Weak Decays Research Articles

Biogeography and environmental drivers of zooplankton communities in permafrost-affected lakes on the Qinghai-Tibet Plateau

Global warming is accelerating permafrost thaw, forming new thermokarst lakes and substantially influencing the old ones. However, the biological communities in thermokarst lakes on the Qinghai-Tibet Plateau (QTP) are rarely studied. Here, we assessed the biogeographical patterns of zooplankton communities in 44 thermokarst lakes across the QTP. Across all lakes, 17 Cladocera and 13 Copepoda species were identified, with most of the lakes dominated by Cladocera. Chydorus sphaericus and Cyclops vicinus were the most frequently detected species. Both cladoceran and copepod communities had very low species richness and density, which lacked a clear spatial pattern but positively associated to dissolved oxygen. In general, species richness was negatively influenced by seston particle quantity while the density was positively influenced by water nutrient concentrations. Cladoceran and copepod communities had a high β-diversity (0.89 and 0.91, respectively), which was dominated by species turnover. However, Cladocera had significantly lower β-diversity and turnover component than copepod communities. β-diversity of Cladocera and Copepoda showed a significant but weak distance decay relationship and also significantly correlated with longitude, latitude, mean annual temperature, as well as concentrations of seston particle carbon and nitrogen. In addition, their β-diversities differentially correlated to other environmental variables. Overall, the results suggested that the geographical barriers, climate, and some local environmental variables are key factors in shaping the biogeography of zooplankton community. Although a general biogeographic pattern of zooplankton across the QTP cannot be drawn from this limited dataset, this study provided the first large spatial scale investigation and analyses of zooplankton biogeography in thermokarst lakes on the QTP. Given the important roles of zooplankton in aquatic ecosystems, this study could provide insights for understanding the influences of future environmental changes on thermokarst lake ecosystems.

Global Weak Solution, Uniqueness and Exponential Decay for a Class of Degenerate Hyperbolic Equation

This paper deals with existence, uniqueness and energy decay of solutions to a degenerate hyperbolic equations given by \begin{align*} K(x,t)u'' - M\left(\int_\Omega |\nabla u|^2\,dx \right) \Delta u - \Delta u' = 0, \end{align*} with operator coefficient $K(x,t)$ satisfying suitable properties and $M(\,\cdot \,) \in C^1([0, \infty))$ is a function which greatest lower bound for $ M (\,\cdot\,) $ is zero. For global weak solution and uniqueness we use the Faedo-Galerkin method. Exponential decay is proven by using a theorem due to M. Nakao.

Production of Pc states in Λb decays

We develop a model for the production of the Pc states observed at LHCb in Lambdab - Jpsi p K- decays. With fewer parameters than other approaches, we obtain excellent fits to the Jpsi-p invariant mass spectrum, capturing both the prominent peaks, and broader features over the full range of invariant mass. A distinguishing feature of our model is that whereas Pc(4312), Pc(4380), and Pc(4440) are resonances with Sigmac*-D* constituents, the nature of Pc(4457) is quite different, and can be understood either as a Sigmac-D* threshold cusp, a Lambdac(2595)-D enhancement due to the triangle singularity, or a Lambdac(2595)-D resonance. We propose experimental measurements that can discriminate among these possibilities. Unlike in other models, our production mechanism respects isospin symmetry and the empirical dominance of colour-enhanced processes in weak decays, and additionally gives a natural explanation for the overall shape of the data. Our model is consistent with experimental constraints from photoproduction and Lambdab - Lambdac-D(*)0 K- decays and it does not imply the existence of partner states whose apparent absence in experiments is unexplained in other models.

Beta decay and electron capture rates of manganese isotopes in astrophysical environments

The isotopes of manganese in the mass range of A=53−63 are abundant in the core materials of high-mass stars and they are considered to be of prime importance in the progression of the pre-collapse phases. During these late evolutionary phases, nuclear processes associated with weak interactions, including β−-decay and electron capture (EC) of these isotopes, significantly alter the lepton to baryon ratio (Ye) in the core’s composition. The temporal change in this parameter is one of the basic elements used to simulate a successful explosion. Hence, the β−-decay and EC rates of manganese (Mn) nuclides may serve as important inputs in the simulation codes for core-collapse supernova. In this study, we investigated the weak decay characteristics of 55−63Mn nuclides. The strength distributions of Gamow–Teller transitions in the directions of β−-decay and EC were calculated for these isotopes using the proton–neutron quasi-particle random-phase approximation (pn-QRPA) model. The β-decay half-life values of Mn isotopes under terrestrial conditions were computed and compared with measured data and previous calculations. The pn-QRPA estimated half-lives were in good agreement with the experimental values. The β− and EC rates were then calculated over a large range of stellar temperatures (0.01−30)×109K and densities (10−1011) g/cm3. The computed rates were compared with previous calculations performed using the large-scale shell model (LSSM) and independent particle model (IPM). For most of the isotopes, in high temperature and density regimes, the pn-QRPA calculated β−-decay rates were smaller than the LSSM and IPM rates by up to an order of magnitude. By contrast, the EC rates were larger by up to an order of magnitude (factor of 3−10) at high temperature compared with the LSSM (IPM) results.

