Decay Widths Research Articles

Form factors in HQEFT and model independent analysis of relevant semileptonic decays with NP effects* *Supported in part by the National Natural Science Foundation of China (12147214)

The form factors of decays into P-wave excited charmed mesons (including , , , and their strange counterparts, denoted generically as ) are systematically calculated via QCD sum rules in the framework of heavy quark effective field theory (HQEFT). We consider contributions up to the next leading order of heavy quark expansion and give all the relevant form factors, including the scalar and tensor ones only relevant for possible new physics effects. The expressions for the form factors in terms of several universal wave functions are derived via heavy quark expansion. These universal functions can be evaluated through QCD sum rules. Then, the numerical results of the form factors are presented. With the form factors given here, a model independent analysis of relevant semileptonic decays is performed, including the contributions from possible new physics effects. Our predictions for the differential decay widths, branching fractions, and ratios of branching fractions may be tested in more precise experiments in the future.

Momentum dependence of mixing in the pion vector form factor and its effect on * *Supported in part by the Fundamental Research Funds for the Central Universities (FRF-BR-19-001A), and the National Natural Science Foundation of China (11975028, 11974043)

The inclusion of the mixing effect is essential for a precise description of the pion electromagnetic form factor in the process, which quantifies the two-pion contribution to the anomalous magnetic moment of muon . In this study, we analyze the momentum dependence of mixing by considering loop contributions at the next-to-leading order in expansion within the framework of resonance chiral theory. We revisit a previous study [Y. H. Chen, D. L. Yao, and H. Q. Zheng, Commun. Theor. Phys. 69, 1 (2018)] and consider the contribution arising from the kaon mass splitting in the kaon loops and latest experimental data. We perform two types of fits (with momentum-independent or momentum-dependent mixing amplitude) to describe and data within the energy region of 600900 MeV and decay width of . Furthermore, we compare their results. Our findings indicate that the momentum-independent and momentum-dependent mixing schemes provide appropriate descriptions of the data. However, the momentum-dependent scheme exhibits greater self-consistency, considering the reasonable imaginary part of the mixing matrix element obtained. Regarding the contribution to the anomalous magnetic moment of the muon, , the results obtained from the fits considering the momentum-dependent mixing amplitude are in good agreement with those obtained without incorporating the momentum dependence of mixing, within the margin of errors. Furthermore, based on the fitted values of the relevant parameters, we observe that the decay width of is predominantly influenced by the mixing effect.

The strong decay of higher vector Upsilon(11020) state in the framework of non-relativistic quark model

An analytical study of a source of Beauty mesons (B mesons) by the Strong decay of Upsilon(11020) is performed to obtain various modes of B mesons. The non-relativistic quark model framework is used to predict the masses of the bottomonium mesons. The strong decay of the Upsilon(11020) state is calculated utilizing Quark Pair Creation model. In addition, the branching ratio of the strong decay has been calculated for each decay width and using them to estimate the number of B-meson pairs for each strong decay width. The results show reasonable agreement with recent Particle Data Group data, in particular with the total strong decay width of Upsilon(11020). The Upsilon(11020) particle is expected to be a good candidate for the conventional Upsilon(6S) state and provides both types of strange and non-strange B mesons. We found new conclusions for the strong decay widths of the Upsilon(11020) in the relativistic phase space. The strong width of the B^{*}B^{*} channel is predicted to be the highest width by the ratio (cong 51%) concerning higher vector Upsilon(11020) State. In addition, the specific B_{s}B_{s}^{*} channel is expected to be the highest width relative to higher Upsilon resonances.

