Measurement Of Branching Ratio Research Articles

Neutral-pion decay into an electron-positron pair: A review and update

This work aims to review several aspects of the current status of the rare π0→e+e− decay. A particular emphasis is made on radiative corrections and detailed interpretation of related quantities, some numbers appearing in the literature are updated, and the connection with the Dalitz decay, π0→e+e−γ, is discussed. This comes timely as it is aligned with an announcement of a preliminary result of a new branching-ratio measurement done by the NA62 Collaboration, which brings new light into an earlier-reported discrepancy between the Standard Model prediction and the (until-recently latest) precise KTeV result. Published by the American Physical Society 2024

Clarifying the radiative decay of the Hoyle state with charged-particle spectroscopy

A detailed knowledge of the decay properties of the so called Hoyle state in the 12\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{12}$$\\end{document}C nucleus (Ex=7.654\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E_x=7.654$$\\end{document} MeV, 0+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$0^+$$\\end{document}) is required to calculate the rate at which carbon is forged in typical red-giant stars. This paper reports on a new almost background-free measurement of the radiative decay branching ratio of the Hoyle state using advanced charged particle coincidence techniques. The exploitation, for the first time in a similar experiment, of a bidimensional map of the coincidence efficiency allows to reach an unitary value and, consequently, to strongly reduce sources of systematic uncertainties. The present results suggest a value of the radiative branching ratio of Γrad/Γtot=4.2(6)·10-4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Gamma _{rad}/\\Gamma _{tot}=4.2(6)\\cdot 10^{-4}$$\\end{document}. This finding helps to resolve the tension between recent data published in the literature.

Direct Observation of Competing M1 and M3 Transitions in ^{10}B.

Excited states in ^{10}B were populated with the ^{10}B(p,p^{'}γ)^{10}B^{*} reaction at 8.5MeV and their γ decay was investigated via coincidence γ-ray spectroscopy. The emitted γ rays were measured using large-volume LaBr_{3}:Ce and CeBr_{3} detectors placed in anti-Compton shields. This allowed the observation of weak γ-ray transitions, such as the M3 transition between the J^{π},T=0^{+},1 isobaric analog state (IAS) and the J^{π},T=3^{+},0 ground state and the E2 transition between the J^{π},T=2_{1}^{+},0 state and the IAS, i.e., performing measurements of branching ratios at the level of λ≥10^{-4}. For the first time in ^{10}B, the competing M1 and M3 transitions from the decay of the IAS have been observed in a γ spectroscopy experiment. The experimental results are compared with abinitio no-core shell model calculation using the newest version of the local position-space chiral N^{3}LO nucleon-nucleon interaction. The calculations reproduce correctly the ordering of the bound states in ^{10}B, and are in reasonable agreement with the observed branching ratios and reduced transition probabilities.

Direct Measurement of Charge Transfer Probability during Photodissociation of Few-keV OD+ Beam.

We have measured the photodissociation of few-keV OD+ molecular ions into either D+ + O or O+ + D final products. The three-dimensional momentum imaging measurements of the light and massive fragments in coincidence were enabled by using an upgraded two-detector setup. In this work, we show that absorption of a single 790 or 395 nm photon excites the OD+ from its electronic ground state to the B state, which dissociates to the O+(4S) + D dissociation limit. To reach the other nearly degenerate dissociation limit, D+ + O(3P), a unimolecular charge transfer, B to X , transition is required following the same photoexcitation. The measured branching ratio of these dissociation channels is a direct measure of the charge transfer transition probability. This measured probability as a function of energy above the dissociation limit agrees well with our calculations.

