Decay Width Gamma Research Articles

On the two-loop BSM corrections to h⟶γγ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$h\\longrightarrow \\gamma \\gamma $$\\end{document} in the aligned THDM

We compute the two-loop BSM contributions to the h⟶γγ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$h\\longrightarrow \\gamma \\gamma $$\\end{document} decay width in the aligned THDM. We adopt the simplifying assumptions of vanishing EW gauge couplings and vanishing mass of the SM-like Higgs boson, which allow us to exploit a low-energy theorem connecting the hγγ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$h\\gamma \\gamma $$\\end{document} amplitude to the derivative of the photon self-energy w.r.t. the Higgs field. We briefly discuss the numerical impact of the newly-computed contributions, showing that they may be required for a precise determination of Γ[h→γγ]\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Gamma [h\\rightarrow \\gamma \\gamma ]$$\\end{document} in scenarios where the quartic Higgs couplings are large.

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.

The partial waves of B^{*}_{2}(5747) and their contributions in strong decays

The relativistic Bethe–Salpeter method is adopted to study the OZI-allowed strong decays of the 2^+ state B^{*}_{2}(5747)^{0}, with emphasis on the relativistic corrections. We first study the partial waves in the wave functions used and find that there are P, D, and F partial waves in the B^{*}_{2}(5747)^{0} meson, with ratios of P/D/F=1:0.421:0.051. We also find that S/P/D=1:0.354:0.046 for B^*, and S/P=1:0.343 for the B meson. The large components of the D wave in B^{*}_{2}(5747)^{0} and the P wave in B^{(*)} mean that large relativistic effects exist in these states. Second, we calculate the strong decays, and the total decay width Gamma (B^{*}_{2}(5747)^{0})=25.9 MeV and the branching fraction Gamma (B^{*}_{2}(5747)^{0} rightarrow B^{*}pi ) / Gamma (B^{*}_{2}(5747)^{0} rightarrow Bpi )=0.96 obtained are consistent with experimental data. Third, we study the contributions of different partial waves in the initial and final wave functions, and find that the relativistic effects are about 15% and 11% for B^{*}_{2}(5747)^{0} rightarrow Bpi and B^{*}_{2}(5747)^{0} rightarrow B^{*}pi , respectively, which are much smaller than our expected effects, showing that the relativistic corrections cancel each other in these decays.

The newly observed state D_{s0}(2590)^{+}

We choose the Reduction Formula, PCAC and Low Energy Theory to reduce the S matrix of a OZI allowed two-body strong decay involving a light pseudoscalar, the covariant transition amplitude formula with relativistic wave functions as input is derived. After confirm this method by the decay D^*(2010)rightarrow Dpi , we study the newly observed D_{s0}(2590)^{+} with supposing it to be the state D_s(2^1S_0)^+, we find its decay width Gamma is highly sensitive to the D_{s0}(2590)^{+} mass, which result in the meaningless comparison of widths by different models with various input masses. Instead of width, we studied the overlap integral over the wave functions of initial and final states, here we parameterized it as X which is model-independent, and the ratio Gamma /{|{mathbf {P}_f}|^3}, both are almost mass independent, to give us useful information. The results show that, all the existing theoretical predictions X_{D_s(2S) rightarrow D^*K}=0.25sim 0.41 and Gamma /{|{mathbf {P}_f}|^3}=0.81sim 1.77hbox {MeV}^{-2} are smaller than experimental data 0.585^{+0.015}_{-0.035} and 4.54^{+0.25}_{-0.52}hbox {MeV}^{-2}. Further compared with X^{ex}_{D^*(2010) rightarrow Dpi }=0.540pm 0.009, the current data X^{ex}_{D_s(2S) rightarrow D^*K}=0.585^{+0.015}_{-0.035} is too big to be an reasonable value, so it is early to say D_{s0}(2590)^{+} is the conventional D_s(2^1S_0)^+ meson.

Measurement of the CP-violating phase phi _s in B_{s}^{0} rightarrow J/psi phi decays in ATLAS at 13\xa0TeV

