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Register a new user$J/Psi$-Production at Photon-Photon Colliders as a Probe of the Color Octet Mechanism
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We study $J/Psi$ production at photon-photon colliders, which can be realised with Compton scaterring of laser photons at $e^+e^-$ colliders. We find that the production rate through the color-octet channel is comparable to that through the color-singlet channel. Experimentally the two mechanisms can be studied separately because the processes have different signals.
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The DELPHI Collaboration has recently reported the measurement of J/Psi production in photon-photon collisions at LEP II. These newly available data provide an additional proof of the importance of colored c bar{c} pairs for the production of charmonium because these data can only be explained by considering resolved photon processes. We show here that the inclusion of color octet contributions to the J/Psi production in the framework of the color evaporation model is able to reproduce this data. In particular, the transverse-momentum distribution of the J/Psi mesons is well described by this model.
We consider J/psi photoproduction in e+ e- as well as linear photon colliders. We find that the process is dominated by the resolved photon channel. Both the once-resolved and twice-resolved cross-sections are sensitive to (different combinations of) the colour octet matrix elements. Hence, this may be a good testing ground for colour octet contributions in NRQCD. On the other hand, the once-resolved J/psi production cross-section, particularly in a linear photon collider, is sensitive to the gluon content of the photon. Hence these cross-sections can be used to determine the parton distribution functions, especially the gluon distribution, in a photon, if the colour octet matrix elements are known.
To test the color-octet model of heavy quarkonium productions, we propose $psi $-productions at small-$p_T$ regions in polarized $pp$ collisions for the forthcoming RHIC polarized experiments, whose experimental test at $sqrt s=50$ GeV might be very promising.
The cross sections of the scalar meson $f_0(980)$, $a_0(980)$ and $sigma(600)$ production in collision of electron and positron beams were calculated. The two-photon decays of the scalar mesons, obtained in the framework of the Nambu-Jona-Lasinio model, were used. The quark and meson loops were taken into account.
We calculate the next-to-leading order (NLO) quantum chromodynamics (QCD) correction to the exclusive process $gamma+gammato J/psi+J/psi$ in the framework of non-relativistic QCD (NRQCD) factorization formalism. The cross sections at the SuperKEKB electron-positron collider, as well as at the future colliders, like the Circular Electron Positron Collider (CEPC) and the International Linear Collider (ILC), are evaluated. Numerical result indicates that the process will be hopefully to be seen by the Belle II detector within the next decade.
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