Search

The X(6900) resonance, recently discovered in the double-J/ψ channel at the LHCb experiment, has spurred intensive interest in unraveling the nature of the fully charmed tetraquark state. The aim of this paper is to present a model-independent framework to study the inclusive production of this novel species of exotic hadrons, the resonances composed of four heavy quark (commonly referred to as T4c), at large pT in hadron colliders. Appealing to asymptotic freedom and the fact mc≫ΛQCD, we propose that the universal gluon-to-T4c fragmentation function, can be decomposed into the product of the perturbatively calculable short-distance coefficients and the long-distance nonrelativistic QCD (NRQCD) matrix elements. We compute the short-distance coefficient at lowest order in αs and velocity expansion. Adopting the phenomenological four-body wave functions at the origin to roughly estimate those not-yet-known NRQCD matrix elements, and applying the standard QCD factorization theorem, we predict the differential production rates for the T4c (0++ and 2++) at large pT in pp collision, which eagerly awaits the confrontation with the future LHC experiments.

A method of encapsulation of inorganic additives with organic materials was developed to improve the fine power flowability and film quality for powder coating. The flowability tests angle of repose (AOR) and avalanche angle (AVA) were conducted for the coating samples to characterize the effectiveness of the encapsulated additives on group C fine powder flowability. The results show that both AOR and AVA are significantly affected by the encapsulating materials, the encapsulating material weight percentage, as well as the total loading ratios of additives added in fine powders. Polyester shows the best performance on the modification of the additive due to the high similarity to host powder coating. AOR/AVA first decreases and then decreases with the encapsulating material weight. An optimum percentage exists at approximately 10%. A similar trend is observed with the additive loading ratio, and the minimal AOR/AVA is obtained at additive loading ratios between 0.5% and 0.8%. The effective surface area coefficient (η) was introduced to improve the adhesion force model to determine the optimum additive loading ratio for various host particle and additive particle sizes, which agrees well with the experimental results.

Inaction inertia is the phenomenon that forgoing an initial attractive opportunity decreases the likelihood of taking a subsequent opportunity that is less attractive, even when the subsequent opportunity still offers positive value. We conducted three preregistered replications of Tykocinski et al.’s Experiments 1 and 2’s four scenarios in four samples ( N = 1,555). We found consistent findings across samples, with the inaction inertia effect dependent on the scenario used. Strongest support was for the car scenario ( d = −0.57 to −0.68) and the ski scenario ( d = −0.18 to −0.67), with mixed findings for the fitness scenario (large-small: d = −0.62; control contrasts: opposite to predictions) and weak to no effects for the flyer scenario ( d = −0.14 to 0.02). We conclude that context is important in studying inaction inertia, recommend the car and ski scenarios for follow-up research on inaction inertia, and discuss implications for future research.

A new type of fluidized bed called Inverse Liquid-Solid Circulating Fluidized Bed (ILSCFB) has been developed. The circulating fluidized bed consists of the downer with an inner diameter of 7.6 cm and the height of 5.4 m, upcomer with an inner diameter of 20 cm, separator, and connecting pipes between the downer to the storage column. The operation window has been demonstrated at different solids circulation rate and liquid velocity. The hydrodynamic characteristics in the downer of ILSCFB are investigated experimentally by fluidization of the styrofoam and Hollow Glassbeads whose densities are smaller than that of the fluidization media. Average solids holdup in the downer is measured where different liquid velocity and different solids circulation rate in terms of superficial solids velocity. For both types of particles, axial solids holdup distribution is quite uniform under various operating conditions, while radial solids holdup distributions are slightly non-uniform with a minor increase in solids holdup adjacent to the wall under various operating conditions, but no obvious “core-annulus” structure is observed. The comparisons of the hydrodynamics in the ILSCFB and Liquid-Solid Circulating Fluidized Bed (LSCFB) are also made based on the single particle force balance discussion, enabling the generalization of inverse and upwards circulating fluidization of particles.

