Decay Branching Ratios Research Articles

Semileptonic decay of varOmega _c^0 rightarrow varXi ^- l^+ nu _l from light-cone sum rules

The weak decay process of varOmega _c to varXi is calculated in the method of QCD light-cone sum rule. The decay width of varOmega _c^0 rightarrow varXi ^- l^+ nu _l and its decay branching ratio are also calculated with the form factors from this work’s calculation. To the twist-6 distribution amplitudes, the form factors f_1=0.66pm 0.02, f_2=-0.76pm 0.03, g_1=0.06pm 0.01 and g_2=-0.44pm 0.01 are given at zero recoil point. The result of the semileptonic decay width of varOmega _c^0 rightarrow varXi ^-l^+nu _l is varGamma =(7.51pm 0.36)times 10^{-15}~mathrm{{GeV}} , and the prediction of the decay branching ratio Br(varOmega _c^0rightarrow varXi ^-l^+nu _l)=(3.06pm 0.15)times 10^{-3}. These results fit well with other works, and the decay width and branching ratio are improved. This not too small branching ratio gives a good direction to explore this decay channel in the future experiments.

Higgs decay to light (pseudo)scalars in the semi-constrained NMSSM * *Supported by National Natural Science Foundation of China (NSFC) (11605123)

The next-to minimal supersymmetric standard model (NMSSM) with non-universal Higgs masses, i.e., the semi-constrained NMSSM (scNMSSM), extends the minimal supersymmetric standard model (MSSM) by a singlet superfield and assumes universal conditions, except for the Higgs sector. It can not only maintain the simplicity and grace of the fully constrained MSSM and NMSSM and relieve the tension they have been facing since the discovery of the 125-GeV Higgs boson but also allow for an exotic phenomenon wherein the Higgs decay into a pair of light ( ) singlet-dominated (pseudo)scalars (hereafter, in this paper, we use "scalar" for both scalars and pseudoscalars, considering pseudoscalars can also be called CP-odd scalars). This condition can be classified into three scenarios according to the identitiesof the SM-like Higgs and the light scalar: (i) the light scalar is CP-odd, and the SM-like Higgs is ; (ii) the light scalar is CP-odd, and the SM-like Higgs is ; and (iii) the light scalar is CP-even, and the SM-like Higgs is . In this work, we compare the three scenarios, checking the interesting parameter regions that lead to the scenarios, the mixing levels of the doublets and singlets, the tri-scalar coupling between the SM-like Higgs and a pair of light scalars, the branching ratio of Higgs decay to the light scalars, and sensitivities in the detection of the exotic decay at the HL-LHC and future lepton colliders such as CEPC, FCC-ee, and ILC. Finally, several interesting conclusions are drawn, which are useful for understanding the different delicate mechanisms of the exotic decay and designing colliders in future.

Laser effect on the final products of Z-boson decay

Experimentalists have long sought a method that allows them to control the branching ratios of an unstable particle decay and direct some decay to follow one specific desired channel without another. The powerful laser could make this a reality. In this letter and within the framework of the standard electroweak model, we investigate theoretically the laser effect on the branching ratios of different Z-boson decay modes by calculating analytically the Z-boson decay into a fermion–antifermion pai in the presence of a circularly polarized electromagnetic field. It is found that, at high intensities, the Z-boson could only decay invisibly into neutrinos, and its decay into any other pair of charged fermions becomes impossible due to the increase in the effective mass that fermions acquire inside the electromagnetic field. The influence of the laser frequency and intensity on the lifetime is also included in order to confirm the surprising result obtained for the pion lifetime in a previous paper (Mouslih 2020 Phys. Rev. D 102 073006).

