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PAX P olarized A ntiproton E X periment

dr. Paolo Lenisa Universita’ and INFN - Sezione di Ferrara. PAX P olarized A ntiproton E X periment. PAX Collaboration www.fz-juelich.de/ikp/pax Spokespersons: Frank Rathmann f.rathmann@fz-juelich.de Paolo Lenisa lenisa@mail.desy.de. PAX Collaborators. Ma Bo-Qiang

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PAX P olarized A ntiproton E X periment

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  1. dr. Paolo Lenisa Universita’ and INFN - Sezione di Ferrara PAXPolarizedAntiproton EXperiment PAX Collaboration www.fz-juelich.de/ikp/pax Spokespersons: Frank Rathmann f.rathmann@fz-juelich.de Paolo Lenisa lenisa@mail.desy.de

  2. PAX Collaborators Ma Bo-Qiang Department of Physics, Beijing, P.R. China Klaus Goeke, Andreas Metz, and Peter Schweitzer Institut für Theoretische Physik II, Ruhr Universität Bochum, Germany Jens Bisplinghoff, Paul-Dieter Eversheim, Frank Hinterberger, Ulf-G. Meißner, and Heiko Rohdjeß Helmholtz-Institut für Strahlen- und Kernphysik, Bonn, Germany Sergey Dymov, Natela Kadagidze, Vladimir Komarov,Anatoly Kulikov, Vladimir Kurbatov, Vladimir Leontiev, Gogi Macharashvili, Sergey Merzliakov, Valerie Serdjuk, Sergey Trusov, Yuri Uzikov, Alexander Volkov, and Nikolai Zhuravlev Laboratory of Nuclear Problems, Joint Institute for Nuclear Research, Dubna, Russia Igor Savin, Vasily Krivokhizhin, Alexander Nagaytsev, Gennady Yarygin, Gleb Meshcheryakov, Binur Shaikhatdenov, Oleg Ivanov, Oleg Shevchenko, and Vladimir Peshekhonov Laboratory of Particle Physics, Joint Institute for Nuclear Research, Dubna, Russia Wolfgang Eyrich, Andro Kacharava, Bernhard Krauss, Albert Lehmann, David Reggiani, Klaus Rith, Ralf Seidel, Erhard Steffens, Friedrich Stinzing, Phil Tait, and Sergey Yaschenko Physikalisches Institut, Universität Erlangen-Nürnberg, Germany Guiseppe Ciullo, Marco Contalbrigo, Marco Capiluppi, Paola Ferretti-Dalpiaz, Alessandro Drago, Paolo Lenisa, Michelle Stancari, and Marco Statera Instituto Nationale di Fisica Nucleare, Ferrara, Italy Nicola Bianchi, Enzo De Sanctis, Pasquale Di Nezza, Delia Hasch, Valeria Muccifora, Karapet Oganessyan, and Patrizia Rossi Instituto Nationale di Fisica Nucleare, Frascati, Italy

  3. (continued) Stanislav Belostotski, Oleg Grebenyuk, Kirill Grigoriev, Peter Kravtsov, Anton Izotov, Anton Jgoun, Sergey Manaenkov, Maxim Mikirtytchiants, Oleg Miklukho, Yuriy Naryshkin, Alexandre Vassiliev, and Andrey Zhdanov Petersburg Nuclear Physics Institute, Gatchina, Russia Dirk Ryckbosch Department of Subatomic and Radiation Physics, University of Gent, Belgium David Chiladze, Ralf Engels, Olaf Felden, Johann Haidenbauer, Christoph Hanhart, Andreas Lehrach, Bernd Lorentz, Nikolai Nikolaev, Siegfried Krewald, Sig Martin, Dieter Prasuhn, Frank Rathmann, Hellmut Seyfarth, Alexander Sibirtsev, and Hans Ströher Forschungszentrum Jülich, Institut für Kernphysik Jülich, Germany Ashot Gasparyan, Vera Grishina, and Leonid Kondratyuk Institute for Theoretical and Experimental Physics, Moscow, Russia Alexandre Bagoulia, Evgeny Devitsin, Valentin Kozlov, Adel Terkulov, and Mikhail Zavertiaev Lebedev Physical Institute, Moscow, Russia N.I. Belikov, B.V. Chuyko, Yu.V. Kharlov, V.A. Korotkov, V.A. Medvedev, A.I. Mysnik, A.F. Prudkoglyad, P.A. Semenov, S.M. Troshin, and M.N. Ukhanov High Energy Physics Institute, Protvino, Russia Mikheil Nioradze, and Mirian Tabidze High Energy Physics Institute, Tbilisi State University, Tbilisi, Georgia Mauro Anselmino, Vincenzo Barone, Mariaelena Boglione, and Alexei Prokudin Dipartimento di Fisica Teorica, Universita di Torino and INFN, Torino, Italy Norayr Akopov, R. Avagyan, A. Avetisyan, S. Taroian, G. Elbakyan, H. Marukyan, and Z. Hakopov Yerevan Physics Institute, Yerevan, Armenia

