Measurement Of Branching Fraction Research Articles

Accessing CKM suppressed top decays at the LHC

We propose an extension of the existing experimental strategy for measuring branching fractions of top quark decays, targeting specifically t\to j_q Wt→jqW, where j_qjq is a light quark jet. The improved strategy uses orthogonal bb- and qq-taggers, and adds a new observable, the number of light-quark-tagged jets, to the already commonly used observable, the fraction of bb-tagged jets in an event. Careful inclusion of the additional complementary observable significantly increases the expected statistical power of the analysis, with the possibility of excluding |V_{tb}|=1|Vtb|=1 at 95\%95% C.L. at the HL-LHC, and accessing directly the standard model value of |V_{td}|^2+|V_{ts}|^2|Vtd|2+|Vts|2.

Non-resonant contributions to three-body D → K (s) π ω decays

Recently, the BESIII collaboration has reported an improved measurement of the branching fraction for D 0 → K − π + ω decay, the first observations and branching fraction measurements for D0→KS0π0ω and D+→KS0π+ω decays with the values of (3.392 ± 0.044 stat ± 0.085 syst )%, (0.848 ± 0.046 stat ± 0.031 syst )%, and (0.707 ± 0.041 stat ± 0.029 syst )%, respectively. In this work, we have obtained the non-resonant amplitudes under the factorization approach. The calculated values for branch ratios are B(D0→K−π+ω)=(3.302±0.195)% , B(D0→KS0π0ω)=(0.782±0.067)% , and B(D+→KS0π+ω)=(0.702±0.111)% which are in good agreement with reported experimental values.

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.

A study of the K+→ π0e+νγ decay

A sample of 1.3 × 105K+ → π0e+νγ candidates with less than 1% background was collected by the NA62 experiment at the CERN SPS in 2017–2018. Branching fraction measurements are obtained at percent relative precision in three restricted kinematic regions, improving on existing results by a factor larger than two. An asymmetry, possibly related to T-violation, is investigated with no evidence observed within the achieved precision.

The DL Advocate: playing the devil’s advocate with hidden systematic uncertainties

We propose a new method based on machine learning to play the devil’s advocate and investigate the impact of unknown systematic effects in a quantitative way. This method proceeds by reversing the measurement process and using the physics results to interpret systematic effects under the Standard Model hypothesis. We explore this idea with two alternative approaches: the first one relies on a combination of gradient descent and optimisation techniques, its application and potentiality is illustrated with an example that studies the branching fraction measurement of a heavy-flavour decay. The second method employs reinforcement learning and it is applied to the determination of the P_{5}^{'} angular observable in B^0 rightarrow K^{*0} {mu ^+mu ^-} decays. We find that for the former, the size of a hypothetical hidden systematic uncertainty strongly depends on the kinematic overlap between the signal and normalisation channel, while the latter is very robust against possible mismodellings of the efficiency.

First observation and branching fraction measurement of the {Lambda}_b^0to {D}_s^{-}p decay

The first observation of the {Lambda}_b^0to {D}_s^{-}p decay is presented using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of sqrt{s} = 13 TeV, corresponding to a total integrated luminosity of 6 fb−1. Using the {Lambda}_b^0to {Lambda}_c^{+}{pi}^{-} decay as the normalisation mode, the branching fraction of the {Lambda}_b^0to {D}_s^{-}p decay is measured to be mathcal{B}left({Lambda}_b^0to {D}_s^{-}pright)=left(12.6pm 0.5pm 0.3pm 1.2right)times {10}^{-6} , where the first uncertainty is statistical, the second systematic and the third due to uncertainties in the branching fractions of the {Lambda}_b^0to {Lambda}_c^{+}{pi}^{-} , {D}_s^{-}to {K}^{-}{K}^{+}{pi}^{-} and {Lambda}_c^{+}to p{K}^{-}{pi}^{+} decays.

