This work reports the first observation of azimuthal asymmetries around the thrust axis in e+e− annihilation of pairs of back-to-back charged pions in one hemisphere, and π0 and η mesons in the opposite hemisphere. ...
详细信息
This work reports the first observation of azimuthal asymmetries around the thrust axis in e+e− annihilation of pairs of back-to-back charged pions in one hemisphere, and π0 and η mesons in the opposite hemisphere. These results are complemented by a new analysis of pairs of back-to-back charged pions. The π0 and η asymmetries rise with the relative momentum z of the detected hadrons as well as with the transverse momentum with respect to the thrust axis. These asymmetries are sensitive to the Collins fragmentation function H1⊥ and provide complementary information to previous measurements with charged pions and kaons in the final state. In particular, the η final states will provide additional information on the flavor structure of H1⊥. This is the first measurement of the explicit transverse-momentum dependence of the Collins fragmentation function from Belle data. It uses a dataset of 980.4 fb−1 collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV.
We report a measurement of time-dependent CP violation in B0→KS0π0π0 decays using a data sample of 772×106 BB¯ pairs collected by the Belle experiment running at the ϒ(4S) resonance at the KEKB e+e− coll...
详细信息
We report a measurement of time-dependent CP violation in B0→KS0π0π0 decays using a data sample of 772×106 BB¯ pairs collected by the Belle experiment running at the ϒ(4S) resonance at the KEKB e+e− collider. This decay proceeds mainly via a b→sdd¯ “penguin” amplitude. The results are sin2ϕ1eff=0.92−0.31+0.27 (stat.) ±0.11 (syst.) and A=0.28±0.21 (stat.) ±0.04 (syst.), which are the most precise measurements of CP violation in this decay mode to date. The value for the CP-violating parameter sin2ϕ1eff is consistent with that obtained using decay modes proceeding via a b→cc¯s “tree” amplitude.
We report on the first Belle search for a light CP-odd Higgs boson, A0, that decays into low mass dark matter, χ, in final states with a single photon and missing energy. We search for events produced via the dipion ...
详细信息
We report on the first Belle search for a light CP-odd Higgs boson, A0, that decays into low mass dark matter, χ, in final states with a single photon and missing energy. We search for events produced via the dipion transition ϒ(2S)→ϒ(1S)π+π−, followed by the on-shell process ϒ(1S)→γA0 with A0→χχ, or by the off-shell process ϒ(1S)→γχχ. Utilizing a data sample of 157.3×106 ϒ(2S) decays, we find no evidence for a signal. We set limits on the branching fractions of such processes in the mass ranges MA0<8.97 GeV/c2 and Mχ<4.44 GeV/c2. We then use the limits on the off-shell process to set competitive limits on WIMP-nucleon scattering in the WIMP mass range below 5 GeV/c2.
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 t...
详细信息
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.
Using a data sample of 921.9 fb−1 collected with the Belle detector, we study the process of e+e−→Ds+Ds1(2536)−+c.c. via initial-state radiation. We report the first observation of a vector charmoniumlike state deca...
详细信息
Using a data sample of 921.9 fb−1 collected with the Belle detector, we study the process of e+e−→Ds+Ds1(2536)−+c.c. via initial-state radiation. We report the first observation of a vector charmoniumlike state decaying to Ds+Ds1(2536)−+c.c. with a significance of 5.9σ, including systematic uncertainties. The measured mass and width are (4625.9−6.0+6.2(stat)±0.4(syst)) MeV/c2 and (49.8−11.5+13.9(stat)±4.0(syst)) MeV, respectively. The product of the e+e−→Ds+Ds1(2536)−+c.c. cross section and the branching fraction of Ds1(2536)−→D¯*0K− is measured from the DsD¯s1(2536) threshold to 5.59 GeV.
We report the first observation of the spontaneous polarization of Λ and Λ¯ hyperons transverse to the production plane in e+e− annihilation, which is attributed to the effect arising from a polarizing fragment...
详细信息
We report the first observation of the spontaneous polarization of Λ and Λ¯ hyperons transverse to the production plane in e+e− annihilation, which is attributed to the effect arising from a polarizing fragmentation function. For inclusive Λ/Λ¯ production, we also report results with subtracted feed-down contributions from Σ0 and charm. This measurement uses a dataset of 800.4 fb−1 collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV. We observe a significant polarization that rises with the fractional energy carried by the Λ/Λ¯ hyperon.
We report the study of B+→pΛ¯K+K− and B+→p¯ΛK+K+ decays using a 772×106 BB¯ pair data sample recorded on the ϒ(4S) resonance with the Belle detector at KEKB. The following branching fractions ...
