Search

Lepton scattering is an established ideal tool for studying inner structure of small particles such as nucleons as well as nuclei. As a future high energy nuclear physics project, an Electron-ion collider in China (EicC) has been proposed. It will be constructed based on an upgraded heavy-ion accelerator, High Intensity heavy-ion Accelerator Facility (HIAF) which is currently under construction, together with a new electron ring. The proposed collider will provide highly polarized electrons (with a polarization of $\sim$80%) and protons (with a polarization of $\sim$70%) with variable center of mass energies from 15 to 20 GeV and the luminosity of (2-3) $\times$ 10$^{33}$ cm$^{-2}$ s$^{-1}$. Polarized deuterons and Helium-3, as well as unpolarized ion beams from Carbon to Uranium, will be also available at the EicC. The main foci of the EicC will be precision measurements of the structure of the nucleon in the sea quark region, including 3D tomography of nucleon; the partonic structure of nuclei and the parton interaction with the nuclear environment; the exotic states, especially those with heavy flavor quark contents. In addition, issues fundamental to understanding the origin of mass could be addressed by measurements of heavy quarkonia near-threshold production at the EicC. In order to achieve the above-mentioned physics goals, a hermetical detector system will be constructed with cutting-edge technologies. This document is the result of collective contributions and valuable inputs from experts across the globe. The EicC physics program complements the ongoing scientific programs at the Jefferson Laboratory and the future EIC project in the United States. The success of this project will also advance both nuclear and particle physics as well as accelerator and detector technology in China., EicC white paper, written by the whole EicC working group

Using an almost complete relativistic method based on the Bethe-Salpeter equation, we study the mixing angle $\theta$, the mass splitting $\bigtriangleup M$, the strong decay widths $\Gamma(D^{({\prime})}_1)$ and the weak production rates $Br(B\to D^{({\prime})}_1\ell\nu_{\ell})$ of the $D_1(2420)$ and $D_1^{\prime}(2430)$. We find there is the strong cancellation between the $^1P_1$ and $^3P_1$ partial waves in $D_1^{\prime}(2430)$ with $\theta \sim-35.3^{\circ}$, which leads to the `$1/2$ vs $3/2$' puzzle. The puzzle can not be overcome by adding only relativistic corrections since in a large parameter range where $\bigtriangleup M$ is linear varying and not small, the $\theta$, $\Gamma(D^{({\prime})}_1)$ and $Br(B\to D^{({\prime})}_1\ell\nu_{\ell})$ remain almost unchanged but conflict with data. While in a special range around the mass inverse point where $\bigtriangleup M=0$ and $\theta =\pm 90^{\circ}$, they change rapidly but we find the windows where $\bigtriangleup M$, $\Gamma(D^{({\prime})}_1)$ and $Br(B\to D^{({\prime})}_1\ell\nu_{\ell})$ are all consistent with data. The small $\bigtriangleup M$ confirmed by experiment, is crucial to solve the `$1/2$ vs $3/2$' puzzle., Comment: 18 pages, 5 figures

The spectrum and relativistic wave functions of $B_c$ system are investigated via solving the complete Salpeter equation. Emphases are put on the study of the partial waves of each $J^P$ state. Our study shows that there are three categories of $J^P$ states. The first category contains $0^-$ and $0^+$ states, which are ${}^1S_0$ dominant state with a small amount of $P$ wave and ${}^3P_0$ dominant state with a small amount of $S$ wave, respectively. The second category includes the natural parity states, such as $1^-$, $2^+$, $3^-$, etc. Taking the $1^-$ state as an example, we study it in two cases. One is the ${}^3S_1$ dominant state with a small amount of $P$ and $D$ waves, and the other is the ${}^3D_1$ dominant state but contains a large amount of $S$ and $P$ wave components. The third category includes the unnatural parity states, such as $1^+$, $2^-$, $3^+$, etc. For the $1^+$ spectrum, the states are grouped into pairs with different radial quantum numbers. Each pair contains two ${}^1P_1-{}^3P_1$ mixing states, and the corresponding mixing angles are calculated by using the relativistic wave functions., Comment: 26 pages, 1 table, 8 figures

