Measurement Of Branching Ratio Research Articles

Reactions of H2, HD, and D2 with H2+, HD+, and D2+: Product-Channel Branching Ratios and Simple Models.

We present measurements of the product-channel branching ratios of the reactions (i) HD+ + HD forming H2D+ + D (38.1(30)%) and HD2+ + H (61.9(30)%), (ii) HD+ + D2 forming HD2+ + D (61.4(35)%) and D3+ + H (38.6(35)%), and (iii) D2+ + HD forming HD2++ D (60.5(20)%) and D3+ + H (39.5(20)%) at collision energies Ecoll near zero, i.e., below kB × 1 K. These branching ratios are compared with branching ratios predicted using three simple models: a combinatorial model (M1), a model (M2) describing the reactions as H-, H+-, D-, and D+-transfer processes, and a statistical model (M3) that relates the reaction rate coefficients to the translational and rovibrational state densities of the HnD3–n+ + H/D (n = 0, 1, 2 or 3) product channels. The experimental data are incompatible with the predictions of models M1 and M2 and reveal that the branching ratios exhibit clear correlations with the product state densities.

Lifetime of the hypertriton

Conflicting values of the hypertriton lifetime τ(3ΛH) were derived in relativistic heavy ion (RHI) collision experiments over the last decade. A very recent ALICE Collaboration measurement is the only experiment where the reported τ(3ΛH) comes sufficiently close to the free-Λ lifetime τΛ, as expected naively for a very weakly bound Λ in 3ΛH. We revisited theoretically this 3ΛH lifetime puzzle [1], using 3ΛH and 3He wave functions computed within the ab initio no-core shell model employing interactions derived from chiral effective field theory to calculate the two-body decay rate Γ(3ΛH → 3He + π−). We found significant but opposing contributions arising from ΣNN admixtures in 3ΛH and from π− − 3He final-state interaction. To derive τ(3ΛH), we evaluated the inclusive π− decay rate Γπ− (3ΛH) by using the measured branching ratio Γ(3ΛH → 3He + π−)/Γπ− (3ΛH) and added the π0 contributions through the ΔI = 1/2rule. The resulting τ(3ΛH) varies strongly with the rather poorly known Λ separation energy Esep(3ΛH) and it is thus possible to associate each one of the distinct RHI τ(3ΛH) measurements with its own underlying value of Esep(3ΛH).

Measurement of time dependent product branching ratios indicates two-state reactivity in metal mediated chemical reactions.

For several decades, the influence of Two State Reactivity (TSR) has been implicated in a host of reactions, but has lacked a stand-alone, definitive experimental kinetic signature identifying its occurrence. Here, we demonstrate that the measurement of a temporally dependent product branching ratio is indicative of spin inversion and is a kinetic signature of TSR. This is caused by products exiting different hypersurfaces with different rates and relative exothermicities. The composite measurement of product intensities with the same mass but with different multiplicities yield biexponential temporal dependences with the sampled product ratio changing in time. These measurements are made using the single photon initiated dissociative rearrangement reaction (SPIDRR) technique which identifies TSR but further determines the kinetic parameters for reaction along the original ground electronic surface in competition with spin inversion and its consequent TSR.

Revisiting rescattering contributions to overline{B} (s) \u2192 {D}_{(s)}^{left(ast right)}M decays

Motivated by the reported discrepancies between experimental data and Standard Model predictions for the branching ratios of the color-allowed decays overline{B} 0 → D(*)+K− and {overline{B}}_s^0 → {D}_s^{left(ast right)+}{pi}^{-} , we study final-state rescattering effects on overline{B} (s) → {D}_{(s)}^{left(ast right)}P and overline{B} (s) → D(s)V, where P(V) is a light pseudoscalar (vector) meson. We consider quasi-elastic rescatterings in the framework of SU(3) and U(3) flavor symmetries, and find that the effects cannot explain the measured branching ratios of the color-allowed and color-suppressed decays simultaneously. We also perform global fits to the overline{B} (s) → {D}_{(s)}^{left(ast right)}P and overline{B} (s) → D(s)V data, allowing for new physics contributions to the Wilson coefficient a1 associated with the color-allowed tree amplitudes. It is shown that the fits prefer a downward shift of mathcal{O} (10%) in a1 even in the presence of the quasi-elastic rescattering contributions.

