20 research outputs found
Measurement of branching fractions for decays and search for a narrow resonance in the final state
We report an observation of the and decays using pairs collected at the resonance with the Belle detector at the KEKB asymmetric-energy collider. We obtain the branching fractions and . We search for a new narrow charmonium(-like) state in the mass spectrum and find no significant excess. We set upper limits on the product of branching fractions, , at where a -odd partner of may exist, at and assuming their known mass and width, and over a range from 3.8 to . The obtained upper limits at 90% confidence level for , , and are , , and , respectively
Pion wave function from lattice QCD vs. chiral quark models
We analyze the equal-time Bethe-Salpeter quark wave function of the pion
obtained from a quenched lattice QCD calculation with delocalized quark
interpolators. We find that the result agrees remarkably well with the
predictions of the Nambu--Jona-Lasinio model in all channels. We choose the
quenched lattice QCD, since it is closer to the large-Nc limit of the
Nambu--Jona-Lasinio model. We also show how transversity information, relevant
for the light-cone physics, can be obtained from our equal-time rest-frame
lattice calculations.Comment: 7 pages, 2 figure
Slow control of the Belle II Aerogel Ring Imaging detector
Since 2018, an Proximity Focusing Aerogel Ring Imaging Detector (ARICH) efficiently separates hadrons in the forward end-cap of the Belle II spectrometer. Cherenkov photons emitted in the double-layer aerogel radiator are expanded in 16-cm space and detected on the photon detector, which consists of 420 hybrid avalanche photodiodes and rear readout electronics operating in threshold mode. Each of the sensors requires six different high voltages and a supply of four low voltages for the electronics. Because of the power dissipation, the system also includes a cooling system in which cold water circulates through the Al tubes thermally connected to the readout electronics. Reliable control of supply voltages and monitoring of environmental data and sensor status ensure stable operation of the ARICH detector and early response to sudden changes in current, single event disturbances, overheating, and other faults. In this paper, we introduce the ARICHās slow control system and the data quality monitor used to track performance
Measurement of two-particle correlations of hadrons in ā«ā« collisions at Belle
The measurement of two-particle angular correlation functions in high-multiplicity e+eā collisions at ās=10.52āāGeV is reported. In this study, the 89.5āāfbā1 of hadronic e+eā annihilation data collected by the Belle detector at KEKB are used. Two-particle angular correlation functions are measured in the full relative azimuthal angle (ĪĻ) and three units of pseudorapidity (ĪĪ·), defined by either the electron beam axis or the event-shape thrust axis, and are studied as a function of charged-particle multiplicity. The measurement in the thrust axis analysis, with mostly outgoing quark pairs determining the reference axis, is sensitive to the region of additional soft gluon emissions. No significant anisotropic collective behavior is observed with either coordinate analyses. Near-side jet correlations appear to be absent in the thrust axis analysis. The measurements are compared to predictions from various event generators and are expected to provide new constraints to the phenomenological models in the low-energy regime
Particle identification performance of the prototype aerogel RICH counter for the Belle II experiment
We have developed a new type of particle identification device, called an aerogel ring imaging Cherenkov (ARICH) counter, for the Belle II experiment. It uses silica aerogel tiles as Cherenkov radiators. For detection of Cherenkov photons, hybrid avalanche photo-detectors (HAPDs) are used. The designed HAPD has a high sensitivity to single photons under a strong magnetic field. We have confirmed that the HAPD provides high efficiency for single-photon detection even after exposure to neutron and -ray radiation that exceeds the levels expected in the 10-year Belle II operation. In order to confirm the basic performance of the ARICH counter system, we carried out a beam test at the using a prototype of the ARICH counter with six HAPD modules. The results are in agreement with our expectations and confirm the suitability of the ARICH counter for the Belle II experiment. Based on the in-beam performance of the device, we expect that the identification efficiency at is 97.4% and 4.9% for pions and kaons, respectively. This paper summarizes the development of the HAPD for the ARICH and the evaluation of the performance of the prototype ARICH counter built with the final design components
Search for the decay ā«ā«
We report results from a search for the decay B0sāĪ·Ī· using 121.4āāfbā1 of data collected at the Ī„(5S) resonance with the Belle detector at the KEKB asymmetric-energy e+eā collider. We do not observe any signal and set an upper limit on the branching fraction of 14.3Ć10ā5 at 90% confidence level. This result represents a significant improvement over the previous most stringent limit
Measurement of the branching fraction and ā«ā« asymmetry for ā«ā« decays
We measure the branching fractions and CP asymmetries for the decays Bā° ā DĀÆ 0Ļā° and Bāŗ ā DĀÆ 0Ļāŗ, using a data sample of 772 Ć 10ā¶ BBĀÆ pairs collected at the Ļ(4S) resonance with the Belle detector at the KEKB eāŗeā collider. The branching fractions obtained and direct CP asym-metries are B(Bā° ā DĀÆ 0Ļā°)=[2.70 0.06(stat) 0.10(syst)]Ć10āā“, B(Bāŗ ā DĀÆ 0Ļāŗ)=[4.53 0.02(stat) 0.15(syst)]Ć10āĀ³, ACP(Bā° ā DĀÆ 0Ļā°)= [+0.42 2.05(stat) 1.22(syst)]%, and ACP(Bāŗ ā DĀÆ 0Ļāŗ) = [+0.19 0.36(stat) 0.57(syst)]%. The measurements of B are the most precise to date and are in good agreement with previous results, as is the measurement of ACP(Bāŗ ā DĀÆ 0Ļāŗ). The measurement of ACP for Bā° ā DĀÆ 0Ļā° is the first for this mode, and the value is consistent with Standard Model expectations