Measurement of tau branching ratios to five charged hadrons

The branching ratios of the decay of the lepton to five charged hadrons have been measured with the OPAL detector at LEP using data collected between 1991 and 1995 at centre-of-mass energies close to the resonance. The branching ratios are measured to be where the first error is statistical and the second systematic. Received: 4 June 1998 / Published online: 11 March 1999     

Photoelectron branching ratios and partial ionization cross-sections for CO and N2 in the energy range 18–50 eV

Branching ratios for photoionization to various ion states of CO and N₂ have been measured in the energy range 18–50 eV using an electron—electron coincidence technique at an ejected electron angle of 90°. The branching ratios, which show a marked variation with energy are shown to be in good agreement with the results of conventional photoelectron spectroscopy at those energies where quantitative PES measurements have been made. The results indicate that the effect of the assymmetry parameter, β, is relatively insignificant in the case of CO and N₂. Partial oscillator strengths have been determined from the branching ratios using recent total photoabsorption data. In addition to the expected one electron ion states, others are observed arising from two electron processes and the variation of these cross-sections with energy loss is also reported.     

Branching ratios of successive emission (up to three) of C2n + (n = 1–5) fragments in asymmetrical fission processes of C60 r+ ions (r = 4–6)

Highly charged C₆₀ molecules are produced in collisions between neutral C₆₀ and multiply charged ions within a large range of temperatures. Successive emission of one, two or three light monocharged fragments referred as one-, two- and three-step processes have been observed. The experimental mass branching ratios for the emission of one C_2n⁺ fragment from C₆₀⁶⁺, C₆₀⁵⁺ and C₆₀⁴⁺ ions are compared with the theoretical values using a statistical model. From hotter C₆₀⁶⁺ ions, branching ratios for three-step processes have been measured and the data are in good agreement with an estimation using the branching ratios in one-step process.     

J/Ψ and Ψ′ production in hadronic Z0 decays

The production of Jψ mesons in Z⁰ decays is studied using 3.6 million hadronic events recorded by the OPAL detector at LEP. The inclusive Z⁰ to Jψ and b-quark to Jψ branching ratios are measured from the total yield of Jψ mesons, identified from their decays into lepton pairs. The Jψ momentum distribution is used to study the fragmentation of b-quarks. The production rate of ψ′ mesons, identified from their decays into a Jψ and a π⁺π^? pair, is measured as well. The following results are obtained: ${Br(Z^{0}?ghtarrow {? J}/?i X)=(3.9pm 0.2pm 0.3)cdot 10^{-3} {? and} ?op Br(Z^0?ghtarrow ?i ^?ime X)=(1.6pm 0.3pm 0.2)cdot 10^{-3}, }$ where the first error is statistical and the second systematic. Finally the Jψ sample is used to reconstruct exclusive b-hadron decays and calculate the corresponding b-hadron branching ratios and masses.     

B\to \pi \rho, \pi \omega decays in perturbative QCD approach

We calculate the branching ratios and CP-asymmetries for , and decays, in the perturbative QCD approach. In this approach, we calculate non-factorizable and annihilation type contributions, in addition to the usual factorizable contributions. Our result is in agreement with the branching ratio of , measured by the CLEO and BABAR collaborations. We also predict large CP-asymmetries in these decays. These channels are useful to determine the CKM angle . Received: 5 November 2001 / Published online: 8 February 2002     

Charmless Hadronic Decays B→VV in the Topcolor－Assisted Technicolor Model

Based on the effective Hamiltonian with the generalized factorization approach, we calculate the branching ratios and CP asymmetries of B→VV decays in the Topcolor-assisted Technicolor (TC2) model. Within the considered parameter space we find that: (a) for the penguin-dominated B→K^*+φ and K^*0φ decays, the new physics enhancements to the branching ratios are around 40%; (b) the measured branching ratios of B→K^*+φ and K^*0φ decays prefer the range of 3≤N_c^eff≤5; (c) the SM and TC2 model predictions for the branching ratio B(B⁺→ρ⁺ρ⁰) are only about half of the Belle's measurement; and (d) for most B→VV decays, the new physics corrections on their CP asymmetries are generally small or moderate in magnitude and insensitive to the variation of m_π and N_c^eff.     