Global determination of two-meson distribution amplitudes from three-body B decays in the perturbative QCD approach

We perform a global analysis of three-body charmless hadronic decays $B\to VP_3\to P_1P_2P_3$ in the perturbative QCD (PQCD) approach, where $V$ denotes an intermediate vector resonance, and $P_i$, $i=1,2,3$, denote final-state pseudoscalar mesons. Fitting the PQCD factorization formulas at leading order in the strong coupling $\alpha_s$ to measured branching ratios and direct $CP$ asymmetries, we determine the Gegenbauer moments in the two-meson distribution amplitudes (DAs) for the meson pairs $P_1P_2=\pi\pi, K\pi, KK$. The fitted Gegenbauer moments are then employed to make predictions for those observables, whose data are excluded in the fit due to larger experimental uncertainties. A general consistency between our predictions and data is achieved, which hints the validity of the PQCD formalism for the above three-body $B$ meson decays and the universality of the nonperturbative two-meson DAs. The obtained two-meson DAs can be applied to PQCD studies of other multi-body $B$ meson decays involving the same meson pairs. We also attempt to determine the dependence of the Gegenbauer moments on the meson-pair invariant mass, and demonstrate that this determination is promising, when data become more precise.

Branching ratios for the three most intense gamma rays in the decay of 47Ca

A sample of 47Ca produced through isotope harvesting at the National Superconducting Cyclotron Laboratory was used to measure branching ratios of 7.17(5)%, 7.11(5)%, and 75.0(5)% for the 489.2, 807.9, and 1297.1 keV characteristic gamma rays, respectively. Based on these updated branching ratios, the ground state to ground state 47Ca to 47Sc beta decay branching ratio has been indirectly measured as 17.7(5)% and the ground state to 1297.1 keV excited state as 82.2(5)%. These values represent a greatly increased precision for all five branching ratios compared to the currently accepted values (Burrows, 2007). The measurements presented here were made relative to the ingrown 47Sc daughter in a47Ca sample and the well-established 159.4 keV gamma-ray branching ratio and the half-life for the decay of 47Sc (Reher et al., 1986; Meadows and Mode, 1968; Mommsen et al., 1980). These measurements were supported by verifying that the half-lives measured from characteristic gamma-ray peaks over multiple spectra for both 47Ca and 47Sc were consistent with previously reported values. Additionally, the half-lives of both 47Ca and 47Sc were independently measured with Liquid Scintillation Counting to reverify the previously reported values used in this study to find updated gamma-ray branching ratio values.

One-loop corrections to the Higgs boson invisible decay in the dark doublet phase of the N2HDM

The Higgs invisible decay width may soon become a powerful tool to probe extensions of the Standard Model with dark matter candidates at the Large Hadron Collider. In this work, we calculate the next-to-leading order (NLO) electroweak corrections to the 125 GeV Higgs decay width into two dark matter particles. The model is the next-to-minimal 2-Higgs-doublet model (N2HDM) in the dark doublet phase, that is, only one doublet and the singlet acquire vacuum expectation values. We show that the present measurement of the Higgs invisible branching ratio, BR(H → invisible < 0.11), does not lead to constraints on the parameter space of the model at leading order. This is due to the very precise measurements of the Higgs couplings but could change in the near future. Furthermore, if NLO corrections are required not to be unphysically large, no limits on the parameter space can be extracted from the NLO results.

Accurate prediction and measurement of vibronic branching ratios for laser cooling linear polyatomic molecules.

We report a generally applicable computational and experimental approach to determine vibronic branching ratios in linear polyatomic molecules to the 10-5 level, including for nominally symmetry-forbidden transitions. These methods are demonstrated in CaOH and YbOH, showing approximately two orders of magnitude improved sensitivity compared with the previous state of the art. Knowledge of branching ratios at this level is needed for the successful deep laser cooling of a broad range of molecular species.

Measuring Photodissociation Product Quantum Yields Using Chemical Ionization Mass Spectrometry: A Case Study with Ketones.

