# Presentation: 706372

## RunII DØ Luminosity Constant

- Tamsin Edwards, University of Manchester
- DØ Collaboration Workshop
- 27th Feb 2004

-    Introduction
-    Inelastic Cross-section
-    LM Acceptance
-    LM Efficiency
-    The New Luminosity Constant
-    Online Halo Correction
-    Conclusion

## Introduction

- Measure luminosity to normalise DØ analyses
- Instantaneous luminosity (b-1s-1):
- Effective inelastic cross-section, referred to as the **Luminosity Constant (mb):**

-    LM efficiency: extracted from data using forward calorimeter

-    LM acceptance: determined from MC

- rate of inelastic collisions

- DZero Collaboration Meeting

- 27th Feb 2004

## Inelastic Cross-Section            

-  Inelastic cross-section σpp measured at √s = 1.8TeV by three experiments at Fermilab: E710, E811 and CDF
-  Joint DØ/CDF working group formed ~1.5 years ago to combine into a  single number
-  One byproduct of the working group is the Klimenko-Konigsberg-Liss average  of E811 and CDF results:
**σ****pp**** = 60.7 ± 2.4mb (**√**s = 1.96 TeV) **
*S.Klimenko, J.Konigsberg, T.M. Liss,* FERMILAB-FN-0741 (2003)
-  Both DØ and CDF have chosen to adopt the KKL average
-  We note that other averaging techniques would shift the central value by 3% and increase the error by a factor of 1.2

- DZero Collaboration Meeting

- 27th Feb 2004

## Acceptance 

-  Geometric acceptance of LM detectors:	2.7 < |η| < 4.4

**North**
- (-ve η)

**South**
- (+ve η)

- p

-  Event is in acceptance if at least one charged particle hits each detector
-  Determined separately for different processes, assuming:
- Single Diffractive: 	σSD = 9.6 ± 0.5mb
- Double Diffractive: 	σDD = 7.2 ± 2.0mb
- Hard Core: 		σHC = 43.9mb

- measured by E811, CDF and E710

- defined as σpp − σSD − σDD

- DZero Collaboration Meeting

- 27th Feb 2004

## Generator Level Acceptances

-  Hard Core acceptances are similar
-  Diffractive numbers vary widely
-  Total inelastic acceptances agree between generators:
-  Some internal compensation between processes
-  Hard Core dominates the total acceptance

|  | MBR | DTUJET | PHOJET | PYTHIA |
| --- | --- | --- | --- | --- |
| HC | 0.911 | 0.949 | 0.924 | 0.943 |
| SD | 0.183 | 0.088 | 0.280 | 0.242 |
| DD | 0.563 | 0.642 | 0.570 | 0.321 |
| inelastic | 0.75 | 0.78 | 0.78 | 0.76 |

- Calculated with four MC generators:

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- 27th Feb 2004

## Detector Level Acceptances

|  | Pythia | MBR | Final |
| --- | --- | --- | --- |
| HC | 0.994 | 0.969 | 0.982 ± 0.013 |
| SD | 0.381 | 0.244 | 0.313 ± 0.137 |
| DD | 0.559 | 0.698 | 0.624 ± 0.130 |

- Detector Modelling:
- Pythia + full detector simulation
- MBR + parameterised detector model

- Hard Core: small generator level spread
-  δHC = ± 1⁄2  |Pythia - MBR|

- Diffractive: large spread
-  δSD,DD = ± |Pythia - MBR|

- DZero Collaboration Meeting

- 27th Feb 2004

## RunI comparison

- Increase in √s :60.7 ± 2.4 mb at 1.96 TeV is equivalent to 59.3 ± 2.3mb at 1.8TeV

|  | RunI | RunII |
| --- | --- | --- |
| Cross-sections (mb) | √s = 1.8TeV | √s = 1.96TeV |
| Inelastic | 57.55 ± 1.56 | 60.7 ± 2.4 |
| Single Diffractive | 9.57 ± 0.43 | 9.6 ± 0.5 |
| Double Diffractive | 1.29 ± 0.20  | 7.2 ± 2.0 |
| Acceptances |  |  |
| Hard Core | 0.97 ± 0.02 | 0.982 ± 0.013 |
| Single Diffractive | 0.15 ± 0.05 | 0.313 ± 0.137 |
| Double Diffractive | 0.72 ± 0.03 | 0.624 ± 0.130 |
| Aσpp (mb) | 47.70 ± 2.03 | 50.58 ± 3.01 |