Study of singly heavy baryon lifetimes

We study the inclusive decay widths of singly heavy baryons with the improved bag model in which the unwanted center-of-mass motion is removed. Additional insight is gained by comparing the charmed and bottom baryons. We discuss the running of the baryon matrix elements and compare the results with the non-relativistic quark model (NRQM). While the calculated two-quark operator elements are compatible with the literature, those of the four-quark ones deviate largely. In particular, the heavy quark limit holds reasonably well in the bag model for four-quark operator matrix elements but is badly broken in the NRQM. We predict 1 − τ (Ωb)/τ( {Lambda}_b^0 ) = (8.34 ± 2.22)% in accordance with the current experimental value of left({11.5}_{-11.6}^{+12.2}right)% and compatible with (13.2 ± 4.7)% obtained in the NRQM. We find an excellent agreement between theory and experiment for the lifetimes of bottom baryons. We confirm that {Omega}_c^0 could live longer than {Lambda}_c^{+} after the dimension-7 four-quark operators are taken into account. We recommend to measure some semileptonic inclusive branching fractions in the forthcoming experiments to discern different approaches. For example, we obtain mathcal{BF}left({Xi}_c^{+}to X{e}^{+}{nu}_eright) = (8.57±0.49)% and mathcal{BF}left({Omega}_c^0to X{e}^{+}{nu}_eright) = (1.88 ± 1.69)% in sharp contrast to mathcal{BF}left({Xi}_c^{+}to X{e}^{+}{nu}_eright) = left({12.74}_{-2.45}^{+2.54}right)% and mathcal{BF}left({Omega}_c^0to X{e}^{+}{nu}_eright) = left({7.59}_{-2.24}^{+2.49}right)% found in the NRQM.

Investigating full-heavy tetraquarks composed of cc{bar{c}}{bar{b}} and bb{bar{b}}{bar{c}}

The full-heavy tetraquarks cc{bar{c}}{bar{b}} and bb{bar{b}}{bar{c}} are systematically investigated within a quark model. The meson–meson structure, diquark–antidiquark structure and K-structure are considered in this work. There is no bound state for cc{bar{c}}{bar{b}} and bb{bar{b}}{bar{c}} systems in IJ^{P}=00^{+},01^{+} and 02^{+} channels. However, for cc{bar{c}}{bar{b}} system, three possible resonance states with energy of 10{,}079~textrm{MeV} , 10{,}081~textrm{MeV} and 10{,}177~textrm{MeV} are found in IJ^{P}=00^{+},01^{+} and 02^{+}, respectively, and their decay width Gamma are 6.7–8.4 MeV, 1.4–7.2 MeV and 9.1–11.1 MeV. For bb{bar{b}}{bar{c}} system, there also exist three possible resonance states with energy of 16{,}474~textrm{MeV} , 16{,}474~textrm{MeV} and 16{,}541~textrm{MeV} in IJ^{P}=00^{+},01^{+} and 02^{+}, respectively, and the decay widths Gamma of them are 2.2–6.1 MeV, 2.2–6.9 MeV and 5.3–8.5 MeV. bc{bar{c}}{bar{c}} and cb{bar{b}}{bar{b}} systems will have the same results as cc{bar{c}}{bar{b}} and bb{bar{b}}{bar{c}}, respectively. These full-heavy resonance states are worthy to be searched in the future experiments.

Leptonic Decay Widths for the Composite System of Two Relativistic Fermions

The new relativistic semiclassical leptonic decay widths of vector mesons as the relativistic systems of two quarks with arbitrary masses interacting by means of the funnel-type potentials with Coulomb interaction are obtained. The behavior of the relativistic leptonic decay widths of vector mesons is investigated. Comparison of the behavior for new expression with its relativistic spinless analog is given. Consideration is conducted within the framework of completely covariant quasipotential approach in the Hamiltonian formulation of quantum field theory via a transition to the relativistic configurational representation in the case of two relativistic spin particles of arbitrary masses.

