We have searched for the Cabibbo-suppressed decay Λc+→ϕpπ0 in e+e− collisions using a data sample corresponding to an integrated luminosity of 915 fb−1. The data were collected by the Belle ...experiment at the KEKB e+e− asymmetric-energy collider running at or near the ϒ(4S) and ϒ(5S) resonances. No significant signal is observed, and we set an upper limit on the branching fraction of B(Λc+→ϕpπ0)<15.3×10−5 at 90% confidence level. The contribution of nonresonant Λc+→K+K−pπ0 decays is found to be consistent with zero, and the corresponding upper limit on its branching fraction is set to be B(Λc+→K+K−pπ0)NR<6.3×10−5 at 90% confidence level. We also search for an intermediate hidden-strangeness pentaquark decay Ps+→ϕp. We see no evidence for this intermediate decay and set an upper limit on the product branching fraction of B(Λc+→Ps+π0)×B(Ps+→ϕp)<8.3×10−5 at 90% confidence level. Finally, we measure the branching fraction for the Cabibbo-favored decay Λc+→K−π+pπ0; the result is B(Λc+→K−π+pπ0)=(4.42±0.05(stat)±0.12(syst)±0.16(norm))%, which is the most precise measurement to date.
Here, we discuss the first observation of the radiative charm decay D0 → ρ0γ and the first search for CP violation in decays D0 → ρ0γ , φγ , and K ¯ *0 ( 892 ) γ , using a data sample of 943fb-1 ...collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. The branching fraction is measured to be B ( D0 → ρ0γ ) = ( 1.77±0.30±0.07 ) ×10-5 , where the first uncertainty is statistical and the second is systematic. The obtained CP asymmetries A CP ( D0 → ρ0γ ) =+0.056±0.152±0.006 , A CP ( D0 → φγ ) = -0.094±0.066±0.001 , and A CP ( D0 → K ¯ *0γ ) =-0.003±0.020±0.000 are consistent with no CP violation. Furthermore, we present an improved measurement of the branching fractions B ( D0 → φγ ) = ( 2.76±0.19±0.10 ) ×10-5 and B ( D0 → K ¯ *0γ ) = ( 4.66±0.21±0.21 ) ×10-4 .
We present an analysis of the exclusive B+ → π+ π− ℓ+ νℓ decay, where ℓ represents an electron or a muon, with the assumption of charge-conjugation symmetry and lepton universality. The study ...exploits the full Υ ( 4 S ) data sample collected by the Belle detector, corresponding to 711 fb−1 of integrated luminosity. Events are selected by fully reconstructing one B meson in hadronic decay modes, subsequently determining the properties of the other B meson. We extract the signal yields using a binned maximum-likelihood fit to the missing-mass squared distribution in bins of the invariant mass of the two pions or the momentum transfer squared. We measure a total branching fraction of B(B+ → π+ π− ℓ+ νℓ) = 22.7+1.9 −1.6 (stat) ± 3.5(syst) × 10−5, where the uncertainties are statistical and systematic, respectively. This result is the first reported measurement of this decay.
Single-spin asymmetries for semi-inclusive electroproduction of charged pions in deep-inelastic scattering of positrons are measured for the first time with transverse target polarization. The ...asymmetry depends on the azimuthal angles of both the pion (phi) and the target spin axis (phi(S)) about the virtual-photon direction and relative to the lepton scattering plane. The extracted Fourier component sin((phi+phi(S))(pi)(UT) is a signal of the previously unmeasured quark transversity distribution, in conjunction with the Collins fragmentation function, also unknown. The component sin((phi-phi(S)(pi)(UT) arises from a correlation between the transverse polarization of the target nucleon and the intrinsic transverse momentum of quarks, as represented by the previously unmeasured Sivers distribution function. Evidence for both signals is observed, but the Sivers asymmetry may be affected by exclusive vector meson production.
A search for the decays B+→hcK+ and B0 → hcKS0 is performed. Evidence for the decay B+ → hcK+ is found; its significance is 4.8σ. No evidence is found for B0 → hcKS0. The branching fraction for ...B+→hcK+ is measured to be (3.7−0.9+1.0 −0.8+0.8)×10−5; the upper limit for the B0 → hcKS0 branching fraction is 1.4×10−5 at 90% C.L. In addition, a study of the pp¯π+π− invariant mass distribution in the channel B+→(pp¯π+π−)K+ results in the first observation of the decay ηc(2S) → pp¯π+π− with 12.1σ significance. The analysis is based on the 711 fb−1 data sample collected by the Belle detector at the asymmetric-energy e+e− collider KEKB at the ϒ(4S) resonance.
A comprehensive collection of results on longitudinal double-spin asymmetries is presented for charged pions and kaons produced in semi-inclusive deep-inelastic scattering of electrons and positrons ...on the proton and deuteron, based on the full HERMES data set. The dependence of the asymmetries on hadron transverse momentum and azimuthal angle extends the sensitivity to the flavor structure of the nucleon beyond the distribution functions accessible in the collinear framework. No strong dependence on those variables is observed. In addition, the hadron charge-difference asymmetry is presented, which under certain model assumptions provides access to the helicity distributions of valence quarks.
X-Ray Monochromators: I. Theory Mesropyan, M.H.; Rostomyan, A.H.
Physica status solidi. B. Basic research,
June 2002, Letnik:
231, Številka:
2
Journal Article
Recenzirano
X‐ray cyclic monochromators, which are particular cases of X‐ray resonators, are considered. Conditions for the existence of a resonance wavelength in the Co‐Kα1 line spectral interval in monolithic ...cyclic monochromators and polylithic tunable cyclic monochromators are discussed. Maximum reflectivity for a four‐reflection monolithic monochromator is achieved when each reflection is symmetric. For a two‐monolith four‐reflection polylithic monochromator, maximum reflectivity is achieved when the asymmetry of one reflection in one monolith is the inverse of the other reflection in the same monolith.
We report the first evidence for X(3872) production in two-photon interactions by tagging either the electron or the positron in the final state, exploring the highly virtual photon region. The ...search is performed in e^{+}e^{-}→e^{+}e^{-}J/ψπ^{+}π^{-}, using 825 fb^{-1} of data collected by the Belle detector operated at the KEKB e^{+}e^{-} collider. We observe three X(3872) candidates, where the expected background is 0.11±0.10 events, with a significance of 3.2σ. We obtain an estimated value for Γover ˜_{γγ}B(X(3872)→J/ψπ^{+}π^{-}) assuming the Q^{2} dependence predicted by a ccover ¯ meson model, where -Q^{2} is the invariant mass squared of the virtual photon. No X(3915)→J/ψπ^{+}π^{-} candidates are found.
We report the measurement of branching fractions and CP-violation asymmetries in B → ϕϕK decays based on a 711 fb−1 data sample containing 772 × 106 B¯B events. The data were recorded at the Υ(4S) ...resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. For B+ → ϕϕK+, the branching fraction and CP-violation asymmetry measured below the ηc threshold ... respectively. Similarly, the branching fraction obtained for ... below the ηc threshold is ... . We also measure the CP-violation symmetry for ... within the ηc region ... .(ProQuest: ... denotes formulae omitted.)
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