Post on 31-Dec-2015
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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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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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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