Placing of the recently observed bottom strange states BsJ(6063) and BsJ(6114) in bottom spectra

Abstract We employ the heavy quark effective theory (HQET) to give spin-parity quantum numbers for the bottom strange states BsJ(6063) and BsJ(6114) recently observed by the LHCb Collaboration [9]. By exploring flavor-independent parameters $\Delta _{F}^{(c)} =\Delta _{F}^{(b)}$ and $\lambda _{F}^{(c)} = \lambda _{F}^{(b)}$ appearing in the HQET Lagrangian, we calculate the masses of the experimentally missing bottom strange meson states 2S, 1P, 1D. The parameter ΔF appears in the HQET Lagrangian and gives the spin-averaged mass splitting between excited-state doublets (F) and ground-state doublets (H). Another parameter λF comes from first-order corrections in the HQET Lagrangian and gives hyperfine splittings. We also analyze these bottom strange masses by taking 1/mQ corrections, which lead to modifications of parameter terms of $\Delta _{F}^{(b)} =\Delta _{F}^{(c)} + \delta \Delta _F$ and $\lambda _{F}^{(b)} = \lambda _{F}^{(c)}\delta \lambda _F$. Further, we analyze their two-body decays, couplings, and branching ratios via the emission of light pseudoscalar mesons. Based on the predicted masses and decay widths, we tentatively identify the states BsJ(6063) as 23S1 and BsJ(6114) as 13D1. Our predictions provide crucial information for future experimental studies.

Strong decays of {P}_{psi}^N{(4312)}^{+} to J/ψ(ηc)p and {overline{D}}^{left(ast right)}{Lambda}_c within the Bethe-Salpeter framework

Based on the effective Lagrangian in the heavy quark limit, we calculate the one-boson-exchange interaction kernel of {P}_{psi}^N{(4312)}^{+} as the overline{D}{Sigma}_c molecular state in isospin- frac{1}{2} . We present the Bethe-Salpeter equation and wave function for the constituent particles to be a (pseudo)scalar meson and a frac{1}{2} baryon. By solving the Bethe-Salpeter equation, we obtain {P}_{psi}^N{(4312)}^{+} as the overline{D}{Sigma}_c molecular state with JP = {left(frac{1}{2}right)}^{-} . Combining the effective Lagrangian and the obtained BS wave function, the partial decay widths of {P}_{psi}^N{(4312)}^{+} to J/ψp, ηcp, {overline{D}}^{ast 0}{Lambda}_c^{+} and {overline{D}}^0{Lambda}_c^{+} are calculated to be 0.17, 0.085, 8.8, and 0.026 MeV, respectively, which are roughly consistent with the LHCb experimental measurements and some other theoretical researches. The obtain results indicate the fraction of {overline{D}}^{ast 0}{Lambda}_c^{+} channel amounts to ~ 90% of {P}_{psi}^N{(4312)}^{+} , and is a highly promising channel to be discovered in the near future experiments. Our results favor the interpretation of {P}_{psi}^N{(4312)}^{+} as the overline{D}{Sigma}_c molecular state with JP = {left(frac{1}{2}right)}^{-} and isospin I = frac{1}{2} .

Suppression of Higgs mixing by “quantum Zeno effect”

The Higgs portal interaction to a singlet sector of the standard model (SM) gauge group is widely-studied. In this paper, we show that a quantum effect is important if the Higgs field mixes with another singlet scalar field whose decay rate is larger than the mass difference between the two mass eigenstates. This effect may be interpreted as the “quantum Zeno effect” by defining the (would-be) decay process of the singlet scalar as the measurement. In either the quantum mechanics or the quantum field theory, we show that the resulting propagating mode is not the eigenstate of the mass matrix, but it is approximately the eigenstate of the interaction. As a consequence, the decoupling of the mixing effect happens at the infinity limit of the decay width of the exotic scalar even if the naïve mixing parameter is not small. With a finite decay width of the exotic scalar, we derive the effective mass of the propagating mode in the SM sector, its decay rate, and the couplings at the 1-loop level. It turns out that the mixed mass eigenstates can mimic the discovered 125 GeV Higgs boson. This fuzzy Higgs boson can be obtained in a simple perturbative renormalizable model when the mass difference is smaller than O(0.1)GeV (O(1) GeV, O(10)GeV) for O(1) (O(0.01), O(0.001)) mixing to be consistent with the 125 GeV SM Higgs boson. We argue the possible natural scenario for the tiny mass splitting and the possibility that the upper bound of the mass difference is larger for a strongly-coupled singlet sector. To probe the fuzzy Higgs boson scenario, it is difficult to directly produce the singlet sector particles. Nevertheless, the future Higgs factories may probe this scenario by precisely measuring the Higgs boson invisible decay rate and the deviation of the Higgs coupling. Applications of the mechanism are also mentioned.

