Improved α4\alpha^4 Term of the Electron Anomalous Magnetic Moment

We report a new value of electron $g-2$, or $a_e$, from 891 Feynman diagrams of order $\alpha^4$. The FORTRAN codes of 373 diagrams containing closed electron loops have been verified by at least two independent formulations. For the remaining 518 diagrams, which have no closed lepton loop, verification by a second formulation is not yet attempted because of the enormous amount of additional work required. However, these integrals have structures that allow extensive cross-checking as well as detailed comparison with lower-order diagrams through the renormalization procedure. No algebraic error has been uncovered for them. The numerical evaluation of the entire $\alpha^4$ term by the integration routine VEGAS gives $-1.7283 (35) (\alpha/\pi)^4$, where the uncertainty is obtained by careful examination of error estimates by VEGAS. This leads to $a_e = 1 159 652 175.86 (0.10) (0.26) (8.48) \times 10^{-12}$, where the uncertainties come from the $\alpha^4$ term, the estimated uncertainty of $\alpha^5$ term, and the inverse fine structure constant, $\alpha^{-1} = 137.036 000 3 (10)$, measured by atom interferometry combined with a frequency comb technique, respectively. The inverse fine structure constant $\alpha^{-1} (a_e)$ derived from the theory and the Seattle measurement of $a_e$ is $137.035 998 83 (51)$.Comment: 64 pages and 10 figures. Eq.(16) is corrected. Comments are added after Eq.(40

Electroweak Fermion-loop Contributions to the Muon Anomalous Magnetic Moment

The two-loop electroweak corrections to the anomalous magnetic moment of the muon, generated by fermionic loops, are calculated. An interesting role of the top quark in the anomaly cancellation is observed. New corrections, including terms of order $G_\mu \alpha m_t^2$, are computed and a class of diagrams previously thought to vanish are found to be important. The total fermionic correction is $-(23\pm 3) \times 10^{-11}$ which decreases the electroweak effects on $g-2$, predicted from one-loop calculations, by 12\%. We give an updated theoretical prediction for $g-2$ of the muon.Comment: Corrected versio

Why do we need the new BNL muon g-2 experiment now?

New final results from the CMD-2 and SND e+e- annihilation experiments, together with radiative return measurements from BaBar, lead to recent improvements in the standard model prediction for the muon anomaly. The uncertainty at 0.48 ppm--a largely data-driven result--is now slightly below the experimental uncertainty of 0.54 ppm. The difference, a_mu(expt)- a_mu(SM) = (27.6 +/- 8.4) x 10^-10, represents a 3.3 standard deviation effect. At this level, it is one of the most compelling indicators of physics beyond the standard model and, at the very least, a major constraint for speculative new theories such as SUSY or extra dimensions. Others at this Workshop detailed further planned standard model theory improvements to a_mu. Here I outline how BNL E969 will achieve a factor of 2 or more reduction in the experimental uncertainty. The new experiment is based on a proven technique and track record. I argue that this work must be started now to have maximal impact on the interpretation of the new physics anticipated to be unearthed at the LHC.Comment: Invited Talk, Tau-06 Workshop, 10 pages, 5 figure

Angular momentum at null infinity in higher dimensions

We define the angular momentum at null infinity in higher dimensions. The asymptotic symmetry at null infinity becomes the Poincare group in higher dimensions. This fact implies that the angular momentum can be defined without any ambiguities such as supertranslation in four dimensions. Indeed we can show that the angular momentum in our definition is transformed covariantly with respect to the Poincare group.Comment: 13 page