Mass spectra and wave functions of the $J^P=\frac{1}{2}^+$ $(bcq)$ baryons are calculated by the relativistic Bethe-Salpeter equation\,(BSE) with considering the mixing effects between the $1^+$ and $0^+$ $(bc)$-diquarks inside. Based on the diquark picture, the three-body problem of baryons is transformed into two two-body problems. The BSE and wave functions of the $0^+$ diquark are given, and then solved numerically to obtain the effective mass spectra and form factors. Also we present the wave functions at zero point for the $(bc)$-diquark. Considering the obtained diquark form factors, the $(bcq)$ baryons are then described by the BSE as the bound state of a diquark and a light quark, where the interaction kernel includes the inner transitions between the $0^+$ and $1^+$ diquarks. The general wave function of the $\frac{1}{2}^+$ $(bcq)$ baryons is constructed and solved to obtain the corresponding mass spectra. Especially, by using the obtained wave functions, the mixing effects between $\Xi_{bc}(\Omega_{bc})$ and $\Xi_{bc}'(\Omega'_{bc})$ in ground states are computed and determined to be small ($\sim \!1\%$). The numerical results indicate that it is a good choice to take $\Xi_{bc}$ and $\Xi'_{bc}$ as the baryon states with the inside $(bc)$-diquarks occupying the definite spin., Comment: 26 pages, 15 figures

In the paper, the inclusive production of heavy quarkonium ${\ensuremath{\eta}}_{Q}$ ($Q=b$ or $c$) via $Z$ boson decays within the framework of nonrelativistic QCD effective theory are studied. The contributions from the leading color-singlet and color-octet Fock states are considered. Total and differential decay widths for the inclusive decays $Z\ensuremath{\rightarrow}{\ensuremath{\eta}}_{Q}+X$ are presented. It is found that the decays $Z\ensuremath{\rightarrow}{\ensuremath{\eta}}_{Q}+X$ are dominated by the ${^{3}S}_{1}^{[8]}$ component, so the decays can be inversely adopted to determine the values of the long-distance matrix elements $⟨{\mathcal{O}}^{{\ensuremath{\eta}}_{c}}({^{3}S}_{1}^{[8]})⟩$ and $⟨{\mathcal{O}}^{{\ensuremath{\eta}}_{b}}({^{3}S}_{1}^{[8]})⟩$, respectively. Our numerical results show that at an ${e}^{+}{e}^{\ensuremath{-}}$ collider running at the $Z$ pole with a high luminosity around $1{0}^{35}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$ (a super $Z$ factory), there are about $4.5\ifmmode\times\else\texttimes\fi{}{10}^{7}$ ${\ensuremath{\eta}}_{c}$ meson events and $6.1\ifmmode\times\else\texttimes\fi{}{10}^{5}$ ${\ensuremath{\eta}}_{b}$ meson events to be produced per operation year, and the inclusive decays may be used for clarifying some problems on the heavy quarkonium ${\ensuremath{\eta}}_{Q}$ and nonrelativistic QCD.

The compact tetraquark states with fully heavy quark contents $QQ\overline{Q}\overline{Q}$ are studied as the bound states of the diquark-antidiquark within the Bethe-Salpeter framework. The (anti)diquark masses and form factors used are the same as we calculated the doubly heavy baryons in a previous work. Under the instantaneous approximation, the three-dimensional (Bethe-)Salpeter equation of the tetraquarks is derived and solved numerically to obtain the corresponding mass spectra and wave functions of the tetraquarks with ${J}^{PC}={0}^{++}$, ${1}^{+\ensuremath{-}}$, and ${2}^{++}$. Our results show that the three ground states of $cc\overline{c}\overline{c}$ locate in the mass range of 6.4--6.5 GeV, and the $bb\overline{b}\overline{b}$ states in mass range of 19.2--19.3 GeV. The obtained relativistic wave functions naturally include the mixing effects from the possible $D$ (or $G$) partial waves, and then can be further used to do precise calculations of the tetraquark decays. Based on the obtained results, the LHCb's observation $X(6900)$ is less likely to be the ground states of compact $cc\overline{c}\overline{c}$ tetraquarks but might be the first or second excited states. In addition, a widely used propagatorlike form factor is also investigated and discussed.

