Misha Nekipelov, Kolya Nikolaev*, Frank RathmannMisha Nekipelov, Kolya Nikolaev*, Frank Rathmann

Institut für Kernphysik, Forschungszentrum JülichInstitut für Kernphysik, Forschungszentrum Jülich*Landau Institute, Chernogolovka, Russia*Landau Institute, Chernogolovka, Russia

Spin Filtering in Storage Rings from a Spin Filtering in Storage Rings from a Theorists Perspective: Anno 2009Theorists Perspective: Anno 2009

DSPIN-2009, 1-5 September 2009, Dubna

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W. Pauli

N. Bohr

Even they were puzzled by spin… Even they were puzzled by spin… then A. Krish et al stormed the then A. Krish et al stormed the

fieldfield

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Why polarized antiprotons?

• Quest for the transversity: the last missing leading twist SF of the proton

• Without transversity the spin tomography of the proton will be ever incomplete

• PAX at FAIR (E.Steffens‘ talk): double spin DY as a direct access to transversity, a unique successor to 4 decades of DIS physics

• M.Anselmino et al: Encouraging signals from model-dependent extractions of transversity

• Spin filtering: a unique way to HIGH LUMI double polarized proton-antiproton collider

• Other ideas on how to polarize antiprotons?

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Long way to Tippereray: Dreams & Misconceptions & Enlightenment

• 40 years of dreaming of polarized antiprotons• LEAR: missed opportunities• FILTEX!• Meyer & Horowitz: asking key questions• Rathmann et al.: immaculate conception of

PAX misdriven by Meyer‘s interpretation of FILTEX

• Milstein & Strakhovenko & NNN & Pavlov & infidels (Shatunov...): electrons are useless

• Hoegel‘s dialectic spiral: backdoor e‘s Walcher et al.

• 1st PAX expt at COSY: back to hadronic spin filtering for antiprotons

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What Could Happen to a Spin in a Polarized Internal Target?

For an ensemble of spin ½ particles with projections + () and - ()

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Spin Filtering Anno 2004: betting on e‘s

~ 5 years ago, PAX proposed a method to polarize antiprotons

by „spin-filtering“

Milstein & Strakhovenko & NNN & Pavlov: a no-go theorem

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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”

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New ideas: spin flip in polarized e-cooler

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No effect expected ! Confirmed by PAX-ANKE at COSY.

The corollary: bet on hadronic spin filtering of anti-p‘s

10.1016/JNIMB.2008.04.010

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Antiproton-nucleon interactions: more in Nurushev‘s talk

• A wealth of good data from LEAR• Nice measurements of single-spin

asymmetries• No substantial data on double spin

observables: only low statistics recoil proton polarization estimates

• Ask theorists: Could the theory help?

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Good and not so good news from models:

• A good news: All models „predict“ non-vanishing double spin observables

• 10-20 percent polarization of filtered antiprotons is feasible

• Not so good news: Predictions differ by factor 2-3 in magnitude and wildely regading the energy dependence: hence I omit slides

• K. Adenauer: „Why should I care about that nonsense I promised yesterday?“ --- go to AD CERN and measure youself!

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Summary and oulook:

• We possess a quantitative theory of spin-filtering & spin-flip phenomena in storage rings

• Still it is prudent to check everything with protons at COSY where the theory is under tight control (SAID & Nijmegen databases)

• The deuterium PIT must not be forgotten!• Antiprotons: neither solid theory no exptl

database for double spin observables: do it yourself at AD CERN (PAX)

• A consolation: still the models do “predict“ a nonvanishing filtering cross section and 10-20 per sent polarization of filtered antiprotons

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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”

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