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Register a new userCharmed baryon resonances with heavy-quark symmetry
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We study charmed baryon resonances that are generated dynamically from a coupled-channel unitary approach that implements heavy-quark symmetry. Some states can already be identified with experimental observations, such as $Lambda_c(2595)$, $Lambda_c(2660)$, $Sigma_c(2902)$ or $Lambda_c(2941)$, while others need a compilation of more experimental data as well as an extension of the model to include higher order contributions. We also compare our model to previous SU(4) schemes.
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We study charmed baryon resonances which are generated dynamically within a unitary meson-baryon coupled channel model that treats the heavy pseudoscalar and vector mesons on equal footing as required by heavy-quark symmetry. It is an extension of recent SU(4) models with t-channel vector meson exchanges to a SU(8) spin-flavor scheme, but differs considerably from the SU(4) approach in how the strong breaking of the flavor symmetry is implemented. Some of our dynamically generated states can be readily assigned to recently observed baryon resonances, while others do not have a straightforward identification and require the compilation of more data as well as an extension of the model to d-wave meson-baryon interactions and p-wave coupling in the neglected s- and u-channel diagrams. Of several novelties, we find that the Lambda_c(2595), which emerged as a ND quasi-bound state within the SU(4) approaches, becomes predominantly a ND* quasi-bound state in the present SU(8) scheme.
Both unitary chiral theories and lattice QCD simulations show that the $DK$ interaction is attractive and can form a bound state, namely, $D^*_{s0}(2317)$. Assuming the validity of the heavy antiquark-diquark symmetry (HADS), the $Xi_{cc}bar{K}$ interaction is the same as the $DK$ interaction, which implies the existence of a $Xi_{cc}bar{K}$ bound state with a binding energy of $49-64$ MeV. In this work, we study whether a $Xi_{cc}Xi_{cc}bar{K}$ three-body system binds. The $Xi_{cc}Xi_{cc}$ interaction is described by exchanging $pi$, $sigma$, $rho$, and $omega$ mesons, with the corresponding couplings related to those of the $NN$ interaction via the quark model. We indeed find a $Xi_{cc}Xi_{cc}bar{K}$ bound state, with quantum numbers $J^P=0^-$, $I=frac{1}{2}$, $S=1$ and $C=4$, and a binding energy of $80-118$ MeV. It is interesting to note that this system is very similar to the well-known $NNbar{K}$ system, which has been studied extensively both theoretically and experimentally. Within the same framework, we show the existence of a $NNbar{K}$ state with a binding energy of $35-43$ MeV, consistent with the results of other theoretical works and experimental data, which serves as a consistency check on the predicted $Xi_{cc}Xi_{cc}bar{K}$ bound state.
We study the three-body anti-triplet ${bf B_c}to {bf B_n}MM$ decays with the $SU(3)$ flavor ($SU(3)_f$) symmetry, where ${bf B_c}$ denotes the charmed baryon anti-triplet of $(Xi_c^0,-Xi_c^+,Lambda_c^+)$, and ${bf B_n}$ and $M(M)$ represent baryon and meson octets, respectively. By considering only the S-wave $MM$-pair contributions without resonance effects, the decays of ${bf B_c}to {bf B_n}MM$ can be decomposed into irreducible forms with 11 parameters under $SU(3)_f$, which are fitted by the 14 existing data, resulting in a reasonable value of $chi^2/d.o.f=2.8$ for the fit. Consequently, we find that the triangle sum rule of ${cal A}(Lambda_c^+to nbar K^0 pi^+)-{cal A}(Lambda_c^+to pK^- pi^+)-sqrt 2 {cal A}(Lambda_c^+to pbar K^0 pi^0)=0$ given by the isospin symmetry holds under $SU(3)_f$, where ${cal A}$ stands for the decay amplitude. In addition, we predict that ${cal B}(Lambda_c^+to n pi^{+} bar{K}^{0})=(0.9pm 0.8)times 10^{-2}$, which is $3-4$ times smaller than the BESIII observation, indicating the existence of the resonant states. For the to-be-observed ${bf B_c}to {bf B_n}MM$ decays, we compute the branching fractions with the $SU(3)_f$ amplitudes to be compared to the BESIII and LHCb measurements in the future.
Recent data on the production of $D$ mesons and $Lambda_c^+$ baryons in heavy ion collisions at the Relativistic Heavy Ion Collider and the Large Hadron Collider exhibit a number of striking characteristics such as enhanced yield ratios $D_s^+/D^0$, $Lambda_c^+/D^0$ and their transverse momentum dependences. In this paper, we derive the momentum dependence of open charm mesons and singly charmed baryons produced in ultra-relativistic heavy ion collisions via the equal-velocity quark combination. We present analytic expressions and numerical results of yield ratios and compare them with the experimental data available. We make predictions for other charmed hadrons.
We give a systematic study of ${bf B}_cto {bf B}_n V$ decays, where ${bf B}_c$ and $ {bf B}_n$ correspond to the anti-triplet charmed and octet baryons, respectively, while $V$ stand for the vector mesons. We calculate the color-symmetric contributions to the decays from the effective Hamiltonian with the factorization approach and extract the anti-symmetric ones based on the experimental measurements and $SU(3)_F$ flavor symmetry. We find that most of the existing experimental data for ${bf B}_cto {bf B}_n V$ are consistent with our fitting results. We present all the branching ratios of the Cabbibo allowed, singly Cabbibo suppressed and doubly Cabbibo suppressed decays of ${bf B}_cto {bf B}_n V$. The decay parameters for the daughter baryons and mesons in ${bf B}_cto {bf B}_n V$ are also evaluated. In particular, we point out that the Cabbibo allowed decays of $Lambda_c^+ to Lambda^0 rho^+$ and $ Xi_c^0 to Xi^- rho^+$ as well as the singly Cabbibo suppressed ones of $Lambda_c^+ to Lambda^0 K^{*+}$, $Xi_c^+ to Sigma^+ phi$ and $Xi_c^0to Xi^- K^{*+}$ have large branching ratios and decay parameters with small uncertainties, which can be tested by the experimental searches at the charm facilities.
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