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Tensor structure in high-energy proton-deuteron reactions

Shunzo Kumano High Energy Accelerator Research Organization (KEK) Graduate University for Advanced Studies (GUAS). Tensor structure in high-energy proton-deuteron reactions. shunzo.kumano@kek.jp http://research.kek.jp/people/kumanos/. Based on works with

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Tensor structure in high-energy proton-deuteron reactions

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  1. Shunzo Kumano High Energy Accelerator Research Organization (KEK) Graduate University for Advanced Studies (GUAS) Tensor structurein high-energy proton-deuteron reactions shunzo.kumano@kek.jp http://research.kek.jp/people/kumanos/ Based on works with F. E. Close, S. Hino, T.-Y. Kimura, M. Miyama KEK theory center workshop on Short-range correlations and tensor structure at J-PARC September 25, 2009

  2. Contents  Introduction to tensor structure functions Tensor structure functions (b1, …, b4) Sum rule, Projection to each structure function from W  Polarized proton-deuteron Drell-Yan processes Note: The proton does not have to be polarized for b1. If a polarized-deuteron target will becomes available at J-PARC or any other facilities, it is a possible experiment.

  3. Introduction to Tensor Structure Functions

  4. References on tensor structure function b1 Theoretical formalism for polarized electron-deuteron deep inelastic scattering P. Hoodbhoy, R. L. Jaffe, and A. Manohar, NP B312 (1989) 571. [ L. L. Frankfurt and M. I. Strikman, NP A405 (1983) 557. ] HERMES experimental result A. Airapetian et al., Phys. Rev. Lett. 95 (2005) 242001. Our works Sum rule for b1 F. E. Close and SK, Phys. Rev. D 42 (1990) 2377. Projections to b1, …, b4 from W T.-Y. Kimura and SK, Phys. Rev. D 78 (2008) 117505.

  5. Motivation  Spin structure of the spin-1/2 nucleon Nucleon spin puzzle: This issue is not solved yet, but it is rather well studied theoretically and experimentally.  Spin-1 hadrons (e.g. deuteron) There are some theoretical studies especially on tensor structure in electron-deuteron deep inelastic scattering.  HERMES experimental results A few investigations have been done for polarized proton-deuteron processes.  J-PARC experiment ?

  6. Structure function b1 in a simple example Spin-1 particles (deuteron, mesons) b1=0 only in S-wave • The b1 probes a dynamical aspect of hadron structure • beyond simple expectations of a naive quark model. • Description of tensor structure by quark-gluon degrees of freedom

  7. Electron scattering from a spin-1 hadron P. Hoodbhoy, R. L. Jaffe, and A. Manohar, NP B312 (1989) 571. [ L. L. Frankfurt and M. I. Strikman, NP A405 (1983) 557. ]

  8. Projections to F1, F2, …, b4 from W T.-Y. Kimura and SK, PRD 78 (2008) 117505.

  9. Structure Functions Parton Model

  10. Sum rule for b1 F.E.Close and SK, PRD42, 2377 (1990). Elastic amplitude in a parton model

  11. Macroscopically If the sum-rule violation is shown by experiment, it suggests antiquark tensor polarization.

  12. 27.6 GeV/c positron deuteron HERMES results on b1 A. Airapetian et al. (HERMES), PRL 95 (2005) 242001. Drell-Yan experiments probe these antiquark distributions.

  13. +  E866 q – J-PARC E906 q Actual experimental proposals at J-PARC: P04, P24 Antiquark distributions  It should be possible to use polarized proton-deuteron Drell-Yan processes to measure the tensor polarized distributions.

  14. Polarized proton-deuteron Drell-Yan process

  15. References • General formalism for polarized Drell-Yan processes with spin-1/2 and spin-1 hadrons M. Hino and SK, Phys. Rev. D59 (1999) 094026. • Parton-model analysis of polarized Drell-Yan processes with spin-1/2 and spin-1 hadrons M. Hino and SK, Phys. Rev. D60 (1999) 054018. • An application: Possible extraction of polarized light-antiquark distributions from Drell-Yan SK and M. Miyama, Phys. Lett. B497 (2000) 149. Comments on the situation • There was a feasibility study for polarized deuteron beam at RHIC: E. D. Courant, BNL-report (1998). • No acutual experimental progress with hadron facilities. • Future: J-PARC, COMPASS, U70, GSI-FAIR, RHIC, …

  16. Purposes of studying polarized deuteron reactions Status

  17. c.m. frame Formalism of pd Drell-Yan process See Ref. PRD59 (1999) 094026. proton-proton proton-deuteron Number of structure functions 48 108 Additional structure functions due to tensor structure 11 22 I will briefly explain in the following. In parton model 3 4

  18. Drell-Yan cross section and hadron tensor Possible vectors to expand W Expand W by possible combinations

  19. Structure functions and cross sections

  20. Q1 Q0 Q2 Possible spin asymmetries The quadrupole spin asymmetries arenew ones in spin-1 hadron reactions. pp Drell-Yan pd Drell-Yan

  21. Parton-model analysis We express  in terms of parton distributions. The details are in PRD60 (1999) 054018.

  22. Spin asymmetries in the parton model Unpolarized cross section Spin asymmetries

  23. Summary on pd Drell-Yan

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