Branching Ratios Research Articles

High-Resolution Imaging Study on Photodissociation of OCS+ [A2ΠΩ=1/2,3/2 (ν1 0 ν3)

The development of the velocity map ion imaging (VMI) technique has greatly advanced the study of photodissociation dynamics. The high-resolution imaging study of the photodissociation allows for the acquisition of precise and detailed information on the fragments. This information can further provide more insight into the energy partition and potential pathways involved in the photodissociation process. In this study, we report the investigation on the photodissociation of OCS+ via the A2ΠΩ=1/2,3/2 states following the excitation of A2Π (ν1 0 ν3) ← X2Π (0 0 0) by using time-sliced VMI techniques in the ultraviolet region. Our investigation revealed significant mode-dependent recoil anisotropies and branching ratios of two product channels for both Ω = 1/2 and Ω = 3/2. The photolysis products also exhibited dramatic deviation in angular distributions and generally comparable kinetic energy distributions following the excitation to the same vibrational modes of A2ΠΩ states with two separate spin-orbit components. According to the observation in this study and previously reported photodissociation mechanisms of the OCS+ cations, the decay from the A2Π3/2 state was more likely via the internal conversion to high rovibrational states of the X2Π state, in comparison to the A2Π1/2 state.

Nucleoside Cation Radicals: Generation, Radical-Induced Hydrogen Atom Migrations, and Ribose Ring Cleavage in the Gas Phase.

Nucleoside ions that were furnished on ribose with a 2'-O-acetyl radical group were generated in the gas phase by multistep collision-induced dissociation of precursor ions tagged with radical initiator groups, and their chemistry was investigated in the gas phase. 2'-O-Acetyladenosine cation radicals were found to undergo hydrogen transfer to the acetoxyl radical from the ribose ring positions that were elucidated using specific deuterium labeling of 1'-H, 2'-H, and 4'-H and in the N-H and O-H exchangeable positions, favoring 4'-H transfer. Ion structures and transition-state energies were calculated by a combination of Born-Oppenheimer molecular dynamics and density functional theory and used to obtain unimolecular rate constants for competitive hydrogen transfer and loss of the acetoxyl radical. Migrations to the acetoxyl radical of ribose hydrogens 1'-H, 2'-H, 3'-H, and 4'-H were all exothermic, but product formation was kinetically controlled. Both Rice-Ramsperger-Kassel-Marcus (RRKM) and transition-state theory (TST) calculations indicated preferential migration of 4'-H in a qualitative agreement with the deuterium labeling results. The hydrogen migrations displayed substantial isotope effects that along with quantum tunneling affected the relative rate constants and reaction branching ratios. UV-vis action spectroscopy indicated that the cation radicals from 2'-O-acetyladenosine consisted of a mixture of isomers. Radical-driven dissociations were also observed for protonated guanosine, cytosine, and thymidine conjugates. However, for those nucleoside ions and cation radicals, the dissociations were dominated by the loss of the nucleobase or formation of protonated nucleobase ions.

The top quark rare decays with flavor violation

Abstract In the present study, we investigate the decays of the top quark $t\rightarrow c\gamma$, $t\rightarrow cg$, $t\rightarrow cZ$ and $t\rightarrow ch$. They are extremely rare processes in the Standard Model (SM). As the $U(1)$ extension of the minimal supersymmetric standard model (MSSM), the $U(1)_X$SSM features new superfields such as the right-handed neutrinos and three Higgs singlets. We analyze the effects of different sensitive parameters on the results and make reasonable theorecial predictions, which provides a useful reference for future experimental development. Considering the constraint of the updated experimental data, the numerical results show that the branching ratios of all four processes $t\rightarrow c\gamma,~cg,~cZ,~ch$ can reach the same order of magnitude as their experimental upper limits. Among them, $\tan\beta$ has the most obvious effect on each process and is the main parameter. $g_X$, $g_{YX}$, $\mu$, $M_2$, $\lambda_H$, $M_{U23}^2$ and $M_{Q23}^2$ are important parameters for the processes, and have effects on the numerical results. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Science and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.