Light-cone sum rules for S-wave B → Kπ form factors

We derive a set of light-cone sum rules relating the S-wave B → Kπ hadronic form factors to the B-meson light-cone distribution amplitudes (LCDAs), taking into account the complete set of LCDAs up to and including twist four. These results complement the sum rules for the P-wave B → Kπ form factors obtained earlier. We then use the new sum rules to estimate the S-wave contributions to B → Kπℓℓ decays as a function of the Kπ invariant mass. We pay particular attention to the fact that the S-wave Kπ spectrum cannot be modelled by a sum of Breit-Wigner resonances, and employ a more consistent dispersive coupled-channel approach. We compare our predictions for branching ratios and angular observables with LHCb measurements in two different kinematic regions, around K∗(892) and {K}_0^{ast }(1430) . We observe an overall compatibility and discuss possible improvements of our model to obtain a better description of the B → Kπ form factors over a large kinematic range.

From inflation to reheating and their dynamical stability analysis in Gauss–Bonnet gravity

We investigate the inflation and reheating phenomenology in scalar-Einstein-Gauss–Bonnet theory of gravity where a scalar field non-minimally couples with the Gauss-Bonnet (GB) curvature term. Regarding the inflationary phenomenology, we find – (1) the inflation starts with a quasi de-Sitter phase and has an exit at a finite e-fold, which is indeed consistent with the resolution of horizon and flatness problems, (2) the scalar and tensor perturbations prove to be ghost free and do not suffer from gradient instability, (3) the curvature perturbation amplitude as well as its tilt and the tensor-to-scalar ratio turn out to be simultaneously compatible with the recent Planck data for suitable values of the parameters which also results to the inflationary energy scale ∼1012GeV. After the inflation ends, the scalar field starts to decay to radiation with a constant decay width. For our considered scalar potential and the GB coupling function, the model results to an analytic power law solution of the Hubble parameter and a logarithmic solution of the scalar field during the reheating era, where the exponent of the Hubble parameter determines the effective EoS parameter (weff) during the same. The stability of such reheating dynamics is examined by dynamical analysis which ensures that weff can go beyond unity and reach up-to the maximum value of max(weff)=1.56. The scenario with weff>1 proves to be purely due to the presence of the GB coupling function, which in turn may have important consequences on enhancing the primordial gravitational waves’ amplitude observed today. The inflationary e-fold number (Nf) gets further constrained by the input of the reheating stage, and we critically examine the constraint of Nf coming from both the inflation and reheating phenomenology. We finally construct the complete forms of scalar potential (V(ϕ)) and the GB coupling function (ξ(ϕ)) that smoothly transits from inflation to reheating, and numerically solve the Hubble parameter and the scalar field for such complete forms of V(ϕ) and ξ(ϕ). Such numerical solutions match with analytic ones in the respective regime. After the reheating ends, the GB term gets decouple from the theory and the radiation energy density dominates the energy budget of the universe, which in turn produces the standard radiation era of the universe.

Loop enhancement of direct detection cross section in a fermionic dark matter model

We investigate the effect of one loop quantum corrections on the elastic scattering of dark matter off the nucleon in a fermionic dark matter model. The model introduces two new singlet fermions and a singlet scalar. The fermions communicate with the SM particles through a Higgs portal. It is found that some viable regions in the parameter space respecting the bounds from the observed relic density, the Higgs invisible decay width, and direct detection experiment, will be shrunk significantly when one loop effects are taken into account. The regions already resided below the neutrino floor, partly may come into regions which are testable by the current or future direct detection experiments. In addition, some regions being viable at tree level, may be excluded when quantum corrections are included.