In this paper we take B-L supersymmetric standard model (B-LSSM) and TeV scale left-right symmetric model (LRSM) as two representations of the two kinds of new physics models to study the nuclear neutrinoless double beta decays ($0\nu2\beta$) so as to see the senses onto these two kinds of models when the decays are taken into account additionally. Within the parameter spaces allowed by all the exist experimental data, the decay half-life of the nucleus $^{76}$Ge and $^{136}$Xe, $T^{0\nu}_{1/2}$($^{76}$Ge, $^{136}$Xe), is precisely calculated and the results are presented properly. Based on the numerical results, we conclude that the room of LRSM type models for the foreseeable future experimental observations on the decays is greater than that of B-LSSM type models., Comment: 37 pages, 9 figures

In the paper, we calculate the fragmentation functions for $g \to B_c$ and $g \to B_c^*$. The ultraviolet divergences in the calculation are removed through the renormalization of the operator definition of the fragmentation functions under the modified minimal subtraction scheme. We then obtain the fragmentation functions $D_{g \to B_c}(z,\mu_F)$ and $D_{g \to B_c^*}(z,\mu_F)$, which are presented as figures and fitting functions. The obtained fragmentation functions are complementary to the previous work on the next-to-leading order fragmentation functions for $\bar{b}\to B_c(B_c^*)$ and $c\to B_c(B_c^*)$., Comment: 22 pages, 4 figures

This paper presented the proximity capacitive sensor using Hidden Markov Model to detect user gesture. The human interactive gesture signal analyses have been a research topic smart home fields that algorithms build in local device to recognize real time. The Hidden Markov Model have been used in many fields that including identification and classification. The features of Hidden Markov Model used probability concept train and learn identification model that obtain correct input signal probability feedback to user. Moreover, Hidden Markov Model uses a transition between the observed value and the state to describe model which record dynamic random distribution to identify object. Therefore, the Hidden Markov Model methods to identify user gesture has satisfactory response.

The proposed of this paper is a signal acquisition wearable device base on single chip microcontroller solution for Electrocardiography (ECG) monitor. Traditional ECG monitor used complex circuits to detect ECG signal that improved detection 60Hz environment noise and skin interference. We proposed an easy to detect ECG signal mothed which used Texas Instruments MCU MSP430I series that feature have 24bit sigma delta ADC, and the low power consumption saved battery energy that has satisfactory performance in wearable device fields. Additional, we design a discrete digital filter to improve environment noise and skin interference in microcontroller. In the experimental results, we presented a single chip ECG wearable device monitor that signal shows satisfactory output $response$.

To test the standard model (SM) precisely and to look for the clues deviating from SM, a proposal for determining the effective electro-weak mixing angles sin2 θeff (particularly f = lept, c, b) is proposed. It is via observing the asymmetries (the forward-backward one AFB, the left-right one ALR and the combined left-right forward-backward one ALRFB ) of the doubly heavy-flavored hadrons in the production at a super Z-factory (an e+e− collider designed with a luminosity as high as possible for modern-day techniques runs around the center-of-mass energy $$\sqrt s = {m_Z}$$ ). To see the sensitivity, uncertainties as well as the event accumulation precisely, the observables for describing the asymmetries of the produced hadrons are computed numerically with varying effective mixing angles, and based on the result analyses, it is concluded that the proposal may offer an independent complement determination of the effective mixing angles.