Measurements of photolysis quantum yields are challenging because of the difficulties in measuring the first-generation photodissociation products, interference from other products or contaminants, sufficient photon fluxes and/or low absorption cross sections of the photolyte to make detectable amounts of products, and quantification of the photon flux. In the case of acetone (and other atmospherically relevant ketones) the uncertainty in the photolysis quantum yield creates uncertainty in the calculated OH radical and acyl peroxy nitrate production in the atmosphere. We present a new method for determining photodissociation product quantum yields by measuring acyl peroxy radicals (RC(O)O2) produced in the photolysis of ketones in air using chemical ionization mass spectrometry (CIMS). We show good agreement of our CIMS method with previously published quantum yields of the acyl radical from photolysis of biacetyl and methyl ethyl ketone (MEK) at 254 nm. Additionally, we highlight the capabilities of this CIMS method through the measurement of photolysis branching ratios for MEK. We suggest future applications of CIMS (in the laboratory and field) to measure RC(O)O2 and associated photolysis processes.

Global analysis of hadronic two-body B decays in the perturbative QCD approach

Based on the flavor structure of four-quark effective operators, we develop an automatic computation program to calculate hadronic two-body $B$ meson decay amplitudes, and apply it to their global analysis in the perturbative QCD (PQCD) approach. Fitting the PQCD factorization formulas for $B\to PP,VP$ decays at leading order in the strong coupling $\alpha_s$ to measured branching ratios and direct CP asymmetries, we determine the Gegenbauer moments in light meson light-cone distribution amplitudes (LCDAs). It is found that most of the fitted Gegenbauer moments of the twist-2 and twist-3 LCDAs for the pseudoscalar meson $P$ ($P=\pi$, $K$) and vector meson $V$ ($V=\rho$, $K^*$) agree with those derived in QCD sum rules. The shape parameter for the $B_s$ meson distribution amplitude and the weak phase $\phi_3(\gamma)=(75.1\pm2.9)^\circ$ consistent with the value in Particle Data Group are also obtained. It is straightforward to extend our analysis to higher orders and higher powers in the PQCD approach, and to the global determination of LCDAs for other hadrons.

Experimental L-series x ray production cross sections for Re by tuning synchrotron radiation across its Li (i=1–3) sub-shell ionization thresholds

In the present work, the Lk (k = l, α, η, β1, β3, β6, β4, β2,15, β5,7, β9,10, γ1,5, γ2,3,6,8, γ4) x ray production (XRP) cross sections have been measured for Re at energies across its Li (i = 1–3) sub-shell ionization threshold energies covering the region 10.5 keV–14.0 keV using synchrotron radiation. The measured values have been compared with the three sets of XRP cross sections calculated using the Dirac-Fock model based x ray emission rates, the non-relativistic Hartree-Fock-Slater model based Li (i = 1–3) sub-shell photoionization cross-sections and three sets of the fluorescence (ωi) and Coster-Kronig (fij) yields based on the Dirac-Hartree-Slater model based values, the semi-empirical values and the experimental values reported earlier by us. The present measured XRP cross sections are found to be in a good agreement with those calculated using the experimental ωi/fij values; whereas these are found to be significantly lower (~30%) than those calculated using the theoretical and the semi-empirical ωi/fij values. In view of the observed good agreement of the present measured Lk XRP cross sections with those calculated using the experimental fluorescence and Coster-Kronig yields and that of the measured branching ratios (ILl/ILα,; ILβ2,15/ILα,; ILη/ILβ1; ILγ1,5/ILβ1 and ILγ2,3/ILβ3) with the theoretical values calculated using the Dirac-Fock model based x ray emission rates, the use of these parameters is recommended for different analytical applications.

Measurement of the very rare K+\u2192 {pi}^{+}nu overline{nu} decay

The NA62 experiment reports the branching ratio measurement mathrm{BR}left({K}^{+}to {pi}^{+}nu overline{nu}right)=left({10.6}_{-3.4}^{+4.0}left|{}_{mathrm{stat}}right.pm {0.9}_{mathrm{syst}}right)times {10}^{-11} at 68% CL, based on the observation of 20 signal candidates with an expected background of 7.0 events from the total data sample collected at the CERN SPS during 2016–2018. This provides evidence for the very rare K+→ {pi}^{+}nu overline{nu} decay, observed with a significance of 3.4σ. The experiment achieves a single event sensitivity of (0.839 ± 0.054) × 10−11, corresponding to 10.0 events assuming the Standard Model branching ratio of (8.4 ± 1.0) × 10−11. This measurement is also used to set limits on BR(K+→ π+X), where X is a scalar or pseudo-scalar particle. Details are given of the analysis of the 2018 data sample, which corresponds to about 80% of the total data sample.

