Miroslav Helbich, Columbia U.

1. Miroslav Helbich, Columbia U. Diffractive meeting 11.june 2003 Status of the exclusive in DIS analysis Srtd dead strips Acceptance study in Q2 - W plane Proton dissociation (update + decision for the preliminary) Discussion on the results to become preliminary Q2 distributions W distributions and (Q2) R(Q2) and R(W) Conclusions and outlook

2. Miroslav Helbich, Columbia U. Diffractive meeting 11.june 2003 Srtd dead channel problems Srtd y plane had too many dead channels in too periods indicated on the plots Run ranges are indicated on the plot This affects ~12pb-1 of data in 99/00 period No other serious problems seen

3. Miroslav Helbich, Columbia U. Diffractive meeting 11.june 2003 Acceptance in Q2 W plane W is measured from K+K- tracks Acceptance in W is determined by CTD acceptance For higher Q2 the acceptance moves to higher W 26.5+2.2 Q2 < W <106+0.72 Q4; W<160GeV Difference seen at the edges => put an offset of 8GeV for Wmin and 10GeV for Wmax

4. Miroslav Helbich, Columbia U. Diffractive meeting 11.june 2003 Proton dissociation update Following triggers can be used: - DIS05 box-cut 12x6cm, no FPC cut, FIR energy <5GeV, no prescale require flt46 p-diss sample = FPC Energy>1GeV Tune Mn spectrum to reproduce the FPC Energy or FPC Et ~350 events selected in Q2-W accepted region and |t|<2GeV - DIS01 box-cut 12x6cm, no FPC cut, no FIR energy cut, prescale =10 for 99/00 e+ data require flt46 Tune Mn spectrum to FPC or FIR (transverse) energy A good check for the dis05 trigger ~200 events selected in Q2-W accepted region and |t|<2GeV

5. Miroslav Helbich, Columbia U. Diffractive meeting 11.june 2003 Proton dissociation update Beta: - many parametrizations can describe the data with simmilar chi2 Beta = 0.4 (delta chi2 =1 => Beta = -0.8 - +1.3) Beta = a exp(-b|t|) more complicated parametrizations like Ariks (with different parameters) - b-slope Q2 dependence agrees with Ariks parametrization Results: - different parametrizations + changing measurement within errors lead to ~30% error on the expected number of p-diss events - overall normalization obtained from DIS01 and DIS05 triggers is consistent! Disclaimer: this is a fast study – don't rely on these results

6. Miroslav Helbich, Columbia U. Diffractive meeting 11.june 2003 Proton dissociation update p-diss is rising with Q2 and flat with W helicity distributions are the same => no impact on the R measurement For preliminary: subtract constant 7 ± 5% for Q2 and W cross-sections Treat Q2 dependence as a systematic check Disclaimer: this is a fast study – don't rely on these results

7. Miroslav Helbich, Columbia U. Diffractive meeting 11.june 2003 Q2 distributions Agreement with previous results fit to (Q2+m2)-n => n is the slope on the log-log plot Data suggest that n rises with n=2.1 ± 0.1(stat) for Q2<6GeV2 and n=2.6±01(stat) for Q2>6GeV2

8. Miroslav Helbich, Columbia U. Diffractive meeting 11.june 2003 W distributions measure W dependence in 4 Q2 bins W range defined by acceptance given before Improved precision on delta due to increased W range accepted Delta comes out to be consistent with soft delta = 0.2 behaviour Measurement changes with W range selected and with binning inside the range => systematics

9. Miroslav Helbich, Columbia U. Diffractive meeting 11.june 2003 W distributions – comparison with ICHEP98 Measured from the Last points are the most important ones ICHEP points given in “rounded” W => swimming of the data was done => this can lead to incorrect improvement of precision Single points are generally in agreement Data lead to different slopes

10. Miroslav Helbich, Columbia U. Diffractive meeting 11.june 2003 R(Q2) measurement Results unchanged Plot with finer binning made to see why are points at Q2~3GeV2 higher No change if one restricts cos(υh) range seen No work on improving the W dependence (swim the points to same Q2) => we may not need to show the plot – just say it in words

11. Miroslav Helbich, Columbia U. Diffractive meeting 11.june 2003 Plans for systematics Alignment of Srtd => highest systematics seen in previous studies Proton dissociation for Q2 dependence W range and binning dependence for W distributions (maybe shift vertex) Next steps Paper writing started – expect first draft by tomorrow Systematic checks by weekend Finalize results and talk for collaboration meeting early next week