Revisiting the determining fraction of glueball component in f 0 mesons via radiative decays of J/ψ * *Supported by National Natural Science Foundation of China (11805160, 11747040, 11675082, 11605039)

QCD theory predicts the existence of glueballs, but so far all experimental endeavors have failed to identify any such states. To remedy this discrepancy between QCD, which has proven to be a successful theory for strong interactions, and the failure of experimental searches for glueballs, one is tempted to accept the promising interpretation that the glueballs mix with regular states of the same quantum numbers. The lattice estimate of the masses of pure glueballs ranges from 1 to 2 GeV, which is the region of the family. Thus many authors suggest that the mesonic series is an ideal place to study possible mixtures of glueballs and . In this paper, following the strategy proposed by Close, Farrar and Li, we try to determine the fraction of glueball components in mesons using the measured mass spectra and the branching ratios of radiative decays into mesons. Since the pioneering papers by Close et al., more than 20 years have elapsed and more accurate measurements have been done by several experimental collaborations, so it is time to revisit this interesting topic using new data. We suppose and to be pure quark states, while for , and , to fit both the experimental data of radiative decay and their mass spectra, glueball components are needed. Moreover, the mass of the pure glueball is phenomenologically determined.

The γ decay of the Hoyle and higher excitation energy states of 12C

The Hoyle state and few other excited levels of 12C are fundamental for the production of carbon in the universe. In particular, the γ decay branching ratio is of utmost importance, being the only way to produce a carbon at the ground state. For the purpose to precisely investigate the decay mechanism of such states we conducted an experiment, at Laboratori Nazionali del Sud-Istituto Nazionale di Fisica Nucleare (INFN-LNS), using the reaction α + 12 C at 64 MeV. We used the 4π CHIMERA detector to detect both α and γ 12 C decay channels. Details of the experiment and preliminary results are discussed in the paper.

The scale of superpartner masses and electroweakino searches at the high-luminosity LHC

Searches for weakly interacting particles is one of the main goals of the high luminosity LHC run. In this work we study the well motivated cases of electroweakinos with mostly Wino and Bino components. We show the relevance of squark induced t-channel production in defining the production cross section and hence the LHC reach. Moreover, a realistic evaluation of the decay branching ratios show a strong dependence on the sign of μ and, for negative values of μ, on the relative size of the ratio of μ to the gaugino masses compared with tan β. Overall, unless it is kinematically suppressed, or specific conditions are fulfilled, the Higgs decay channel is the most significant one, and the trilepton channel becomes subdominant with respect to final states including bottom quarks. Although the properties are different than in the Higgsino-Bino case, also in this case the discovery reach extends to mass values that are significantly larger than the ones probed at current luminosities, leading to a strong motivation for the search for electroweakinos in the high luminosity LHC run.

Search for SU(2) V singlet Higgs boson in the Georgi–Machacek model at the LHC

In this paper, we study in detail the phenomenology of the non-SM SU(2) V singlet Higgs boson at the 14 TeV Large Hadron Collider (LHC) in the Georgi–Machacek (GM) model. We present a systematic comparison of the production mechanisms and decay modes of , especially the vector-boson fusion (VBF) and gluon–gluon fusion (ggF) production mechanisms and the decays to W + W −, ZZ, H 5 H 5, H 3 H 3, and . After performing a comprehensive scan over the seven-dimensional parameter space of the GM model, we find that the , and decay channels are almost excluded by the theoretical and experimental constraints, while can decay into H 5 H 5 in an appreciable region of the GM parameter space. Based on the scanning results, we discuss detailedly the production via ggF and VBF with subsequent decays of , and at the 14 TeV LHC. The integrated cross sections and some kinematic distributions of final products for both the signals at some benchmark points of the GM parameter space and the corresponding SM backgrounds are provided. If the decay to H 5 H 5 is kinematically allowed, can be detected in the decay channel at high-luminosity LHC unless is too small or is too high. In the mass range of , the vector-boson fusion is the most promising production channel in search of due to the two hard tagging jets in the final state, and we may expect to discover in both and decay channels with of data if the decay branching ratio of to a pair of weak gauge bosons is sufficiently large.