Feasibility of searching for the Cabibbo-favored D*→K¯π+ , K¯*π+ , K¯ρ+ decays

The current knowledge on the $D^{\ast}$ mesons are still inadequate. Encouraged by the positive development prospects of high-luminosity and high-precision experiments, the Cabibbo-favored nonleptonic $D^{\ast}$ ${\to}$ $\bar{K}{\pi}^{+}$, $\bar{K}^{\ast}{\pi}^{+}$, $\bar{K}{\rho}^{+}$ weak decays are studied with the naive factorization approach. It is found that branching ratios of these processes can reach up to ${\cal O}(10^{-10})$ or more, and can be accessible at STCF, CEPC, FCC-ee and LHCb@HL-LHC experiments in the future. It might even be possible to search for the $D^{{\ast}0}$ ${\to}$ $K^{{\ast}-}{\pi}^{+}$ and $K^{-}{\rho}^{+}$ decays at the running SuperKEKB experiments.

Weak decays of triply heavy baryons in light front approach

We analyze weak decays of triply heavy baryon Ωccc++ and calculate the form factors for Ωccc++→Ξcc++/Ωcc+ transitions in a light front quark model. The momentum distributions in form factors are accessed via the pole-model parametrization. Using the results for form factors, we predict decay branching fractions for semi-leptonic decays, and obtain B(Ωccc++→Ξcc+e+νe)=0.08%, B(Ωccc++→Ωcc+e+νe)=1.23%. Forward-backward asymmetry and angular distributions are then investigated in this work. We also estimate branching fractions for a few color-allowed processes and find that the Ωccc++→Ωcc+π+ has a sizable branching fraction: B(Ωccc++→Ωcc+π+)=1.82%. We point out that the Ωccc++→Ωcc+π+ is a golden channel for the discovery of the Ωccc++. This analysis can provide a useful reference for future experimental search in future.

Acetylene black interlayer regulated sulfur deposition for lithium-sulfur batteries with high utilization and long-term life

Lithium-sulfur (Li-S) batteries are considered to be competitive next-generation energy storage systems. However, practical applications are limited due to the shuttle of lithium polysulfides (LiPSs) and the poor electronic conductivity of the sulfur cathode, especially at high-rate currents. Here, we applied commercialized Acetylene black (AB) as separator coating in Li-S batteries. The stacking of AB nanospheres forms a void space that can physically adsorb polysulfides, store electrolytes, and promote lithium-ion diffusion; Simultaneously, it forms an excellent electronic conduction network that significantly improves the utilization of higher-order LiPSs. The thickness and composition of the coating can regulate the nucleation of crystalline S and Li2S to promote the uniform deposition of solid-phase particles. AB-150 releases an initial capacity of 961.3 mAh g−1 and still maintains at 825 mAh g−1 after 100 cycles with a capacity retention rate of 85.8% at 0.2C. Even remains at 371.2 mAh g−1 after 1000 cycles at 1C with a weak capacity decay rate of 0.06% per cycle. These understandings can also be extended to the design of polar/catalytic interlayer materials driving the large-scale application of Li-S batteries.