Observation of the decay Ds+→ωπ+η

Using 7.33 fb−1 of e+e− collision data collected by the BESIII detector at c.m. energies between 4.128 GeV and 4.226 GeV, we observe for the first time the decay Ds±→ωπ±η with a statistical significance of 7.6σ. The measured branching fraction of this decay is (0.54±0.12±0.04)%, where the first uncertainty is statistical and the second is systematic.Received 9 February 2023Accepted 13 March 2023DOI:https://doi.org/10.1103/PhysRevD.107.052010Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBranching fractionHadronic decaysParticle decaysParticles & Fields

Atomic Transition Probabilities for Transitions of Si i and Si ii and the Silicon Abundances of Several Very Metal-poor Stars ∗ ∗ Based on observations made with the NASA/ESA Hubble Space Telescope (HST), obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. Other data

We report new measurements of branching fractions for 20 UV and blue lines in the spectrum of neutral silicon (Si i) originating in the 3s 23p4s 3Po 1,2,1Po 1, and 3s3p 3 1Do 1,2 upper levels. Transitions studied include both strong, nearly pure LS multiplets as well as very weak spin-forbidden transitions connected to these upper levels. We also report a new branching fraction measurement of the 4P1/2–2Po 1/2,3/2 intercombination lines in the spectrum of singly ionized silicon (Si ii). The weak spin-forbidden lines of Si i and Si ii provide a stringent test on recent theoretical calculations, to which we make comparison. The branching fractions from this study are combined with previously reported radiative lifetimes to yield transition probabilities and log(gf) values for these lines. We apply these new measurements to abundance determinations in five metal-poor stars.

Weak decays of antitriplet charmed baryons from the perspective of flavor symmetry

In this work, we carry out a global fit for the two-body weak decays of antitriplet charmed baryons in both SU(3) respected and broken scenarios incorporating all the available data up to date. In the SU(3) irreducible representation approach (IRA), more amplitudes for irreducible representation terms are taken into account and the ranges for their coefficients in each scenarios are predicted. By a comparison among various fitting schemes in this work, experimental data prefer the SU(3) symmetry breaking scenario. Observables of interest, branching fractions and decay asymmetries of all the Cabibbo-favored (CF), singly Cabibbo-suppressed (SCS) and doubly Cabibbo-suppressed (DCS) channels are calculated in the chosen fitting scheme. Most of our predictions are consistent well with experimental data. We further propose more ways to explore the SU(3) symmetry in charmed baryon decays: (i) A clear measurement of branching fraction on CF mode {Xi}_c^0to {Xi}^0{pi}^0 as a large difference exists between SU(3) respected and broken scenarios. (ii) The decay asymmetries of the five yet-to-be measured CF decay modes, {Xi}_c^0to {Lambda}^0{K}_S , Σ0KS, Ξ0π0, Ξ0η, Ξ0η′, for their opposite signs in the two different cases. (iii) The future measurement on branching fraction ratios indicated from eq. (2.10) and presented on table 7. An improved measurement for alpha left({Lambda}_c^{+}to p{K}_Sright) is called for since predictions from both fittings, including the one in current work and earlier works, and the pole model calculation prefer an opposite sign from previous experimental value. Given branching fractions of most of the CF modes and part of the SCS modes being measured, predictions for the remaining channels, including the DCS modes as well as more decay asymmetries, are anticipated to be checked by the upcoming experiments in BESIII, Belle/Belle-II and LHCb.

Recent results from the NA62 and NA48/2 experiments at CERN

A measurement of the K+→π0e+νγ radiative decay and a search for the K+→π−(π0)e+e+ lepton number violating decays by the NA62 experiment are presented, together with the first observation and branching fraction measurement of the rare decay K+→π0π0μ+ν by the NA48/2 experiment.

A new KS → πeν branching fraction measurement from KLOE-2

The KLOE-2 Collaboration continues the KLOE long-standing tradition of flavour physics precision measurements in the kaon sector with a new KS → πeν branching fraction measurement with 1.63 fb−1 KLOE data acquired at the DAΦNE Frascati ϕ-factory. The strategy to achieve this new result has been presented together with the combination with our previous BR(KS → πeν) measurement, based on an independent data sample, which allows the total precision to be improved by almost a factor of two, and a new derivation of f +(0)|Vus |.

