PAX Polarized. Antiproton. EXperiment. PAX Collaboration. Paolo Lenisa. Universita and INFN - Sezione di Ferrara.

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1 dr. Paolo Lenisa Universita and INFN - Sezione di Ferrara PAX Polarized Antiproton EXperiment PAX Collaboration Frank Rathmann Paolo Lenisa Spokespersons: f.rathmann@fz-juelich.de 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 CR-Complex NESR FLAIR: (Facility for very Low energy Anti-protons and fully stripped Ions)

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

7 The Central Physics Issue Twist-2 distribution functions f = 1 Spin-average g = 1L - Helicity-difference h = - 1 Helicity-flip

8 Status of knowledge World data on F 1 p World data on g 1 p Transversity, h 1 F 2 +c i (x) SLAC x= x= x= x= (i=20) x= x= x= x= x= NMC BCDMS H preliminary H e + p NLO QCD Fit c i (x)= 0.6 (i(x)-0.4) 10 3 Preliminary 10 2 December 1998 x=0.008 ( x 2048) x=0.015 ( x 1024) x=0.025 ( x 512) x=0.035 ( x 256) x=0.05 ( x 128) x=0.08 ( x 64) Remains still still unmeasured Poorly Poorly modeled x=0.002 x= x=0.125 ( x 32) x=0.005 x=0.175 ( x 16) x=0.008 x=0.013 (i=10) x=0.02 x=0.032 x=0.05 x=0.08 x=0.13 x=0.18 x=0.25 x=0.40 x=0.65 (i=1) Q 2 /GeV 2 g 1 p x=0.25 ( x 8) x=0.35 ( x 4) x=0.5 ( x 2) x=0.75 ( x 1) Q 2 [(GeV/c) ] E155 E143 SMC HERMES EMC A review in: Barone, Drago,Ratcliffe, Phys. Rep. 359 (2002) 1 Well known and well modeled Known, but poorly modeled

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

10 Transversity in Drell-Yan processes PAX: Polarized antiproton beam polarized proton target (both transverse) l + l - q 2 =M 2 q q T p q L p e h (x, M )h (x,m 2 q 2 q 2 q dσ dσ q ATT = â TT dσ + dσ eqq(x1, M )q(x 2,M ) q ) q = u, u,d, d,... M invariant Mass of lepton pair Elementary QED process qq l + l 2 sin θ = cos 2φ 1+ cos θ â TT 2 θ: polar angle of lepton in l + l - rest frame ϕ: azimuthal angle w.r.t. proton polarization

11 A TT in the Drell-Yan production at PAX RHIC: τ=x 1 x 2 =M 2 /s~10-3 Exploration of the sea quark content (polarizations small!) A TT very small (~ 1 %) PAX: M 2 ~10 GeV 2, s~30-50 GeV 2, τ=x 1 x 2 =M 2 /s~ Exploration of valence quarks (h 1q (x,q 2 )large) A TT /a TT > 0.3 Models predict h 1u >> h 1d u 2 u 2 h1 (x1,m )h1 (x1,m ) ATT = â TT 2 2 u(x,m )u(x, M ) (where q p 1 = q p = q) Main contribution to Drell-Yan events at PAX from x 1 ~x 2 ~ τ deduction of x-dependence of h 1u (x,m 2 )! x F =x 1 -x 2 A â TT TT T=15 GeV T=22 GeV Anselmino, Barone, Drago, Nikolaev (hep-ph/ v1)

12 Single Spin Asymmetries Several experiments have observed unexpectedly large single spin asymmetries in pbar-p at large values of x F 0.4 and moderate values of p T (0.7 < p T < 2.0 GeV/c) E704 Tevatron FNAL 200GeV/c π + A N = 1 P beam N N + N N π - Large asymmetries originate from valence quarks: sign of A N related to u and d-quark polarizations x F

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 + 1T P, ST ψ (0) I(0, ξ ) γ ψ ( ξ ) f P, S T DIS DY ( ) ( ) f = f 1T DIS 1T 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 G E -G m separation test of Rosenbluth separation in the time-like region

15 Polarized internal target Target Source Detector Beam Storage Cell Polarimeter Interaction Region point-like 5-10 mm free jet low density cm -2 extended mm storage cell high density cm -2

16 Example: The HERMES target

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

18 The HERMES target Atomic Beam Source NIM A 505, (2003) 633 P z+ = 1> + 4> P z- = 2> + 3>

19 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

20 Target polarization P T = α α 0 rpa + α0(1 α r ) P P T = total target polarization α 0 =atomic fraction in absence of recombination α r =atomic fraction surviving recombination P a = polarization of atoms P m = polarization of recombined molecules Relation to measured quantities: Sampling corrections α r = c α α r TGA P a = c P P a BRP m

21 Target performance Longitudinal Polarization (B=335 mt) Hydrogen Deuterium P t = ± 0.028

22 Target performance Longitudinal Polarization (B=335 mt) Hydrogen Deuterium P t = ± 0.028

23 Target performance Tranverse Polarization (B=297 mt) Hydrogen 0.2 π + HERMES PRELIMINARY not corrected for smearing and acceptance effects 8% scale uncertainty 0.2 π + HERMES PRELIMINARY not corrected for smearing and acceptance effects 8% scale uncertainty sin(φ+φs) A UT 0.1 sin(φ-φs) A UT π - Collins angle 0.2 π - Sivers angle sin(φ+φs) A UT sin(φ-φs) A UT π 0 Maximum possible effect of exclusive vector mesons π 0 Maximum possible effect of exclusive vector mesons P T = ± sin(φ+φs) A UT -0.1 sin(φ-φs) A UT x B z x B z

