P. Lenisa The PAX project 1 Paolo Lenisa – Università and INFN – Ferrara, ITALY Trento, July 6 th PAX Polarized Antiproton Experiments

P. Lenisa The PAX project 2 PAX Collaboration TIMELINE Jan. 04 Letter of Intent for FAIR May 04QCD-PAC meeting at GSI Aug. 04Workshop on polarized antiprotons at GSI Jan. 05 Technical Proposal for FAIR Mar. 05QCD-PAC meeting at GSI Nov. 05LoI to CERN-SPSC to perform spin-filtering experiments with antiprotons at the AD ring Apr. 06LoI to COSY-PAC for spin filtering experiments with protons at COSY 180 physicists 35 institutions (15 EU, 20 NON-EU)

P. Lenisa The PAX project 3 … the PAC would like to stress again the uniqueness of the program with polarized anti-protons and polarized protons that could become available at GSI. Evaluation by QCD-PAC (March 2005) The STI requests R&D work to be continued on the proposed asymmetric collider experiment with both polarized anti-protons and protons: t o demonstrate that a high degree of anti-proton polarization can be reached The STI believes that PAX should become part of the FAIR core research program based on its strong scientific merit once the open problems are convincingly solved. Recommendation of the STI of FAIR (Sept. 2005)

P. Lenisa The PAX project 4 Physics Motivations

P. Lenisa The PAX project 5 Physics with polarized antiprotons at GSI-PAX Transversity via Drell-Yan processes direct access to transversity Transverse Single Spin Asymmetries QCD “theorem”: (Sivers) D-Y = – (Sivers) DIS Time-like e.l.m. form factors form factors Elastic processes spin mysteries like in pp ? High Energy Low Energy

P. Lenisa The PAX project 6 h 1 from pbar-p Drell-Yan at GSI Similar predictions by Efremov et al., Eur. Phys. J. C35, 207 (2004) PAX : M 2  s=x 1 x 2 ~ → valence quarks (A TT large ~ ) Anselmino et al. PLB 594,97 (2004)

P. Lenisa The PAX project 7 10 % precision on the h 1 u (x) in the valence region 1 year of data taking at GeV collider L = 2∙10 30 cm -2 s -1 Precision in h 1 measurement Precision in h 1 measurement (L~10 31 reachable)

P. Lenisa The PAX project 8 Barone, Calarco, Drago Martin, Schäfer, Stratmann, Vogelsang What about p-p? h 1q (x, Q 2 ) small and with much slower evolution than Δq(x, Q 2 ) and q(x, Q 2 ) at small x h 1q (x, Q 2 ) - ≠ RHIC: τ=x 1 x 2 ~10 -3 → sea quarks (A TT ~ 0.01 ) JPARC/U70: τ=x 1 x 2 ~10 -1 → valence and sea (A TT ~ 0.1 ) PAX: τ=x 1 x 2 ~10 -1 → valence and sea (A TT ~ 0.1 )

P. Lenisa The PAX project 9 DY in p-p: A TT Aymmetry is large at PAX energy (> 0.1) Sign of the asymmetry will distinguish between the two models. It will give indications about calculation of sea distributions. 1 2 Asymmetries evoluted from the assumptions: CDM (~CQSM) 2 1 A. Drago

P. Lenisa The PAX project 10 p-pbar DY events distribution (√s~15 GeV) p-pbar +p-p -> complete map of transversity p-p Extraction of h 1u for x>0.2 x 1 =x 2 ->A TT ~h 1u 2 Direct measurement of h 1u for 0.15<x<0.5 M 2 /s=x 1 x 2 ~

P. Lenisa The PAX project 11 Val. scenario Std. scenario x F =x 1 -x 2 DY in p-p: A LL Large asymmetries expected Test of the assumptions of the fits Models: Val. scenario: Std. scenario:

P. Lenisa The PAX project 12 Physics with polarized antiprotons at GSI-PAX Transversity via Drell-Yan processes direct access to transversity Transverse Single Spin Asymmetries QCD “theorem”: (Sivers) D-Y = – (Sivers) DIS Time-like e.l.m. form factors form factors Elastic processes spin mysteries like in pp ? High Energy Low Energy

P. Lenisa The PAX project 13 Single Spin Asymmetries (and their partonic origin) pqpq PqPq π k┴k┴ Collins effect = fragmentation of polarized quark depends on P q · (p q x k ┴ ) P p k┴k┴ Sivers effect = number of partons in polarized proton depends on P · (p x k ┴ ) q p k┴k┴ Boer-Mulders effect = polarization of partons in unpolarized proton depends on P q · (p x k ┴ ) q PqPq Collins: chiral-odd Sivers: chiral-even Boer-Mulders: chiral-odd These effects may generate SSA

P. Lenisa The PAX project 14 BNL-AGS √s = 6.6 GeV 0.6 < p T < 1.2 p ↑ p E704 √s = 20 GeV 0.7 < p T < 2.0 p ↑ p STAR-RHIC √s = 200 GeV 1.1 < p T < 2.5 p ↑ p E704 √s = 20 GeV 0.7 < p T < 2.0 p ↑ p SSA, pp → πX

P. Lenisa The PAX project 15 Physics with polarized antiprotons at GSI-PAX Transversity via Drell-Yan processes direct access to transversity Transverse Single Spin Asymmetries QCD “theorem”: (Sivers) D-Y = – (Sivers) DIS Time-like e.l.m. form factors form factors Elastic processes spin mysteries like in pp ? High Energy Low Energy

