http www fzjuelich deikppax dr Paolo Lenisa Universit

http: //www. fz-juelich. de/ikp/pax dr. Paolo Lenisa Università di Ferrara and INFN - ITALY DIS 2005 XIII International Workshop on Deep Inelastic Scattering Madison, April 29 th 2005 PAX experiment PAX: Polarized Antiproton Experiments 1

PAX Collaboration Spokespersons: Paolo Lenisa Frank Rathmann lenisa@mail. desy. de f. rathmann@fz-juelich. de 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 Gb. R, Germany Department of Mathematics, University of 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 experiment PAX: Polarized Antiproton Experiments 2

PAX Collaboration 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 experiment PAX: Polarized Antiproton Experiments 3

PAX: Polarized Antiproton Experiments WHY? Outline Physics Case HOW? Polarized Antiprotons WHAT? Staging estimate WHERE AND WHEN? (D) PAX experiment Detector and signal The FAIR project at GSI 4

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 ATT in the Drell-Yan production of lepton pairs – theoretical expectations for ATT 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 PAX experiment Physics Polarization Staging Signals FAIR 5

Transversity Properties: - Probes relativistic nature of quarks No gluon analog for spin-1/2 nucleon Different evolution than Sensitive to valence quark polarization Chiral-odd: requires another chiral-odd partner Impossible in DIS PAX experiment p p l+l-X ep e’h X Direct Measurement Indirect Measurement: Convolution of with unknown fragment. fct. Physics Polarization Staging Signals FAIR 6

Transversity in Drell-Yan processes PAX: Polarized antiproton beam → polarized proton target (both transverse) l+ q p q. L l- q 2=M 2 q. T p M invariant Mass of lepton pair PAX experiment Physics Polarization Staging Signals FAIR 7

Other Topics • • PAX experiment 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 8

PAX: Polarized Antiproton Experiments WHY? Outline Physics Case HOW? Polarized Antiprotons WHAT? Staging estimate WHERE AND WHEN? (D) PAX experiment Detector and signal The FAIR project at GSI 9

Polarized internal target point-like 5 -10 mm free jet low density 1012 cm-2 extended 200 -500 mm storage cell high density 1014 cm-2 PAX experiment Physics Polarization Staging Signals FAIR 10

Performance of Polarized Internal Targets HERMES: Stored Positrons Dz Longitudinal Field (B=335 m. T) PT = 0. 845 ± 0. 028 HERMES H PINTEX: Stored Protons Dzz H Fast reorientation in a weak field (x, y, z) Transverse Field (B=297 m. T) PT = 0. 795 0. 033 HERMES Targets work very reliably (months of stable operation) PAX experiment Physics Polarization Staging Signals FAIR 11

Principle of spin filter method σtot = σ0 + σ ·P·Q + σ||·(P·k)(Q·k) P beam polarization Q target polarization k || beam direction For initially equally populated spin states: (m=+½) and (m=-½) transverse case: longitudinal case: Unpolarized anti-p beam Polarized H target PAX experiment Physics Polarization Staging Signals FAIR 12

Principle of spin filter method σtot = σ0 + σ ·P·Q + σ||·(P·k)(Q·k) P beam polarization Q target polarization k || beam direction For initially equally populated spin states: (m=+½) and (m=-½) transverse case: longitudinal case: Polarized Unpolarized anti-p beam Polarized H target PAX experiment Physics Polarization Staging Signals FAIR 13

Principle of spin filter method σtot = σ0 + σ ·P·Q + σ||·(P·k)(Q·k) P beam polarization Q target polarization k || beam direction For initially equally populated spin states: (m=+½) and (m=-½) transverse case: For low energy pp scattering: 1<0 tot+< tot- PAX experiment Physics Polarization Staging longitudinal case: Expectation Target Beam Signals FAIR 14

Experimental Setup at TSR (1992) PAX experiment Physics Polarization Staging Signals FAIR 15

1992 Filter Test at TSR with protons Results Experimental Setup T=23 Me. V F. Rathmann. et al. , PRL 71, 1379 (1993) PAX experiment Physics Polarization Staging Signals FAIR 16

Spin transfer from electrons to protons Horowitz & Meyer, PRL 72, 3981 (1994) H. O. Meyer, PRE 50, 1485 (1994) α λp=(g-2)/2=1. 793 me, mp 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 (negative for antiprotons) relative lab. velocity between p and e beam charge number PAX will exploit spin-transfer from polarized electrons of the target to antiprotons PAX experiment Physics Polarization Staging Signals FAIR 17

Spin Transfer Cross Section EM (mbarn) 100 10 1 10 PAX experiment 1000 Physics Polarization Staging T (Me. V) Signals FAIR 18

Beam lifetimes in the APR Beam Lifetime Coulomb Loss beam lilfetime τbeam (h) Total Hadronic ψacc(mrad) 40 10 8 6 30 25 20 10 4 2 10 PAX experiment 100 Physics Polarization Staging 1000 Signals FAIR T (Me. V) 19

Polarization Buildup: optimal polarization time Beam Polarization Optimimum time for Polarization Buildup given by maximum of FOM(t) tfilter = 2·τbeam Measuring time t to achieve a certain error δATT ~ FOM = P 2·I (N ~ I) I/I 0 statistical error of a double polarization observable (ATT) 0. 8 0. 6 0. 4 0. 2 0 PAX experiment Physics Polarization Staging 2 4 Signals FAIR 6 t/τbeam 20

