# Presentation: 804052

##  Distributions

- Veronica Sorin
- Universidad de Buenos Aires
- DØ RunI Meeting,
- August 18, 2000

## Outline

- Introduction
- Motivation
-      Definition
- Goals
- MC and Data samples
- Systematic Errors
- Comparison with JETRAD predictions
- Plans

## Event Shapes

- Extensively studied at *e**+**e**-* and *ep*
- experiments:
- test QCD
- sensitive to resummations and non-perturbative effects
- measurement of αs

- Non-perturbative effects:
- Power-corrections, of the order of 1/Q .
- Related with hadronization effects.
- Resummations:
- at small values of the shape variable (two-jet limit)
- fixed-order perturbative calculations are not reliable.
- That’s because of the presence of large logarithms due
- to the emission of soft and collinear gluons.

## Thrust

- _Thrust_

**The sum is over all particles/towers/jets/subjets in the event**

**: ****direction which**
** ****maximizes   T**

-     transverse momenta
** **

- _T in Hadron Colliders_ :
- Busy environment: underlying event, pile-up, multiple interactions

-   3D                        2D

-   Transverse Thrust :

-   particles                      jets

-  calculate T using only the 2 leading jets  ( T2 )

## Measurement of        distributions
Data vs Herwig 
Comparison with LO (JETRAD) and NLO QCD  (program recently available) predictions.

- Data vs Herwig
- Comparison with LO (JETRAD) and NLO QCD  (program recently available) predictions.

- We’ll analyze the need of **resummations** on
- the LO and NLO theoretical calculations
- in the limit
- due to the presence of  large logarithms

## MC Samples

- HERWIG Generator:
-  	- parton   0.9
-     - partonET30,50,75,110,150 (GeV)
- Detector Simulation (Showerlib)
- Overlayed with zerobias and minimum bias events
- min_bias: crossing with inelastic interaction (underlying event), low lum
- zero_bias: just a crossing (Noise, pileup, extra  pp ), various lum.

- D = 1

- _Jet Reconstruction_

**K ****T**** algorithm: infrared safe at all orders**

## DATA Samples

- Run Ib , Triggers : Jet_30, Jet_50, Jet_85, Jet_Max
- Cuts:
- 	- jet quality cuts
-     • 0.05 < *EM fraction *< 0.95
-     • *CH fraction *< 0.4
-     • _*missing E*_*T    **< 0.7*
- 	   *E**T* *(jet 1)*
*- | vertex_z | ****	**50 cm*
- - Remove “bad” runs

-  || < 1, | 
-   4 HT3 bins
- (HT3 : scalar sum of the transverse
- momentum of the three leading jets)

## Triggers Turn On

## Corrections and Systematic Errors

-  Energy Scale
-  Misvertexing
-   η bias
-  Resolutions

- We can estimate the global effect by means of a study of luminosity dependence.

- Integrated luminosity for each subsample from the PDB.
- We analyzed “cross section” ratios of:  ET1 (leading jet), ET2, ET3 and HT3, requiring the trigger to be fully efficient.
- Any luminosity dependence will affect either
- the shape or the normalization , or both.

## Comparison with JETRAD

- JETRAD : LO prediction for

- Lower limit :

-  _NLO prediction_

- It will improve the prediction at low values of

## Plans 

-  We have studied almost all the systematics :
-  Energy Scale : 10-15%
-  Misvertexing, Vertex Resolution:              small corrections
-  Good agreement between Data and Herwig.
-  Comparison with Jetrad shows that the variable is sensitive to resummations and higher order effects
-  To Do :
-  quantitative studies of systematics
-  comparison with NNLO QCD prediction
-  Goal:
-            approval for winter or spring conferences,
-            publication for the summer.

## [10] K. Rabbertz and U. Wollmer,  hep-ex/0008006

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- [6] H1 Collaboration (C. Adloff et al.), Phys. Lett. B 406 (1997) 256 [hep-ph/9706002]
- [7] S. Catani, L.Trentadue, G. Turnock and
-  B.R. Webber, phys. Lett B 263 (1991) 491.
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- [10] K. Rabbertz and U. Wollmer,  hep-ex/0008006