One-dimensional (1D) morphology-unique Au–Ag2S nano-hybrids are achieved by combining the interfacial self-assembly of Ag nanowires, interface-oriented site-specific etching of Ag nanowires with AuCl4−, and the sulfurization of S2−. The as-formed Au–Ag2S nano-hybrid has a trough-like morphology. The wall of the Au–Ag2S nanotrough is a Ag2S/Au/Ag2S trilayer wall, but the Ag2S layer is a Ag2S-rich mixture of Ag2S and Au rather than pure Ag2S because of the diffusion of Au atoms towards Ag2S. The Au–Ag2S nanotrough shows strong absorption in the visible region (400–800 nm) and exhibits a favorable photoelectrochemical (PEC) response, the photocurrent of which is ∼8.5 times larger than that of pure Ag2S. This enhanced PEC response originates from the localized plasmonic resonance effect of Au. Moreover, the PEC biosensor based on the Au–Ag2S nanotroughs shows high sensitivity and selectivity, satisfactory reproducibility, and good stability towards human α-thrombin (TB) detection: a sensitive linear response ranging from 1.00 to 10.00 pmol L−1 and a low detection limit of 0.67 pmol L−1. This study provides a new model for studying the PEC behavior of plasmonic metal/semiconductor materials, and this Au–Ag2S nanotrough may also be useful in the fields of photocatalysis and photovoltaics.

The study has shown that the shear component of the vertical integrated kinetic energy (Ks) over the box (40oE-100oE, 0-20oN) can be used to measure the intensity of the South Asian summer monsoon (SASM). Based on its value averaged between June and August, the SASM can be divided into strong and weak monsoon episodes. Between 1958 and 2018, there existed 16 (16) strong (weak) monsoon episodes. Based on the calendar year, the relationship between the SASM and ENSO episodes can be grouped into six patterns: weak monsoon - El Nino (WM-EN), normal monsoon - El Nino (NM-EN), weak monsoon - non ENSO (WM-NE), strong monsoon - La Nina (SM-LN), normal monsoon - La Nina (NM-LN) and strong monsoon - non ENSO (SM-NE). Previous studies suggest that the WM-EN and SM-LN patterns reflect the correlated relationship between the SASM and El Nino/Southern Oscillation (ENSO) events. Therefore, we name these two strongly coupled categories WM-EN and SM-LN as the resonance effect. Two important circulations, i.e., Walker circulation (WC) and zonal Asian monsoon circulation (MC), in the vertical plane are found to be not always correlated. The MC is controlled by thermal gradients between the Asian landmass and the tropical Indian Ocean, while the WC associated with ENSO events is primarily the east-west thermal gradient between the tropical South Pacific and the tropical Indian Ocean. Furthermore, the gradient directions caused by different surface thermal conditions are different. The main factor for the resonance effect is the phenomenon that the symbols of SSTA in the tropical Indian Ocean and the equatorial eastern Pacific are the same, but are opposite to that of the SSTA near the maritime continent.

We apply the newly developed NRQCD factorization formula to analyze the exclusive production of the fully-charmed tetraquark $T_{4c}$ plus a hard photon at $B$ factory. For simplicity, in this work we have concentrated on the associated production of the $0^{++}$ and $2^{++}$ tetraquarks with a photon. With some rough estimates about the size of the unknown nonperturbative NRQCD matrix elements, we predict the production rates of these types of exclusive channels at $\sqrt{s}=10.6$ GeV and also assess their observation prospect at {\tt Belle 2} experiment., Comment: 11 pages, 3 figures

To develop durable and low-price catalysts of methanol oxidation to commercialize direct methanol fuel cell, many attempts have been made at fabricating Pt-based hybrids by designing component-, morphology-, facet-, integration-pattern-varied nanostructures, and have achieved considerable successes. However, most of present catalysts still lack robust catalytic durability especially owing to the corrosion of mixed carbon and the poor mechanical stability of catalyst layer. Herein, Te nanowire array is transformed at an air/water interface into a 3D Pt