Measurement of the production branching ratios following nuclear muon capture for palladium isotopes using the in-beam activation method

Measurement of the production branching ratios following nuclear muon capture for palladium isotopes using the in-beam activation method

Measuring hadronic Higgs boson branching ratios at future lepton colliders

We present a novel strategy for the simultaneous measurement of Higgs-boson branching ratios into gluons and light quarks at a future lepton collider operating in the Higgs-factory mode. Our method is based on template fits to global event-shape observables, and in particular fractional energy correlations, thereby exploiting differences in the QCD radiation patterns of quarks and gluons. In a constrained fit of the deviations of the light-flavour hadronic Higgs-boson branching ratios from their Standard Model expectations, based on an integrated luminosity of 5ab-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$5\\,\ ext {ab}^{-1}$$\\end{document}, we obtain 68%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$68\\%$$\\end{document} confidence level limits of μgg=1±0.05\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu _{gg}=1 \\pm 0.05$$\\end{document} and μqq¯<21\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu _{q\\bar{q}}<21$$\\end{document}.

Radiative Decay Branching Ratio of the Hoyle State in 12C via Charged Particle Coincidence Techniques

The properties of the Hoyle state in 12C (7.654 MeV, 0+) affect the rate at which carbon, one of the most abundant elements in the Universe, is forged in stars. Recent experiments reported values of its radiative decay branching ratio that are in tension, posing major implications especially in the astrophysical domain. This work reports on an almost background-free measurement of the radiative decay branching ratio of the Hoyle state that exploits charged particle coincidence techniques. The experiment adopts several methodologies to minimize the background and identify the rare signal associated with the radiative decay. Large care is devoted to having under full control two of the major sources of systematic errors in particle-coincidence experiments: the coincidence efficiency and the spurious coincidence rate. We find a radiative decay branching ratio of Γrad/Γtot = 4.2(6) · 10−4. The new finding helps to resolve the tension between recent data published in the literature.

Recent results from the NA62 experiment at CERN

The NA62 experiment at CERN collected the world's largest data set of charged kaon decays in 2016-2018, leading to the most precise measurement of the branching fraction of the ultra-rare K+→π+νν‾ decay, based on 20 candidates. This provides evidence for the observation of the K+→π+νν‾ decay with a significance of 3.4σ. This measurement is also used to set limits on B(K+→π+X), where X is a scalar or pseudo-scalar particle. The analysis of the full 2016-2018 data sample is reviewed. More recent results from NA62 analyses of K+→π0e+νγ, K+→π+μ+μ− and K+→π+γγ decays, using data samples recorded in 2017–2018, are also reported. The radiative kaon decay K+→π0e+νγ (Ke3γ) is studied with a data sample of O(100k) Ke3γ candidates with sub-percent background contamination. Final results of the most precise measurements of the Ke3γ branching ratios and T-asymmetry are presented. The K+→π+μ+μ− sample comprises about 27k signal events with negligible background contamination, and the results presented include the most precise determination of the branching fraction and the decay form factor. The K+→π+γγ sample contains about 4k signal events with 10% background contamination, and the preliminary analysis results improve the precision of the branching fraction measurement by a factor of 3 with respect to previous measurements. An overview of the latest NA62 results and future prospects for the experiment is presented.

More synergies from beauty, top, Z and Drell-Yan measurements in SMEFT

We perform a global analysis of Beauty, Top, Z and Drell-Yan measurements in the framework of the Standard Model effective theory (SMEFT). We work within the minimal flavor violation (MFV) hypothesis, which relates different sectors and generations beyond the SU(2)L-link between left-handed top and beauty quarks. We find that the constraints on the SMEFT Wilson coefficients from the combined analysis are stronger than the constraints from a fit to the individual sectors, highlighting synergies in the global approach. We also show that constraints within MFV are strengthened compared to single-generation fits. The strongest bounds are obtained for the semileptonic four-fermion triplet operator Clq3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {C}_{lq}^{(3)} $$\\end{document}, probing scales as high as 18 TeV, followed by the gluon dipole operator CuG with 7 TeV, and other four-fermion and penguin operators in the multi-TeV range. Operators with left-handed quark bilinears receive order one contributions from higher orders in the MFV expansion induced by the top Yukawa coupling as a result of the FCNC b → sμμ anomalies combined with the other sectors. We predict the 68% credible intervals of the dineutrino branching ratios within MFV as 4.25⋅10−6≤BB0→K∗0νν¯≤11.13⋅10−6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ 4.25\\cdot {10}^{-6}\\le \\mathcal{B}\\left({B}^0\ o {K}^{\\ast 0}\ u \\overline{\ u}\\right)\\le 11.13\\cdot {10}^{-6} $$\\end{document} and 2.26⋅10−6≤BB+→K+νν¯≤5.78⋅10−6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ 2.26\\cdot {10}^{-6}\\le \\mathcal{B}\\left({B}^{+}\ o {K}^{+}\ u \\overline{\ u}\\right)\\le 5.78\\cdot {10}^{-6} $$\\end{document}, which include the respective Standard Model predictions, and are in reach of the Belle II experiment. We show how future measurements of the dineutrino branching ratios can provide insights into the structure of new physics in the global fit.

