1. The Diffractive Structure Function: ξ dependence Christina Mesropian The Rockefeller University

2. December 02, 2003Christina Mesropian The Diffractive Structure Function Single Diffractive dissociation Subject of interest: Hard diffraction process: production of high p T dijets p x p - p - P Study the diffractive structure function Regge factorization:

3. December 02, 2003Christina Mesropian The Diffractive Structure Function Measure ratio of SD to ND 2 dijet samples: SD: diffractive – leading pND: non-diffractive then known ND structure function -

4. December 02, 2003Christina Mesropian discrepancy in normalization factorization breakdown The Diffractive Structure Function Power Law dependence

5. December 02, 2003Christina Mesropian The Diffractive Structure Function: Run I contributions from reggeon exchange in 0.035<ξ<0.095 range ξ dependence if reggeon has different structure than pomeron change in shape for R as a function of x SD ND no ξ dependence

6. December 02, 2003Christina Mesropian The Diffractive Structure Function: Run 2: to study ξ dependence for low ξ (<0.035) values events without hits in BSC on the p or p side - rapidity gaps East West BSC gap requirement dijets

7. December 02, 2003Christina Mesropian Beam Shower Counters: scintillation counters around the beam pipe detect particles traveling in direction from interaction point along beam pipe 5.5 < |η| <7.5 coverage The Diffractive Structure Function: Run 2: Hardware BSCs provide East and West gap triggers:

8. December 02, 2003Christina Mesropian The Diffractive Structure Function: Run 2: Trigger gap trigger rate decreases with increasing luminosity – additional interactions “kill” gap Trigger namePSRate (Hz) Cross Section Level 1 L1_GAP_WEST_JET51101.212.8 μb Level 2 L2_PS500_L1_GAP_WEST_ &_JET5 5000.2027.6 nb L2_JET15_&_L1_GAP_WES T_PS50 500.2534.3 nb L2_JET40_&_L1_GAP_WES T 11.63223.0 nb Level 3 DIFF_GAPW_ST510.2027.4 nb DIFF_GAPW_JET2010.1115.3 nb DIFF_GAPW_JET5010.1925.5 nb MBR Monte Carlo simulation

9. December 02, 2003Christina Mesropian The Diffractive Structure Function: Run 2 determination of ξ: from the information of final state particles in the diffractive mass system X X pp _ η → information from calorimeters: forward calorimeters: MiniPlugs: 3.5<|η|<5.1 low ξ values 0.001 < ξ possibly…

10. December 02, 2003Christina Mesropian The Diffractive Structure Function: Run 2 Tighter cut on BSCW gap for cross reference with RP+Jet data sample

11. December 02, 2003Christina Mesropian The Diffractive Structure Function: Run 2 Cleaner sub-sample Request MP west gap 0-0 bin corresponds to BSCW+MPW gap sub-sample

12. December 02, 2003Christina Mesropian The Diffractive Structure Function: Run 2 Strategy for the analysis: calculate ξ for each event separate clean diffractive sample: calculate x for dijet system compare with ND Jet5 sample cross checks with RP + Jet5 sample different Q 2 samples for the same trigger… BSCW- Gap + Jet Sample 0.001 < ξ

13. December 02, 2003Christina Mesropian Summary FACT: New possibility to extend ξ range down to 0.001 for Q 2 100 GeV 2 QUESTION: Will the ξ distribution at the Tevatron be the same as at HERA at very low ξ? ANSWER: New results from CDF Run 2 data coming soon!