Spectroscopic study of Ca47 from the β− decay of K47

The $\beta^-$ decay of $^{47}$K to $^{47}$Ca is an appropriate mechanism for benchmarking interactions spanning the $sd$ and $pf$ shells, but current knowledge of the $\beta^-$-decay scheme is limited. We have performed a high-resolution, high-efficiency study of the $\beta^-$-decay of $^{47}$K with the GRIFFIN spectrometer at TRIUMF-ISAC. The study revealed 48 new transitions, a more precise value for the $^{47}$K half-life (17.38(3)~s), and new spin and parity assignments for eight excited states. Levels placed for the first time here raise the highest state observed in $\beta^-$ decay to within 568(3) keV of the $Q$-value and confirm the previously measured large $\beta^-$-decay branching ratios to the low-lying states. Previously unobserved $\beta^-$-feeding to 3/2$^+$ states between 4.5 and 6.1~MeV excitation energy was identified with a total $\beta^-$-feeding intensity of 1.29(2)\%. The sum of the $B(GT)$ values for these states indicates that the $1s_{1/2}$ proton hole strength near this excitation energy is comparable to the previously known $1s_{1/2}$ proton and neutron hole strengths near 2.6 MeV.

Decay Properties of Conventional and Hybrid $$\boldsymbol{B}_{\boldsymbol{c}}$$ Mesons

Spectrum, radial wave functions at origin, decay constants, weak decay widths, life-time, and branching ratios for radially excited conventional and hybrid $$B_{c}$$ mesons are derived within non-relativistic quark model framework employing Schrodinger equation by shooting method. Calculated results are compared with available theoretical results and experimental observations. This work may help in identifying the new discovered $$B_{c}$$ meson states at CDF, LHCb, and ATLAS.

Enhancing sensitivities to long-lived particles with high granularity calorimeters at the LHC

The search for long-lived particles (LLP) is an exciting physics opportunity in the upcoming runs of the Large Hadron Collider. In this paper, we focus on a new search strategy of using the High Granularity Calorimeter (HGCAL), part of the upgrade of the CMS detector, in such searches. In particular, we demonstrate that the high granularity of the calorimeter allows us to see “shower tracks” in the calorimeter, and can play a crucial role in identifying the signal and suppressing the background. We study the potential reach of the HGCAL using a signal model in which the Standard Model Higgs boson decays into a pair of LLPs, h → XX. After carefully estimating the Standard Model QCD and the misreconstructed fake-track backgrounds, we give the projected reach for both an existing vector boson fusion trigger and a novel displaced-track-based trigger. Our results show that the best reach for the Higgs decay branching ratio, BR(h → XX), in the vector boson fusion channel is about mathcal{O} (10−4) with lifetime cτX ∼ 0.1–1 meters, while for the gluon gluon fusion channel it is about mathcal{O} (10−5–10−6) for similar lifetimes. For longer lifetime cτX ∼ 103 meters, our search could probe BR(h → XX) down to a few ×10−4(10−2) in the gluon gluon fusion (vector boson fusion) channels, respectively. In comparison with these previous searches, our new search shows enhanced sensitivity in complementary regions of the LLP parameter space. We also comment on many improvements can be implemented to further improve our proposed search.

Laser-assisted pion decay

This paper revives the controversial debate that has arisen over the last two decades about the possibility that the electromagnetic field affects the lifetime or the decay rate of an unstable particle. In this research, we show, by performing analytical calculations and extracting numerical results, that the pion lifetime can be changed notably by inserting the decaying pion into an electromagnetic field only if the number of photons transferred between the decaying system and the laser field does not reach the well-known sum-rule. The influence of the laser parameters on the decay rate and branching ratio is also discussed. The surprising result obtained for the pion lifetime is referred to as the well-known quantum Zeno effect.

