Search

In our recent work\cite{Noh:2023zoq}, the mass and binding energy of $T_{cc}$ are found to be $3873$ MeV and $-2$ MeV, respectively, which align with the observations reported at LHCb\cite{LHCb:2021vvq}. Based on our latest quark model approach, we extend our search for other potentially stable configurations of doubly heavy tetraquarks using our nonrelativistic quark model described in Ref.~\cite{Noh:2023zoq}. Our numerical calculations indicate that the $\bar{u}\bar{s}cb$ configuration is deeply bound. However, the $\bar{u}\bar{d}cb$ configuration with the isospin symmetry in the light quark sector is relatively less bound. In this study, we emphasize a compulsory aspect for requiring a complete set of three dimensional harmonic oscillator bases through the discussion of the $\bar{u}\bar{s}cb$ configuration and investigate the essential differences between the $\bar{u}\bar{s}cb$ and $\bar{u}\bar{d}cb$ configurations., Comment: 14 pages

As our recent quark model calculation~\cite{Noh:2023fdy} suggests a strong possibility of a compact $T_{cc}$ that closely reproduces experimental mass, we have a strong incentive to extend our work to investigate the possible compact configuration of a pentaquark $udcc\bar{s}$, which is related to the structure of the doubly charmed tetraquark $T_{cc}$. Since the introduction of a complete set of 3-dimensional harmonic oscillator bases to a spatial wave function in solving a quark model-based Hamiltonian with variational method leads to a more accurate value of the mass, it seems natural that future studies of the pentaquark should be treated with the same elaborate technical approach. To attain such precision for the ground state energy, we utilize a complete set of 3-dimensional harmonic oscillator base up to 6th quanta. Before carrying out this process, one important thing that has to be taken into account is to find out the color $\otimes$ spin states of the pentaquark for the evaluation of color and spin interaction most essential to the quark model configuration. To easily identify the suitable configuration, we make a systematic analysis of $SU(6)_{CS}$ irreducible representation of the pentaquark, from which we find that there is a correspondence between the color $\otimes$ spin states obtained from their coupling scheme and the multiplet of the $SU(6)_{CS}$ irreducible representation of the pentaquark. We find that the energy of the pentaquark configuration is +18.5 MeV above the lowest threshold for decay into $\Xi_{cc}$ and $K$, suggesting that this configuration is not stable against its decay. Nonetheless, while we used a Gaussian hyperfine potential, it was recently found that a Yukawa form leads to a stronger attraction for the $T_{cc}$ configuration. Therefore it is important to study the same configuration using the latter potential., Comment: 28 pages

The recent discovery of the doubly charmed tetraquark $T_{cc}$ ($\bar{u}\bar{d}cc$) provides a stringent constraint on its binding energy relative to its lowest decay threshold. We use a fully convergent spatial wave function and perform a simultaneous global fit to both the meson and baryon spectra. Our analysis shows that a Yukawa type hyperfine potential leads to a slight bound state for $T_{cc}$ with $(I,S) = (0,1)$ below its lowest threshold, in agreement with recent experimental findings. We also find that $T_{cc}$ is highly likely to be in a compact configuration., Comment: 5 pages, 4 figures

We argue why the recently observed $T_{cc}$ could either be a compact multiquark configuration or a loosely bound molecular configuration composed of charmed mesons, whereas the $X(3872)$ is most likely a molecular configuration. The argument is based on different short range interactions for these tetraquark states coming from the color-color and color-spin interaction in a quark model, and the presence of a common strong D-wave mixing at larger distance similar to the deuteron case, which for the molecular configurations lead to large sizes. Such an analogy at large distance allows us to calculate the transverse momentum dependence of the loosely bound molecular configuration of tetraquarks produced in heavy ion collisions using the coalescence model that successfully reproduces the deutron data using the proton spectra. The ratio of the integrated $X(3872)$ yield obtained from our method to the $\psi(2S)$ yield obtained from statistical hadronization model method is calculated to be $0.806 \pm 0.234$, which is a factor of 2.47 larger than that obtained by using statistical model predictions for both particles and in line with the data from the CMS experiment. As the previously calculated transverse momentum distribution of the $T_{cc}$ assuming the structure to be a compact multiquark configuration is markedly different, experimental measurements of the transverse distribution of the tetraquark states will discriminate between their two possible structures., Comment: 9 pages, 3 figures

