Engineering topics
Publications and source records attributed to Hedges, M. T. (ORCID:0000000165041872).
We report the results of the first search for the decay B$^{0}_{s}$ → π 0 π 0 using 121.4 fb -1 of data collected at the Y(5S) resonance with the Belle detector at the KEKB asymmetric-energy e + e - collider. We observe no signal and set a 90% confidence level upper limit of 7.7 ×10 -6 on the B$^{0}_{s}$ → π 0 π 0 decay branching fraction.
We measure the ratio of branching fractions for the $\Upsilon$ (4S) decays to B + B - and B 0 $\bar{B}$ 0 using B + → J/Ψ($\ell\ell$)K + and B 0 → J/Ψ($\ell\ell$)K 0 samples, where J/Ψ($\ell\ell$) stands for J/Ψ → $\ell$ + $\ell$ - ($\ell$ = e or μ), with 711 fb -1 of data collected at the $\Upsilon$ (4S) resonance with the Belle detector. We find the decay rate ratio of $\Upsilon$ (4S) → B + B - over $\Upsilon$ (4S) → B 0 $\bar{B}$ 0 to be 1.065 ± 0.012 ± 0.019 ± 0.047, which is the most precise measurement to date. The first and second uncertainties are statistical and systematic, respectively, and the third uncertainty is due to the assumption of isospin symmetry in B → J/Ψ($\ell\ell$) K.
Here, we report a study of Λ$^+_c$ → Λ h + and Λ$^+_c$ → Σ 0 h + ( h = K, π ) decays based on a data sample of 980 fb -1 collected with the Belle detector at the KEKB energy-asymmetric e + e - collider. The first results of direct CP asymmetry in two-body singly Cabibbo-suppressed (SCS) decays of charmed baryons are measured, A$^{dir}_{CP}(Λ^+_{c} → ΛK^{+})$ = +0.021 ± 0.026 ± 0.001 and A$^{dir}_{CP}(Λ^+_{c} → Σ^{0}K^{+})$ = +0.025 ± 0.054 ± 0.004. We also make the most precise measurement of the decay asymmetry parameters (α) for the four modes of interest and search for CP violation via the α-induced CP asymmetry (A$^α_{CP}$ ). We measure A$^α_{CP}$ ($Λ^+_{c} → ΛK^{+}$) = -0.023 ± 0.086 ± 0.071 and A$^α_{CP}$ ($Λ^+_{c} → Σ^{0}K^{+}$) = +0.08 ± 0.35 ± 0.14, which are the first A$^α_{CP}$ results for SCS decays of charmed baryons. We search for Λ -hyperon CP violation in $Λ^+_{c}$ → (Λ, Σ 0 )π + and find A$^α_{CP}$(Λ → pπ - ) = +0.013 ± 0.007 ± 0.011 . This is the first time that hyperon CP violation has been measured via Cabibbo-favored charm decays. No evidence of baryon CP violation is found. We also obtain the most precise branching fractions for two SCS Λ$^+_c$ decays, $\mathscr{B}$($Λ^+_{c} → ΛK^{+}$) = (6.57 ± 0.17 ± 0.11 ± 0.35) x 10 -4 and $\mathscr{B}$($Λ^+_{c} → Σ^{0}K^{+}$) = (3.58 ± 0.19 ±0.06 ±0.19) x 10 -4 . The first uncertainties are statistical and the second systematic, while the third uncertainties come from the uncertainties on the world average branching fractions of $Λ^+_{c}$ → (Λ, Σ 0 )π + .