P. Lenisa The PAX project 16 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

P. Lenisa The PAX project 17 Physics with polarized antiprotons at GSI-PAX Transversity via Drell-Yan processes direct access to transversity Transverse Single Spin Asymmetries QCD “theorem”: (Sivers) D-Y = – (Sivers) DIS Time-like e.l.m. form factors form factors Elastic processes spin mysteries like in pp ? High Energy Low Energy

P. Lenisa The PAX project 18 Proton Electromagnetic Formfactors Single-spin asymmetry in pp → e + e - –Measurement of relative phases of magnetic and electric FF in the time-like region Double-spin asymmetry in pp → e + e - –independent G E -G m separation –test of Rosenbluth separation in the time-like region S. Brodsky et al., Phys. Rev. D69 (2004)

P. Lenisa The PAX project 19 Experimental setup

P. Lenisa The PAX project 20 PAX Accelerator Setup Antiproton Polarizer Ring (APR) Asymmetric Antiproton-Proton Collider (CSR) High Energy Synchrotron Ring (HESR)

P. Lenisa The PAX project 21 Antiproton Polarizer Ring Energy250 MeV  250 mm mrad Circumf.86 m

P. Lenisa The PAX project 22 Staging: Phase I Physics:EMFF pbar-p elastic Experiment: pol./unpol. pbar on internal polarized target Independent from HESR running

P. Lenisa The PAX project 23 Staging: Phase II EXPERIMENT: Asymmetric collider : polarized antiprotons in HESR (p=15 GeV/c) polarized protons in CSR (p=3.5 GeV/c) Physics: Transversity Second IP with minor interference with PANDA

P. Lenisa The PAX project 24 ParameterBunchedCoasting CSRHESRCSRHESR Particlespbarp p Circum. [m] P max [GeV/c] s max [GeV 2 ]~ 200 No. bunches No. particles5x x x x10 13 Lifetime [hs]~1500~300~1500~300 Lum. [cm -2 s -1 ]5x x10 31 Polar. ↑↑, →→, ↑→ p-pyes Parameters

P. Lenisa The PAX project 25 Symmetric collider Circum.[m]681 No. Bunches10 No. p1x10 12 No pbar1x10 12 S max [GeV 2 ]~900 Polar. ↑↑,→→↑↑,→→ p-pno Asymm. collider Luminosity

P. Lenisa The PAX project 26 PAX Detector Concept PAX Detector Concept Physics: h 1 distribution sin 2  EMFF sin2  pbar-p elastic high |t| Detector: Extremely rare DY signal (10 -7 p-pbar) Maximum Bjorken-x coverage (M interval) Excellent PID (hadron/e rejection ~ 10 4 ) High mass resolution (≤2 %) Moderate lepton energies (0.5-5 GeV) Azimuthally Symmetric: BARREL GEOMETRY LARGE ANGLES Experiment: Flexible Facility e+e-e+e-

P. Lenisa The PAX project 27 Kinematics for Drell-Yan processes QCD corrections might be very large at smaller values of M, for cross- sections, not for A TT : K-factor almost spin-independent H. Shimizu, G. Sterman, W. Vogelsang and H. Yokoya, hep-ph/ V. Barone et al., in preparation Fermilab E GeV/c CERN NA GeV/c "safe region" Usually taken as Q 2 >4 GeV 2

P. Lenisa The PAX project 28 PAX Detector Concept PAX Detector Concept Physics: h 1 distribution sin 2  EMFF sin2  pbar-p elastic high |t| Magnet: Keeps beam polarization vertical Compatible with Cerenkov Compatible with polarized target Detector: Extremely rare DY signal (10 -7 p-pbar) Maximum Bjorken-x coverage (M interval) Excellent PID (hadron/e rejection ~ 10 4 ) High mass resolution (≤2 %) Moderate lepton energies (0.5-5 GeV) Azimuthally Symmetric: BARREL GEOMETRY LARGE ANGLES Experiment: Flexible Facility TOROID NO FRINGE FIELD e+e-e+e-

P. Lenisa The PAX project 29 PAX Detector Concept PAX Detector Concept Designed for Collider but compatible with fixed target Cerenkov (200  m) (20  m) GEANT simulation

P. Lenisa The PAX project APR final design and construction Phase I: GSI Physics: EMFF, p-pbar elastic with fixed target. Phase II: … HESR+CSR asymmetric collider Physics: h 1 The (long) way towards a The (long) way towards a polarized antiproton collider Phase 0: Pol. buildup COSY and CERN

P. Lenisa The PAX project 31

P. Lenisa The PAX project 32 SIS18HESR RESR APR CSR HESRCSR HESR Antiproton and Proton accelerators’ scheme Energy time proton antiproton

P. Lenisa The PAX project 33 Higher energy p-p machine V. Barone, T. Calarco and A. Drago Phys. Rev. D 56 (1997) 527 s  Asymmetry  PAX ideal

P. Lenisa The PAX project 34 Transverse sea M. Wakamatsu and T. Kubota Phys. Rev. D 63 (1999) V. Barone, T. Calarco and A. Drago Phys. Lett. B 390 (1997) 287 CDM CQSM The two models predict different sign for  (with comparable amplitude).

P. Lenisa The PAX project 35 Longitudinal sea M. Glück et al. Phys. Rev. D 63 (2001) Models: Val. scenario: Std. scenario: