Relative Branching Fractions Research Articles

Theoretical investigation of the ground state dissociation pathways of CH2NO2

We report theoretical calculations of the nitromethyl radical (CH2NO2) ground state dissociation pathways. Calculations were performed using a combination of density functional theory (DFT) and coupled-cluster singles doubles and triples (CCSD(T)) with the cc-pVTZ basis set. The ground state unimolecular dissociation of the nitromethyl radical (CH2NO2) occurs via three dissociation pathways and we have characterized the transition state associated with the formation of NO + CH2O (channel I) which has a barrier height of 167.5 kJ/mol. We have also calculated the variational transition states associated with the CH2 + NO2 (channel II) and CH2NO + O (channel III) product channels. Thermal rate constants were calculated to model dissociations at temperatures relevant to shock tube experiments on nitromethane combustion. We find that the branching fractions vary over the range of temperatures relevant to nitromethane combustion, with channel II rising from <1% at 800 K to 14% at 2450 K, and channel I decreasing from >99% to 86% over the same range at one bar. RRKM theory was used to calculate unimolecular microcanonical rate constants at total energies corresponding to photoexcitation over a range of UV wavelengths from 279 to 228 nm to assess the relative branching fractions and compare to previous experimental data on the photodissociation of CH2NO2. The comparison reveals a disparity in the branching fraction between the calculation and experimental results, suggesting the possibility of an excited state dissociation pathway.

Observation of an a_{0}-like State with Mass of 1.817GeV in the Study of D_{s}^{+}→K_{S}^{0}K^{+}π^{0} Decays.

Using e^{+}e^{-} annihilation data corresponding to an integrated luminosity of 6.32 fb^{-1} collected at center-of-mass energies between 4.178 and 4.226GeV with the BESIII detector, we perform the first amplitude analysis of the decay D_{s}^{+}→K_{S}^{0}K^{+}π^{0} and determine the relative branching fractions and phases for intermediate processes. We observe an a_{0}-like state with mass of 1.817GeV in its decay to K_{S}^{0}K^{+} for the first time. In addition, we measure the ratio {B[D_{s}^{+}→K[over ¯]^{*}(892)^{0}K^{+}]/B[D_{s}^{+}→K[over ¯]^{0}K^{*}(892)^{+}]} to be 2.35_{-0.23stat}^{+0.42}±0.10_{syst}. Finally, we provide a precision measurement of the absolute branching fraction B(D_{s}^{+}→K_{S}^{0}K^{+}π^{0})=(1.46±0.06_{stat}±0.05_{syst})%.

Cross section measurements of the processes e+e−→ ωπ0 and ωη at center-of-mass energies between 3.773 and 4.701 GeV

The Born cross sections of the processes e+e− → ωπ0 and e+e− → ωη are measured at center-of-mass energies between 3.773 and 4.701 GeV using a total integrated luminosity of 22.7 fb−1 collected with the BESIII detector operating at the BEPCII collider. A simple s−n dependence for the continuum process can describe the measured Born cross sections. No significant contributions from the ψ(4160), Y(4230), Y(4360), ψ(4415), Y(4660) resonances are found, which indicates relative small branching fractions for these resonances into the ωπ0 and ωη final states.

Rescaling the isospin triangle argument for constraining phi _2 (alpha): Consolidating Belle II and a potential path forward for LHCb

A rescaling of the SU(2) isospin triangles constraining phi _2 (alpha) that relies on measurements of the experimentally cleaner relative branching fractions, as opposed to those absolute, is proposed. Paving the way towards more systematically sustainable analysis, this method promises to eliminate a dominant systematic at Belle II amongst others, namely the uncertainty on the number of B {bar{B}} pairs in data. Furthermore, a phi _2 constraint in the B rightarrow rho rho system at LHCb that is more independent of Belle II input is shown to become viable even without a measurement of C!P violation in B^0 rightarrow rho ^+rho ^-.