K\rightarrow \pi\pi e^+e^- decays and chiral low-energy constants

The branching ratios of the measured decay and of the still unmeasured decay are calculated to next-to-leading order in chiral perturbation theory (CHPT). Recent experimental results are used to determine two possible values of the combination of weak low-energy couplings (LECs) from the chiral Lagrangian. The values obtained are compared to the predictions of theoretical approaches to weak counterterm couplings to distinguish between the two values. Using the favoured value of the combination and taking into account additional assumptions suggested by the considered models, one obtains the branching ratio of the second decay as a function of the unknown combination of weak low-energy couplings. Finally, using values of the individual LECs derived from a particular model, one predicts the branching ratio of the decay. Received: 27 February 2001 / Published online: 11 May 2001     

Radiative lifetimes,branching ratios and absolute transition probabilities of atomic uranium by delayed photoionization measurements

Radiative lifetimes of ten even-parity energy levels of atomic uranium in the 15,500–19,000 cm^?1 region and branching ratios of six transitions originating either from ground level (⁵L ₆ ^o ) or from lowest metastable level (⁵K ₅ ^o ) at 620.32 cm^?1 are measured employing three-step delayed photoionization technique. The lifetimes of five energy levels and branching ratios of five transitions are measured for the first time. By combining the experimentally measured values of radiative lifetimes and branching ratios, we have determined the absolute transition probabilities of six transitions of uranium and compared with those previously reported in the literature.     

Measurement of the Michel parameters in leptonic tau decays

The Michel parameters of the leptonic decays are measured using the OPAL detector at LEP. The parameters , , (with ) and are extracted from the energy spectra of the charged decay leptons and from their energy–energy correlations. A new method involving a global likelihood fit of Monte Carlo generated events with complete detector simulation and background treatment has been applied to the data recorded at center-of-mass energies close to corresponding to an integrated luminosity of 155 pb. If e- universality is assumed and inferring the polarization from neutral current data, the measured Michel parameters are: where the value of has been constrained using the published OPAL measurements of the leptonic branching ratios and the lifetime. Limits on non-standard coupling constants and on the masses of new gauge bosons are obtained. The results are in agreement with the V–A prediction of the Standard Model. Received: 25 June 1998 / Published online: 1 March 1999     

K^0_S production in \tau decays

From a sample of about 160k candidates collected with the ALEPH detector at LEP between 1991 and 1995, lepton decays involving are studied. The associated production in decays is also investigated. The branching ratios are measured for the inclusive decay , where can be anything, and for the exclusive decays The decay is studied for the first time, giving a branching ratio The channels , , , , and are also investigated. In addition, mass spectra in the and final states are analysed to provide information on the intermediate states produced in the decays. Received: 6 January 1998 / Published online: 15 May 1998     

New approaches to assign configurations using low-statistic γ-ray spectra

Analytical methods to deduce single particle configurations from g _K factors using branching ratios in rotational bands, especially in low-statistic cases for heavy nuclei, will be presented. Two methods utilising ??-ray branching ratios in rotational bands and also intensities in the K X-ray region of spectra are shown and results from these are given.     

α-decay Branching Ratios to Rotational Band of Heavy Even-even and Odd-A Nuclei

By using a simple barrier penetration approach,we predict the α-decay branching ratios to members of ground-state rotational band of heavy even-even No isotopes.We also extend our approach to calculate the α-decay branching ratios to the rotational band of heavy odd-A nuclei.The theoretical branching ratios of α-decays are found in good agreement with the available experimental data.     

Relative transition probabilities in the A-X system of OD

As in a previous study on the OH molecule, branching ratios for emission from v′ = 0, 1 and 2 of the A²Σ⁺ state of OD have been measured using frequency-doubled, tunable dye laser excitation. The six independent ratios so obtained are used to assess calculations incorporating an electronic transition moment varying linearly with internuclear distance, a form judged superior from the OH work. Calculations of the rotational dependence of the transition probabilities in OD, and comments on some recent OH investigations are included.     