Analysis of FCNC ΞQQ→ΛQl+l− decay in light-cone sum rules

The weak decays of doubly heavy ${\mathrm{\ensuremath{\Xi}}}_{QQ}$ baryon induced by flavor changing $b\ensuremath{\rightarrow}d$ and $c\ensuremath{\rightarrow}u$ flavor changing neutral current within the light-cone sum rules are studied. The sum rules are constructed and analyzed for the corresponding transition form factors using the parallel components of the light-cone distribution amplitudes for ${\mathrm{\ensuremath{\Lambda}}}_{Q}$ baryon. Having the results for the form factors, the corresponding branching ratios for ${\mathrm{\ensuremath{\Xi}}}_{QQ}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{Q}{l}^{+}{l}^{\ensuremath{-}}$ decays are estimated. While the branching ratio due to $b\ensuremath{\rightarrow}d$ transition is around ${10}^{\ensuremath{-}9}$, in $c\ensuremath{\rightarrow}u$ transition case, it is found as around ${10}^{\ensuremath{-}13}$. Hence, ${\mathrm{\ensuremath{\Xi}}}_{bb}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{b}{l}^{+}{l}^{\ensuremath{-}}$ decay has the potential of being discovered at LHCb. However, ${\mathrm{\ensuremath{\Xi}}}_{bb}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{b}{l}^{+}{l}^{\ensuremath{-}}$ is difficult to be measured due to the extremely small values of obtained branching ratio. Our results on the branching ratio are also compared with the results of the light-front approach.

Mixed convection flow from a convectively heated vertical porous plate with combined effects of suction/injection, internal heat generation and nonlinear thermal radiation

This article explored the mixed convection flow from a convectively heated vertical porous plate influenced by nonlinear thermal radiation with suction/injection. The significant effect of the internal heat generation is also taken into account. The boundary layer approximation equations responsible for the flow characteristics are formulated and translated to ordinary differential equations (ODEs) with the help of the similarity variable. The shooting technique is then employed to reduce the second-order ODEs to an initial value problem which is solved numerically by the Runge-Kutta method in maple software. Some of the results obtained are: that for weak mixed convection, the velocity and fluid temperature decay exponentially with suction whereas appreciating with fluid injection. The radiative heat flux boosts the fluid temperature and in turn propagates the fluid flow. The internal heat generation ([Formula: see text]) serves as a barrier for the heat flow from the left plate surface to the right plate surface except the mixed convection is resiliently sufficient to counter the generated heat and heat conducted via the plate from its left surface. However, for a weak [Formula: see text], the heat transfer from the left to right plate surface is feasible even with weak mixed convection. For [Formula: see text], the wall temperature is less than 1 and the heat transfer flows from the wall into the free stream. However, for [Formula: see text], the heat transfer flow back into the wall. With weak convection and buoyancy effect, the heat transfer could be increased by increasing the internal heat generation but the contrary is true for nonlinear thermal radiation.

Pathway toward Optical Cycling and Laser Cooling of Functionalized Arenes.

Rapid and repeated photon cycling has enabled precision metrology and the development of quantum information systems using atoms and simple molecules. Extending optical cycling to structurally complex molecules would provide new capabilities in these areas, as well as in ultracold chemistry. Increased molecular complexity, however, makes realizing closed optical transitions more difficult. Building on already established strong optical cycling of diatomic, linear triatomic, and symmetric top molecules, recent work has pointed the way to cycling of larger molecules, including phenoxides. The paradigm for these systems is an optical cycling center bonded to a molecular ligand. Theory has suggested that cycling may be extended to even larger ligands, like naphthalene, pyrene, and coronene. Herein, we study optical excitation and fluorescent vibrational branching of CaO-[Formula: see text], SrO-[Formula: see text], and CaO-[Formula: see text] and find only weak decay to excited vibrational states, indicating a promising path to full quantum control and laser cooling of large arene-based molecules.

Weak-decay searches for Qs{bar{u}}{bar{d}} tetraquarks

We propose to search for the open heavy-flavor exotic states with the quark components of Qs{bar{u}}{bar{d}} with Q=b,c via their weak decays. If there exist such exotic states below the BK or DK thresholds, they can only decay weakly. The advantages include: (i) the experimental backgrounds from the secondary decay vertex are much lower due to the long lifetimes, (ii) the productions are large enough for only one heavy quark in such states, (iii) the thresholds of BK or DK are about 260 MeV higher compared to the B_spi or D_spi thresholds of the configurations of Qu{bar{s}}{bar{d}} or Qd{bar{s}}{bar{u}}, with a higher possibility to exist such weakly-decay particles, and (iv) if observed, their inner structures are easier understood since they can not be induced by the kinematic effects.

Probing the Neutrino-Mass Scale with the KATRIN Experiment

The absolute mass scale of neutrinos is an intriguing open question in contemporary physics. The as-yet-unknown mass of the lightest and, at the same time, most abundant massive elementary particle species bears fundamental relevance to theoretical particle physics, astrophysics, and cosmology. The most model-independent experimental approach consists of precision measurements of the kinematics of weak decays, notably tritium β decay. With the KATRIN experiment, this direct neutrino-mass measurement has entered the sub-eV domain, recently pushing the upper limit on the electron-based neutrino mass down to 0.8 eV (90% CL) on the basis of first-year data out of ongoing, multiyear operations. Here, we review the experimental apparatus of KATRIN, the progress of data taking, and initial results. While KATRIN is heading toward the target sensitivity of 0.2 eV, other scientific goals are pursued. We discuss the search for light sterile neutrinos and an outlook on future keV-scale sterile-neutrino searches as well as further physics opportunities beyond the Standard Model.

