Antiproton-Proton Scattering Experiments with Polarization

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1 Antiproton-Proton Scattering Experiments with Polarization Frank Rathmann Institut für Kernphysik Forschungszentrum Jülich PAX Collaboration (Polarized Antiproton EXperiments)

2 Outline Introduction Physics Case Transversity SSA Electromagnetic Form Factors Antiproton Polarizer Polarized Internal Target Polarization Buildup Requirements for HESR Detector Concept Forward Spectrometer Large Acceptance Spectrometer Physics Performance Summary Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 2

3 Introduction Past ~10 years, tremendous progress in spin-physics experiments with polarized beams on internal targets Near future: Exploitation at COSY Experimental and theoretical developments pave the way to Future Hadron Physics at GSI Hadronic Probes: IUCF-PINTEX: Proton-Proton Elastic NN NNπ Proton-Deuteron Elastic COSY-EDDA: Proton-Proton Elastic Time-Reversal Invariance COSY-ANKE: Proton-Deuteron Dynamics Neutron-Proton Elastic RHIC-SPIN Electromagnetic Probes: Bates-BLAST Novosibirsk-VEPP-3 HERA-HERMES Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 3

4 Future Facility at GSI HESR Super FRS HESR: High Energy Storage Ring Energy: GeV Length 442 m N = 5 x antiprotons High luminosity - 2 x cm -2 s -1 High resolution - p/p ~ 10-5 (8 MV HE e-cooling) Development of Cooling methods electron and/or stochastic 2MV prototype e-cooler at COSY PANDA: Internal Detector CR Production Target Production rate 10 7 /sec at 30 GeV NESR Letter of Intent: PAX Polarized Antiproton EXperiments ( Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 4

5 Outline Introduction Physics Case Transversity SSA Electromagnetic Form Factors Antiproton Polarizer Polarized Internal Target Polarization Buildup Requirements for HESR Detector Concept Forward Spectrometer Large Acceptance Spectrometer Physics Performance Summary Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 5

6 PAX central physics issue Transversity distribution of the nucleon last leading-twist missing piece of the QCD description of the partonic nucleon structure directly accessible uniquely via the double transverse spin asymmetry A TT in Drell-Yan h 1q (x,q 2 ) of the proton for valence quarks Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 6

R + u L ) u = 1/ 2(u R -u L ) - q(x) helicity difference (known) No probabilistic interpretation (in the helicity

7 Distribution functions Probabilistic interpretation in helicity base: quark proton quark proton f 1 (x) R R 1/2 1/2 + L L 1/2 1/2 q(x) spin averaged (well known) g 1 (x) h 1 (x) new base R R - L L 1/2 1/2 1/2 1/2 R L 1/2-1/2 u = 1/ 2(u R + u L ) u = 1/ 2(u R -u L ) - q(x) helicity difference (known) No probabilistic interpretation (in the helicity base) Transversity base q(x) helicity flip (unknown) Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 7

8 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 Elementary QED process qq l + l 2 sin θ = cos 2φ 1+ cos θ â TT 2 ) q = u, u,d, d,... M invariant Mass of lepton pair θ: polar angle of lepton in l + l - rest frame ϕ: azimuthal angle with respect to proton polarization Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 8

9 Transversity Measurement of A TT also planned at RHIC, but τ=x 1 x 2 =M 2 /s~10-3 Exploration of the sea quark content A TT very small (< 1%) PAX typical kinematics M 2 ~10 GeV 2, s~30-50 GeV 2 τ=x 1 x 2 =M 2 /s~ only valence quarks quarks with large x contribute h 1q (x,q 2 ) large Models predict h 1u >> h 1d u 2 u 2 h1 (x1,m )h1 (x 2, M ) ATT = â TT 2 2 u(x,m )u(x, M ) 1 (where q p 2 = q p = q) A â TT TT T=15 GeV T=22 GeV Anselmino, Barone, Drago, Nikolaev (hep-ph/ March 2004) x F =x 1 -x 2 Main contribution to Drell-Yan events at PAX from x 1 ~x 2 ~ τ deduce x-dependence of h 1u (x,m 2 ) Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 9