Basing on the systems of linear partial differential equations derived from Mellin-Barnes representations and Miller's transformation, we obtain GKZ-hypergeometric systems of one-loop self energy, one-loop triangle, two-loop vacuum, and two-loop sunset diagrams, respectively. The codimension of derived GKZ-hypergeometric system equals the number of independent dimensionless ratios among the external momentum squared and virtual mass squared. Taking GKZ-hypergeometric systems of one-loop self energy, massless one-loop triangle, and two-loop vacuum diagrams as examples, we present in detail how to perform triangulation and how to construct canonical series solutions in the corresponding convergent regions. The series solutions constructed for these hypergeometric systems recover the well known results in literature., Comment: 32 pages, 1 figure

A recently observed spectrum of ${P}_{c}$ states exhibits a strong link to ${\mathrm{\ensuremath{\Sigma}}}_{c}{\overline{D}}^{(*)}$ thresholds. In spite of successful molecular interpretations, we still push forward to wonder whether there exist finer structures. Utilizing the effecitve Lagrangians respecting heavy quark symmetry and chiral symmetry, as well as instantaneous Bethe-Salpeter equations, we investigate the ${\mathrm{\ensuremath{\Sigma}}}_{c}{\overline{D}}^{(*)}$ interactions and three ${P}_{c}$ states. We confirm that ${P}_{c}(4312)$ and ${P}_{c}(4440)$ are good candidates of ${\mathrm{\ensuremath{\Sigma}}}_{c}\overline{D}$ and ${\mathrm{\ensuremath{\Sigma}}}_{c}{\overline{D}}^{*}$ molecules with spin-$\frac{1}{2}$, respectively. Unlike other molecular calculations, our results indicate the ${P}_{c}(4457)$ signal might be a mixture of spin-$\frac{3}{2}$ and spin-$\frac{1}{2}$ ${\mathrm{\ensuremath{\Sigma}}}_{c}{\overline{D}}^{*}$ molecules, where the latter one appears to be an excitation of ${P}_{c}(4440)$. Therefore we conclude that, confronting three LHCb ${P}_{c}$ signals, there may exist not three, but four molecular states.

In this paper, we calculate the total decay widths for the ${W}^{+}$-boson decays, ${W}^{+}\ensuremath{\rightarrow}{B}_{c}+b+\overline{s}+X$ and ${W}^{+}\ensuremath{\rightarrow}{B}_{c}^{*}+b+\overline{s}+X$, up to next-to-leading order (NLO) accuracy within the framework of the nonrelativistic QCD theory. Both the fixed-order and the fragmentation approaches are adopted to do the calculation. Differential decay widths $d\mathrm{\ensuremath{\Gamma}}/dz$ and $d\mathrm{\ensuremath{\Gamma}}/d{s}_{1}$ are also given. We find that the NLO corrections are significant in those two ${W}^{+}$ decay channels. Our numerical results show that at the LHC, there are about $7.03\ifmmode\times\else\texttimes\fi{}{10}^{4}$ ${B}_{c}$-meson events and $5.10\ifmmode\times\else\texttimes\fi{}{10}^{4}$ ${B}_{c}^{*}$-meson events to be produced via the ${W}^{+}$-boson decays per operation year.

We calculate the two-body strong decays of the orbitally excited scalar mesons $$D_0^*(2400)$$ and $$D_J^*(3000)$$ by using the relativistic Bethe–Salpeter (BS) method. $$D_J^*(3000)$$ was observed recently by the LHCb Collaboration, the quantum number of which has not been determined yet. In this paper, we assume that it is the $$0^+(2P)$$ state and obtain the transition amplitude by using the PCAC relation, low-energy theorem and effective Lagrangian method. For the 1P state, the total widths of $$D_0^*(2400)^{0}$$ and $$ D_0^*(2400)^+$$ are 226 and 246 MeV, respectively. With the assumption of $$0^+(2P)$$ state, the widths of $$D_J^*(3000)^0$$ and $$D_J^*(3000)^+$$ are both about 131 MeV, which is close to the present experimental data. Therefore, $$D_J^*(3000)$$ is a strong candidate for the $$2^3P_0$$ state.

