• Energy Research

Abstract We report the first measurement of the exclusive cross sections e+e− → $$ B\overline{B} $$ B B ¯ , e+e− → $$ B{\overline{B}}^{\ast } $$ B B ¯ ∗ , and e+e− → $$ {B}^{\ast }{\overline{B}}^{\ast } $$ B ∗ B ¯ ∗ in the energy range from 10.63 GeV to 11.02 GeV. The B mesons are fully reconstructed in a large number of hadronic final states and the three channels are identified using a beam-constrained-mass variable. The shapes of the exclusive cross sections show oscillatory behavior with several maxima and minima. The results are obtained using data collected by the Belle experiment at the KEKB asymmetric-energy e+e− collider.

The inclusive cross sections for di-hadrons of charged pions and kaons ($e^+e^- \rightarrow hhX$) in electron-positron annihilation are reported. They are obtained as a function of the total fractional energy and invariant mass for any di-hadron combination in the same hemisphere as defined by the thrust event-shape variable and its axis. Since same-hemisphere di-hadrons can be assumed to originate predominantly from the same initial parton, di-hadron fragmentation functions are probed. These di-hadron fragmentation functions are needed as an unpolarized baseline in order to quantitatively understand related spin-dependent measurements in other processes and to apply them to the extraction of quark transversity distribution functions in the nucleon. The di-hadron cross sections are obtained from a $655\,{\rm fb}^{-1}$ data sample collected at or near the $��(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. 21 pages, 18 figures plus 25 figures in supplemental material, submitted to PRD

We report searches for the processes $e^+e^-\to\pi^+\pi^-\pi^0\chi_{bJ}$ and $e^+e^-\to\phi\chi_{bJ}$ (J=1,2) in the vicinity of the $\Upsilon(11020)$ resonance using energy scan data collected by the Belle experiment at the KEKB collider. We observe $e^+e^-\to \pi^+\pi^-\pi^0\chi_{b1}$ and find evidence for $e^+e^-\to \omega\chi_{b2}$ processes for data with center-of-mass energies from 10.96 to 11.05~GeV for the first time. The statistical significance for $\pi^+\pi^-\pi^0\chi_{b1}$ and $\omega\chi_{b2}$ are $6.1\sigma$ and $4.0\sigma$, respectively. We investigate energy dependence of the $e^+e^-\to\pi^+\pi^-\pi^0\chi_{bJ}$ cross section and find that it is consistent with production of $\Upsilon(10860)$ and $\Upsilon(11020)$ resonances without significant non-resonant contribution. Assuming $e^+e^-\to \pi^+\pi^-\pi^0\chi_{bJ}$ proceeds via $\Upsilon(10860)$ and $\Upsilon(11020)$, the branching fraction $\mathcal{B}(\Upsilon(11020)\to\pi^+\pi^-\pi^0\chi_{bJ})=(8.6\pm4.1\pm6.1^{+4.5}_{-2.5})\times10^{-3}$ is measured for the first time, where the first error is statistical, the second is systematic, and the third from the branching fraction of $\Upsilon(11020)\to e^+e^-$. The signals for $e^+e^-\to \phi\chi_{bJ}$ are not significant, and the upper limits of the Born cross sections at the 90\% confidence level are $0.6$ and $1.0$~pb for $e^+e^-\to \phi\chi_{b1}$ and $\phi\chi_{b2}$, respectively, for center-of-mass energies from 10.96 to 11.05~GeV.

We report new measurements of the production cross sections of pairs of charged pions and kaonsas a function of their fractional energies using various fractional-energy definitions. Two different fractional-energy definitions were used and compared to the conventional fractional-energy definitionreported previously. The new variables aim at either identifying dihadron cross sections in terms of single-hadron fragmentation functions, or to provide a means of characterizing the transverse momentum created in the fragmentation process. The results were obtained applying the updated initial-state radiation correction used in other recent Belle publications on light-hadron production cross sections. In addition, production cross sections of single charged pions, kaons, and protons were also updated using this initial-state radiation correction. The cross sections 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 Physical review / D D 101(9), 092004: 1-13 (2020). doi:10.1103/PhysRevD.101.092004 Published by American Physical Society, Melville, NY