1. PAX experiment PAX: Polarized Antiproton Experiments 1 dr. Paolo Lenisa Università di Ferrara and INFN - ITALY ECT – Workshop: Hadronic structure of the nucleon Trento, May 9-13 http://www.fz-juelich.de/ikp/pax

2. PAX experiment PAX: Polarized Antiproton Experiments 2 Yerevan Physics Institute, Yerevan, Armenia Department of Subatomic and Radiation Physics, University of Gent, Belgium University of Science & Technology of China, Beijing, P.R. China Department of Physics, Beijing, P.R. China Palaiseau, Ecole Polytechnique Centre de Physique Theorique, France High Energy Physics Institute, Tbilisi State University, Tbilisi, Georgia Nuclear Physics Department, Tbilisi State University, Georgia Forschungszentrum Jülich, Institut für Kernphysik Jülich, Germany Institut für Theoretische Physik II, Ruhr Universität Bochum, Germany Helmholtz-Institut für Strahlen- und Kernphysik, Bonn, Germany Physikalisches Institut, Universität Erlangen-Nürnberg, Germany Langenbernsodorf, UGS, Gelinde Schulteis and Partner GbR, Germany Department of Mathematics, University of Dublin,Dublin, Ireland Università del Piemonte Orientale and INFN, Alessandria, Italy Dipartimento di Fisica dell’Università and INFN, Cagliari, Italy Università dell’Insubria and INFN, Como, Italy Instituto Nationale di Fisica Nuclelare, Ferrara, Italy PAX Collaboration Spokespersons: Paolo Lenisa Paolo Lenisalenisa@mail.desy.de Frank Rathmann Frank Rathmann f.rathmann@fz-juelich.de

3. PAX experiment PAX: Polarized Antiproton Experiments 3 Dipartimento di Fisica Teorica, Universita di Torino and INFN, Torino, Italy Instituto Nationale di Fisica Nucleare, Frascati, Italy Andrej Sultan Institute for Nuclear Studies, Dep. of Nuclear Reactions, Warsaw, Poland Petersburg Nuclear Physics Institute, Gatchina, Russia Institute for Theoretical and Experimental Physics, Moscow, Russia Lebedev Physical Institute, Moscow, Russia Physics Department, Moscow Engineering Physics Institute, Moscow, Russia Laboratory of Theoretical Physics, Joint Institute for Nueclear Research, Dubna, Russia Laboratory of Particle Physics, Joint Institute for Nuclear Research, Dubna, Russia Laboratory of Nuclear Problems, Joint Institute for Nuclear Research, Dubna, Russia Budker Institute of Nuclear Physics, Novosibirsk, Russia High Energy Physics Institute, Protvino, Russia Institute of Experimental Physics, Slovak Academy of Science, Kosice Slovakia Department of Radiation Sciences, Nuclear Physics Division, Uppsala University, Uppsala, Sweden Collider Accelerator Department, Brookhaven National Laboratory, Broohhaven USA RIKEN BNL Research Center Brookhaven National Laboratory, Brookhaven, USA University of Wisconsin, Madison, USA Department of Physics, University of Virginia, USA 178 physicists 35 institutions (15 EU, 20 NON-EU) PAX Collaboration

4. PAX experiment PAX: Polarized Antiproton Experiments 4 The PAX proposal Jan. 04 LOI submitted 15.06.04QCD PAC meeting at GSI 18-19.08.04Workshop on polarized antiprotons at GSI 15.09.04 F. Rathmann et al., A Method to polarize stored antiprotons to a high degree (Phys. Rev. Lett. 94, 014801 (2005)) 15.01.05 Technical Report submitted 14-16.03.05QCD-PAC meeting at GSI Polarization enters in the core of FAIR

5. PAX experiment 5 Outline WHY? Physics Case HOW? Polarized Antiprotons WHAT?Staging Detector and signal estimate WHERE AND WHEN? The FAIR project at GSI PAX: Polarized Antiproton Experiments

6. PAX experiment 6 Physic Topics Transversity Electromagnetic Form Factors Hard Scattering Effects SSA in DY, origin of Sivers function Soft Scattering –Low-t Physics –Total Cross Section –pbar-p interaction Physics Polarization Staging Signals FAIR

