Calculation of Decay μ → eγ in R ξ Gauge in a Model of Electroweak-Scale Right-Handed Neutrinos

The lepton flavor violating process μ - eγ has been previously studied in a model of electroweak-scale right-handed neutrinos. In that work the decay amplitude was computed in unitarity gauge, augmented by some technical considerations that correct the leading term thus obtained. This complication arises because the mixing matrices appearing in the weak charged currents are not unitary in the model. In this paper, we recalculate the amplitude in Re gauge. The cancellation of the ξ dependence in the final result serves as a useful check to both the obtained amplitude and the technical points made in the previous work.     

Nonequilibrium fluctuations in μ space

The properties of fluctuations in space in or outside thermal equilibrium are obtained by solving hierarchies of equations derived either from the Liouville or the Master equation. In particular we study the one-, two-, etc., time correlation functions that describe the spatial and temporal behavior of the fluctuations in space. Explicit solutions are obtained for a dilute gas. The Langevin approach is briefly discussed. Our results are compared with those obtained in the extensive literature, which is reviewed in some detail.     

Insights on d μ t sticking from d μ d stripping and μ,3He capture

Data from the recent PSI high statistics experiment on d μ d fusion are used to measure the stripping process in d μ d→ n+μ,³He and test current calculations of the stripping process. The PSI results in μ³He capture are also used to remove a troubling background from this measurement. Combination of these results with the old dμ t sticking analysis slightly raise and improve that result to ω_s= (0.58± 0.04)% and indicate that theory and experiment can meet if theoretical stripping is increased only at the beginning of the track. This conclusion is in accord with the new stripping calculations where excited state stripping is increased significantly. This revised version was published online in August 2006 with corrections to the Cover Date.     

A simple geometric representative for μ of a point

ForSU(2) (orSO(3)) Donaldson theory on a 4-manifoldX, we construct a simple geometric representative for of a point. Letp be a generic point inX. Then the set {[A]F _A ^– (p) is reducible}, with coefficient –1/4 and appropriate orientation, is our desired geometric representative. The construction is an exercise in real algebraic geometry in the style of Ehresmann and Pontryagin.This work is partially supported by an NSF Mathematical Sciences Postdoctoral Fellowship and Texas Advanced Research Project grant ARP-037.     

Application of μ SR to radiation damage in metals

Proton-irradiated Al, Cu and Ni foils have been investigated by the SR technique. No trapping of ⁺ has been observed in the temperature range investigated (<300 K). In Ni a temperature-independent increase of the depolarisation rate by a factor of three is found for the irradiated target. This change is attributed to field inhomogeneities produced by defects.     

The Z → c \bar c → γγ*, Z → b \bar b → γγ* triangle diagrams and the Z → γψ, Z → γϒ decays

The approach to the Z → γψ and Z → γ? decay study is presented in detail, based on the sum rules for the Z → c $ \bar c $ → γγ* and Z → b $ \bar b $ → γγ* amplitudes and their derivatives. The branching ratios of the Z → γψ and Z → γ? decays are calculated for different hypotheses on saturation of the sum rules. The lower bounds of Σ _ψ BR(Z → γψ) = 1.95 × 10^?7 and Σ_υ BR(Z → γ?) = 7.23 × 10^?7 are found. Deviations from the lower bounds are discussed, including the possibility of BR(Z → γJ/ψ(1S)) ～ BR(Z → γ?(1S)) ～ 10^?6, that could be probably measured in LHC. The angular distributions in the Z → γψ and Z → γ? decays are also calculated.     

Phase Transformations α → β → γ → δ → ε in Titanium Hydride TiH x with Increase in Hydrogen Concentration

Structural phase transformations of the hcp bcc fct fcc fct ( ) type in titanium hydrides TiH _x experimentally found to occur with increase in the hydrogen concentration x are studied theoretically. Free energy phases are statistically calculated, and their concentration dependence is determined. Phase transformation temperatures are found from intersection points of free energy curves and from points of common tangents to the curves. The energy parameters of the system are estimated. The calculation results are compared with the experimental data.     

