Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Preliminary Result of A N Measurement in p  p  Elastic Scattering at RHIC, at  s = 200 GeV Włodek Guryn for pp2pp collaboration Brookhaven National Laboratory, Upton, NY, USA OUTLINE of the TALK Description of the experiment Description of analysis Results and interpretation Where do we go from here?

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Total and Differential Cross Sections, and Polarization Effects in pp Elastic Scattering at RHIC S. Bültmann, I. H. Chiang, R.E. Chrien, A. Drees, R. Gill, W. Guryn*, J. Landgraf, T.A. Ljubičič, D. Lynn, 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 S. Khodinov, M. Rijssenbeek, L. Whitehead SUNY Stony Brook, USA K. De, N. Ozturk University of Texas at Arlington, USA A. Sandacz Institute for Nuclear Studies, Warsaw, Poland * spokesman

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Spin Dependence in Elastic Scattering Five helicity amplitudes describe proton-proton elastic scattering Some of the measured quantities are σ tot of gives s dependence of   Contributes to the shape of A N

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Source of single spin analyzing power A N Single spin asymmetry A N arises in the CNI region is due to the interference of hadronic non-flip amplitude with electromagnetic spin-flip amplitude (originally called Schwinger asymmetry) Any difference from the above is an indication if other contributions, hadronic spin flip caused by resonance (Reggeon) or vacuum exchange (Pomeron) contributions.

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration The world data on A N (pp) FNAL E704  s  20 GeV N. Akchurin et al. PRD 48, 3026 (1993) Preliminary 2002 A N = ± CNI curve N.H. Buttimore et al. PRD 59, (1999)

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration RHIC/AGS Measurements E950 elastic pC J. Tojo et al. PRL 89, (2002) There will also be results from polarized jet at RHIC

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Experimental Determination of A N Use Square-Root-Formula to calculate spin ( ,  ) and false asymmetries ( , .) This formula cancels luminosity dependence and apparatus asymmetries. Since A N is a relative measurement the efficiencies  (t,  ) cancel

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Principle of the Measurement Elastically scattered protons have very small scattering angle θ *, 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. x 0,y 0 : Position at Interaction Point Θ* x Θ* y : Scattering Angle at IP x D, y D : Position at Detector Θ x D, Θ y D : Angle at Detector =

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration The Setup

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Elastic Event Identification An elastic event has two collinear protons, one on each side of IP 1.It also has eight Si detector “hits”, four on each side. 2.Clean trigger: no hits in the other arm and in inelastic counters. 3.The vertex in (z 0 ) can be reconstructed using ToF.

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Trigger Active area Acceptance beam pipe shadow Only “inner” pots used for trigger and analysis, biggest acceptance Analyze the data for the closest position (¾ of all data)

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Angle (hit) Correlations Before the Cuts Events with only eight hits Note: the background appears enhanced because of the “saturation” of the main band

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Hit selection 1.Pedestal value, pedestal width (  and dead channels (only six) were determined; 2.Valid hit, single strip, has dE/dx > 5  above the pedestal; 3.Cluster size is  5 consecutive strips above pedestal cut; 4.Valid hit in the Si plane for event reconstruction: is a cluster whose dE/dx > 20 ADC counts above pedestal and is within fiducial area of the detector (slide); has for a y-plane y > 0.2mm from the edge of the detector. 5.Coordinate for x and y formed from adjacent hits in Sin for each Roman Pot

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Elastic Events Display Dave Morse

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Elastic Event Selection I Up Down Corerlations Use the correlation between coordinates from two opposite RPs (RP1U – RP3D) or (RP1D – RP3U) to define candidate tracks. Use natural widths of the distributions -  (x1-x2) vs (x1+x2) cm

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Elastic Event Selection III After finding matching hits in x and y: Choose events with one track in x and one track in y and  6hits. Veto on the Sc signal in the opposite arm, TDC cut. Choose collinear tracks within 3  in angles. Plot dN/dt and calculate asymmetries.