A measurement of the B_{s}^{0} rightarrow J/psi phi decay parameters using 80.5, mathrm {fb^{-1}} of integrated luminosity collected with the ATLAS detector from 13 text {Te}text {V} proton–proton collisions at the LHC is presented. The measured parameters include the CP-violating phase phi _{s} , the width difference Delta Gamma _{s} between the B_{s}^{0} meson mass eigenstates and the average decay width Gamma _{s}. The values measured for the physical parameters are combined with those from 19.2, mathrm {fb^{-1}} of 7 and 8 text {Te}text {V} data, leading to the following: ϕs=-0.087±0.036(stat.)±0.021(syst.)radΔΓs=0.0657±0.0043(stat.)±0.0037(syst.)ps-1Γs=0.6703±0.0014(stat.)±0.0018(syst.)ps-1\\documentclass[12pt]{minimal}\t\t\t\t\\usepackage{amsmath}\t\t\t\t\\usepackage{wasysym}\t\t\t\t\\usepackage{amsfonts}\t\t\t\t\\usepackage{amssymb}\t\t\t\t\\usepackage{amsbsy}\t\t\t\t\\usepackage{mathrsfs}\t\t\t\t\\usepackage{upgreek}\t\t\t\t\\setlength{\\oddsidemargin}{-69pt}\t\t\t\t\\begin{document}$$\\begin{aligned} \\phi _{s}= & {} -0.087 \\pm 0.036 ~\\mathrm {(stat.)} \\pm 0.021 ~\\mathrm {(syst.)~rad} \\\\ \\Delta \\Gamma _{s}= & {} 0.0657 \\pm 0.0043 ~\\mathrm {(stat.)}\\pm 0.0037 ~\\mathrm {(syst.)~ps}^{-1} \\\\ \\Gamma _{s}= & {} 0.6703 \\pm 0.0014 ~\\mathrm {(stat.)}\\pm 0.0018 ~\\mathrm {(syst.)~ps}^{-1} \\end{aligned}$$\\end{document}Results for phi _{s} and Delta Gamma _{s} are also presented as 68% confidence level contours in the phi _{s} – Delta Gamma _{s} plane. Furthermore the transversity amplitudes and corresponding strong phases are measured. phi _{s} and Delta Gamma _{s} measurements are in agreement with the Standard Model predictions.

Probing new U(1) gauge symmetries via exotic Z \u2192 Z\u2032\u03b3 decays

New U(1) gauge theories involving Standard Model (SM) fermions typically require additional electroweak fermions for anomaly cancellation. We study the non-decoupling properties of these new fermions, called anomalons, in the Z − Z′ − γ vertex function, reviewing the connection between the full model and the effective Wess-Zumino operator. We calculate the exotic Z → Z′γ decay width in U(1)B−L and U(1)B models, where B and L denote the SM baryon and lepton number symmetries. For U(1)B−L gauge symmetry, each generation of SM fermions is anomaly free and the exotic Z → {Z}_{BL}^{prime}gamma decay width is entirely induced by intragenerational mass splittings. In contrast, for U(1)B gauge symmetry, the existence of two distinct sources of chiral symmetry breaking enables a heavy, anomaly-free set of fermions to have an irreducible contribution to the Z → {Z}_B^{prime}gamma decay width. We show that the current LEP limits on the exotic Z → {Z}_B^{prime}gamma decay are weaker than previously estimated, and low-mass {Z}_B^{prime } dijet resonance searches are currently more constraining. We present a summary of the current collider bounds on U(1)B and a projection for a TeraZ factory on the Z → {Z}_B^{prime}gamma exotic decay, and emphasize how the Z → Z′γ decay is emblematic of new anomalous U(1) gauge symmetries.

The effect of an anomalous Higgs trilinear self-coupling on the h rightarrow gamma , Z decay

We compute the two-loop effects induced by an anomalous Higgs trilinear self-coupling in the partial decay width Gamma (h rightarrow gamma Z). The computation is performed using the anomalous coupling approach, working in the unitary gauge, and in a theory in which the anomalous coupling is generated via the addition to the scalar potential part of the Standard Model Lagrangian of an (in)finite tower of (Phi ^dagger Phi )^n terms. The former computation is automatically finite while the latter requires the renormalization of the lowest order contribution. We discuss the renormalization conditions that should be employed in order to obtain the same result in the two approaches. We find that the h rightarrow gamma Z process is one of the most sensitive mode to an anomalous trilinear Higgs self-coupling. As a by-product of this work we confirm one of two different results present in the literature concerning the contribution of an anomalous Higgs trilinear coupling in the h rightarrow gamma gamma decay.

The Upsilon (1S) leptonic decay using the principle of maximum conformality

In the paper, we study the Upsilon (1S) leptonic decay width Gamma (Upsilon (1S)rightarrow ell ^+ell ^-) by using the principle of maximum conformality (PMC) scale-setting approach. The PMC adopts the renormalization group equation to set the correct momentum flow of the process, whose value is independent to the choice of the renormalization scale and its prediction thus avoids the conventional renormalization scale ambiguities. Using the known next-to-next-to-next-to-leading order perturbative series together with the PMC single scale-setting approach, we do obtain a renormalization scale independent decay width, Gamma _{Upsilon (1S) rightarrow e^+ e^-} = 1.262^{+0.195}_{-0.175} keV, where the error is squared average of those from alpha _s(M_{Z})=0.1181pm 0.0011, m_b=4.93pm 0.03 GeV and the choices of factorization scales within pm 10% of their central values. To compare with the result under conventional scale-setting approach, this decay width agrees with the experimental value within errors, indicating the importance of a proper scale-setting approach.