Ab Initio and RRKM/Master Equation Analysis of the Photolysis and Thermal Unimolecular Decomposition of Bromoacetaldehyde

Bromoacetaldehyde (BrCH2CHO) is a major stable brominated organic intermediate of the bromine-ethylene addition reaction during the arctic bromine explosion events. Similar to acetaldehyde, which has been recently identified as a source of organic acids in the troposphere, it may be subjected to photo-tautomerization initially forming brominated vinyl compounds. In this study, we investigate the unimolecular reactions of BrCH2CHO under both photolytic and thermal conditions using high-level quantum chemical calculations and Rice-Ramsperger-Kassel-Marcus (RRKM)/master equation analysis. The unimolecular decomposition of BrCH2CHO takes place through 14 dissociation and isomerization channels along a potential energy surface involving eight wells. Under the assumption of singlet ground-state potential energy surface-dominated photodynamics, the primary photodissociation yields of BrCH2CHO are investigated under both collision-free and collision energy transfer conditions. At atmospheric pressure and under tropospheric actinic flux conditions at ground level, depending on the assumed collisional energy transfer parameter, 150 cm-1 < ⟨ΔEdown⟩ < 450 cm-1, 78-33% of BrCH2CHO undergoes direct photodissociation instead of collisional deactivation at an excitation wavelength of 320 nm. This is significantly higher than the 14% reported for acetaldehyde, hence indicating a strong effect of bromine substitution on the product photolysis yield that is related to additional favorable Br and HBr forming dissociation channels. In contrast to the overall photodissociation quantum yield, the relative branching fractions of the photodissociation products are less dependent on the collisional energy transfer parameter. For a representative value of ⟨ΔEdown⟩ = 300 cm-1 and an excitation wavelength of 320 nm, with 27% for C-C bond fission, 11% for C-Br bond fission, 7% for HBr elimination, and only below 2% each for a consecutive O-Br fission reaction and the photo-tautomerization channel yielding brominated vinyl alcohol, the photodissociation is markedly different from the acetaldehyde case. Finally, as brominated halogenated compounds are of interest for flame inhibition purposes, thermal multichannel unimolecular rate constants were calculated for temperatures in the range from 500 to 2000 K. At a temperature of 2000 K and ambient pressure, the two main reaction channels are the C-Br and C-C bond fissions, contributing 35 and 43% to the total reaction flux, respectively.

Product Detection of the CH(X2Π) Radical Reaction with Cyclopentadiene: A Novel Route to Benzene

The reaction of the methylidyne radical (CH(X2Π)) with cyclopentadiene (c-C5H6) is studied in the gas phase at 4 Torr and 373 K using a multiplexed photoionization mass spectrometer. Under multiple collision conditions, the dominant product channel observed is the formation of C6H6 + H. Fitting the photoionization spectrum using reference spectra allows for isomeric resolution of C6H6 isomers, where benzene is the largest contributor with a relative branching fraction of 90 (±5)%. Several other C6H6 isomers are found to have smaller contributions, including fulvene with a branching fraction of 8 (±5)%. Master Equation calculations for four different entrance channels on the C6H7 potential energy surface are performed to explore the competition between CH cycloaddition to a C═C bond vs CH insertion into C-H bonds of cyclopentadiene. Previous studies on CH addition to unsaturated hydrocarbons show little evidence for the C-H insertion pathway. The present computed branching fractions support benzene as the sole cyclic product from CH cycloaddition, whereas fulvene is the dominant product from two of the three pathways for CH insertion into the C-H bonds of cyclopentadiene. The combination of experiment with Master Equation calculations implies that insertion must account for ∼10 (±5)% of the overall CH + cyclopentadiene mechanism.

Measurement of the absolute branching fraction of [formula omitted] decays

Based on 586 pb−1 of e+e− annihilation data collected at a center-of-mass energy of s=4.6GeV with the BESIII detector at the BEPCII collider, the absolute branching fraction of Λc+→pKS0η decays is measured for the first time to be B(Λc+→pKS0η)=(0.414±0.084±0.028)%, where the first uncertainty is statistical and the second is systematic. The result is compatible with a previous CLEO result on the relative branching fraction B(Λc+→pKS0η)B(Λc+→pK−π+), and consistent with theoretical predictions of SU(3) flavor symmetry.