Search for pair production of scalar and vector leptoquarks decaying to muons and bottom quarks in proton-proton collisions at s=13 TeV

A search for pair production of scalar and vector leptoquarks (LQs) each decaying to a muon and a bottom quark is performed using proton-proton collision data collected at s=13 TeV with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 138 fb−1. No excess above standard model expectation is observed. Scalar (vector) LQs with masses less than 1810 (2120) GeV are excluded at 95% confidence level, assuming a 100% branching fraction of the LQ decaying to a muon and a bottom quark. These limits represent the most stringent to date. © 2024 CERN, for the CMS Collaboration 2024 CERN

Searches for exclusive Higgs boson decays into D⁎γ and Z boson decays into D0γ and [formula omitted] in pp collisions at [formula omitted] with the ATLAS detector

Searches for exclusive decays of the Higgs boson into D⁎γ and of the Z boson into D0γ and Ks0γ can probe flavour-violating Higgs boson and Z boson couplings to light quarks. Searches for these decays are performed with a pp collision data sample corresponding to an integrated luminosity of 136.3 fb−1 collected at s=13TeV between 2016–2018 with the ATLAS detector at the CERN Large Hadron Collider. In the D⁎γ and D0γ channels, the observed (expected) 95% confidence-level upper limits on the respective branching fractions are B(H→D⁎γ)<1.0(1.2)×10−3, B(Z→D0γ)<4.0(3.4)×10−6, while the corresponding results in the Ks0γ channel are B(Z→Ks0γ)<3.1(3.0)×10−6.

Continuous-Time Quantum Walk in Glued Trees: Localized State-Mediated Almost Perfect Quantum-State Transfer.

In this work, the dynamics of a quantum walker on glued trees is revisited to understand the influence of the architecture of the graph on the efficiency of the transfer between the two roots. Instead of considering regular binary trees, we focus our attention on leafier structures where each parent node could give rise to a larger number of children. Through extensive numerical simulations, we uncover a significant dependence of the transfer on the underlying graph architecture, particularly influenced by the branching rate (M) relative to the root degree (N). Our study reveals that the behavior of the walker is isomorphic to that of a particle moving on a finite-size chain. This chain exhibits defects that originate in the specific nature of both the roots and the leaves. Therefore, the energy spectrum of the chain showcases rich features, which lead to diverse regimes for the quantum-state transfer. Notably, the formation of quasi-degenerate localized states due to significant disparities between M and N triggers a localization process on the roots. Through analytical development, we demonstrate that these states play a crucial role in facilitating almost perfect quantum beats between the roots, thereby enhancing the transfer efficiency. Our findings offer valuable insights into the mechanisms governing quantum-state transfer on trees, with potential applications for the transfer of quantum information.

A comprehensive study of ferroelectric, dielectric and optical properties of europium-doped SBD metal- organic framework

The synthesis of Europium-doped Strontium based benzene dicarboxylate dimethylformamide metal–organic framework- Eu([Sr(μ-BDC)(DMF)])- with short form as Eu:SBD@MOF was carried out using the solvothermal method. The investigation involved characterization techniques such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), CHN analysis, and energy-dispersive X-ray (EDX) elemental analysis. The results confirmed the formation of metal–organic crystals in the framework. The XRD characterization shows good alignment with the simulated pattern of SBD. The experimental absorption spectrum displays distinct transitions of the Eu (III) ion alongside transitions of the ligands. Calculations of line strengths for all observed transitions have been conducted. The Judd-Ofelt theory has been employed to determine intensity parameters, transition probabilities, branching ratios, and radiative lifetimes for the Eu: SBD@MOF. These JO parameters further aid in calculating various excited state properties. When excited by ultraviolet and visible photons, the complex exhibits emission in the red region respectively. The crystal’s dielectric loss and dielectric constant were investigated for their frequency dependence. It was observed that by virtue of DMF, a molecule linked to the crystal, a synthesized MOF exhibits a good dielectric characteristic and when the temperature is raised to 558 K, the dielectric constant drops sharply as DMF molecule could not stand after this temperature. Further ferroelectric studies reveal that the Eu: SBD@MOF has maximum polarization of 0.27 C/cm2 which is greater than Rochelle salt and other MOF’s. Exploring the broadband dielectric response of metal–organic frameworks (MOFs) open up new avenues in research, potentially leading to innovative applications in smart optoelectronics, terahertz sensors, high-speed telecommunications, and microelectronics.

