Decay Widths Research Articles

Shedding light on charmonium

We investigate E1 radiative transitions within charmonium in a relativistic approach based on light-front QCD. In quantum field theory, two sets of processes are pure E1: χc0→J/ψγ (ψ→χc0γ) and hc→ηcγ (ηc′→hcγ), both involving the P-wave charmonia. We compute the E1 radiative decay widths as well as the corresponding transition form factors of various processes including those involving 2P states. These observables provide an access to the microscopic structures of the P-wave charmonium. We show that our parameter-free predictions are in excellent agreement with the experimental measurements as well as lattice simulations whenever available. Published by the American Physical Society 2024

Observation of D_{s}^{+}→η^{'}μ^{+}ν_{μ}, Precision Test of Lepton Flavor Universality with D_{s}^{+}→η^{(')}l^{+}ν_{l}, and First Measurements of D_{s}^{+}→η^{(')}μ^{+}ν_{μ} Decay Dynamics.

By analyzing 7.33 fb^{-1} of e^{+}e^{-} annihilation data collected at center-of-mass energies between 4.128 and 4.226GeV with the BESIII detector, we report the observation of the semileptonic decay D_{s}^{+}→η^{'}μ^{+}ν_{μ}, with a statistical significance larger than 10σ, and the measurements of the D_{s}^{+}→ημ^{+}ν_{μ} and D_{s}^{+}→η^{'}μ^{+}ν_{μ} decay dynamics for the first time. The branching fractions of D_{s}^{+}→ημ^{+}ν_{μ} and D_{s}^{+}→η^{'}μ^{+}ν_{μ} are determined to be (2.235±0.051_{stat}±0.052_{syst})% and (0.801±0.055_{stat}±0.028_{syst})%, respectively, with precision improved by factors of 6.0 and 6.6 compared to the previous best measurements. Combined with the results for the decays D_{s}^{+}→ηe^{+}ν_{e} and D_{s}^{+}→η^{'}e^{+}ν_{e}, the ratios of the decay widths are examined both inclusively and in several ℓ^{+}ν_{ℓ} four-momentum transfer ranges. No evidence for lepton flavor universality violation is found within the current statistics. The products of the hadronic form factors f_{+,0}^{η^{(')}}(0) and the c→s Cabibbo-Kobayashi-Maskawa matrix element |V_{cs}| are determined. The results based on the two-parameter series expansion are f_{+,0}^{η}(0)|V_{cs}|=0.452±0.010_{stat}±0.007_{syst} and f_{+,0}^{η^{'}}(0)|V_{cs}|=0.504±0.037_{stat}±0.012_{syst}, which help to constrain present models on f_{+,0}^{η^{(')}}(0). The forward-backward asymmetries are determined to be ⟨A_{FB}^{η}⟩=-0.059±0.031_{stat}±0.005_{syst} and ⟨A_{FB}^{η^{'}}⟩=-0.064±0.079_{stat}±0.006_{syst} for the first time, which are consistent with the theoretical calculation.

Noncommutative field theory of the Tkachenko mode: Symmetries and decay rate

We construct an effective field theory describing the collective Tkachenko oscillation mode of a vortex lattice in a two-dimensional rotating Bose-Einstein condensate in the long-wavelength regime. The theory has the form of a noncommutative field theory of a Nambu-Goldstone boson, which exhibits a noncommutative version of dipole symmetry. From the effective field theory, we show that, at zero temperature, the decay width Γ of the Tkachenko mode scales with its energy E as Γ∼E3 in the low-energy limit. We also discuss the width of the Tkachenko mode at a small temperature. Published by the American Physical Society 2024

Laser-assisted two-proton radioactivity

In this work, we systematically investigate the two-proton (2p) radioactivity assisted by an ultra-intense laser field within a deformed one-parameter model (OPM). The results show that the ultra-intense laser hardly affects the preformation probability of the emitted 2p-pair, but it can change the 2p radioactive half-lives to a finite extent by affecting the penetrability probability. Moreover, we compare the responses of different 2p radioactivity nuclei to the laser field, and it is found that the 2p radioactivity of nuclei with a low decay width are more easily influenced by the intense laser field. Furthermore, the effects of different physical parameters of a laser pulse on the 2p radioactivity were also discussed. The calculations indicate that the lasers characterized by shorter wavelengths and higher intensities exert a more significant influence on the rate of the average change in pulse duration. Finally, we extended the deformed OPM to predict the half-lives of 2p radioactivity candidates and identified the possible experimental objects of the laser-assisted 2p radioactivity. This study may promote the possibility of future experimental investigations on extensive facilities like GSI and ELI-NP, etc.