α decay of Fm243143 and Fm245145 , and of their daughter nuclei

Nuclear structure of $^{243}\mathrm{Fm}$, $^{245}\mathrm{Fm}$, and their daughter nuclei were investigated via detection of their radioactive decays, $\ensuremath{\alpha}$, $\ensuremath{\gamma}$, and spontaneous fission. Measured $\ensuremath{\alpha}$-decay energies, half-lives, and branching ratios improve the literature data significantly. A signature for detection of the hitherto unknown $^{235}\mathrm{Cm}$ was found in the $\ensuremath{\alpha}$-decay chains from $^{243}\mathrm{Fm}$. Two groups of $\ensuremath{\alpha}$ events with average energies of 6.69(2) MeV and 7.01(2) MeV and with a half-life of ${T}_{1/2}={300}_{\ensuremath{-}100}^{+250}$ s are suggested to originate from $^{235}\mathrm{Cm}$. Tentative decay schemes for $^{243}\mathrm{Fm}$, $^{239}\mathrm{Cf}$, $^{235}\mathrm{Cm}$, and $^{245}\mathrm{Fm}$, $^{241}\mathrm{Cf}$ isotopes are suggested based on the present experimental data. Systematical trends of single-particle states in $N=141$ isotones of $Z=92--98$ nuclei are discussed.

Photo response of Dy164

Background: Little data is available for the pygmy dipole resonance (PDR) in axially deformed nuclei. Photon-scattering experiments are complicated by high level densities in the PDR region and the small energy difference of transitions to the ground state and to excited states.Purpose: We report on an experimental study of the low-energy dipole strength distribution of the well-deformed nucleus $^{164}\mathrm{Dy}$ between 4.0--7.7 MeV.Methods: The low-lying photoresponse of $^{164}\mathrm{Dy}$ has been investigated using the method of nuclear resonance fluorescence using a quasimonochromatic linearly polarized $\ensuremath{\gamma}$-ray beam in the energy range of 4.0--7.7 MeV in steps of 0.2 MeV.Results: For excitation energies between 4 MeV and 5 MeV, sufficiently low level densities allow for the identification of individual states, including level energies, reduced transition widths and branching ratios. Energy-averaged mean decay branching ratios, mean population ratios and partial absorption cross sections were determined above 5 MeV up to the neutron-separation threshold at 7.7 MeV. A Lorentzian-shaped enhancement of the partial photo absorption cross section followed by decays back to the ground-state band is found at 6.10(5) MeV with a width of 0.77(23) MeV. A comparison with results from complementary measurements is performed using the framework of the statistical model.Conclusions: The experimental results for the mean population ratios deviate systematically from the statistical model simulation by 30(6)%. However, they are in agreement within one standard deviation of the simulation.

Study of semileptonic decay of in QCD sum rule

In this work we study the semileptonic decay of (l = e, μ, τ) with the QCD sum rule method. We calculate the translation form factors relevant to this semileptonic decay, then the branching ratios of (l = e, μ, τ) decays are calculated with the form factors obtained here. Our result for the branching ratio of agree very well with the recent experimental data. For the unmeasured decay modes such as and , we give theoretical predictions.

ΔK=0 M1 Excitation Strength of the Well-Deformed Nucleus Dy164 from K Mixing

The size of a ΔK=0 M1 excitation strength has been determined for the first time in a predominantly axially deformed even-even nucleus. It has been obtained from the observation of a rare K-mixing situation between two close-lying J^{π}=1^{+} states of the nucleus ^{164}Dy with components characterized by intrinsic projection quantum numbers K=0 and K=1. Nuclear resonance fluorescence induced by quasimonochromatic linearly polarized γ-ray beams provided evidence for K mixing of the 1^{+} states at 3159.1(3) and 3173.6(3)keV in excitation energy from their γ-decay branching ratios into the ground-state band. The ΔK=0 transition strength of B(M1;0_{1}^{+}→1_{K=0}^{+})=0.008(1)μ_{N}^{2} was inferred from a mixing analysis of their M1 transition rates into the ground-state band. It is in agreement with predictions from the quasiparticle phonon nuclear model. This determination represents first experimental information on the M1 excitation strength of a nuclear quantum state with a negative R-symmetry quantum number.

