04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Test of Small Angle Elastic Proton-Carbon Scattering as a High Energy Proton Beam

Polarimeter for RHIC

G. Bunce, H. Huang, Y. Makdisi, T. Roser, M. SyphersBrookhaven National Laboratory, Upton, NY 11973, USA

J. Doskow, K. Kwiatkowski, H.O. Meyer, B. v.Przewoski, T. Rinckel*

Indiana University Cyclotron Facility, Bloomington, IN 47405K. Imai

Kyoto University/ RIKENB. Bassalleck, L.L. Chavez, D.E. Fields*, K. Knight, R. Stotzer, T.L. Thomas, D. Wolfe

University of New Mexico* Co-spokesmen

Motivation Theory Measurements Experimental Apparatus Beam Time Request

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Motivation

RHIC schedule First Year running Oct.’99 - Aug. ‘00

Siberian Snakes installed Spin Rotators not installed yet Commissioning only, No Physics

Second Year running Oct. ‘00 - Aug. ‘01 Spin rotators installed Higher (Blue Book) Luminosity

Good Physics (G)

BUT: Need relative polarimeter for First Year commissioning !

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Motivation

Need fast relative and 5 % absolute polarimeter in RHIC Polarimeter options:

Inclusive Pion production (Analyzing power measured by E704) Polarimeter designed, but… Expensive and Complex May have smaller analyzing power due to Carbon target (vs.

Hydrogen used by E704)

Other polarimeters are complex: i.e. gas jet target, intense polarized electron beam, etc.

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Motivationp + C CNI polarimeter

Pros Inexpensive setup Solid target High figure of merit Little energy

dependence Pol. vs. y possible

ConsX Difficult Carbon recoil

detectionX Not absolute

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Theoryp+C Coulomb Nuclear Interference

CNI is an interference effect between the purely Coulombic spin-flip term and the hadronic non spin-flip term in the scattering potential

For the interference term to be important, the scattering must take place “outside of the nucleus (r>>R), but well within the screening radius of the atomic electrons (r<<ao)”

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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CNI analyzing power is given by:

so no direct energy dependence.

At small |-t| values, the Hadronic analyzing power goes as

At 200 MeV, Hadronic AN is large (~50%)

But, at 25 - 250 GeV, Hadronic AN ~ 0%

Theory

s

t

massproton : , 7928.1

8 with 02

020

p

totpN

mG

Zt

ttm

ttGtA

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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CNI Analyzing Power

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Measurements200-400 MeV p+12C elastic, Tamii et al.

AIP Conf. Proc. 339, page 395

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Measurements800 MeV p+p Pauletta et al.

Physical Review C27 (1983) 282-295.

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Measurementspp elastic at 200GeV/c (E704)

Physical Review D48 (1993) 3026-3036.

Curve has no hadronic spin flip

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Experimental Setup

Silicon array (4 - 3mm x 7mm, 12 cm from target)

Channel Plate detectorElectrostatic mirror

Target (6g/cm2 x 20m)

u,v Chambers

x,y Chambers

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Experimental SetupForward Proton Detector

Nuclear Physics A539 (1992) 633-661.

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Experimental SetupCarbon Recoil Detector

Silicon detectors

Nuclear Instruments and Methods 171 (1980) 71-74.

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Kinematics

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Kinematics

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Kinematics

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Kinematics

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Beam Time Request

Beam current = 200 A flux density = 1.8 1016 cm-2 s-1

luminosity = 2.6 x 1030 cm-2 s-1

cross section = 15 mb/sr at p=20 deg - 400 mb/sr at 6 deg

count rate for each of the 8 angle bins is then 4.5 kHz adjust luminosity to 3.5 x 1028 cm-2 s-1 the data rate at the largest angle of interest is 10 Hz statistical accuracy of better than 1% can be carried out in about one

hour

From the above, we conclude that the time for actual data taking under

various conditions will be of the order of 5-6 shifts.

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Recoil Rates and Time RequestRecoilAngle[deg]

RecoilEnergy[keV]

RecoilTOF[ns]

ForwardAngle[deg]

Forw.SolidAngle[msr]

CrossSection[mb/sr]

Rate

[Hz]87.6 110 93 4.4 0.20 400 2.8

86.0 300 57 7.3 0.33 350 4.1

84.4 585 41 10.2 0.46 270 4.3

82.8 960 32 13.1 0.59 130 2.7

Luminosity: 3.5 x 1028 cm-2 s-1 to keep p detector rate < 500 HzA=1% per C detector requires about one hour run.We will need about 5-6 shifts for data taking under various conditions

04/19/23 Douglas E. Fields for the p+C CNI collaboration

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Beam Time Request

200 MeV 450 MeVL 3.5 x 1028 cm-2 s-1 (Rate <500Hz in p)

Rec> 87.6o 86o 84.4o 82.8o 87.6o 86o 84.4o 82.8o

Rec 1.72o 1.71o 1.71o 1.70o 1.72o 1.71o 1.71o 1.70o

<ERec> 110 keV 300 keV 585 keV 960 keV

TOFRec93 ns 57 ns 41 ns 32 ns

p

4.4o 7.3o 10.2o 13.1o

d/dp 400 mb 350 mb 270 mb 130 mb

p 0.20 msr 0.33 msr 0.46 msr 0.59 msr

RateRec 2.8 4.1 4.3 2.7

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Beam Time Request

5 shifts beam preparation, electronics adjustments, target manipulation, general overhead

6 shifts data acquisition at 200 MeV6 shifts data acquisition at 450 MeV

Total = 17 shifts