Understanding thee⁺e⁻→D^{(*) +}D^{(*) −}processes observed by Belle

Abstract

We calculate the production cross sections for D * + D * − , D + D * − and D + D − in e + e − annihilation through one virtual photon in the framework of perturbative QCD with constituent quarks. The calculated cross sections for D * + D * − and D + D * − production are roughly in agreement with the recent Belle data. The helicity decomposition for D * meson production is also calculated. The fraction of the D * ± L D * ∓ T final state in e + e − → D * + D * − process is found to be 65%. The fraction of DD * T production is 100% and DD * L is forbidden in e + e − annihilation through one virtual photon. We further consider e + e − annihilation through two virtual photons, and then find the fraction of DD * T in e + e − → DD * process to be about 91%. PACS number(s): 12.40. Nn, 13.85.Ni, 14.40.Gx Recently, heavy meson production in e + e − annihilation has become a very interesting subject both experimentally and theoretically. For instance, for charmonium production in e + e − annihilation at the B-factory energy √ s = 10.6GeV, there are large differences between the experimental data [1, 2, 3] and the calculated cross sections for both exclusive processes [4] and inclusive processes [5]. Even by including the effects of e + e − annihilation into two photons in the exclusive double-charmonium production [6] and inclusive charmonium production [7], the large discrepancies still exist [8]. Moreover, most recently the Belle Collaboration has measured [9] the charmed meson pair D ( * )+ D ( * )− production in e + e − annihilation and also found a large differences between observed data and theoretical predictions [10]. The measured cross sections are σ(e + e − → D * + D * − ) = 0.65 ± 0.04 ± 0.07 pb and σ(e + e − → D + D * − ) = 0.71 ± 0.05 ± 0.09 pb, which are, however, lower than those predicted in Ref.[10] by an order of magnitude (see [9] for the comparison). The Belle measurements of the exclusive D meson pair production in e + e − annihilation could be another challenge to the theoretical studies. In order to understand these production processes, in this letter we will present a calculation in the framework of perturbative QCD with constituent quarks. Namely, we will treat the charmed mesons D ( * ) as bound states of a constituent charmed quark and a constituent light antiquark, and the virtual photon will couple to the charm quark, which will subsequently emit a light quark pair with constituent quark masses through a virtual gluon (see the upper diagram in Fig. 1). The virtuality of the virtual gluon could be large enough for the application of perturbative QCD. In addition, the case of the 1

Exclusive double B meson production from e+e− annihilation into two virtual photons

“…2. A comparison of numerical results of the two-photon mechanism of electron-positron annihilation with the one-photon mechanism shows that the two-photon contribution to the total cross sections for the production of a pair is suppressed by a small factor 10 −3 , which is associated with the ratio of interaction constants α 2 /α 2 s and qualitatively corresponds to the results for D + D − [55]. There are no factors that could lead to an increase in the cross sections for two-photon annihilation compared with one-photon annihilation.…”

Bridging light-cone and NRQCD approaches: asymptotic behavior of B c electromagnetic form factor

“…On the other hand, although modeling the B meson LCDA as Φ B (x) = f B 2 √ 2Nc δ(x − x 0 ) may seem to be a overly rough approximation, it may arguably capture some reasonable physics provided that m u is taken as the constituent quark mass of order Λ QCD . That is, this approximation is compatible 12 For a phenomenological investigation of time-like D ( * )+ D ( * )− form factor from this perspective, see [43].…”

New Ni(II), Pd(II) and Pt(II) complexes coordinated to azo pyrazolone ligand with a potent anti‐tumor activity: Synthesis, characterization, DFT and DNA cleavage studies

“…(E)-4-((2-hydroxyphenyl)diazenyl)-3-phenyl-1H-pyrazol-5(4H)-one, HL, and its Ni(II), Pd(II) and Pt(II) complexes were synthesized and the biological activity was evaluated for antitumor, antioxidant and antimicrobial activity as well as DNA cleavage. Their structures were assigned depending on the elemental analysis, conductivity, magnetic moment, spectral measurements (IR, 1 HNMR, mass and UV-Vis) and thermal analysis. 3D molecular modeling using DFT method confirmed that the geometrical structures agree well with the suggested experimental ones.…”

“…The compounds having pyrazolone moiety are found to be remarkable anti-tubercular, anti-inflammatory, antibacterial, antifungal and antitumor activity. [1] Due to the reactivity of position −4 in the pyrazolone ring, it undergoes a coupling reaction with a number of aryl diazonium chlorides forming 4-arylazo derivatives, which considered an important class of azo dyes. The azo-derivatives of pyrazolone compounds have attracted attention because of their potential importance in medicinal chemistry as antimicrobial and therapeutic agents, [2] in analytical chemistry as complexing agents having an excellent ability to form chelates with a number of metal cations [3] for the determination of these metal ions spectrophotometrically [4] , and in industrial chemistry as dyestuffs.…”