Measurement of the relative branching fractions of B+→h+h′+h′− decays

The relative branching fractions of $B^+ \to h^+h^{\prime +}h^{\prime -}$ decays, where $h^{(\prime)}$ is a pion or kaon, are measured. The analysis is performed with a data sample, collected with the LHCb detector, corresponding to an integrated luminosity of $3.0 {\rm fb}^{-1}$ of $pp$ collisions. The results obtained improve significantly on previous measurements of these quantities, and are important for the interpretation of Dalitz plot analyses of three-body charmless hadronic decays of $B^+$ mesons.

χb(3P) multiplet revisited: Hyperfine mass splitting and radiative transitions

Invoked by the recent CMS observation regarding candidates of the $\chi_b(3P)$ multiplet, we analyze the ultrafine and mass splittings among $3P$ multiplet in our unquenched quark model (UQM) studies. The mass difference of $\chi_{b2}$ and $\chi_{b1}$ in $3P$ multiplet measured by CMS collaboration ($10.6 \pm 0.64 \pm 0.17$ MeV) is very close to our theoretical prediction ($12$ MeV). Our corresponding mass splitting of $\chi_{b1}$ and $\chi_{b0}$ enables us to predict more precisely the mass of $\chi_{b0}(3P)$ to be ($10490\pm 3$) MeV. Moreover, we predict ratios of the radiative decays of $\chi_{bJ}(nP)$ candidates, both in UQM and quark potential model. Our predicted relative branching fraction of $\chi_{b0}(3P)\to\Upsilon(3S)\gamma$ is one order of magnitude smaller than $\chi_{b2}(3P)$, this naturally explains the non-observation of $\chi_{b0}(3P)$ in recent CMS search. We hope these results might provide useful references for forthcoming experimental searches.

Dynamical analysis of the X resonance contributions to the decay J/ψ→γX→γϕϕ

The dynamics of the $J^{PC}=0^{-+}$, $0^{++}$, and $2^{++}$ resonance contributions to the decay $J/\psi\to\gamma X(J^{PC})\to\gamma\phi\phi$ is analysed using the data obtained by BESIII collaboration. The effective coupling constants parameterising invariant amplitudes of the transitions $J/\psi\to\gamma X(J^{PC})$ and $X(J^{PC})\to\phi\phi$ and masses of $X(J^{PC})$ resonances are found from the fits. They are used for evaluation of the branching fractions $B_{X(J^{PC})\to\phi\phi}$, relative branching fractions $B_{J/\psi\to\gamma X(J^{PC})\to\gamma\phi\phi}$, and for obtaining the photon angular distributions.

Light isovector resonances in π−p→π−π−π+p at 190 GeV/c

We have performed the most comprehensive resonance-model fit of $\pi^-\pi^-\pi^+$ states using the results of our previously published partial-wave analysis (PWA) of a large data set of diffractive-dissociation events from the reaction $\pi^- + p \to \pi^-\pi^-\pi^+ + p_\text{recoil}$ with a 190 GeV/$c$ pion beam. The PWA results, which were obtained in 100 bins of three-pion mass, $0.5 < m_{3\pi} < 2.5$ GeV/$c^2$, and simultaneously in 11 bins of the reduced four-momentum transfer squared, $0.1 < t' < 1.0$ $($GeV$/c)^2$, are subjected to a resonance-model fit using Breit-Wigner amplitudes to simultaneously describe a subset of 14 selected waves using 11 isovector light-meson states with $J^{PC} = 0^{-+}$, $1^{++}$, $2^{++}$, $2^{-+}$, $4^{++}$, and spin-exotic $1^{-+}$ quantum numbers. The model contains the well-known resonances $\pi(1800)$, $a_1(1260)$, $a_2(1320)$, $\pi_2(1670)$, $\pi_2(1880)$, and $a_4(2040)$. In addition, it includes the disputed $\pi_1(1600)$, the excited states $a_1(1640)$, $a_2(1700)$, and $\pi_2(2005)$, as well as the resonancelike $a_1(1420)$. We measure the resonance parameters mass and width of these objects by combining the information from the PWA results obtained in the 11 $t'$ bins. We extract the relative branching fractions of the $\rho(770) \pi$ and $f_2(1270) \pi$ decays of $a_2(1320)$ and $a_4(2040)$, where the former one is measured for the first time. In a novel approach, we extract the $t'$ dependence of the intensity of the resonances and of their phases. The $t'$ dependence of the intensities of most resonances differs distinctly from the $t'$ dependence of the nonresonant components. For the first time, we determine the $t'$ dependence of the phases of the production amplitudes and confirm that the production mechanism of the Pomeron exchange is common to all resonances.