Luminescence behavior of Nd3+ions doped ZnO-BaO-(Gd2O3/GdF3)- P2O5 glasses for laser material applications

In current study Neodymium doped phosphate glasses were prepared and subsequently the Physical and luminescence properties of these glasses were thoroughly analyzed. In total, eleven absorption bands centered at 352, 431, 474, 512, 526, 583, 626, 683, 746, 803 and 875 nm were observed in absorption spectra. Similarly, the emission spectra of the prepared glasses recorded with 804 nm excitation show three radiative transitions peaks at 873, 1054 and 1333 nm. The luminescence properties of present glasses analyzed theoretically as several radiative properties studied through Judd-Ofelt theory. The emission cross section for 4F3/2→4I11/2 transition of Nd3+ ions, measured to be 11.2 × 10−20 cm2 in the case of oxide and 13.10 × 10−20 cm2 in the case of oxyfluoride glass. Similarly, the calculated and measured branching ratio for oxide glass are 54% and 51% respectively, and for oxyfluoride glass the calculated and measured branching ratios are 53% and 55% respectively. From the FTIR spectra it is noted that the bands correspond to the OH group show low transmittance intensity in oxyfluoride glass than oxide glass which is an evident of low OH contents oxyfluoride glass. In conclusion, from the results of present study reveal that the oxyfluoride glasses reported in present work can be a possible material for laser applications.

Establishing a nearly closed cycling transition in a polyatomic molecule

We study optical cycling in the polar free radical calcium monohydroxide (CaOH) and establish an experimental path towards scattering $\sim$$10^4$ photons. We report rovibronic branching ratio measurements with precision at the $\sim10^{-4}$ level and observe weak symmetry-forbidden decays to bending modes with non-zero vibrational angular momentum. Calculations are in excellent agreement with these measurements and predict additional decay pathways. Additionally, we perform high-resolution spectroscopy of the $\widetilde{\text{X}}\,^2\Sigma^+(12^00)$ and $\widetilde{\text{X}}\,^2\Sigma^+(12^20)$ hybrid vibrational states of CaOH. These advances establish a path towards radiative slowing, 3D magneto-optical trapping, and sub-Doppler cooling of CaOH.

Precision branching-ratio measurements in ^{18}O

An experiment has been performed utilising the ^{12}C(^{7}Li,p)^{18}O reaction to populate high-energy states in ^{18}O. Using the Munich Q3D magnetic spectrograph in conjunction with the Birmingham large-angular-coverage DSSD array, branching ratios have been measured for over fifty states in ^{18}O, investigating the alpha -decay, n-decay, 2n-decay and gamma -decay branches. In tandem, Monte-Carlo techniques have been used to identify and separate features.

Search for evidence of rotational cluster bands in O18

Clustering in $^{18}\mathrm{O}$ is of great interest to the nuclear physics community, due to theoretical predictions of $\mathrm{core}+\ensuremath{\alpha}$ and nuclear molecular structures. An experiment was performed in order to measure branching ratios for states in $^{18}\mathrm{O}$, determining the tendency towards clustering based on the value of ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\alpha}}/{\mathrm{\ensuremath{\Gamma}}}_{\text{tot}}$ for each state, and the reduced widths compared to the Wigner limit. An experimental method that enables the measurement of branching ratios for almost all available decay modes, including $\ensuremath{\gamma}$ decay, $\ensuremath{\alpha}$ decay, and $n$ decay, was employed. The method is also sensitive to the population of excited states in daughter nuclei, allowing for more accurate determination of the ${\ensuremath{\alpha}}_{0}$ branch. The measurements represent, for several states, either the first branching ratio measurement or the first determination of ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\alpha}}/{\mathrm{\ensuremath{\Gamma}}}_{\text{tot}}$. Based on these measurements, no evidence of consistent cluster structure is seen across any of the bands previously proposed, casting doubt on their existence. Despite this, some states displaying cluster structure are observed.