The hypergeometric function method naturally provides the analytic expressions of scalar integrals from concerned Feynman diagrams in some connected regions of independent kinematic variables, also presents the systems of homogeneous linear partial differential equations satisfied by the corresponding scalar integrals. Taking examples of the one-loop $B_{_0}$ and massless $C_{_0}$ functions, as well as the scalar integrals of two-loop vacuum and sunset diagrams, we verify our expressions coinciding with the well-known results of literatures. Based on the multiple hypergeometric functions of independent kinematic variables, the systems of homogeneous linear partial differential equations satisfied by the mentioned scalar integrals are established. Using the calculus of variations, one recognizes the system of linear partial differential equations as stationary conditions of a functional under some given restrictions, which is the cornerstone to perform the continuation of the scalar integrals to whole kinematic domains numerically with the finite element methods. In principle this method can be used to evaluate the scalar integrals of any Feynman diagrams., Comment: 39 pages, including 2 ps figures

The mass spectra, mixing angle, and decay constants of the ${J}^{P}={1}^{+}$ heavy-light mesons are systematically studied within the framework of the Bethe-Salpeter equation (BSE). The full ${1}^{+}$ Salpeter wave function is given for the first time. The mixing between the ${1}^{+\ensuremath{-}}$ and ${1}^{++}$ in the ${1}^{+}$ heavy-light systems are automatically determined by the dynamics in the equation without any man-made mixing. The results indicate that in a rigorous study there exists the phenomenon of mixing angle inversion or mass inversion within ${1}^{+}$ heavy-light doublet, which is sensitive to the $s$-quark mass for the charmed mesons and $u$- or $d$-quark masses for the bottomed mesons. This inversion phenomenon can answer the question of why we have confused mixing angles in the literature and partly explain the lower mass of ${D}_{s1}(2460)$ compared to that of ${D}_{s1}(2536)$. The decay constants are also presented and can behave as a good quantity to distinguish the ${1}^{+}$ doublet in heavy-light mesons. This study indicates that the light-quark mass may play an important role in deciding the mass order, mixing angle, and decay constant relation between the $|{j}_{l}=\frac{3}{2}⟩$ and $|{j}_{l}=\frac{1}{2}⟩$ heavy-light mesons.

The fragmentation functions for a $c$ or $\overline{b}$ quark to a ${B}_{c}$ or ${B}_{c}^{*}$ meson are derived up to QCD next-to-leading order. They are further computed numerically and presented precisely in figures. In order to reach a higher accuracy, we also try to properly use them to estimate ${B}_{c}$ and ${B}_{c}^{*}$ production at a $Z$ factory (an ${e}^{+}{e}^{\ensuremath{-}}$ collider running at the energy of the $Z$-boson pole).

In the paper, we derive the next-to-leading order (NLO) fragmentation function for a heavy quark, either charm or bottom, into a heavy quarkonium $J/\Psi$ or $\Upsilon$. The ultra-violet divergences in the real corrections are removed through the operator renormalization, which is performed under the modified minimal subtraction scheme. We then obtain the NLO fragmentation function at an initial factorization scale, e.g. $\mu_{F}=3 m_c$ for $c\to J/\Psi$ and $\mu_{F}=3m_b$ for $b\to \Upsilon$, which can be evolved to any scale via the use of Dokshitzer-Gribov-Lipatov-Altarelli-Parisi equation. As an initial application of those fragmentation functions, we study the $J/\Psi$ ($\Upsilon$) production at a high luminosity $e^+e^-$ collider which runs at the energy around the $Z$ pole and could be a suitable platform for testing the fragmentation function., Comment: 13 pages, 11 figures

Based on the nonrelativistic quantum chromodynamics factorization formalism, the polarization parameters λθϕ and λϕ of prompt J/ψ hadroproduction for CMS and LHCb are analyzed in the helicity frame and calculated at QCD next-to-leading order for the first time. For prompt J/ψ production, we take into account the feed-down contributions from χcJ and ψ(2S) decays. The theoretical predictions for the polarization parameters λθϕ and λϕ of J/ψ are presented. Using the theoretical results, we perform a simultaneous fit to the experimental measurements of the yield and polarization of J/ψ hadroproduction, and find that the results describe the experimental measurements at the LHC quite well.