The branching fraction calculations of Bc+ → ψ(2S)π+, Bc+ → J/ψK+ and Bc+ → J/ψDs+ decays relative to that of the Bc+ → J/ψπ+ mode

The weak decay of [Formula: see text] into [Formula: see text], [Formula: see text] and [Formula: see text] mesons, observed by LHCb collaboration for the first time, are calculated in the model which takes into account the “factorizable” contributions and “nonfactorizable” corrections. The decays of [Formula: see text] mesons into charmonia and light hadrons are expected to be well described by the factorization approximation. In the standard model, [Formula: see text], [Formula: see text] decays occur through only the tree-level diagrams and so there are no CP violation in these channels. The decay [Formula: see text] is expected to proceed mainly via a [Formula: see text] transition because the [Formula: see text] decay has identical final state and similar event topology, where it is chosen as the relative branching fraction channel. The ratio of branching fractions [Formula: see text] is of particular interest since the CKM matrix element is suppressed by a factor [Formula: see text], in which the [Formula: see text] occur through [Formula: see text] transition, but the dominant amplitude of the decay [Formula: see text] is a [Formula: see text] transition. The decay [Formula: see text] is examined by color-allowed, color-suppressed spectator and weak annihilation diagrams. The weak annihilation topology, in contrast to decays of other beauty hadrons, is not suppressed and can contribute significantly to the decay amplitude. Because of the [Formula: see text], [Formula: see text] and [Formula: see text] branching fractions are calculated relative to the [Formula: see text] decay, this decay mode is estimated separately, the ratio between them are [Formula: see text], [Formula: see text] and [Formula: see text], respectively, that are compatible with the experimental data.

Formula omitted] decays at BESIII

Using 567 pb-1 of e+e− annihilation data collected at a center-of-mass energy of s = 4.6 GeV with the BESIII detector, four analyses of Λc+ decay are reported in the QCD 17 conference. The measurements of singly Cabibbo-suppressed decays Λc+→pπ+π− and pK+K− are performed, and the relative branching fractions with respect to the Cabibbo-favored decay Λc+→pK−π+ are given, the absolute branching fractions are also obtained for these two decays. Evidence for the singly Cabibbo-suppressed decay Λc+→pη is found with 4.2σ, and the upper limit for Λc+→pπ0is reported. The absolute branching fraction B(Λc+→Σ−π+π+π0) is determined to be (2.11±0.33±0.14)%. In addition, an improved measurement of B(Λc+→Σ−π+π+) is determined as (1.81 ± 0.17 ± 0.09)%. The branching fraction of the inclusive decay Λc+→Λ+X is measured to be B(Λc+→Λ+X)=(38.2−2.2+2.8±0.6)%.

