Bottom Counterparts Research Articles

Analysis of Tcc and Tbb based on the hadronic molecular model and their spin multiplets

Tcc(ccu¯d¯)+ has been reported by the LHCb experiment in 2022. The analysis using the Breit-Wigner parametrization found the small binding energy, 0.273 MeV, which is measured from the threshold of D*+D0. In this paper, we consider Tcc as a DD* hadronic molecule as a deuteronlike state. The one-boson exchange model is employed as for the heavy meson interactions, where we determine the cutoff parameter Λ to reproduce the reported binding energy of Tcc with I(JP)=0(1+). We discuss the properties of the bound state and also search for Tcc with quantum numbers other than 0(1+). Furthermore, we analyze Tbb as a bottom counterpart of Tcc, which involves two bottom quarks, and obtain several bound states. Finally, we consider the light-cloud basis for wave functions of the doubly heavy tetraquarks in the heavy quark limit. Using the basis, we find the spin multiplets of their bound states, indicating the spin structures of diquarks in Tcc and Tbb with the finite quark masses. Published by the American Physical Society 2024

Status and Prospects of Exotic Hadrons at Belle II

In the past 20 years, many new hadrons that are difficult to explain within the conventional quark model have been discovered in the quarkonium region; these are called exotic hadrons. The Belle II experiment, as the next-generation B factory, provides a good platform for exploring them. The charmonium-like states can be produced at Belle II in several ways, such as B meson decays, initial-state radiation processes, two-photon collisions and double charmonium production. Bottomonium-like states can be produced directly in e + e − colliding energies at Belle II with low continuum backgrounds. Belle II plans to perform a high-statistics energy scan from the threshold up to the highest possible energy of 11.24 GeV to search for new Yb states with J PC = 1−−, Xb [the bottom counterpart of χ c1(3872), also known as X(3872)] and partners of Zb states. We give a mini-review on the status and prospects of exotic hadrons at Belle II.

X(3872) , X(4014) , and their bottom partners at finite temperature

The properties of the $X(3872)$ and its spin partner, the $X(4014)$, are studied both in vacuum and at finite temperature. Using an effective hadron theory based on the hidden-gauge Lagrangian, the $X(3872)$ is dynamically generated from the $s$-wave rescattering of a pair of pseudoscalar and vector charm mesons. By incorporating the thermal spectral functions of open charm mesons, the calculation is extended to finite temperature. Similarly, the properties of the $X(4014)$ are obtained out of the scattering of charm vector mesons. By applying heavy-quark flavor symmetry, the properties of their bottom counterparts in the axial-vector and tensor channels are also predicted. All the dynamically generated states show a decreasing mass and acquire an increasing decay width with temperature, following the trend observed in their meson constituents. These results are relevant in relativistic heavy-ion collisions at high energies, in analyses of the collective medium formed after hadronization or in femtoscopic studies, and can be tested in lattice-QCD calculations exploring the melting of heavy mesons at finite temperature.

Interpretation of the Lambda _c(2910)^+ baryon newly seen by Belle Collaboration and its possible bottom partner

The developments in the experimental facilities and analyses techniques have recently lead to the observation of many hadronic states ranging from excitations of conventional hadrons to various exotic states. The baryons with single heavy quark are among these states providing an attractive field of research to get a better understanding of the nonperturbative nature of the strong interaction. Recently, the Belle Collaboration announced observation of the state Lambda _c(2910)^+ with a mass 2913.8pm 5.6pm 3.8~textrm{MeV}/c^2 and width 51.8pm 20.0pm 18.8~textrm{MeV}. In the present study, by the mass analyses of different excitations at Lambda _c channel and their comparison with existing experimental information, we find that the spin-parity of this newly found excited state is J^P= frac{1}{2}^- and it is a 2P state denoting by Lambda _c(frac{1}{2}^-,2P). We predict its current coupling as well, which can be served as one of the main input parameters to investigate different decays and interactions of this particle. We also determine the mass and current coupling of Lambda _b(frac{1}{2}^-,2P) as possible bottom counterpart of the new Lambda _c(2910)^+ state, which may be in agenda of different experiments in near future.