Mass, Spectroscopy, and Two-Neutron Decay of ^{16}Be.

The structure and decay of the most neutron-rich beryllium isotope, ^{16}Be, has been investigated following proton knockout from a high-energy ^{17}B beam. Two relatively narrow resonances were observed for the first time, with energies of 0.84(3) and 2.15(5)MeV above the two-neutron decay threshold and widths of 0.32(8) and 0.95(15)MeV, respectively. These were assigned to be the ground (J^{π}=0^{+}) and first excited (2^{+}) state, with E_{x}=1.31(6) MeV. The mass excess of ^{16}Be was thus deduced to be 56.93(13)MeV, some 0.5MeV more bound than the only previous measurement. Both states were observed to decay by direct two-neutron emission. Calculations incorporating the evolution of the wave function during the decay as a genuine three-body process reproduced the principal characteristics of the neutron-neutron energy spectra for both levels, indicating that the ground state exhibits a strong spatially compact dineutron component, while the 2^{+} level presents a far more diffuse neutron-neutron distribution.

Pc states in the mixture of molecular and pentaquark pictures

We systematically study hidden charm pentaquark states in the constituent quark model with a general Hamiltonian for multiquark systems, considering the coupling between the Σc(*)D¯(*) molecular states and the q3cc¯ compact pentaquark states by the one-gluon exchange hyperfine interaction. The ground state hidden-charm pentaquark mass spectra and the strong decay widths are calculated. This work suggests that Pc(4312), Pc(4457), and Pc(4380) resonances might be mainly ΣcD¯, ΣcD¯*, and Σc*D¯ hadronic molecules respectively, and Pc(4440) might include sizable pentaquark components. Published by the American Physical Society 2024

Quarkonia dissociation at finite magnetic field in the presence of momentum anisotropy

In this study, we investigate the potential of heavy quarkonia within a magnetized hot QGP medium having finite momentum anisotropy. The phenomenon of inverse magnetic catalysis is introduced into the system, influencing the magnetic field-modified Debye mass and thereby altering the effective quark masses. Concurrently, the impact of momentum anisotropy in the medium is considered that influence the particle distribution in the medium. The thermal decay width and dissociation temperature of quarkonium states, specifically the 1S and 2S states of charmonium and bottomonium, are computed. Our results reveal that both momentum anisotropy and the inverse magnetic catalysis effects play a significant role in modifying the thermal decay width and dissociation temperature of these heavy quarkonia states.

Constraints on subleading interactions in beta decay Lagrangian

We discuss the effective field theory (EFT) for nuclear beta decay. The general quark-level EFT describing charged-current interactions between quarks and leptons is matched to the nucleon-level non-relativistic EFT at the OMeV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O}\\left(\ extrm{MeV}\\right) $$\\end{document} momentum scale characteristic for beta transitions. The matching takes into account, for the first time, the effect of all possible beyond-the-Standard-Model interactions at the subleading order in the recoil momentum. We calculate the impact of all the Wilson coefficients of the leading and subleading EFT Lagrangian on the differential decay width in allowed beta transitions. As an example application, we show how the existing experimental data constrain the subleading Wilson coefficients corresponding to pseudoscalar, weak magnetism, and induced tensor interactions. The data display a 3.5 sigma evidence for nucleon weak magnetism, in agreement with the theory prediction based on isospin symmetry.

