Experiment pp2pp at RHIC

1
Experiment pp2pp at RHIC

• V.P. Kanavets for pp2pp Collaboration

• S. Bueltmann, B. Chrien, A. Drees, R. Gill, W.
  Guryn, I. H. Chiang, D. Lynn,
• P. Pile, A. Rusek, M. Sakitt, S. Tepikian
  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 Moscow
  Engineering Physics Institute (MEPHI), Moscow,
  Russia
• I. G. Alekseev, V. P. Kanavets, B. V. Morozov,
  D. N. Svirida ITEP, Moscow, Russia
• M. Rijssenbeek, C. Tang, P. Yaron, S. Yeung
  SUNY Stony Brook, USA
• K. De, N. Guler, J. Li University of Texas at
  Arlington, USA
• Sandacz Institute for Nuclear Studies, Warsaw,
  Poland
• spokesperson

2
Main goal

• Main goal of the pp2pp
• measurement of pp elastic scattering in collider
  regime with UNIQUE capability due to polarized
  proton beams.
• Kinematical range
• almost unexplored,wide
• 50 ltÖ-s lt500 GeV
• 4 x 10-4lttlt1.3 GeV2

3
Outline

• ? pp2pp Collaboration
• ? Kinematics, amplitudes
• ? Physics of pp elastic scattering
• ?general
• ?spin physics
• ? pp2pp detectors
• ? First (engineering) run
• ? Some results
• ? Future
• ? Summary

4
Kinematics

• P1 P2 P3 P4
• At the interaction point (IP)
• P1 ?P2 ? P3 ?P4 ? P collinearity
• ?P1? ?P2? ?P3? ?P4? Pbeam
• s (P1 P2)2 (2Ebeam)2
• t (P1 ? P3)2 ?4 P2beam ? sin2 ?/2 ? For small
  angles t ?(Pbeam? ?)2
• Helicity amplitudes
• ? ? ?h3h4 ?M(s,t)? h1h2 ? ,
• hi ? s- channel helicity of proton i
• ?1 ? ? ?? ??? ?? ? no helicity flip
• ?2 ? ? ?? ??? ?? ? double helicity flip
• ?3 ? ? ?? ??? ?? ? no helicity flip
• ?4 ? ? ?? ??? ?? ? double helicity flip
• ?5 ? ? ?? ??? ?? ? single helicity flip
• Frequently used
• ?? (?1 ? ?2)?2, ?? (?1 ? ?2)?2

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Physics of pp2pp

• ?t ?? 10?3 GeV2 ? Coulomb region
• predictable ?direct measurement of LUMINOSITY
• t ? range
• 10?? ? ?t? ? 1.3
  GeV2 ?Medium ?t? nuclear region
• including
  Coulomb-Nuclear Interference region
• (6 ? 0.15) fermi
• ?
• SCATTERING PROBES CONSTITUENT STRUCTURE OF PROTON
  AND ITS STATIC PROPERTIES
• ?
• long range nonpeturbative QCD
• ?
• Regge phenomenology ? QCD inspired models with
  POMERON
• ( and ODDERON ) exchange.
• AT HIGH ENERGIES THE DOMINANT MEDIATOR OF SMALL
  ?t? SCATTERING is POMERON.

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Physics of pp2pp (cont.)

• POMERON ? SINGULARITY in COMPLEX ANGULAR MOMENTUM
  PLANE with
• trajectory a(t) (1 ? D?? 0.25 t (D ?0? small)
• isospin T 0
• charge conjugation C 1
• Hypothetic ODDERON ? the same, but C ??, (D ?
  0, small).
• ?
• DISTINCTION between amplitudes of pp and pp
  scattering because of the different sign of
  ODDERON contribution.
• Description of pp DIFFERENTIAL CROSS SECTION AT
  Ö-s 53 Gev by interference of single Pomeron,
  double Pomeron and three gluon exchanges.

A.Donnachie, P.V.Landshoff, NP D231 (1984) 189
7
Nature of Pomeron

• Constituent structure of Pomeron is not
  understood well up to now. For example
• in Lipatov model Pomeron is t channel exchange
  by two reggedized gluons in C 1 colorless
  state and ODDERON is exchange by three reggedized
  gluons in C1 colorless state.
• ?
• Equal foundation for Pomeron and Odderon.
• Universal Pomeron model by J.Soffer et al.
  predicts for pp and pp scattering the same
  sc/(lns)c
• total cross section behavior from high energy
  relativistic quantum field theory and Froissart
  Martin bound ?tot?const?(lns)2. From pp data
  c0.167, c 0.748

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pp2pp experimental capabilities

• Scattering with unpolarized protons
• total cross section ?tot(s), diffraction cone
  slope parameter b(s,t), and r(s) ?Re
  A(s)/ImA(s)?t0 parameter will be extracted from
  d?/dt in Coulomb Nuclear Interference (CNI) and
  nuclear regions.
• PHYSICAL TESTS
• Pomeranchuk theorem
• ?pptot ? ?pptot ? 0 at s? ?
• Presence of odderon
• rpp ? rpp ? 0 at s? ?
• contribution of three gluon exchange with C 1
  in dip region (from comparison with pp data).