Gas-solid hydrodynamics in a stator-rotor vortex chamber reactor

The gas–solid vortex reactor (GSVR) has enormous process intensification potential. However the huge gas consumption can be a serious disadvantage for the GSVR in some applications such as fast pyrolysis. In this work, we demonstrate a recent novel design, where a stator-rotor vortex chamber (STARVOC) is driven by the fluid’s kinetic energy, to decouple the solids bed rotation and gas. Gas-solid fluidization by using air and monosized aluminum balls was performed to investigate the hydrodynamics. A constructed fluidization flow regime map for a fixed solids loading of 100 g shows that the bed can only be fluidized for a rotation speed between 200 and 400 RPM. Below 200 RPM, particles settle down on the bottom plate and cannot form a stable bed due to inertia and friction. Above 400 RPM, the bed cannot be fluidized with superficial velocities up to 1.8 m/s (air flow rate of 90 Nm3/h). The bed thickness shows some non-uniformities, being smaller at the top of the bed than at the bottom counterpart. However by increasing the air flow rate or rotation speed the axial nonuniformity can be resolved. The bed pressure drop first increases with increasing gas flow rate and then levels off, showing similar characteristics as conventional fluidized beds. Theoretical pressure drops calculated from mathematical models such as Kao et al. model agree well with experimental measurements. Particle velocity discrepancies between the top and bottom particles reveal that the impact of gravity cannot be completely neglected. Design guidelines and possible applications for further development of STARVOC concept are proposed based on fundamental data provided in this work.

Properties of the P c(4312) pentaquark and its bottom partner

We present an analysis of the newly observed pentaquark to shed light on its quantum numbers. To do that, the QCD sum rules approach is used. The measured mass of this particle is close to the threshold and has a small width, which supports the possibility of its being a molecular state. We consider an interpolating current in a molecular form and analyze both the positive and negative parity states with spin- . We also consider the bottom counterpart of the state with similar molecular form. Our mass result for the charm pentaquark state supports that the quantum numbers of the observed state are consistent with .

Heavy baryon-antibaryon molecules in effective field theory

We discuss the effective field theory description of bound states composed of a heavy baryon and antibaryon. This framework is a variation of the ones already developed for heavy meson-antimeson states to describe the $X(3872)$ or the $Z_c$ and $Z_b$ resonances. We consider the case of heavy baryons for which the light quark pair is in S-wave and we explore how heavy quark spin symmetry constrains the heavy baryon-antibaryon potential. The one pion exchange potential mediates the low energy dynamics of this system. We determine the relative importance of pion exchanges, in particular the tensor force. We find that in general pion exchanges are probably non-perturbative for the $\Sigma_Q \bar{\Sigma}_Q$, $\Sigma_Q^* \bar{\Sigma}_Q$ and $\Sigma_Q^* \bar{\Sigma}_Q^*$ systems, while for the $\Xi_Q' \bar{\Xi}_Q'$, $\Xi_Q^* \bar{\Xi}_Q'$ and $\Xi_Q^* \bar{\Xi}_Q^*$ cases they are perturbative If we assume that the contact-range couplings of the effective field theory are saturated by the exchange of vector mesons, we can estimate for which quantum numbers it is more probable to find a heavy baryonium state. The most probable candidates to form bound states are the isoscalar $\Lambda_Q \bar{\Lambda}_Q$, $\Sigma_Q \bar{\Sigma}_Q$, $\Sigma_Q^* \bar{\Sigma}_Q$ and $\Sigma_Q^* \bar{\Sigma}_Q^*$ and the isovector $\Lambda_Q \bar{\Sigma}_Q$ and $\Lambda_Q \bar{\Sigma}_Q^*$ systems, both in the hidden-charm and hidden-bottom sectors. Their doubly-charmed and -bottom counterparts ($\Lambda_Q {\Lambda}_Q$, $\Lambda_Q {\Sigma}_Q^{(*)}$, $\Sigma_Q^{(*)} {\Sigma}_Q^{(*)}$) are also good candidates for binding.

