Engineering topics
Aulchenko, V. (ORCID:0000000253944406)
Publications and source records attributed to Aulchenko, V. (ORCID:0000000253944406).
Observation of charmed strange meson pair production in ϒ ( 2 S ) decays and in e + e − annihilation at s = 10.52 GeV
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Measurement of the e + e - → $ {B}_s^0{\overline{B}}_s^0X $ cross section in the energy range from 10.63 to 11.02 GeV using inclusive $ {D}_s^{+} $ and D 0 production
We report the first measurement of the inclusive e + e - → $b\bar{b}$ → D$^±_s$ X and e + e - → $b\bar{b}$ → D 0 / $\overline{D}^0$ X cross sections in the energy range from 10.63 to 11.02 GeV. Based on these results, we determine σ(e + e - → ${B}_s^0{\overline{B}}_s^0$ X) and σ(e + e - → $B\overline{B}$ X) in the same energy range. We measure the fraction of ${B}_s^0$ events at Υ(10860) to be f s = (${22.0}_{-2.1}^{+2.0}$)%. We determine also the ratio of the ${B}_s^0$ inclusive branching fractions $\mathcal{B}$(${B}_s^0$ → D 0 / $\overline{D}^0$X)/$\mathcal{B}$(${B}_s^0$ → ${D}_s^{\pm }$X) = 0.416 ± 0.018 ± 0.092. The results are obtained using the data collected with the Belle detector at the KEKB asymmetric-energy e + e - collider.
Observation of a threshold cusp at the Λ η threshold in the pK - mass spectrum with Λ$^{+}_{c}$ → pK - π + decays
We observe a narrow peaking structure in the pK - invariant-mass spectrum near the Λη threshold. The peak is clearly seen in 1.5 million events of Λ$^{+}_{c}$ → pK - π + decay using the 980 fb -1 data sample collected by the Belle detector at the KEKB asymmetric-energy e + e - collider. We try two approaches to explain this structure: as a new resonance and as a cusp at the Λη threshold. The best fit is obtained with a coherent sum of a Flatte function and a constant background amplitude with the reduced X 2 of 257/243 (p = 0.25), while the fits to Breit-Wigner functions are unfavored by more than 7σ. The best fit explains the structure as a cusp at the Λη threshold, and the obtained parameters are consistent with the known properties of Λ(1670). The observation gives the first identification of a threshold cusp in hadrons from the spectrum shape.
Measurement of differential distributions of B → D*$\ell\bar{v}_{\ell}$ and implications on | V cb |
We present a measurement of the differential shapes of exclusive B → D*$\ell\bar{v}_{\ell}$ (B = B - , $\bar{B}$ 0 and $\ell$ = e, μ) decays with hadronic tag-side reconstruction for the full 711 fb -1 Belle dataset. We extract the Caprini-Lellouch-Neubert (CLN) and Boyd-Grinstein-Lebed (BGL) form factor parameters and use an external input for the absolute branching fractions to determine the Cabibbo-Kobayashi-Maskawa matrix element and find |V cb | CLN = (40.2 ± 0.9) x 10 -3 and |V cb | BGL = (40.7 ± 1.0) x 10 -3 with the zero-recoil lattice QCD point $\mathcal{F}$(1) = 0.906 ± 0.013. We also perform a study of the impact of beyond zero-recoil lattice QCD calculations on the |V cb | determinations. Additionally, we present the lepton-flavor universality ratio R eμ = $\mathcal{B}$(B → D*e$\bar{v}$ e )/$\mathcal{B}$(B → D*μ$\bar{v}$ μ ) = 0.993 ± 0.023 ± 0.023, the electron and muon forwardbackward asymmetry and their difference ΔA FB = 0.028 ± 0.028 ± 0.008, and the electron and muon D* longitudinal polarization fraction and their difference ΔF$^{D*}_L$ = 0.030 ± 0.025 ± 0.007. The uncertainties quoted correspond to the statistical and systematic uncertainties, respectively.
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.
First Measurement of the B + → π + π 0 π 0 Branching Fraction and C P Asymmetry
We study B + → π + π 0 π 0 using 711 fb -1 of data collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e + e - collider. Here we measure an inclusive branching fraction of (19.0 ±1.5 ±1.4)×10 -6 and an inclusive CP asymmetry of (9.2 ±6.8 ±0.7)%, where the first uncertainties are statistical and the second are systematic, and a B + → ρ(770) + π 0 branching fraction of (11.2 ± 1.1 ± 0.9 $^{+0.8}_{-1.6}$)× 10 -6 , where the third uncertainty is due to possible interference with B + → ρ(1450) + π 0 . We present the first observation of a structure around 1 GeV/c 2 in the π 0 π 0 mass spectrum, with a significance of 6.4σ, and measure a branching fraction to be (6.9 ±0.9 ±0.6) × 10 -6 . We also report a measurement of local CP asymmetry in this structure.
Search for the decay B s 0 → π 0 π 0 at Belle
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.
Search for X ( 3872 ) → π + π - π 0 at Belle
We present a search for the decay X(3872) → π + π - π 0 in the (772 ±11) ×10 6 Y(4S)→B$\overline{B}$ data sample collected at the Belle detector, where the X(3872) is produced in B ± → K ± X(3872) and B 0 →K$^{0}_{S}$X(3872) decays. We do not observe a signal, and set 90% credible upper limits for two different models of the decay processes: if the decay products are distributed uniformly in phase space, $\mathscr{B}$(X(3872) → π + π - π 0 )<1.3%, and if M(π + π - ) is concentrated near the mass of the D 0 $\overline{D}$ 0 pair in the process X(3872) → D 0 $\overline{D}$ *0 + c.c. → D 0 $\overline{D}$ 0 π 0 → π + π - π 0 , $\mathscr{B}$(X(3872) → π + π - π 0 )<1.2×10 -3 .