7. PAX experiment 7 Physics Case: Central Physics Issue Transversity distribution of the nucleon: –last leading-twist missing piece of the QCD description of the partonic structure of the nucleon –directly accessible uniquely via the double transverse spin asymmetry A TT in the Drell-Yan production of lepton pairs –theoretical expectations for A TT in DY > 0.2 transversely polarized antiprotons transversely polarized proton target –definitive observation of h 1 q (x,Q 2 ) of the proton for the valence quarks Physics Polarization Staging Signals FAIR

8. PAX experiment 8Transversity -Probes relativistic nature of quarks -No gluon analog for spin-1/2 nucleon -Different evolution than -Sensitive to valence quark polarization Properties : Chiral-odd: requires another chiral-odd partner Impossible in DIS Direct Measurement ppl+l-Xppl+l-X ep   e’h  X Indirect Measurement: Convolution of with unknown fragment. fct. Physics Polarization Staging Signals FAIR

9. PAX experiment 9 Transversity in Drell-Yan processes p p QLQL Q l+l+ l-l- Q 2 =M 2 QTQT Polarized Antiproton Beam → Polarized Proton Target (both transversely polarized) M invariant Mass of lepton pair Physics Polarization Staging Signals FAIR

10. PAX experiment 10 PAX: s~30-210 GeV 2, M 2 ~10-100 GeV 2,  =x 1 x 2 =M 2 /s~0.05-0.6 → Exploration of valence quarks (h 1 q (x,Q 2 ) large) A TT for PAX kinematic conditions A TT /a TT > 0.2 Models predict |h 1 u |>>|h 1 d | Physics Polarization Staging Signals FAIR RHIC: √s = 200 GeV, M 2 ≤100 GeV2 τ=x 1 x 2 =M 2 /s ≤2x10 -3 → Exploration of the sea quark content (polarizations small!) A TT very small (~ 1 %) Barone, Calarco, Drago Martin, Schaefer, Stratmann, Vogelsang A. Efremov et al. Eur. Phys. J. C 35 (2004) 207

11. PAX experiment 11 Energy for Drell-Yan processes “safe region”: M≥M J/   ≥ M 2 J/  /s QCD corrections at smaller M? H. Schimizu, G. Sterman, W. Vogelsang and H. Yokoya, hep-ph/0503270 V. Barone et al., in preparation Physics Polarization Staging Signals FAIR

12. PAX experiment 12 NLO corrections: cross section Physics Polarization Staging Signals FAIR

13. PAX experiment 13 NLO corrections: A TT Physics Polarization Staging Signals FAIR

14. PAX experiment 14 ql+l+ l-l- ql+l+ l-l- All vector couplings, same spinor structure Measure A TT also in J/  resonance region M. Anselmino, V. Barone, A. Drago, N. Nikolaev Physics Polarization Staging Signals FAIR Resonance region

15. PAX experiment 15 Proton Electromagnetic Formfactors Measurement of relative phases of magnetic and electric FF in the time-like region –Possible only via SSA in the annihilation pp → e + e - Double-spin asymmetry –independent G E -G m separation –test of Rosenbluth separation in the time-like region S. Brodsky et al., Phys. Rev. D69 (2004) Physics Polarization Staging Signals FAIR

16. PAX experiment 16 p (GeV/c) Study onset of Perturbative QCD Pure Meson Land Meson exchange ∆ excitation NN potential models Transition Region Uncharted Territory Huge Spin-Effects in pp elastic scattering large t : non-and perturbative QCD High Energy small t: Reggeon Exchange large t: perturbative QCD Physics Polarization Staging Signals FAIR

17. PAX experiment 17 pp Elastic Scattering from ZGS Spin-dependence at large-P  90° cm ): Spin-dependence at large-P  (90° cm ): Hard scattering takes place only with spins . D.G. Crabb et al., PRL 41, 1257 (1978) T=10.85 GeV Similar studies in pp elastic scattering Physics Polarization Staging Signals FAIR

18. PAX experiment 18 Outline WHY? Physics Case HOW? Polarized Antiprotons WHAT?Staging Detector and signal estimate WHERE AND WHEN? The FAIR project at GSI (D) PAX: Polarized Antiproton Experiments

19. PAX experiment 19 Polarized internal target point-like5-10 mmfree jetlow density10 12 cm -2 extended200-500 mmstorage cellhigh density10 14 cm -2 Physics Polarization Staging Signals FAIR

20. PAX experiment 20 Atomic Beam Source NIM A 505, (2003) 633 The HERMES target Physics Polarization Staging Signals FAIR

