Positron Asymmetry and Polarization from the E166 September 2005 run Gideon Alexander, Erez Reinherz-Aronis

Positron Asymmetry and Polarizationfrom the E166 September 2005 run

Gideon Alexander, Erez Reinherz-Aronis

E-166 - Princeton, May 2006

Gideon AlexanderErez Reinherz-Aronis

General

• In the analysis we considered only the Central Crystal (Crystal #5)

• We adopted the approach that by chaining all runs together the local variations are averaged out.



Selection of Runs and Events

• 1st stage:SuperRuns.Runs with Spectrometer and Lens values

Runs were rejected whenEmpty runs.Beam off.15 Hz runs.

Spectrometer [A] 100 120 140 160 180

Lens [A] 220 260 340 360 374

Positron energy [MeV]

3.65 4.38 5.11 5.84 6.57



Selection of Runs and Events

• 2nd stage :

Pairs of events were accepted by‘Trigger' word*. ‘Latch' word*.

*These are a result of a careful study of the 'agup', 'x5_1[0]' and 'x5_1[1] variables.

Note: Events with ADC above 4000 were filtered out.



Use of the toroid 6130• The toroid currents was used to define the appropriate range

of the data. Taking ±2σ range from an overall Gaussian fit.

• The analysis was then carried out with and without a Toroid normalization.

Positron Asymmetry• Event Pair : Signal*, Background (Bg).• Gaussian Fit in general is poor we use it only to define the sample

rage.• For each spectrometer value we calculate L and R

601601

)(1

)(1

magnets

N

iii

eventsmagnets

N

iii

events

eventsevents

BgSignalN

RBgSignalN

L

*Signal = Signal over Background (Signal + Bg)

RL

RLAsyor

BgSignalBgSignal

BgSignalBgSignalAsy

6060

6060

)()(

)()(



Asymmetry Error

R

R

L

L

NRR

R

NLL

L

LRRLRL

LRAsy

RL

RLAsy

11

)()()(

2 222

• For a Gaussian distribution:



Asymmetry Error

R

R

L

L

N

ii

NR

s

NL

s

RL

LRAsy

xxN

s

11

)(

2

)(1

1

22

2

1

222

• Note: Gaussian Fit in general is poor

• Calculate Sigma by

• so the Asymmetry error can be written as



Gain 1, Low sensitivity (12 bit)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

3 3.25 3.5 3.75 4 4.25 4.5 4.75 5 5.25 5.5 5.75 6 6.25 6.5 6.75 7

Positron Energy [MeV]

As

ym

me

try

[%

]

1 sigma

1 sigma / tor6130

1.5 sigma

1.5 sigma / tor6130

3 sigma

3 sigma / tor6130



Gain 1, High sensitivity (15 bit)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

3 3.25 3.5 3.75 4 4.25 4.5 4.75 5 5.25 5.5 5.75 6 6.25 6.5 6.75 7

Positron Energy [MeV]

As

ym

me

try

[%

]

1 sigma

1 sigma / tor6130

1.5 sigma

1.5 sigma / tor6130

3 sigma

3 sigma / tor6130



Positron Asymmetry

ee

e APP

Positron Polarization

Ae+ (extract) from Table 13, E-166 Proposal, June 2003.

~0.073

Positron Asymmetry and Polarizationfrom the E166 September 2005 run

Prof. Gideon Alexander, Erez Reinherz-Aronis



-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4 5 6 7 8 9 10



-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4 5 6 7 8 9 10



CsI

Analyzing magnet (-60/+60)

W-Target

Lens

SpectrometerSpectrometerSpectrometerSpectrometer

e-

e-

e-

γ

γ

Undulator

Bend magnets

SLC

e-

e-

Analyzing magnet (-60/+60)

γ detectors

E-166 @ FFTB (SLAC)

Backup 3



Backup - values for Polarization

Spectrometer [A] Ee+ Ae+

100 3.65 0.1931

120 4.38 0.1867

140 5.11 0.1688

160 5.84 0.1600

180 6.57 0.1585

Backup 4

Ae+ (extract) from Table 13, E-166 Proposal, June 2003 (Averages).



Backup – Toriod cutsSpectrometer [A] Low

limitHigh

limit

100 490 550

120 500 520

120 520 570

140 480 538

140 538 600

160 530 567

180 525 565

electrons 500 520

electrons 520 550

electrons 560 590

Backup 5

Documents

Positron Asymmetry and Polarization from the E166 September 2005 run Gideon Alexander, Erez Reinherz-Aronis