High Branching Ratio Research Articles

Non-statistical decay and α-correlations in the 12C+12C fusion–evaporation reaction at 95 MeV

Multiple alpha coincidences and correlations are studied in the reaction 12C+12C at 95 MeV for fusion–evaporation events completely detected in charge. Two specific channels with carbon and oxygen residues in coincidence with α −particles are addressed, which are associated with anomalously high branching ratios with respect to the predictions of Hauser–Feshbach calculations. Triple alpha emission appears kinematically compatible with a sequential emission from a highly excited Mg. The phase space distribution of α − α coincidences suggests a correlated emission from a Mg compound, leaving an oxygen residue excited above the threshold for neutron decay. These observations indicate a preferential α emission of 24Mg at excitation energies well above the threshold for 6 − α decay.

Enhanced 2.7 μm emission from Er3+ doped oxyfluoride tellurite glasses for a diode-pump mid-infrared laser

The influence of fluoride and shielding gas (O2 or Ar) on the physical and spectroscopic properties of Er3+ doped TeO2-ZnO-ZnF2 glass system is investigated. The larger electronegativity of F than O accounts for the gradual decrease of refractive index, density, and J-O parameters with increasing ZnF2. An analysis on Fourier transform infrared transmission spectra reveals that the absorption coefficient of OH− around 3 μm as low as 0.247 cm−1 can be achieved when 30 mol% ZnF2 containing sample is treated with Ar gas during glass melting process. The reduction of OH− groups combined with the low multiphonon relaxation rate (207 s−1) contributes to the enhanced emissions at 1.5 and 2.7 μm, along with prolonged lifetimes of 4I11/2 and 4I13/2 levels. A high branching ratio (17.95%) corresponding to the Er3+: 4I11/2 → 4I13/2 transition, the large absorption and emission cross section (0.44 × 10−20 cm2 and 0.45 × 10−20 cm2), and good gain cross section demonstrate that oxyfluoride tellurite glass could be a promising material for a diode-pump 2.7 μm fiber laser.

Role of shape and quadrupole deformation of parents in the cluster emission of rare earth nuclei

The nuclear structure effects on α decay and cluster emission are investigated in the case of even–even rare earth nuclei150–160Dy ,150–160Er ,150–160Yb ,158,162,166–176Hf ,160,164–178W and162,166,170–180Os . The role of shape and deformation of parent nuclei in the decay rate is studied by taking the Coulomb and proximity potentials as the interacting barrier for the post scission configuration. The quadrupole deformation of parent nuclei causes a slight change in the half-life of α emissions, but it affects the rate of heavy cluster emissions significantly. Prolate deformation of parents enhances cluster emission, while an oblate deformation slows down the decay. Shape and deformation of parent nuclei causes change in the branching ratio also. A prolate deformation increases the branching ratio, whereas an oblate deformation reduces it. Highest branching ratio is predicted at N ~ 90.

NonleptonicBc→VVdecays

We study the exclusive nonleptonic ${B}_{c}\ensuremath{\rightarrow}VV$ decays, within the factorization approximation, in the framework of the relativistic independent quark model, based on a confining potential in the scalar-vector harmonic form. The weak form factors are extracted from the overlap integral of meson wave functions derived in the relativistic independent quark model. The predicted branching ratios for different ${B}_{c}$-meson decays are obtained in a wide range, from a tiny value of $\mathcal{O}({10}^{\ensuremath{-}6})$ for ${B}_{c}\ensuremath{\rightarrow}{D}^{*}{D}_{(s)}^{*}$ to a large value of 24.32% for ${B}_{c}\ensuremath{\rightarrow}{B}_{s}^{*}{\ensuremath{\rho}}^{\ensuremath{-}}$, in general agreement with other dynamical-quark-model predictions. The decay modes ${B}_{c}\ensuremath{\rightarrow}{B}_{s}^{*}{\ensuremath{\rho}}^{\ensuremath{-}}$ and ${B}_{c}\ensuremath{\rightarrow}{B}^{*}{\ensuremath{\rho}}^{\ensuremath{-}}$ with high branching ratios of 24.32% and 1.73%, respectively, obtained in this model should be detectable at the LHC and Tevatron in the near future. The $b\ensuremath{\rightarrow}c$, $u$ induced decays are predicted predominantly in the longitudinal mode, whereas the $\overline{c}\ensuremath{\rightarrow}\overline{s}$, $\overline{d}$ induced decays are obtained in a slightly higher transverse mode. The $CP$-odd fractions $({R}_{\ensuremath{\perp}})$ for different decay modes are predicted and those for color-favored ${B}_{c}\ensuremath{\rightarrow}{D}^{*}{D}^{*}$, ${D}^{*}{D}_{s}^{*}$ decays indicate significant $CP$ violation in this sector.