  4. Outline • The Future GSI Facility • Physics Case • Transversity • SSA • Electromagnetic Form Factors • Antiproton Polarizer • Polarized Internal Target • Polarization Buildup • Beam lifetimes • Requirements for HESR • Detector Concept • Forward Spectrometer • Large Acceptance Spectrometer • Physics Performance • Conclusion

  5. Future Int. Accelerator Facility at GSI SIS100/300 HESR: PANDA and PAX FLAIR: (Facility for very Low energy Anti-protons and fully stripped Ions) CR-Complex NESR

  6. Super FRS CR RESR Antiproton Production Target Gas Target and Pellet Target: cooling power determines thickness NESR • Cooling – e- and/or stochastic • 2MV prototype e-cooling at COSY The Antiproton Facility HESR (High Energy Storage Ring) • Length 442 m • Bρ = 50 Tm • N = 5 x 1010 antiprotons High luminosity mode • Luminosity = 2 x 1032 cm-2s-1 • Δp/p ~ 10-4 (stochastic-cooling) High resolution mode • Δp/p ~ 10-5 (8 MV HE e-cooling) • Luminosity = 1031 cm-2s-1 HESR • Antiproton production similar to CERN • Production rate 107/sec at 30 GeV • Energy = 1.5 - 15 GeV/c

  7. Spin-average Helicity-difference Helicity-flip The Central Physics Issue Twist-2 distribution functions

  8. Transversity, Remains still unmeasured Poorly modeled A review in: Barone, Drago,Ratcliffe, Phys. Rep. 359 (2002) 1 Well known and well modeled Known, but poorly modeled Status of knowledge

  9. Properties: • Probes relativistic nature of quarks • No gluon analog for spin-1/2 nucleon • Different evolution than • Sensitive to valence quark polarization Transversity Chiral-odd: requires another chiral-odd partner

  10. PAX:Polarizedantiproton beam → polarizedproton target (both transverse) l+ q2=M2 l- q qT p p qL M invariant Mass of lepton pair Elementary QED process θ: polar angle of lepton in l+l- rest frame : azimuthal angle w.r.t. proton polarization Transversity in Drell-Yan processes

  11. 0.3 ATT/aTT > 0.3 Models predict |h1u|>>|h1d| 0.25 T=15 GeV 0.15 T=22 GeV 0.15 Anselmino, Barone, Drago, Nikolaev (hep-ph/0403114 v1) Main contribution to Drell-Yan events at PAX from x1~x2~τ deduction of x-dependence of h1u(x,M2)! 0 0.2 0.4 0.6 xF=x1-x2 ATT in the Drell-Yan production at PAX RHIC: τ=x1x2=M2/s~10-3 → Exploration of the sea quark content(polarizations small!) ATT very small (~ 1 %) PAX: M2~10 GeV2, s~30-50 GeV2, τ=x1x2=M2/s~0.2-0.3 →Exploration ofvalence quarks(h1q(x,Q2) large)