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Calculation of Scattering Angle 1.Using matched hits scattering angels can be calculated. 2.Use transport and and average (x 0, y 0 ) and beam angles obtained from vectors reconstructed using all eight RPs. 3.Make z-vertex correction using ToF. Before ToFAfter ToF

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Collinearity:  x before and after z-correction, and  y  x ) = 130  rad  x ) = 100  rad  y ) = 70  rad

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Event Yields after Cuts DESCRIPTION# Events All Events3,699k Elastic trigger Events with hits in Si fid. area (  6 hits/event) 3,598k 1,816k Candidate elastic events (at least one track using x,y correlations) Arm A + B1,295k Collinear elastic events: 3  cut in (  x,  y ) one track in Arm A+B only Elastic events used for spin analysis, t-cut 1,254k 1,218k Candidate elastic events arm A716k Candidate elastic events arm B579k Collinear events: 3  cut in (  x,  y ) arm A 696k Collinear events: 3  cut in (  x,  y ) arm B 558k

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration dN/dt Useful t-interval [0.011,0.029] (Gev/c) 2

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration  angle distributions for spin combinations

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Determination of A N Use Square-Root-Formula to calculate raw asymmetries. 1.It cancels cancel luminosity dependence and effects of apparatus asymmetries. 2.It uses ,  bunch combinations. Whereis very small Since A N is a relative measurement the efficiencies  (t,  ) cancel

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Preliminary Results: Full bin < -t < (GeV/c) 2 Fit A N cos(  ) dependence to obtain A N Arm A Arm B A N (  PRELIMINARY  [deg]

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Results: P Yellow + P Blue = 0.67 (central value) and CNI curve (  tot,  from world data, B from pp2pp result) Note: a) P Yellow + P Blue = 0.67 can vary by ± 15% ( a working number); b) Systematic effects due to the beam transport uncertainty are small compared to the beam polarization uncertainty. Preliminary One point for full t-interval [0.011,0.029]Two points for two half intervals PRELIMINARY

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Results: comparison with CNI different polarizations and CNI parameters Curves show dependence of CNI on  tot,  and B PRELIMINARY

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Prediction using E704 and E950 data Larry Trueman The upper curve has Regge contribution and the Pomeron coupling set to zero. Here  = i. Not much change in the curve. Note that the f/a2 is the dominant Regge contribution and this leads to a very large energy dependence, especially to Re(  ), in going from 704 energy to RHIC energy. At s = 400 GeV 2,  = i LT: The predictions are very uncertain because E704 makes a very large contribution with large errors to the Regge parameters. Preliminary

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Theoretical Interpretation: Boris Kopeliovich Assume the non-flip Re   / Im   =  /2*  =0.15, where  ~ 0.1, is the power of s in energy dependence of  tot  1) The dashed curve is calculation with central values for r 5 as was published by E950. Need for energy dependence of r 5 2) The dash-dotted uses Im r 5 =  0.12, from  p and pp data at low energies. (BK SPIN2002 and hep-ph/ ) The phase is assumed to be the same as for the non-flip amplitude, i.e. Re r 5 /Im r 5 = ) Solid curve assumes r 5 rising as s , Regge Model of  tot i.e. the spin-flip amplitude rises as s 2  and results in: a) Im r 5 =  0.24 ( twice that at low energy.) b) Re r 5 =  /2*2  *Im r 5 =  Kopeliovich - Povh prediction Mod.Phys.Lett. A13: ,1998 CNI This Exp. Preliminary Preliminary

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Summary 1.We have measured the single spin analyzing power A N in polarized pp elastic scattering at  s = 200 GeV, highest to date, in t-range [0.011,0.29] (GeV/c) 2. 2.The A N is  4-5  from zero (statistical error.) 3.The A N is  2  away from a CNI curve, which does not have hadronic spin flip amplitude. 4.We discussed interpretation of the result by Larry Trueman and Boris Kopeliovich. (there is clear  s dependence in r 5, a hadronic spin flip is present.) 5.In order to understand better underlying dynamics one needs to map  s and t- dependence of A N and also measure other spin related variables A NN …. RHIC is a great and unique place to do this physics and we have a plan how to do it and do it better!

Preliminary A N pp2pp September 2004 Włodek Guryn for pp2pp collaboration Future Possibility – Big Improvement  s (GeV) ** |t|-range (Gev/c) 2 Typical errors m0.003 < |t| < 0.02  B = 0.3,  tot = 2 – 3 mb  = and  A N =0.002 x-y Full acceptance at  s 200 GeV Without IPM and kicker With IPM and kicker dN/dt