21. PAX experiment 21 The HERMES target Atomic Beam Source NIM A 505, (2003) 633 P z+ = |1> + |4> P z- = |2> + |3> m j = +1/2 m j = -1/2 m i =-1/2 m i =+1/2 1 |1> |2> |3> |4> ee-ee-p |1> Physics Polarization Staging Signals FAIR

22. PAX experiment 22 The HERMES target Atomic Beam Source NIM A 505, (2003) 633 Storage cell NIM A 496, (2003) 277 Physics Polarization Staging Signals FAIR

23. PAX experiment 23 The HERMES target Atomic Beam Source NIM A 505, (2003) 633 Storage cell NIM A 496, (2003) 277 Diagnostics: Target Gas Analyzer NIM A 508, (2003) 265 Breit-Rabi Polarimeter NIM A 482, (2002) 606 Physics Polarization Staging Signals FAIR

24. PAX experiment 24 Performance of Polarized Internal Targets P T = 0.795  0.033 HERMES H Transverse Field (B=297 mT) HERMES DzDz D zz P T = 0.845 ± 0.028 Longitudinal Field (B=335 mT) HERMES: Stored Positrons PINTEX: Stored Protons H Fast reorientation in a weak field (x,y,z) Targets work very reliably (months of stable operation) Physics Polarization Staging Signals FAIR

25. PAX experiment 25 Principle of spin filter method P beam polarization Q target polarization k || beam direction σ tot = σ 0 + σ  ·P·Q + σ || ·(P·k)(Q·k) transverse case:longitudinal case: For initially equally populated spin states:  (m=+½) and  (m=-½) Unpolarized anti-p beam Polarized H target Physics Polarization Staging Signals FAIR

26. PAX experiment 26 Principle of spin filter method P beam polarization Q target polarization k || beam direction σ tot = σ 0 + σ  ·P·Q + σ || ·(P·k)(Q·k) transverse case:longitudinal case: For initially equally populated spin states:  (m=+½) and  (m=-½) Unpolarized anti-p beam Polarized H target Polarized anti-p beam Physics Polarization Staging Signals FAIR

27. PAX experiment 27 Principle of spin filter method P beam polarization Q target polarization k || beam direction σ tot = σ 0 + σ  ·P·Q + σ || ·(P·k)(Q·k) transverse case:longitudinal case: For initially equally populated spin states:  (m=+½) and  (m=-½) Expectation TargetBeam   For low energy pp scattering:  1 <0   tot+ <  tot- Physics Polarization Staging Signals FAIR

28. PAX experiment 28 Experimental Setup at TSR (1992) Physics Polarization Staging Signals FAIR

29. PAX experiment 29 1992 Filter Test at TSR with protons Experimental Setup Results F. Rathmann. et al., PRL 71, 1379 (1993) T=23 MeV Physics Polarization Staging Signals FAIR

30. PAX experiment PAX: Polarized Antiproton Experiments 30 Puzzle from FILTEX Test Observed polarization build-up: dP/dt = ± (1.24 ± 0.06) x 10 -2 h -1 Expected build-up: P(t)=tanh(t/τ pol ), 1/τ pol =σ 1 Qd t f=2.4x10 -2 h -1  about factor 2 larger! σ 1 = 122 mb (pp phase shifts) Q = 0.83 ± 0.03 d t = (5.6 ± 0.3) x 10 13 cm -2 f = 1.177 MHz Three distinct effects: 1.Selective removal through scattering beyond Ψ acc =4.4 mrad σ R  =83 mb 2.Small angle scattering of target protons into ring acceptance σ S  =52 mb 3.Spin transfer from polarized electrons of the target atoms to the stored protons σ EM  =70 mb (-) Horowitz & Meyer, PRL 72, 3981 (1994) H.O. Meyer, PRE 50, 1485 (1994)

31. PAX experiment PAX: Polarized Antiproton Experiments 31 Spin transfer from electrons to protons Horowitz & Meyer, PRL 72, 3981 (1994) H.O. Meyer, PRE 50, 1485 (1994) α fine structure constant λ p =(g-2)/2=1.793anomalous magnetic moment m e, m p rest masses pcm momentum a 0 Bohr radius C 0 2 =2πη/[exp(2πη)-1]Coulomb wave function η=zα/νCoulomb parameter (negative for antiprotons) vrelative lab. velocity between p and e zbeam charge number Polarization Staging Signals Timeline

