Proton Polarimetry at RHIC

K. Oleg Eyserfor the CNI polarimeter group

Newport News, VA, October 25, 2013

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@ RHIC

AGSAGSLINACLINACBOOSTERBOOSTER

Polarized Source

Spin Rotators

200 MeV Polarimeter

Absolute Polarimeter (H jet)

PHENIX

BRAHMS & PP2PP

STAR

Siberian Snakes

Siberian Snakes

Spin Flipper

RHIC pC Polarimeters

Rf Dipole AGS Internal Polarimeter

AGS pC Polarimeter

Strong SnakePartial Snake

Helical Partial Snake

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RHIC Luminosity

Beam momentum100 GeV250 GeV

Consistent luminosity improvement over the years

255 GeV in 2013

Significance: Figure of Merit

or

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Polarization and Asymmetries

𝐴𝑁=𝑑𝜎 𝑙𝑒𝑓𝑡−𝑑𝜎 h𝑟𝑖𝑔 𝑡

𝑑𝜎 𝑙𝑒𝑓𝑡+𝑑𝜎 h𝑟𝑖𝑔 𝑡

S

x

y

NP

Polarization:

𝜀=𝐴𝑁 ∙𝑃=𝑁 𝐿−𝑁𝑅

𝑁 𝐿+𝑁𝑅

𝒔𝒛=𝑵

𝒑=𝑳

left

right

scattering plane

𝑠𝑧=±12ℏ𝑃=𝑛↑−𝑛↓

𝑛↑+𝑛↓

(proton)

(proton)(Carbon)

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Polarimeters in RHIC

Carbon polarimeters

Two per ring

Fast measurement

Beam polarization profile

Hydrogen jet

Polarized target

Continuous operation

per fill

normalization

Carbon polarimeters

Hydrogen jet

beam

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Elastic Signal Identification

𝐸𝑘𝑖𝑛=12𝑚𝑣2=1

2𝑚(𝑑𝑡 )

2

ADC/TDC waveform readout

normalized to peak

ADCmax

TDC0

V10BASELINE

Elastic signal

→ Energy calibration

→ Time offset

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Energy Calibration

𝑐 ∙ 𝐴=𝐸𝑚𝑒𝑎𝑠=𝐸𝑘𝑖𝑛−∆𝐸

∆𝐸𝛼(𝐴𝑚 )=0.72∙∆𝐸𝛼 (𝐺𝑑)

Two different α-sources

Stopping power forα-particles and protons from NIST database

∆𝐸𝑃=0.44 ∙∆𝐸𝛼 (𝐺𝑑) ∙𝐸[𝑀𝑒𝑉 ]−0.64

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Elastic Signal and Background

5 MeV

1 M

eV

signal region background region

atomic jet target

proton beam

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Asymmetry and Polarization

⇒

𝜀=𝜀𝑖𝑛𝑐−𝑟 ∙𝜀𝑏𝑔1−𝑟

What if

𝑃 𝐵𝑒𝑎𝑚=−𝜀𝐵𝑒𝑎𝑚𝜀𝑇𝑎𝑟𝑔𝑒𝑡

𝑃𝑇𝑎𝑟𝑔𝑒𝑡𝑃 𝐵=

𝜀𝐵𝜀𝑇𝑃𝑇𝑃𝑌=

𝜀𝑌𝜀𝑇𝑃𝑇

Polarization independent background

Polarization dependent background

background fraction

+

-

+

- +

-

+

-

+

-

+

-

+

-

+

-

+

+

+

+

+

+

+

-

-

-

-

-

+

+

+

-

abort gaps

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Polarimeter PerformanceKinematic distributions for consistency checks

Fast feedback to RHIC operations

Target P=92%

1 Fill

over 150 RHIC fills in 2013

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Summary

Polarization in RHIC is measured with fast p+C targets for monitoring, polarization profiles,

and polarization decay, a polarized atomic hydrogen jet for normalization.

The 2013 data provides unprecedented possibilities to use the jet polarimeter for background studies.

The jet polarimeter provides fast feedback to RHIC operations.

Final analysis and systematic studies are on-going.

https://wiki.bnl.gov/rhicspin/RHIC_Spin_Group

BACKUP

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Polarization Profile

𝑃𝑐𝑜𝑙𝑙=∫𝑑𝑥𝑑𝑦𝑃 (𝑥 , 𝑦 ) 𝐼𝐵 (𝑥 , 𝑦 ) 𝐼𝑌 (𝑥 , 𝑦)

∫𝑑𝑥𝑑𝑦 𝐼𝐵 (𝑥 , 𝑦 ) 𝐼𝑌 (𝑥 , 𝑦 )

𝑃 𝑗𝑒𝑡=∫𝑑𝑥𝑑𝑦𝑃 (𝑥 , 𝑦 ) 𝐼 𝐵 (𝑥 , 𝑦 )

∫𝑑𝑥𝑑𝑦 𝐼𝐵 (𝑥 , 𝑦 )

𝑃𝑠𝑤𝑒𝑒𝑝=∫𝑑𝑦𝑃 (𝑦 ) 𝐼𝐵 ( 𝑦 )

∫𝑑𝑦 𝐼 𝐵 ( 𝑦 )

jet target polarization is flat

vertical and horizontal Carbon targets available

For Gaussian profiles

Profile parameter