Recent Measurements of Decay Asymmetry Parameter and CP Asymmetry for Charmed Baryon Decays at Belle

We review the recent results from the Belle experiment on the measurements of branching fractions and decay asymmetry parameters (α) for the hadronic weak decays of charmed baryons, including Λc+→B+P: Λc+→(Λ,Σ0)h+ (h=π,K) and Λc+→Σ+(π0,η,η′); Ξc0→B+P: Ξc0→Ξ−π+; Ξc0→B+V: Ξc0→ΛK¯*0, Ξc0→Σ0K¯*0, and Ξc0→Σ+K*−. In addition, we present an overview of the searches for CP violation via the α-induced CP asymmetry for Λc+→(Λ,Σ0)h+ and Ξc0→Ξ−π+. Finally, we discuss the promising decay modes of Ωc0 which can be measured in the near future and are indispensable in searching for CP violation in the charm sector.

Measurement of the branching fraction of the singly Cabibbo-suppressed decay Λc+→ΛK+

We report a branching fraction measurement of the singly Cabibbo-suppressed decay Λc+→ΛK+ using a data sample collected with the BESIII detector at the BEPCII storage ring. The data span center-of-mass energies from 4.599 to 4.950 GeV and correspond to an integrated luminosity of 6.44 fb−1. The branching fraction of Λc+→ΛK+ relative to that of the Cabibbo-favored decay Λc+→Λπ+ is measured to be R=B(Λc+→ΛK+)B(Λc+→Λπ+)=(4.78±0.34±0.20)%. Combining with the world-average value of B(Λc+→Λπ+), we obtain B(Λc+→ΛK+)=(6.21±0.44±0.26±0.34)×10−4. Here the first uncertainties are statistical, the second systematic, and the third comes from the uncertainty of the Λc+→Λπ+ branching fraction. This result, which is more precise than previous measurements, does not agree with theoretical predictions, and suggests that nonfactorizable contributions have been underestimated in current models.Received 9 August 2022Accepted 16 November 2022DOI:https://doi.org/10.1103/PhysRevD.106.L111101Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBranching fractionHadronic decaysParticle decaysPhysical SystemsCharmed baryonsTechniquesPrecision measurementsParticles & Fields

Study of the Semileptonic Decay Λ_{c}^{+}→Λe^{+}ν_{e}.

The study of the Cabibbo-favored semileptonic decay Λ_{c}^{+}→Λe^{+}ν_{e} is reported using a 4.5 fb^{-1} data sample of e^{+}e^{-} annihilations collected at center-of-mass energies ranging from 4.600GeV to 4.699GeV with the BESIII detector at the BEPCII collider. The branching fraction of the decay is measured to be B(Λ_{c}^{+}→Λe^{+}ν_{e})=(3.56±0.11_{stat}±0.07_{syst})%, which is the most precise measurement to date. Furthermore, we perform an investigation of the internal dynamics in Λ_{c}^{+}→Λe^{+}ν_{e}. We provide the first direct comparisons of the differential decay rate and form factors with those predicted from lattice quantum chromodynamics (LQCD) calculations. Combining the measured branching fraction with a q^{2}-integrated rate predicted by LQCD, we determine |V_{cs}|=0.936±0.017_{B}±0.024_{LQCD}±0.007_{τ_{Λ_{c}}}.

Pursuit of new physics within the Lambda _crightarrow Delta K decays

We point out the CP asymmetry in the chain decay of Lambda _c^+rightarrow Delta ^+K(t)(rightarrow pi ^+pi ^-) is determined by the branching fractions of Lambda ^+_crightarrow Delta ^{++} K^-, Lambda ^+_crightarrow Delta ^{+} K^0_{S,L} and Lambda ^+_crightarrow Delta ^{0} K^+ modes under the isospin symmetry. The ambiguities from loop-induced quantities and SU(3)_F breaking hadronic effects are avoided. Once the CP asymmetry in the Lambda _c^+ decays into Delta ^+ and neutral kaons is confirmed by experiments, we can check if it is beyond the Standard Model, or verify the CP-violating effect resulted from the interference between the Cabibbo-favored and the doubly Cabibbo-suppressed amplitudes with the neutral kaon mixing. Future measurements of branching fractions play a critical role in reducing the uncertainties.

