Energy Dependence of the Pomeron Spin-flip * How to Measure the Pomeron Spin-flip?

نویسندگان

  • B. Z. Kopeliovich
  • B. Povh
چکیده

There is no theoretical reason to think that the spin-flip component of the Pomeron is zero. One can measure the spin-flip part using Coulomb-nuclear interference (CNI). Perturbative QCD calculations show that the spin-flip component is sensitive to the smallest quark separation in the proton, while the non-flip part probes the largest separation. According to HERA results on the proton structure function at very low x the energy dependence of the cross-section correlates with the size of the color dipole. Analysing the data from HERA we predict that the ratio of the spin-flip to non-flip amplitude grows with energy as r(s) ∝ (1/x) 0.1−0.2 , violating Regge factorisation of the Pomeron. The Pomeron contribution to the elastic scattering amplitude of a spin 1/2 particle has a form, f P (s, t) = f P 0 (s, t) 1 + i √ −t m N σ n r(s, t) (1) The function r(s, t) characterises the Pomeron spin-flip to non-flip ratio. In the case of N N elastic scattering r can be expressed through the spin amplitude in standard notations, r = 2m N √ −t Φ 5 Im(Φ 1 + Φ 3) (2) If the Pomeron is a Regge pole (factorisation holds), the spin-flip and non-flip amplitudes have the same phase, i.e. r is pure imaginary. Either this is true, or Re r ≪ 1. Indeed, a real part of r would lead to a polarisation in elastic due to " self-interference " of the two components of the Pomeron, A pp N (t) = √ −t m N 4Re r(t) 1 + |r| 2 |t| /m 2 N ,

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تاریخ انتشار 1998