Decay property of the X(3842) as the ψ3(1D33) state

In this paper, the new particle X(3842) discovered by the LHCb Collaboration is identified to be the ψ3(13D3) state. We study its strong decays with the combination of the Bethe-Salpeter method and the P30 model. Its electromagnetic (EM) decay is also calculated by the Bethe-Salpeter method within the Mandelstam formalism. The strong decay widths are Γ[X(3842)→D0D¯0]=1.27 MeV and Γ[X(3823)→D+D−]=1.08 MeV, and the ratio is B[X(3842)→D+D−]/B[X(3823)→D0D¯0]=0.84. The EM decay width is Γ[X(3842)→χc2γ]=0.29 MeV. We also estimate the total width to be 2.87 MeV, which is in good agreement with the experimental data 2.79−0.86+0.86 MeV. Since the used relativistic wave functions include different partial waves, we also study the contributions of different partial waves in electromagnetic decay. Published by the American Physical Society 2024

Heavy neutral lepton corrections to SM boson decays: lepton flavour universality violation in low-scale seesaw realisations

We study lepton flavour universality violation in SM boson decays in low-scale seesaw models of neutrino mass generation, also addressing other electroweak precision observables. We compute the electroweak next-to-leading order corrections, which turn out to be important – notably in the case of the invisible decay width of the Z boson, for which the corrections can be as large as the current experimental uncertainty. As a well-motivated illustrative study case, we choose a realisation of the Inverse Seesaw mechanism, and discuss the complementary role of lepton flavour conserving, lepton flavour violating and precision observables, both in constraining and in probing such models of neutrino mass generation. Our findings suggest that invisible Z decays are especially important, potentially at the origin of the most stringent constraints for certain regimes of the Inverse Seesaw (while complying with charge lepton flavour violation and other electroweak precision tests). We also discuss the probing power of the considered observables in view of the expected improvement in experimental precision at FCC-ee.

Why quarkonium hybrid coupling to two S -wave heavy-light mesons is not suppressed

We examine the couplings of quarkonium hybrids to heavy-light meson pairs in the Born-Oppenheimer approximation for QCD. The lowest hybrid multiplets consist of bound states of the Πu and Σu− potentials. We find that the Σu− potential can couple to pairs of S-wave mesons through string breaking, while the Πu potential cannot. From this observation, we derive model-independent selection rules that contradict previous expectations that quarkonium hybrids are forbidden to decay into pairs of S-wave mesons. These Born-Oppenheimer selection rules are consistent with the partial decay widths of the lowest charmonium hybrid with exotic quantum numbers JPC=1−+ recently calculated using lattice QCD. Published by the American Physical Society 2024

Production of charmonium pentaquarks from b-baryon and B-meson decays: SU(3) analysis* *W. H. H and J. X. is supported in part by the National Natural Science Foundation of China (12105247), the China Postdoctoral Science Foundation (2021M702957). Y.X is supported in part by the National Natural Science Foundation of China (12005294)

Here, we study the production of charmonium pentaquarks from bottom baryon and B-meson decays under the flavor symmetry. Decay amplitudes for various processes are parameterized in terms of irreducible nonperturbative amplitudes. Numerous relations between decay widths are deduced. Moreover, the strong decays of pentaquarks are considered. Our results can be tested in future measurements at LHCb, Belle II, and CEPC. Once decay branching fractions are measured, this study will be useful for the exploration of new decay channels and pentaquark states.

Approximate N5LO Higgs Boson Decay Width Γ(H→γγ)

The precision and predictive power of perturbative QCD (pQCD) prediction depends on both a precise, convergent, fixed-order series and a reliable way of estimating the contributions of unknown higher-order (UHO) terms. It has been shown that by applying the principle of maximum conformality (PMC), which applies the renormalization group equation recursively to set the effective magnitude of αs of the process, the remaining conformal coefficients will be well matched with the corresponding αs at each order, leading to a scheme-and-scale invariant and more convergent perturbative series. The PMC series, being satisfied with the standard renormalization group invariance, has a rigorous foundation. Thus it not only can be widely applied to virtually all high-energy hadronic processes, but also can be a reliable platform for estimating UHO contributions. In this paper, by using the total decay width Γ(H→γγ) which has been calculated up to N4LO QCD corrections, we first derive its PMC series by using the PMC single-scale setting approach and then estimate its unknown N5LO contributions by using a Bayesian analysis. The newly suggested Bayesian-based approach estimates the magnitude of the UHO contributions based on an optimized analysis of the probability density distribution, and the predicted UHO contribution becomes more accurate when more loop terms have been known to tame the probability density function. Using the top-quark pole mass Mt = 172.69 GeV and the Higgs mass MH = 125.25 GeV as inputs, we obtain Γ(H→γγ)=9.56504keV, and the estimated N5LO contribution to the total decay width is ΔΓH=±1.65×10−4keV for the smallest credible interval of 95.5% degree of belief.