详细信息
We report the study of B+→pΛ¯K+K− and B+→p¯ΛK+K+ decays using a 772×106 BB¯ pair data sample recorded on the ϒ(4S) resonance with the Belle detector at KEKB. The following branching fractions are measured: B(B+→pΛ¯K+K−)=(4.10−0.43+0.45±0.50)×10−6, B(B+→p¯ΛK+K+)=(3.70−0.37+0.39±0.44)×10−6, B(ηc→pΛ¯K−+c.c.)=(2.83−0.34+0.36±0.35)×10−3 and B(B+→pΛ¯ϕ)=( 7.95±2.09±0.77)×10−7, where c.c. denotes the corresponding charge-conjugation process. The intermediate resonance decays are excluded in the four-body decay measurements. We also find evidence for B(ηc→Λ(1520)Λ¯+c.c.)=(3.48±1.48±0.46)×10−3 and B(B+→Λ(1520)Λ¯K+)=( 2.23±0.63±0.25)×10−6. No significant signals are found for J/ψ→Λ(1520)Λ¯+c.c. and B+→Λ¯(1520)ΛK+; we set the 90% confidence level upper limits on their decay branching fractions as <1.80×10−3 and <2.08×10−6, respectively.
We report measurements of isospin asymmetry Δ0− and difference of direct CP asymmetries ΔACP between charged and neutral B→Xsγ decays. This analysis is based on the data sample containing 772×106BB¯ pair...
详细信息
We report measurements of isospin asymmetry Δ0− and difference of direct CP asymmetries ΔACP between charged and neutral B→Xsγ decays. This analysis is based on the data sample containing 772×106BB¯ pairs that was collected with the Belle detector at the KEKB energy-asymmetric e+e− collider. Using a sum-of-exclusive technique with invariant Xs mass up to 2.8 GeV/c2, we obtain Δ0−=[−0.48±1.49(stat)±0.97(syst)±1.15(f+−/f00)]% and ΔACP=[+3.69±2.65(stat)±0.76(syst)]%, where the last uncertainty for Δ0− is due to the uncertainty on the production ratio of B+B− to B0B¯0 in ϒ(4S) decays. The measured value of Δ0− is consistent with zero, allowing us to constrain the resolved photon contribution in the B→Xsγ, and improve the branching fraction prediction. The result for ΔACP is consistent with the prediction of the SM. We also measure the direct CP asymmetries for charged and neutral B→Xsγ decays. All the measurements are the most precise to date.
We report the results of a search for the decay B0→X(3872)(→J/ψπ+π−)γ. The analysis is performed on a data sample corresponding to an integrated luminosity of 711 fb−1 and containing 772×106BB¯ pairs,...
详细信息
We report the results of a search for the decay B0→X(3872)(→J/ψπ+π−)γ. The analysis is performed on a data sample corresponding to an integrated luminosity of 711 fb−1 and containing 772×106BB¯ pairs, collected with the Belle detector at the KEKB asymmetric-energy e+e− collider running at the ϒ(4S) resonance energy. We find no evidence for a signal and place an upper limit of B(B0→X(3872)γ)×B(X(3872)→J/ψπ+π−)<5.1×10−7 at 90% confidence level.
We present the first measurements of branching fractions of rare tau-lepton decays, τ−→π−ντℓ+ℓ− (ℓ=e or μ), using a data sample corresponding to 562 fb−1 collected at a center-of-mass energy of 10.58 GeV with t...
详细信息
We present the first measurements of branching fractions of rare tau-lepton decays, τ−→π−ντℓ+ℓ− (ℓ=e or μ), using a data sample corresponding to 562 fb−1 collected at a center-of-mass energy of 10.58 GeV with the Belle detector at the KEKB asymmetric-energy e+e− collider. The τ−→π−ντe+e− decay is observed for the first time with 7.0σ significance. The partial branching fraction determined by the structure-dependent mechanisms mediated by either a vector or an axial-vector current for the mass region Mπee>1.05 GeV/c2 is measured to be B(τ−→π−ντe+e−)[Mπ−e+e−>1.05 GeV/c2]=(5.90±0.53±0.85±0.11)×10−6, where the first uncertainty is statistical, the second is systematic, and the third is due to model dependence. In the full phase space, due to the different detection efficiencies for the structure-dependent mechanisms mediated by axial-vector and vector currents, the branching fraction varies from BA(τ−→π−ντe+e−)=(1.46±0.13±0.21)×10−5 to BV(τ−→π−ντe+e−)=(3.01±0.27±0.43)×10−5, respectively. An upper limit is set on the branching fraction of the τ−→π−ντμ+μ− decay, B(τ−→π−ντμ+μ−)<1.14×10−5, at the 90% confidence level.
暂无评论