with mass of $(4003 pm 6 ^{+4}_{-14})$ MeV and width $(131 pm 15 pm 26)$ MeV. In this note we examine the possibility that these two states are distinct eigenstates of a mixing process similar to that which gives rise to two axial-vector mesons labeled by the Particle Data Group $K_1(1270)$ and $K_1(1400)$. The main point is that on top of a $bar c c$ pair, the $Z_{cs}$ states have the same light quark content as the $K_1$-s. In the compact tetraquark picture this implies several additional states, analogous to members of the $K_1$ nonet. These states have not yet been observed, nor are they required in the molecular approach. Thus experimental discovery or exclusion of these extra states will be a critical test for competing models of exotic mesons with hidden charm.
We study $e^{+}e^{-}$ collisions with a $pi^{+}pi^{-}pi^{0}eta_{c}$ final state using data samples collected with the BESIII detector at center-of-mass energies $sqrt{s}=4.226$, $4.258$, $4.358$, $4.416$, and $4.600$ GeV. Evidence for the decay $zcpmtorhopmetac$ is reported with a statistical significance of $3.9sigma$ with various systematic uncertainties taken into account at $sqrt{s} = 4.226$ GeV, and the Born cross section times branching fraction $sigma^{B}(EEto pimpzcpm)times BR(zcpmtorhopmetac)$ is measured to be $(48 pm 11 pm 11),rm{pb}$. The $zcpmto rhopmetac$ signal is not significant at the other center-of-mass energies and the corresponding upper limits are determined. In addition, no significant signal is observed in a search for $zcppmto rho^{pm}etac$ with the same data samples. The ratios $R_{zc}=BR(zcpmto rho^{pm} etac)/BR(zcpmto pi^{pm} jpsi)$ and $R_{zcp}=BR(zcppmto rho^{pm} etac)/BR(zcppmto pi^{pm} hc)$ are obtained and used to discriminate between different theoretical interpretations of the $zcpm$ and $zcppm$.
The extended supersymmetric SO(10) model with missing partner mechanism is studied. An intermediate vacuum expectation value is incorporated which corresponds to the see-saw scale. Gauge coupling unification is not broken explicitly. Proton decay is found to satisfy the present experimental limits at the cost of fine-tuning some parameters.
In the scenario that a dark matter (DM) is a weakly interacting massive particle, there are many possibilities of the interactions with the Standard Model (SM) particles to achieve the relic density of DM. In this paper, we consider one simple DM model where the DM candidate is a complex scalar and interacts with the SM particles via exchange of the Higgs particle and an extra quark, named bottom partner. The extra quark carries the same quantum number as the right-handed down-type quarks and has Yukawa couplings with the DM candidate and the right-handed down-type quarks. The Yukawa interactions are not only relevant to the thermal relic density of the DM, but also contribute to the flavor physics, such as the $Delta F=2$ processes. In addition, the flavor alignment of the Yukawa couplings is related to the decay modes of the extra quark. Then, we can find the explicit correlations among the physical observables in DM physics, flavor physics and the signals at the LHC. Based on the numerical analyses of the thermal relic density, the direct detection of the DM and the current LHC bounds using the latest results, we survey our predictions for the $Delta F=2$ processes. We investigate the perturbative bound on the Yukawa coupling, as well. Study of a fermionic DM model with extra scalar quarks is also given for comparison.
We construct an effective hadronic model including single heavy baryons (SHBs) belonging to the $(mathbf{3},mathbf{3})$ representation under $mbox{SU}(3)_L times mbox{SU}(3)_R$ symmetry, respecting the chiral symmetry and heavy-qaurk spin-flavor symmetry. When the chiral symmetry is spontaneously broken, the SHBs are divided into the baryons with negative parity of $bar{mathbf 3}$ representation under $mbox{SU}(3)$ flavor symmetry which is the chiral partners to the ones with positive parity of ${mathbf 6}$ representation. We determine the model parameters from the available experimental data for the masses and strong decay widths of $Sigma_c^{(ast)}$, $Lambda_c (2595)$, $Xi_c (2790)$, and $Xi_c (2815)$. Then, we predict the masses and strong decay widths of other baryons including $Xi_b$ with negative parity. We also study radiative decays of SHBs including $Omega_c^ast$ and $Omega_b^ast$ with positive parity.
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