Towards a new paradigm for heavy-light meson spectroscopy

Since 2003 many new hadrons, including the lowest-lying positive-parity charm-strange mesons ${D_{s0}^*(2317)}$ and ${D_{s1}(2460)}$, were observed that do not conform with quark model expectations. It was recently demonstrated that various puzzles in the charm meson spectrum find a natural resolution, if the SU(3) multiplets for the lightest scalar and axial-vector states, amongst them the ${D_{s0}^*(2317)}$ and the ${D_{s1}(2460)}$, owe their existence to the nonperturbative dynamics of Goldstone-Boson scattering off $D_{(s)}$ and $D^*_{(s)}$ mesons. Most importantly the ordering of the lightest strange and nonstrange scalars becomes natural. In this work we demonstrate for the first time that this mechanism is strongly supported by the recent high quality data on the ${B^-\to D^+\pi^-\pi^- }$ provided by the LHCb experiment. This implies that the lowest quark-model positive-parity charm mesons, together with their bottom counterparts, if realized in nature, do not form the ground-state multiplet. This is similar to the pattern that has been established for the scalar mesons made from light up, down and strange quarks, where the lowest multiplet is considered to be made of states not described by the quark model. In a broader view, the hadron spectrum must be viewed as more than a collection of quark model states.

Exotic doubly charmed Ds0*(2317)D and Ds1*(2460)D* molecules

The $D_{s0}^*(2317) D$ and $D_{s1}^*(2460) D^*$ heavy meson systems can exchange a kaon that is emitted in S-wave owing to the opposite intrinsic parity of the $D_{s0}^*$($D_{s1}^*$) and $D$($D^*$) mesons. As a consequence of the mass difference of the $D_{s0}^*$($D_{s1}^*$) and $D$($D^*$) mesons, the range of the kaon exchange potential will be significantly longer than expected, corresponding to an effective mass of about $200\,{\rm MeV}$. The potential will be very strong: the strength of the interaction is proportional to $(m_{D_{s0}} - m_D)^2 / f_{\pi}^2$ and $(m_{D_{s1}} - m_{D^*})^2 / f_{\pi}^2$. This combination of range and strength almost guarantees the existence of $D_{s0}^*(2317) D$ and $D_{s1}^*(2460) D^*$ bound states with $J^P = 0^{-}$ and $J^P = 0^{-}, 2^{-}$ respectively. Concrete calculations indicate a binding energy of $5-15\,{\rm MeV}$ independently of $J^P$. The $D_{s0}^*(2317) D$ and $D_{s1}^*(2460) D^*$ molecules have manifestly exotic flavour quantum numbers: $C=2$, $S=1$ and $I=1/2$. We expect the existence of bottom counterparts composed of the $B B_{s0}$ and $B^* B_{s1}^*$ mesons, which will be more bound and have a richer spectrum that might include a shallow P-wave state and an excited S-wave state.

Tetraquark states in the bottom sector and the status of the $$Y_b$$ Y b (10890) state

We have done the exploratory study of bottom tetraquarks ($[bq\bar b \bar q];{q\in u,d}$) in the diquark-antidiquark framework with the inclusion of spin hyperfine, spin-orbit and tensor components of the one gluon exchange interaction. Our focus here is on the $Y_b$(10890) and other exotic states in the bottom sector. We have predicted some of the bottom counterparts to the charm tetraquark candidates. Our present study shows that if $Z_b(10610)$ and $Z_b(10650)$ are diquark-diantiquark states then they have to be first radial excitations only and we have predicted $Z_b(10650)$ state as first radial excitation of tetraquark state $X_b$ (10.143-10.230). We have identified $X_b$ state with $J^{PC}= 1^{+-}/0^{++}$ as being the analogue of $Z_c(3900)$. An observation of the $X_b$ will provide a deeper insight into the exotic hadron spectroscopy and is helpful to unravel the nature of the states connected by the heavy quark symmetry. We particularly focus on the lowest P wave $[bq][\bar b\bar q]$ states with $J^{PC}=1^{--}$ by computing their leptonic, hadronic and radiative decay widths to predict the status of still controversial $Y_b$(10890) state. Apart from this, we have also shown here the possibility of mixing of P wave states. In the case of mixing of $1^{--}$ state with different spin multiplicities, we found that predicted masses of the mixed P states differ from $Y_b$(10890) state only by $\pm20$ MeV energy difference which can be helpful to resolve further the structure of $Y_b$(10890).