  12. Single Spin Asymmetries Several experiments have observed unexpectedly large single spin asymmetries in pbar-p at large values of xF ≥ 0.4 and moderate values of pT (0.7 < pT < 2.0 GeV/c) E704 Tevatron FNAL 200GeV/c π+ Large asymmetries originate from valence quarks: sign of AN related to u and d-quark polarizations π- xF

  13. Gauge Link structure: Universality violation? Gauge invariant definition of T-odd distribution function in DIS contains a future pointing Wilson line, whereas in Drell-Yan (DY) it is past pointing DIS DY Collins, PLB 536 (2002) 43 Requires experimental checks

  14. 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 GE-Gm separation • test of Rosenbluth separation in the time-like region

  15. Polarized internal target

  16. Example: The HERMES target

  17. Atomic Beam Source • NIM A 505, (2003) 633 The HERMES target

  18. Atomic Beam Source • NIM A 505, (2003) 633 The HERMES target Pz+ = |1> + |4> Pz- = |2> + |3>

  19. 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 The HERMES target

  20. Target polarization • PT = total target polarization • a0 =atomic fractionin absence of recombination • ar=atomic fractionsurviving recombination • Pa= polarization of atoms • Pm = polarization of recombined molecules • Relation to measured quantities: • Sampling corrections • ar=caarTGA • Pa= cPPaBRP

  21. Target performance • Longitudinal Polarization (B=335 mT) • 1996-1997 Hydrogen • 1999-2000 Deuterium Pt = 0.845 ± 0.028

  22. Target performance • Longitudinal Polarization (B=335 mT) • 1996-1997 Hydrogen • 1999-2000 Deuterium Pt = 0.845 ± 0.028

  23. Target performance • Tranverse Polarization (B=297 mT) • 2002 - … Hydrogen PT = 0.795  0.033

  24. ( ) ) ( P beampol. Q targetpol. k || beam s = s + s × × + s × × × × P P Q k Q k tot 0 1 2 ( ) = × = 0 , if P k 0 For initially equally populated spin states:  (m=½)  (m=-½) s = s ± s × Q ± tot 0 1 Principle of Spin Filter Method For low energy pp scattering: 1<0  tot+<tot-

  25. Results T=23 MeV F. Rathmann. et al., PRL 71, 1379 (1993) Filter Test at TSR with protons Experimental Setup

  26. Expectedbuild-up: P(t)=tanh(t/τ1), • 1/τ1=σ1Qdtf=2.4x10-2 h-1 •  about factor 2 larger! σ1 = 122 mb (pp phase shifts) Q = 0.83 ± 0.03 dt = (5.6 ± 0.3) x 1013cm-2 f = 1.177 MHz Three distinct effects: • Selective removal through scattering beyond θacc=4.4 mradσR=83 mb • Small angle scattering of target protons into ring acceptanceσS=52 mb • Spin transfer from polarized electrons of the target atoms to the stored protons σE=-70 mb Horowitz & Meyer, PRL 72, 3981 (1994) H.O. Meyer, PRE 50, 1485 (1994) Puzzle from FILTEX Test Observed polarization build-up: dP/dt = ± (1.24 ± 0.06) x 10-2 h-1

  27. Spin transfer from electrons to protons Horowitz & Meyer, PRL 72, 3981 (1994) H.O. Meyer, PRE 50, 1485 (1994) α fine structure constant λp=(g-2)/2=1.793 anomalous magnetic moment me, mp rest masses p cm momentum a0 Bohr radius C02=2πη/[exp(2πη)-1] Coulomb wave function η=-zα/ν Coulomb parameter (neg. for anti-protons) v relative lab. velocity between p and e z beam charge number

  28. The lifetime of a stored beam is given by 20 mrad 10 5 mrad 10 mrad 8 (Target thickness = dt=5·1014 atoms/cm2) 6 beam lilfetime τb (h) 4 Ψacc = 1 mrad 2 400 800 1200 T (MeV) Beam lifetimes in HESR In order to achieve highest polarization in the antiproton beam, acceptance angles around Ψacc = 10 mrad are needed.