We have improved our previous variational method based constituent quark model by introducing a complete set of 3-dimensional harmonic oscillator bases as the spatial part of the total wave function. To assess the validity of our approach, we compared the binding energy, thus calculated with the exact value for the hydrogen model. After fitting to the masses of the ground state hadrons, we apply our new method to analyze the doubly-heavy tetraquark states $qq'\bar{Q}\bar{Q'}$ and compared the result for the binding energies with that from other works. We also calculated the ground state masses of $T_{sc} (ud\bar{s}\bar{c})$ and $T_{sb} (ud\bar{s}\bar{b})$ with $(I,S) = (0,1), (0,2)$. We found that $T_{bb} (ud\bar{b}\bar{b})$ and $us\bar{b}\bar{b}$, both with $(I,S) = (0,1)$, are stable against the two lowest threshold meson states with binding energies $-145$ MeV and $-42$ MeV, respectively. We further found that $T_{cb} (ud\bar{c}\bar{b})$ is near the lowest threshold. The spatial sizes for the tetraquarks are also discussed., Comment: 20 pages, 10 figures

We systematically analyze the flavor color spin structure of the pentaquark $q^4\bar{Q}$ system in a constituent quark model based on the chromomagnetic interaction in both the SU(3) flavor symmetric and SU(3) flavor broken case with and without charm quarks. We show that the originally proposed pentaquark state $\bar{Q}s qqq$ by Gignoux et al and by Lipkin indeed belongs to the most stable pentaquark configuration, but that when charm quark mass correction based on recent experiments are taken into account, a doubly charmed antistrange pentaquark configuration ($udc c \bar{s}$) is perhaps the only flavor exotic configuration that could be stable and realistically searched for at present through the $\Lambda_c K^+ K^- \pi^+$ final states. The proposed final state is just reconstructing $K^+$ instead of $\pi^+$ in the measurement of $\Xi^{++}_{cc} \rightarrow \Lambda_c K^- \pi^+ \pi^+$ reported by LHCb collaboration and hence measurable immediately., Comment: 5pages,5tables

We perform a constituent quark model analysis for the masses of the doubly heavy tetraquark states $T_{QQ}$ after we fix the parameters to fit the masses of the newly observed $\Xi_{cc}^{++}$ and hadrons involving heavy quarks relevant to the stability of these states. We investigate in detail how the relative distances between quark pairs vary as we change the quark content and how they affect the various contributions to the total tetraquark masses. We also find that our full calculations give in general less binding compared to simplified quark model calculations that treat quark dynamics inside the tetraquark the same as that inside a baryon. We trace the main origin to be the differences in the number of relative kinetic energies which increases as one goes from meson, baryon and tetraquarks. We also compare our new results with previous works using less constrained parameters and find that the tetraquark state $T_{bb}(ud\bar{b}\bar{b})$ and $T_{bb}(us\bar{b}\bar{b})$ are bound by 120.56 MeV and 7.3 MeV respectively., Comment: 11 pages

We decompose the tribaryon configuration in terms of SU(3) flavor and spin state and analyse their color-spin-flavor wave function following Pauli principle. By comparing the color-color and color-spin interactions of compact tribaryon configuration against the lowest three nucleon threshold within a constituent quark model, we show that the three nucleon forces have to be repulsive at short distance for all possible quantum numbers and all values of the SU(3) symmetry breaking parameter. Our work identifies the origin of the repulsive nuclear three body forces including the hyperons at short distance that are called for from phenomenological considerations starting from nuclear matter to the maximum mass of a neutron star., Comment: 5 pages, 1 figure, version to be published in prd

