Folie 1 Many exciting old ideas with antiprotons, pre LEAR Revival for FAIR / FLAIR Trap experiments active at AD/CERN pp →YY with S = ±1, ±2, ±3 (possibly YY atomic effects) CP violation test: α Λ – α Λ = 0 Compare decay asymmetry of Λ and Λ ELENA: cooled p beams down to 100keV (best stop experim.) Walter Oelert S=-2 hadronic states (B=1, 2, 3,…) via p stop. Recoilless! Highest precision p stop and coincident channeling (dynamic unit cell tomography) Annihilat. dynamics p+ 9 Be→{αα} 380keV Breeding of cooled d beams in double ring collider. Max. rate, max. quality Production of polarised p with filter method in cooler ring …and more Ideas get lost after a scientific lifetime

Mitglied der Helmholtz-Gemeinschaft Production of antiprotons Spin filter method Antihyperon decay Polarised production Comparison Ways to make polarised antiproton beams Dieter Grzonka, Kurt Kilian, Walter Oelert, IKP FZ-Jülich MESON – Krakow Monday

Folie 3 Production of antiprotons Convert collision energy into particle- antiparticle pairs energy → p + p (in 3 S 1- ?) Quasifree production p + p → p + (3p) 0<ε<max Symmetric in cm system At 26 GeV/c beam 0 < ε <3360 MeV 2914 MeV/c > p cm > 0 If p cm < 150 MeV/c then S wave production D. Dekkers CERN PS 1968 K. Kilian et al.1977 pre LEAR memo to PSCC 26 GeV/c beam

Folie 4 pp→p+(3p) Assumption of quasifree nucleon-nucleon interaction is reasonable. Simple kinematical situation At maximum (3.65 GeV/c) antiprotons are collected, cooled and piled up in storage synchrotrons. From there extremely dense beams are delivered. At CERN (26 GeV) one gets one useful antiproton from 10 6 beam protons Average p flux I 0 = 10 7 s -1 p lab. Momentum MC simulation

Folie 5 Spin filter method Suggested for the future ISR: P.L.Csonka, Nucl. Instr. Meth. 63 (1968) 247 If singlet and triplet cross sections are different, then an internal polarised target depletes one of the stored spin components faster than the other. Polarisation rises on the expense of intensity. σ = σ H + Δσ Cb Spin filtering for polarised antiprotons works only with cooling avoids beam blow up and losses by multiple scattering K.Kilian 1980, Pol. Conf. Lausanne, K.Kilian & D.Moehl 1982, Erice LEAR workshop Filtering below 1 GeV/c → Important Δσ Cb

Folie 6 Spin-filtering at TSR: „FILTEX“ – proof-of- principle → Spin filtering works for protons F. Rathmann et al., PRL 71, 1379 (1993) 6Spin-filtering studies at COSY and ADFrank Rathmann PAX submitted new proposal to find out how well spin filtering works for antiprotons: Measurement of the Spin-Dependence of the pp Interaction at the AD Ring (CERN-SPSC / SPSC-P-337)

Folie 7 Frank RathmannSpin-filtering studies at COSY and AD7 of 19 statistical error of a double polarization observable (A TT ) Measuring time t to achieve a certain error δ ATT t ~ FOM = P 2 ·I Polarization Buildup: Figure of Merit (N ~ I) Optimum time for Polarization Buildup given by maximum of FOM(t) t filter = 2·τ beam t/τ beam I/I Beam Polarization P2ΤP2Τ σ↑↑ : σ↓↑P2ΤP2Τ 1 : 0.521% 1 : 0.87% Δσ Cb → will dilute effect 2T > 4 days ? Ask F.R. Other spin dependent processes? E.g. B. Schoch: scatter polarised photons

Folie 8 Λ → p + π + p p lab (p) p cm π+π+ p lab (π + ) Antihyperon decay Decay makes p with helicity h = Lorentz boost creates transverse vector polarisation. First and so far only experiment with polarised 200 GeV p at Fermilab. Λ production with primary proton beam. At the end an average of 10 4 polarised p s -1 A. Bravar et al. Phys. Rev. Lett. 77, 2626 (1996) Decay momentum in cm syst. is 101 MeV/c

Folie 9 FNAL experiment: A. Bravar et al. P.R.L.77,2626,(1996) NB: decay polarisation tagging below 0.5 mrad ! Experiment ~ km long

Folie 10 Useful antihyperon source in the GeV range (FAIR) pp → ΛΛ → pπ + pπ - Decay direction of the hyperon defines the polarisation direction of the baryon. The two decay V are tags and spectrometers for each other Most important is geometrical reconstruction of all tracks Will not work with internal target (miserable multi track reconstruction, miserable trigger condition) Branching ratio σ ΛΛ /σ tot = cτ Λ = 7.89 cm

Folie 11 Active sandwich target, tracker, baryon number identifier pp target efficiency ~ Insert a flat target for p secondary scattering (done for Λ and Λ scattering)

