# Presentation: 901939

## Inclusive Differential pT Cross Section 

- for the *Z* boson

- Dylan Casey
*University of Rochester*
*for the*
- DØ Collaboration

- 1997 Joint April APS/AAPT Meeting
- and CAM ‘97
- 18-21 April 1997
- Washington, DC

## Motivation and Theory

- Improve M*W* precision by constraining vector boson production parameters
- Test vector boson production phenomenology
- Ladinsky-Yuan(1993); Arnold-Kaufman(1990); Altarelli-Ellis-Greco-Martinelli(1984)
- parameterize low *p**T* (<30 GeV/c) behavior as
*g**1*, *g**2*, and *g3 *values obtained from high statistics low energy Drell-Yan data and CDF *p**T*(Z) data from 1989 Collider Run (365 events)
- Most sensitive to *g**2* in region near M*Z*
- Test QCD/ Search for new physics at high *p**T*

## Data Selection and Reconstruction

- Fiducial and Kinematic requirements
- |h|<1.0 (Central Calorimeter; CC) and
- 	1.5<|h|<2.5 (End Cap Calorimeter; EC)
- not within 5% of j module boundary for |h|<1.0
- E*T*>25 GeV
- 76<Mee<106 GeV/c2
- Electron Quality and Tracking
- isolated object
- transverse and longitudinal shape consistent with an electron
- at least one of the two electron candidates must have a track that matches well with the calorimeter cluster
- 2188 events with two central electrons (CCCC)
- 1818 events with one central electron and one forward electron (CCEC)
- 4006 events total

- CCCC

- CCEC

## Measurement Components

- Goal: Measure smeared cross section as a function of *p**T *(ds/d*p**T*) and compare to smeared theory
- Account for *p**T* dependent corrections
- Acceptance; fiducial and kinematic requirements
- Identification efficiency; e- quality requirements
- Background
- Determine cross section in *p**T* bins
***s******i****** = (d******i ******- b******i ******)/ a******i ******e******i***
*s**i* = cross section in bin *I*
*d**i* = data events in bin *i;* *b**i* = background in bin *i*
*a**i* = acceptance for bin *i;**e**i* = efficiency for bin *i*
- Normalize to total cross section to account for non- *p**T* dependent corrections

## Acceptance

- Use parameterized detector simulation
- Include trigger turn on, E*T* cut, hcut, f cut
- Fit to fifth order polynomial
- Errors from MC statistics only

## Background	

- QCD type events primary background
- jj/gj contributions » 50/50
- s(gj)/s(jj) » 10-3; Probability(j->e) » 10-3
- Use gj data to get shape of background in *p**T* and invariant mass
- High statistics
- 50% gj purity
- Fit invariant mass to Breit-Wigner convoluted with a Gaussian over a fixed background
- CCCC exponential
- CCEC quadratic
- Add *p**T* distributions from different topologies according to their relative contributions to the background

## Background Level

*f*back(CCCC) = 0.046+/-0.007
*f*back(CCEC) = 0.036+/-0.011

## Background Shape

## Identification Efficiency

- e- quality cuts are less efficient if the 	hadronic activity in the event is close to 	the electron
- Effect parameterized for *p**T *< 30 GeV/c 	in terms of total hadronic recoil
- Data + Geant e-
- Good agreement between data and MC for 	 e- cluster shapes
- Extend to higher *p**T* using HERWIG MC 	+ GEANT e- + zero bias data
- Fit to cubic and use fit values for e*i* in  	the cross section calculation
- Errors from MC statistics only

## Identification Efficiency

- solid    =  total recoil parameterization
- dashed = HERWIG + zero bias data (3x1030 pb-1)
- dotted  = HERWIG + zero bias data (14x1030 pb -1)

- Ratio of recoil parameterization/HERWIG

## Identification Efficiency

- Fit to third order polynomial
- Errors from MC statistics only

## Preliminary Results

- solid    = Data
- dashed = Arnold-Kaufman (MRSA)
- dotted  = Ladinsky-Yuan (MRSA)

- Comparing phenomenology to data
- c2/dof (Arnold-Kaufman)	 = 86/20
- c2/dof (Ladinsky-Yuan)	 = 16/20

## Conclusion

- All results preliminary
- Future plans
- unsmear data
- Fully determine systematic uncertainties
- Fit for optimal values of non-perturbative parameter, *g**2*
- Extend to *p**T* > 100 GeV/c