Coupled-channel Effects Research Articles

Relativistic Dirac analyses of proton scattering from $$^{92}{\text {Zr}}$$

Relativistic coupled channel analyses based on the Dirac equation are presented for polarized 800-MeV proton inelastic scatterings from an axially symmetric deformed nucleus $$^{92}{\text {Zr}}$$ by using an optical potential model and the first-order collective model. The sequential iteration method using a computer program is employed to solve the complicated Dirac coupled channel equations. The optical potential parameters of the Woods–Saxon shape and the deformation parameters of several low-lying excited states are determined phenomenologically and analyzed. The coupled channel effect between the excited states that belong to the ground-state rotational band is investigated.

Evaporation residue cross section in the Cl37+Zn68 fusion reaction near the Coulomb barrier

Background: The measured subbarrier fusion cross sections in heavy-ion reactions are found to be significantly large as compared with those expected from the one-dimensional barrier penetration model (1d-BPM). Although attempts have been made to comprehend the enhancement in terms of different intrinsic degrees of freedom of the colliding nuclei, a clear understanding of the same is yet to come.Purpose: The objectives of this study is to understand the interplay of the channel coupling effect on fusion excitation function and explore the decay dynamics of the excited compound nucleus in the sub-and-near barrier region.Method: Fusion excitation function has been measured at energies from 7% below to 38% above the Bass barrier using a recoil mass spectrometer. Furthermore, cross sections of the different evaporation residues, such as 98, 99, 100, and 101 u, have been extracted.Results: The observed enhancement in the subbarrier fusion cross sections over the 1d-BPM predictions has been explained by considering the low-lying inelastic excitations among the interacting partners using ccfull code and by the barrier modification using the dynamical cluster-decay model (DCM). The cross sections of individual residual mass fractions (98, 99, 100, and 101 u) have been compared with the Hauser-Feshbach model.Conclusion: Coupled-channel calculations and DCM have successfully explained the total fusion cross sections data. The measured total fusion cross section ${\ensuremath{\sigma}}_{\mathrm{fus}}$ was found to be approximately equal to the sum of various residual mass fractions ($\mathrm{\ensuremath{\Sigma}}{\ensuremath{\sigma}}_{\mathrm{ER}}$) at energies above the Bass barrier. One-dimensional barrier height and radius parameters extracted from the measured data are in good agreement with the Bass model and DCM parameters.

Exotic double-charm molecular states with hidden or open strangeness and around 4.5∼4.7 GeV

In this work, we investigate the interactions between the charmed-strange meson ($D_s, D_s^{*}$) in $H$-doublet and the (anti-)charmed-strange meson ($D_{s1}, D_{s2}^{*}$) in $T$-doublet, where the one boson exchange model is adopted by considering the $S$-$D$ wave mixing and the coupled-channel effects. By extracting the effective potentials for the discussed $H_s\bar{T}_s$ and $H_s{T}_s$ systems, we try to find the bound state solutions for the corresponding systems. We predict the possible hidden-charm hadronic molecular states with hidden strangeness, i.e., the $D_s^{*}\bar D_{s1}+c.c.$ states with $J^{PC}$=$0^{--}, 0^{-+}$ and the $D_s^{*}\bar D_{s2}^{*}+c.c.$ states with $J^{PC}$=$1^{--}, 1^{-+}$. Applying the same theoretical framework, we also discuss the $H_s T_s$ systems. Unfortunately, the existence of the open-charm and open-strange molecular states corresponding to the $H_s T_s$ systems can be excluded.

Probing hidden-charm decay properties of Pc states in a molecular scenario

The ${P}_{c}(4312)$, ${P}_{c}(4440)$, and ${P}_{c}(4457)$ observed by the LHCb collaboration are very likely to be $S$-wave ${\mathrm{\ensuremath{\Sigma}}}_{c}{\overline{D}}^{(*)}$ molecular candidates due to their near threshold character. In this work, we study the hidden-charm decay modes of these ${P}_{c}$ states, ${P}_{c}\ensuremath{\rightarrow}J/\ensuremath{\psi}p({\ensuremath{\eta}}_{c}p)$, using a quark interchange model. The decay mechanism for the ${P}_{c}\ensuremath{\rightarrow}J/\ensuremath{\psi}p({\ensuremath{\eta}}_{c}p)$ processes arises from the quark-quark interactions, where all parameters are determined by the mass spectra of mesons. We present our results in two scenarios. In scenario I, we perform the dynamical calculations and treat the ${P}_{c}$ states as pure ${\mathrm{\ensuremath{\Sigma}}}_{c}{\overline{D}}^{(*)}$ molecules. In scenario II, after considering the coupled channel effect between different flavor configurations ${\mathrm{\ensuremath{\Sigma}}}_{c}^{(*)}{\overline{D}}^{(*)}$, we calculate these partial decay widths again. The decay patterns in these two scenarios can help us to explore the molecular assignment and the inner flavor configurations for the ${P}_{c}$ states. In particular, the decay widths of $\mathrm{\ensuremath{\Gamma}}({P}_{c}(4312)\ensuremath{\rightarrow}{\ensuremath{\eta}}_{c}p)$ are comparable to the $J/\ensuremath{\psi}p$ decay widths in both of these two scenarios. Future experiments like LHCb may confirm the existence of the ${P}_{c}(4312)$ in the ${\ensuremath{\eta}}_{c}p$ channel.