24 Principle of Spin Filter Method σ tot = σ 0 + σ 1 P Q + σ 2 ( P k)( Q k) = 0, if ( P k ) = 0 P beampol. Q targetpol. k beam For initially equally populated spin states: (m=½) (m=-½) σ tot ± = σ 0 ± σ 1 Q For low energy pp scattering: σ 1 <0 σ tot+ <σ tot- Expectation Target Beam

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

26 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 1 ), 1/τ 1 =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 cm -2 f = MHz Three distinct effects: 1. Selective removal through scattering beyond θ 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 E =-70 mb Horowitz & Meyer, PRL 72, 3981 (1994) H.O. Meyer, PRE 50, 1485 (1994)

27 Spin transfer from electrons to protons r r p + e p + e ( 1+ λ ) p me ν 2α ln( 2pa ) 2 1 4πα 2 0 σe = C0 sin 2 2 p mp 2α ν Horowitz & Meyer, PRL 72, 3981 (1994) H.O. Meyer, PRE 50, 1485 (1994) α λ p =(g-2)/2=1.793 m e,m p p a 0 C 02 =2πη/[exp(2πη)-1] η=-zα/ν v z fine structure constant anomalous magnetic moment rest masses cm momentum Bohr radius Coulomb wave function Coulomb parameter (neg. for anti-protons) relative lab. velocity between p and e beam charge number

28 Beam lifetimes in HESR The lifetime of a stored beam is given by σ C = θ max dσ dω 4 e dω = 2πε m 1 2ψ v 2 θ Ruth. 0 p acc min τ b = ( σ C 1 + σ 0 ) d t f σ0 = σ tot (pp) (Target thickness = d t = atoms/cm 2 ) In order to achieve highest polarization in the antiproton beam, acceptance angles around Ψ acc = 10 mrad are needed. beam lifetime [h] beam lilfetime τ b (h) mrad 8 τ T, τ T, τ T, τ T, mrad T (MeV) 1 T kinetic energy [MeV] 5 mrad Ψ acc = 1 mrad

29 Polarization Build-up up Exploit spin transfer process σ E works also if hadronic polarizing cross sections σ R and σ S turn out to be small N(t)=N 0 exp(-t/τ b ) τ b =(f d t σ L ) -1 I(t)=N(t) f P(t)=1-exp(-t/τ 1 )~ σ E d t f Q t Optimum filtering time: t=2 τ b (from d(p 2 I)/dt=0) P(2τ b )=2 Q (σ E /σ L ) Estimate for σ L from Indiana Cooler σ L = T -2 mb, (Note: σ E ~T -1 ) R.E. Pollock et al., NIM A 330, 380 (1993)

30 Antiproton Polarizer spin-transfer cross section (electrons to antiprotons) Expected Buildup d t = atoms/cm 2 P electron = σ e (mbarn) σ etr ( T) Polarization antiproton Polarization (%) P2( t, 800) P2( t, 500) 6 4 I( t, ) T=500 MeV Goal T=800 MeV T T (MeV) t 3600 beam lifetime [h] t (h) 30

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

32 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) Stored protons: P(n)=P i (η) n η=(99.3±0.1)%

33 Polarimetry Different schemes to determine target and beam polariz. 1. Suitable target polarimeter (Breit-Rabi or Lamb-Shift) to measure target polarization 2. At lower energies ( MeV) analyzing power data from PS172 are available. Therefrom a suitable detector asymmetry can be calibrated effective analyzing power Beam and target analyzing powers are 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 (±8 o 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 Luminosity Physics Performance Spin-filtering for two beam lifetimes: P > 5% N(pbar) = at f r ~ s -1 d t = cm -2 L(t = 0) = 1 10 N p f r d t = cm 2 s 1 Time-averaged luminosity is about factor 3 lower beam loss and duty cycle Experiments with unpolarized beam L factor 10 larger

38 Count rate estimate Uncertainty in A TT depends on target and beam polarization ( P >0.05, Q ~0.9) δ A TT = 1 P Q N 22 N Note: Conservative estimate since hadronic buildup effect might be large as well 240 days T = 15 GeV T = 22 GeV only nonresonant J/Ψ contribution included

39 Extension of the safe region h 1q (x,q 2 ) not confined to safe region M > 4 GeV! qq qq qq J / Ψ γ * e + e unknown vector coupling, but same Lorentz and spinor structure as other two processes Unknown quantities cancel in the ratios for A TT, 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 A TT Anselmino, Barone, Drago, Nikolaev (hep-ph/ v1)

40 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: h 1q (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 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

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

Antiproton-Proton Scattering Experiments with Polarization. PAX Collaboration

Antiproton-Proton Scattering Experiments with Polarization PAX Collaboration www.fz-juelich.de/ikp/pax Spokespersons: Paolo Lenisa lenisa@mail.desy.de Frank Rathmann f.rathmann@fz-juelich.de PAX Collaborators