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The PAX experiment

The PAX experiment. Paolo Lenisa Università di Ferrara and INFN - Italy. Tbilisi , July 10 th 2014. Motivation. The PAX collaboration proposed to investigate Drell Yan processes in scattering of polarized proton - antiproton beams at the HESR (FAIR ).

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The PAX experiment

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  1. The PAX experiment Paolo Lenisa Università di Ferrara and INFN - Italy Tbilisi, July 10th 2014 PAX - Polarized Antiprotons

  2. Motivation The PAX collaborationproposedtoinvestigateDrellYan processes in scatteringofpolarizedproton- antiprotonbeamsatthe HESR (FAIR). Annihilation ofvalencequarkwithan antivalencequarkallowsdirectaccess to: transversity, …. Requirements: Polarizedprotonbeam Polarizedantiprotonbeam PAX - Polarized Antiprotons

  3. A polarized Proton-AntiprotonColliderat FAIR polarizedantiprotons in HESR (p=15 GeV/c) polarizedprotons in CSR (p=3.5 GeV/c) direction of protons direction of anti-protons PAX - Polarized Antiprotons

  4. HowtoPolarizeAntiprotons? Spin-1/2 particles 2 states selectiveflip selectiveremoval polarized unpolarized unpolarized polarized • Does not affectintensity • Reduces beam intensity PAX - Polarized Antiprotons

  5. Selective-flip: a proposal Eur. Phys. J. A 34, 447 (2007) PAX - Polarized Antiprotons

  6. Spin-flip studies at COSY (in I3HP2) • Use protonbeam and co-moving electrons • Turn experiment around: p e → p e into p e → p e • i.e. observe depolarization of a polarized proton beam Velocity mismatch COSYelectron cooler(detuned) PAX - Polarized Antiprotons

  7. Spin-flip: results Nominal protonenergy in electronrestframe (keV) 0 1 2 3 σ║ < 3.2 x 107 b σ┴ < 1.7 x 107b 4107 D.Oellers et al., Physics Letters B 674 (2009) 269 2107 depol (barn) 0 -2107 -4107 0 110-3 210-3 310-3 D.Oellers et al., Physics Letters B 674 (2009) 269 |Relative velocityofelectrons in protonrestframe| (c) RESULT: Selectiveflip: e+pbarspin-flip cross-sectionistoolow MILESTONE forthefield! PAX - Polarized Antiprotons

  8. HowtoPolarizeAntiprotons? Spin-1/2 particles 2 states selectiveflip selectiveremoval polarized unpolarized unpolarized polarized • Does not affectintensity • Reduces beam intensity PAX - Polarized Antiprotons

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

  10. Spin-filtering P…beam particlespinorientation Q…targetparticlespinorientation k || beam direction unpolarized p beam polarized target PAX - Polarized Antiprotons

  11. Spin-filtering P…beam particlespinorientation Q…targetparticlespinorientation k || beam direction polarized p beam polarized target PAX - Polarized Antiprotons

  12. 1992: Filter Test at TSR with protons Spin filteringworksforprotons F. Rathmann. et al., PRL 71, 1379 (1993) PAX submitted new proposal to find out how well does spin filtering work for antiprotonsMeasurement ofthe Spin-Dependenceofthe pp Interaction atthe AD Ring (CERN-SPSC-2009-012 / SPSC-P-337) PAX - Polarized Antiprotons

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

  14. Spin-dependence of the pbar-p interaction TRANSVERSE 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). LONGITUDINAL Oct. 2009 SPS Committee: … Taking into account the timeline and constraints of the various projects concerned, the SPSCencourages the PAX Collaboration to first perform their spin filtering measurements at COSY… PAX - Polarized Antiprotons

  15. Spin Filtering Studies at COSY Spin filtering with protons for better understanding of the underlying processes and commissioning of the experimental setup • Length: 183.4 m • Injectionenergy: 45 MeV • Electroncoolingforlonglifetimes • upto 600 MeV/c (p) PAX - Polarized Antiprotons

  16. Experimental setupat PAX-IT Low-β Quadrupoles ABS Target Chamber PAX - Polarized Antiprotons

  17. Low-bsection Beam lifetime : Low-βsection off Low-βsection on PAX - Polarized Antiprotons

  18. Atomic Beam Source PAX - Polarized Antiprotons

  19. Target chamber SAES getter pump (each 1900 l/s) HiPace 1800 turbo (1200 l/s) PAX - Polarized Antiprotons

  20. Beam polarimeter Measurement of asymmetry in pd-elastic scattering 2 Silicon Tracking Telescopes left and right of the COSY beam Deuterium Cluster Target (dt=1014 atoms/cm2) PAX - Polarized Antiprotons

  21. Spin-filteringcycle Spin-flipper clustertarg. + STT (beam polarimetry) p COSY ring polarizedtarget PAX - Polarized Antiprotons

  22. Spin-filtering: results W. Augustyniaket al., Physi. Lett. B 712 (2012) 64 • MILESTONE FOR THE FIELD! • Confirms understanding of spin-filtering as a viable method to polarize a stored beam. • Confirms complete control of the systematics of the experiment. Mar. 2012 SPS Committee: … many positive developments have occurred at the AD, leading to an updated program for the coming years ….We consider that PAX is now incompatible with this program. PAX - Polarized Antiprotons

  23. Polarizedantiprotons: situation Status: • Successfull (negative) spin-flip test at COSY • Successfullspinfilteringmeasruement at COSY on transversetarget. • Excellentagreementwiththeoreticalpredictionsforprotons • Successfullcommissioningof experimental setupforexperimentswithantiproton • Present perspective • Spin filtering with protons and a longitudinally polarized gas target at COSY at Tp130 MeV ( scattering) • Still pending: • Spin-filteringexperimentsat AD exploringthesystems, , () (transverseand longitudinal polarization) PAX - Polarized Antiprotons

  24. PAX nextfutureplans Waiting forapprovalat CERN (orconstructionof FAIR facility) Longitudinal spin-filteringtest at COSY  mandatoryfordeterminationof total spin-filteringcross-section Superconducting 4.7 Tm solenoidordered Longitudinal beam polarimeter in pre‘aration: -> nexttalkfrom V. Carassiti PAX - Polarized Antiprotons

  25. PAX - Polarized Antiprotons

  26. Additional Slides PAX - Polarized Antiprotons

  27. Spin Filteringwith Longitudinal Polarization • Buildup of longitudinal beam polarization due torepeatedinteractionwith a longitudinallypolarized hydrogen target • Tp 45 - 130 MeV kineticprotonenergy • Detector: Measurement of longitudinal beam polarizationusingelasticscattering • Measurement duringfilteringwith hydrogen targetpossible • Spin correlationcoefficient (~ 0.5) • Nobackground PAX - Polarized Antiprotons

  28. Expectedpolarizations after filteringfortwolifetimes transverse longitudinal A D PAX - Polarized Antiprotons

  29. Additional calculations… PLB 690 (2010) Projected polarizations PAX - Polarized Antiprotons

  30. Stages ofinstallationat AD Installation of six magnets for the low-β insertion Phase 1 Installation of the target chamber: Machine acceptance studies. Stacking studies Phase 2 Spin-filtering measurements up to 70 MeV with transverse beam polarization Phase 3 PAX - Polarized Antiprotons

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