Study of four-body decays B(s)→(ππ)(ππ)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)} \\rightarrow (\\pi \\pi )(\\pi \\pi )$$\\end{document} in the perturbative QCD approach

In this work, we make a systematical study on the four-body B(s)→(ππ)(ππ)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)} \\rightarrow (\\pi \\pi )(\\pi \\pi )$$\\end{document} decays in the perturbative QCD (PQCD) approach, where the ππ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi \\pi $$\\end{document} invariant mass spectra are dominated by the vector resonance ρ(770)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rho (770)$$\\end{document} and the scalar resonance f0(980)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$f_0(980)$$\\end{document}. We improve the Gengenbauer moments for the longitudinal P-wave two-pion distribution amplitudes (DAs) by fitting the PQCD factorization formulas to measured branching ratios of three-body and four-body B decays. With the fitted Gegenbauer moments, we make predictions for the branching ratios and direct CP asymmetries of four-body B(s)→(ππ)(ππ)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)} \\rightarrow (\\pi \\pi )(\\pi \\pi )$$\\end{document} decays. As a by-product, we extract the branching ratios of two-body B(s)→ρρ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)} \\rightarrow \\rho \\rho $$\\end{document} from the corresponding four-body decay modes and calculate the relevant polarization fractions. We find that the B(B0→ρ+ρ-)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{B}(B^0 \\rightarrow \\rho ^+\\rho ^-)$$\\end{document} is consistent with the previous theoretical predictions and data. The leading-order PQCD calculations of the B(B+→ρ+ρ0)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{B}(B^+\\rightarrow \\rho ^+\\rho ^0)$$\\end{document}, B(B0→ρ0ρ0)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{B}(B^0\\rightarrow \\rho ^0\\rho ^0)$$\\end{document} and the f0(B0→ρ0ρ0)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$f_0(B^0\\rightarrow \\rho ^0\\rho ^0)$$\\end{document} are a bit lower than the experimental measurements, which should be further examined. It is shown that the direct CP asymmetries are large when both tree and penguin contributions are comparable to each other, but small for the tree-dominant or penguin-dominant processes. In addition to the direct CP asymmetries, the “true” and “fake” triple-product asymmetries (TPAs) originating from the interference among various helicity amplitudes in the B(s)→(ππ)(ππ)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)}\\rightarrow (\\pi \\pi )(\\pi \\pi )$$\\end{document} decays are also analyzed. The sizable averaged TPA AT-true1,ave=25.26%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{A}_{\ ext {T-true}}^{1, \ ext {ave}}=25.26\\%$$\\end{document} of the color-suppressed decay B0→ρ0ρ0→(π+π-)(π+π-)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B^0\\rightarrow \\rho ^0\\rho ^0 \\rightarrow (\\pi ^+\\pi ^-)(\\pi ^+\\pi ^-)$$\\end{document} is predicted for the first time, which deviates a lot from the so-called “true” TPA AT-true1=7.92%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal {A}_\ ext {T-true}^1=7.92\\%$$\\end{document} due to the large direct CP violation. A large “fake” TPA AT-fake1=24.96%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal {A}_\ ext {T-fake}^1=24.96\\%$$\\end{document} of the decay B0→ρ0ρ0→(π+π-)(π+π-)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B^0\\rightarrow \\rho ^0\\rho ^0 \\rightarrow (\\pi ^+\\pi ^-)(\\pi ^+\\pi ^-)$$\\end{document} is also found, which indicates the significance of the final-state interactions. The predictions in this work can be tested by LHCb and Belle-II experiments in the near future.

