1 dr. Paolo Lenisa Università di Ferrara and INFN – ITALY on behalf of the PAX-Collaboration Perspectives for Polarized Antiprotons Polarized Antiprotons P.Lenisa XIV International Workshop on Polarized Sources, Targets and Polarimetry St. Petersburg,

Motivation: Missing tool for Hadron Physics 2 Polarized Antiprotons P.Lenisa Polarized Antiprotons

3 transversely polarised quarks and nucleons longitudinally polarised quarks and nucleons unpolarised quarks and nucleons Quark structure of the nucleon P.Lenisa Well known Known Less known

Polarized Antiprotons 4 Inclusive DIS Semi-inclusive DIS Drell-Yan HERMES,COMPASS,JLab transversely polarised quarks and nucleons longitudinally polarised quarks and nucleons unpolarised quarks and nucleons Quark structure of the nucleon P.Lenisa

Accesso to transversity through Drell-Yan 5 Polarized Antiprotons P.Lenisa

Asymmetric (double-polarized) proton (15 GeV/c) – antiproton (3.5 GeV/c) collider 6 p p A double polarized pbar-p collider for FAIR Polarized Antiprotons P.Lenisa

7 1 year run -> 10 % precision on the h 1 u (x) in the valence region P p =30% P p =10% Polarized Antiprotons P.Lenisa h 1u from p  -p  Drell-Yan at PAX u-dominance |h 1u |>|h 1d |

Polarized Antiprotons 8 Polarization Rosenbluth Space-Like FFs: proton data Study of the Proton Electromagnetic Form-Factors JLab results dramatically changed picture of the Nucleon: - G E p /G M p decreases with Q 2 - data suggest G E p crosses 0 at Q 2  8 GeV 2 Time-Like FFs: proton data Expected Q 2 behaviour reached quite early, however there is still a factor of 2 between timelike and spacelike. Additional and more precise measurements needed P.Lenisa

9 Most contain moduli G E, G M Independent G E -G M separation Test of Rosenbluth separation in the time-like region Access to G E -G M phase Very sensitive to different models Double polarized pbar-p annihilation: E. Tomasi, F. Lacroix, C. Duterte, G.I. Gakh, EPJA 24, 419(2005) Polarized Antiprotons P.Lenisa

10 Polarization and Models in T.L. Region VDM : IJL Ext. VDM ‘QCD inspired’ R AyAy A xx A yy A xz A zz E. Tomasi, F. Lacroix, C. Duterte, G.I. Gakh, EPJA 24, 419(2005) Polarized Antiprotons P.Lenisa

Method: The mechanism of spin-filtering 11 Polarized Antiprotons P.Lenisa Polarized Antiprotons

P. Lenisa PAX Status Report 12 Polarized antiprotons Intense beam of polarized pbar never produced: Synchr. radiation ~  (  4 /R) ->  pol ~10 7 y in 20 TeV pbar ring Conventional methods (ABS) not applicable Polarized pbar from antilambda decay I< 1.5∙10 5 s -1 (P ≈ 0.35) Pbar scattering off liquid H 2 target I< 2∙10 3 s -1 (P ≈ 0.2)

Production of polarization in a stored beam Two Methods: Loss versus spin flip For an ensemble of spin ½ particles with projections + (  ) and – (  ) 13 Polarized Antiprotons P.Lenisa

Spin-filtering 14P.Lenisa Polarization build-up of a circulating particle beam by interaction with a polarized gas target Polarization build-up of a circulating particle beam by interaction with a polarized gas target Polarized Antiprotons

Unpolarized anti-p beam Polarized target Polarization Buildup P.Lenisa15 S beam-particle spin Q target polarization k || beam direction S beam-particle spin Q target polarization k || beam direction Polarized Antiprotons

Unpolarized anti-p beam Polarized target Polarized anti-p beam P.Lenisa16 Polarization Buildup S beam-particle spin Q target polarization k || beam direction S beam-particle spin Q target polarization k || beam direction Polarized Antiprotons Optimum (black curve) after 2 lifetimes filtering Optimum (black curve) after 2 lifetimes filtering

Spin-filtering at TSR: „FILTEX“ – proof-of-principle Spin filtering works for protons F. Rathmann et al., PRL 71, 1379 (1993) 17 PAX submitted new proposal to find out how well does spin filtering work for antiprotons Measurement of the Spin-Dependence of the pp Interaction at the AD Ring (CERN-SPSC / SPSC-P-337) Polarized Antiprotons P.Lenisa

Antiproton polarization : Proton polarization Eexperiments with pol. pbar P.Lenisa 18 Polarized Antiprotons Experimental program: Measurements with pbar at AD-Ring

P.Lenisa19 PAX target section Measurements at AD (CERN) Aim: 1 st measurement of the spin-dependence of the pbar-p cross section Method: measurement of polarization build-up by spin-filtering Polarized Antiprotons