Theoretical Estimate of the Half-life for the Radioactive 134Cs and 135Cs in Astrophysical Scenarios

We analyze the CsBa and Cs Ba β − decays, which are crucial production channels for Ba isotopes in asymptotic giant branch (AGB) stars. We calculate, starting from relativistic quantum mechanics, the effects of multichannel scattering onto weak decays, including nuclear and electronic excited states (ESs) populated above ≃10 keV, for both parent and daughter nuclei. We find increases in the half-lives for T > 108 K (by more than a factor of 3 for 134Cs) as compared to previous works based on systematics. We also discuss our method in view of these previous calculations. An important impact on half-lives comes from nuclear ES decays, while including electronic temperatures yields further increases of about 20% at energies of 10–30 keV, typical of AGB stars of moderate mass (M ≲ 8 M ⊙). Despite properly considering these effects, the new rates remain sensitively lower than the Takahashi & Yokoi values, implying longer half-lives at least above 8–9 keV. Our rate predictions are in substantial accord with recent results based on the shell model, and strongly modify branching ratios along the s-process path previously adopted. With our new rate, nucleosynthesis models well account for the isotopic admixtures of Ba in presolar SiC grains and in the Sun.

Study of CP violation in hyperon decays at super-charm-tau factories with a polarized electron beam

Nonleptonic two-body weak decays of baryons are an important tool to probe the combined charge conjugation--parity symmetry ($CP$) violation. We explain why the decays of strange baryons provide complementary information to the decays of kaons. A model-independent parametrization of the nonleptonic decays of the $\mathrm{\ensuremath{\Lambda}}$ and $\mathrm{\ensuremath{\Xi}}$ baryons is reviewed, and the amplitudes are updated according to the latest experimental input. We demonstrate the potential of performing precision tests in strange baryon decays at the next-generation electron-positron $J/\ensuremath{\psi}$ factories with luminosity of ${10}^{35}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$. The copious production of spin-entangled hyperon-antihyperon pairs via the $J/\ensuremath{\psi}$ resonance allows for a direct comparison of the baryon and antibaryon decay properties. Using analytic approximations and numerical calculations, we study the quantitative impact of spin correlations and polarization in such $CP$ tests. We show that by using a longitudinally polarized electron beam the statistical precision of the $CP$ tests can be significantly improved compared to the experiments without polarized beams. Furthermore, we map out further directions for possible improvements, like analysis of incompletely reconstructed events or a combination of the isospin related processes. Altogether, these methods are promising for the observation of a statistically significant $CP$-violation signal with a strength corresponding to the standard model predictions. Our conclusions should encourage more detailed feasibility studies, including optimization of the measurement methods and studies of systematic effects. Finally, our results call for an update of the theory predictions with increased precision.

Constraints on heavy neutral leptons interacting with a singlet scalar

Heavy neutral leptons (HNLs) are an attractive minimal extension of the Standard Model, as is a singlet scalar $s$ mixing with the Higgs boson. If both are present, it is natural for HNLs to interact with $s$. For a light singlet,the decay $N\to s\nu$ can dominate over weak HNL decays. We reinterpret existing constraints on HNL mixing from the DELPHI, CHARM and Belle experiments for 0.5-100 GeV mass HNLs, taking into account the new decay channel. Although the constraints are typically weakened, in some cases they can become stronger, due to observable $s\to\ell^+\ell^-$ decays in the detectors. The method presented here could be used to recast constraints from other (older) experiments without resorting to computationally expensive Monte Carlo simulations. In addition, we update and correct some errors in the analysis of the original constraints, in the absence of the singlet.

Status of J-PARC E73 experiment: first direct Hypertriton lifetime measurement with 3He(K--, π 0 ) 3Λ H reaction

In the last decade, heavy-ion based experiments (HypHI, STAR and ALICEi ) announced surprisingly short lifetime for 3 ΛH mesonic weak decay (MWD), which is difficult to interpret given the fact that 3 ΛH is a very loosely bound system. It will be very interesting to study this issue with a different experimental approach. We propose a direct measurement for 3 ΛH hypernucleus MWD lifetime with ∼10% precision as J-PARC E73 experiment; 4 ΛH hypernucleus lifetime will also be measured as a feasibility test for our experimental approach. In this proceeding, we will introduce the experimental method and the current status of E73 experiment.

