Measurement of the one-prong hadronic tau branching ratios at LEP

The branching ratios of the and decays have been measured using the 1991–1995 data recorded with the OPAL detector at LEP. These branching ratios are measured simultaneously using three selection criteria and are found to be where the first error is statistical and the second is systematic. Received: 4 December 1997 / Published online: 2 June 1998     

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     

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.     

Study Pure Annihilation Decays $B_s^0(\bar B_s^0)\rightarrow D^{\pm}\pi^{\mp}$ in PQCD Approach

The rare decays $B_s^0\rightarrow D^\pm \pi^\mp$ and $\bar B_s^0\rightarrow D^\mp \pi^\pm$ can occur only via annihilation-type diagrams in the standard model. In this paper, we calculate branching ratios of these decays in perturbative QCD approach ignoring soft final state interaction. From our calculation, we find that their branching ratios are at O(10^-6) with large CP asymmetry, which may be measured in LHC-b experiment in the future.     

Cabibbo-Suppressed Non-leptonic Decays of Ac and Final State Interaction

With the diquark structure of Ac, we investigate the branching ratio of Ac → nr and pro. The results show that without considering the final state interaction (FSI), the branching ratio of Ac → pπ0 is only of order 10-6 whereas this ratio could reach 10-4 and is at the same order as Ac → nr if taking into account the FSI effects. Concrete values depend on phenomenological parameters adopted in the calculations. These branching ratios can be measured in the experiments to come.     

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.     

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     

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     

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.     

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.     

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.     

A model of the formation of branched polymethyl methacrylates

A model of formation of macromolecules in the form of a crown of a tree was suggested to describe the character of branching and architecture of branched macromolecules synthesized by radical copolymerization of a monomer with a bifunctional monomer-branching agent in the presence of a chain transfer agent. The branch representing a polymer chain with included branching agent units was accepted as the main structural element of macromolecules. Model parameters were determined from the kinetic characteristics of copolymerization, such as reagent ratio and growth rate and chain transfer constants. Branching and architecture parameters of branched polymethyl methacrylates synthesized at various monomer: branching agent: chain transfer agent ratios were calculated     

Observation of the baryonic flavor-changing neutral current decay Λb(0)→Λμ+μ-

We report the first observation of the baryonic flavor-changing neutral current decay Λ(b)(0)→Λμ(+)μ(-) with 24 signal events and a statistical significance of 5.8 Gaussian standard deviations. This measurement uses a pp collisions data sample corresponding to 6.8 fb(-1) at √s = 1.96 TeV collected by the CDF II detector at the Tevatron collider. The total and differential branching ratios for Λ(b)(0)→Λμ(+)μ(-) are measured. We find B(Λ(b)(0)→Λμ(+)μ(-))=[1.73 ± 0.42(stat) ± (syst)] × 10(-6). We also report the first measurement of the differential branching ratio of B(s)(0)→?μ(+)μ(-), using 49 signal events. In addition, we report branching ratios for B(+)→K(+)μ(+)μ(-), B(0)→K(0)μ(+)μ(-), and B→K(*)(892)μ(+)μ(-) decays.     

Cabibbo-Suppressed Non-leptonic Decays of ∧c and Final State Interaction

With the diquark structure of ∧c, we investigate the branching ratio of ∧c→nπ^ and pπ^0. The results show that without considering the finM state interaction (FSI), the branching ratio of ∧c→pπ^0 is only of order 10^-6 whereas this ratio could reach 10^-4 and is at the same order as ∧c→nπ^ if taking into account the FSI effects. Concrete values depend on phenomenologicM parameters adopted in the calculations. These branching ratios can be measured in the experiments to come.     

Study of pure annihilation decays Bd,s→DOD-O

Within the heavy quark limit and the hierarchy approximation Λqcd << Md << Mb,we analyze the B→DOD-O and Bs→ DOD-O decays,which occur purely via annihilation type diagrams.As a rough estimate,we calculate their branching ratios and CP asymmetries in the perturbative QCD (PQCD) approach.The branching ratio of B→ DOD-O is about 3.8×10-5 that is just below the latest experimental upper limit.The branching ratio of Bs→ DOD-O is about 6.8 × 10-4,which could be measured in LHC-b.From the calculation,it is found that this branching ratio is not sensitive to the weak phase angle γ.In these two decay modes,there exist CP asymmetries because of the interference between weak and strong interaction.However,these asymmetries are too small to be measured easily.     

Branching ratios between correlated and uncorrelated two electron transitions into the K-shell of Al,Ca, Fe and Ni ions

The branching ratios between the radiative single and double electron transitions into the doubly ionized K-shell were measured as a function of the atomic number. The results are compared with various theoretical predictions.     

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     

Contribution of One-Photon Annihilation at ψ(2S) in e+e－ Experiment

The continuum one-photon annihilation at ψ(2S) in e⁺e^－ experiment is studied. Such contributions to the measured final states ωπ⁰ and π⁺π^－ at ψ(2S) mass are estimated by phenomenological models. It is found that these contributions must be taken into account in the determination of branching ratios of ψ(2S)→ωπ0 and ψ(2S)→π⁺π^－, as well as other electromagnetic decay modes. The study reaches the conclusion that in order to obtain the correct branching ratios on these decay modes at BES, at least 10pb^－1of data below the ψ(2S) peak is needed.     

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