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What pHe3 can teach us

What pHe3 can teach us. Polarized He-3 is an effective neutron target  d-quark target Polarized protons are an effective u-quark target. Therefore combining pp and pHe3 data will allow a full quark flavor separation u, d, ubar , dbar. Two physics trusts for a polarized pHe3 program:

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What pHe3 can teach us

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  1. What pHe3 can teach us • Polarized He-3 is an effective neutron target  d-quark target • Polarized protons are an effective u-quark target Therefore combining pp and pHe3 data will allow a full quark flavor separation u, d, ubar, dbar • Two physics trusts for a polarized pHe3 program: • Measuring the sea quark helicity distributions through W-production • Access to Ddbar • Caveat maximum beam energy for He-3: 166 GeV • Need increased luminosity to compensate for lower W-cross section • Measuring single spin asymmetries AN for pion production and Drell-Yan • expectations for AN (pions) • similar effect for π± (π0 unchanged) 3He: helpful input for understanding of transverse spin phenomena Critical to tag spectator protons from 3He with roman pots

  2. eRHIC: polarized eHe3 scattering • Future: • Polarized electron – proton and electron – He3 scattering allows for a test of the best know Sum Rule in QCD The Bjoerken Sum Rule Calculated in pQCD Currently measured to 10% g1p and g1n: polarized structure functions EIC could provide a 1-2% measurement, if beam polarization Is measured to 1-2%

  3. More insights to the proton Transversity distribution function dq(x) Single Spin Asymmetries Unpolarized distribution function q(x), G(x) beyond collinear picture Explore spin orbit correlations Sivers distribution function Boer-Mulders distribution function Correlation between and Helicity distribution function Dq(x),DG(x) Correlation between and Correlation between and E.C. Aschenauer He-3 Workshop, BNL, September 2011

  4. u d Dq: W Production Basics Since W is maximally parity violating W’s couple only to one partonhelicity large Δuand Δdresult inlarge asymmetries. No Fragmentation ! Similar expression for W- to get Δ and Δd… E.C. Aschenauer He-3 Workshop, BNL, September 2011

  5. expectations for ALe in pp collisions de Florian, Vogelsang t large u large t large u large strong sensitivity to limited sensitivity to E.C. Aschenauer He-3 Workshop, BNL, September 2011

  6. ALW: Future Possibilities ALW: He3-p @ 432 GeV ALW: pp @ 500 GeV phase 2 of pp2pp@STAR can separate scattering on n or p E.C. Aschenauer He-3 Workshop, BNL, September 2011 • Can we increase p-beam energy? • 325 GeV: factor 2 in sW • access to lower x for Dg(x) • Increased beam-energy and polarized He-3 beam  full flavor separation

  7. Quantum phase-space tomography of the nucleon 3D picture in momentum space 3D picture in coordinate space transverse momentum generalized parton distributions dependent distributions  exclusive reaction like DVCS Wigner Distribution W(x,r,kt) Join the real 3D experience !! TMDs GPDs d3r d2ktdz u-quark Polarized p Polarized p d-quark E.C. Aschenauer He-3 Workshop, BNL, September 2011

  8. The long term future future of pp@RHIC AN in 3He-proton collisions Siversfcts. for u and d quarks opposite in sign and slightly larger for d quarks expectations for Drell Yan Z. Kang @ 2010 Iowa RSC meeting • u <-> disospin rotation leads to different signs for AN for protons and neutrons • asymmetries for neutrons are larger (due to electric charges) proton caveat: does not yet include possibility of nodes in Sivers function neutron expectations for AN (pions) • similar effect for π± (π0 unchanged) • this time computed within twist-3 formalism • here, effect due to favored/unfavored fragmentation 3He: helpful input for understanding of transverse spin phenomena E.C. Aschenauer He-3 Workshop, BNL, September 2011

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