We investigate the symmetry property and the stability of the heptaquark containing two identical heavy antiquarks using color-spin interaction. We construct the wave function of the heptaquark from the Pauli exclusion principle in the SU(3) breaking case. The stability of the heptaquark against the strong decay into one baryon and two mesons is discussed in a simple chromomagnetic model. We find that $q^2 s^3 \bar{s}^2$ with $I=0,S=\frac{5}{2}$ is the most stable heptaquark configuration that could be probed by reconstructing the $\Lambda+\phi+\phi$ invariant mass., Comment: 14 pages, 11 figures, version to be published in prd

Interfaces dominate heat conduction in nanostructured systems, and much work has focused on methods to enhance interfacial conduction. These approaches generally address planar interfaces, where the heat flux vector is everywhere normal to the interface. Here, we explore a nanostructured interface geometry that uses nonplanar features to enhance the effective interfacial conductance beyond what is possible with planar interfaces. This interface consists of interdigitating Al pillars embedded within SiO2 with characteristic feature size ranging from 100 nm to 800 nm. The total sidewall surface area is modulated to highlight the impact of this additional channel by changing the pillar-to-pillar pitch L_P between 1.6 um and 200 nm while maintaining the same Al:SiO2 fill fraction. Using optical pump-probe thermoreflectance measurements, we show that the effective conductance of a ~65 nm thick fin layer monotonically increases with decreasing L_P, and that the conductance for L_P = 200 nm is more than twice the prediction for a layered stack with the same volume ratio and a planar interface. Through a combination of Boltzmann transport modeling and finite element calculations, we explore the impact of the pitch L_P and the pillar aspect ratio on effective thermal conductance. This analysis suggests that the concept of nanostructured interfaces can be extended to interfaces between diffusive and quasi-ballistic media in highly scaled devices. Our work proposes that the controlled texturing of interfaces can facilitate interfacial conduction beyond the planar interface regime, opening new avenues for thermal management at the nanoscale., Comment: To appear in Nanoscale and Microscale Thermophysical Engineering

The constituent quark model with color-spin hyperfine potential is used to investigate the property of a compact pentaquark configuration with $J^p$=$3/2^-$ and isospin=1/2, which is the most likely quantum number of one of the recently observed exotic baryon states at LHCb. Starting from the characterization of the isospin, color, and spin states for the pentaquark configuration, we construct the total wave function composed of the spatial wave function, which we take to be symmetric and in S-wave, and the four orthogonal isospin $\otimes$ color $\otimes$ spin states that satisfy the Pauli principle. We then use the variational method to find a compact stable configuration. While there are compact configurations where the hyperfine potential is more attractive than the sum of $p$ and $J/\psi$ hyperfine potentials, we find that the ground state is the isolated $p$ and $J/\psi$ state. Furthermore, the mass of the excited state lies far above the observed pentaquark state leading us to conclude that the observed states can not be a compact multiquark configuration with $J^p$=$3/2^-$., Comment: no figure,10 pages

We investigate the symmetry property and the stability of dibaryons containing two strange quarks and one heavy flavor with $I=\frac{1}{2}$. We construct the wave function of the dibaryon in two ways. First, we directly construct the color and spin state of the dibaryon starting from the four possible SU(3) flavor state. Second, we consider the states composed of five light quarks, and then construct the wave function of the dibaryon by adding one heavy quark. The stability of the dibaryon against the strong decay into two baryons is discussed by using variational method in a constituent quark model with confining and hyperfine potential. We find that for all configurations with S=0,1,2, the ground states of the dibaryons are the sum of two baryons, and there are no compact bound state that is stable against the strong decay., Comment: 36 pages, 1 figure

We investigate the symmetry property and construct the wave function of the dibaryon states containing two strange quarks with S=0 in both the flavor SU(3) symmetric and breaking cases. We discuss how the color $\otimes$ isospin $\otimes$ spin states of dibaryon in the symmetry broking case of flavor SU(3) can be extracted from the fully antisymmetric states in flavor SU(3). The stability of the dibaryon against the strong decay into two baryons are then discussed, by using the variational method within a constituent quark model with a confining and color-spin interactions. To compare our results with that from lattice QCD in flavor SU(3) limit, we search for the stable H-dibaryon in a wide range of $\pi$ meson mass. We find that with the given potential, there is no compact six quark dibaryon state in the SU(3) flavor symmetry broken case with realistic quark masses as well as in flavor SU(3) symmetric case in a wide range of quark masses., Comment: 22pages, 2figures

