NLO corrections and contribution of a tensor gluon operator to the process γ ∗ γ → ππ
نویسندگان
چکیده
We have calculated the NLO corrections for the leading twist amplitude of the reaction γ * γ → ππ at large virtuality of the photon and at W 2 ≪ Q 2. With a simple model for the two-pion quark and gluon distribution amplitudes we have estimated that the NLO effects may reduce the leading-order amplitude by as much as 30%. We have found that besides the usual twist-2 quark and gluon operators the NLO amplitude receives contribution from a distribution associated with twist-2 tensor gluon operator. The new gluon distribution can be investigated by studying the azimuthal asymmetry of the cross section for e + γ → e ′ + ππ.
منابع مشابه
Power corrections to the process γγ ∗ → ππ in the Light - Cone Sum Rules approach
We applied QCD Light Cone Sum Rules to estimate power corrections to the helicity-conserving amplitude in the process γ * γ → ππ. We found that above Q 2 ∼ 4 GeV 2 power corrections are numerically small and the twist-2 part dominates.The amplitude can be reliably calculated in this region using models of 2π distribution amplitudes as an input. We found that the magnitude of the NLO corrections...
متن کاملX iv : h ep - p h / 94 08 40 4 v 2 8 S ep 1 99 4 OITS - 553 Isospin Structure of Penguins And Their Consequences in B Physics ∗
Isospin structure of gluon mediated or strong penguin is significantly altered when the full electroweak corrections are included. This has the consequence that some previous analyses which relied on a simple isospin structure in charmless B decays become inapplicable. We present the general Hamiltonian in next-to-leading order QCD, and illustrate our conclusion quantitatively for B → ππ and B ...
متن کاملNLO QED corrections to ISR in e+e− annihilation and the measurement of σ(e+e− → hadrons) using tagged photons
The leptonic tensor for the process ee → γ + γ∗, which describes the next-to-leading order virtual and soft QED corrections to initial state radiation in ee annihilation with emission of an extra virtual photon decaying into hadrons, is calculated. A Monte Carlo generator for the reaction ee → γ + ππ has been set up which includes these corrections. It thus describes configurations where the in...
متن کاملThe contribution of the four - parton final states to γ ∗ γ ∗ → hadrons
In the analysis of the total cross section for the γ∗γ∗ → hadrons process, we include the four parton final states, which are part of the O(α2 S ) corrections. The four-parton final states contain the diagrams with gluon exchange in the crossed channel, which constitute the leading order of the BFKL resummation. We show that the diagrams with gluon exchange in the crossed channel play an import...
متن کاملImplications of Recent Measurements of Nonleptonic Charmless B Decays
Both B factories BELLE 1 and BABAR 2 have reported at this conference the preliminary results of B → Kπ and B → ππ (see Table I). For the unitary angle γ ∼ 60, the ratio R = B(B → Kπ)/B(B → ππ) is conventionally predicted to lie in the region 1.3−2.0, to be compared with the experimental values of 4.0± 1.6, 2.8± 2.0 and 1.3± 0.5 obtained by CLEO , BELLE and BABAR, respectively. Hence, the expec...
متن کامل