Within the framework of nonrelativistic QCD factorization formalism, we compute the helicity amplitude as well as the decay width of ${\ensuremath{\eta}}_{Q2}$ ($Q=c$, $b$) electromagnetic decay into two photons up to next-to-next-to-leading order in ${\ensuremath{\alpha}}_{s}$ expansion. For the first time, we verify the validity of nonrelativistic QCD factorization for the $D$-wave quarkonium decay at next-to-next-to-leading order. We find that the $\mathcal{O}({\ensuremath{\alpha}}_{s})$ and $\mathcal{O}({\ensuremath{\alpha}}_{s}^{2})$ corrections to the helicity amplitude are negative and moderate, nevertheless both corrections combine to suppress the leading-order prediction for the decay width significantly. By approximating the total decay width of ${\ensuremath{\eta}}_{Q2}$ as the sum of those for the hadronic decay and the electric $E1$ transition, we obtain the branching ratios $\text{Br}({\ensuremath{\eta}}_{c2}\ensuremath{\rightarrow}2\ensuremath{\gamma})\ensuremath{\approx}5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ and $\text{Br}({\ensuremath{\eta}}_{b2}\ensuremath{\rightarrow}2\ensuremath{\gamma})\ensuremath{\approx}4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$. To explore the potential measurement on ${\ensuremath{\eta}}_{Q2}$, we further evaluate the production cross section of ${\ensuremath{\eta}}_{Q2}$ at LHCb at the lowest order in ${\ensuremath{\alpha}}_{s}$ expansion. With the kinematic constraint on the longitudinal rapidity $4.5gyg2$ and transverse momentum ${P}_{T}g(2--4){m}_{Q}$ for ${\ensuremath{\eta}}_{Q2}$, we find the cross section can reach 2--50 nb for ${\ensuremath{\eta}}_{c2}$, and 1--22 pb for ${\ensuremath{\eta}}_{b2}$. Considering the integrated luminosity $\mathcal{L}=10\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ at $\sqrt{s}=7$, 13 TeV, we estimate that there are several hundreds events of $pp\ensuremath{\rightarrow}{\ensuremath{\eta}}_{c2}\ensuremath{\rightarrow}2\ensuremath{\gamma}$. Since the background is relatively clean, it is promising to reconstruct ${\ensuremath{\eta}}_{c2}$ through its electromagnetic decay. On the other hand, due to the small branching ratio and production cross section, it is quite challenging to detect ${\ensuremath{\eta}}_{b2}\ensuremath{\rightarrow}2\ensuremath{\gamma}$ at LHCb.

In the paper, we present QCD predictions for $\eta_{c} + \gamma$ production at an electron-position collider up to next-to-next-to-leading order (NNLO) accuracy without renormalization scale ambiguities. The NNLO total cross-section for $e^{+}+e^{-}\to\gamma+\eta_{c}$ using the conventional scale-setting approach has large renormalization scale ambiguities, usually estimated by choosing the renormalization scale to be the $e^+ e^-$ center-of-mass collision energy $\sqrt{s}$. The Principle of Maximum Conformality (PMC) provides a systematic way to eliminate such renormalization scale ambiguities by summing the nonconformal $\beta$ contributions into the QCD coupling $\alpha_s(Q^2)$. The renormalization group equation then sets the value of $\alpha_s$ for the process. The PMC renormalization scale reflects the virtuality of the underlying process, and the resulting predictions satisfy all of the requirements of renormalization group invariance, including renormalization scheme invariance. After applying the PMC, we obtain a scale-and-scheme independent prediction, $\sigma|_{\rm NNLO, PMC}\simeq 41.18$ fb for $\sqrt{s}$=10.6 GeV. The resulting pQCD series matches the series for conformal theory and thus has no divergent renormalon contributions. The large $K$ factor which contributes to this process reinforces the importance of uncalculated NNNLO and higher-order terms. Using the PMC scale-and-scheme independent conformal series and the $\rm Pad\acute{e}$ approximation approach, we predict $\sigma|_{\rm NNNLO, PMC+Pade} \simeq 21.36$ fb, which is consistent with the recent BELLE measurement $\sigma^{\rm obs}$=$16.58^{+10.51}_{-9.93}$ fb at $\sqrt{s} \simeq 10.6$ GeV. This procedure also provides a first estimate of the NNNLO contribution., Comment: 8 pages, 5 figures. Discussions improved and references updated. Revised version to be published in JHEP

Within NRQCD factorization framework, in this work we compute, at the lowest order in velocity expansion, the next-to-leading-order (NLO) perturbative corrections to the short-distance coefficients associated with heavy quark fragmentation into the ${}^1S_0^{(1,8)}$ components of a heavy quarkonium. Starting from the Collins and Soper's operator definition of the quark fragmentation function, we apply the sector decomposition method to facilitate the numerical manipulation. It is found that the NLO QCD corrections have a significant impact., Comment: 11 pages, 2 figures

