Absolute & Relative Normalization

Paul E. Reimer

8 January 2009

1. Luminosity monitors

2. Calibrations

3. Targets composition

Based on Theses of R. Towell and J. Webb

28 January 2009Paul E. Reimer Absolute and Relative Normalization

Luminosity and Beam Monitors

Secondary emission monitors (SEM)

– Primary beam intensity monitor Ion chamber (IC)

– Secondary monitor Segmented wire ion chamber (SWIC)

– Position and profile monitor Scintillator telescopes (AMON, WMON)

– Viewed targets at 85o in lab through hole in shielding

Absolute calibrations?

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SEM vs. IC3

Not quite linear Calibration and/or offset

changes during dataset

Affects all targets in the same way.

Shifts can be isolated to particular times/jumps

Not significant problem for Ratio experiment

Deuterium (ic3+0)

Empty (ic3+2.5e4)

Hydrogen (ic3+5e4)

Linear relationship

Approx. 2000 SEM

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SEM linearity check

Plot sem vs. other luminosity monitors (amon and wmon)

Perform similar test with IC3

Deuterium

Empty

Hydrogen

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SEM Offset empirically determined

Should also be examined target-by-target

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SEM absolute calibration

Difficult—6.5% systematic uncertainty for E866/NuSea

Replace target with thin Cu foil Proton beam activates Cu foil creating 24Na Measure rate of 1368 keV ’s emitted by the 24Na Need 24Na production cross section

– Measured at 400 GeV, not 120 or 800 GeV

– 3.90 ± 0.11 mb (2.7% uncertainty already)

Can we do better????

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Target issues

Target Length

– Measure it—Write it down—Note which target it belongs to.

Target Density from target measured target pressure (see ref. in Webb’s thesis)

– Similar formula for deuterium

– Approx. 2% systematic for E866/NuSea

Target attenuation length

– PDG values for H2 and D2

– Also need HD for lD2 contamination

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Target Contamination

Analysis of D2 gas during fill done at Argonne (black box)

Approx 1% uncertainty in Absolute Luminosity

Approx 0.61% uncertainty in Ratio

– Tied with rate dependence for largest uncertainty

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Conclusion

Relative uncertainty dominated by target composition

– Obtain purest D2 we can get from Fermilab

Absolute uncertainty dominated by SEM calibration

– Better ideas??