Measurement of the branching fraction and search for CP violation in D 0 → K $^{0}_{S}$ K $^{0}_{S}$ π + π - decays at Belle
We measure the branching fraction for the Cabibbo-suppressed decay D 0 → K $^{0}_{S}$ K $^{0}_{S}$ π + π - and search for CP violation via a measurement of the CP asymmetry A CP as well as the T-odd triple-product asymmetry a$^{T}_{CP}$. We use 922 fb -1 of data recorded by the Belle experiment, which ran at the KEKB asymmetric-energy e + e - collider. The branching fraction is measured relative to the Cabibbo-favored normalization channel D 0 → K $^{0}_{S}$ π + π - ; the result is $\mathscr{B}$( D 0 → K $^{0}_{S}$ K $^{0}_{S}$ π + π - )=[4.79±0.08(stat)±0.10(syst)±0.31(norm)]×10 -4 , where the first uncertainty is statistical, the second is systematic, and the third is from uncertainty in the normalization channel. We also measure A CP =[-2.51±1.44(stat)$^{+0.11}_{-0.10}$(syst)]%, and a$^{T}_{CP}$=[-1.95±1.42(stat)$^{+0.14}_{-0.12}$(syst)]%. These results show no evidence of CP violation.
Angular analysis of the low K + K – invariant mass enhancement in B + →K + K – π + decays
We study the decay B + →K + K – π + and investigate the angular distribution of K + K – pairs with invariant mass below 1.1 GeV / c 2 . This region exhibits both a strong enhancement in signal and very large direct CP violation. We construct a coherent sum model for the angular distribution of the S- and P-wave, and report the ratio of their amplitudes, the relative phase and the forward-backward asymmetry. We also report absolute differential branching fractions and direct CP asymmetry for the decay in bins of M K+K– and the differential branching fractions in bins of M K+π– . The results are based on a data sample that contains 772 × 10 6 $B\bar{B}$ pairs collected at the $Υ$(4S) resonance with the Belle detector at the KEKB asymmetric-energy e + e – collider. The result favors the presence of S- and D-waves in low M K+K– region to the detriment of a P-wave.
Measurement of the branching fractions for Cabibbo-suppressed decays D + → K + K - π + π 0 and D ( s ) + → K + π - π + π 0 at Belle
We present measurements of the branching fractions for the singly Cabibbo-suppressed decays and , and the doubly Cabibbo-suppressed decay , based on of data recorded by the Belle experiment at the KEKB e + e - collider. We measure these modes relative to the Cabibbo-favored modes D + → K - π + π + π 0 and D$^{+}_{s}$ → K + K - π + π 0 . Our results for the ratios of branching fractions are $\mathscr{B}$(D + →K + K - π + π 0 )/$\mathscr{B}$(D + → K - π + π + π 0 ) =(11.32±0.13±0.26)%, $\mathscr{B}$(D + →K + π - π + π 0 )/$\mathscr{B}$(D + →K - π + π + π 0 ) =(1.68±0.11±0.03)%, and $\mathscr{B}$(D$^{+}_{s}$ → K + π - π + π 0 )/$\mathscr{B}$(D$^{+}_{s}$ → K + K - π + π 0 ) =(17.13±0.62±0.51)%, where the uncertainties are statistical and systematic, respectively. The second value corresponds to (5.83 ±0.42) ×tan 4 θ C , where θ C is the Cabibbo angle; this value is larger than other measured ratios of branching fractions for a doubly Cabibbo-suppressed charm decay to a Cabibbo-favored decay. Multiplying these results by world average values for $\mathscr{B}$(D + → K - π + π + π 0 ) and $\mathscr{B}$(D$^{+}_{s}$ → K + K - π + π 0 ) yields $\mathscr{B}$( + →K + K - π + π 0 ) = (7.08±0.08±0.16±0.20)×10 -3 , $\mathscr{B}$(D + → K + π - π + π 0 ) =(1.05±0.07±0.02±0.03)×10 -3 , and $\mathscr{B}$(D$^{+}_{s}$ → K + π - π + π 0 ) =(9.44±0.34±0.28±0.32)×10 -3 , where the third uncertainty is due to the branching fraction of the normalization mode. The first two results are consistent with, but more precise than, the current world averages. The last result is the first measurement of this branching fraction.
First search for the weak radiative decays Λ$^+_c$ → Σ + γ and Ξ$^0_c$ → Ξ 0 γ
We present the first search for the weak radiative decays Λ$^+_c$ → Σ + γ and Ξ$^0_c$ → Ξ 0 γ using a data sample of 980 fb -1 collected by the Belle detector operating at the KEKB asymmetric-energy e + e - collider. There are no evident Λ$^+_c$ → Σ + γ or Ξ$^0_c$ → Ξ 0 γ signals. Taking the decays Λ$^+_c$ → pK - π + and Ξ$^0_c$ → Ξ - π + as normalization channels, the upper limits at 90% credibility level on the ratios of branching fractions $\mathcal{B}$(Λ$^+_c$ → Σ + γ)/$\mathcal{B}$(Λ$^+_c$ → pK - π + ) < 4.0 x 10 -3 and $\mathcal{B}$(Ξ$^0_c$ → Ξ 0 γ)/$\mathcal{B}$(Ξ$^0_c$ → Ξ - π + ) < 1.2 x 10 -2 are determined. We obtain the upper limits at 90% credibility level on the absolute branching fractions $\mathcal{B}$(Λ$^+_c$ → Σ + γ) < 2.6 x 10 -4 and $\mathcal{B}$(Ξ$^0_c$ → Ξ 0 γ) < 1.8 x 10 -4 .