We probe effects of the partial chiral symmetry restoration to the mass of heavy-light mesons in a constituent quark model by changing the constituent quark mass of the light quark. Due to the competing effect between the quark mass and the linearly rising potential, whose contribution to the energy increases as the quark mass decreases, the heavy-light meson mass has a minimum value near the constituent quark mass typically used in the vacuum. Hence, the meson mass increases as one decreases the constituent quark mass consistent with recent QCD sum rule analyses, which show an increasing $D$ meson mass as the chiral order parameter decreases., Comment: 4 pages, 4 figures

We investigate the properties of dibaryons containing u and d quarks in the constituent quark model. In constructing the ground state wave function, we choose the spatial part to be fully symmetric and the remaining color, isospin and spin part to be antisymmetric so as to satisfy the the Pauli principle. By adapting the IS coupling scheme that combine the isospin basis function with the spin basis function, and subsequently coupling this to the color singlet basis function, we construct the color $\otimes$ isospin $\otimes$ spin states compatible with the physical states of the dibaryon. By using the variational method, we then calculate the mass of the dibaryon in a nonrelativistic potential model, involving Coulomb, color confinement and color-spin hyperfine interaction. In particular, to asses the stability for different types of the confinement potential, we introduce one that is linearly proportional to the interquark distance and another to its square root. For all cases considered, we find that there are no compact bound states against the strong decay., Comment: 17 pages

Using the variational method, we calculate the mass of the J^P=1^+ (ud)bar(bb) tetraquark containing two identical heavy antiquarks in a nonrelativistic potential model with color confinement and spin hyperfine interaction. In particular, we extend a previous investigation of the model by Brink and Stancu by investigating the effect of including the color anti-sextet component of the diquark configuration as well as using several more Gaussian parametrization for the L=0 part of the spatial wave function. We find that for the heavy tetraquark, the 6bar{6} component among the color singlet bases is negligible and that the previously used specific Gaussian spatial configuration is good enough in obtaining the ground state energy., Comment: 14 pages

The flow of charm is calculated in 2+1 ideal hydrodynamics by introducing the charge of $c\bar{c}$ pair assuming that the number of $c\bar{c}$ pairs is conserved in relativistic heavy-ion collisions. It is found that the mean radial flow velocity of charm quarks is smaller than that of bulk matter by 10$\sim$15 \% and the measured $v_2$ of heavy-flavor electrons is reproduced up to $p_T^e=$ 1.5 GeV/c in Au+Au collision at RHIC. The same flow is applied to regenerated $J/\psi$ and its $v_2$ is discussed., Comment: 6 pages, 7 figures

We build up a model to reproduce the experimentally measured $R_{AA}$ of $J/\psi$ near midrapidty in Au+Au collision at $\sqrt{s_{NN}}=200$ GeV. The model takes into account the $J/\psi$ suppression from the quark-gluon plasma and hadron gas as well as the nuclear absorption of primordial charmonia and the regeneration effects at the hadronization stage, and hence is a generalization of the two component model introduced by Grandchamp and Rapp. The improvements in this work are twofold; the addition of the initial local temperature profile and a consistent use of QCD NLO formula for both the dissociation cross section in the hadron gas and the thermal decay widths in the quark-gluon plasma for the charmonium states. The initial local temperature profile is determined from the assumption that the local entropy density is proportional to a formula involving the number densities of the number of participants and of the binary collisions that reproduces the multiplicities of charged particles at chemical freeze-out. The initial local temperature profile brings about a kink in the $R_{AA}$ curve due to the initial melting of $J/\psi$. The initially formed fireball, composed of weakly interacting quarks and gluons with thermal masses that are extracted from lattice QCD, follows an isentropic expansion with cylindrical symmetry. The fit reproduces well the Au+Au as well as the Cu+Cu data. The same method is applied to predict the $R_{AA}$ expected from the Pb+Pb collision at LHC energy., Comment: 18 pages, 13 figures