Visible luminescence characteristics of Sm3+ doped Zinc Alumino Bismuth Borate glasses

Zinc Alumino Bismuth Borate (ZnAlBiB) glasses at different compositions doped with 1mol% of Sm3+ ions were prepared by using the melt quenching technique and investigated by XRD, optical absorption, emission and decay curve analysis to understand the visible luminescence of these glasses. From the absorption spectra the JO parameters are evaluated and are used to calculate the radiative properties such as transition probability, radiative lifetime, branching ratio and absorption cross-sections for various fluorescent levels of Sm3+ ions. The emission spectra of Sm3+ ions doped ZnAlBiB glasses show two intense emission bands 4G5/2→6H7/2 (orange) and 4G5/2→6H9/2 (red) for which the stimulated emission cross-section and branching ratios are evaluated to understand the potentiality of these materials as visible lasers. The decay profiles for the 4G5/2 fluorescent level of Sm3+ doped ZnAlBiB glasses have been recorded to measure the quantum efficiency (η) of these glasses. The strong visible emissions, large stimulated emission cross-sections, high branching ratios and good quantum efficiencies observed for the present ZnAlBiB glasses suggest the suitability of these glasses as laser and photonic devices operating in visible region.

REACTIONS FORMING C$_{n=2,10}^{(0,+)}$, Cn= 2, 4H(0, +), AND C3H$_2^{(0,+)}$ IN THE GAS PHASE: SEMIEMPIRICAL BRANCHING RATIOS

The aim of this paper is to provide a new set of branching ratios (BRs) for interstellar and planetary chemical networks based on a semiempirical model. We applied, instead of zero-order theory (i.e., only the most exoergic decaying channel is considered), a statistical microcanonical model based on the construction of breakdown curves and using experimental high velocity collision BRs for their parameterization. We applied the model to ion–molecule, neutral–neutral, and ion–pair reactions implemented in the few popular databases for astrochemistry, such as KIDA, OSU, and UMIST. We studied the reactions of carbon and hydrocarbon species with electrons, He+, H+, CH+, CH, C, and C+ leading to intermediate complexes of the type Cn = 2, 10, Cn = 2, 4H, C3H2, C, Cn = 2, 4H+, or C3H. Comparison of predictions with measurements supports the validity of the model. Huge deviations with respect to database values are often obtained. Effects of the new BRs in time-dependent chemistry for dark clouds and for photodissociation region chemistry with conditions similar to those found in the Horsehead Nebula are discussed.

Optical and radiative properties of Nd3+-doped lead tellurite borate glasses

Glass samples of composition (in mol%) 20PbO-20TeO2-(60 – x)B2O3-xNd2O3 (x = 0, 1, 2, 3, 4) were prepared by melt quenching. The glassy nature of as-quenched samples was established via differential scanning calorimetry. The amorphous nature of the glasses was confirmed via powder X-ray diffraction measurements. Judd–Ofelt (JO) analysis based on UV–visible absorption spectra was performed to determine JO parameters Ωλ (λ = 2, 4, 6). The observed trend is Ω2 > Ω6 > Ω4. The large value of Ω2 indicates the presence of covalent bonding between the Nd3+ ions and the surrounding ligands. Radiative properties, such as radiative transition probabilities, branching ratios, and radiative lifetimes are estimated. The glass samples have relatively high branching ratio, and their emission (Aem) to excited state absorption (AESA) intensity ratio is higher than one for the 4F3/2 → 4I11/2 transition, indicating that the prepared glasses may have potential laser applications.

Effect of Fluorine Ions on 2.7 μm Emission in Er3+/Nd3+-Codoped Fluorotellurite Glass

The 2.7 μm emission properties of Er(3+)/Nd(3+)-codoped fluorotellurite glasses were investigated in the present work. The thermal stability, refractive index, absorption and transmission spectra, and emission spectra were measured and investigated. The 2.7 μm emission in Er(3+)/Nd(3+)-codoped fluorotellurite glasses was enhanced with the increase of fluorine ions. The Judd-Ofelt analysis based on absorption spectra was performed in order to determine the Judd-Ofelt intensity parameters Ωt (t = 2, 4, 6), spontaneous emission probability, radiative lifetime and branching ratios of Er(3+):(4)I(11/2) → (4)I(13/2) transition. It is found that the Er(3+)/Nd(3+)-codoped fluorotellurite glass possesses a lower spontaneous transition probability A (58.95 s(-1)) but a higher branching ratio β (15.72%) corresponding to the stimulated emission of Er(3+):(4)I(11/2) → (4)I(13/2) transition. Additionally, the transmittance was also tested and reached a maximum when the molar concentration of ZnF(2) is 15%. The presence of fluorine ions greatly decreases the population of OH(-) groups, which affects the 2.7 μm emission effectively by means of decreasing the rate of energy transfer to impurities (e.g., OH(-) groups).