Searching and identifying leptoquarks through low-energy polarized scattering processes e−p→e−Λc

We investigate the potential for searching and identifying the leptoquark (LQ) effects in the charm sector through the low-energy polarized scattering processes $\vec{e}^{\,-}p\to e^-\Lambda_c$, $e^-\vec{p}\to e^-\Lambda_c$, and $\vec{e}^{\,-}\vec{p}\to e^-\Lambda_c$. Considering only the longitudinally polarized processes, we show that the different LQ models can be disentangled from each other by measuring the four spin asymmetries, $A_{L}^e$, $A_{L}^p$, $A_{L3}^{ep}$, and $A_{L6}^{ep}$, constructed in terms of the polarized cross sections. Although it is challenging to accomplish the same goal with transversely polarized processes, we find that investing them in future experiments is especially beneficial, since they can directly probe into the imaginary part of the Wilson coefficients in the general low-energy effective Lagrangian. With our properly designed experimental setups, it is also demonstrated that promising event rates can be expected for all these processes and, even in the worst-case scenario -- no LQ signals are observed at all, they can still provide a competitive potential for constraining the new physics, compared with those from the conventional charmed-hadron weak decays and the high-$p_T$ dilepton invariant mass tails at high-energy colliders.

Theoretical study of the process Ds+→π+KS0KS0 and the isovector partner of f0(1710)

We present a theoretical study of ${a}_{0}(1710)$, the isovector partner of ${f}_{0}(1710)$, in the process ${D}_{s}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{K}_{S}^{0}{K}_{S}^{0}$. The weak interaction part proceeds through the charm quark decay process: $c(\overline{s})\ensuremath{\rightarrow}(s+\overline{d}+u)(\overline{s})$, while the hadronization part takes place in two mechanisms, differing in how the quarks from the weak decay combine into $\ensuremath{\pi}{K}^{*}$ with a quark-antiquark pair $q\overline{q}$ with the vacuum quantum numbers. In addition to the contribution from the tree diagram of the ${K}^{*+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{K}_{S}^{0}$, we have also considered the ${K}^{*}{\overline{K}}^{*}$ final-state interactions within the chiral unitary approach to generate the intermediate state ${a}_{0}(1710)$, then it decays into the final states ${K}_{S}^{0}{K}_{S}^{0}$. We find that the recent experimental measurements on the ${K}_{S}^{0}{K}_{S}^{0}$ and ${\ensuremath{\pi}}^{+}{K}_{S}^{0}$ invariant mass distributions can be well reproduced, and the proposed mechanism can provide valuable information on the nature of scalar ${f}_{0}(1710)$ and its isovector partner ${a}_{0}(1710)$.

Reconciliation of Theoretical Lifetimes of the 5s5p Metastable State for 88Sr with Measurement: The Role of the Blackbody-Radiation-Induced Decay

We conducted measurement and calculation to resolve the long-standing large discrepancy in the metastable state lifetime for the 88Sr atom between theoretical and experimental results. The present lifetime s, measured using the magneto-optical trap as a photon amplifier to detect the weak decay events, is approximately 60% larger than the previous experimental value s. By considering the electron correlation effects in the framework of the multiconfiguration Dirac–Hartree–Fock theory, we obtained a theoretical lifetime of 1079(54) s, which lies in the range of measurements with error bars. Furthermore, we considered the higher-order electron correlation and Breit interaction to control the uncertainty of the theoretical calculation. The significant improvement in the agreement between calculations and measurements is attributed to the updated blackbody radiation-induced decay rate.

Colossal phonon drag enhanced thermopower in lightly doped diamond

Diamond is one of the most studied materials because of its unique combination of remarkable electrical, mechanical, thermal and optical properties. Using a fully self-consistent ab initio theory of coupled electron-phonon transport, we reveal another striking behavior: a huge drag enhancement of the thermopower of lightly doped diamond. Thermopower values of around 100,000 μV K−1 are found at 100 K, significantly exceeding the highest previously measured value in the correlated metal FeSb2, and occurring at much higher temperatures. The enormous thermopower in diamond arises primarily from exceptionally weak anharmonic phonon decay around and below 100 K that facilitates efficient momentum exchange between charge carriers and phonons through electron-phonon interactions. Exceedingly large thermoelectric power factors are also identified. This work gives insights into the physics of the coupled electron-phonon system in solids and advances our understanding of thermoelectric transport in the regime of strong drag.