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Correlations in double parton distributions at small x

Correlations in double parton distributions at small x. András Ster. MTA KFKI RMKI, Budapest, Hungary Dept. of Astronomy and Theoretical Physics, Lund University, Sweden. Content. Introduction Double Parton Scattering & Double Parton Distributions The Lund Dipole Cascade Model

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Correlations in double parton distributions at small x

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  1. Correlations in double parton distributions at small x András Ster MTA KFKI RMKI, Budapest, Hungary Dept. of Astronomy and Theoretical Physics, Lund University, Sweden

  2. Content • Introduction • Double Parton Scattering & Double Parton Distributions • The Lund Dipole Cascade Model • Application to Double Parton Distributions • Results • Summary

  3. Introduction - Motivation Multiple hard parton (q,g) collisions are common in high energy pp collisions • For example: • 4 jets in 63 AGeV events @ CERN ISR (AFS) • 4 jets and 3 jets +  in 1.8 TeV events @ Tevatron (CDF, D0) Larger probability found than expected for uncorrelated hard subcollisions ? @ LHC

  4. Literature Connection between correlations in momentum and impact parameter (b) space have not yet been studied

  5. Correlation studies Earlier Sjöstrand and van Zilj assumed that the dependence of double-parton density on kinematic variables (x, Q2) and on the separation in impact parameter space (b) factorizes. Implemented in PYTHYA and HERWIG event generators Problem: how to extrapolate to higher energies (LHC) Our solution: detailed dynamical model for parton evolution (Lund Dipole Cascade Model)

  6. Correlation studies Lund Dipole Cascade Model Based on BFKL and Müller’s dipole cascade model Correlation sources in the model: 1) from fluctuations (event by event) 2) “hot spots” makes the profile narrower

  7. Double Parton Scattering & Double Parton Distributions - Experimental results Measure of correlation is defined by eff according to D(A,B) is the cross-section of the two hard processes SA and SB are the single inclusive cross-sections If hard interactions were uncorrelated, eff would be equal to the total non-diffractive corss-section

  8. Experimental results Tevatron (CDF, D0) results: eff 15 mb CERN ISR (AFS) results: eff 5 mb

  9. Essential formulae The formalism: Stirling and Gaunt:

  10. The Lund Dipole Cascade Model We define: With the constraint:

  11. The Lund Dipole Cascade Model Dipole cascades:

  12. The Lund Dipole Cascade Model We define: With the constraint:

  13. Results

  14. Results

  15. Results

  16. Results

  17. Results

  18. Results

  19. Results

  20. Summary Lund Dipole Cascade Model offers unique possibility to study gluon evolution inside hadrons at small x In our analysis we have found that the two-parton correlation function F(b) in a non-trivial way on all kinematic variables x1,x2,Q21,Q22 Our results show a non-flat energy dependence within errors compatible with experiments in their energy range.

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