On Polarization of the Beam Extracted with the Bent Crystal

M. Ukhanov

IHEP Protvino

Kyoto 2-7 October 2006 M. Ukhanov IHEP Protvino 2

Outline

• Basics of the phenomenon

• Estimation of the effect

• Numerical example

Kyoto 2-7 October 2006 M. Ukhanov IHEP Protvino 3

Definition

P = 0A ≠ 0P ≠ 0

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Junior hunter exercise

P = 0A ≠ 0P ≠ 0

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Senior hunter exercise

P = 0A ≠ 0P ≠ 0

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Consequence from the definition

Beam,

extracted by means of the bent crystal,

must be polarized

by definition.

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Analyzing power at small |t|

hadflipnon

hadflip

hadflipnon

emflipN CCA *

2*

1

AN = AEM + AH

Kyoto 2-7 October 2006 M. Ukhanov IHEP Protvino 8

Analyzing power at small |t|

B.Z. Kopeliovich and T.L. Trueman, hep-ph/0012091

best fit withhadronic spin-flip

Kopeliovich –Truemann modelPRD64 (01) 034004hep-ph/0305085

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What we can expect

NH

NH

NH

NH

tAtA

tAtAP

))(1())(1(

))(1())(1(

Critical channeling angle in Si

θ = 5 μrad / p½(TeV/c)½

@ p = 70 GeV/c => θ ≈ 20 μrad

100 mrad bend gives N = 5000

If AH(t) = A0 |t/t0|½

for very small –t < t0 = 10-3 GeV2

and A0 = AH(10-3 GeV2) = 0.005Then P ≈ 0.8

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Dependence on the A0

AH(t) = A0 |t/t0|½

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Conclusions

• Bent crystal extraction provides polarization in the resulted beam.

• The beam polarization could be measurable

• or even big enough for practical needs.

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Analyzing power evolution at small t

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Independence on the channeling assumptions