Spin-dependence of the pbar-p interaction P.Lenisa20 Model A: T. Hippchen et al., Phys. Rev. C 44, 1323 (1991). Model OBEPF: J. Haidenbauer, K. Holinde, A.W. Thomas, Phys. Rev. C 45, 952 (1992). Model D: V. Mull, K. Holinde, Phys. Rev. C 51, 2360 (1995). Polarized Antiprotons

Expected polarizations after filtering for two lifetimes transverse A D 21 longitudinal Polarized Antiprotons P.Lenisa Measurement of the polarization buildup allows determination of σ 1 and σ 2 Once pbar polarization available, spin-correlation coefficients accessible

Polarized Antiprotons 22 More recent calculations… PLB 690 (2010) P.Lenisa Cross sections Projected polarizations

Antiproton polarization : Proton polarization Experiments with pol. pbar P.Lenisa 23 Polarized Antiprotons Experimental program Measurements with p at COSY-Ring (Germany)

WASA e-cooler ANKE PAX Spin-filtering at COSY Main purpose: 1. Commissioning of the experimental setup for CERN/AD 2. Quantitative understanding of the machine parameters Main purpose: 1. Commissioning of the experimental setup for CERN/AD 2. Quantitative understanding of the machine parameters P.Lenisa 24 Polarized Antiprotons

Installation of low-β section (2009) Beam has to fit through storage cell target (d t =5x10 13 atoms/cm 2 ) Increase acceptance angle at target position P.Lenisa 25 Polarized Antiprotons

Model in good agreement with measurement: β ~ 0.3m -> beam fits through the cell! Model in good agreement with measurement: β ~ 0.3m -> beam fits through the cell! No negative impact on the COSY operation Commissioning of the experimental setup (2010) I. Machine studies: Low-  section P.Lenisa 26 Polarized Antiprotons

In case intra-beam scattering poses a limitation, increase of beam emittance should increase lifetime! (Touschek) Increase of beam emittance by tilting of electron cooler beam Beam emittance measured with ionisation profle monitor P.Lenisa 27 Polarized Antiprotons Commissioning of the experimental setup (2010) I. Machine studies: Studies of beam-lifetime limitations

ABS Breit-Rabi polarimeter Breit-Rabi polarimeter  Spin filtering requires >10 13 atoms/cm 2 → ABS + openable storage cell  Analysis of target polarization by Breit-Rabi polarimeter (BRP) and a target gas analyzer (TGA)  Spin filtering requires >10 13 atoms/cm 2 → ABS + openable storage cell  Analysis of target polarization by Breit-Rabi polarimeter (BRP) and a target gas analyzer (TGA) Commissioning of the experimental setup (2010) II. Polarized Target P.Lenisa 28 Polarized Antiprotons

P.Lenisa Polarized Antiprotons 29 BRP: Continous monitoring of the target polarization

p D2D2 pd elastic scattering: detection in two (L-R) symmetric Silicon Tracking Telescopes Commissioning of the experimental setup (2010) III. Beam Polarimeter P.Lenisa 30 Polarized Antiprotons Deuteron identification d p

P.Lenisa Polarized Antiprotons 31 Commissioning of the experimental setup (Aug. 2011) IV. Installation of NEG pump (12000 l/s)

In an ideal machine Single-Coulomb scattering at the target dominates beam loss COSY beam movable frame system Beam size Acceptance angle September 2011 ongoing beamtime: I Measurement of ring acceptance P.Lenisa 32 Polarized Antiprotons

September 2011 ongoing beamtime: II Ring polarization studies P.Lenisa 33 Polarized Antiprotons I.Measurement of polarization lifetime:  P >10 5 s II.Measurement of spin-flip efficiency:  =0.987

Spin-filtering cycle P.Lenisa 34 Polarized Antiprotons Polarization dP/dt  0.18%/h Cycle COSY measurement

P.Lenisa Polarized Antiprotons 35 To be continued …. Ferrara - Castello Estense Sebastiano Filippi: “The spinning top game" – XVI cent.

Additional slides P.Lenisa 36 Polarized Antiprotons

pp interaction models P.Lenisa 37 Polarized Antiprotons

Nuclear polarization of the hydrogen target determined with the Breit-Rabi polarimeter after opening and closing of the storage cell a few times closed open 0penable storage cell Atomic beam source provides polarized hydrogen target Storage cell target to reach d t =5x10 13 atoms/cm 2 P.Lenisa 38 Polarized Antiprotons

Polarisation buildup cross sections Folie 34

Polarized Antiprotons 40 Polarized antiprotons on fixed target (PAX-Phase I) EXPERIMENT: Fixed target experiment: polarized antiprotons protons in CSR (p>200 MeV/c) fixed polarized protons target P.Lenisa