Within the nonrelativistic QCD (NRQCD) factorization framework, we compute the $\mathcal{O}({\ensuremath{\alpha}}_{s}{v}^{2})$ corrections to the hadronic decay rate of vector quarkonia, exemplified by $J/\ensuremath{\psi}$ and $\mathrm{\ensuremath{\Upsilon}}$. Setting both the renormalization and NRQCD factorization scales to be ${m}_{Q}$, we obtain $\mathrm{\ensuremath{\Gamma}}(J/\ensuremath{\psi}\ensuremath{\rightarrow}\mathrm{LH})=0.0716\frac{{\ensuremath{\alpha}}_{s}^{3}}{{m}_{c}^{2}}⟨{\mathcal{O}}_{1}({^{3}S}_{1}){⟩}_{J/\ensuremath{\psi}}[1\ensuremath{-}1.19{\ensuremath{\alpha}}_{s}+(\ensuremath{-}5.32+3.03{\ensuremath{\alpha}}_{s})⟨{v}^{2}{⟩}_{J/\ensuremath{\psi}}]$ and $\mathrm{\ensuremath{\Gamma}}(\mathrm{\ensuremath{\Upsilon}}\ensuremath{\rightarrow}\mathrm{LH})=0.0716\frac{{\ensuremath{\alpha}}_{s}^{3}}{{m}_{b}^{2}}⟨{\mathcal{O}}_{1}({^{3}S}_{1}){⟩}_{\mathrm{\ensuremath{\Upsilon}}}[1\ensuremath{-}1.56{\ensuremath{\alpha}}_{s}+(\ensuremath{-}5.32+4.61{\ensuremath{\alpha}}_{s})⟨{v}^{2}{⟩}_{\mathrm{\ensuremath{\Upsilon}}}]$. We confirm the previous calculation of $\mathcal{O}({\ensuremath{\alpha}}_{s})$ corrections on a diagram-by-diagram basis, with the accuracy significantly improved. For $J/\ensuremath{\psi}$ hadronic decay, we find that the $\mathcal{O}({\ensuremath{\alpha}}_{s}{v}^{2})$ corrections are moderate and positive, nevertheless unable to counterbalance the huge negative corrections. On the other hand, the effect of $\mathcal{O}({\ensuremath{\alpha}}_{s}{v}^{2})$ corrections for $\mathrm{\ensuremath{\Upsilon}}(nS)$ is sensitive to the $\mathcal{O}({v}^{2})$ NRQCD matrix elements. With the appropriate choice of the NRQCD matrix elements, our theoretical predictions for the decay rates may be consistent with the experimental data for $\mathrm{\ensuremath{\Upsilon}}(1S,2S)\ensuremath{\rightarrow}\mathrm{LH}$. As a by-product, we also present the theoretical predictions for the branching ratio of $J/\ensuremath{\psi}(\mathrm{\ensuremath{\Upsilon}})\ensuremath{\rightarrow}3\ensuremath{\gamma}$ accurate up to $\mathcal{O}({\ensuremath{\alpha}}_{s}{v}^{2})$.

Within the nonrelativistic QCD (NRQCD) factorization framework, we have computed the $$ \mathcal{O}\left({\alpha}_s^2\right) $$ O α s 2 corrections to the exclusive production of P-wave spin-triplet charmonia χcJ (J = 0, 1, 2) accompanied with a hard photon at B factory. For the first time, we have explicitly verified the validity of NRQCD factorization for exclusive P-wave quarkonium production to two-loop order. Unlike the χcJ electromagnetic decays, the $$ \mathcal{O}\left({\alpha}_s^2\right) $$ O α s 2 corrections are found to be smaller than the $$ \mathcal{O} $$ O (αs) corrections in all three channels e+e− → χc0,1,2 + γ. In particular, the $$ \mathcal{O}\left({\alpha}_s^2\right) $$ O α s 2 corrections appear moderate for χc1 + γ case, and marginal for χc0 + γ. Moreover, the predictions in next-to-next-to-leading order (NNLO) accuracy for the production rates of χc0,1 + γ are insensitive to the renormalization and factorization scales. All these features may indicate that perturbative expansion in these two channels exhibits a decent convergence behavior. By contrast, both the $$ \mathcal{O} $$ O (αs) and $$ \mathcal{O}\left({\alpha}_s^2\right) $$ O α s 2 corrections to the χc2 + γ production rate are sizable, which reduce the Born order cross section by one order of magnitude after including the NNLO perturbative corrections. Taking the values of the long-distance NRQCD matrix elements from nonrelativistic potential model, our prediction to χc1 + γ production rate is consistent with the recent Belle measurement. The NNLO predictions to the χc0,2 + γ production rates are much smaller than that for χc1 + γ, which seems to naturally explain why the e+e− → χc0,2 + γ channels have escaped experimental detection to date.

