Single spin asymmetry measurement in t range 0'010'03 GeVc2 in ppelastic scattering at s200 GeV

1
Single spin asymmetry measurement in t range
0.01-0.03 (GeV/c)2 in pp-elastic scattering at
?s200 GeV

• I.G. Alekseev for pp2pp Collaboration

S. Bueltmann, I. H. Chiang, B. Chrien, A. Drees,
R. Gill, W. Guryn, D. Lynn, J. Landgraf, T.A.
Ljubicic, C. Pearson, P. Pile, A. Rusek, M.
Sakitt, S. Tepikian, K. Yip Brookhaven National
Laboratory, USA J. Chwastowski, B. Pawlik
Institute of Nuclear Physics, Cracow, Poland M.
Haguenauer Ecole Polytechnique/IN2P3-CNRS,
Palaiseau, France A. A. Bogdanov, S.B. Nurushev,
M.F Runtzo, M.N.Strikhanov Moscow Engineering
Physics Institute (MEPHI), Moscow, Russia I. G.
Alekseev, V. P. Kanavets, L.I. Koroleva, B. V.
Morozov, D. N. Svirida ITEP, Moscow,
Russia A.Khodinov, M. Rijssenbeek, L. Whithead,
S. Yeung SUNY Stony Brook, USA K. De, N. Guler,
J. Li, N. Ozturk University of Texas at
Arlington, USA A. Sandacz Institute for Nuclear
Studies, Warsaw, Poland spokesperson
SYMMETRIES AND SPIN, Prague, July 27 - August 3,
2005
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Helicity amplitudes for spin ½ ½ ? ½ ½

• Matrix elements
• Useful notations
• Formalism is well developed,
• however not much data ! At high energy only AN
  measured to some extent.

Observables cross sections
and spin asymmetries
spin nonflip double spin flip spin
nonflip double spin flip single spin flip
also ASS, ASL, ALL
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AN Coulomb nuclear interference

• The left right scattering asymmetry AN arises
  from the interference of
• the spin non-flip amplitude with the spin flip
  amplitude (Schwinger)
• In absence of hadronic spin flip
• Contributions AN is exactly calculable
• (Kopeliovich Lapidus)
• Hadronic spin- flip modifies the QED
• predictions. Hadronic spin-flip is
• usually parametrized as

µ(m-1)p µspptot
needed phenomenological input
stot, ?, d (diff. of Coulomb-hadronic
phases), also for nuclear targets em. and
had. formfactors
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AN measurements in the CNI region

pp Analyzing Power
pC Analyzing Power
E950_at_BNL p 21.7 GeV/c PRL89(02)052302
E704_at_FNAL p 200 GeV/c PRD48(93)3026
no hadronic spin-flip
with hadonic spin-flip
no hadronic spin-flip
Re r5 0.088 0.058 Im r5 -0.161 0.226
highly anti-correlated
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RHIC-Spin accelerator complex

RHIC pC CNI polarimeters

absolute pH polarimeter
BRAHMS PP2PP
RP3,4
PHOBOS
RHIC
RP1,2
PHENIX
Siberian Snakes
STAR
Siberian Snakes
Spin Rotators
5 Snake
Pol. Proton Source
LINAC
BOOSTER
AGS
200 MeV polarimeter
AGS quasi-elastic polarimeter
20 Snake
AGS pC CNI polarimeter
Rf Dipoles
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The setup of PP2PP
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Principle of the measurement

• Elastically scattered protons have very small
  scattering angle ?, hence beam transport magnets
  determine trajectory scattered protons
• The optimal position for the detectors is where
  scattered protons are well separated from beam
  protons
• Need Roman Pot to measure scattered protons close
  to the beam without breaking accelerator vacuum

Beam transport equations relate measured position
at the detector to scattering angle.
x0, y0 Position at Interaction Point Tx , Ty
Scattering Angle at IP xD, yD Position at
Detector TxD, TyD Angle at Detector
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Si detector package
Al strips 512 (Y), 768 (X), 50µm wide100 µm
pitch

• 4 planes of 400 µm Silicon microstrip detectors
• 4.5 x 7.5 cm2 sensitive area
• 8 mm trigger scintillator with two PMT readout
  behind Silicon planes.
• Run 2003 new Silicon manufactured by Hamamatsu
  Photonics.
• Only 6 dead strips per 14112 active strips.

implanted resistors
SVX chips
Trigger Scintillator
bias ring
guard ring
Detector board
Si
1st strip?edge 490 µm
LV regulation
Michael Rijssenbeek
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Hit selection

Landau fit
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Elastic events selection

• Only inner roman pots were used.
• OR of X and Y silicon pairs in each roman pot
  was used.
• A match of hit coordinates (x,y) from detectors
  on the opposite sides of the IP was required to
  be within 3? for x and y-coordinate.
• The hit coordinates (x,y) of the candidate proton
  pairs were also required to be in the acceptance
  area of the detector, determined by the aperture
  of the focusing quadrupoles located between IP
  and the RP's.
• If there were more than one match between the
  hits on opposite sides of the IP the following
  algorithm was applied if there is only one match
  with number of hits equal to 4, it is considered
  to be the "elastic event track". If there is no
  match with 4 hits or there are more than one such
  match, the event is rejected.
• Elastic events loss lt 3.5

Note the background appears enhanced because of
the saturation of the main band
Hit correlations before the cuts
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Elastic events

X
Y
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Calculation of asymmetry AN
Polarized crossection
Square root formula
where
Beam polarization (PBPY)/-- 0.880.12,
(PB - PY)-/- -0.050.05 Crosscheck ?N
(predicted)? (PB - PY)-/-AN ?-0.0011 ? ?N
(measured)-0.00160.0023
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Single spin asymmetry AN

Raw asymmetry ?N for 0.01lttlt0.03 (GeV/c)2
PRELIMINARY
Statistical errors only
Arm A Arm B
nucl-ex/0507030
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AN from PP2PP

No hadronic spin flip
Preliminary
Only statistical errors shown
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Fit r5

N. H. Buttimore et. al. Phys. Rev. D59, 114010
(1999)
where tc -8pa / stot

? is
anomalous magnetic moment of the proton
Re r5 -0.033 0.035 Im r5 -0.43 0.56
no hadronic spin flip
our fit
PRELIMINARY
Only statistical errors shown
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Effect of uncertainty of the beam polarization

? ? (pol.)
? ? (pol.)
PRELIMINARY
Re r5 -0.060.04 Im r5 -0.70 0.68
Re r5 -0.020.03 Im r5 -0.32 0.51
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Conclusions and plans

• Conclusions
• The first measurement of AN at collider energy
  vs200 GeV, small t
• AN is more than 10? different from 0
• AN systematically 1s above CNI curve with no
  hadronic spin-flip
• What is next ?
• Rotate RP1,3 (full acceptance over ? !) and move
  to STAR IP (spin rotators !!) ? (?tot, d?/dt, b,
  ?, AN , ANN , ASS , ALL , ALS)
• ?20m, pbeam100 GeV/c ? 0.003lttlt0.02(GeV/c)2
• ?10m, pbeam250 GeV/c ? 0.025lttlt0.12(GeV/c)2.

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Rotating RP1 and RP3
Full acceptance at ?s 200 GeV Without IPM and
kicker
With IPM and kicker