10 Extension of the safe region The determination of h 1q (x,q 2 ) is not confined to the 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 Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 10

11 Single Spin Asymmetries E704 Tevatron FNAL 200GeV/c 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) A N (%) π + π - A N = 1 P beam N N + N N x F Large asymmetries originate from valence quarks sign of A N related to u and d-quark polarizations Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 11

12 SSA in Drell-Yan Processes PAX will allow studies of new non-perturbative spin properties of the proton non-vanishing T-odd correlation functions, like the Sivers Function Theoretical Prediction: Collins, PLB 536 (2002) 43 T f = f 1 DY 1T DIS Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 12

13 Proton Electromagnetic Formfactors Measurement of the relative phase of magnetic and electric FF in the time-like region This phase can only be measured via SSA in the annihilation pp e + e - double-spin asymmetry independent G E -G m separation test of the Rosenbluth separation in the time-like region Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 13

14 Outline Introduction Physics Case Transversity SSA Electromagnetic Form Factors Antiproton Polarizer Polarized Internal Target Polarization Buildup Requirements for HESR Detector Concept Forward Spectrometer Large Acceptance Spectrometer Physics Performance Summary Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 14

15 Principle of a polarized internal target (PIT) Target Source Detector Beam Storage Cell Polarimeter point-like 5-10 mm Interaction Region free jet low density cm -2 extended mm storage cell high density cm -2 Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 15

Polarized Atomic Beam Source ABS for ANKE I=7.

16 Polarized Atomic Beam Source ABS for ANKE I= H/s Lamb-Shift Polarimeter Tremendous progress since 1956 ~ 10 6 more atoms/s Luminosity (double polarized) Electron machines: ~10 31 cm -2 s -1 Proton machines: ~10 30 cm -2 s -1 Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 16

17 Features of a PIT Distinct advantages over solid or high pressure targets 1. rapid reversal of target spin (x,y,z): In H/D jet targets up to 100 Hz achieved 2. isotopically pure, no contamination by unpolarized components in the target 3. low background due to absence of container walls 4. no radiation damage, target gas replenished every few ms PIT s are ideally suited for high precision experiments Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 17

18 Principle of Spin Filter Method σ tot = σ 0 + σ 1 P Q For initially equally populated spin states: (m=½) (m=-½) + σ I 2 M MK ( M ) ML = 0, if P k = 0 ( P k ) ( Q k ) σ tot ± = σ 0 P beampol. Q targetpol. k beam ± σ 1 Q For low energy pp scattering: σ 1 <0 σ tot+ <σ tot- Expectation Target Beam Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 18

19 Filter Test at TSR (1992) Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 19

20 Filter Test at TSR with protons Experimental Setup Results T=23 MeV F. Rathmann. et al., PRL 71, 1379 (1993) Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 20

21 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 Q d 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 Meyer and Horowitz identified three distinct effects to explain exactly the observed build-up! 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 =-70 mb σ E Horowitz & Meyer, PRL 72, 3981 (1994) H.O. Meyer, PRE 50, 1485 (1994) Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 21

22 Polarization Build-up up PAX will exploit spin transfer process σ E works also if hadronic polarizing cross sections σ and σ R 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 (t << τ 1 ) Optimum filtering time t=2 τ b (from d(p 2 I)/dt=0) P(2τ b )=2 Q (σ E /σ L ) Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 22

23 Spin transfer from electrons to protons 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 2 0 =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 (negative for anti-protons) relative lab. velocity between p and e beam charge number Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 23

24 Antiproton Polarizer Expected Buildup spin-transfer cross section (electrons to antiprotons) d t = atoms/cm 2 P electron = 0.9 σ e (mbarn) σ etr ( T) antiproton Polarization (%) 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 Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 24

25 Constraints on the HESR Machine Design A storage cell target requires a small β-function at the interaction point: σ beam ~β ½ d I L d t ~ I LI 2 d -3 T -½ ~ I LI 2 β -3/2 beam 3/2 T -½ low-β section Typical values β (m) d t (cm -2 ) Q TSR 1.05 ± IUCF 0.98 (x),1.71 (y) HERA ~ Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 25