Analysis of the mass and width of the X(4140) as axialvector tetraquark state

In this article, we construct both the [sc]_T[{bar{s}}{bar{c}}]_A+[sc]_A[{bar{s}}{bar{c}}]_T type and [sc]_T[{bar{s}}{bar{c}}]_V-[sc]_V[{bar{s}}{bar{c}}]_T type axialvector currents with J^{PC}=1^{++} to study the mass of the X(4140) with the QCD sum rules. The predicted masses support assigning the X(4140) to be the [sc]_T[{bar{s}}{bar{c}}]_V-[sc]_V[{bar{s}}{bar{c}}]_T type axialvector tetraquark state. Then we study the hadronic coupling constant g_{XJ/psi phi } with the QCD sum rules based on solid quark-hadron duality, and obtain the decay width Gamma (X(4140)rightarrow J/psi phi )=86.9pm 22.6,{mathrm{MeV}}, which is in excellent agreement with the experimental data 83pm 21^{+21}_{-14} { text{ MeV }} from the LHCb collaboration.

Udb¯b¯ tetraquark resonances with lattice QCD potentials and the Born-Oppenheimer approximation

We study tetraquark resonances with lattice QCD potentials computed for a static bbar bbar pair in the presence of two lighter quarks u d, the Born-Oppenheimer approximation and the emergent wave method. As a proof of concept we focus on the system with isospin I = 0, but consider different relative angular momenta l of the heavy quarks bbar bbar. For l=0 a bound state has already been predicted with quantum numbers I(JP) = 0(1+). Exploring various angular momenta we now compute the phase shifts and search for S and T matrix poles in the second Riemann sheet. We predict a tetraquark resonance for l =1, decaying into two B mesons, with quantum numbers I(JP) = 0(1-), mass m = 10 \, 576^{+4}_{-4} MeV} and decay width Gamma = 112^{+90}_{-103} MeV.

Unambiguous identification of the second 2+ state in 12C and the structure of the Hoyle state.

The second J(π)=2+ state of 12C, predicted over 50 years ago as an excitation of the Hoyle state, has been unambiguously identified using the 12C(γ,α0)(8)Be reaction. The alpha particles produced by the photodisintegration of 12C were detected using an optical time projection chamber. Data were collected at beam energies between 9.1 and 10.7 MeV using the intense nearly monoenergetic gamma-ray beams at the HIγS facility. The measured angular distributions determine the cross section and the E1-E2 relative phases as a function of energy leading to an unambiguous identification of the second 2+ state in 12C at 10.03(11) MeV, with a total width of 800(130) keV and a ground state gamma-decay width of 60(10) meV; B(E2:2(2)+→0(1)+)=0.73(13)e(2) fm(4) [or 0.45(8) W.u.]. The Hoyle state and its rotational 2+ state that are more extended than the ground state of 12C presents a challenge and constraints for models attempting to reveal the nature of three alpha-particle states in 12C. Specifically, it challenges the ab initio lattice effective field theory calculations that predict similar rms radii for the ground state and the Hoyle state.

DKmolecule in the Bethe-Salpeter equation approach in the heavy quark limit

In the heavy quark limit, we establish the Bethe-Salpeter equation for the possible molecular state containing one heavy meson D and one light meson K. With the kernel induced by one-particle-exchange diagrams, we solve the Bethe-Salpeter equation numerically in the ladder and covariant instantaneous approximations and find that the DK bound state may exist. Assuming the observed state D*(s0)(2317)(+) is an S-wave DK molecular bound state we calculate the strong decay width of D*(s0)(2317)(+). Our prediction for the decay width Gamma(D*(s0)(2317)(+) -> D-s(+) pi(0)) is consistent with the previous investigations and the current experimental data.

Applications of the USD Hamiltonians to rapid-proton capture rates for sd-shell nuclei

We discuss the use of the USD, USDA and USDB Hamiltonians for calculating rapid-proton capture rates for the sd-shell nuclei. The isobaric-mass-multiplet equation is used to make associations between the levels in the proton-rich nuclei of interest and those in the nuclei with N ≥ Z. The theoretical uncertainties associated with the calculated spectroscopic factors and gamma-decay widths are discussed. Results are shown for the 25Al(p,γ)26Si resonance-capture rate.

