The mass structure of hadron multiplets is understood to imply the inexactness of SU(3) symmetry. Here we show that these symmetry broken mass splittings amongst baryon and meson multiplet members are close integral multiples of the mass difference between a neutral pion and a muon, the first excitation within the elementary particle mass spectrum. This is found to be equally true for the mass intervals amongst the particles belonging to the multiplets having different spin and parity characteristics. The results reinforce our earlier contention that the mass difference between a neutral pion and a muon is of fundamental importance to the elementary particle mass distribution.
Restrictions on the Hadronic Contribution to the Muon $(g-2)$-factor and to the Pion Electromagnetic Formfactor from Analytical Properties of the Pion Electromagnetic Formfactor
We study the structure of heavy quark spin (HQS) multiplets for heavy meson-baryon molecular states in a coupled system of $\bar{P}^{(*)}Σ_{Q}^{(*)}$, with constructing the one-pion exchange potential with S-wave orbital angular momentum. Using the light cloud spin basis, we find that there are four types of HQS multiplets classified by the structure of heavy quark spin and light cloud spin. The multiplets which have attractive potential are determined by the sign of the coupling constant for the heavy meson-pion interactions. Furthermore, the difference in the structure of light cloud spin gi…
The largest error in the theoretical determination of the muon anomalous magnetic moment is due to the low-energy hadronic vacuum polarization, which cannot be calculated by perturbative QCD and requires nonperturbative techniques. Recently, an accurate determination of the low-energy two-pion contribution to muon $g-2$ has been obtained by a parametrization-free analytic continuation of the pion vector form factor from other kinematical regions. In this work we compare the results of the analytic continuation with direct determinations at low momenta from experiment and lattice QCD. We also e…
This paper contains some new results on the hadronic light-by-light contribution (HLbL) to the muon $g-2$. The first part argues that we can expect large effects from disconnected diagrams in present and future calculations by lattice QCD of HLbL. The argument is based on the dominance of pseudo-scalar meson exchange. In the second part, we revisit the pion loop HLbL contribution to the muon anomalous magnetic moment. We study it in the framework of some models studied earlier, pure pion loop, full VMD and hidden local symmetry for inclusion of vector mesons. In addition we study possible ways…
New confining sectors can contain a set of pseudo-Goldstone mesons that exhibit a complicated structure in terms of stability and relative masses. Stable ones can act as dark matter candidates, while their interactions with the unstable ones determine their relic abundances. The overall structure, by specifying which channels are kinematically forbidden or not, affects the cosmology, constraints and collider phenomenology. In this paper, we present a classification of these pseudo-Goldstone meson structures. We find that the structures can be classified into three categories, corresponding to …
In the present work, we investigate several theoretical models of the pion vector form factor and aim at getting the best fit for the two-pion cross sections to reduce the uncertainties of the calculation of two-pion contribution to the muon anomalous magnetic moment. Combined with a polynomial description to the pion vector form factor, we obtain the best fit from the Gounaris-Sakurai (or Kühn-Santamaria) model for the experimental data up to 1 GeV. By product, the branching ratio of $ω\to ππ$ can be extracted as $\text{Br}(ω\toππ)=(1.52\pm 0.06) \%$, which is consistent with the one of Parti…
我们回顾最近的测量罕见的π衰变：Pi+ -> Pi 0 e+ Nu [π β，Pi_（e3），或Pi_β衰变]，辐射衰变Pi+ -> e+ Nu γ [Pi_（e2 γ）或RPD]，和Pi+ -> e+ Nu [Pi_（e2）]衰变，以及辐射μ子衰变Mu -> e Nu Nu-bar γ，它们的理论意义以及进一步改进的前景。
Hadronic light-by-light scattering in the muon g-2: impact of proposed measurements of the (pi^0 -> gamma gamma) decay width and the (gamma^* gamma -> pi^0) transition form factor with the KLOE-2 experiment
We propose a one-loop neutrino mass model with several $SU(2)_L$ multiplet fermions and scalar fields in which the inert feature of a scalar to realize the one-loop neutrino mass can be achieved by the cancellation among Higgs couplings thanks to non-trivial terms in the Higgs potential and to present it in a simpler way. Then we discuss our typical cut-off scale by computing renormalization group equation for $SU(2)_L$ gauge coupling, lepton flavor violations, muon anomalous magnetic moment, possibility of dark matter candidate, neutrino mass matrix satisfying the neutrino oscillation data. F…
We have previously calculated the pion-nucleon $Σ_{πN}$ term in the chiral mixing approach with $u,d$ flavors only, and found the lower bound $Σ_{πN} \geq \left(1 + \frac{16}{3} \sin^2 θ\right){3 \over 2} \left(m_{u}^{0} + m_{d}^{0}\right)$. The mixing angle $θ$ can be calculated as $\sin^2θ= \frac{3}{8}\left(g_A^{(0)} + g_A^{(3)}\right)$. With presently accepted values of current quark masses, this leads to $Σ_{πN} \geq 58.0 \pm 4.5 \begin{array}{l} +11.4 \\ -6.5 \end{array}$ MeV, which is in agreement with the values extracted from experiments, and substantially higher than most previous two…