Optimum Beam Energies for Buildup in APR Maximum FOM ψacc= 50 mrad AP Space charge limit 15 40 mrad 10 Ψacc (mrad) Τbeam (h) P(2·τbeam) T (Me. V) 10 1. 2 0. 19 163 20 2. 2 0. 29 88 30 4. 6 0. 35 61 40 9. 2 0. 39 47 50 16. 7 0. 42 38 F. Rathmann et al. , Phys. Rev. Lett. 94, 014801 (2005) 5 30 mrad 20 mrad 10 1 PAX experiment 100 Physics Polarization Staging 10 mrad Signals FAIR T (Me. V) 21

Beam Polarization P(2·τbeam) Beam Polarization Ψacc=50 mrad 0. 4 40 0. 3 EM only 30 20 10 0. 2 5 0. 1 0 1 10 100 T (Me. V) Filter Test: T = 23 Me. V Ψacc= 4. 4 mrad PAX experiment Physics Polarization Staging Signals FAIR 22

Antiproton Polarizer Ring (APR) Mechansim: spin transfer from electrons to protons Injection B ex, y: Siberian Snake e-cooler ABS APR 100 m Polarizer Target PAX experiment RING PARAMETERS: Energy: 50 Me. V (p~300 Me. V/c) 500 p mm mrad Circumeference: 100 m No. Particles: 1012 EQUIPMENT: Polarized target e-cooler Snake e-cool Stochastic cooling? PROJECTION: P > 30% after 18 -20 hrs (1011 pbar) Physics Polarization Staging Signals FAIR 23

PAX: Polarized Antiproton Experiments WHY? Outline Physics Case HOW? Polarized Antiprotons WHAT? Staging estimate WHERE AND WHEN? (D) PAX experiment Detector and signal The FAIR project at GSI 24

Staging: Phase I (PAX@CSR) Physics: Experiment: EMFF pbar-p elastic pol. /unpol. Pbar (3. 5 Ge. V/c) on int. pol. target Independent from HESR running PAX experiment Physics Polarization Staging Signals FAIR 25

Staging: Phase II (PAX@HESR) Physics: Transversity EXPERIMENT: 1. Asymmetric collider: polarized antiprotons in HESR (p=15 Ge. V/c) polarized protons in CSR (p=3. 5 Ge. V/c) 2. Internal polarized target with 22 Ge. V/c polarized antiproton beam. Second IP with minor interference with PANDA PAX experiment Physics Polarization Staging Signals FAIR 26

PAX: Polarized Antiproton Experiments WHY? Outline Physics Case HOW? Polarized Antiprotons WHAT? Staging estimate WHERE AND WHEN? (D) PAX experiment Detector and signal The FAIR project at GSI 27

Transversity in Drell-Yan processes PAX: Polarized antiproton beam → polarized proton target (both transverse) l+ q p q. L l- q 2=M 2 q. T p M invariant Mass of lepton pair PAX experiment Physics Polarization Staging Signals FAIR 28

ATT for PAX kinematic conditions RHIC: τ=x 1 x 2=M 2/s~10 -3 → Exploration of the sea quark content (polarizations small!) ATT very small (~ 1 %) PAX: M 2~10 -100 Ge. V 2, s~45 -200 Ge. V 2, τ =x 1 x 2=M 2/s~0. 05 -0. 6 → Exploration of valence quarks (h 1 q(x, Q 2) large) ATT/a. TT > 0. 2 Models predict |h 1 u|>>|h 1 d| PAX experiment Physics Polarization Staging Signals FAIR 29

Kinematics and cross section • M 2 = s x 1 x 2 • x. F=2 QL/√s = x 1 -x 2 2 k events/day collider 22 Ge. V M (Ge. V/c 2) Estimated luminosities: • Fixed target: 2. 7 x 1031 cm-2 s-1 • Collider: 1 -2 x 1030 cm-2 s-1 PAX experiment Physics Polarization Staging Signals FAIR 30

ATT asymmetry: angular distribution • Asymmetry is largest for angles • Asymmetry varies like cos(2 f). =90° Needs a large acceptance detector (LAD) PAX experiment Physics Polarization Staging Signals FAIR 31

PAX detector concept GEANT simulation (200 mm) Cerenkov (20 mm) Designed for Collider but compatible with fixed target PAX experiment Physics Polarization Staging Signals FAIR 32

Estimated signal for h 1 (phase II) 1 year of data taking Collider: Fixed target: L=2 x 1030 cm-2 s-1 L=2. 7 x 1031 cm-2 s-1 PAX experiment Physics Polarization Staging Signals FAIR 33

PAX: Polarized Antiproton Experiments WHY? Outline Physics Case HOW? Polarized Antiprotons WHAT? Staging estimate WHERE AND WHEN? (D) PAX experiment Detector and signal The FAIR project at GSI 34

Faciltiy for Antiproton and Ion Research (GSI, Darmstadt, Germany) -Proton linac (injector) -2 synchrotons (30 Ge. V p) -A number of storage rings Parallel beams operation PAX experiment Physics Polarization Staging Signals FAIR 35

The FAIR project at GSI SIS 100/300 50 Me. V Proton Linac HESR: High Energy Storage Ring: PANDA and PAX CR-Complex NESR PAX experiment Physics Polarization Staging FLAIR: (Facility for very Low energy Antiprotons and fully stripped Ions) Signals FAIR 36

Timeline Phase 0: 2005 -2012 APR design and construction @ Juelich Phase I: 2013 -2017 APR+CSR @ GSI Physics: EMFF with fixed target Phase II: 2018 - … HESR+CSR asymmetric collider Physics: h 1 PAX experiment Physics Polarization Staging Signals FAIR 37

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 experiments: • Pbeam > 0. 30 • L> 1. 6 · 1030 cm-2 s-1 (Collider), L 2. 7 · 1031 cm-2 s-1(fixed target) Detector concept: • Large acceptance detector with a toroidal magnet PAX experiment 38

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” PAX experiment 39