26 Beam lifetimes in HESR The lifetime of a stored beam τ b = ( σ The coulomb loss σ C = = θ θ max min σ0 = σ tot C 1 + σ dσ dω 4 e 2πε m 0 2 p (pp) 0 ) d 1 2ψ t f In order to achieve highest polarization in the antiproton beam, acceptance angles around Ψ acc = 10 mrad are needed. v Ruth. 4 dω 2 acc 1 2 beam lilfetime τ b (h) beam lifetime [h] τ T2010, 3 6 τ T1010, 3 τ T510, 3 τ T110, mrad 10 mrad 5 mrad Calculation assumes a target thickness of d t = atoms/cm 2 Ψ acc = 1 mrad T kinetic energy 1200 [MeV] T (MeV) Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 26

27 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! Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 27

28 Polarization Export calibrated Export polarization from a beam energy, where it is calibrated Possible only with a stored beam unknown time COSY-ANKE Method employed for pd-breakup Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 28

29 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)% Ferrite Rf-dipole higher Bdl=0.58 T mm stored deuterons flipped also efficiency η>0.9 Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 29

30 Polarimetry PAX will employ different schemes to determine beam and target polarization: 1. A suitable target polarimeter (Breit-Rabi or Lamb-Shift) allows one to determine the 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 Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 30

31 Outline Introduction Physics Case Transversity SSA Electromagnetic Form Factors Antiproton Polarizer Polarized Internal Target Polarization Buildup Requirements for HESR Detector Concept Forward Spectrometer Large Acceptance Spectrometer Physics Performance Summary Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 31

32 Detector Concept Two complementary parts: 1. Forward Detector 2. Central Large Acceptance Detector Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 32

33 Forward Detector (HERMES-like) ±8 0 acceptance unambiguous identification of leading particles precise measurement of their momenta Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 33

34 Large Acceptance Detector (φ-symmetric( symmetric) measurement of angles (θ,φ) and energies of electromagnetic particles (Drell-Yan pairs) Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 34

35 Outline Introduction Physics Case Transversity SSA Electromagnetic Form Factors Antiproton Polarizer Polarized Internal Target Polarization Buildup Requirements for HESR Detector Concept Forward Spectrometer Large Acceptance Spectrometer Physics Performance Summary Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 35

36 Physics Performance Luminosity 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 For experiments with unpolarized beam on polarized target, L ~ factor 10 larger Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 36

37 Count rate estimate Uncertainty of Double-spin asymmetry A TT depends on polarization of beam and target ( P >0.05, Q ~0.9) δ A TT = 1 P Q N 22 N Note: Conservative estimate since hadronic buildup effect may be large 240 days T = 15 GeV T = 22 GeV only nonresonant J/Ψ contribution included Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 37

38 Summary 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 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 polarization build-up Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 38

39 PAX: The next steps 2004 LOI on its way! Formation of an advisory committee at GSI in progress Evaluation of LOI s available within a couple of weeks If approved: Technical Report (with Milestones) by followed by evaluations and green light for construction Technical Design Reports (for the Milestones) Commissioning of HESR Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 39

40 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 Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 40

41 (continued) Nicola Bianchi, Enzo De Sanctis, Pasquale Di Nezza, Delia Hasch, Valeria Muccifora, Karapet Oganessyan, and Patrizia Rossi Instituto Nationale di Fisica Nucleare, Frascati, Italy 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 Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 41

42 (continued) 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 + new Collaborators welcome Total: Spokespersons: Paolo Lenisa Frank Rathmann 17 Institutions 116 members lenisa@mail.desy.de f.rathmann@fz-juelich.de Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 42

43 Final Remark Polarization data has often been the graveyard of fashionable theories. If theorists had their way, they might just ban such measurements altogether out of self-protection. J.D. Bjorken St. Croix, 1987 Frank Rathmann Indo-German Workshop (Delhi, India, March 16, 2004) 43

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