We report a lattice QCD calculation of the hadronic light-by-light contribution to the muon anomalous magnetic moment at physical pion mass. The calculation includes the connected diagrams and the leading, quark-line-disconnected diagrams. We incorporate algorithmic improvements developed in our previous work. The calculation was performed on the $48^3 \times 96$ ensemble generated with a physical-pion-mass and a 5.5 fm spatial extent by the RBC and UKQCD collaborations using the chiral, domain wall fermion (DWF) formulation. We find $a_μ^{\text{HLbL}} = 5.35 (1.35) \times 10^{- 10}$, where th…
We propose a scenario where only the Higgs multiplets have direct couplings to a supersymmetry (SUSY) breaking sector. The standard model matter multiplets as well as the gauge multiples are sequestered from the SUSY breaking sector; therefore, their masses arise via anomaly mediation at the high energy scale with a gravitino mass of $\sim$100 TeV. Due to renormalization group running effects from the Higgs soft masses, the masses of the third generation sfermions become O(10) TeV at the low energy scale, while the first and second generation sfermion masses are O(0.1-1) TeV, avoiding the tach…
We extend our previous calculations of the hadronic light-by-light scattering contribution to the muon anomalous magnetic moment in holographic QCD to models with finite quark masses and a tower of massive pions. Analysing the role of the latter in the Wess-Zumino-Witten action, we show that the Melnikov-Vainshtein short-distance constraint is satisfied solely by the summation of contributions from the infinite tower of axial vector meson contributions. There is also an enhancement of the asymptotic behavior of pseudoscalar contributions when their infinite tower of excitations is summed, but …
A lattice computation of the leading-order hadronic contribution to the muon anomalous magnetic moment can potentially help reduce the error on the Standard Model prediction for this quantity, if sufficient control of all systematic errors affecting such a computation can be achieved. One of these systematic errors is that associated with the extrapolation to the physical pion mass from values on the lattice larger than the physical pion mass. We investigate this extrapolation assuming lattice pion masses in the range of 200 to 400MeV with the help of two-loop chiral perturbation theory, and f…
We have computed the hadronic light-by-light (LbL) contribution to the muon anomalous magnetic moment $a_μ$ in the frame of Chiral Perturbation Theory with the inclusion of the lightest resonance multiplets as dynamical fields (R$χ$T). It is essential to give a more accurate prediction of this hadronic contribution due to the future projects of J-Parc and FNAL on reducing the uncertainty in this observable. We, therefore, computed the pseudoscalar transition form factor and proposed the measurement of the $e^+e^-\toμ^+μ^-π^0$ cross section and dimuon invariant mass spectrum to determine more a…
In a previous publication, we showed that a high energy muon collider can make decisive statements about the electroweak (WIMP) Dark Matter (DM), reaching a DM mass which could give the observed thermal relic abundance. In this document, we report new studies of the spin-$0$ minimal WIMP DM at high energy muon colliders, and update our results on the fermionic spin-$1/2$ case. We find that, by combining multiple inclusive missing mass search channels, it is possible to fully cover the thermal targets of fermionic and scalar doublets, and Dirac triplet, with a 10 TeV muon collider. Higher energ…
There exists a longstanding disagreement between bubble chamber measurements of the single pion production channel $ν_μp\rightarrow μ^{-}pπ^{+}$ from the Argonne and Brookhaven National Laboratories. We digitize and reanalyse data from both experiments to produce cross-section ratios for various interaction channels, for which the flux uncertainties cancel, and find good agreement between the experiments. By multiplying the cross-section ratio by the well-understood charged current quasi-elastic cross-section on free nucleons, we extract single-pion production cross-sections which do not depen…
Simple dynamics, few available decay channels, and extremely well controlled radiative and loop corrections, make pion and muon decays a sensitive means for testing the underlying symmetries, the universality of weak fermion couplings, as well as for study of pion structure and chiral dynamics. We review the current state of experimental study of the allowed rare decays of charged pions: (a) electronic, $π^+ \to e^+ν_e$, or $π_{e2}$, (b) radiative, $π^+ \to e^+ν_eγ$, or $π_{e2γ}$, and (c) semileptonic, $π^+\to π^0 e^+ ν$, or $π_{e3}$, as well as muon radiative decay, $μ^+\to e^+ ν_{\text{e}}\b…
We compute the decay rate of dimuonium into a neutral pion and a photon. We find that approximately one in 10^5 ortho-dimuonia decays into this channel. We also determine the contribution of the virtual photon-pion loop to the hyperfine splitting in dimuonium and reproduce its leading effect in the anomalous magnetic moment of the muon.
