Antiproton Polarization Studies for FAIR

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Paul Joseph Harrington
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1 Mitglied der Helmholtz-Gemeinschaft Antiproton Polarization Studies for FAIR How to produce polarized antiprotons (and what to use them for?) May 31, 2008 Hans Ströher Transversity 2008 (Ferrara, Italy)

2 Introduction ~ 3 years ago, we proposed a method to polarize antiprotons by spin-filtering Folie 2

3 Introduction New initiative, driven by the FAIR-project at GSI Folie 3

4 Introduction High Energy Storage Ring (HESR) for a beam of antiprotons (How) is it possible to provide polarized antiproton beams in HESR? Folie 4

5 Plan of talk The (long) road to polarized antiprotons: Proposals, ideas, calculations, Experiments Depolarization studies at COSY FILTEX (TSR) Spin-filtering at COSY Spin-filtering at AD/CERN Summary, Conclusion taken on by the PAX-collaboration (Spokespersons: F. Rathmann (Jülich), P. Lenisa (Ferrara)) Folie 5

6 Proposed methods (1): Some history EPAC 1988 Stern-Gerlach splitting never tried (huge effort) Folie 6

7 Proposed methods (2): Recent paper Need for an experimental test of this idea! Folie 7

8 Depolarization Studies at COSY: Idea Use proton beam and co-moving electrons Turn experiment around: p e p into p e p i.e. depolarization of a polarized proton beam COSY electron Velocity cooler (detuned) mismatch Folie 8

depolarize proton beam Analyze proton polarization with internal

9 Depolarization Studies at COSY: Principle Use (transversely) polarized proton beam circulating in COSY Switch on (detuned) electron cooler to depolarize proton beam Analyze proton polarization with internal D2-cluster target of ANKE ANKE cluster target & STT e-cooler p Tp = 49 MeV Folie 9

10 Depolarization Studies at COSY: Details Detuned Cooler Voltage Tdetuned= 50 s V ~ few 100 V Nominal Cooler Voltage Tnominal = 100 s D2 target off Ecooler on/detuned D2 target on Ecooler on Folie 10

11 Beam current Depolarization Studies at COSY: Measurements Folie 11

12 Depolarization Studies at COSY: Polarimetry pd elastic scattering; detection in silicon tracking telescopes (STT) Prelimin a ry p d Folie 12

13 Depolarization Studies at COSY: Results ln σ depol = Pdet uned P nominal Δt d t f rev v/c ~ 0.002!! Preliminary!! No effect observed, i.e. cross section must be many orders-of-magnitude smaller than 1013b! Folie 13

14 Depolarization Studies at COSY: New calc s (NIM B) /JNIMB ~ 1 mb No effect expected! Folie 14

15 Depolarization Studies at COSY: No effect expected, too? (since high cross section is for longitudinal polarization) Note: disagreement w/ MSS calculation by 1016!! Folie 15

16 Spin-filtering: Polarization build-up of an originally unpolarized particle beam by repeated interaction with polarized hydrogen target, e.g. in a storage ring: Spin-filtering is known to work ( FILTEX ); not clear, how (see above) Folie 16

17 Spin-filtering at TSR: FILTEX TSR Test Storage Ring at MPI Heidelberg FILTEX Filter Experiment (1992) Folie 17

18 Spin-filtering at TSR: FILTEX proof-of-principle PhD of F. Rathmann Spin filtering works for protons Folie 18

19 Spin-filtering at COSY: Optimize, understand FILTEX p pp = 0.3 GeV/c ABS + storage cell, Si-tracking det s (HERMES) Superconducting quadrupole (new) Need a lowß section in COSY Folie 19

Spin-filtering at COSY: Low-ß Section Target: Storage cell 3

10 5 0 16.8 17.3 17.8 18.3 18.8 19.3 19.8 20.3 20.8 21.3 21.

20 Spin-filtering at COSY: Low-ß Section Target: Storage cell Beta functions [m] Polarimeter Length [m] Need superconducting quadrupoles Folie 20

21 Spin-filtering at CERN/AD: pp and pd scattering Target (equipment used, tested at COSY) Electron cooler (upgrade of existing AD-cooler) Snake (also longitudinal; new) Measurement of effective p polarization build-up cross section First measurement of spin-correlations in above reactions Folie 21

22 Spin-filtering at COSY: Milestones, timeline COSY: determine / optimize beam lifetime - needed for large filtering time (beamtime in II/2008) SC quadrupoles design almost ready; companies have been contacted (order in 2008) COSY: set up HERMES-ABS and recoil detectors (2009) COSY: implement set-up in ring (early 2010), perform sf -measurements CERN/AD: LoI full proposal; move equipment and repeat with anti-protons (~ 2011) By 2012/13 we will know how to do spin-filtering!! Design the APR (antiproton polarizer ring) Folie 22

23 Hadron Physics Dream Machine for FAIR: an asymmetric (double-polarized) proton (15 GeV/c) antiproton (3.5 GeV/c) collider using HESR, CSR and APR Folie 23

24 Quark Transversity Distribution in Drell-Yan: Double transverse spin asymmetry: Folie 24

25 Summary: p e pp p e+ pp long. trans. WAKBJ: gigantic??? MSS: small small 1016 Folie 25

26 Summary: p e pp p e+ pp long. trans. WAKBJ: gigantic??? MSS: small small No depolarization of polarized protons Folie 26

27 Summary: Spin-filtering works: p e pp p (FILTEX) COSY p e+ pp p CERN/AD long. trans. WAKBJ: gigantic??? MSS: small small No depolarization of polarized protons Folie 27

28 Conclusion: The road towards polarized antiprotons is long But: - clear roadmap - commitment by PAX-collaboration - first measurements/achievements We appreciate any help! Note: Now and here (expertise) or never (not in a very long time)! Folie 28

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

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