Narrow Results

We have investigated the contribution of the Higher Twist (HT) Feynman diagrams to the large-$p_T$ inclusive ${\rho }_L$ meson production cross-section in proton–proton and proton–antiproton collisions and we discuss the phenomenological consequences of possible HT contributions to cross-sections. To extract HT subprocesses from Leading Twist (LT) background, we use various ${\rho }_L$ meson distribution amplitudes (DAs). In the numerical calculations, the dependencies of the HT contribution on the transverse momentum and the rapidity are discussed with special emphasis on DAs. Analysis of our results shows that HT contributions decrease more rapidly than LT contributions with increasing $p_T$. The preceding results demonstrate that HT contributions must be considered especially in the region of low $p_T$ and the HT contribution to the cross-section depends on the choice of the meson DAs.

In this article, we investigate the contribution of the high twist Feynman diagrams to the large-p_T pion production cross section in proton-proton collisions and we present the general formulae for the high and leading twist differential cross sections. The pion wave function where two non-trivial Gegenbauer coefficients a₂ and a₄ have been extracted from the CLEO data, two other pion model wave functions, P₂, P₃, the asymptotic and the Chernyak-Zhitnitsky wave functions are used in the calculations. The results of all the calculations reveal that the high twist cross sections, the ratios R, r, the dependence transverse momentum p_T and the rapidity y of pion in the Φ_CLEO(x,Q²) wave function case is very close to the Φ_asy(x) asymptotic wave function case. It is shown that the high twist contribution to the cross section depends on the choice of the meson wave functions.

In this article, we investigate the contribution of the high twist Feynman diagrams to the large-p_T single pseudoscalar and vector mesons inclusive production cross section in two-photon collisions and we present the general formulae for the high and leading twist differential cross sections. The pion wave function where two non-trivial Gegenbauer coefficients a₂ and a₄ have been extracted from the CLEO data, Braun–Filyanov pion wave function, the asymptotic and the Chernyak–Zhitnitsky wave functions are all used in the calculations. For ρ-meson we used the Ball–Braun wave function. The results of the calculations reveal that the high twist cross sections, the ratio R, the dependence transverse momentum p_T and the rapidity y of meson in the Φ_CLEO(x, Q²) wave function case is very close to the Φ_asy(x) asymptotic wave function case. It is shown that the high twist contribution to the cross section depends on the choice of the meson wave functions.