Effect of the early kinetic decoupling in a fermionic dark matter model

We study the effect of the early kinetic decoupling in a model of fermionic dark matter (DM) that interacts with the standard model particles only by exchanging the Higgs boson. There are two DM-Higgs couplings, namely CP-conserving and CP-violating couplings. If the mass of the DM is slightly below half of the Higgs boson mass, then the couplings are suppressed to obtain the measured value of the DM energy density by the freeze-out mechanism. In addition, the scattering processes of DM off particles in the thermal bath are suppressed by the small momentum transfer if the CP-violating DM-Higgs coupling is larger than the CP-conserving one. Due to the suppression, the temperature of the DM can differ from the temperature of the thermal bath. By solving coupled equations for the number density and temperature of the DM, we calculate the DM-Higgs couplings that reproduce the right amount of the DM relic abundance. We find that the couplings have to be larger than the one obtained without taking into account the difference in the temperatures. A consequence of the enhancement of the DM-Higgs couplings is the enhancement of the Higgs invisible decay branching ratio. The enhancement is testable at current and future collider experiments.

Improved precision on the experimental E0 decay branching ratio of the Hoyle state

Background: Stellar carbon synthesis occurs exclusively via the 3α process, in which three α particles fuse to form C12 in the excited Hoyle state, followed by electromagnetic decay to the ground state. The Hoyle state is above the α threshold, and the rate of stellar carbon production depends on the radiative width of this state. The radiative width cannot be measured directly, and must instead be deduced by combining three separately measured quantities. One of these quantities is the E0 decay branching ratio of the Hoyle state, and the current 10% uncertainty on the radiative width stems mainly from the uncertainty on this ratio. The rate of the 3α process is an important input parameter in astrophysical calculations on stellar evolution, and a high precision is imperative to constrain the possible outcomes of astrophysical models. Purpose: To deduce a new, more precise value for the E0 decay branching ratio of the Hoyle state. Method: The E0 branching ratio was deduced from a series of pair conversion measurements of the E0 and E2 transitions depopulating the 02+ Hoyle state and 21+ state in C12, respectively. The excited states were populated by the C12(p,p′) reaction at 10.5 MeV beam energy, and the pairs were detected with the electron-positron pair spectrometer, Super-e, at the Australian National University. The deduced branching ratio required knowledge of the proton population of the two states, as well as the alignment of the 21+ state in the reaction. For this purpose, proton scattering and γ-ray angular distribution experiments were also performed. Results: An E0 branching ratio of ΓπE0/Γ=8.2(5)×10−6 was deduced in the current work, and an adopted value of ΓπE0/Γ=7.6(4)×10−6 is recommended based on a weighted average of previous literature values and the new result. Conclusions: The new recommended value for the E0 branching ratio is about 14% larger than the previous adopted value of ΓπE0/Γ=6.7(6)×10−6, while the uncertainty has been reduced from 9% to 5%. The new result reduces the radiative width, and hence 3α reaction rate, by 11% relative to the adopted value, and the uncertainty to 6.1%. This reduction in width and increased precision is likely to constrain possible outcomes of astrophysical calculations.6 MoreReceived 28 May 2020Accepted 29 July 2020DOI:https://doi.org/10.1103/PhysRevC.102.024320©2020 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasElectromagnetic transitionsNuclear astrophysicsNuclear structure & decaysSpectroscopic factors & electromagnetic momentsProperties6 ≤ A ≤ 19Nuclear Physics