Invited: Direct Bonding: A Key Enabler for 3D Monolithic Integration

Monolithic 3D Integration (3DMI) consists in processing transistors on top of each other sequentially. This technology appears to be an alternative solution to scaling, from the 7nm node integration and below, as substantial gain in area and performance as compared to planar technology is expected without scaling the transistor technology node. 3DMI appears to be the most optimized way to take advantage of the vertical dimension as almost no alignment constraints remains. By using a standard lithography, the top transistors can be aligned directly onto their bottom counterparts with a high accuracy (see Fig. 1), contrary to TSV-based 3D technologies [2]. Furthermore, 3DMI is a highly versatile technology as the different transistor levels can be optimized independently, from the choice of the channel characteristics (e.g. material, orientation, strain) to the architecture itself (e.g. CMOS on CMOS, PMOS on NMOS, FinFET on BULK, LVT on RVT) [3]. Such sequential integration raises two main technological challenges: - Creating an active layer above a bottom transistor which will become the channel of the top transistor. In order to achieve similar performance for top FET than bottom FET, the substrate quality must be equivalent than commercial substrates. Thus, this layer must be monocristalline and defect free in order to optimize the mobility and to be consistent with high performance criteria. A precise thickness control is also necessary in order to avoid device performance dispersion. - Realizing a high performance top transistor level without degrading the bottom level as the stacked transistor levels are processed sequentially, i.e. at low temperature process –typically below 600°C. Recent results demonstrate some integration solutions, such as junction activation by Solid Phase Epitaxy Regrowth below 600°C [4].To tackle the first challenge, we transfer a thin silicon layer from a high quality Silicon On Insulator (SOI) wafer by direct bonding. It appears to be the most effective solution to obtain a defect free monocristalline active layer with a well-controlled thickness. This method is preferred to different techniques which have been developed to create large monocristal grains of silicon either by laser anneal of amorphous Poly-Silicon [5] or by µ-Czochralsky process [6]. However, in both cases, large “seed layers” are necessary to control the orientation and the size of these grains, which is not consistent with for high density circuits.For this layer transfer, a blanket SOI wafer on which a Si02 layer is either grown or deposited, is bonded on the classical pre-metal dielectric above the bottom transistor level. The SOI backside is then removed by grinding and chemical etching to keep only the silicon layer. While expert knowledge has been reached for full sheet wafer bonding, the situation on a patterned layer can be really challenging with the design rules of 3DMI. In order to face these challenges, the surface preparation, the direct bonding process and the thinning steps have been optimized to prevent any defect on the whole 300mm surface. Also TMAH bevel edge protection and silicide protection layer have been added.This work will give a general overview of 3D monolithic challenges. Also, a specific focus will be made on direct bonding which is a major enabler of this type of integration. Indeed among the other alternative techniques, it appears to be the best solution to meet the high performance and high density criteria.REFERENCES:[1] P. Batude et al., VLSI Technology, pp. 158 (2011) [1] P. Batude et al., ECS Spring meeting, (16) pp. 47 (2008) [2] P. Batude et al., IITC-AMC (2014) [3] P. Batude et al., IEDM, pp.731-734 (2011) [4] C-H. Shen et al., IEDM, pp. 931-934 (2013) [5] J. Derakhshandeh et al., TED vol.58, no. 11 (2011)Fig.1: 3DMI demonstration with ultra-high alignment between the stacked transistors [1] obtained with 248nm stepper.

Open bottom states and theB¯-meson propagation in hadronic matter

The interaction and propagation of anti-B mesons with light mesons, N and Delta baryons is studied within a unitarized approach based on effective models that are compatible with chiral and heavy-quark symmetries. We find several heavy-quark spin doublets in the open-bottom sectors, where anti-B and anti-B* mesons are present. In the meson sector we find several resonant states, among them, a B0 and a B1 with masses 5530 MeV and 5579 MeV as well as Bs0* and Bs1* narrow states at 5748 MeV and 5799 MeV, respectively. They form two doublets with no experimental identification yet, the first one being the bottom counterpart of the D0(2400) and D1(2430) states, and the second bottom doublet associated to the ubiquitous Ds0* (2317) and the Ds1 (2460). In the baryon sector, several Lambda_b and Sigma_b doublets are identified, among them the one given by the experimental Lambda_b(5910) and Lambda*_b(5921). Moreover, one of our states, the Sigma_b*(5904), turns out to be the bottom counterpart of the Sigma*(1670) and Sigma_c*(2549), which is a case for discovery. We finally analyze different transport coefficients for the anti-B meson in hot matter, such as formed in heavy-ion collisions at RHIC and LHC. For RHIC/LHC energies, the main contribution to the coefficients comes from the interaction of anti-B mesons with pions. However, we also include the effects of baryonic density which might be sizable at temperatures T < 100 MeV, as the chemical potential is expected to increase in the last stages of the expansion. We conclude that although the relaxation time decreases with larger baryonic densities, the anti-B meson does not thermalize at RHIC/LHC energies, representing an ideal probe for the initial bottom distribution.