Folie 12 CP violation test P. D. Barnes et al., PR C (1996) 10 5 pair events (at and GeV/c) [ A ] = ± (most precise so far) 100 times smaller error allows relevant CP test Needs 10 9 pair events or 2x10 14 beam p (200 days) As byproduct: “beam” of 10 9 polarised decay p A = (α Λ + α Λ ) / (α Λ - α Λ ) = 0 ΛΛ production >95% triplet

Folie 13 Use the antiproton factory (nearly) as usual. Cut out kinematical regions in the antiproton production spectrum which would dilute vector polarisation Avoid pure s wave antiprotons Cut one side in the horizontal angular distribution Cut up and down angles In addition avoid depolarisation in the cooler synchrotron Polarised production

Folie 14 y x

Folie 15 Red lines: angular and momentum acceptance of AD S wave region

Folie 16 y x

Folie 17 Clean cuts may need a “pointlike” source, means a shorter production target Reduction 1/5 Cuts in kinematics Reduction 1/5 I/I 0 ~ 1/25

Folie 18 p production and transport to AD - Necessary cuts in p distribution easily made in the existing beam line

Folie 19 Existing AD for p stop experiments Acceptance H, V (π mm mrad)200/180 Acceptance Δp/p (%)±3.2% Number of p injected per cycle

Folie 20 AD tune diagram and Limit of spin stability (red lines)

Folie 21 CNI polarimeter reaction (coulomb-nuclear interference) allows to check if polarised p come out A = 4.5% maximum at t = (GeV/c) 2 corresponds to 38 mrad for p+p scattering at 3.5 GeV/c Polarisation test at CERN PS Cu (lH 2 ) target on external beam 1.5 Tm dipole, 10 cm gap Straw tracker stacks before and after an lH 2 analyser target on the p exit side. Adapted to 3.3 to 3.7 GeV/c p Trigger szintillators All in vacuum (Target and detectors exist at COSY TOF) A 2mb polarim. react.

Folie 22 Measurement of antiproton polarisation detector components in vacuum 1 m P T < 150 MeV/c ( s-wave ) P T < 700 MeV/c AD acceptance straw tubes ( track resolution ~ 100 μm ) Cerenkov detector n=1.03 liquid hydrogen analyser target 24 GeV/c proton beam antiproton production target 1 cm W dipole magnet 1.6 T 38 mrad scintillator hodoscope P = 3.4 – 3.6 GeV/c beam dump 2% precision in p polarisation with 4 10^16 primary protons on 8mm W target

Folie 23 Comparison Filter methode Λ decay Polarised production P0 – 40% ??>45% !0 - 40% ?? I/I – ?10 -3 x x.2 ~ x 0.2 ~ P 2 I< < T 0 ~ 2 days (hadronic) Reduced duty factor ? Polarisation dependence of filter reactions ? (not spin transfer) Sibirian snake needed Proof with protons ok External target for Λ production Decay spectrometer and –polarimeter Pol. p scattering parasitic with CP test? Has been used (FNAL) Numbers are known Is there p polarisation? Test experiment on external PS beam Would be by far simplest solution

Folie 24 Comparison Filter methode Λ decay Polarised production P0 – 40% ??>45% !0 - 40% ?? I/I – ?10 -3 x x.2 ~ x 0.2 ~ P 2 I< < T 0 ~ 2 days (hadronic) Reduced duty factor ? Polarisation dependence of filter reactions ? (not spin transfer) Sibirian snake needed Proof with protons ok External target for Λ production Decay spectrometer and –polarimeter Pol. p scattering parasitic with CP test? Has been used (FNAL) Numbers are known Is there p polarisation? Test experiment on external PS beam If p not polarised, use polarised 26 GeV proton beam Would be by far simplest solution

Folie 25 Thank you for your attention

Folie 26 polarisation dependent interactions Spin filter idea with cooling (K. Kilian & D. Moehl 1980 Lausanne Pol. Conf., 1982 Erice LEAR workshop) Stimulated activities. Most successful: E. Steffens and the FILTEX collaboration at the TSR in MPI Heidelberg. Proof that it works with protons. F. Rathmann PRL (1993) Idea of spin transfer at very low energy e↑ + p → e + p↑ in beam – beam interaction. PAX collaboration at COSY showed that there is no effect D. Oellers et al. Phys. Lett. B674 (2009) 269 Certainly polarisation dependent is interaction of circularly polarised photons with p γ + p → n + π B. Schoch, EPJ 2010

Folie 27 Intensity loss - polarisation gain - FOM With a storage cell target ( pol. prot. cm -2 ) T 0 ~ 2 days (hadronic) K.K. & D.M. Erice 1982

Folie 28 Geometry spectrometer (PS185 at LEAR) A stack of 23 wire chambers Decay spectrometer and polarimeter with full acceptance and very high precision