Theoretical photoionization study of Ti9+ion

Photoionization (PI) of the Ti9+ion is investigated using the Dirac R-matrix method. Multi-configuration Dirac–Fock (MCDF) calculations are performed to construct accurate target functions. Good agreement of energy levels and radiative transition rates indicate the accuracy of target functions. PI cross sections show good consistency between length and velocity forms. The results are consistent with the previous theoretical values in high-energy regions. Partial waves’ contribution to the total PI cross sections are discussed for the GS and MS. Moreover, the PI cross sections are dominated by many resonance structures and affected by the channel coupling effects in the low-energy region. In addition to providing data for the Opacity Project TOPbase, the present work promotes plasma simulation and diagnosis.

Study on device reliability for P-type FinFETs with different fin numbers

In this work, both channel coupling effect and compressive stress were found to influence the performance and reliability for p-type FinFET. With fin number increasing, the carrier density in the channel is reduced due to the coupling effect between the neighboring fins. On the other hand, with the enlarging of the area of contact etch stop layer (CESL) due to fin number increasing, hole mobility is enhanced because of active surface area (SA) induced compressive stress. As a result, multi-fin FinFET device with more fins shows lower normalized drain current due to reduced carrier density, and worse reliability could also be observed because of hotter carriers in the channel.

Reanalysis of the most strange dibaryon within constituent quark models

The most strange dibaryon $\Omega\Omega$ with quantum numbers $S=-6$, $I=0$, and $J^{P}=0^{+},~1^{-},~2^{+},~3^{-}$ is reanalyzed in the framework of quark delocalization color screening model (QDCSM) and chiral quark model (ChQM). The $\Omega\Omega$ dibaryon with $J^{P}=0^{+}$ is bound, and the one with other quantum numbers $J^{P}=1^{-},~2^{+},~3^{-}$ are all unbound in our calculation. The low-energy scattering phase shifts, the scattering length, and the effective range of the $\Omega\Omega$ dibaryon with $J^{P}=0^{+}$ also support the existence of such strange dibaryon. This dibaryon is showed to be a shallow bound state in QDCSM, while the binding energy becomes much larger in the ChQM by including the effect of the hidden-color channel coupling. And the scalar nonet meson-exchange in the ChQM also provides more attraction for the $\Omega\Omega$ system. Experimental search for such most strange dibaryon will provide much information for understanding the hadron-hadron interactions in different quark models.

Probing new types of Pc states inspired by the interaction between an S -wave charmed baryon and an anticharmed meson in a T¯ doublet state

Inspired by the observations of three $P_c$ states, we systematically investigate interactions between an $S$-wave charmed baryon $\mathcal{B}_{c}^{(*)}=\Lambda_c/\Sigma_c/\Sigma_c^{*}$ and an anticharmed meson $\bar T=\bar D_1/\bar D_2^*$ with the one-pion-exchange potential model and the one-boson-exchange potential model, and search for possible new types of $P_c$ states with the structures of $\mathcal{B}_{c}^{(*)}\bar T$. Both $S$-$D$ wave mixing and coupled channel effects are considered. Our results suggest that in some $\mathcal{B}_{c}^{(*)}\bar T$ systems there are ideal candidates of new types of $P_c$ states, i.e., the $\Sigma_c\bar{D}_1$ state with $I(J^P)=1/2(1/2^+)$, the $\Sigma_c\bar{D}_2^*$ state with $I(J^P)=1/2(3/2^+)$, the $\Sigma_c^*\bar{D}_1$ state with $I(J^P)=1/2(1/2^+)$, and the $\Sigma_c^*\bar{D}_2^*$ states with $I(J^P)=1/2(1/2^+, 3/2^+)$, and we suggest that these predicted new types of $P_c$ states can be detected in the process $\Lambda_b^0 \to \psi(2S) p \pi^{-}$. Meanwhile, we also extend our study to the interactions between an $S$-wave charmed baryon and a charmed meson in a $T$ doublet, and we predict a series of double-charm molecular pentaquarks.