Appropriate mowing can promote the growth of Anabasis aphylla through the auxin metabolism pathway

Anabasis aphylla (A. aphylla), a species of the Amaranthaceae family, is widely distributed in northwestern China and has high pharmacological value and ecological functions. However, the growth characteristics are poorly understood, impeding its industrial development for biopesticide development. Here, we explored the regenerative capacity of A. aphylla. To this end, different lengths of the secondary branches of perennial branches were mowed at the end of March before sprouting. The four treatments were no mowing (M0) and mowing 1/3, 2/3, and the entire length of the secondary branches of perennial branches (M1–M3, respectively). Next, to evaluate the compensatory growth after mowing, new assimilate branches’ related traits were recorded every 30 days, and the final biomass was recorded. The mowed plants showed a greater growth rate of assimilation branches than un-mowed plants. Additionally, with the increasing mowing degree, the growth rate and the final biomass of assimilation branches showed a decreasing trend, with the greatest growth rate and final biomass in response to M1. To evaluate the mechanism of the compensatory growth after mowing, a combination of dynamic (0, 1, 5, and 8 days after mowing) plant hormone-targeted metabolomics and transcriptomics was performed for the M0 and M1 treatment. Overall, 26 plant hormone metabolites were detected, 6 of which significantly increased after mowing compared with control: Indole-3-acetyl-L-valine methyl ester, Indole-3-carboxylic acid, Indole-3-carboxaldehyde, Gibberellin A24, Gibberellin A4, and cis (+)-12-oxo-phytodienoic acid. Additionally, 2,402 differentially expressed genes were detected between the mowed plants and controls. By combining clustering analysis based on expression trends after mowing and gene ontology analysis of each cluster, 18 genes related to auxin metabolism were identified, 6 of which were significantly related to auxin synthesis. Our findings suggest that appropriate mowing can promote A. aphylla growth, regulated by the auxin metabolic pathway, and lays the foundation for the development of the industrial value of A. aphylla.

Jet-Origin Identification and Its Application at an Electron-Positron Higgs Factory.

To enhance the scientific discovery power of high-energy collider experiments, we propose and realize the concept of jet-origin identification that categorizes jets into five quark species (b,c,s,u,d), five antiquarks (b[over ¯],c[over ¯],s[over ¯],u[over ¯],d[over ¯]), and the gluon. Using state-of-the-art algorithms and simulated νν[over ¯]H,H→jj events at 240GeV center-of-mass energy at the electron-positron Higgs factory, the jet-origin identification simultaneously reaches jet flavor tagging efficiencies ranging from 67% to 92% for bottom, charm, and strange quarks and jet charge flip rates of 7%-24% for all quark species. We apply the jet-origin identification to Higgs rare and exotic decay measurements at the nominal luminosity of the Circular Electron Positron Collider and conclude that the upper limits on the branching ratios of H→ss[over ¯],uu[over ¯],dd[over ¯] and H→sb,db,uc,ds can be determined to 2×10^{-4} to 1×10^{-3} at 95%confidence level. The derived upper limit for H→ss[over ¯] decay is approximately 3 times the prediction of the standard model.

Skeletonization of open-channels networks - New approaches

Due to the complexity of open-channel networks in which a lengthy procedure is required to understand and analyze their behavior. This paper introduces a methodology for the skeletonization of complex tree-shaped open channel systems. The aim is to aggregate separate branches into one equivalent branch, which has a new skeletonization factor. Three different illustrative examples of river systems using two approaches are analyzed. The software package HEC-RAS is employed to simulate the proposed open channel networks as a one-dimensional steady, gradually varied flow state. Results show that there is a strong correlation between the skeletonization factor required for the equivalent branch and the flow rate of the equivalent branch. The skeletonization factor is also significantly affected by an increase in the ratio of the bed width of each branch canal to that of the main channel in Approach A. The water depth along the main channel has increased more significantly in approach B than in approach A, with average increases of 49.5 %, 29.2 %, and 14.1 % for a number of branches equal to 2, 4, and 6, respectively. Finally, the developed skeletonization concept can be used to represent complex open-channels network models.

