Abstract
We study the rapidity dependence of the central exclusive production cross sections of C-even mesons in pA and AA collisions, where A is a heavy ion. We observe qualitatively different behaviour of the contributions arising from gamma -Odderon and Pomeron–Pomeron fusion mechanisms. This can be used to extract the Odderon signal from the events of f_2 mesons exclusively produced in the forward region. Estimates, obtained using expected values of the Odderon cross section, indicate that the gamma -Odderon contribution may exceed by a few times the Pomeron-induced background in Pb–Pb collisions. Moreover, the Odderon effect can be clearly seen in terms of the asymmetry in pA and AA collisions with the beam and target reversed. It is particularly interesting to note that the asymmetry for gamma -Odderon fusion reaches its maximum value close to 1 in the forward direction, whereas the asymmetry for the Pomeron–Pomeron fusion contribution is small. The role of additional interactions of the f_2 meson with nucleons in the heavy ion, and also the contributions from secondary Reggeons, are estimated. The photon–Odderon contribution has a large normalisation uncertainty but the enhanced cross-section in the forward region combined with a large asymmetry increases the chance of experimentally detecting the Odderon.
Highlights
This type of process can be used to search for the Odderon.1 In particular we study the possibility of searching for Odderonexchange in ultraperipheral p A collisions at the LHC, where A is a heavy ion [19]
We find a large asymmetry for f2 production through photon–Odderon fusion that is largely absent in the background Pomeroninduced processes
Since the R-exchange cross section decreases with energy the R-exchange contribution is larger for kinematics in which the f2 meson goes in the ion direction; adding some positive component to the asymmetry A( p A)
Summary
We have to emphasize that in the f2 → π +π − decay mode there is a large background coming from the direct π +π − ultraperipheral photoproduction and the higher mass tail of the ρ meson which can be produced via the photon– Pomeron fusion with a quite large cross section. 6 we perform numerical calculations to give indications of the size of the cross sections and asymmetries expected for p A → p + f2 + A and A A → A + f2 + A∗ by making physically reasonable assumptions for the unknown parameters We consider both the Pomeron–Pomeron and the photon-induced fusion mechanisms. A A collisions and considering the asymmetry of the crosssection with respect to rapidity, its effects can be enhanced
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