χc1(4274) multiplicity in heavy-ion collisions

In a previous work we computed the thermally averaged cross sections for the production and absorption reactions of the χc1(4274) state in the hot hadron gas formed in heavy-ion collisions. In the present work we estimate the final yield of the χc1(4274) state in these collisions. We use the coalescence model to fix the initial multiplicity of the χc1(4274), which is treated as a P-wave bound state of DsD¯s0 and also as a compact tetraquark. The Bjorken picture is used to model the hydrodynamic expansion and cooling. We also consider the Hubble cooling, which is faster and mimics the effect of the transverse expansion. Then, the kinetic equation is solved to evaluate the time evolution of the χc1(4274) yield during the hot hadron gas phase. Since the χc1(4274) decay width is large it might decay inside the hadron gas. Therefore, we also include the χc1(4274) decay and regeneration terms by means of an effective coupling, estimated from the available data. The combined effects of hadronic interactions and the χc1(4274) decay have a strong impact on the final yield. Also, predictions of the χc1(4274) multiplicity as a function of centrality and of the charged hadron multiplicity measured at midrapidity [dNch/dη(η<0.5)] are presented. Finally, we calculate the yield of a proposed P-wave molecular state of DsD¯s0, Y′(4274), characterized by a smaller width and smaller coupling constant obtained from the Weinberg compositeness condition. Published by the American Physical Society 2024

Internal structures of the baryons Ξ(2030) and Ξ(2120)

Currently, there is much controversy surrounding the interpretation of the Ξ(2030) and Ξ(2012) as traditional hadrons containing double strange quarks. In particular, the ratios of the partial decay widths into ΛK¯ and ΣK¯ for Ξ(2030) cannot obtain a suitable explanation under the qss three-quark structure. Thus, we suggest the Ξ(2030) and Ξ(2012) to be VB(=K¯*Σ/ρΞ/K¯*Λ/ϕΞ/ωΞ) molecular states. In this work, we perform a systematical investigation of possible molecular states from the VB(=K¯*Σ/ρΞ/K¯*Λ/ϕΞ/ωΞ) interaction. The interaction of the system considered is described by the t-channel vector (ρ,ω,ϕ,K¯*) and pseudoscalar (π,η(′),K¯) meson exchanges. By solving the nonrelativistic Schrödinger equation with the obtained one-boson-exchange potentials, the VB(=K¯*Σ/ρΞ/K¯*Λ/ϕΞ/ωΞ) bound states with different quantum numbers are searched. The calculation suggests that Ξ(2030) can be assigned as a P-wave K¯*Σ/ρΞ/K¯*Λ/ϕΞ/ωΞ molecular state with spin-parity JP=5/2+. The calculation also predicts the existence of four K¯*Σ/ρΞ/K¯*Λ/ϕΞ/ωΞ bound states with JP=1/2± and JP=3/2±. The Ξ(2012) may be a candidate for one of these four bound states. If Ξ(2012) is an S-wave molecular state with JP=1/2− or JP=3/2−, we suggest determining its spin and parity by studying its decay width, owing to the difference in their molecular components. Published by the American Physical Society 2024

Radiative transition decay width of ψ2(3823)→γχc1 from lattice QCD

We present an exploratory Nf=2 lattice QCD study of ψ2(3823)→γχc1 at a pion mass mπ≈350 MeV. The related two-point and three-point functions are calculated using the distillation method. The electromagnetic multipole form factor V^(0)=2.083(11) for J/ψ→γηc is consistent with previous lattice results. The form factors E^1(0), M^2(0), and E^3(0) for Γ(χc2→γJ/ψ) have the same hierarchy as that derived from experiments, and the predicted decay width Γ(χc2→γJ/ψ)=368(5) keV is in excellent agreement with the Particle Data Group value 374(10) keV and previous lattice QCD results in the quenched approximation. The same strategy is applied to the study of the process ψ2(3823)→γχc1, and the partial decay width is predicted to be 337(27) keV. According to the BESIII constraints on the ψ2(3823) decay channels and some phenomenological results, we estimate the total width Γ(ψ2(3823))=520(100) keV. Published by the American Physical Society 2024