Nano-Odontology: Nanostructured Assemblies for Endodontic Regeneration

The vitality of the pulp is so fundamental to the functional life of the tooth that new strategies are required to avoid the removal of the whole pulp following irreversible pulpitis and to regenerate the lost endodontic tissues. Nano-odontology would provide suitable solutions for pulp tissue conservative and regenerative approaches. In our group, we have shown that when covalently coupled to Poly-Glutamic Acid (PGA) the incorporation of an anti-inflammatory hormone (melanocortin, a-MSH) into the multilayered films Poly-L-Lysine (PLL)/PGA increases the anti-inflammatory reaction of pulp fibroblasts and macrophages stimulated by LPS (Lipo-Polysaccharides). Recently, usual linear PLL polymers have been chemically grafted for making new Dendrigraft polymers (DGLG4) whose higher branching ratios can give useful properties. The objective is to use nanostructured assemblies containing DGLG4 and PGA-alpha-MSH to design a new nanomaterial. These nanostructured assemblies (DGLG4-PGA-alpha-MSH)n constitute a thick reservoir of the anti-inflammatory peptide and promote adhesion and proliferation of pulp fibroblast on the biomaterial surface. These nanostructured films could be adapted for an endodontic regeneration application to target pulp connective tissue regeneration. Firstly, the crucial reduction of inflammation could be helpful by using PGA-alpha-MSH and secondly the initiation of the regeneration of the connective tissue will be promoted by the whole nanostructured film of which allows pulp cells colonisation.

Control of reaction efficiency by two-color two-pulse excitation: Photoisomerization of indocyanine green in condensed phase

In cyanine dye, photoisomerization paths involving multiphoton processes were found by two-color two-pulse correlation of ultrafast transient absorption spectroscopy. The reaction efficiency depended on the interval between two pump pulses, UV and NIR pulses, as well as the fluence of the NIR pulse, but was little dependent on that of the UV pulse. These results indicate that the new photoisomerization paths involve the NIR multiphoton process and/or the UV one-photon process. The difference in two-pulse correlation between positive and negative time regions revealed a new reaction path that had the highest branching ratio of cis isomer to other leuco forms.

Search for the standard model Higgs boson in the two-electron and two-muon final state with the CMS detector

The decay of the standard model Higgs boson to ZZ(⋆), with both Zs decaying to leptons is one of the most important potential discovery channels for the Higgs boson at the large hadron collider at CERN. The four lepton state with the highest branching ratio is the two-electron two-muon final state. This paper presents the discovery potential of the Higgs boson in this channel with the CMS detector. Higgs boson masses between 115 and 600 GeV are explored. With the exception of a narrow region close to mH = 170 GeV, it is found that for 130 GeV⩽mH⩽ 500 GeV, the Higgs boson is expected to be observable at CMS with significance exceeding 5σ with 30 fb−1 of integrated luminosity.

Search for anomalous semileptonic decay of heavy flavor hadrons produced in association with aWboson at CDF II

We present a search for anomalous semileptonic decays of heavy flavor hadrons produced in association with a $W$ boson, in proton-antiproton collisions at sqrt{s}=1.96 TeV. We use 162 pb-1 of data collected with the CDF II detector at the Fermilab Tevatron Collider. We select events with one W boson and at least one jet with an identified secondary vertex. In the jets with a secondary vertex we look for a semileptonic decay to a muon. We compare the number of jets with both a secondary vertex and a semileptonic decay, and the kinematic properties of these jets, with the standard model expectation of W plus heavy flavor production and decay. No discrepancy is seen between the observation and the expectation, and we set limits on the production cross section of a B-like hadron with an anomalously high semileptonic branching ratio.

Fission barriers for the emission of odd-numbered fragments from multichargedC60prepared inAr8+‐C60collisions

We report on measurements of the branching ratios of emission of small C{sub n}{sup +} fragments in asymmetrical fission of highly charged C{sub 60}{sup r+} ions (r=4-6). For the channels corresponding to the emission of one fragment, only small fragments with an even number of carbon atoms are observed. For the channels with the emission of two fragments, successive emission of small fragments with an odd number of carbon atoms has been observed with a surprisingly high branching ratio (30%). In order to reproduce the experimental branching ratios in the framework of a statistical evaporation model, the height of fission barriers for the emission of one odd numbered fragment has to be reduced at higher temperature in order to allow the opening of these channels that are forbidden at lower temperature.