Cutoff effects in lattice actions at μ ≠ 0

We look at the cutoff dependence of several lattice actions, including two improved actions viz. Naik and p4, and and chirally-invariant ones, namely fixed-point, overlap and domain-wall, with the aim of understanding its behavior at μ ≠ 0. Apart from numerical results, we also derive a series expansion in N _r ⁻¹ for the free-gas pressure. We find that actions with O(a ⁿ )-improved rotational invariance produce O(a ⁿ )-improvement in the pressure. The series for unimproved overlap and domain-wall fermions are identical to the naive series, and hence using Naik or p 4 kernels should produce improvement in these formulations as well. Lastly, we find that actions that are improved at μ = 0 remain so as the chemical potential is turned on. The series coefficients become μ-dependent now, however their functional form at any given order is the same for all actions.     

Decay of Nd140→Pr140→Ce140

An intermediate image magnetic spectrometer was used to study the continuous ⁺-spectrum of Pr¹⁴⁰ and the Auger electrons of the decay chain Nd¹⁴⁰Pr¹⁴⁰Ce¹⁴⁰. The maximum energy of the continuous ⁺-spectrum is 2318±10 keV. The ratio of the intensities of the different Auger groupsK–LLK–LXK–MX=1 (0.58±0.05) (0.09±0.02). The ratio of the number of Auger electrons of the K-series to the electrons of the continuous spectrume _K/ ⁺ is 0.292.

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Nd¹⁴⁰Pr¹⁴⁰Ce¹⁴⁰

Pr¹⁴⁰ Nd¹⁴⁰ Pr¹⁴⁰¹⁴⁰. ⁺- — 2318±10 keV. -:K–LLK–LXK–MX=1(0,58±0,05) (0,09±0,02). K e _K/ ⁺=0,292.

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We should like to thank Z. Macháek and Z. Dubcová for help in the measurements and J. Vlachý, graduate of the Faculty of Technical and Nuclear Physics, for help in the measurements and elaboration of the experimental results.     

β-tin→Imma→sh phase transitions of germanium

New paths were designed for the investigations of the β-tin→Imma→sh phase transitions in nanocrystalline Ge under conditions of hydrostatic stress. A second-order transition between the β-tin and Imma phases was identified at 66 GPa, and a first-order transition between the Imma and sh phases was determined at 90 GPa. Superconductivity was obtained up to 190 GPa using the acquired structural data in first-principles calculations. This provides evidence that the standard electron-phonon coupling mechanism is responsible for superconductivity in Ge, as evidenced by the good agreement between the calculations and existing experiments.     

Alpha-decay branching ratios to high-lying excited-states of the 242Cm→238pu→ 234U →230Th→226Rn decay chain

We present a systematic calculation on the 0c-decay branching ratios to excited-states of an even-even α-decay chain 242Cm→238pu→234U →230Th→226Rn by the improved barrier penetration approach. The changes of the parities between the parent nuclei and the daughter nuclei are properly taken into account. The theoretical values are compared with the available experimental data and the deviation between them is within a factor of 5 in most cases.     

Inelastic final-state interactions in B → VV →π K processes

We study the final-state interactions in B →π K decays through B → VV →π K processes where the inelastic rescattering occurs via single pion exchange. The next-to-leading order low-energy effective Hamiltonian and Bauer-Stech-Wirbel (BSW) model are used to evaluate the weak transition matrix elements and final-state interactions. We found that the final-state interaction effects in B →ρ K^*→π K processes are significant. The Fleischer-Mannel relation for the Cabibbo-Kobayashi-Maskawa (CKM) angle γ can be significantly modified. Received: 13 August 1998     

New polymorphs of alumina: Part II μ and λ alumina

Abstract

We had reported observation of polymorphs of alumina having rare earth sesquioxide type structures in xerogel γ alumina (XGA) at high pressures and temperatures (High Pressure Research, 1998). In this paper we report observation of two additional phases at somewhat different pressures and temperatures. The XGA quenched from 5.2 GPa and 1450°C showed, besides α Al₂O₃, a new hexagonal metastable polymorph μAl₂O₃. Over a period of 10 to 12 weeks μ A1₂O₃ transforms to a stable hexagonal phase λ Al₂O₃. The cell parameters of λ Al₂O₃ are comparable with those of k Al₂O₃ found by Saalfield on dehydration of gibbsite A1₂O₃3H₂O in air at 800°C. The XGA containing 1 wt% of Cr₂O₃ yielded similar results at 4.56GPa and 1100°C. Further the XGA containing Cr showed complete transformation to n Al₂O₃ at 5.2 GPa and 1520°C.     