Dalitz plot analyses of J/ψ→π+π−π0 , J/ψ→K+K−π0 , and J/ψ→Ks0K±π∓ produced via e+e− annihilation with initial-state radiation

We study the processes $e^+ e^- \to \ \gamma_{\rm ISR} J/\psi$ where $J/\psi \to \pi^+ \pi^- \pi^0$, $J/\psi \to K^+ K^- \pi^0$, and $J/\psi \to K^0_S K^{\pm} \pi^{\mp}$ using a data sample of 519 $fb^{-1}$ recorded with the BaBar detector operating at the SLAC PEP-II asymmetric-energy $e^+ e^-$ collider at center-of-mass energies at and near the $\Upsilon(nS)$ ($n = 2,3,4$) resonances. We measure the ratio of branching fractions $R_1 = \frac{B(J/\psi \ \to \ K^+ K^- \pi^0)}{B(J/\psi \ \to \ \pi^+ \pi^- \pi^0)}$ and $R_2 = \frac{B(J/\psi \ \to \ K^0_S K^{\pm} \pi^{\mp})}{B(J/\psi \ \to \ \pi^+ \pi^- \pi^0)}$. We perform Dalitz-plot analyses of the three $J/\psi$ decay modes and measure fractions for resonances contributing to the decays. We also analyze the $J/\psi \to \pi^+ \pi^- \pi^0$ decay using the Veneziano model. We observe structures compatible with the presence of $\rho(1450)$ in all the three $J/\psi$ decay modes and measure the relative branching fraction: $R(\rho(1450)) = \frac{B(\rho(1450) \ \to \ K^+ K^-)}{B(\rho(1450) \ \to \ \pi^+ \pi^-)} = 0.307 \pm 0.084 ({\rm stat}) \pm 0.082 ({\rm sys})$.

Dalitz plot analysis ofηc→K+K−ηandηc→K+K−π0in two-photon interactions

We study the processes γγ→K+K−η and γγ→K+K−π0 using a data sample of 519 fb−1 recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e+e− collider at center-of-mass energies at and near the ϒ(nS) (n=2,3,4) resonances. We observe ηc→K+K−π0 and ηc→K+K−η decays, measure their relative branching fraction, and perform a Dalitz plot analysis for each decay. We observe the K0*(1430)→Kη decay and measure its branching fraction relative to the Kπ decay mode to be R(K0*(1430))=B(K0*(1430)→Kη)B(K0*(1430)→Kπ)=0.092±0.025−0.025+0.010. The ηc→K+K−η and K0*(1430)→Kη results correspond to the first observations of these channels. The data also show evidence for ηc(2S)→K+K−π0 and first evidence for ηc(2S)→K+K−η.6 MoreReceived 27 March 2014DOI:https://doi.org/10.1103/PhysRevD.89.112004© 2014 American Physical Society

Search for theX(4140)state inB+→J/ψϕK+decays with the D0 detector

We investigate the decay B^+ -> J/psi phi K^+ in a search for the X(4140) state, a narrow threshold resonance in the J/psi phi system. The data sample corresponds to an integrated luminosity of 10.4 fb^{-1} of ppbar collisions at sqrt s =1.96 TeV collected by the D0 experiment at the Fermilab Tevatron collider. We observe a mass peak with a statistical significance of 3.1 standard deviations and measure its invariant mass to be M=4159.0 +-.3 (stat) +- 6.6 (syst) MeV and its width to be Gamma= 19.9+-12.6 (stat)}^{+1.0}_{-8.0} (syst) MeV. Identifying this mass peak as the X(4140), we measure, for M(J/psi phi) <4.59 GeV, the relative branching fraction B_rel= B(B^+ -> X(4140) K^+)/ B(B^+ ->J/psi phi K^+) to be 21+-8 (stat) +- 4 (syst)%. In addition, the data can accommodate the presence of a second enhancement at a mass of 4328.5+- 12.0 MeV.

Search for the decay [formula omitted

A search for the D0→π+π−μ+μ− decay, where the muon pair does not originate from a resonance, is performed using proton–proton collision data corresponding to an integrated luminosity of 1.0fb−1 recorded by the LHCb experiment at a centre-of-mass energy of 7 TeV. No signal is observed and an upper limit on the relative branching fraction with respect to the resonant decay mode D0→π+π−ϕ(→μ+μ−), under the assumption of a phase-space model, is found to beB(D0→π+π−μ+μ−)/B(D0→π+π−ϕ(→μ+μ−))<0.96 at 90% confidence level. The upper limit on the absolute branching fraction is evaluated to be B(D0→π+π−μ+μ−)<5.5×10−7 at 90% confidence level. This is the most stringent to date.