Possible molecular states composed of doubly charmed baryons with coupled-channel effect

We systematically investigate the possible molecular states composed of (1) two spin-$\frac{3}{2}$ doubly charmed baryons, and (2) a pair of spin-$\frac{3}{2}$ and spin-$\frac{1}{2}$ doubly charmed baryons. The one-boson-exchange (OBE) model is used to describe the potential between two baryons. The channel mixing effect is considered for the systems with the same quantum number $(I(J^P))$ but different total spin ($S$) and orbital angular momenta ($L$). We also study the channel mixing effect among the systems composed of various doubly charmed baryons if they have the same quantum number. Many of the systems are good candidates of molecular states.

Coupled channels calculation of fusion reaction for selected medium systems

This study focuses on using a semi-classical and quantum mechanical approach based originally on the theory of Winther and Alder that is used to explain the Coulomb excitation. This approach is called the coupled channels with continuum-discretised (CCCD), where the semi-classical and quantum models were used to investigate the channel coupling effects on the determination of the cross section for fusion σfus (mb) and the distribution of the fusion barrier Dfus (mb/MeV) for systems 14N+59Co, 16O+64Ni and 18O+64Ni. The comparison between the results of the semi-classical and quantum mechanical models along with the corresponding experimental data shows clearly that the adopted semi-classical model is very competitive to the quantum mechanical model and can be considered as efficient approach to study the properties of the fusion reactions.

Ne20+Ge76 elastic and inelastic scattering at 306 MeV

Background: Double charge exchange (DCE) nuclear reactions have recently attracted much interest as tools to provide experimentally driven information about nuclear matrix elements of interest in the context of neutrinoless double-beta decay. In this framework, a good description of the reaction mechanism and a complete knowledge of the initial and final-state interactions are mandatory. Presently, not enough is known about the details of the optical potentials and nuclear response to isospin operators for many of the projectile-target systems proposed for future DCE studies. Among these, the 20Ne + 76Ge DCE reaction is particularly relevant due to its connection with 76Ge double-beta decay. Purpose: We intend to characterize the initial-state interaction for the 20Ne + 76Ge reactions at 306 MeV bombarding energy and determine the optical potential and the role of the couplings between elastic channel and inelastic transitions to the first low-lying excited states. Methods: We determine the experimental elastic and inelastic scattering cross-section angular distributions, compare the theoretical predictions by adopting different models of optical potentials with the experimental data, and evaluate the coupling effect through the comparison of the distorted-wave Born approximation calculations with the coupled channels ones. Results: Optical models fail to describe the elastic angular distribution above the grazing angle (9.4{\deg}). A correction in the geometry to effectively account for deformation of the involved nuclear systems improves the agreement up to about 14{\deg}. Coupled channels effects are crucial to obtain good agreement at large angles in the elastic scattering cross section.

Effects of heavy meson loops on higher charmonia radiative transitions

Radiative transitions between charmonium states offer an insight into the internal structure of heavy quark bound states within QCD. In this work, we performed a systematically investigation of the radiative transitions of psi (nS) rightarrow gamma chi _{cJ}(mP) and psi (nD) rightarrow gamma chi _{cJ}(mP) via intermediate charmed meson loop with a non-relativistic effective field theory. We only focus on the line-shape behavior of the distributions via different intermediate meson loops. Our results show that the coupled-channel effects of these decays are relatively weak, while the coupled channel effects has obvious enhancement when the inial (final) states are closed to the thresholds of charmed-mesons pair.

Hidden charm pentaquark states and ΣcD¯(*) interaction in chiral perturbation theory

In this work, we employ the heavy hadron chiral perturbation theory (HHChPT) to calculate the $\Sigma_c\bar{D}^{(*)}$ potentials to the next-to-leading order. The contact, the one-pion exchange and the two-pion exchange interactions are included. Besides, the mass splittings between the heavy quark spin symmetry (HQSS) multiplets are kept in calculations. Our result shows that neglecting the heavy quark symmetry (HQS) violation effect may be misleading to predict the potentials between the charmed hadrons. We perform numerical analysis with three scenarios. In the first scenario, we relate the low-energy constants (LECs) in the contact terms of $\Sigma_c\bar{D}^{(*)}$ to those of nucleon systems, and reproduce the $P_c(4312)$ and $P_c(4440)$ as loosely bound states. In the second scenario, we vary the unknown LECs and find a small parameter region in which $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ can coexist as molecular states. In the third scenario, we include the coupled-channel effect on the basis of scenario II, and notice that the three $P_c$ states can be reproduced as molecular states simultaneously in a large region of parameters. Our analytical results can be used for the chiral extrapolations in lattice QCD. With the lattice QCD results in the future as inputs, the identification of the $P_c$ states and predictions for other systems would be more reliable.