Three-dimensional approach applied to quasistationary states of deformed α emitters

We apply a three-dimensional (3D) approach to investigate the quasistationary states of well-deformed $\ensuremath{\alpha}$ emitters. With a splitting of the anisotropic 3D potential into internal and external parts at a separation surface, the 3D $\ensuremath{\alpha}$-cluster decay width is determined by the initial wave function of a true bound state of an anisotropic harmonic oscillator potential and a nonresonance scattering wave function of Coulomb potential. Substantial difference between the one-dimensional (1D) and 3D decay width is found for typical $\ensuremath{\alpha}$ emitters with large quadrupole and hexadecapole deformations.

Radiative decays of the spin-2 partner of X(3872)

It has been generally expected that the X(3872) has a spin-2 partner, X2, with quantum numbers JPC=2++. In the hadronic molecular model, its mass was predicted to be below the D⁎D¯⁎ threshold, and the new structure reported in the γψ(2S) invariant mass distribution by the Belle Collaboration with mass M=(4014.3±4.0±1.5) MeV and decay width Γ=(4±11±6) MeV, with a global significance of 2.8 σ, is a nice candidate for it. We consider the radiative decay widths for the X2→γψ with ψ=J/ψ,ψ(2S) treating the X2 as a D⁎D¯⁎ shallow bound state, and estimate the events of X2 in two-photon collisions that can be collected in the γJ/ψ→γℓ+ℓ− (ℓ=e,μ) final states at Belle. Based on the upper limit for the ratio of decay widths of X(3872)→γψ(2S) and X(3872)→γJ/ψ measured by BESIII, we predict the similar ratio Γ(X2→γψ(2S))/Γ(X2→γJ/ψ) to be smaller than 1.0. We suggest searching for the X2 signal in the γJ/ψ invariant mass distribution via two-photon fusions. The results will lead to insights into both the X(3872) and the new structure observed by Belle.

Study of I=0 bottomonium bound states and resonances in S , P , D , and F waves with lattice QCD static-static-light-light potentials

In this paper we study $I = 0$ bottomonium in $S$, $P$, $D$ and $F$ waves considering five coupled channels, one confined quarkonium and four open $B^{(*)} \bar B^{(*)}$ and $B_s^{(*)} \bar B_s^{(*)}$ meson-meson channels. To this end we use and extend a recently developed novel approach utilizing lattice QCD string breaking potentials for the study of quarkonium bound states and resonances. This approach is based on the Born Oppenheimer approximation and the unitary emergent wave method and allows to compute the poles of the $\mbox{T}$ matrix. We compare our results to existing experimental results for $I = 0$ bottomonium and discuss masses, decay widths and the assignment of angular momentum quantum numbers. Moreover, we determine the quarkonium and meson-meson composition of these states to clarify, which of them are ordinary quarkonium, and which of them should rather be interpreted as tetraquarks.

Role of triangle singularity in the decay process D0→π+π−f0(980) , f0→π+π−

We study the process $D^0 \to \pi^+ \pi^- f_0(980),\ f_0 \to \pi^+ \pi^-$ by introducing the triangle mechanism, in which $f_0(980)$ is considered to be dynamically generated from the meson-meson interaction. For the total contribution of this process, the contribution of the triangular loop formed by $K^{*} \bar{K} K$ particles could generate a triangular singularity of about 1418 MeV. We calculate the differential decay width of this process and show a narrow peak of about 980 MeV in the $\pi^+ \pi^-$ invariant mass distribution, which comes from $f_0$ decay. For the $M_{inv}(\pi f_0)$ invariant mass distribution, we obtain a finite peak at 1418 MeV, which is consistent with the triangle singularity.

Mass spectroscopy and decay properties of Ξcb, Ξbb baryons

Using the Hypercentral Constituent Quark Model (hCQM), the mass spectra of doubly heavy baryons [Formula: see text] and [Formula: see text] are determined. The model describes an interaction inside the baryonic system. Screened potential has been considered as confining potential with color-Coulomb potential to enumerate the masses of baryonic states. Regge trajectories have been plotted in [Formula: see text] plane. The properties like magnetic moment and radiative decay width have been determined using the obtained results.