9
Spin Physics

• In general spin is sensitive to the mechanism of
  exchange.
• CNI REGION, -t (0.001 0.01) GeV2 ? SINGLE
  SPIN ASYMMETRY EXPECTATION
• leading term of small t AN?d?/dt?2Im ??5
• Interference of hadronic non-flip amplitude with
  electromagnetic spin-flip amplitude produces
  asymmetry (4 5)? in the maximum at ?t?
  0.003 GeV2. This yield to AN is calculable.
• ?
• Base for RHIC polarimetry

FNAL E704 data (1993)
N.H. Buttimore, B.Z. Kopeliovich, E. Leader, J.
Soffer, T.L. Trueman, The Spin Dependence of
High-Energy Proton Scattering, PR D59 114010
(1999)
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Spin Physics (cont.)

• SEARCH for spin-flip of Pomeron.
• AN in CNI region is sensitive to hadronic
  spin-flip amplitude due to its interference with
  non-flip electromagnetic amplitude. This term
  (including its phase) may be extracted from
  measured AN (t).
• hadronic spin-flip amplitude accounts for s
  channel helicity noncoservation at high energies.
  helicity-flip term of Pomeron can indicate
• isoscalar anomalous magnetic moment of nucleon
• helicity nonconservation in constituent quark
  gluon vertex
• compact quark pair in proton (diquark quark
  structure).

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Spin physics (cont.)

• DOUBLE TRANSVERSE SPIN ASYMMETRY
• Leading term at small t ANN?d?/dt?2Re ??2
• SEARCH for Odderon.
• ?
• Different (??/2) phases of Pomeron and Odderon
  at t0
• ?
• Enhancement of Odderon contribution to ANN due to
  interference with electromagnetic amplitude
• ?
• Characteristic peak near ?t? 0.002 GeV2.

E.Leader, T.L.Trueman The Odderon and spin
dependence of high-energy proton-proton
scattering, PR D61, 077504 (2000)
f2/f0.05(1i)
f2/f0.05
f2/f0.05i
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TOTAL CROSS SECTION DIFFERENCE

• for transverse polarization ??T (s) ?tot ????
  ? ?tot ????.
• MEDIUM 0.1 ? ?t? ? 1.3 GeV2 REGION
• ?
• Study dynamics of diffractive pp scattering
• Single spin asymmetry AN especially interesting
  in dip region
• From previous measurements
• appearence of negative AN asymmetry near t 1
  GeV2 at Ö-s ?10 GeV
• slow variation in 10 ? Ö-s ? 24 GeV range
• Double spin asymmetry ANN
• ?
• Measurement of differences between spin parallel
  and antiparallel crossections in the whole
  region.
• LARGE ?t? ? 3 GeV2 REGION
• ?
• Test pQCD
• Two gluon (hard Pomeron) and three gluons
  (Odderon) exchanges with point-like quark-gluon
  interaction.
• Small d?/dt with t-8 dependence.

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The RHIC Spin complex
e 5 ? mm mrad with scraping
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Experimental Setup

• MAIN IDEA
• In colliding beam mode scattered proton follow
  trajectories determined by LATTICE of the
  collider because it has the same momentum as a
  beam proton and scattering angle is small.
• The coordinates of scattered particles at the
  detector position with respect to the reference
  orbit are given by TRANSPORT EQUATION
• Y ? a11 y?? Leff ??y
• y? is position of interaction vertex,
• ??y is scattering angle
• OPTIMUM CONDITION for scattering angle
  measurement is INDEPENDENCE on vertex position
• ?
• a11 ? ?, Leff large ? y ? Leff ??y
• ? PARALLEL to POINT FOCUSING
• ?
• The location of detectors was chosen from this
  requirement.

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Experimental Setup (cont.)

• ACCEPTANCE is determined by the beam pipe size
  for large ?t? and there ia a ?tmin? cutoff for
  small ?t?due to the beam emittance. The distance
  from the beam to the detector device bottom has
  to be larger than 15 ?y at the detector position
  to exclude intercepting the outer edge of beam.
• BASIC ELEMENTS
• Silicon strip detectors inside Roman pots (RP),
  located downstream from IP. RP allow insertion
  (with vacuum bellows) of the detectors inside
  beam pipe.
• Set of veto counters around IP to reject
  inelastic diffractive background.