Search for a new resonance decaying into two spin-0 bosons in a final state with two photons and two bottom quarks in proton-proton collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV

A search for a new boson X is presented using CERN LHC proton-proton collision data collected by the CMS experiment at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV in 2016–2018, and corresponding to an integrated luminosity of 138 fb−1. The resonance X decays into either a pair of Higgs bosons HH of mass 125 GeV or an H and a new spin-0 boson Y. One H subsequently decays to a pair of photons, and the second H or Y, to a pair of bottom quarks. The explored mass ranges of X are 260–1000 GeV and 300–1000 GeV, for decays to HH and to HY, respectively, with the Y mass range being 90–800 GeV. For a spin-0 X hypothesis, the 95% confidence level upper limit on the product of its production cross section and decay branching fraction is observed to be within 0.90–0.04 fb, depending on the masses of X and Y. The largest deviation from the background-only hypothesis with a local (global) significance of 3.8 (below 2.8) standard deviations is observed for X and Y masses of 650 and 90 GeV, respectively. The limits are interpreted using several models of new physics.

Measurement of simplified template cross sections of the Higgs boson produced in association with W or Z bosons in the H→bb¯ decay channel in proton-proton collisions at s=13 TeV

Differential cross sections are measured for the standard model Higgs boson produced in association with vector bosons (W, Z) and decaying to a pair of b quarks. Measurements are performed within the framework of the simplified template cross sections. The analysis relies on the leptonic decays of the W and Z bosons, resulting in final states with 0, 1, or 2 electrons or muons. The Higgs boson candidates are either reconstructed from pairs of resolved b-tagged jets, or from single large-radius jets containing the particles arising from two b quarks. Proton-proton collision data at s=13 TeV, collected by the CMS experiment in 2016–2018 and corresponding to a total integrated luminosity of 138 fb−1, are analyzed. The inclusive signal strength, defined as the product of the observed production cross section and branching fraction relative to the standard model expectation, combining all analysis categories, is found to be μ=1.15−0.20+0.22. This corresponds to an observed (expected) significance of 6.3 (5.6) standard deviations. © 2024 CERN, for the CMS Collaboration 2024 CERN

Improved analysis of double J/ψ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$J/\\psi $$\\end{document} production in Z-boson decay

In this paper, we present an improved calculation for the decay rate of the rare Z-boson decay into J/ψ+J/ψ.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$J/\\psi + J/\\psi .$$\\end{document} This decay is dominated by the photon fragmentation mechanism, i.e., the transition Z→J/ψ+γ∗\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z\\rightarrow J/\\psi + \\gamma ^{*}$$\\end{document} followed by the fragmentation γ∗→J/ψ.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\gamma ^{*}\\rightarrow J/\\psi .$$\\end{document} In our calculation, the amplitude of γ∗→J/ψ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\gamma ^{*}\\rightarrow J/\\psi $$\\end{document} is extracted from the measured value of Γ(J/ψ→e+e-),\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Gamma (J/\\psi \\rightarrow e^+ e^-),$$\\end{document} and the amplitude of Z→J/ψ+γ∗\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z\\rightarrow J/\\psi + \\gamma ^{*}$$\\end{document} is calculate through the light-cone approach. The higher-order QCD and relativistic corrections in the amplitude of γ∗→J/ψ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\gamma ^{*}\\rightarrow J/\\psi $$\\end{document} and the large logarithms of mZ2/mc2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_{_Z}^2/m_c^2$$\\end{document} that appear in the amplitude of Z→J/ψ+γ∗\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z\\rightarrow J/\\psi + \\gamma ^{*}$$\\end{document} are resummed in our calculation. Besides, the non-fragmentation amplitude is calculated based on the NRQCD factorization, and the next-to-leading order QCD and relativistic corrections are included. The obtained branching fraction for this Z decay channel is 8.66-0.69+1.48×10-11.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$8.66 ^{+1.48} _{-0.69}\ imes 10^{-11}.$$\\end{document}

Production of Xb via radiative transition of ϒ(10753)

We studied the radiative transitions between the ϒ(10753), the S−D mixed state of the ϒ(4S) and ϒ1(3D13), and the Xb, the heavy quark flavor symmetry counterpart of the X(3782) in the bottomonium sector. The radiative transition was assumed to occur through the intermediate bottom mesons, including P-wave B1(′) mesons as well as the S-wave B(*) ones. The consideration of the B1(′) mesons leads to the couplings to be in S-wave, and hence enhances the contributions of the intermediate meson loops. The radiative decay width for the ϒ(10753)→γXb is predicted to be order of 10 keV, corresponding to a branching fraction of 10−4. Based on the theoretical results, we strongly suggest to search for the Xb in the e+e−→γXb with Xb→ππχb1 near s=10.754 GeV, and it is hoped that the calculations here could be tested by the future Belle II experiments. Published by the American Physical Society 2024