32. PAX experiment 32 Spin Transfer Cross Section 101001000T (MeV)  EM  (mbarn) 100 10 1 Physics Polarization Staging Signals FAIR

33. PAX experiment 33 Beam lifetimes in the APR 101001000T (MeV) 40 30 25 ψ acc (mrad) 20 10 2 4 6 8 beam lilfetime τ beam (h) 10 Beam Lifetime Coulomb Loss Total Hadronic Physics Polarization Staging Signals FAIR

34. PAX experiment 34 Polarization Buildup: optimal polarization time statistical error of a double polarization observable (A TT ) Measuring time t to achieve a certain error δ ATT ~ FOM = P 2 ·I (N ~ I) Optimimum time for Polarization Buildup given by maximum of FOM(t) t filter = 2·τ beam 02 4 6 t/τ beam I/I 0 0.2 0.4 0.6 0.8 Beam Polarization Physics Polarization Staging Signals FAIR

35. PAX experiment 35 Optimum Beam Energies for Buildup in APR ψ acc = 50 mrad 40 mrad 30 mrad 20 mrad AP Space charge limit 1 10 T (MeV) 100 10 mrad FOM 5 10 15 Maximum FOM Ψ acc (mrad) Τ beam (h) P(2·τ beam ) T (MeV) 101.20.19163 202.20.2988 304.60.3561 409.20.3947 5016.70.4238 F. Rathmann et al., Phys. Rev. Lett. 94, 014801 (2005) Physics Polarization Staging Signals FAIR

36. PAX experiment 36 0.1 0.2 0.3 0.4 Beam Polarization P(2·τ beam ) 10 T (MeV)100 EM only 5 10 30 20 40 Ψ acc =50 mrad 0 1 Filter Test: T = 23 MeV Ψ acc = 4.4 mrad Beam Polarization Physics Polarization Staging Signals FAIR

37. PAX experiment 37 Antiproton Polarizer Ring (APR) e-cooler APR ABS Siberian Snake B Injection 100 m Polarizer Target RING PARAMETERS: Energy:50 MeV (p~300 MeV/c)  x,y : 500  mm mrad Circumeference:100 m No. Particles:10 12 EQUIPMENT: Polarized target Snake e-cool Stochastic cooling? PROJECTION: P > 30% after 18-20 hrs (10 11 pbar) Physics Polarization Staging Signals FAIR

38. PAX experiment 38 Spin-filtering with hadronic interaction Model A: T. Hippchen et al. Phys. Rev. C 44, 1323 (1991) P Kinetic energy (MeV) 10 100 10001 0.05 0.10 0.15 0.20 Model D: V. Mull, K. Holinde, Phys. Rev. C 51, 2360 (1995) P Kinetic energy (MeV) 10 100 10001 0.05 0.10 0.15 0.20 Physics Polarization Staging Signals FAIR

39. PAX experiment 39 Outline WHY? Physics Case HOW? Polarized Antiprotons WHAT?Staging Detector and signal estimate WHERE AND WHEN? The FAIR project at GSI (D) PAX: Polarized Antiproton Experiments

40. PAX experiment 40 Staging: Phase I (PAX@CSR) Physics:EMFF pbar-p elastic Experiment: pol./unpol. Pbar (3.5 GeV/c) on int. pol. target Independent from HESR running Physics Polarization Staging Signals FAIR

41. PAX experiment 41 Staging: Phase II (PAX@HESR) EXPERIMENT: 1. Asymmetric collider: polarized antiprotons in HESR (p=15 GeV/c) polarized protons in CSR (p=3.5 GeV/c) 2. Internal polarized target with 22 GeV/c polarized antiproton beam. Physics: Transversity Second IP with minor interference with PANDA Physics Polarization Staging Signals FAIR

42. PAX experiment 42 Outline WHY? Physics Case HOW? Polarized Antiprotons WHAT?Staging Detector and signal estimate WHERE AND WHEN? The FAIR project at GSI (D) PAX: Polarized Antiproton Experiments

43. PAX experiment 43 Kinematics and cross section M 2 = s x 1 x 2 x F =2Q L /√s = x 1 -x 2 Estimated luminosities: Fixed target: 2.7x10 31 cm -2 s -1 Collider:1-2 x 10 30 cm -2 s -1 M (GeV/c 2 ) 22 GeV collider 2 k events/day Physics Polarization Staging Signals FAIR