Hadronic light-by-light scattering in the muong−2: impact of proposed measurements of theπ0→γγdecay width and theγ*γ→π0transition form factor with the KLOE-2 experiment

We discuss, how planned measurements at KLOE-2 of the (pi^0 -> gamma gamma) decay width and the (gamma^* gamma -> pi^0) transition form factor can improve estimates for the numerically dominant pion-exchange contribution to hadronic light-by-light scattering in the muon g-2 and what are the limitations related to the modelling of the off-shellness of the pion.

Pair Decay Width of the Hoyle State and its Role for Stellar Carbon Production

The pair decay width of the first excited 0+ state in 12C (the Hoyle state) is deduced from a novel analysis of the world data on inelastic electron scattering covering a wide momentum transfer range, thereby resolving previous discrepancies. The extracted value Γπ=(62.3±2.0) μeV is independently confirmed by new data at low momentum transfers measured at the S-DALINAC and reduces the uncertainty of the literature values by more than a factor of 3. A precise knowledge of Γπ is mandatory for quantitative studies of some key issues in the modeling of supernovae and of asymptotic giant branch stars, the most likely site of the slow-neutron nucleosynthesis process.

Primakoff effect in $ \eta$ -photoproduction off protons

We analyse data on forward eta-meson photoproduction off a proton target and extract the eta to gamma gamma decay width utilizing the Primakoff effect. The hadronic amplitude that enters into our analysis is strongly constrained because it is fixed from a global fit to available gamma p to p eta data for differential cross sections and polarizations. We compare our results with present information on the two-photon eta-decay from the literature. We provide predictions for future PrimEx experiments at Jefferson Laboratory in order to motivate further studies.

Radiative B decay spectrum: DGE at NNLO

We compute the differential B -> X_s gamma decay width in the Standard Model as a function of the photon energy using Dressed Gluon Exponentiation (DGE). The resummed spectrum is matched with the fixed-order expansion, making use of the next-to-next-to-leading order (NNLO) results for the matrix element of the magnetic dipole interaction O_7 and NLO ones for other operators in the effective Weak Hamiltonian. We develop a new technique to implement constraints on the analytic structure of the Sudakov factor in moment space. This improves the behavior of the resummed spectrum away from the Sudakov region. We also derive an analytic expression for the Borel transform of the perturbative series for the O_7 spectrum in the large-beta_0 limit. Using this example we demonstrate that exponentiation in moment space is necessary for the calculation of the spectrum for E_gamma > 2 GeV. Finally, we investigate numerically the relation between renormalons, power corrections and support properties. We present predictions for the branching fraction and the first few spectral moments as a function of a cut E_gamma>E_0 and estimate the theoretical uncertainty.

Study of the 26Si(p,γ)27P reaction through Coulomb dissociation of 27P

The Coulomb dissociation of 27P was studied experimentally using 27P beams at 57 MeV/nucleon with a lead target. The E2 gamma decay width of the first excited state in 27P was determined to be (2.8 ± 0.5) × 10−5 eV. The total (M1+E2)gamma decay width of the state, which is of astrophysical interest, is estimated by combining the experimental result and a shell model calculation. The reaction rate of 26Si(p, γ)27P is deduced from the estimated total gamma decay width. The astrophysical implication derived from estimated gamma decay width is discussed.

Study of 26Si(p, γ) 27P reaction using Coulomb dissociation method

The Coulomb dissociation of 27 P was studied experimentally using 27 P beams at 57 MeV/nucleon with a lead target. The E2 gamma decay width of the first excited state in 27 P was extracted. Assuming the same E2/M1 mixing ratio as the one for the mirror nucleus 27 Mg, the gamma decay width of the state, which is of astrophysical interest, is estimated to be ten times smaller than the value calculated by J. A. Caggiano et al.

Constraints on the parameters of the left-right mirror model

We study some phenomenological constraints on the parameters of a left right model with mirror fermions (LRMM) that solves the strong CP problem. In particular, we evaluate the contribution of mirror neutrinos to the invisible Z decay width (\Gamma_Z^{inv}), and we find that the present experimental value on \Gamma_Z^{inv}, can be used to place an upper bound on the Z-Z' mixing angle that is consistent with limits obtained previously from other low-energy observables. In this model the charged fermions that correspond to the standard model (SM) mix with its mirror counterparts. This mixing, simultaneously with the Z-Z' one, leads to modifications of the \Gamma(Z --> f \bar{f}) decay width. By comparing with LEP data, we obtain bounds on the standard-mirror lepton mixing angles. We also find that the bottom quark mixing parameters can be chosen to fit the experimental values of R_b, and the resulting values for the Z-Z' mixing angle do not agree with previous bounds. However, this disagreement disappears if one takes the more recent ALEPH data.