The mass spectra and wave functions for the doubly heavy baryons are computed under the picture that the two heavy quarks inside a doubly heavy baryon, such as two $c$-quarks in $\Xi_{cc}$, combine into a heavy `diquark core' in color anti-triplet firstly, then the diquark core turns into a color-less doubly heavy baryon via combining the light $q$-quark inside the baryon. Namely both of the combinations, the two heavy quarks inside the baryon into a diquark core in color anti-triplet and the heavy diquark core with the light quark into the baryon, are depicted by relativistic Bethe-Salpeter equations (BSEs) with an accordingly QCD inspired kernel respectively, although in the paper only the heavy diquark cores with the quantum numbers $J^P=1^+$ are considered. Since the `second combination' is of the heavy diquark core and the light quark, so the structure effect of the diquark core to the relevant kernel of the BSE is specially considered in terms of the diquark-core wave functions. The mass spectra and wave functions for the `low-laying' doubly heavy baryons in the flavors $(ccq)$, $(bcq)$ and $(bbq)$ and in the quantum numbers $J^P=\frac{1}{2}^+$, $J^P=\frac{3}{2}^+$, achieved by solving the equations under the so-called instantaneous approximation, are presented properly and some comparisons with the others' results under different approaches in the literature are made., Comment: 21 pages, 17 figures; To be published in Chinese Physics C

By applying the nonrelativistic quantum chromodynamics factorization formalism to hadroproduction, a complete analysis of the polarization parameters , , and for the production is presented at QCD next-to-leading order. With the long-distance matrix elements extracted from experimental data for the production rate and polarization parameter of hadroproduction, our results provide a good description of the measured parameters and in both the helicity and Collins-Soper frames. In our calculations, the frame invariant parameter is consistent in the two frames. Finally, we mention that there are discrepancies between the available experimental data and corresponding theoretical predictions for .

This paper presented the simple mesh network protocol (SMNP) for low power wide area network. The Sub1G protocol is low power wide area network member that transmission have been a research topic in smart home fields, in which Sub1G penetrated walls better than 2.4GHz protocol transmission in house. We simplify tradition complex mesh network protocol to construct easy protocol in smart home. The features of SMNP used dual rule which are broadcast and assignment in transmission process, and most of the time system is sleep to reduce power consumption. In addition, the SMNP have no specific rule that including coordinator, router and node which everyone are access point. Therefore, the SMNP methods have satisfactory response with low power and easy construct in internet of things fields.

This paper presented a proximity capacitive gesture recognition with fuzzy identify system. The smart home securities have been a research topic in internet of thing fields that securities algorithms build in real time processor to recognize user identification. Recently, the capacitive sensor technologies have been developed for proximity method that sensing electronic varies around sensor detection point, and the trend of low prices device in smart home market is an important elements. Hence, we utilize microcontroller with fuzzy expert knowledge identify algorithms to implement proximity capacitive gesture recognition. In the experimental results, we show the different gesture signal and fuzzy expert knowledge recognized there patterns. In addition, we used wearable device combined BLE (Bluetooth low energy) feedback output response real time.

We present an approach to analyze the scalar integrals of any Feynman diagrams in detail here. This method not only completely recovers some well-known results in the literature, but also produces some brand new results on the $C_{_0}$ function. The approach can be employed to evaluate the coefficient of arbitrary power of $\varepsilon$ in the expansion of a scalar integral, where $D=4-2\varepsilon$ denotes the time-space dimension., Latex, 68 pages

In the paper, we make a comprehensive study of the hadroproduction of the ${B}_{c}({B}_{c}^{*})$ meson via the gluon-gluon fusion mechanism at the RHIC and LHC colliders. Total and differential cross sections via the proton-nucleus ($p\text{\ensuremath{-}}\mathrm{N}$) and nucleus-nucleus (N-N) collision modes have been discussed under various collision energies. To compare with those via the proton-proton collision mode at the LHC, we observe that a sizable number of ${B}_{c}({B}_{c}^{*})$-meson events can also be produced via the $p\text{\ensuremath{-}}\mathrm{N}$ and N-N collision modes at the RHIC and LHC. If assuming the spin-triplet ${B}_{c}^{*}$ meson directly decays to the spin-singlet ${B}_{c}$ meson with 100% probability, $1.2\ifmmode\times\else\texttimes\fi{}{10}^{5}$ and $4.7\ifmmode\times\else\texttimes\fi{}{10}^{5}$ ${B}_{c}$-meson events can be produced via the $p\text{\ensuremath{-}}\mathrm{Au}$ and Au-Au collision modes at the RHIC in one operation year, and $5.8\ifmmode\times\else\texttimes\fi{}{10}^{6}$ and $4.6\ifmmode\times\else\texttimes\fi{}{10}^{6}$ ${B}_{c}$-meson events can be produced via the $p\text{\ensuremath{-}}\mathrm{Pb}$ and Pb-Pb collision modes at the LHC in one operation year.

