First Result from the pp2pp Experiment Włodek Guryn for pp2pp collaboration Brookhaven National Laboratory, Upton, NY, USA Introduction – pp2pp physics program; Description of the experiment; Engineering run in 2002; Data analysis and results; Summary and outlook.

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 2 Total and Differential Cross Sections, and Polarization Effects in pp Elastic Scattering at RHIC S. Bueltmann, B. Chrien, A. Drees, R. Gill, W. Guryn*, I. H. Chiang, D. Lynn, C. Pearson, 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, 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 M. Rijssenbeek, C. Tang, 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 * spokesman

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 3 Polarized Proton Collisions in RHIC

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 4 RHIC has the UNIQUE capability for colliding POLARIZED proton beams, further elucidating the exchange dynamics: – Beam energy between 25 and 250 GeV; – Transverse polarization up to 70%; – Polarization can be chosen on a bunch-by-bunch basis (good for eliminating detection systematics!); Allows to measure spin dependence of proton-proton elastic scattering CNI region : < -t < 0.02 (GeV/c) 2 √s = 200 GeV < -t < 0.13 (GeV/c) 2 √s = 500 GeV  tot, , B, d  /dt, A N (t), A NN (t)   ot = 600  barn (~1%),  = (4%),  A N (t),  A NN (t) = Medium |t| region: 0.02 < -t < 1.3 (GeV/c)2 √s = 500 GeV diffractive minimum (peaks and bumps) and their spin dependence PP2PP Physics program Design parameters

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 5 pp2pp experiment studies the dynamics and spin dependence of hadronic interaction through proton-proton elastic scattering P, O Vacuum QM exchanged p pp pp pp p Pomeron (C=+1) Odderon (C=  1) + Perturbative QCD Picture s = (p 1 + p 2 ) 2 = (C.M energy) 2 t = (p 1 – p 3 ) 2 = - (four momentum transfer) 2 s    t  1 (GeV/c) 2 – Non-perturbative regime Elastic scattering d  /dt + optical theorem  total cross section  tot

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 6 M PP2PP Highest energy so far: pp: 63 GeV (ISR) pp: 1.8 TeV (Tevatron) pp2pp energy range: 50 GeV   s  500 GeV pp2pp t-range: (at  s = 500 GeV) 410 –4 GeV 2  |t |  1.3 GeV 2 Summary of Existing Data

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 7 Principle of 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 beam without breaking accelerator vacuum Beam transport equations relate measured position at detector to scattering angle x = a 11 x 0 + L eff θ x  Optimize so that a 11 small and L eff large θ x = a 12 x 0 + a 22 θ x  x 0 can be eliminated by measuring θ x * x : Position at Detector θ x : Angle at Detector x 0 : Position at Interaction Point θ x : Scattering Angle at IP * Similar equations for y-coordinate We found that because of the roll, misalignment, of the quadrupoles there is a mixing between x and y.

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 8 pp2pp Experimental Setup in Engineering run 2002 Elastic and Inelastic Detectors

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 9 Running Conditions in 2002 Running conditions during a pp2pp, 14 hour dedicated run: Beam momentum p = 100 GeV/c Number of bunches per beam N B = 55 used 35 bunches Beam scraped to emittance ε  12 π m and intensity I  protons in each beam Beam optics used β* = 10 m Beam polarization (working #) P b = 0.24  0.02 Closest approach of first detector strip to beam about 15 mm  15  beam  t min = GeV 2 Collected ~1 million triggers of which >30 % are elastic events

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 10 Data Analysis: Colinearity Correlation plots of x- and y-coordinates using elastic triggers with reconstructed tracks of scattered protons

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 11 Beam Angular Divergence Good agreement between width of θ x and θ y distributions for measured and simulated events with emittance of: ε = 12 π m And vertex size:  z = 70 cm Δθ x  150 μrad Δθ y  70 μrad N. Öztürk Δθ y Δθ x N. Öztürk

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 12 Event Reconstruction Elastic event: good track in two “opposite” set of detectors SSD coordinate was calculated using energy weighted average of the position of the strips belonging to the isolated cluster of no more than three hits; Correlation between tracks in two Roman Pots: require that (  x 2 +  y 2 ) be within “radius” : (  x 2 +  y 2 ) < 16 (  x 2 +  y 2 ); At least six out of eight hits belong to the track; No more than two planes with hits in “non” elastic arm; Select events within uniform t-acceptance t  cut 

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 13 |t |-  -Acceptance Find region in |t |- and  -space with full acceptance coverage and high statistics t = - ( p beam θ ) 2  = azimuthal angle Event Sample 196,000 events: 159,250 events ( 0 <  < 180º ) 122,437 events ( 45º <  < 135º ) 58,511 events ( 45º <  < 135º ) & GeV 2  |t |  GeV 2 )