^{133}In: A Rosetta Stone for Decays of r-Process Nuclei.

The β decays from both the ground state and a long-lived isomer of ^{133}In were studied at the ISOLDE Decay Station (IDS). With a hybrid detection system sensitive to β, γ, and neutron spectroscopy, the comparative partial half-lives (logft) have been measured for all their dominant β-decay channels for the first time, including a low-energy Gamow-Teller transition and several first-forbidden (FF) transitions. Uniquely for such a heavy neutron-rich nucleus, their β decays selectively populate only a few isolated neutron unbound states in ^{133}Sn. Precise energy and branching-ratio measurements of those resonances allow us to benchmark β-decay theories at an unprecedented level in this region of the nuclear chart. The results show good agreement with the newly developed large-scale shell model (LSSM) calculations. The experimental findings establish an archetype for the β decay of neutron-rich nuclei southeast of ^{132}Sn and will serve as a guide for future theoretical development aiming to describe accurately the key β decays in the rapid-neutron capture (r-) process.

A new puzzle in non-leptonic B decays

We build a set of new observables using closely related non-leptonic penguin-mediated Bd and Bs decays: {overline{B}}_{d,s}to {K}^{ast 0}{overline{K}}^{ast 0},{overline{B}}_{d,s}to {K}^0{overline{K}}^0,{overline{B}}_{d,s}to {K}^0{overline{K}}^{ast 0} and {overline{B}}_{d,s}to {overline{K}}^0{K}^{ast 0} together with their CP conjugate partners. These optimised observables are designed to reduce hadronic uncertainties, mainly coming from form factors and power-suppressed contributions, and thus maximize their sensitivity to New Physics (NP). The deviations observed with respect to the Standard Model (SM) in the ratios of branching ratios of {overline{B}}_{d,s}to {K}^{ast 0}{overline{K}}^{ast 0}left(2.6sigma right) and {overline{B}}_{d,s}to {K}^0{overline{K}}^0left(2.4sigma right) can be explained by simple NP scenarios involving the Wilson coefficients mathcal{C} 4 and mathcal{C} 6 associated with QCD penguin operators and the coefficient mathcal{C} 8g of the chromomagnetic operator. The optimised observables for {overline{B}}_{d,s}to {K}^0{overline{K}}^{ast 0} and {overline{B}}_{d,s}to {overline{K}}^0{K}^{ast 0} show distinctive patterns of deviations with respect to their SM predictions under these NP scenarios. The pattern of deviations of individual branching ratios, though affected by significant hadronic uncertainties, suggests that NP is needed both in b → d and b → s transitions. We provide the regions for the Wilson coefficients consistent with both optimised observables and individual branching ratios. The NP scenarios considered to explain the deviations of {overline{B}}_{d,s}to {K}^{ast 0}{overline{K}}^{ast 0} and {overline{B}}_{d,s}to {K}^0{overline{K}}^0 can yield deviations up to an order of magnitude among the observables that we introduced for {overline{B}}_{d,s}to {K}^0{overline{K}}^{ast 0} and {overline{B}}_{d,s}to {overline{K}}^0{K}^{ast 0} . Probing these new observables experimentally by improving the measurements of individual branching ratios of penguin-mediated decays would confirm the consistency of the deviations already observed and provide a highly valuable hint of NP in the non-leptonic sector.

Measurement of the very rare decay at the NA62 experiment

The decay, with a very precisely predicted branching ratio of less than 10−10, is among the best processes to reveal indirect effects of new physics. The NA62 experiment reports the branching ratio measurement BR() = ± 0.009| syst ) · 10−10 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 decay, observed with a significance of 3.4σ. This measurement is also used to set limits on BR(K + → π +X), where X is a new feebly interacting scalar or pseudo-scalar particle, foreseen in several new physics scenarios.

Measurements on the production and properties of light hypernuclei at STAR

The hyperon-nucleon (Y-N) interaction, an important ingredient for the nuclear equation-of-state (EoS), remains poorly constrained. Precise measurements of hypernucei intrinsic properties and production yields in heavy-ion collisions are crucial for the understanding of their production mechanisms and the strength of the Y-N interaction. Thanks to the high statistics data taken from the STAR BES II program, a series of hypernuclei measurements are carried out at low energies. In these proceedings, we present the kinematic and centrality dependence of light hypernuclei production yields and strangeness population factor (S3, S4) in Au+Au collisions at √SNN = 3 GeV. We also report the energy dependence of Λ3H yields and S3 at mid-rapidity from 3 to 27 GeV Au+Au collisions. Precise measurements of Λ4He lifetime and Λ3H branching ratio are also reported. These results are compared with model calculations and physics implications are discussed.

Fine-structure branching ratios N(2D5/2)/N(2D3/2) above threshold N(2D5/2.3/2)+N(2D5/2.3/2) for 14N2 and 15N2

Accurate measurements of the product spin-orbit finne-structure branching ratios are important for understanding the detailed photodissociation dynamics of small molecules. In this study, the atomic spin-orbit fine-structure branching rar tio N(2D5/2)/N(2D3/2) to the dissociation channel N(2D5/2,3/2)+N(2D5/2,3/2) is measured for the c4′1Σu+(υ′=6) and b′1Σu+(υ′=21) states of 14N2, and the b′1Σu+(υ′=20) and b′1Σu+(υ′=21) states of 15N2 by using the vacuum ultraviolet (VUV)pump VUV-probe time-sliced velocity-mapped ion imaging setup. The measurements show that the fine-structure branching ratio N(2D5/2)/N(2D3/2) is independent of the rotational level of the parent molecule (14N2 or 15N2) in each vibronic state, while it does show dependence on the vibronic characteristics. It is ~1.35 for the c4′1Σu+(υ′=6) state of 14N2 and b′1Σu+(υ′=20) state of 15N2, which are both close to the dissociation threshold N(2D5/2,3/2)+N(2D5/2,3/2); while it becomes ~1.00 for the b′1Σu+(υ′=21) state of both 14N2 and 15N2, which are relatively far above the dissociation threshold. A possible change from a statistical process near the threshold to a diabatic process far above the threshold might have occurred to be responsible for the observed vibronic dependence of the branching ratio. Detailed informations on the potential energy curves and their mutual couplings near the dissociation threshold are highly desired for understanding the present experimental measurement.

Flavored axions and the flavor problem

A Peccei-Quinn (PQ) symmetry is proposed, in order to generate in the Standard Model (SM) quark sector a realistic mass matrix ansatz with five texture-zeros. Limiting our analysis to Hermitian mass matrices we show that this requires a minimum of 4 Higgs doublets. This model allows assigning values close to 1 for several Yukawa couplings, giving insight into the origin of the mass scales in the SM. Since the PQ charges are non-universal the model features Flavor-Changing Neutral Currents (FCNC) at the tree level. From the analytical expressions for the FCNC we report the allowed region in the parameter space obtained from the measurements of branching ratios of semileptonic meson decays.

One-loop corrections to the Higgs boson invisible decay in a complex singlet extension of the SM

The search for dark matter (DM) at colliders is founded on the idea of looking for something invisible. There are searches based on production and decay processes where DM may reveal itself as missing energy. If nothing is found, our best tool to constrain the parameter space of many extensions of the Standard Model (SM) with a DM candidate is the Higgs boson. As the measurements of the Higgs couplings become increasingly precise, higher-order corrections will start to play a major role. The tree-level contribution to the invisible decay width provides information about the portal coupling. Higher-order corrections also give us access to other parameters from the dark sector of the Higgs potential that are not present in the tree-level amplitude. In this work we will focus on the complex singlet extension of the SM in the phase with a DM candidate. We calculate the one-loop electroweak corrections to the decay of the Higgs boson into two DM particles. We find that the corrections are stable and of the order of a few percent. The present measurement of the Higgs invisible branching ratio, $\mathrm{BR}(H\ensuremath{\rightarrow}\text{ }\mathrm{invisible})&lt;0.11$, already constrains the parameter space of the model at leading order. We expect that by the end of the LHC the experimental measurement will require the inclusion of the electroweak corrections to the decay in order to match the experimental accuracy. Furthermore, the only competing process, which is direct detection, is shown to have a cross section below the neutrino floor.