One-dimensional (1D) morphology-unique Au-Ag

Cracks and other diseases may occur in the long-term operation of highway tunnels and reduce the structural load-carrying capacity. Strengthening using carbon fiber reinforced polymer (CFRP) sheets and other materials could extend the service time of the tunnels. However, the process of strengthening tunnels is remarkably different from the process of strengthening aboveground structures because of the secondary load. In order to understand the development of stress and deformation of strengthened tunnels under secondary load, a 1 : 10 scaled model was tested to simulate the tunnel strengthened with CFRP under different damage states. The test results show that CFRP strengthening improved the stiffness of the structure and inhibited the propagation of the existing cracks. The peeling of the CFRP sheets made the strengthened structure quickly lose its load-carrying capacity, causing the instability of the structure. The failure loads of the structures strengthened at different damage states were essentially the same, with an average value of 184% of the original failure load. Nevertheless, the early strengthening helped control the structural deformation. The test results also demonstrate that the bonding strength between the CFRP and the lining is essential for strengthening effectiveness. This study provides a theoretical basis for similar engineering reinforcement designs.

Supplemental Material, SPPS-RNR-Inaction_Inertia-replication-v1-supplementary-lengthened-G for Foregone Opportunities and Choosing Not to Act: Replications of Inaction Inertia Effect by Jieying Chen, Long Sang Hui, Teresa Yu, Gilad Feldman, Shiyuan Zeng, Tze Lam Ching, Chi Ho Ng, Kwok Wai Wu, Chung Man Yuen, Tsz Ki Lau, Bo Ley Cheng and Ka Wai Ng in Social Psychological and Personality Science

AuPt alloy catalysts with various compositions have been successfully prepared simply by one-step co-reduction of Au and Pt precursors involving sodium citrate as stabilizer and reductant. XRD, TEM and EDX element mapping analysis confirmed that the resulting AuPt nanoparticles are single-phase alloys rather than random mixtures of tiny Au and Pt particles. Compared with Pt/C, alloying Au with Pt can effectively alter the kinetic process of formic acid oxidation, reducing the generation of CO-like intermediates. Au81Pt19 displays superior electrocatalytic activity and durability, ~11 times in the mass activity better than commercial Pt/C and may be of practical significance for the commercialization of direct formic acid fuel cell.

To develop durable and low-price catalysts of methanol oxidation to commercialize direct methanol fuel cell, many attempts have been made at fabricating Pt-based hybrids by designing component-, morphology-, facet-, integration-pattern-varied nanostructures, and have achieved considerable successes. However, most of present catalysts still lack robust catalytic durability especially owing to the corrosion of mixed carbon and the poor mechanical stability of catalyst layer. Herein, Te nanowire array is transformed at an air/water interface into a 3D Pt16 Te hierarchical nanostructure via an interface-confined galvanic replacement reaction. As-formed Pt16 Te nanostructure has an asymmetrical architecture composed of nanotroughs and nanopillars, and nanopillars are perpendicular to nanotroughs with a loose arrangement. Pt16 Te hierarchical nanostructure has a "self-supported" feature and, when directly used as the catalyst of methanol electrooxidation, exhibits superior catalytic activity (>four times larger in mass activity than state-of-the-art Pt/C in either acidic or basic solution) and long-term durability (after 500 cycles of cyclic voltammetric measurement, more than 55% of the initial specific activity remains whereas Pt/C only remains 22.2% in acidic solution and almost loses all activity in basic solution). This study fully demonstrates that designing "self-supported" catalyst film may be the next promising step for improving the catalytic performance of Pt-based hybrids.

We study the ${\ensuremath{\eta}}_{c}$ photoproduction in $ep$ collisions in this paper. The short-distance coefficients for $c\overline{c}(^{1}{S}_{0}^{[1]})$, $c\overline{c}(^{1}{S}_{0}^{[8]})$, $c\overline{c}(^{3}{S}_{1}^{[8]})$, and $c\overline{c}(^{1}{P}_{1}^{[8]})$ photoproductions via both direct and resolved photons are evaluated at leading order in ${\ensuremath{\alpha}}_{s}$ expansion, where the color-singlet contribution is achieved for the first time. The dependence of the cross sections on the renormalization and factorization scales, and the charm quark mass is studied in this paper. As an interesting result, the color-singlet cross section is dominated by the resolved photoproduction, which is almost two orders of magnitude larger than the contributions from the direct photons. The resolved photoproduction also enhances the color-octet cross sections considerably. By including the contributions from direct and resolved photons, we find the color-singlet channel dominates the integrated cross section. Making use of different sets of long-distance matrix elements, we observe some apparently distinguishable predictions, which can be utilized to scrutinize the validity of these matrix elements. Moreover, we carefully analyze different kinematic distributions of the cross sections and find that, in high ${p}_{t}$ regions, the color-singlet contribution is considerably suppressed comparing with the color-octet parts for most sets of long-distance matrix elements. This feature renders the ${\ensuremath{\eta}}_{c}$ photoproduction process another laboratory to test the color-octet mechanism in nonrelativistic QCD.

