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Register a new userChiral Perturbation Theory Calculations For S-wave $pi^0$ production In pp Collision
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The total cross section for the pp --> pp $pi^0$ reaction at energies close to threshold is calculated within the frame of a chiral perturbation theory. The tree and one loop diagrams up to chiral order D=2 contributions are taken into account. The $L^{(0)}$ isoscalar-scalar part of t-channel two-pion exchange loop diagrams enhances the production amplitude strongly. The calculated cross section scale and energy dependence are very close to data.
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The total cross section for the $pp to pp pi^0$ reaction at energies close to threshold is calculated within the frame of a chiral perturbation theory, taking into account tree and one loop diagrams up to chiral order D=2. Two-pion loop contributions dominate $pi^0$ production at threshold. The calculated cross section reproduces data, both scale and energy dependence, fairly well.
The total cross section for the pp to pp $pi^0$ reaction at energies close to threshold is calculated in a covariant one-boson-exchange model. The amplitudes for the elementary BN to N$pi^0$ processes are taken to be the sum of s, u and t pole terms. The main contributions to the primary productionamplitude is due to a sigma meson exchange. Both the scale and energy dependence of the cross section are perfectly reproduced.
The $eta to pi^+ pi^- pi^0 gamma$ decay is discussed in the general context of Chiral Perturbation Theory (ChPT), assuming that the low--energy constants (counter--terms) are saturated by vector-meson resonances. The $eta to pi^+ pi^- pi^0 gamma$ amplitude can be separated in two distinct pieces: the inner bremsstrahlung, $A^{(IB)}$, and the structure dependent (or direct emission), $A^{(SD)}$, amplitudes. The former -- which essentially contains the same physics as $A(eta to pi^+ pi^- pi^0)$ -- is found to dominate over the second one -- which looks more interesting from the ChPT point of view.
We calculate the production cross-section and the transverse single-spin asymmetry for pion in $p^{uparrow}+pto pi^0 + X$. Our computation is based on existence of the instanton induced effective quark-gluon and quark-gluon-pion interactions with a strong spin dependency. In this framework we calculate the cross section without using fragmentation functions. We compare predictions of the model with data from RHIC. Our numerical results, based on the instanton liquid model for QCD vacuum, are in agreement with unpolarized cross section data. The asymmetry grows with the transverse momentum of pion $k_t$ in accordance with experimental observations. It reach value $sim 10%$ but at higher $k_t$ than experiment shows.
We report a measurement of the spin-dependent total cross section ratios delta_sigma_T/sigma_tot and delta_sigma_L/sigma_tot of the pp --> pp pi^0 reaction between 325 MeV and 400 MeV. The experiment was carried out with a polarized internal target in a storage ring. Non-vertical beam polarization was obtained by the use of solenoidal spin rotators. Near threshold, the knowledge of both spin-dependent total cross sections is sufficient to deduce the strength of certain participating partial waves, free of any model.
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