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Future possibilities for W-physics

Future possibilities for W-physics. (Charm-associated W-boson production at RHIC). Hiroshi Yokoya (Niigata U.). in collaboration with Kazutaka Sudoh (KEK). RBRC workshop, April 26-27 2007 “ Parity-violating Spin Asymmetries at RHIC ”. Introduction.

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Future possibilities for W-physics

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  1. Future possibilities for W-physics (Charm-associated W-boson production at RHIC) Hiroshi Yokoya (Niigata U.) in collaboration with Kazutaka Sudoh (KEK) RBRC workshop, April 26-27 2007 “Parity-violating Spin Asymmetries at RHIC”

  2. Introduction • W-boson production at RHIC, /s = 500 GeV flavor structure of pol. PDFs : inclusive cross section : • W-boson + α • W-boson + Jets : pT-distribution, lepton angular distribution • W-boson + Gamma : radiation zero • W-boson + Charm : strange-quarkdistribution • W-boson + …

  3. W+Jetsresults from the Tevatron pT distribution D0 (’98) CDF (’91) lines: NLL+NLO non-perturbative parameter? spin dependence?

  4. P-even P-odd W+Jetsresults from the Tevatron Lepton Angular Distribution NLO : Mirkes (’92) CDF (’06) P-odd come from loop-diagrams (T-odd) Hagiwara,Hikasa,Kai (’84) Hagiwara,Hikasa,HY (’06)

  5. W+gamma production at RHIC Kawamura,Kiyo,Kodaira,Morii (’02) Radiation Zero : at some phase-space points (parton level) as a consequence of the trilinear coupling of gauge bosons in SM

  6. Charm-associated W-boson production in collaboration with K. Sudoh (KEK) • sub-process in LO : ← information on the s-quark pol. PDF • Cabibbo mixing :

  7. Cross sections in LO • unpolarized cross section : • polarized cross section : • Single longitudinal-spin asymmetry :

  8. Partonic cross-section, partonic asymmetry Feynman diagrams;

  9. Forward W : • Backward W :

  10. Hadronic Cross-Section Rapidity distribution : Total cross section :

  11. Spin asymmetry • Single-spin asymmetry • Expected statistical error Polarization degree : Luminosity : Detection efficiency :

  12. Spin asymmetry Rapidity difference :

  13. Spin asymmetry

  14. RHIC-II ?

  15. to be discussed • Detection of decay particles from W & charm • How can we measure the rapidities of W and c? • Is detection efficiency (ε=0.1) too overestimated? • Significant background? • Higher-order corrections • QCD NLO correction : K ~ 1.5–2 ?? new subprocess : • large corrections may come from

  16. Summary • Charm-associated W-boson production at RHIC • probe the polarized strange and gluon distributions • large Δd contribution for W-c production, through cabibbo mixing • measurerapidities to separate Δs and Δg • statistics is limited, and need more studies for the experimental signals • and NLO?

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