Layout of the pp2pp experiment
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Roman pot station

• Each Roman Pot station
• Contains two Roman Pots with detector packages
• Precision motion with CNC Linear Slide

Stepping Motor
Linear Slide
Vacuum
Bellows
UHVChamber
Silicon Strip
Detectors
Pot
SVX Readout
Electronics
Michael Rijssenbeek
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Roman Pot Design

• Roman Pot (UTA-BNL)
• Thinnest possible bottom (minimize d0) to
  closely approach the beam
• Thin beam windows reduce interactions and beam
  blow-up

LV regulation
PMTs
Trigger Counters
Silicon Detectors
Michael Rijssenbeek
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Si Detector Package
Al strips 512 (Y), 768 (X), 70µm wide100 µm
pitch

• 4 planes of 400 µm Silicon microstrip detectors
  (BNL Instrum. Div.)
• 4.5 x 7.5 cm2 sensitive area
• good resolution, low occupancy
• Redundancy 2X- and 2Y-detectors
• Closest proximity to the beam 14 mm
• 8 mm trigger scintillator with two PMT readout
  behind Silicon planes

implanted resistors
bias ring
Trigger Scintillator
guard ring
Si
Detector board
1st strip?edge 490 µm
LV regulation
Michael Rijssenbeek
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Elastic detectors

• Each Roman pot contains 4 silicon microstrip
  detectors (2 x-view and 2 y-view to provide
  redundancy) and 8 mm thick trigger scintillator
  with 2 PMTs readout
• Microstrip detector
• Single sided
• 2 versions x-view and y-view
• DATA ACQUISITION SYSTEM
• SVX-IIE chips (designed by D0 Collaboration)
• 128 input channels per chip
• Preamplifier, analog pipeline, Wilkenson type ADC
  per channel
• Sparse data option ? output data only for
  channels which ADC values are above threshold and
  their neighbors ? trigger rate upto several kHz

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The first (engineering) run. 24-Jan-02

• ACCELERATOR PARAMETERS
• Pbeam 100 GeV/c
• Revolution rate 78.25 kHz
• Number of bunches 55
• Total intensity (each beam) 5?1011
• Emittance after scraping 10? mm?mrad
• Polarization (each beam, vertical ) (20-25)
• Bunch-bunch crossing with polarization
  combinations (??), (??), (??) and (??) ?
  excellent beam quality
• EXPERIMENTAL CONDITIONS
• 1 Roman pot station (top and bottom pots) at 57 m
  from IP in each arm
• Inelastic veto around IP (to tag inelastic
  events)
• ? (in IP) 10 m, Leff(ver) 23 m, Leff(hor)
  7 m
• Kinematic range Ö-s 200 GeV, 0.004 lt t lt
  0.02 GeV2
• Data taking 14 hours ? Collected 974 k triggers
  (60 elastic)

21
Data analysis

• MAIN GOALS
• Determination of differential crossection as a
  function of t and extraction of nuclear slope
  parameter
• Estimation of the average transverse single-spin
  asymmetry for the covered kinematical range
• SELECTION OF ELASTIC EVENTS, BACKGROUND
  DETERMINATION
• Selection of elastic events from x-,
  y-correlation plots
• Optimization of hit recognition
• Determination of Si detectors efficiency
• Background determination
• ACCEPTANCE CALCULATION
• From data fiducial region with high acceptance
• From MC simulation

22
Some results

• Efficiency of elastic event identification gt 99
• Background under the elastic peak lt 2
• The error bars in the measured angles are defined
  mainly by the beam parameters at the IP
• sector 1 top sector 2 bottom
• x-correlation y-correlation xtop xbottom

23
Conclusions and Summary

• Conclusions
• Good performance of the Si detectors and other
  apparatus
• Beautiful separation of elastic events
• High quality data
• Summary
• The first experiment on high energy polarized
  proton elastic scattering starts
• First run successful
• Expect physics results this summer
• Exciting opportunities of pp2pp in the next few
  years

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Long term plan

• 2003
• Finish building of the experiment 4 more Roman
  pot stations
• Extend measurements to 0.1 lt t lt 1.3 GeV2
• High statistical run
• 2004 and beyond
• Measure in CNI region, requiring special RHIC
  tune,
• 0.0004 lt t 0.12 GeV2
• Measure in large t region 1.3 lt t lt 5 GeV2
• Elastic scattering of pd, dd, p?