In this paper, we systematically calculate two-body strong decays of newly observed ${D}_{J}(3000)$ and ${D}_{sJ}(3040)$ with $2\mathrm{P}({1}^{+})$ and $2\mathrm{P}({1}^{+\ensuremath{'}})$ assignments in an instantaneous approximation of the Bethe-Salpeter equation method. Our results show that both resonances can be explained as the $2\mathrm{P}({1}^{{+}^{\ensuremath{'}}})$ with broad width via $^{3}{P}_{1}$ and $^{1}{P}_{1}$ mixing in $D$ and ${D}_{s}$ families. For ${D}_{J}(3000)$, the total width is 229.6 MeV in our calculation, close to the upper limit of experimental data, and the dominant decay channels are ${D}_{2}^{*}\ensuremath{\pi}$, ${D}^{*}\ensuremath{\pi}$, and ${D}^{*}(2600)\ensuremath{\pi}$. For ${D}_{sJ}(3040)$, the total width is 157.4 MeV in our calculation, close to the lower limit of experimental data, and the dominant channels are ${D}^{*}K$ and ${D}^{*}{K}^{*}$. These results are consistent with observed channels in experiments. Given the very little information that has been obtained from experiments and the large error bars of the total decay widths, we recommend the detection of dominant channels in our calculation.

We present a detailed discussion on the doubly charmed baryon $\Xi_{cc}$ production at the RHIC and LHC via the proton-nucleus ($p$-N) and nucleus-nucleus (N-N) collision modes. The extrinsic charm mechanism via the subprocesses $g+c\to (cc)[n]+\bar{c}$ and $c+c\to (cc)[n]+g$ together with the gluon-gluon fusion mechanism via the subprocess $g+g\to(cc)[n]+\bar{c}+\bar{c}$ have been taken into consideration, where the intermediate diquark is in $[n]=[^1S_0]_{\bf 6}$-state or $[^3S_1]_{\bar{\bf 3}}$-state, respectively. Total and differential cross sections have been discussed under various collision energies. To compare with the $\Xi_{cc}$ production via proton-proton collision mode at the LHC, we observe that sizable $\Xi_{cc}$ events can also be generated via $p$-N and N-N collision modes at the RHIC and LHC. For examples, about $8.1\times10^7$ and $6.7\times10^7$ $\Xi_{cc}$ events can be accumulated in $p$-Pb and Pb-Pb collision modes at the LHC within one operation year., Comment: 10 pages, 6 figures

The reflection energy loss of a cavity receiver is complicated due to the structure of multi-surface inside the cavity. Based on the assumption of semi-gray diffuse reflection, a fast model is proposed to solve the problem. During the calculation, each panel is treated as a semi-gray diffuse reflecting surface. The solar radiation energy transfer between different surfaces is also considered. The fast model is then used to calculate the reflection energy loss of a molten salt cavity receiver with known view factors. The result is compared with values calculated through other models, and the fast model is proved effective to calculate the reflection energy loss of cavity receivers.