Probing γWW couplings through radiative W-decays

We investigate the possibilities of probing γWW couplings through W → γff′ by computing the branching ratios for various polarization channels of W and γ, allowing for the most general γWW couplings. The bounds on the possible deviations of γWW couplings from their standard model values can be improved if the branching ratios for the decays of W's with positive and negative helicities can be separately measured.     

Identifying Tau Hadronic Decay with Neural Network

The identification of tau one prong hadronic decay using neural network is presented.Based on the identification,we measured the branching ratios: Br(π/Kv)=(12.18±0.26±0.42)%,Br(π/Kπ⁰v)=(25.20±0.35±0.50)%,Br(π/K2π⁰v)=(8.88±0.37±0.38)%,Br(π/K3π⁰v)=(1.70±0.24±0.39)%.     

Some lifetimes and transition probabilities in Cu(I)

Radiative lifetimes of 7 levels in the Cu(I) 3d⁹ 4s4p configuration have been measured using a delayed coincidence technique; copper vapor was excited in an argon buffer gas and cross sections for collisional destruction of copper levels by argon were also obtained. Transition probabilities of the lines originating from these levels have been determined using the measured lifetimes and branching ratios.     

On discrepancies within the experimental and theoretical low energy3H(α, γ)7Li cross sections

The two presently available measurements of the low-energy³H(α, γ)⁷Li reaction differ from each other by roughly 30% in total magnitude as well as in their determination of the branching ratios for the transition into the two final⁷Li bound states. Studying the³H(α, γ)⁷Li reaction in the framework of the microscopic Resonating Group Method we were able to reproduce both experimental total cross sections using different effective nucleon-nucleon interactions. However, none of the effective forces yields branching ratios compatible with the data measured by the Toronto-Münster-collaboration.     

Branching ratio and angular distribution of ejected electrons from Eu 4f~76p_(1/2)nd auto-ionizing states

The branching ratios of ions and the angular distributions of electrons ejected from the Eu 4f~76p_(1/2)nd auto-ionizing states are investigated with the velocity-map-imaging technique.To populate the above auto-ionizing states,the relevant bound Rydberg states have to be detected first.Two new bound Rydberg states are identified in the region between41150 cm~(-1)and 44580 cm~(-1),from which auto-ionization spectra of the Eu 4f~76p_(1/2)nd states are observed with isolated core excitation method.With all preparations above,the branching ratios from the above auto-ionizing states to different final ionic states and the angular distributions of electrons ejected from these processes are measured systematically.Energy dependence of branching ratios and anisotropy parameters within the auto-ionization spectra are carefully analyzed,followed by a qualitative interpretation.     

Lifetime measurements in166Er

The lifetimes of five states in the ground band, from spin 6⁺ up to spin 14⁺, and of all even states in the gamma band up to spin 12⁺, have been measured in¹⁶⁶Er using the recoil distance method. The reduced electric quadrupole transition probabilities have been determined from the measured lifetimes using previously measured branching ratios, and the mixing between the ground band and theγ-band has been studied. The transitional electric quadrupole moments for the ground band and theγ-band have been deduced and are discussed.     

Spectroscopic analysis and laser parameters of Nd3+ in Ca3Sc2Ge3O12 garnet crystals

3 Sc₂Ge₃O₁₂ (CaSGG) single crystals with the garnet structure have been grown by means of the flux growth technique. The doping with Nd³⁺ and Mg²⁺ (as charge compensator) yields samples suitable for optical spectroscopy experiments. The absorption and emission properties have been measured at temperatures ranging from 10 to 298 K. The emission spectra give evidence of the presence of non-equivalent Nd³⁺ sites. The decay time of the 1.06-μm emission band has been measured as a function of temperature and incident power. The intensities of the 298 K absorption transitions have been analyzed by means of the Judd–Ofelt theory. The radiative lifetimes, the branching ratios (β), and the spontaneous emission probabilities have been evaluated for the ⁴F_3/2 excited state using the calculated intensity parameters. The stimulated-emission cross sections and the branching ratios have been estimated from the experimental data for the most important laser transitions indicating that this crystal can be considered an interesting material for solid-state laser applications. Received: 2 June 1998 / Revised version: 28 October 1998 / Published online: 24 February 1999