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 14 Extracting B from dN/dt-Distribution dd dt =  G E     t2t2    tot 2 e +Bt   G E   tot e +½Bt t + + [ ] C Fit |t |-distribution with fixing  tot  51.6 mb and  0.13 and keeping B as a free parameter in range GeV 2  |t |  GeV 2  results in B = ( 16.3  1.6 ) GeV -2 Depends on detector position Depends on beam transport element positions B = ( 16.3  1.6 ) GeV -2

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 15 Systematic and Correlation Errors Systematic Errors were evaluated using Monte Carlo simulations: 1.Beam emmitence; 2.Vertex position spread in x, y, z; 3.Incoming beam angels – major source; 4.Beam transport uncertainty; Total Systematic Error  0.9 (GeV/c) -2 Correlation between fitted parameter B and values of   and  :    ±4 mb =>  –/ (GeV/c) -2  ±  0.02 =>  ±  0.32 (GeV/c) -2

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 16 RESULT b = 16.3 ± 1.6 (stat.) ± 0.9 (syst.) (GeV/c) -2 Analysis done by two independent groups is in agreement. E710: 0.02<-t<0.08 CDF: <-t < 0.08 UA4: <-t < 0.12

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 17 Donnachie&Landshoff OPE Model Bourrely, Soffer, Wu

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 18 Single spin asymmetry A N arises in CNI region mainly from interference of hadronic non-flip amplitude with electromagnetic spin-flip amplitude A N (t ) = N  (t) + N  (t) - N  (t) - N  (t) 1 P beam cos  N  (t) + N  (t) + N  (t) + N  (t)  Im [ Φ 5 * Φ + ] dσ / dt for small t Preliminary Fit  N / cos  = ± Preliminary A N = ± 0.018

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 19 Running Conditions Systematic error improvement in 2003 due to:  Excellent silicon detector efficiency;  Measurement of local angles with new Roman Pot stations;  Improved beam optics measurement;  Van der Meer beam scans for luminosity measurement. Systematic error improvement in 2003 due to:  Excellent silicon detector efficiency;  Measurement of local angles with new Roman Pot stations;  Improved beam optics measurement;  Van der Meer beam scans for luminosity measurement.

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 20 Conclusions and Plans Conclusions  A promising physics result for b and A N from engineering run 2002  Excellent silicon detector performance in physics run 2003  Good statistics obtained - waiting for physics results. New proposal for 2004 and beyond ( to be considered by PAC Sept 29, 2003 )  Run with current setup (  tot, d  /dt, b, , A N, A NN )  * =20 m, p beam =100 GeV/c  0.003<|t|<0.02(GeV/c) 2 ;  * =10 m, p beam =250 GeV/c  0.025<|t|<0.12(GeV/c) 2.  Put Roman Pots between DX and D0 magnets (d  /dt, b, A N, A NN )  * =3m, p beam = 250 [100] GeV/c  0.2<|t|<1.3(GeV/c) 2 [0.02<|t|<0.12(GeV/c) 2.]  Upgrade RHIC quadrupoles power supply at our IP to run with  * =100m and move Roman Pots to 70m position (  tot, d  /dt, b, , A N, A NN )  * =100m, p beam =100 and 250 GeV/c  |t| CNI region

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 21 Spin Physics with pp2pp Five helicity amplitudes describe proton-proton elastic scattering Φ 1 (s,t )  Φ 2 (s,t )  Φ 3 (s,t )  Φ 4 (s,t )  Φ 5 (s,t )  σ tot = Im [ Φ + (s,t ) ] t=0 8 π s Measure: Φ n (s,t )  with h x = s-channel helicity p 1 = -p 2 incoming protons p 3 = -p 4 scattered protons Φ + (s,t ) = ½ ( Φ 1 (s,t ) + Φ 3 (s,t ) ) dσdσ dtdt = ( |Φ 1 | 2 + |Φ 2 | 2 + |Φ 3 | 2 + |Φ 4 | 2 | + 4|Φ 5 | 2 ) 2 π s 2 Δσ T = - Im [ Φ 2 (s,t ) ] t=0 = σ  - σ  8 π s Δσ L = Im [ Φ 1 (s,t ) - Φ 3 (s,t ) ] t=0 = σ  - σ  8 π s  

Small x and Diffraction Sept , 2003 FNAL Włodek Guryn 22 = Actual transport: (x 0, y 0 ) not known also coupled because of the quad roll YellowBlue