Turbidity currents interacting with three-dimensional seafloor topography

AbstractDirect numerical simulations are employed to investigate the interactions of bidisperse turbidity currents with three-dimensional seafloor topography in the form of Gaussian bumps. Results for two different bump heights are compared against currents propagating over a flat surface. The bump heights are chosen such that the current largely flows over the smaller bump, while it primarily flows around the taller bump. Furthermore, the effects of the settling velocity are investigated by comparing turbidity currents with corresponding compositional gravity currents. The influence of the bottom topography on the front velocity of turbidity currents is seen to be much weaker than the influence of the particle settling velocity. Consistent with earlier work on gravity currents propagating over flat boundaries, the influence of the Reynolds number on the front velocity of currents interacting with three-dimensional bottom topography is found to be small, as long as$\mathit{Re}\geq O(1000)$. The lobe-and-cleft structures, on the other hand, exhibit a stronger influence of the Reynolds number. The current/bump interaction deforms the bottom boundary-layer vorticity into traditional horseshoe vortices, with a downwash region in the centre of the wake. At the same time, the vorticity originating in the mixing layer between the current and the ambient interacts with the bump in such a way as to form ‘inverted horseshoe vortices’, with an upwash region in the wake centre. Additional streamwise vortical structures form as a result of baroclinic vorticity generation. The dependence of the sedimentation rate and streamwise vorticity generation on the height of the bump are discussed, and detailed analyses are presented of the energy budget and bottom wall-shear stress. It is shown that for typical laboratory-scale experiments, the range of parameters explored in the present investigation will not give rise to bedload transport or sediment resuspension. Based on balance arguments for the kinetic and potential energy components, a scaling law is obtained for the maximum bump height over which gravity currents can travel. This scaling law is validated by simulation results, and it provides a criterion for distinguishing between ‘short’ and ‘tall’ topographical features. For turbidity currents, this scaling result represents an upper limit. An interesting non-monotonic influence of the bump height is observed on the long-term propagation velocity of the current. On the one hand, the lateral deflection of the current by the bump leads to an effective increase in the current height and its front velocity in the region away from the bump. At the same time, taller bumps result in a more vigorous three-dimensional evolution of the current, accompanied by increased levels of dissipation, which slows the current down. For small bumps, the former mechanism dominates, so that on average the current front propagates faster than its flat bottom counterpart. For currents interacting with larger bumps, however, the increased dissipation becomes dominant, so that they exhibit a reduced front velocity as compared to currents propagating over flat surfaces.

HEAVY QUARK SYMMETRIES AND HEAVY MESON MOLECULES

A few of the newly discovered XYZ states might be bound states of a heavy meson and antimeson. These molecular states, as they are also known, respect heavy quark symmetries at the potential level and as a consequence they might appear in multiplets. Here we exploit their symmetry to predict new states from already known ones. For instance, we expect the existence of a bottom counterpart of the X(3872) at 10580 MeV. Conversely, the assumption that the Zb(10610) and [Formula: see text] are molecular implies a pair of analogous resonances with hidden charm located at 3870 and 4010 MeV. They might be identified with the Zc(3900) and Zc(4025), supporting the idea that they are [Formula: see text] and [Formula: see text] bound states.

