Beam helicity

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This page is considered done. It been reviewed by an expert. There may be missing elements, but they are all flagged and the text has no errors.

Intro

The LPOL is capable of measuring the helicity of the lepton beam. The sign of the polarization measured by the LPOL can therefore be used as an indicator of the helicity. Care has to be taken when changing the sign of the leptons from electrons to positrons.

Essentials

The helicity of the lepton beam for the different running periods is summarized in the following table.

HERA I running period Year First run Last run Lepton helicity 1995 1 7004 +1 1996 7005 14260 +1 1997 14261 21835 -1 21836 24380 +1 24381 28301 -1 1998 1 10548 -1 1999 1 1942 +1 1943 4208 -1 4209 9998 +1 9999 13303 -1 2000 1 6109 +1 6110 9404 -1 9405 13204 +1 13205 18168 -1 18169 22579 +1 22580 26713 -1 26714 30354 +1

HERA II running period Year First run Last run Lepton helicity 2002 1 4097 -1 2003 1 1472 +1 2004 1 4821 +1 4822 12047 -1 12048 16584 +1 2005 1 1755 +1 1756 15626 -1 15627 26035 +1 26036 44748 -1 2006 1 10958 -1 10959 43990 +1 43991 48195 -1 2007 1 17981 -1 17982 40840 +1

Obtaining beam helicity from uDST

This email from Elke describes how to obtain the beam helicity from the uDST entries.

More info

The information about the beam helicity can be found on the summary pages for every year, collected on the uDST documentation page.

Other beam related pages

• Beam charge
• Beam position
• Beam energy
• Beam polarization