Comprehensive Multipath Variational Kinetics Study on Hydrogen Abstraction Reactions from Three Typical Dimethylcyclohexane Isomers by Hydroxyl Radicals: from the Electronic Structure to Model Applications.

Cycloalkanes serve as an important class of chemical components in both fossil and alternative transportation fuels and have attracted considerable attention from the combustion community. Hydrogen abstractions from cycloalkanes by hydroxyl radicals initiate the fuel decomposition process and trigger off the subsequent chain reactions and thus play an important role in both combustion and atmospheric chemistry. The target of this study is to fill the vacancy in kinetics data toward the H-abstraction reactions by hydroxyl radical from three typical dimethylcyclohexane isomers through first-principles and direct dynamics. The rate constants involving 18 elementary reactions in total were accurately determined by the multipath canonical variational transition state theory with the multidimensional small-curvature correction for tunneling (MP-CVT/SCT), over a broad temperature range of 200-2000 K. The significant roles of multistructural torsional anharmonicity and recrossing effects were stressed per abstraction site, while the quantum tunneling effect was found to be slight at temperatures of interest in combustion. The discrepancies observed among different reaction systems at a similar abstraction site highlight the fuel molecular effects on site-specific rate constants. The comparison results of total rate constants given by different dynamics approaches prove the importance of considering the torsional anharmonicity, recrossing, and tunneling effects, and the robust feature of the simplified MS-CVT/SCT. The calculated total constants for dimethylcyclohexane isomers by OH are consistent with those measured for methylcyclohexane and 1,4-dimethylcyclohexane at low temperatures. The branching ratio analysis confirms the predominant role of the tertiary abstraction at low-to-intermediate temperatures and its growing competition with distinct secondary abstractions as temperature increases. The calculated rate constants were eventually fitted into the analytical expressions and incorporated into the kinetic models to learn about the influences on modeling performance.

Product-specific reaction kinetics in continuous uniform supersonic flows probed by chirped-pulse microwave spectroscopy.

Experimental studies of the products of elementary gas-phase chemical reactions occurring at low temperatures (<50K) are very scarce, but of importance for fundamental studies of reaction dynamics, comparisons with high-level quantum dynamical calculations, and, in particular, for providing data for the modeling of cold astrophysical environments, such as dense interstellar clouds, the atmospheres of the outer planets, and cometary comae. This study describes the construction and testing of a new apparatus designed to measure product branching fractions of elementary bimolecular gas-phase reactions at low temperatures. It combines chirped-pulse Fourier transform millimeter wave spectroscopy with continuous uniform supersonic flows and high repetition rate laser photolysis. After a comprehensive description of the apparatus, the experimental procedures and data processing protocols used for signal recovery, the capabilities of the instrument are explored by the study of the photodissociation of acrylonitrile and the detection of two of its photoproducts, HC3N and HCN. A description is then given of a study of the reactions of the CN radical with C2H2 at 30K, detecting the HC3N product, and with C2H6 at 10K, detecting the HCN product. A calibration of these two products is finally attempted using the photodissociation of acrylonitrile as a reference process. The limitations and possible improvements in the instrument are discussed in conclusion.

Evidence of the singly Cabibbo suppressed decay Λc+→pπ0

Evidence for the singly Cabibbo suppressed decay Λc+→pπ0 is reported for the first time with a statistical significance of 3.7σ based on 6.0 fb−1 of e+e− collision data collected at center-of-mass energies between 4.600 and 4.843 GeV with the BESIII detector at the BEPCII collider. The absolute branching fraction of Λc+→pπ0 is measured to be (1.56−0.58+0.72±0.20)×10−4. Combining with the branching fraction of Λc+→nπ+, (6.6±1.3)×10−4, the ratio of the branching fractions of Λc+→nπ+ and Λc+→pπ0 is calculated to be 3.2−1.2+2.2. As an important input for the theoretical models describing the decay mechanisms of charmed baryons, our result indicates that the nonfactorizable contributions play an essential role and their interference with the factorizable contributions should not be significant. In addition, the absolute branching fraction of Λc+→pη is measured to be (1.63±0.31stat±0.11syst)×10−3. Published by the American Physical Society 2024

Thermal decomposition and isomerization of 1-Butyl and 1-Pentyl radical by flash pyrolysis vacuum ultraviolet photoionization time-of-flight mass spectrometry.