- DZero Collaboration Meeting

- 27th Feb 2004

## LM Efficiency

- Two detectors, North and South, each with 24 scintillator wedges
- Charge from the wedges on each side are summed, and the total is discriminated
- Time difference between North & South classifies the event:
- Coincidence: ***FastZ***
- North before South: ***PHalo***
- South before North: ***Ahalo***
- LM efficiency:
- 	 εLM =  εN x εS x εFastZ
- εN(S)	North (South) detector efficiency: discriminator threshold
- εFastZ	FastZ efficiency: coincidence window |zvtx| < 97cm

- there are separate time windows for each, so an event may be none of these

- DZero Collaboration Meeting

- 27th Feb 2004

## Detector efficiency

-  Events with one detector off:
- Inefficient (lots of forward energy)
- Single diffractive (v.little forward energy)
-  Use sum of energy behind the off detector  to separate the two components

- Cell energy sum, (GeV)

-    Three separate subtraction methods      applied to different distributions

- good separation of noise & real energy

-    Checked stability to many variations:     bin width, cell energy threshold, η region,      tick dependence, data sample

- inefficient events

- noise distribution

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- 27th Feb 2004

## FastZ Efficiency

-  Events with both detectors on and FastZ off: [except those that fired Phalo/AHalo: see later, halo correction]
- Inefficient events: vertex outside ±97cm
- Beam losses hit LM
- Use energy sum distributions to separate the two components

- DZero Collaboration Meeting

- 27th Feb 2004

## Efficiencies

-  Detector efficiencies:
-  FastZ efficiency:
-  LM efficiency:
-  Comparisons:
- Monte Carlo cross-check:
- RunI:

- εN = 97 ± 1%
- εS = 95 ± 1.2%

- εFastZ = 98.6 ± 0.4%

- εLM = 90.9 ± 1.8%

- εLM (MC) = 93%

- εLM (RunI) = 90.7 ± 2%

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- 27th Feb 2004

## Final effective cross-section

-    New Luminosity Constant:

| Input | Contributed error (mb) |
| --- | --- |
| Inelastic | 2.14 |
| Single Diffractive | 0.30 |
| Double Diffractive | 0.65 |
| Hard Core | 0.50 |
| Single Diffractive | 1.20 |
| Double Diffractive | 0.85 |
| LM Efficiency | 0.91 |

- Cross-sections (mb)

- Acceptances

- - a 6.5% error

- DZero Collaboration Meeting

- 27th Feb 2004

## Online Halo Correction

-  Real interactions may be classified as PHalo or AHalo instead of FastZ:
- If beam losses hit the detectors during the same bunch crossing, the LM uses the early signal → no longer a North-South coincidence
-  A function of instantaneous luminosity
-  Probability of an interaction is independent of beam losses:

-     Scaler rates adjusted online:
-  Rate (inelastic corrected)  = Rate (inelastic) (1 + Rate (PHalo) + Rate (AHalo))
-  Rate (inelastic corrected)  = Rate (inelastic) - Rate (PHalo) x Rate (AHalo)
-                                                  (1 − Rate (PHalo)) x (1 − Rate(AHalo))

- 1st order

- full correction

- DZero Collaboration Meeting

- 27th Feb 2004

## Conclusion

-    DØ Technical note that will be referenced in publications:
-     *“**Luminosity Constant for D**Ø RunII”,**    * T.Edwards, S.Yacoob, Tim Andeen, Jaewon Park,
-      M.Begel, B.Casey, R.Partridge, H.Schellman, A.Sznajder

-    Example effect of new constant:     Previous inst. luminosity 22.02 x 1030cm-2s-1  →  21.33  x 1030cm-2s-1

-    One page summary: DØ Note 4328

- DZero Collaboration Meeting

- 27th Feb 2004