Hadronic Decays of Charmed Hadrons at BESIII

The BESIII experiment has collected the e+e− collision data samples corresponding to integrated luminosities of 2.93fb−1, 3.19fb−1, 3.13fb−1 and 567pb−1 at center-of-mass energies of 3.773 GeV, 4.178 GeV, 4.189–4.226 GeV and 4.599 GeV, respectively. We report the measurements of strong-phase parameters based on the decays D0→KS/L0π+π−, D0→KS/L0K+K−, D0→K−π+π+π− and D0→K−π+π0, which are important input for binned model-independent measurement of the CKM angle γ/ϕ3. In addition, we report amplitude analyses and branching fraction measurements of D+, Ds+ and Λc+ decays along with the Λc+ spin determination.

Weak radiative hyperon decays in covariant baryon chiral perturbation theory

Weak radiative hyperon decays, important to test the strong interaction and relevant in searches for beyond the standard model physics, have remained puzzling both experimentally and theoretically for a long time. The recently updated branching fraction and first measurement of the asymmetry parameter of Λ→nγ by the BESIII Collaboration further exacerbate the issue, as none of the existing predictions can describe the data. We show in this work that the covariant baryon chiral perturbation theory, with constraints from the latest measurements of hyperon non-leptonic decays, can well describe the BESIII data. The predicted branching fraction and asymmetry parameter for Ξ-→Σ-γ are also in agreement with the experimental data. We note that a more precise measurement of the asymmetry parameter, which is strongly constrained by chiral symmetry and related with that of Σ+→pγ, is crucial to test Hara’s theorem. We further predict the branching fraction and asymmetry parameter of Σ0→nγ, whose future measurement can serve as a highly nontrivial check on our understanding of weak radiative hyperon decays and on the covariant baryon chiral perturbation theory.

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})%.

Amplitude analysis and branching fraction measurement of the decay {D}_s^{+} → K+π+π−

Using 6.32 fb−1 of e+e− collision data collected at the center-of-mass energies between 4.178 and 4.226 GeV with the BESIII detector, we perform an amplitude analysis of the decay {D}_s^{+} → K+π+π− and determine the amplitudes of the various intermediate states. The absolute branching fraction of {D}_s^{+} → K+π+π− is measured to be (6.11 ± 0.18stat.± 0.11syst.) × 10−3. The branching fractions of the dominant intermediate processes {D}_s^{+} → K+ρ0, ρ0→ π+π− and {D}_s^{+} → K*(892)0π+, K*(892)0→ K+π− are determined to be (1.96 ± 0.19stat.± 0.23syst.) × 10−3 and (1.85 ± 0.12stat.± 0.13syst.) × 10−3, respectively. The intermediate resonances f0(500), f0(980), and f0(1370) are observed for the first time in this channel.

Amplitude analysis and branching fraction measurement of {D}_s^{+} → K−K+π+π+π−

Using e+e− annihilation data corresponding to a total integrated luminosity of 6.32 fb−1 collected at the center-of-mass energies between 4.178 and 4.226 GeV with the BESIII detector, we perform an amplitude analysis of the decay {D}_s^{+} → K−K+π+π+π− and determine the relative fractions and phases of different intermediate processes. Absolute branching fraction of {D}_s^{+} → K−K+π+π+π− decay is measured to be (6.60 ± 0.47stat.± 0.38syst.) × 10−3. The dominant intermediate process is {D}_s^{+} → a1(1260)+ϕ, ϕ → K−K+, a1(1260)+→ ρπ+, ρ → π+π−, with a branching fraction of (5.15 ± 0.41stat.± 0.32syst.) × 10−3.