Thermal decomposition and isomerization of 1-butyl and 1-pentyl radical were studied in the temperature range of 500-1480 K on a short time scale of 20-100 µs using flash pyrolysis vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry. 1-Bromobutane and 1-bromopentane were used as precursors for the 1-butyl and 1-pentyl radical, respectively. The reactive intermediates in the thermal dissociation reactions were directly observed. The 1-butyl radical decomposed to ethene and ethyl radical with ethyl radical rapidly losing an H atom to form a second ethene molecule. Loss of H atom from butyl radical was also a significant decomposition channel. Isomerization of 1-butyl via 1,3-H migration was observed as a minor channel at 1380 K and above with a branching ratio of less than 3% at 1430 K. The 1-pentyl radical was observed to decompose mainly by isomerization to 2-pentyl radical followed by β-scission to produce propene and ethyl radicals at temperatures approximately 900 K and below. Above 900 K, β-scission of 1-pentyl to produce ethene and 1-propyl radical became increasingly important. Isomerization to 3-pentyl was verified to be a minor channel.

Measurements of the branching fraction ratio Bϕ→μ+μ−/Bϕ→e+e−\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{B}\\left(\\phi \ o {\\mu}^{+}{\\mu}^{-}\\right)/\\mathcal{B}\\left(\\phi \ o {\ extrm{e}}^{+}{\ extrm{e}}^{-}\\right) $$\\end{document} with charm meson decays

Measurements of the branching fraction ratio Bϕ→μ+μ−/Bϕ→e+e−\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{B}\\left(\\phi \ o {\\mu}^{+}{\\mu}^{-}\\right)/\\mathcal{B}\\left(\\phi \ o {e}^{+}{e}^{-}\\right) $$\\end{document} with Ds+→π+ϕ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {D}_s^{+}\ o {\\pi}^{+}\\phi $$\\end{document} and D+→ π+ϕ decays, denoted Rϕπs\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {R}_{\\phi \\pi}^s $$\\end{document} and Rϕπd\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {R}_{\\phi \\pi}^d $$\\end{document}, are presented. The analysis is performed using a dataset corresponding to an integrated luminosity of 5.4 fb−1 of pp collision data collected with the LHCb experiment. The branching fractions are normalised with respect to the B+ → K+J/ψ(→ e+e−) and B+ → K+J/ψ(→ μ+μ−) decay modes. The combination of the results yieldsRϕπ=1.022±0.012stat±0.048syst.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {R}_{\\phi \\pi}=1.022\\pm 0.012\\left(\ extrm{stat}\\right)\\pm 0.048\\left(\ extrm{syst}\\right). $$\\end{document}The result is compatible with previous measurements of the ϕ → ℓ+ℓ− branching fractions and predictions based on the Standard Model.

Energy- and Angle-Resolved Scattering of Ne from Dodecane Liquid Surfaces: Theory Corroborating Experiment.

Motivated by recent experimental work by the Neumark group, we present here an all-atom molecular dynamics study of Ne scattering from a dodecane liquid surface with the objective of elucidating the fundamental aspects of gas-liquid dynamics. Using a fine-tuned force field, the GPU-accelerated simulations reproduced semiquantitatively the energy- and angle-resolved experimental results. The branching ratio between the impulsive scattering (IS) and thermal desorption (TD) channels exhibits a clear correlation with the incidence energy (Ei) and angle. Ne atoms with lower Ei values are more likely to be trapped, yielding an increased TD ratio. For a given Ei, a large incidence angle led to a higher IS ratio. The energy transfer between Ne atoms and liquid dodecane was found to be more sensitive to the deflection angle than to the incidence or reflection angle. With an increasing deflection angle, the fractional energy loss increases, suggesting that more kinetic energy is transferred to the liquid.