44. PAX experiment 44 A TT asymmetry: angular distribution Needs a large acceptance detector (LAD) Asymmetry is largest for angles  =90 ° Asymmetry varies like cos(2  ). Physics Polarization Staging Signals FAIR

45. PAX experiment 45 Designed for Collider but compatible with fixed target Cerenkov (200  m) (20  m) GEANT simulation PAX detector concept Physics Polarization Staging Signals FAIR

46. PAX experiment 46 Estimated signal for h 1 (phase II) 1 year of data taking Collider: L=2x10 30 cm -2 s -1 Fixed target: L=2.7x10 31 cm -2 s -1 Physics Polarization Staging Signals FAIR

47. PAX experiment PAX: Polarized Antiproton Experiments 47 Beam (MeV/c) (GeV 2 )  e+e- (nbarn)* L (cm -2 s -1 ) Days DS Days SS 5493.767.37.8x10 30 2.90.3 9004.183.71.1x10 31 4.70.5 36008.750.0441.5x10 31 13213 N pbar = 1x10 11 f=L CSR /  c d t =1x10 14 cm -2 Q=0.8 (p pol) P=0.3 (pbar pol)  =0.5 Estimated signal for EMFF (Phase I) PS170 and E835 PAX could run down to 200 MeV/c with double polarization Running days to get  O = 0.05 Polarization Staging Signals Timeline

48. PAX experiment PAX: Polarized Antiproton Experiments 48 BNL E838 Estimated Signal for pbar p elastic (Phase I) Cross section estimation for p=3.6 GeV/c,  =120° Event rate (  t=0.1 GeV 2 ): 2 hours to get N  10 Polarization Staging Signals Timeline

49. PAX experiment PAX: Polarized Antiproton Experiments 49 PAX Integrated Luminosities for Physics Cases pb -1 fb -1 Integrated Luminosity EMFF, DSA, s=3.76 GeV 2 ppbar elastic, DSA, t=4 GeV 2 Phase-I: L=1.5·10 31 cm -2 s -1 Antiproton Beam Polarization P pbar =0.3, Proton Polarization P p =0.8 Phase-II: L=2·10 30 cm -2 s -1 EMFF, DSA, s=9 GeV 2 Absolute Error Δ DSA =0.05 h 1, DSA, M>2 GeV, Δ=10% h 1, DSA, M>4 GeV, Δ=20% (1 y) (4 y) (1 y)

50. PAX experiment 50 Outline WHY? Physics Case HOW? Polarized Antiprotons WHAT?Staging Detector and signal estimate WHERE AND WHEN? The FAIR project at GSI (D) PAX: Polarized Antiproton Experiments

51. PAX experiment 51 Faciltiy for Antiproton and Ion Research (GSI, Darmstadt, Germany) (GSI, Darmstadt, Germany) -Proton linac (injector) -2 synchrotons (30 GeV p) -A number of storage rings  Parallel beams operation Physics Polarization Staging Signals FAIR

52. PAX experiment 52 FLAIR: (Facility for very Low energy Anti- protons and fully stripped Ions) SIS100/300 HESR: High Energy Storage Ring: PANDA and PAX NESR CR-Complex The FAIR project at GSI The FAIR project at GSI 50 MeV Proton Linac Physics Polarization Staging Signals FAIR

53. PAX experiment 53 Phase 0: 2005-2012 Polarization tests, polarizer design and construction. Phase I: 2013-2017 APR+CSR @ GSI Physics: EMFF with fixed target Phase II: 2018 - … HESR+CSR asymmetric collider Physics: h 1 Timeline Timeline Physics Polarization Staging Signals FAIR

54. PAX experiment 54 Conclusions Challenging opportunities accessible with polarized pbar. Unique access to a wealth of new fundamental physics observables Central physics issue: h 1 q (x,Q 2 ) of the proton in DY processes Other issues: Electromagnetic Formfactors Polarization effects in Hard and Soft Scattering processes differential cross sections, analyzing powers, spin correlation parameters Staging approach Projections for double polarization experiment (tests) : P beam > 0.30 L> 1.6 ·10 30 cm -2 s -1 (Collider), L  2.7 ·10 31 cm -2 s -1 (fixed target) Detector concept: Large acceptance detector with a toroidal magnet

55. PAX experiment 55 Georg Christoph Lichtenberg (1742-1799) “Man muß etwas Neues machen, um etwas Neues zu sehen.” “You have to make something new, if you want to see something new”