Study ofXc(3250)as aD0*(2400)Nmolecular state

We present a QCD sum rule analysis for the newly observed resonance $X_{c}(3250)$ by assuming it as a $D_{0}^{*}(2400)N$ molecular state. Technically, contributions of operators up to dimension 12 are included in the operator product expansion (OPE). We find that it is difficult to find the conventional OPE convergence in this work. By trying releasing the rigid OPE convergence criterion, one could find that the OPE convergence is still under control in the present work and the numerical result for $D_{0}^{*}(2400)N$ state is $3.18\pm0.51 {GeV}$, which is in agreement with the experimental data of $X_{c}(3250)$. In view of that the conventional OPE convergence is not obtained here, thus only weak conclusions can be drawn regarding the explanation of $X_{c}(3250)$ in terms of a $D_{0}^{*}(2400)N$ molecular state. As a byproduct, the mass for the bottom counterpart $\bar{B}_{0}^{*}N$ state is predicted to be $6.50\pm0.49 {GeV}$.

Generation, Transformation, and Scattering of Long Waves Induced by a Short-Wave Group over Finite Topography

Abstract Second-order analytical solutions are constructed for various long waves generated by a gravity wave train propagating over finite variable depth h(x) using a multiphase Wentzel–Kramers–Brillouin (WKB) method. It is found that, along with the well-known long wave, locked to the envelope of the wave train and traveling at the group velocity Cg, a forced long wave and free long waves are induced by the depth variation in this region. The forced long wave depends on the depth derivatives hx and hxx and travels at Cg, whereas the free long waves depend on h, hx, and hxx and travel in the opposite directions at . They interfere with each other and generate free long waves radiating away from this region. The author found that this topography-induced forced long wave is in quadrature with the short-wave group and that a secondary long-wave orbital velocity is generated by variable water depth, which is in quadrature with its horizontal bottom counterpart. Both these processes play an important role in the energy transfer between the short-wave groups and long waves. These behaviors were not revealed by previous studies on long waves induced by a wave group over finite topography, which calculated the total amplitude of long-wave components numerically without consideration of the phase of the long waves. The analytical solutions here also indicate that the discontinuity of hx and hxx at the topography junctions has a significant effect on the scattered long waves. The controlling factors for the amplitudes of these long waves are identified and the underlying physical processes systematically investigated in this presentation.

Masses of tetraquarks with open charm and bottom

The masses of the heavy tetraquarks with open charm and bottom are calculated within the diquark–antidiquark picture in the framework of the relativistic quark model. The dynamics of the light quarks and diquarks is treated completely relativistically. The diquark structure is taken into account by calculating the diquark–gluon form factor. New experimental data on charmed and charmed-strange mesons are discussed. Our results indicate that the anomalous scalar Ds0⁎(2317) and axial vector Ds1(2460) mesons could not be considered as diquark–antidiquark bound states. On the other hand, Ds(2632) and DsJ⁎(2860) could be interpreted as scalar and tensor tetraquarks, respectively. The predictions for masses of the corresponding bottom counterparts of the charmed tetraquarks are given.

Masses of heavy tetraquarks with hidden charm and bottom

The relativistic model of heavy tetraquarks is formulated within the diquark-antidiquark picture. The diquark structure is taken into account by the diquark-gluon form factor. New experimental data on charmonium-like states above open charm threshold are discussed. The obtained results indicate that X(3872), Y(4140), Y(4260), Y(4360), Z2(4250), Z(4433) and Y(4660) could be tetraquark states with hidden charm. Predictions for the masses of bottom counterparts to the charm tetraquark candidates are given.

X(3872)and the bound state problem ofD0D¯*0(D¯0D*0)in a chiral quark model

The bound state problem of D{sup 0}D*{sup 0}(D{sup 0}D*{sup 0}) is relevant to the molecular interpretation of the X(3872). We investigated this problem in a chiral quark model by solving the resonating group method equation. We found the system is unbound through S-wave {pi} and {sigma} interactions. The inclusion of {rho} and {omega} meson exchanges is helpful to the formation of a molecule. Because the binding energy relies on the coupling constants, we cannot draw a definite conclusion as to whether a molecular state exists in the D{sup 0}D*{sup 0}(D{sup 0}D*{sup 0}) system. When moving on to the bottom counterpart, we obtained an S-wave BB* state.

RELATIVISTIC MODEL OF HIDDEN BOTTOM TETRAQUARKS

The relativistic model of the ground state and excited heavy tetraquarks with hidden bottom is formulated within the diquark–antidiquark picture. The diquark structure is taken into account by calculating the diquark–gluon vertex in terms of the diquark wave functions. Predictions for the masses of bottom counterparts to the charm tetraquark candidates are given.