Hierarchical nanostructures are very universal in the natural world. However, to date most of synthetic approaches are just capable of producing simple nanomaterials, such as nanospheres, nanorods, nanowires, nanopolyhedrons, etc. Fabrication of complex nanostructures has to depend on the assembly of single nano-building blocks and e-beam lithography. Thus, it is imperative to create complex nanostructures by direct synthetic methods. Herein, three-dimensional fern-like Au nanostructures (3DFGNs) were achieved simply by one-step glycine-assisted electrodeposition. The effects of glycine concentration, electrode substrate and deposition potential on the growth of Au nanostructures were explored. Over the range of glycine concentration from 1.0 mmol/L to 10 mmol/L, all Au nanostructures are 3DFGNs except for the difference of the average diameter of branches. The oriented growth of 3DFGN is attributed to the specific adsorption of NH2 groups of glycine. Each fern-like dendrite of 3DFGN is a four-fold symmetric single-crystal growing along the (111) direction. As-prepared 3DFGNs show morphology- and size-dependent electrocatalytic performance towards methanol oxidation. Optimized 3DFGN exhibits satisfactory electrocatalytic activity and long-term durability, ∼3 times in the specific activity better than island-like Au aggregates electrodeposited without glycine.

Inorganic solution processed CsPbBr3 perovskite thin films are highly promising optoelectronic materials and have been applied in solar cells, light emitting diodes, and photodetectors. They show good electroluminescence properties combined with high thermal stability. In this work, CsPbBr3 perovskite thin films doped with a series of organic cations of various chain lengths, namely, methylammonium (MA), ethylammonium (EA), butylammonium (BA) and octylammonium (OA) at optimized molar ratios of (organic cations: Cs+), were fabricated with a two-step solution process. The crystalline structure, surface morphology and photophysical properties of the films were characterized in detail. The surface morphology of the films was improved with reduced surface roughness, accompanying by doping with the organic cations. The amplified spontaneous emissions (ASE) were observed from all of the different CsPbBr3 films at room temperature. The gain coefficients for the doped CsPbBr3 films were higher than the pristine films, due to much reduced bulk defects, reduced non-radiative recombination in the films, as well as improved surface quality of the films. This work provides a simple method of preparing organic cations modified CsPbBr3 laser gain media of high performance.

The next-to-next-to-leading-order (NNLO) pQCD prediction for the $\ensuremath{\gamma}{\ensuremath{\gamma}}^{*}\ensuremath{\rightarrow}{\ensuremath{\eta}}_{c}$ form factor was evaluated in 2015 using nonrelativistic QCD (NRQCD). A strong discrepancy between the NRQCD prediction and the BABAR measurements was observed. Until now there has been no solution for this puzzle. In this paper, we present a NNLO analysis by applying the Principle of Maximum Conformality (PMC) to set the renormalization scale. By carefully dealing with the light-by-light diagrams at the NNLO level, the resulting high precision PMC prediction agrees with the BABAR measurements within errors, and the conventional renormalization scale uncertainty is eliminated. The PMC is consistent with all of the requirements of the renormalization group, including scheme-independence. The application of the PMC thus provides a rigorous solution for the $\ensuremath{\gamma}{\ensuremath{\gamma}}^{*}\ensuremath{\rightarrow}{\ensuremath{\eta}}_{c}$ form factor puzzle, emphasizing the importance of correct renormalization scale-setting. The results also support the applicability of NRQCD to hard exclusive processes involving charmonium.

The prospective Higgs factories, exemplified by ILC, FCC-ee and CEPC, plan to conduct precision Higgs measurements at the ${e}^{+}{e}^{\ensuremath{-}}$ center-of-mass energy around 250 GeV. The cross sections for the dominant Higgs production channel, the Higgsstrahlung process, can be measured to a (sub)percent accuracy. Merely incorporating the well-known next-to-leading-order (NLO) electroweak corrections appears to be far from sufficient to match the unprecedented experimental precision. In this work, we make an important advancement toward this direction by investigating the mixed electroweak-QCD corrections to ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}HZ$ at next-to-next-to-leading order (NNLO) for both unpolarized and polarized $Z$ bosons. The corrections turn out to reach the 1% level of the Born order results, and thereby must be incorporated in future confrontations with the data.