Observation of an Excited Ω^{-} Baryon Adachi, I; Ahn, J K; Al Said, S ...
Physical review letters,
2018-Aug-03, Letnik:
121, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Using data recorded with the Belle detector, we observe a new excited hyperon, an Ω^{*-} candidate decaying into Ξ^{0}K^{-} and Ξ^{-}K_{S}^{0} with a mass of 2012.4±0.7(stat)±0.6(syst) MeV/c^{2} and ...a width of Γ=6.4_{-2.0}^{+2.5}(stat)±1.6(syst) MeV. The Ω^{*-} is seen primarily in ϒ(1S),ϒ(2S), and ϒ(3S) decays.
Using a sample of 771.6×10(6) ϒϒ(4S) decays collected by the Belle experiment at the KEKB e(+)e(-) collider, we observe, for the first time, the transition ϒ(4S)→ηh(b)(1P) with the branching fraction ...Bϒ(4S)→ηh(b)(1P)=(2.18±0.11±0.18)×10(-3) and we measure the h(b)(1P) mass M(h(b)(1P))=(9899.3±0.4±1.0) MeV/c(2), corresponding to the hyperfine (HF) splitting ΔM(HF)(1P)=(0.6±0.4±1.0) MeV/c(2). Using the transition h(b)(1P)→γη(b)(1S), we measure the η(b)(1S) mass M(η(b)(1S))=(9400.7±1.7±1.6) MeV/c(2), corresponding to ΔM(HF)(1S)=(59.6±1.7±1.6) MeV/c(2), the η(b)(1S) width Γ(η(b)(1S))=(8(-5)(+6)±5) MeV/c(2) and the branching fraction Bh(b)(1P)→γη(b)(1S)=(56±8±4)%.
We report measurements of the branching fractions of singly Cabibbo-suppressed decays Λc+ → pη and Λc+ → pπ0 using the full Belle data sample corresponding to an integrated luminosity of 980.6 ...fb−1. The data were collected by the Belle detector at the KEKB e+ e− asymmetric energy collider. A clear Λ + c signal is seen in the invariant mass distribution of p η . The fitted number of signal events of the Λc+ → pη process is 7734 ± 263 ; from this, we measure the ratio of branching fractions B ( Λc+→ pη ) / B ( Λc+ → pK− π+ ) = 2.258 ± 0. 077 ( stat ) ± 0.122 ( syst ) × 10 − 2 , from which we infer the branching fraction B ( Λc+ → pη ) = 1.42 ± 0.05 ( stat ) ± 0.11 ( syst ) × 10−3. In addition, no significant signal for Λc+ → pπ0 is found, so an upper limit on the branching fraction of B ( Λc+ → pπ0) < 8.0 × 10−5 at a 90% credibility level is set, more than 3 times better than the best current upper limit.
We present the results of an amplitude analysis of B¯0→J/ψK-π+ decays. A new charged charmoniumlike state Zc(4200)+ decaying to J/ψπ+ is observed with a significance of 6.2σ. The mass and width of ...the Zc(4200)+ are 4196+31-29+17-13 MeV/c2 and 370+70-70+70-132 MeV, respectively; the preferred assignment of the quantum numbers is JP=1+. In addition, we find evidence for Zc(4430)+→J/ψπ+. The analysis is based on a 711 fb-1 data sample collected by the Belle detector at the asymmetric-energy e+e- collider KEKB.
We report results from a study of the spin and parity of Ξ c ( 2970 ) + using a 980 fb −1 data sample collected by the Belle detector at the KEKB asymmetric-energy e+e− collider. The decay angle ...distributions in the chain Ξc (2970)+→ Ξc (2645) 0π+ → Ξ+c π− π+ are analyzed to determine the spin of this charmed-strange baryon. The angular distributions strongly favor the Ξc (2970)+ spin J = 1/2 over 3/2 or 5/2, under an assumption that the lowest partial wave dominates in the decay. We also measure the ratio of Ξc (2970)+ decay branching fractions R = B Ξc (2970)+ → Ξc (2645)0π+/B Ξc (2970)+ → Ξ0c π+ = 1.67 ± 0.29 (stat)+0.15 −0.09 (syst) ± 0.25 (IS), where the last uncertainty is due to possible isospin-symmetry-breaking effects. This R value favors the spin-parity J P = 1/2+ with the spin of the light-quark degrees of freedom sl = 0. This is the first determination of the spin and parity of a charmed-strange baryon.