Using the entire data sample of 980 fb -1 collected at or near the Y(4S) resonance with the Belle detector operating at the KEKB asymmetric-energy e + e - collider, we report the measurement of the mass, width, and the branching ratios of the Λ c (2625) + charmed baryon. The mass difference between Λ c (2625) + and Λ$^{+}_{c}$ is measured to be M(Λ c (2625) + )-M(Λ$^{+}_{c}$)=341.518±0.006±0.049 MeV/c 2 . The upper limit on the width is measured to be Γ(Λ c (2625) + )<0.52 MeV/c 2 at 90% confidence level. Based on a full Dalitz plot fit, branching ratios with respect to the mode Λ c (2625) + →Λ$^{+}_{c}$π + π - are measured to be $\frac{\mathscr{B}(Λ_c(2625)^+ → Σ^{0}_{c}π^+)} {\mathscr{B}(Λ_c(2625)^+ → ^{+}_{c}π^+π^-)}$ = (5.19±0.23±0.40)% and $\frac{\mathscr{B}(Λ_c (2625)^+ → Σ{_c^+}^+ π^-)}{\mathscr{B}(Λ_c (2625)^+ → Λ{_c^+} π^+π^-)}$ = (5.13±0.26±0.32)%, where the first and second uncertainties are statistical and systematic, respectively. These measurements can be used to further constrain the parameters of the underlying theoretical models.
We present a study of a singly Cabibbo-suppressed decay Λ$^+_c$ → pK$^0_S$K$^0_S$ and a Cabibbo-favored decay Λ$^+_c$ → pK$^0_S$η based on 980 fb -1 of data collected by the Belle detector, operating at the KEKB energy-asymmetric e + e - collider. We measure their branching fractions relative to Λ$^+_c$ → pK$^0_S$: $\mathscr{B}$(Λ$^+_c$ → pK$^0_S$K$^0_S$)/$\mathscr{B}$(Λ$^+_c$ → pK$^0_S$) = (1.48 ± 0.08 ± 0.04) × 10 -2 and $\mathscr{B}$(Λ$^+_c$ → pK$^0_S$η)/$\mathscr{B}$(Λ$^+_c$ → pK$^0_S$) = (2.73 ± 0.06 ± 0.13) × 10 -1 . Combining with the world average $\mathscr{B}$(Λ$^+_c$ → pK$^0_S$), we have the absolute branching fractions, $\mathscr{B}$(Λ$^+_c$ → pK$^0_S$K$^0_S$) = (2.35 ± 0.12 ± 0.07 ± 0.12) × 10 -4 and $\mathscr{B}$(Λ$^+_c$ → pK$^0_S$η) = (4.35 ± 0.10 ± 0.20 ± 0.22) × 10 -3 . The first and second uncertainties are statistical and systematic, respectively, while the third ones arise from the uncertainty on $\mathscr{B}$(Λ$^+_c$ → pK$^0_S$). The mode Λ$^+_c$ → pK$^0_S$K$^0_S$ is observed for the first time and has a statistical significance of >10σ. The branching fraction of Λ$^+_c$ → pK$^0_S$η has been measured with a threefold improvement in precision over previous results and is found to be consistent with the world average.
Based on a data sample of 983 fb -1 collected with the Belle detector at the KEKB asymmetric-energy e + e - collider, we present the study of the heavy-flavor-conserving decay Ξ$^{0}_{c}$ → Λ$^{+}_{c}$π - with Λ$^{+}_{c}$ reconstructed via its pK - π + decay mode. The branching fraction ratio $\mathscr{B}$(Ξ$^{0}_{c}$ → Λ$^{+}_{c}$π - )/$\mathscr{B}$(Ξ$^{0}_{c}$ → Ξ - π + ) is measured to be 0.38 ±0.04 ±0.04. Combining with the world average value of $\mathscr{B}$(Ξ$^{0}_{c}$ → Ξ - π + ), the branching fraction $\mathscr{B}$(Ξ$^{0}_{c}$ → Λ$^{+}_{c}$π - ) is deduced to be (0.54 ±0.05 ±0.05 ±0.12)%. Here, the uncertainties above are statistical, systematic, and from $\mathscr{B}$(Ξ$^{0}_{c}$ → Ξ - π + ), respectively.