mean charged multiplicity in dis, michele rosin u. wisconsinzeus monday meeting, apr. 18th 2005 1...

Mean Charged Multiplicity in DIS, Michele Rosin U. Wisconsin ZEUS Monday Meeting, Apr. 18th 2005 1

Preliminary Request: Mean Charged Multiplicity in DIS

Preliminary Request: Mean Charged Multiplicity in DIS

M. Rosin, D. Kçira, and A. SavinUniversity of Wisconsin

ZEUS Monday meetingPreliminary request

April 18th, 2005http://www-zeus.desy.de/~sumstine/multip


Multiplicity: e+e- and ppMultiplicity: e+e- and pp

e+e- multiplicity plotted vs √se+e- compared to pp multiplicity plotted vs 3 different values of √spp

Remove the leading particles from the pp reactions and plot pp vs √qhad2

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-:

pp(ISR) vs. √q2had

pp(ISR) vs. √spp

2 eeeepps

2pppp pps

22211

2 leadingincleadinginchadtot qqqqq


ep measurements in the current region of Breit frame

ep measurements in the current region of Breit frame

Previous ZEUS analysis compared e+e- (vs √se+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*Ecurrent 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


Visible multiplicity in Breit and hadronic center of mass (HCM) frames

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

All Hadrons

Current Region Breit Frame

Proton Region HCM Frame

Photon Region HCM Frame

Visible Part

Proton remnant


Moving to the hadronic center of mass (HCM) frame

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<nch> vs. 2*E of correspondent hadronic system


2*Ephoton region = W in HCM frame2*Ephoton 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*Ephoton region= W in HCM frame

slope: 0.12 x10-4

intercept: 1.00062


Control Plots:W & TracksControl 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


Control Plots: Tracks in W binsControl Plots: Tracks in W bins

ARIADNE

LEPTO

W bin 1 W bin 3W bin 2

W bin 3W bin 2W bin 1

LEPTOLEPTO

ARIADNEARIADNE

Lepto has better overall agreement than Ariadne

disagreement in highest W bin

Ariadne shows disagreement in two highest W bins


Multiplicity vs. W in HCM frame(data and both Lepto and Ariadne)

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


Significant SystematicsSignificant Systematics

Systematic Change% Difference in W bins

W bin 1 W bin 2 W 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% <0.5% <0.5%Electron energy cut +/- 1 GeV <0.5% <0.5% <0.5%Q2 cut +/- 1.6 GeV <0.5% <0.5% <0.5%Vertex cut +/- 5 cm <0.5% <0.5% <0.5%E-pz cut +/- 5 GeV <0.5% <0.5% <0.5%Electron radius cut +/- 1 cm <0.5% <0.5% <0.5%

yjb+/- 0.0006 <0.5% <0.5% <0.5%

Track pT+0.05/-0.03 GeV <0.5% <0.5% <0.5%


Comparison to second analysisComparison to second analysis

Current region hadronic center of mass frame vs. WMonte carlo: Ariadne on left, Lepto on right

Agreement between 2 analysis good for both Ariadne and Lepto

Second analysis done by D. Kçira


Multiplicity in current region of Breit and HCM frames compared to e+e- and pp

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


SummarySummary

Request for preliminary:


Comparison to second analysis (Matrix method)

Comparison to second analysis (Matrix method)

Current region hadronic center of mass frame vs. WMonte carlo: Ariadne on left, Lepto on right

Correction method: Matrix method

Agreement between 2 analysis good for both Ariadne and Lepto

mean charged multiplicity in dis, michele rosin u. wisconsinzeus monday meeting, apr. 18th 2005 1...

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