Measurement of the μ decay spectrum with the ICARUS liquid Argon TPC

Examples are given which prove the ICARUS detector quality through relevant physics measurements. We study the decay energy spectrum from a sample of stopping events acquired during the test run of the ICARUS T600 detector. This detector allows the spatial reconstruction of the events with fine granularity, hence, the precise measurement of the range and dE/dx of the with high sampling rate. This information is used to compute the calibration factors needed for the full calorimetric reconstruction of the events. The Michel parameter is then measured by comparison of the experimental and Monte Carlo simulated decay spectra, obtaining . The energy resolution for electrons below MeV is finally extracted from the simulated sample, obtaining .Received: 20 November 2003, Published online: 4 February 2004     

QCD corrections to b→sγγ and exclusive Bs→γγ decay

The short distance QCD corrections to b→sγγ are calculated in the leading logarithmic approximation. The equivalence of operator basis reduction for S-matrix elements by using the equations of motion or by proving a low energy theorem is discussed. We apply the above results to the exclusive B_s→γγ decay. The branching ratio of this decay is found to be 5×10⁻⁷ in the Standard Model. We also found that QCD corrections modify considerably the ratio between CP-even and CP-odd two-photon amplitudes.     

μ → <Emphasis Type="Italic">e</Emphasis>γ decay versus the μ → <Emphasis Type="Italic">eee</Emphasis> bound and lepton flavor violating processes in supernova

Even tiny lepton flavor violation (LFV) due to some New Physics is able to alter the conditions inside a collapsing supernova core and probably to facilitate the explosion. LFV emerges naturally in a see-saw type-II model of neutrino mass generation. Experimentally, the LFV beyond the Standard Model is constrained by rare lepton decay searches. In particular, strong bounds are imposed on the μ → eee branching ratio and on the μ-e conversion in muonic gold. Currently, the μ→eγ is under investigation in the MEG experiment that aims at a dramatic increase in sensitivity in the next three years. We seek a see-saw type-II LFV pattern that fits all the experimental constraints, leads to Br(μ →eγ) ≳ Br(μμ →eee), and ensures a rate of LFV processes in supernova high enough to modify the supernova physics. These requirements are sufficient to eliminate almost all freedom in the model. In particular, they lead to the prediction 0.4 × 10⁻¹² ≲ Br(μ → eγ) ≲ 6 × 10⁻¹², which will be testable by MEG in the nearest future. The considered scenario also constrains the neutrino mass-mixing pattern and provides lower and upper bounds on τ-lepton LFV decays. We also briefly discuss a model with a single bilepton in which the μ → eee decay is absent at the tree level.     

Alpha-decay branching ratios to high-lying excited-states of the ^242Cm → ^238Pu → ^234U → ^230Th → ^226Rn decay chain

We present a systematic calculation on the α-decay branching ratios to excited-states of an even-even α-decay chain ^242Cm → ^238Pu → ^234U → ^230Th → ^226Rn by the improved barrier penetration approach. The changes of the parities between the parent nuclei and the daughter nuclei are properly taken into account. The theoretical values are compared with the available experimental data and the deviation between them is within a factor of 5 in most cases.     

Effects of charged Higgs bosons on the processes b→sγ, b→sg1 and b→sℓ+ℓ−

Effects of charged Higgs bosons (H⁺) on various loop-induced processes in the B-meson system are discussed, within the framework of two Higgs doublet models (2HDMs). The H⁺ contribution to the magnetic moment form factor turns out to be very significant and it can distinguish between the two types of 2HDMs. Even with constraints from B_d mixing, both strong enhancements or strong suppressions (in b→sγ) of decay rates are possible. Thus, information from these modes is competitive with, and may soon surpass, restrictions on 2HDMs from B_d mixing. Since (inclusive) b→sγ and b→sg¹ at current limits are not excluded, continued effort to detect them is encouraged.