Electromagnetic properties of 21O for benchmarking nuclear Hamiltonians

The structure of exotic nuclei provides valuable tests for state-of-the-art nuclear theory. In particular electromagnetic transition rates are more sensitive to aspects of nuclear forces and many-body physics than excitation energies alone. We report the first lifetime measurement of excited states in 21O, finding τ1/2+=420−32+35(stat)−12+34(sys) ps. This result together with the deduced level scheme and branching ratio of several γ-ray decays are compared to both phenomenological shell-model and ab initio calculations based on two- and three-nucleon forces derived from chiral effective field theory. We find that the electric quadrupole reduced transition probability of B(E2;1/2+→5/2g.s.+)=0.71−0.06−0.06+0.07+0.02 e2fm4, derived from the lifetime of the 1/2+ state, is smaller than the phenomenological result where standard effective charges are employed, suggesting the need for modifications of the latter in neutron-rich oxygen isotopes. We compare this result to both large-space and valence-space ab initio calculations, and by using multiple input interactions we explore the sensitivity of this observable to underlying details of nuclear forces.

Visible emission studies of melt-grown Dy-doped CsPbCl3 and KPb2Cl5 crystals

We report results of the optical properties of Dy-doped CsPbCl3 and KPb2Cl5 bulk crystals for potential applications in yellow solid-state laser development. The crystals were synthesized from purified starting materials and melt-grown by vertical Bridgman technique. Optical transmission measurements revealed characteristic absorption bands from intra-4f transitions of Dy3+ ions. Direct optical excitation at 455 nm (6H15/2 → 4I15/2) resulted in dominant yellow emission bands at ∼575 nm from the 4F9/2 excited state of Dy3+ ions. In addition, both crystals exhibited weaker emission lines in the blue (∼483 nm) and red (∼670 nm) regions. The peak emission-cross sections for the yellow transition (4F9/2 → 6H13/2) were determined to be ∼0.22 × 10−20 cm2 for Dy: CsPbCl3 (λpeak = 576.5 nm) and ∼0.59 × 10−20 cm2 for Dy: KPb2Cl5 (λpeak = 574.5 nm). The spectral properties and decay dynamics of the 4F9/2 excited state were evaluated within the Judd-Ofelt theory to predict total radiative decay rates, branching ratios, and emission quantum efficiencies.

H-COUP Version 2: A program for one-loop corrected Higgs boson decays in non-minimal Higgs sectors

We present the concept of H-COUP_ver 2, which evaluates the decay rates (including higher order corrections) for the Higgs boson with a mass of 125GeV in various extended Higgs models. In the previous version (H-COUP_1.0), only a full set of the Higgs boson vertices are evaluated at one-loop level in a gauge invariant manner in these models. H-COUP_ver 2 contains all the functions of H-COUP_1.0. After shortly introducing these extended Higgs models and discussing their theoretical and experimental constraints, we summarize formulae for the renormalized vertices and the decay rates. We then explain how to install and run H-COUP_ver 2 with some numerical examples. Program summaryProgram title: H-COUP Version 2CPC Library link to program files: http://dx.doi.org/10.17632/f88szmrj5x.2Developer’s repository link: http://www-het.phys.sci.osaka-u.ac.jp/ hcoup/Licensing provisions: GPLv3Programming language: Fortran90Journal Reference of previous version: Comput. Phys. Commun. 233 (2018), 134–144Does the new version supersede the previous version?: YesReasons for the new version: The previous version (H-COUP_1.0), which numerically evaluates the full set of one-loop corrected vertex functions for the Higgs boson with a mass of 125 GeV, does not automatically provide the decay rates, the total decay width and branching ratios. In addition, QCD corrections have not been included in the previous version.Summary of revisions: Decay branching ratios and the total decay width for the Higgs boson with NLO electroweak and NNLO QCD corrections are added as outputs.Nature of problem: Decay rates for the Higgs boson and the total decay width are numerically evaluated at NLO for electroweak and NNLO for QCD in the Higgs singlet model, four types (Type-I, Type-II, Type-X, Type-Y) of two Higgs doublet models with a softly-broken Z2 symmetry and the inert doublet model.Solution of method: Electroweak and QCD corrections to the decay rates are computed by the improved on-shell scheme and the MS¯ scheme, respectively.Additional comments including restrictions and unusual features: All functions of the previous version are included in H-COUP_ver 2.