Exclusive Vector Mesons at HERA Henri Kowalski DESY DIS 2006 Tsukuba, April 2006

1. Exclusive Vector Mesons atHERAHenri KowalskiDESY DIS 2006 Tsukuba, April 2006

2. GBW - Golec-B, Wuesthoff BGBK - Bartels, Golec-B, Kowalski KT - Kowalski, Teaney KMW - Kowalski, Motyka, Watt Dipole Models equivalent to LO perturbative QCD for small dipoles Glauber Mueller proton shape

3. Total g*p cross-section KT KMW universal rate of rise of all hadronic cross-sections x < 10-2

4. Dipole cross section determined by fit to F2 simultaneous description of many reactions Inclusive Diffraction F2 C -LPS KT BGBK

5. Exclusive Vector Meson Production H. Kowalski, L. Motyka, G. Watt Effective modification of Fourier Trans by Bartels, Golec-Biernat, Peters Real part correction Skewedness correction Martin, Ryskin Teubner

6. Wave Functions WF Overlaps Boosted Gaussian – NNPZ, FS Gaussian distribution of quark 3-momentum in the meson rest frame then boosted to LC Gauss LC - KT Gaussian distribution of quark 2-momentum in LC, factorization of r, z components - strong endpoint suppression infT Parameters of WF fixed by normalization conditions and the values of mesons decay constant, fV

7. WF Overlaps integrated over z • Boosted Gaussian • different fV • for T and L • Gaus-LC • different R • for T and L • Differences in fV • for Boosted Gaussian • sizably smaller than • dfferences in R for • Gaus-LC • Boosted Gaussian • more consistent • than Gaus-LC

8. KMW

9. KMW

11. Description of the size of interaction region BD Modification by Bartels, Golec-Biernat, Peters KMW proton size BG BG

12. KMW

14. KMW

15. Sensitivity to end points suppression of the r wave function

16. a’ ~ 0.1

17. QCD Evolution within Dipole Sat-Models DSM with DGLAP(BGBK) + b-dependence(KT, KMW) — b-Sat DSM with CGC-BFKL(IIM) + b-dependence(KMW+IIM) — b-CGC model IIM Iancu Itakura Munier

18. Advantage of b-CGC ρ-meson BD ? Advantage of b-Sat

19. Saturation scale (a measure of gluon density) b-frequency In b-Sat (b-CGC) there are substantial saturation effects in the proton center but only limited part of x-section is in saturated region

20. b-independent proton shape? instead of J/Psi t-distributions clearly prefer Gaussian proton shape ρ-meson t-distributions?

21. Conclusions we are developing a very good understanding of inclusive and diffractive DIS interactions: F2 , F2D(3) , F2c , Vector Mesons (J/Y,f,r) we obtain a good description of Q2, W and t dependence of r, f, and J/Y vector meson cross sections with a simple wave function ansatz HERA measurements suggests presence of Saturation phenomena Saturation scale determined at HERA, in the proton center, agrees with RHIC ____________________________________________________ Diffractive vector mesons scattering - an excellent probe of nuclear matter, ---- Measure t distribution on polarized nuclei ----- >>>> Obtain holographic picture of nuclei !!!! <<<<< Possible device: e-RHIC like machine with ~1/3 of HERA energy

22. Dipole Models equivalent to LO perturbative QCD for small dipoles Optical T Inclusive DIS Hard Diffraction Glauber Mueller GBW – first Dipole Saturation Model Golec-Biernat, Wuesthoff BGBK – DSM with DGLAP Bartels, Golec-Biernat, Kowalski IIM - BFKL-CGC motivated ansatzIancu, Itakura, Munier FS – Regge ansatz with saturation Forshaw and Shaw