MHD simulations of dense core collision

We investigated the effect of magnetic fields on the collision process between dense molecular cores. We performed three-dimensional magnetohydrodynamic simulations of collisions between two self-gravitating cores using the Enzo adaptive mesh refinement code. The core was modeled as a stable isothermal Bonnor-Ebert (BE) sphere immersed in uniform magnetic fields. Collisions were characterized by the offset parameter $b$, Mach number of the initial core $\mathcal{M}$, magnetic field strength $B_{0}$, and angle $\theta$ between the initial magnetic field and collision axis. For head-on ($b = 0$) collisions, one protostar was formed in the compressed layer. The higher the magnetic field strength, the lower the accretion rate. For models with $b = 0$ and $\theta = 90^{\circ}$, the accretion rate was more dependent on the initial magnetic field strength compared with $b = 0$ and $\theta = 0^{\circ}$ models. For off-center ($b = 1$) collisions, the higher specific angular momentum increased; therefore, the gas motion was complicated. In models with $b = 1$ and $\mathcal{M} = 1$, the number of protostars and gas motion highly depended on $B_{0}$ and $\theta$. For models with $b = 1$ and $\mathcal{M} = 3$, no significant shock-compressed layer was formed and star formation was not triggered.Comment: 20 pages, 18 figures, 3 tables. Accepted for publication in Ap

Unveiling the Dynamics of Dense Cores in Cluster-Forming Clumps: A 3D MHD Simulation Study of Angular Momentum and Magnetic Field Properties

We conducted isothermal MHD simulations with self-gravity to investigate the properties of dense cores in cluster-forming clumps. Two different setups were explored: a single rotating clump and colliding clumps. We focused on determining the extent to which the formed dense cores inherit the rotation and magnetic field of the parental clump. Our statistical analysis revealed that the alignment between the angular momentum of dense cores, $\bf{L}_{\rm core}$, and the rotational axis of the clump is influenced by the strength of turbulence and the simulation setup. In single rotating clumps, we found that $\bf{L}_{\rm core}$ tends to align with the clump's rotational axis if the initial turbulence is weak. However, in colliding clumps, this alignment does not occur, regardless of the initial turbulence strength. This misalignment in colliding clumps is due to the induced turbulence from the collision and the isotropic gas inflow into dense cores. Our analysis of colliding clumps also revealed that the magnetic field globally bends along the shock-compressed layer, and the mean magnetic field of dense cores, $\bf{B}_{\rm core}$, aligns with it. Both in single rotating clumps and colliding clumps, we found that the angle between $\bf{B}_{\rm core}$ and $\bf{L}_{\rm core}$ is generally random, regardless of the clump properties. We also analyzed the dynamical states of the formed cores and found a higher proportion of unbound cores in colliding clumps. In addition, the contribution of rotational energy was only approximately 5% of the gravitational energy, regardless of the model parameters for both single and colliding cases.Comment: 28 pages, 25 figures, 3 tables. Accepted for publication in Ap

The 10 to the 8th power bit solid state spacecraft data recorder

The results are summarized of a program to demonstrate the feasibility of Bubble Domain Memory Technology as a mass memory medium for spacecraft applications. The design, fabrication and test of a partially populated 10 to the 8th power Bit Data Recorder using 100 Kbit serial bubble memory chips is described. Design tradeoffs, design approach and performance are discussed. This effort resulted in a 10 to the 8th power bit recorder with a volume of 858.6 cu in and a weight of 47.2 pounds. The recorder is plug reconfigurable, having the capability of operating as one, two or four independent serial channel recorders or as a single sixteen bit byte parallel input recorder. Data rates up to 1.2 Mb/s in a serial mode and 2.4 Mb/s in a parallel mode may be supported. Fabrication and test of the recorder demonstrated the basic feasibility of Bubble Domain Memory technology for such applications. Test results indicate the need for improvement in memory element operating temperature range and detector performance

O(\alpha^2 \ln(m_\mu/m_e)) Corrections to Electron Energy Spectrum in Muon Decay

O(\alpha^2 \ln(m_\mu/m_e)) corrections to electron energy spectrum in muon decay are computed using perturbative fragmentation function approach. The magnitude of these corrections is comparable to anticipated precision of the TWIST experiment at TRIUMF where Michel parameters will be extracted from the measurement of the electron energy spectrum in muon decay.Comment: 8 pages, LaTeX, revtex4.cls, 1 PostScript figur

High Order QED Corrections in Physics of Positronium

High-order perturbative corrections to positronium decays and hyperfine splitting are briefly reviewed. Theoretical predictions are compared to the most recent experimental data. Perspectives of future calculations are discussed.Comment: 8 pages, LaTeX, talk given at Workshop on Positronium Physics, ETH Honggerberg, Zurich, May 30-31, 2003, a misprint in Eq. (1) correcte