Product Branching Fractions of the CH + Propene Reaction from Synchrotron Photoionization Mass Spectrometry

The CH(X(2)Π) + propene reaction is studied in the gas phase at 298 K and 4 Torr (533.3 Pa) using VUV synchrotron photoionization mass spectrometry. The dominant product channel is the formation of C4H6 (m/z 54) + H. By fitting experimental photoionization spectra to measured spectra of known C4H6 isomers, the following relative branching fractions are obtained: 1,3-butadiene (0.63 ± 0.13), 1,2-butadiene (0.25 ± 0.05), and 1-butyne (0.12 ± 0.03) with no detectable contribution from 2-butyne. The CD + propene reaction is also studied and two product channels are observed that correspond to C4H6 (m/z 54) + D and C4H5D (m/z 55) + H, formed at a ratio of 0.4 (m/z 54) to 1.0 (m/z 55). The D elimination channel forms almost exclusively 1,2-butadiene (0.97 ± 0.20) whereas the H elimination channel leads to the formation of deuterated 1,3-butadiene (0.89 ± 0.18) and 1-butyne (0.11 ± 0.02); photoionization spectra of undeuterated species are used in the fitting of the measured m/z 55 (C4H5D) spectrum. The results are generally consistent with a CH cycloaddition mechanism to the C═C bond of propene, forming 1-methylallyl followed by elimination of a H atom via several competing processes. The direct detection of 1,3-butadiene as a reaction product is an important validation of molecular weight growth schemes implicating the CH + propene reaction, for example, those reported recently for the formation of benzene in the interstellar medium (Jones , B. M. Proc. Natl. Acad. Sci. U.S.A. 2011 , 108 , 452 - 457).

Measurement of the branching fractions of the decaysBs0→D¯0K−π+andB0→D¯0K+π−

The first observation of the decay Bs -> D0bar K- {\pi}+ is reported. The analysis is based on a data sample, corresponding to an integrated luminosity of 1.0 fb-1 of pp collisions, collected with the LHCb detector. The branching fraction relative to that of the topologically similar decay B0 -> D0bar {\pi}+ {\pi}- is measured to be BR(Bs -> D0bar K- {\pi}+)/BR(B0 -> D0bar {\pi}+ {\pi}-) = 1.18 +- 0.05 (stat.) +- 0.12 (syst.). In addition, the relative branching fraction of the decay B0 -> D0bar K+ {\pi}- is measured to be BR(B0 -> D0bar K+ {\pi}-)/BR(B0 -> D0bar {\pi}+ {\pi}-) = 0.106 +- 0.007 (stat.) +- 0.008 (syst.).

Probing the Dark Matter mass and nature with neutrinos

We study the possible indirect neutrino signal from dark matter annihilations inside the Sun's core for relatively light dark matter masses in the \U0001d4aa(10) GeV range. Due to their excellent energy reconstruction capabilities, we focus on the detection of this flux in liquid argon or magnetized iron calorimeter detectors, proposed for the next generation of far detectors of neutrino oscillation experiments and neutrino telescopes. The aim of the study is to probe the ability of these detectors to determine fundamental properties of the dark matter nature such as its mass or its relative annihilation branching fractions to different channels. We find that these detectors will be able to accurately measure the dark matter mass as long as the dark matter annihilations have a significant branching into the neutrino or at least the τ channel. We have also discovered degeneracies between different dark matter masses and annihilation channels, where a hard τ channel spectrum for a lower dark matter mass may mimic that of a softer quark channel spectrum for a larger dark matter mass. Finally, we discuss the sensitivity of the detectors to the different branching ratios and find that it is between one and two orders of magnitude better than the current bounds from those coming from analysis of Super-Kamiokande data.