Lepton polarization asymmetries forB→K*ell+ell−: A Model Independent approac

In this work we shall derive expressions for the single and double lepton polarization asymmetries for the exclusive decay $B \to K^* \ell^+ \ell^-$, using the most general model independent effective Hamiltonian. We have conducted this study with this particular channel as it has the highest branching ratio among the various purely leptonic and semi-leptonic decay modes, making this mode particularly useful for studying physics beyond the SM. We have also analyzed the effects on these polarization asymmetries, and hence the physics underlying it, when complex phases are included in some of the Wilson coefficients.

Core-level spectroscopic study of FeO andFeS2

The electronic structures of iron oxide and iron disulfide (FeO and $\mathrm{Fe}{\mathrm{S}}_{2}$) have been examined using x-ray emission spectroscopy and other core-level spectroscopies. We compare the excitation spectra for charge neutral excitation (x-ray emission) and ionization (photoelectron spectroscopy) at the $2p$ edge and with final-state $3s$ holes. At the Fe ${L}_{2}$-edge, the branching ratio of $L\ensuremath{\beta}$ to $L\ensuremath{\alpha}$ emission is much higher for high spin FeO than for low spin $\mathrm{Fe}{\mathrm{S}}_{2}$, similar to previous observations of Heusler alloys. We suggest that there is a general trend toward high branching ratios for magnetic $3d$ materials and low branching ratios for nonmagnetic materials. Resonant inelastic x-ray spectra of FeO with $3s$ final-state holes show a smaller exchange splitting than the corresponding x-ray photoemission spectroscopy spectra with $3s$ hole states.

Large direct CP violation in B0→π+π− and an enhanced branching ratio for B0→π0π0

Recent measurements of B0→ππ decays reveal two features that are in conflict with conventional calculations: the channel B0(B̄0)→π+π− shows a large direct CP-violating asymmetry, and the channel B0(B̄0)→π0π0 has an unexpectedly high branching ratio. We show that both features can be understood in terms of strong-interaction mixing of ππ and DD̄ channels in the isospin-zero state, an effect that is important because of the large experimentally observed ratio Γ(B0/B̄0→D+D−)/Γ(B0/B̄0→π+π−)≈50. Our dynamical model correlates the branching ratios and the CP-violating parameters C and S, for the decays B0(B̄0)→π+π−, B0(B̄0)→π0π0, B0(B̄0)→D+D− and B0(B̄0)→D0D̄0.

Observation of dielectronic recombination through two-electron–one-photon correlative stabilization in an electron-beam ion trap

Dielectronic recombination (DR) for He-like ${\mathrm{Ar}}^{16+}$ through both one-electron--one-photon and two-electron--one-photon (TEOP) stabilizations of Li-like states was studied with an electron-beam ion trap (EBIT). It turned out that this is an excellent method to investigate TEOP transitions. Its advantages are a high branching ratio for the TEOP transition and clean conditions under which spectator electrons are controlled. Further, state- and configuration-resolved KLL DR cross sections were obtained due to the unsurpassed electron energy resolution achieved in the EBIT in the energy range around 2 keV.

Puzzles in Cabibbo-suppressed charm decays

We identify two Cabibbo suppressed D+ decay modes with anomalously high branching ratios which are not simply explained by any model. All standard model diagrams that can contribute to these decays are related by symmetries to diagrams for other decays that do not show any such enhancement. If these high branching ratios are confirmed by more precise experiments, they may require new physics to explain them. Anomalies in Ds decays and tests for possible violation of G-parity are discussed.

Search for new physics in rare B decays

A search for the decay B ±→K ±K ±π ∓ was performed using data collected by the OPAL detector at LEP. These decays are strongly suppressed in the Standard Model but could occur with a higher branching ratio in supersymmetric models, especially in those with R-parity violating couplings. No evidence for a signal was observed and a 90% confidence level upper limit of 1.29 × 10 −4 was set for the branching ratio. This upper limit was used to set a limit on the R-parity violating couplings.

Search for new physics in rare B decays

A search for the decay B ±→K ±K ± π ∓ was performed using data collected by the OPAL detector at LEP. These decays are strongly suppressed in the Standard Model but could occur with a higher branching ratio in supersymmetric models, especially in those with R-parity violating couplings. No evidence for a signal was observed and a 90% confidence level upper limit of 1.29×10 −4 was set for the branching ratio.