  29. N(t)=N0exp(-t/τb) τb=(fdtσL)-1 I(t)=N(t) f P(t)=1-exp(-t/τ1)~ σEdtfQt Optimum filtering time: t=2τb (from d(P2I)/dt=0)  P(2τb)=2Q (σE/σL) Estimate for σL from Indiana Cooler σL=4.75 107 T-2 mb , (Note: σE~T-1) R.E. Pollock et al., NIM A 330, 380 (1993) Polarization Build-up • Exploit spin transfer process σE • works also if hadronic polarizing cross sections σRandσSturn out to be small

  30. Expected Buildup spin-transfer cross section (electrons to antiprotons) dt=5·1014 atoms/cm2 Pelectron=0.9 8 100 T=500 MeV 6 Goal 10 4 e (mbarn) antiproton Polarization (%) 1 T=800 MeV 2 5 10 15 20 t (h) 10 100 1000 T (MeV) Antiproton Polarizer

  31. Polarization Conservation in a Storage Ring H.O. Meyer et al., PRE 56, 3578 (1997) Indiana Cooler HESR design must allow for storage of polarized particles!

  32. Stored protons: P(n)=Pi()n  =(99.3±0.1)% Spin Manipulation in a Storage Ring • SPIN@COSY (A. Krisch et. al) • Frequent spin-flips reduce systematic errors • Spin-Flipping of protons and deuterons by artifical resonance • RF-Dipole • Applicable at High Energy Storage Rings (RHIC, HESR)

  33. Polarimetry Different schemes to determinetargetandbeampolariz. • Suitable target polarimeter (Breit-Rabi or Lamb-Shift) to measure target polarization • At lower energies (500-800 MeV) analyzing power data from PS172 are available. • Therefrom a suitable detector asymmetry can be calibrated • → effective analyzing power • Beam and target analyzing powersare identical • measure beam polarization using an unpolarized target • Export of beam polarization to other energies • target polarization is independent of beam energy

  34. Detector Concept Two complementary parts: • Forward detector (±8o acceptance) a la HERMES • Identify unambiguously leading particles • Measure precisely their momenta • Central Large Acceptance Detector • Measure angles and energies of medium energy electromagnetic particles (Drell-Yan)

  35. Forward Detector

  36. Large Acceptance Detector

  37. Physics Performance • Luminosity • Spin-filtering for two beam lifetimes:P > 5% • N(pbar) =5·1011at fr~6·105 s-1 • dt = 5·1014 cm-2 • Time-averaged luminosity is about factor 3 lower • beam loss and duty cycle • Experiments with unpolarized beam • L factor 10 larger

  38. 240 days T = 15 GeV only non-resonant J/Ψcontribution included T = 22 GeV Count rate estimate Note: Conservative estimate since hadronic buildup effect might be large as well Uncertainty in ATT depends on target and beam polarization( |P|>0.05, |Q|~0.9)

  39. unknown vector coupling, but same Lorentz and spinor structure as other two processes Unknown quantities cancel in the ratios for ATT, but helicity structure remains! Cross section increases by two orders from M=4 to M=3 GeV →Drell-Yan continuum enhances sensitivity of PAX to ATT Anselmino, Barone, Drago, Nikolaev (hep-ph/0403114 v1) Extension of the “safe” region h1q(x,Q2) not confined to „safe“ region M > 4 GeV!

  40. Machine design(more beam!) • Need separate target station • HESR must be capable to store polarized antiprotons • Polarization buildup requires large acceptance angle (10 mrad) • Storage cell target requires low-β section • Slow ramping of beam energy needed to optimize pol. build-up Conclusion Challenging opportunities and new physics accessible with PAX at HESR • unique access to a wealth of new fundamental physics observables • polarized antiprotons (P>5%) • Central physics issue: h1q(x,Q2) 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

  41. PAX: The next steps Jan.2004 LOI submitted Formation of an advisory committee at GSI Apr.-May 2004Evaluation of LOI’s (If approved) 15.12.2004 Techn. Report (with Milesones) Evaluations & Green Light for Construction 2005-2008 Technical Design Reports (for Milestones) 2012 Commissioning of HESR

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