Fusion barrier distribution and superheavy elements

The barrier distribution, originated from channel coupling effects in heavy-ion fusion reactions, has been extracted experimentally for many systems using either a fusion excitation function or an excitation function of large-angle quasi-elastic scattering. In this article, we discuss an application of the latter method to the 48Ca+248 Cm system, which is relevant to hot fusion reactions to synthesize superheavy elements. To this end, we carry out coupled-channels calculations for this system, taking into account the deformation of the target nucleus, and discuss the role of deformation in a formation of evaporation residues.

Description of coupled-channel in Semiclassical treatment of heavy ion fusion reactions

Fusion cross sections were measured for the systems 40Ar+144Sm, 40Ar+148Sm and 40Ar+ 154Sm above and under Coulomb barrier to understand the role of coupled channels effects involved in barriers fusion. The fusion barriers distributions and fusion probabilities were analyzed using the semiclassical mechanical code which called Sequential Complete Fusion (SCF) as well as Full Coupled Channel code (CCFULL). These calculations show that the observed fusion cross sections fusion barrier distribution and fusion probabilities for these systems are reproduced clearly in the semiclassical mechanical for all excitation states above and under Coulomb barrier.

First microscopic coupled-channels calculation of cross sections for inelastic α scattering off O16

The $\alpha$ inelastic scattering on $^{16}$O is investigated with the coupled-channel calculation using the $\alpha$-nucleus coupled-channel potentials, which are microscopically derived by folding the the Melbourne $g$-matrix $NN$ interaction with the $^{16}$O and $\alpha$ densities. The matter and transition densities of $^{16}$O are calculated by a microscopic structure model of the variation after the spin-parity projections combined with the generator coordinate method of $^{12}$C+$\alpha$ in the framework of the antisymmetrized molecular dynamics. The calculation reproduces the observed elastic and inelastic cross sections at incident energies of $E_\alpha$=104 MeV, 130 MeV, 146 MeV, and 386 MeV. The coupled-channel effect on the cross sections is also discussed.

Coupled-channel-induced S{-}D mixing of Charmonia and testing possible assignments for Y(4260) and Y(4360)

The mass spectrum and the two-body open-charm decays of the J^{PC}=1^{--} charmonium states are studied with the coupled-channel effects taken into account. The coupled-channel-induced mixing effects among the excited vector charmonia are studied. Based on our calculations of the masses and the decay widths, we find that the tension between the observed properties of Y(4260) / Y(4360) and their conventional charmonia interpretations could be softened.

ρρ scattering revisited with coupled channels of pseudoscalar mesons

The $\rho\rho$ scattering has been studied by two groups which both claimed a dynamical generated scalar meson, most likely to be $f_0(1370)$. Here we investigate the influence of coupled-channels of pseudoscalar mesons, i.e., $\pi\pi$ and $\bar KK$, on this dynamical generated scalar state. With the coupled channel effect included, the pole and partial decay widths are found to be more close to PDG values for $f_0(1500)$.

Possible triple-charm molecular pentaquarks from ΞccD1/ΞccD2* interactions

In this work, we explore a systematic investigation on $S$-wave interactions between a doubly charmed baryon $\Xi_{cc}(3621)$ and a charmed meson in a $T$ doublet $(D_1,\,D_2^*)$. We first analyze the possibility for forming $\Xi_{cc}D_1/\Xi_{cc}D_2^*$ bound states with the heavy quark spin symmetry. Then, we further perform a dynamical study on the $\Xi_{cc}D_1/\Xi_{cc}D_2^*$ interactions within a one-boson-exchange model by considering both the $S$-$D$ wave mixing and coupled channel effect. Finally, our numerical results conform the proposals from the heavy quark spin symmetry analysis: the $\Xi_{cc}D_1$ systems with $I(J^P)=$ $0(1/2^+,\,3/2^+)$ and the $\Xi_{cc}D_2^*$ systems with $I(J^P)=$ $0(3/2^+,\,5/2^+)$ can possibly be loose triple-charm molecular pentaquarks. Meanwhile, we also extend our model to the $\Xi_{cc}\bar{D}_1$ and $\Xi_{cc}\bar D_2^*$ systems, and our results indicate the isoscalars of $\Xi_{cc}\bar{D}_1$ and $\Xi_{cc}\bar{D}_2^*$ can be possible molecular candidates.

Enhanced calculations of fusion barrier distribution for heavy-ion fusion reactions using Wong formula

The effects of coupled-channels in heavy-ion fusion reaction for the system 40Ca + 192Os, 40Ca + 194Pt, and 48Ca + 197Au are discussed. The fusion cross-section σfus, the fusion barrier distribution Dfus and fusion probability Pfus are also discussed. The fusion barrier distribution is calculated using numerical three point, five point and Wong methods. Full quantum coupled-channels calculations are performed using CCFULL code with all order coupling to compare and with available experimental data. The χ² values for the case of no-coupling and coupling effects included shows clearly that the present calculations are in agreement with the experimental.