Three-loop matching coefficients for heavy flavor-changing currents and the phenomenological applications

Within the framework of non-relativistic QCD (NRQCD) factorization, we compute the matching coefficients between full Quantum Chromodynamics (QCD) and NRQCD for the heavy flavor-changing vector, axial-vector, scalar and pseudo-scalar currents up to next-to-next-to-next-to-leading order (N3LO). We accomplish the analytical expressions for the three-loop renormalization constants and the corresponding anomalous dimensions for all of the four NRQCD currents with two different heavy flavors. The three-loop QCD corrections to the matching coefficients turn out to be significantly larger than lower order corrections. By employing the scale relation, we approximately simulate the N3LO correction to the wave functions at the origin for the vector {B}_c^{ast } meson and the pseudo-scalar Bc meson from the known result for the equal-mass heavy quarkonium in potential NRQCD (pNRQCD). We find large cancellations at the third order between the matching coefficients and the wave functions at the origin, and obtain the convergent decay constants of {B}_c^{ast } and Bc up to N3LO. We present the complete perturbative QCD predictions for the decay constants, leptonic decay widths, and branching ratios of the beauty-charmed mesons.

Radiative production and decays of the exotic [formula omitted] and its siblings

We study the production of the light JPC=1−+ hybrid isoscalars η1′(1855) and the yet undiscovered η1(1660) as intermediate states in the radiative decays of the charmonium (J/ψ) to two conventional mesons using a flavor symmetric Lagrangian. For this purpose, we use the J/ψ→γη1′(1855)→γηη′ process as the reference. We find that some of the decay channels have branching ratios similar to or larger than that of the γηη′ channel and are sensitive to the mixing between the hybrid isoscalars. We propose that relatively stable γηf1(1285) channel be explored for the presence of the light hybrid isoscalar η1hyb(1660). We also exploit the strong decay channels containing at least one vector meson to study the radiative decays of the whole hybrid nonet {π1(1600),K1hyb(1750),η1hyb(1660),η1′(1855)}. We find that the hybrids cannot radiatively decay into the I=0 pseudoscalars. Furthermore, the vector decay channels ((ρ/ω/ϕ)γ) of the hybrid isoscalars are sensitive to the strangeness content of the hybrids. We also provide estimates for the branching fractions for the radiative production and partial widths for the radiative decays of the hybrids.

Impact of high-scale Seesaw and Leptogenesis on inflationary tensor perturbations as detectable gravitational waves

We discuss the damping of inflationary gravitational waves (GW) that re-enter the horizon before or during an epoch, where the energy budget of the universe is dominated by an unstable right handed neutrino (RHN), whose out of equilibrium decay releases entropy. Starting from the minimal Standard Model extension, motivated by the observed neutrino mass scale, with nothing more than 3 RHN for the Seesaw mechanism, we discuss the conditions for high scale leptogenesis assuming a thermal initial population of RHN. We further address the associated production of potentially light non-thermal dark matter and a potential component of dark radiation from the same RHN decay. One of our main findings is that the frequency, above which the damping of the tensor modes is potentially observable, is completely determined by successful leptogenesis and a Davidson-Ibarra type bound to be at around 0.1 Hz. To quantify the detection prospects of this GW background for various proposed interferometers such as AEDGE, BBO, DECIGO, Einstein Telescope or LISA we compute the signal-to-noise ratio (SNR). This allows us to investigate the viable parameter space of our model, spanned by the mass of the decaying RHN {M}_1gtrsim 2.4times {10}^8textrm{GeV}cdot sqrt{2times {10}^{-7}textrm{eV}/{tilde{m}}_1} (for leptogenesis) and the effective neutrino mass parameterizing its decay width {tilde{m}}_1 < 2.9 × 10−7 eV (for RHN matter domination). Thus gravitational wave astronomy is a novel way to probe both the Seesaw and the leptogenesis scale, which are completely inaccessible to laboratory experiments in high scale scenarios.