The two tank molten salt thermal storage system is widely used in the commercialized solar thermal power plant. However, the thermocline storage system with a low-cost filler material is a more economically feasible option. In this study, a transient two-dimensional and two-temperature model is developed to investigate the heat transfer and fluid dynamics in a molten salt thermocline thermal storage system. After model validation, the effects of inlet flow boundary condition and storage medium properties including fluid and solid materials on the thermal performance of thermocline storage system are investigated. The results show that thermoclne thickness increases slowest with solar salt as heat transfer fluid (HTF) and Cofalit® as solid material in the thermocline tank. Any non-uniformity in the inlet velocity flow would only enhance mixing and widen the thermocline appreciably, which contributes to the loss of thermodynamic availability of stored energy. The thermocline thickness increases with the non-uniformity of the inlet velocity boundary condition. So smaller non-uniformity of inlet flow is better in non-uniform flow though it may causes larger fluctuations in average outlet temperature. Smaller inlet mass flow rate is better for the thermocline storage tank, while it also causes smaller discharging power. With the chosen basic design parameters such as fluid and solid materials, the size of a 2MWh thermocline tank is determined by a simple one-dimensional design method. Tank with larger H/D ratio has higher discharge efficiency. It helps to figure out the thermal stratification mechanism of a storage tank and thereby to determine optimum design and operating conditions.

A numerical study was undertaken for investigating the heat transfer enhancement in a molten salt solar receiver tube with the twisted tapes. Various parameters of twisted tapes are studied in this paper. Comparisons of the Nusselt number and friction factor of twisted tape with previous correlation are made to evaluate the turbulence models used. Effects of the clearance ratios (C=0 (tight fit), 0.2, 0.5, 0.7 and 1) and twist ratios (γ=2.5, 5.0, 12.5, 15.6, 25, 41.7) on heat transfer rate (Nu), friction factor (f) are examined under non-uniform heat flux using molten salt as the testing fluid. Furthermore, the influence of grid generation on prediction results is also reported. Numerical calculations were performed with FLUENT 6.3.2 code, in the range of Reynolds number 7485-30553. The results show that the insert twisted tape can significantly improve the uniformity of temperature distribution of tube wall and molten salt. The decreases of clearance rate C and twisted rate γ can enhance the heat transfer effectively. Especially when clearance rate C=0, that is the heat transfer enhancement effect with tight-fit twisted tape is the most significant. But at the same time, the decreases of clearance rate and twisted rate also lead to increase the friction factor. These methods and results can be extended to the heat transfer enhancement of all the solar concentrated receivers.

The semileptonic decays \(B_c^ + \to P(V) + \ell ^ + + \bar \nu _\ell \) and the nonleptonic decays Bc+ → P(V) + L, where P(V) denotes a pseudoscalar (vector) charmonium or \((\bar bs)\)-meson, and L denotes a light meson, are studied in the framework of improved instantaneous Bethe-Salpeter (BS) equation and the Mandelstam formula. The numerical results (width and branching ratio of the decays) are presented in tables, and in order to compare conveniently, those obtained by other approaches are also put in the relevant tables. Based on the fact that the ratio \(\frac{{\mathcal{B}\mathcal{R}(B_c^ + \to \psi (2S)\pi ^ + )}} {{\mathcal{B}\mathcal{R}(B_c^ + \to J/\psi \pi ^ + )}} = 0.24_{ - 0.040}^{ + 0.023} \) estimated here is in good agreement with the observation by LHCb \(\frac{{\mathcal{B}\mathcal{R}(B_c^ + \to \psi (2S)\pi ^ + )}} {{\mathcal{B}\mathcal{R}(B_c^ + \to J/\psi \pi ^ + )}} = 0.250 \pm 0.068(stat) \pm 0.014(syst) \pm 0.006(\mathcal{B}) \), one may conclude that with respect to the decays the present framework works quite well.

The production of $B_c$ and $B_c^*$ mesons at a $Z$-factory (an $e^+e^-$ collider operating at energies around the $Z$ pole) is calculatedup to the next-to-leading order (NLO) QCD accuracy. The results show that the dependence of the total cross sections on the renormalization scale $\mu$ is suppressed by the corrections, and the NLO corrections enhance the total cross sections of $B_c$ by $52%$ and of $B_c^*$ by $33%$ when the renormalization scale is taken at $\mu=2m_b$. To observe the various behaviors of the production of the mesons $B_c$ and $B_c^*$, such as the differential cross section vs. the out-going angle, the forward-backward asymmetry, and the distribution vs. the energy fraction $z$ up to NLO QCD accuracy as well as the relevant $K$-factor (NLO to LO) for the production, are calculated, and it is pointed out that some of the observables obtained in the present work may be used as a specific precision test of the standard model.