We report a measurement of the process γγ * → π 0 with a 759 fb −1 data sample recorded with the Belle detector at the KEKB asymmetric-energy e + e − collider. The pion transition form factor, F (Q 2 ), is measured for the kinematical region 4 GeVGeV 2 , where −Q 2 is the invariant mass squared of a virtual photon. The measured values of Q 2 |F (Q 2 )| agree well with the previous measurements below Q 2 ≃ 9 GeV 2 but do not exhibit the rapid growth in the higher Q 2 region seen in another recent measurement, which exceeds the asymptotic QCD expectation by as much as 50%.

We report the observation of prompt J/psi via double cc; production from the e+e- continuum. In this process one cc; pair fragments into a J/psi meson while the remaining pair either produces a charmonium state or fragments into open charm. Both cases have been experimentally observed. We find cross sections of sigma[e+e- -->J/psieta(c)(gamma)]xB(eta(c)-->>or=4 charged)=(0.033(+0.007)(-0.006)+/-0.009) pb and sigma(e+e- -->J/psiD(*+)X)=(0.53(+0.19)(-0.15)+/-0.14) pb and infer sigma(e+e- -->J/psicc;)/sigma(e+e- -->J/psiX)=0.59(+0.15)(-0.13)+/-0.12. These results are obtained from a 46.2 fb(-1) data sample collected near the Upsilon(4S) resonance, with the Belle detector at the KEKB collider.

We report measurements of the continuum R(uds) near the center-of-mass energy of 3.70 GeV, the R[uds(c)+psi(3770)](s) and the R(had)(s) values in e(+)e(-) annihilation at 68 energy points in the energy region between 3.650 and 3.872 GeV with the BES-II detector at the BEPC Collider. We obtain the R(uds) for the continuum light hadron (containing u, d, and s quarks) production near the DD threshold to be R(uds)=2.141+/-0.025+/-0.085.

We report measurements of the properties of the D sJ 2317 and D sJ 2457 resonances produced in continuum e e ÿ annihilation near s p 10:6 GeV. The analysis is based on an 86:9 fb ÿ1 data sample collected with the Belle detector at KEKB. We determine the masses to be M D sJ Belle [7]. This has led to speculation that the new D s 0 resonances, which we denote D sJ , may be exotic mesons [8][9][10][11][12][13]. Measurements of the D sJ quantum numbers and branching fractions (particularly those for radiative decays) will play an important role in determining the nature of these states.In this Letter we report measurements of the D sJ masses, widths, and branching fractions using a sample of e e ÿ ! c c c events collected with the Belle detector [14] at the KEKB collider [15].We reconstruct D s mesons using the decay chain D s ! and ! K K ÿ . To identify kaons or pions, we form a likelihood for each track, L K , from dE=dx measurements in a 50-layer central drift chamber, the responses from aerogel threshold Č erenkov counters, and time-of-flight scintillation counters. The kaon likelihood ratio, P K= L K = L K L , has values between 0 (likely to be a pion) and 1 (likely to be a kaon).For ! K K ÿ candidates we use oppositely charged track pairs where one track has P K= > 0:5 and the other has P K= > 0:2, and with a K K ÿ invariant mass that is within 10 MeV=c 2 2:5 of the nominal mass. We define the helicity angle H to be the angle between the direction of the K and the D s in the rest frame. For signal events this has a cos 2 H distribution, while for background it is flat; we require j cos H j > 0:35.We reconstruct D s candidates by combining a candidate with a candidate, which is a charged track with P K= < 0:9, and requiring M to be within Fig. 1(a) To study the expected signal shape and detection efficiencies, and to determine the level of cross-feed between the two states, we use a Monte Carlo (MC) simulation that treats the D sJ 2317 as a scalar particle with mass 2317 MeV=c 2 decaying to D s 0 and the D sJ 2457 as an axial-vector particle with mass 2457 MeV=c 2 decaying to D s 0 . Zero intrinsic width is assigned to both states. We find that the D sJ 2317 produces a peak of width 7:1 0:2 MeV=c 2 in the M D s 0 distribution at its nominal mass, and a broader reflection peak (of width 12:3 1:8 MeV=c 2 ) at a mass of 8 MeV=c 2 above the D sJ 2457 peak. This latter peak corresponds to a D s and 0 from a D sJ 2317 decay that are combined with a random photon that passes the jM D s ÿ M D s j < 15 MeV=c 2 requirement. (We refer to this as ''feed-up background.'') The D sJ 2457 produces a peak of width 6:0 0:2 MeV=c 2 at its nominal mass and a broader peak (of width 19:5 3:6 MeV=c 2 ), also at its nominal mass. The latter peak is due to events in which the photon from D s ! D s is missed, and a random photon is reconstructed in its place (referred to as the ''broken-signal background''). In addition, the D sJ 2457 produces a reflection in the D s 0 mass distribution with width 14:9 0:8 MeV=c 2 at a mass of 4 Me...

No abstract