Engineering topics
Han, X. (ORCID:0000000316569413)
Publications and source records attributed to Han, X. (ORCID:0000000316569413).
First measurement of the Q 2 distribution of X(3915) single-tag two-photon production
We report the first measurement of the Q 2 distribution of X(3915) produced by single-tag two-photon interactions. The decay mode used is X(3915) →J/Ψω. The covered Q 2 region is from 1.5 (GeV/c) 2 to 10.0 (GeV/c) 2 . We observe 7.9 ± 3.1(stat) ± 1.5(syst) events, where we expect 4.1 ± 0.7 events based on the Q 2 = 0 result from the no-tag two-photon process, extrapolated to higher Q 2 region using the $c\bar{c}$ model of Schuler, Berends, and van Gulik. The shape of the distribution is also consistent with this model; we note that statistical uncertainties are large
Search for the Lepton Flavor Violating Decays B + → K + τ ± ℓ ∓ ( ℓ = e , μ ) at Belle
We present a search for the lepton flavor violating decays B + → K + $\tau$ ± ℓ ∓ , with ℓ = (e,μ), using the full data sample of 772×10 6 B$\overline{B}$ pairs recorded by the Belle detector at the KEKB asymmetric-energy e + e - collider. We use events in which one B meson is fully reconstructed in a hadronic decay mode. We find no evidence for B ± → K ± $\tau$ℓ decays and set upper limits on their branching fractions at the 90% confidence level in the (1 - 3) × 10 -5 range. The obtained limits are the world’s best results.
Measurement of the mass and width of the Λ c (2625) + charmed baryon and the branching ratios of Λ c (2625) + → Σ$^{0}_{c}$π + and Λ c (2625) + → Σ$^{++}_{c}$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.
Measurement of branching fractions of Λ$^+_c$ → pK$^0_S$K$^0_S$ and Λ$^+_c$ → pK$^0_S$η at Belle
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.