Hidden-bottom hadronic transitions of ϒ(10753)

Assuming that the ϒ(10753) is a 4S−3D mixed state, we investigated the hidden-bottom hadronic decays of the ϒ(10753)→ηb(1S)ω(η(′)) via the intermediate meson loops. In a commonly accepted range of the model parameter α in the form factor, the predicted branching ratios may reach to the order of 10−3–10−2. The relative ratio of the partial decay widths of the ϒ(10753)→ηbη(′) to ϒ(10753)→ηbω is found to be dependent on the η−η′ mixing angle. In addition, we also calculated the ratios of the partial decays widths of the ϒ(10753)→ηbω to ϒ(10753)→ϒ(nS)π+π− (n=1, 2), which are found to be around 0.4 and 0.2 for n=1 and n=2, respectively. These values are in accordance with the preliminary experimental results. The calculations presented here tend to favor the ϒ(10753) as the 4S−3D mixture. We hope these predictions could be verified by the future Belle II experiments. Published by the American Physical Society 2024

Hidden charmonium decays of spin-2 partner of X(3872)

The Belle Collaboration recently reported a promising candidate for the spin-2 D*D¯* partner of the X(3872), called the X2 for short, having a mass of (4014.3±4.0±1.5) MeV and a width of (4±11±6) MeV. Assuming the X2 as a pure molecule of the D*D¯*, we calculated in detail the hidden charmonium decays of the X2→J/ψV and X2→ηcP via the intermediate meson loops, where V=ρ0,ω and P=π0,η,η′. The results indicate that the decay widths are strongly dependent on the X2 mass. At present center value of the mass 4014.3 MeV, the width for the X2→J/ψρ0 is predicted to be a few tens of keV, while it is on the order of 102−3 keV for the X2→J/ψω; the predicted width for the X2→ηcπ0 is about a few keV, while the widths for X2→ηcη and ηcη′ are around a few tens and tenths of keV, respectively. We also investigated the dependence of the ratios between these widths on the X2 mass and on the η−η′ mixing angle, which may be good quantities for experiments. We hope that the present calculations will be checked experimentally in the future. Published by the American Physical Society 2024

Decipher the width of the X(3872) via the QCD sum rules

In this work, we take the X(3872) as the hidden-charm tetraquark state with both isospin I=0 and I=1 components, then investigate the strong decays X(3872)→J/ψπ+π−, J/ψω, χc1π0, D*0D¯0, and D0D¯0π0 with the QCD sum rules. We take account of all the Feynman diagrams, and acquire four QCD sum rules based on rigorous quark-hadron duality. We obtain the total decay width about 1 MeV, which is in excellent agreement with the experiment data ΓX=1.19±0.21 MeV from the PDG, it is the first time to reproduce the tiny width of the X(3872) via the QCD sum rules, which supports assigning the X(3872) as the hidden-charm tetraquark state with the JPC=1++. Published by the American Physical Society 2024

Mass spectrum of 1−− heavy quarkonium

We calculate the masses and leptonic decay widths of the bottomonium bb¯ and charmonium cc¯ states in a constituent quark model where the Cornell-like potential and spin-dependent interaction are employed, with all model parameters predetermined by studying ground and first radial excited states of S- and P-wave heavy quarkonium mesons. By comparing the theoretical predictions for JPC=1−− quarkonium states with experimental data and considering possible mixtures of nS and (n−1)D states, we provide tentative assignments for all observed JPC=1−− heavy quarkonia. The work suggests that the ϒ(10860) and ϒ(11020) are bb¯ 5S−4D mixture states, and the ψ(4360) and ψ(4415) are largely 4S and 3D cc¯ states, respectively. The ψ(4230) may not be accommodated with the conventional meson picture in the present work. Published by the American Physical Society 2024