Study of B(s)0→ϕϕ→(K+K−)(K+K−) decays in the perturbative QCD approach

In this work, we make a detailed analysis on the penguin-dominant processes $B_{(s)}^0 \to \phi\phi \to (K^+K^-)(K^+K^-)$ in the perturbative QCD (PQCD) approach. In addition to the dominant $P$-wave resonance, the scalar background $f_0(980) \to K^+K^-$ is also accounted for. We improve the Gegenbauer moments in $KK$ two-meson distribution amplitudes by fitting the PQCD factorization formulas to measured branching ratios of three-body and four-body $B$ decays. We extract the branching ratios of two-body $B_{(s)}^0 \to \phi\phi$ decays from the corresponding four-body decay modes and calculate the relevant polarization fractions together with two relative phases $\phi_{\parallel,\perp}$, which are consistent with the previous theoretical predictions. The PQCD predictions for the "true" triple product asymmetries (TPAs) are zero which are expected in the standard model due to the vanishing weak phase difference, and support the current data reported by the CDF and LHCb Collaborations. A large "fake" TPA $\mathcal{A}_\text{T-fake}^1=30.4\%$ of the decay $B^0_s \to \phi\phi \to (K^+K^-)(K^+K^-)$ is predicted for the first time, which indicates the presence of the significant final-state interactions. The TPAs of the rare decay channel $B^0 \to \phi\phi\to (K^+K^-)(K^+K^-)$ are also predicted and can be tested in the near future.

Exploring strange origin of Dirac neutrino masses at hadron colliders

We consider the possibility that Dirac neutrino masses may be a manifestation of chiral symmetry breaking via nonperturbative QCD dynamics. The key role played by light quarks in this mechanism can naturally lead to signals that are accessible to hadron colliders. Bounds from charged meson decays imply a dominant effect from the strange quark condensate. We propose a model for Dirac neutrino mass generation with an extra Higgs doublet at the TeV scale and significant coupling to strange quarks and leptons. Current data on $D\ensuremath{-}\overline{D}$ mixing constrain the allowed parameter space of the model, and a 100 TeV $pp$ collider would either discover or largely exclude it. A distinct feature of this scenario is that measurements of the charged Higgs leptonic branching ratios can distinguish between ``normal'' and ``inverted'' neutrino mass hierarchies, complementing future determinations at neutrino oscillation experiments.

Electromagnetic Dalitz decays of decuplet to octet with the SU(3) flavor symmetry/breaking

Motivated by the first measured Δ+→pe+e− decay by the HADES Collaboration, electromagnetic Dalitz baryon decays from the spin 32 decuplet (T10) to the spin 12 octet (T8) baryons are investigated by using the SU(3) flavor symmetry/breaking in this paper. All decay amplitudes of T10→T8ℓ+ℓ−(ℓ=e,μ) electromagnetic Dalitz decays could be related by the SU(3) flavor symmetry/breaking, so the amplitudes can be obtained by the measured branching ratio of Δ+→pe+e− decay from the HADES Collaboration. The branching ratios, the lepton flavor universality, and the ratios B(T10→T8ℓ+ℓ−)B(T10→T8γ) are predicted by the relevant experimental data. T10→T8μ+μ− electromagnetic Dalitz decays are studied for the first time. All predicted B(T10→T8ℓ+ℓ−) except B(Ξ⁎0→Ξ0μ+μ−) and B(Ξ⁎−→Ξ−μ+μ−) are on the order of O(10−5−10−7), and these decays could be observed and could be used to test the SU(3) flavor symmetry/breaking approach in the electromagnetic Dalitz decays by HADES, PANDA, BESIII, and other experiments in the near future.