1. Mean Charged Multiplicity in DIS, Michele Rosin U. WisconsinZEUS Monday Meeting, Apr. 18th 2005 1 Preliminary Request: Mean Charged Multiplicity in DIS M. Rosin, D. Kçira, and A. Savin University of Wisconsin ZEUS Monday meeting Preliminary request April 18th, 2005 http://www-zeus.desy.de/~sumstine/multip

2. Mean Charged Multiplicity in DIS, Michele Rosin U. WisconsinZEUS Monday Meeting, Apr. 18th 2005 2 Multiplicity: e + e - and pp  e+e- multiplicity plotted vs √s e+e- compared to pp multiplicity plotted vs 3 different values of √s pp  Remove the leading particles from the pp reactions and plot pp vs √q had 2  Agreement between e + e - and pp when plotted vs. pp invariant mass  Current analysis: Compare multiplicity measurements in ep to e+e- and pp e+e-:e+e-: pp(ISR) vs. √q 2 had pp(ISR) vs. √s pp

3. Mean Charged Multiplicity in DIS, Michele Rosin U. WisconsinZEUS Monday Meeting, Apr. 18th 2005 3 ep measurements in the current region of Breit frame  Previous ZEUS analysis compared e+e- (vs √s e+e- ) to ep in current region of the Breit Frame (vs. Q). Agreement for higher Q  This analysis: repeat the ep measurement in current region of Breit frame using 2*E current as scale. Better overall agreement with e+e- and pp. This method compensates for gluon migration into the target hemisphere. These points are already preliminary  Current region understood  look more closely at particles in the target region

4. Mean Charged Multiplicity in DIS, Michele Rosin U. WisconsinZEUS Monday Meeting, Apr. 18th 2005 4 Visible multiplicity in Breit and hadronic center of mass (HCM) frames  Breit Frame: 90% of hadrons in current region visible in detector, only 30% of target region hadrons are visible  HCM Frame: Particles in proton hemisphere unseen in detector. Photon region dominated by contribution from target region of Breit frame (~80% of visible hadrons) Visible Part All Hadrons Current Region Breit Frame Proton Region HCM Frame Photon Region HCM Frame Visible Part Proton remnant

5. Mean Charged Multiplicity in DIS, Michele Rosin U. WisconsinZEUS Monday Meeting, Apr. 18th 2005 5 Moving to the hadronic center of mass (HCM) frame Using HCM frame is intuitive because all interactions in e+e- and pp happen in the center of mass frame. Photon region of HCM frame has BIG contribution from target region of Breit frame To be consistent with Breit frame measurement we measure 2 vs. 2*E of correspondent hadronic system

6. Mean Charged Multiplicity in DIS, Michele Rosin U. WisconsinZEUS Monday Meeting, Apr. 18th 2005 6 2*E photon region = W in HCM frame Measure total energy in photon hemisphere of hadronic center of mass frame. By definition the total energy in each hemisphere is W/2. Plot 2*E / W vs. W & fit to line slope: 0.12 x10 -4 intercept: 1.00062 2*E photon region = W in HCM frame slope: 0.12 x10-4 intercept: 1.00062

7. Mean Charged Multiplicity in DIS, Michele Rosin U. WisconsinZEUS Monday Meeting, Apr. 18th 2005 7 Control Plots:W & Tracks  Data compared to both Ariadne and Lepto for W and Tracks  W: Both Lepto and Ariadne show general agreement with data, some disagreement at lower W.  Tracks: Lepto simulates track distribution and gives better description of tracks than Ariadne. W: LOG SCALE TRACKS: LINEAR SCALE W: LINEAR SCALE TRACKS: LOG SCALE

8. Mean Charged Multiplicity in DIS, Michele Rosin U. WisconsinZEUS Monday Meeting, Apr. 18th 2005 8 Control Plots: Tracks in W bins ARIADNE LEPTO W bin 1W bin 3W bin 2 W bin 3W bin 2 W bin 1 LEPTO ARIADNE Lepto has better overall agreement than Ariadne disagreement in highest W bin Ariadne shows disagreement in two highest W bins

9. Mean Charged Multiplicity in DIS, Michele Rosin U. WisconsinZEUS Monday Meeting, Apr. 18th 2005 9 Multiplicity vs. W in HCM frame (data and both Lepto and Ariadne)  Measurements in current region of Breit frame and photon hemisphere of HCM frame compared to both Lepto and Ariadne predictions  Disagreement between predictions and data in highest W due to poor simulation of track distributions at high W.  Lepto & Ariadne predictions agree well with each other in both frames  Number of observed hadrons is multiplied by Monte Carlo estimated corrections applied in each W bin (Factors: 1.9, 1.5, 1.3)  Largest systematic from MC (5% in highest W bin), Lepto points are above Ariadne  plot data on average

10. Mean Charged Multiplicity in DIS, Michele Rosin U. WisconsinZEUS Monday Meeting, Apr. 18th 2005 10 Significant Systematics SystematicChange % Difference in W bins W bin 1W bin 2W bin 3 Lepto vs. Ariadne <0.5%3.1%5.4% Matrix vs. Bin-by-bin <0.5%0.6%0.8% CAL energy scale+/- 3% <0.5% Electron energy cut+/- 1 GeV <0.5% Q 2 cut+/- 1.6 GeV <0.5% Vertex cut+/- 5 cm <0.5% E-pz cut+/- 5 GeV <0.5% Electron radius cut+/- 1 cm <0.5% y jb +/- 0.0006 <0.5% Track p T +0.05/-0.03 GeV <0.5%

11. Mean Charged Multiplicity in DIS, Michele Rosin U. WisconsinZEUS Monday Meeting, Apr. 18th 2005 11 Comparison to second analysis Current region hadronic center of mass frame vs. W  Monte carlo: Ariadne on left, Lepto on right  Agreement between 2 analysis good for both Ariadne and Lepto Second analysis done by D. Kçira

12. Mean Charged Multiplicity in DIS, Michele Rosin U. WisconsinZEUS Monday Meeting, Apr. 18th 2005 12 Multiplicity in current region of Breit and HCM frames compared to e+e- and pp  Measurement in current region of Breit frame agree with e+e- and pp points.  Measurement in photon hemisphere of HCM frame agrees with LEP points. Request for preliminary

13. Mean Charged Multiplicity in DIS, Michele Rosin U. WisconsinZEUS Monday Meeting, Apr. 18th 2005 13 Summary Request for preliminary:

14. Mean Charged Multiplicity in DIS, Michele Rosin U. WisconsinZEUS Monday Meeting, Apr. 18th 2005 14 Comparison to second analysis (Matrix method) Current region hadronic center of mass frame vs. W  Monte carlo: Ariadne on left, Lepto on right  Correction method: Matrix method  Agreement between 2 analysis good for both Ariadne and Lepto