High-precision branching ratio measurement and spin assignment implications for Ga62 superallowed β decay

A high-precision branching ratio measurement for the superallowed Fermi $\beta^{+}$ emitter $^{62}$Ga was performed with the Gamma-Ray Infrastructure for Fundamental Investigations of Nuclei (GRIFFIN) spectrometer at the Isotope Separator and Accelerator (ISAC) radioactive ion beam facility at TRIUMF. The high efficiency of the GRIFFIN spectrometer allowed 63 $\gamma$-ray transitions, with intensities down to $\approx$1 part per million (ppm) per $^{62}$Ga $\beta^{+}$ decay, to be placed in the level scheme of the daughter nucleus $^{62}$Zn, establishing the superallowed $\beta$ branching ratio for $^{62}$Ga decay to be 99.8577$^{+0.0023}_{-0.0029}\%$, a factor of 4 more precise than the previous world average. For several cascades, $\gamma-\gamma$ angular correlation measurements were performed to assign spins and/or determine the mixing ratios of transitions. In particular, the spin of the 2.342 MeV excited state in the daughter nucleus $^{62}$Zn was definitively assigned as $J = 0$. This assignment resolves a discrepancy between previous measurements and has important implications for the isospin symmetry breaking correction, $\delta_{C1}$, in $^{62}$Ga superallowed Fermi $\beta$ decay.

Low energy cross section of 18O(p,γ)19F

The observation of oxygen isotopes in giant stars sheds light on mixing processes operating in their interiors. Due to the very strong correlation between nuclear burning and mixing processes it is very important to reduce the uncertainty on the cross sections of the nuclear reactions that are involved. In this paper we focus our attention on the reaction 18O(p,γ)19F. While the 18O(p, α)15N channel is thought to be dominant, the (p,γ) channel can still be an important component in stellar burning in giants, depending on the low energy cross section. So far only extrapolations from higher-energy measurements exist and recent estimates vary by orders of magnitude. These large uncertainties call for an experimental reinvestigation of this reaction.We present a direct measurement of the 18O(p,γ)19F cross section using a high-efficiency 4π BGO summing detector at the Laboratory for Underground Nuclear Astrophysics (LUNA). The reaction cross section has been directly determined for the first time from 140 keV down to 85 keV and the different cross section components have been obtained individually. The previously highly uncertain strength of the 90 keV resonance was found to be three orders of magnitude lower than an indirect estimate based on nuclear properties of the resonant state and a factor of 20 lower than a recently established upper limit. This result excludes the possibility that the 90 keV resonance can contribute significantly to the stellar reaction rate.In addition the strengths and branching ratios of resonances between 150 and 400 keV have been determined with much improved precision and sensitivity using a HPGe detector, including a first measurement of branching ratios of the 216 keV resonance. Preliminary results are presented.

Measurement of the ^{229}Th Isomer Energy with a Magnetic Microcalorimeter.

We present a measurement of the low-energy (0-60keV) γ-ray spectrum produced in the α decay of ^{233}U using a dedicated cryogenic magnetic microcalorimeter. The energy resolution of ∼10 eV, together with exceptional gain linearity, allows us to determine the energy of the low-lying isomeric state in ^{229}Th using four complementary evaluation schemes. The most precise scheme determines the ^{229}Th isomer energy to be 8.10(17)eV, corresponding to 153.1(32)nm, superseding in precision previous values based on γ spectroscopy, and agreeing with a recent measurement based on internal conversion electrons. We also measure branching ratios of the relevant excited states to be b_{29}=9.3(6)% and b_{42}<0.7%.

Total branching ratio of the K− two-nucleon absorption in 12C

This work is a critical re-analysis of the results obtained by the AMADEUS collaboration, concerning the measurement of the K− multi-nucleon absorption reactions, on a 12C target, in the Λp final state (Del Grande et al 2019 Eur. Phys. J. C 79, 190). We show that a good estimate of the K− two-nucleon absorption total branching ratio can be extracted, given that the measured final state interactions and conversion reactions contain information on almost all the remaining hyperon-nucleon final state combinations. The main contribution to the total branching ratio of the K− two-nucleon absorption in Carbon is extracted from the measured ratios and is found to be , which is in agreement with recent theoretical predictions. The missing contribution, from those few channels for which a Λp pair could not be detected in the final state of the interaction, is also estimated combining both the measured branching ratios and the available theoretical information, and amounts to . All together the total branching ratio of the K− two-nucleon absorption in Carbon is found to be