Daisuke Nomura

Improved predictions for g−2 of the muon and αQED(MZ2)

We update the Standard Model predictions of the anomalous magnetic moment of the muon, a_\mu = (g-2)/2, and the value of the QED coupling at the Z-boson mass, incorporating the new e^+e^- \to \pi\pi data obtained by CMD-2 and KLOE, as well as the corrected SND data, and other improvements. The prediction for a_\mu=11659180.4 (5.1) \times 10^{-10} is about 3 \times 10^{-10} lower than before, and has a smaller uncertainty, which corresponds to a 3.4\sigma deviation from the measured value. The prediction for the QED coupling is \alpha(M_Z^2)^{-1}= 128.937 \pm 0.030.

Quest for precision in hadronic cross sections at low energy: Monte Carlo tools vs. experimental data

We present the achievements of the last years of the experimental and theoretical groups working on hadronic cross section measurements at the low-energy e+e− colliders in Beijing, Frascati, Ithaca, Novosibirsk, Stanford and Tsukuba and on τ decays. We sketch the prospects in these fields for the years to come. We emphasise the status and the precision of the Monte Carlo generators used to analyse the hadronic cross section measurements obtained as well with energy scans as with radiative return, to determine luminosities and τ decays. The radiative corrections fully or approximately implemented in the various codes and the contribution of the vacuum polarisation are discussed.

Predictions for g-2 of the muon and alpha(QED) (M**2(Z))

We calculate (g-2) of the muon and the QED coupling alpha(M_Z^2), by improving the determination of the hadronic vacuum polarization contributions and their uncertainties. We include the recently re-analysed CMD-2 data on e^+e^- -> pi^+ pi^-. We carefully combine a wide variety of data for the e^+e^- production of hadrons, and obtain the optimum form of R(s) = sigma_had^0(s)/sigma_pt(s), together with its uncertainty. Our results for the hadronic contributions to g-2 of the muon are a_mu^(had, LO) = (692.4 +- 5.9_exp +- 2.4_rad) * 10^(-10) and a_mu^(had, NLO) = (-9.8 +- 0.1_exp +- 0.0_rad) * 10^(-10), and for the QED coupling Delta alpha^(5)_had (M_Z^2)= (275.5 +- 1.9_exp +- 1.3_rad) * 10^(-4). These yield (g-2)/2 = 0.00116591763(74), which is about 2.4 sigma below the present world average measurement, and alpha(M_Z^2)^(-1) = 128.954 +- 0.031. We compare our (g-2) value with other predictions and, in particular, make a detailed comparison with the latest determination of (g-2) by Davier et al.

The SM prediction of g-2 of the muon

Abstract We calculate ( g −2)/2 of the muon, by improving the determination of the hadronic vacuum polarisation contribution, a had, LO μ , and its uncertainties. The different e + e − data sets for each exclusive (and the inclusive) channel are combined in order to obtain the optimum estimate of the cross sections and their uncertainties. QCD sum rules are evaluated in order to resolve an apparent discrepancy between the inclusive data and the sum of the exclusive channels. We conclude a had, LO μ =(683.1±5.9 exp ±2.0 rad )×10 −10 which, when combined with the other contributions to ( g −2)/2, is about 3 σ below the present world average measurement.

The MSSM confronts the precision electroweak data and the muon g − 2

We update the electroweak study of the predictions of the Minimal Super-symmetric Standard Model (MSSM) including the recent results on the muon anomalous magnetic moment, the weak boson masses, and the final precision data on the Z boson parameters from LEP and SLC. We find that the region of the parameter space where the slepton masses are a few hundred GeV is favored from the muon g − 2 for tan β ~ 10, whereas for tan β ≃ 50 heavier slepton mass up to ~ 1000 GeV can account for the reported 3.2 σ difference between its experimental value and the Standard Model (SM) prediction. As for the electroweak measurements, the SM gives a good description, and the sfermions lighter than 200 GeV tend to make the fit worse. We find, however, that sleptons as light as 100 to 200 GeV are favored also from the electroweak data, if we leave out the jet asymme-try data that do not agree with the leptonic asymmetry data. We extend the survey of the preferred MSSM parameters by including the constraints from the b → sγ transition, and find favorable scenarios in the minimal supergravity, gauge-, and mirage-mediation models of supersymmetry breaking.

Update of g-2 of the Muon and Delta Alpha

We update our Standard Model predictions for g-2 of the muon and for the hadronic contributions to the running of the QED coupling, Δα(5)had(M2Z). Particular emphasis is put on recent changes in the hadronic contributions from new data in the 2π channel and from the energy region just below 2 GeV.

Improved predictions for g-2 of the muon and \alpha_{\rm QED}(M_Z^2)

We update the Standard Model predictions of the anomalous magnetic moment of the muon, a_\mu = (g-2)/2, and the value of the QED coupling at the Z-boson mass, incorporating the new e^+e^- \to \pi\pi data obtained by CMD-2 and KLOE, as well as the corrected SND data, and other improvements. The prediction for a_\mu=11659180.4 (5.1) \times 10^{-10} is about 3 \times 10^{-10} lower than before, and has a smaller uncertainty, which corresponds to a 3.4\sigma deviation from the measured value. The prediction for the QED coupling is \alpha(M_Z^2)^{-1}= 128.937 \pm 0.030.

Hunting for the top partner in the littlest Higgs model with T parity at the CERN LHC

Little Higgs scenario provides us a new solution for the hierarchy and fine tuning problem of the Standard Model. Furthermore, the Littlest Higgs model with T‐parity, which is one of models in this scenario, solves the dark matter problem in our universe. The model predicts existence of a new vector‐like quark, in addition of a whole spectrum of heavy particles including the dark matter. In this talk, we discuss the phenomenology of the little Higgs model, focusing on the collider signature of this new vector‐like quark at the CERN LHC experiment.

Hadronic contributions to the anomalous magnetic moment of the electron and the hyperfine splitting of muonium

Motivated by recent progress of theory and experiment on the anomalous magnetic moment of the electron, ae, we update the hadronic contributions to ae. Using our up-to-date compilation of e + e − ! hadrons data, we find the leading order hadronic contribution a had,LO,VP e = (1.866 ±0.010exp ±0.005rad) · 10 −12 and the next-to-leading order hadronic contribution a had,NLO,VP e = ( 0.2234±0.0012exp ±0.0007rad)·10 −12 , where the first and second errors are from the error of the experimental data and the uncertainty in the treatment of radiative corrections, respectively. These values are compatible with earlier evaluations by other groups, but have significantly improved uncertainties due to the more precise input data used. We also update the leading order hadronic contribution to the ground state hyperfine splitting of muonium, obtaining �� had,VP Mu = (232.68±1.25exp±0.72rad)Hz. This value is consistent with the most precise evaluation in the literature and reduces its error by a factor of two.

Enhancement of mu ---> e gamma in the supersymmetric SU(5) GUT at large tan Beta

Branching ratio of