We report the first observation of the double strange baryon Ξ(1620)0 in its decay to Ξ−π+ via Ξ+c → Ξ−π+π+ decays based on a 980 fb−1 data sample collected with the Belle detector at the KEKB ...asymmetric-energy e+e− collider. The mass and width are measured to be 1610.4 ± 6.0(stat)+6.1−4.2(syst) MeV /c2 and 59.9 ± 4.8(stat)+2.8−7.1(syst) MeV, respectively. We obtain 4.0σ evidence of the Ξ(1690)0 with the same data sample. These results shed light on the structure of hyperon resonances with strangeness S = −2
We report measurements of the production cross sections of charged pions, kaons, and protons as a function of fractional energy, the event-shape variable called thrust, and the transverse momentum ...with respect to the thrust axis. These measurements access the transverse momenta created in the fragmentation process, which are of critical importance to the understanding of any transverse-momentum-dependent distribution and fragmentation functions. The low transverse-momentum part of the cross sections can be well described by Gaussians in transverse momentum as is generally assumed but the fractional-energy dependence is nontrivial and different hadron types have varying Gaussian widths. The width of these Gaussians decreases with thrust and shows an initially rising, then decreasing fractional-energy dependence. The widths for pions and kaons are comparable within uncertainties, while those for protons are significantly narrower. These single-hadron cross sections and Gaussian widths are obtained from a 558 fb−1 data sample collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider.
We present a search for the lepton flavor violating decays B^{+}→K^{+}τ^{±}ℓ^{∓}, with ℓ=(e,μ), using the full data sample of 772×10^{6} BBover ¯ 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^{±}τℓ 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.
Study of γγ→γψ(2S) at Belle Wang, X. L.; Aihara, H.; Asner, D. M. ...
Physical review. D,
06/2022, Letnik:
105, Številka:
11
Journal Article
Recenzirano
Odprti dostop
Using 980 fb-1 of data at and around the Υ(nS)(n = 1, 2, 3, 4, 5) resonances collected with the Belle detector at the KEKB asymmetric-energy e+e- collider, the two-photon process γγ → γψ(2S) is ...studied from the threshold to 4.2 GeV for the first time. Two structures are seen in the invariant mass distribution of γψ(2S): one at MR1 = 3922.4 ± 6.5 ± 2.0 MeV/c2 with a width of ΓR1 = 22 ± 17 ± 4 MeV, and another at MR2 = 4014.3 ± 4.0 ± 1.5 MeV/c2 with a width of ΓR2 = 4 ± 11 ± 6 MeV; the signals are parametrized with the incoherent sum of two Breit- Wigner functions. The first structure is consistent with the X(3915) or the χc2(3930), and the local statistical significance is determined to be 3.1σ with the systematic uncertainties included. The second matches none of the known charmonium or charmonium like states, and its global significance is determined to be 2.8σ including the look-elsewhere effect. The production rates are Γγγ B(R1 → γψ(2S)) = 9.8 ± 3.6 ± 1.2 eV assuming (JPC, |λ|) = (0++, 0) or 2.0 ± 0.7 ± 0.2 eV with (2++, 2) for the first structure and Γγγ B(R2 → γψ(2S)) = 6.2 ± 2.2 ± 0.8 eV with (0++, 0) or 1.2 ± 0.4 ± 0.2 eV with (2++, 2) for the second one. Furthermore, the first errors are statistical and the second systematic, and λ is the helicity.
We present the first measurements of the absolute branching fractions of Ξc+ decays into Ξ−π+π+ and pK−π+ final states. Our analysis is based on a data set of (772±11)×106 BB¯ pairs collected at the ...ϒ(4S) resonance with the Belle detector at the KEKB e+e− collider. We measure the absolute branching fraction of B¯0→Λ¯c−Ξc+ with the Ξc+ recoiling against Λ¯c− in B¯0 decays resulting in B(B¯0→Λ¯c−Ξc+)=1.16±0.42(stat.)±0.15(syst.)×10−3. We then measure the product branching fractions B(B¯0→Λ¯c−Ξc+)B(Ξc+→Ξ−π+π+) and B(B¯0→Λ¯c−Ξc+)B(Ξc+→pK−π+). Dividing these product branching fractions by B¯0→Λ¯c−Ξc+ yields B(Ξc+→Ξ−π+π+)=2.86±1.21(stat.)±0.38(syst.)% and B(Ξc+→pK−π+)=0.45±0.21(stat.)±0.07(syst.)%. Our result for B(Ξc+→Ξ−π+π+) can be combined with Ξc+ branching fractions measured relative to Ξc+→Ξ−π+π+ to set the absolute scale for many Ξc+ branching fractions.
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