1 / 13

Azimuthal dependence in unpolarized proton-induced Drell-Yan processes

Explore azimuthal dependence in proton-induced Drell-Yan processes, investigating high twist effects, nuclear distortion, flavor-blind vacuum correlations, and factorization-breaking spin correlations. Data analysis from Fermilab E866/NuSea experiment suggests potential explanations for observed azimuthal asymmetries.

jessicaddavis
Download Presentation

Azimuthal dependence in unpolarized proton-induced Drell-Yan processes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Azimuthal dependence in unpolarized proton-induced Drell-Yan processes Lingyan Zhu, Jen-Chieh Peng University of Illinois at Urbana-Champaign Paul Reimer Argonne National Laboratory (FNAL E866/NuSea Collaboration) Mini-symposium on orbital motion of quarks in hard scattering 2nd joint meeting of the APS DNP and JPS Maui, Hawaii, Sep 18-22, 2005

  2. Angular distribution for the Drell-Yan processes In the simple parton model: ( for massless quarks and  measured relative to the annihilation axis) =1 and ==0 Correction due to QCD is small.

  3. Azimuthal cos2 distribution in the W Drell-Yan Conway et al., PRD39,92(1989) E615 at Fermilab: 252 GeV π- + W NA10 at CERN: 140/194/286 GeV π- + W Z. Phys. C37, 545 (1988)

  4. Possible explanations for the cos2 asymmetry • The high twist in terms of pion bound state effect is not enough. Brandenburg, Brodsky, Khoze & Muller, PRL73,939(1994) • The nuclear distortion of hadronic projectile wavefunction, typically a spin-orbit effect occuring on the nuclear surface. =0 for pp Drell-Yan. Bianconi & Radici, JPG31,645(2005). • The spin correlation due to nontrival QCD vacuum.—Flavor blind. Brandenburg, Nachtmann & Mirkes, Z. Phy. C60,697(1993) Boer,Brandenburg,Nachtmann&Utermann, EPC40,55(2005). • The non-zero chiral-odd distribution function h1?. It is equal to Sivers function f1T?in the quark-diquark spectator model. Boer, PRD60,014012(1999); …

  5. QCD vacuum effects • Brandenburg, Nachtmann & Mirkes, Z. Phy. C60,697(1993) • The factorization-breaking spin correlation due to nontrivial QCD vacuum may fit the NA10 data at 194 GeV • The helicity flip in the instanton-induced contribution may lead to nontrivial vacuum. • Boer,Brandenburg,Nachtmann&Utermann, EPC40,55(2005). • This vacuum effect should be flavor blind. 0=0.17 mT=1.5

  6. Boer-Mulders function h1? • Boer, PRD60,014012(1999) • An spin-correlation approach in terms of h1? can fit the NA10 data at 194 GeV. • On the base of quite general arguments, for |qT|<<Q(=m), • Salvo,hep-ph/0407208. 1=0.5 mC=2.3 T=CH=1

  7. Models with Boer-Mulders function h1? • The quark-spectator-antiquark model with effective pion-quark-antiquark coupling as a dipole form factor Lu & Ma, hep-ph/0504184 • Twist 2 (as well as the kinematic twist 4) contribution in a parton-spectator framework Gamberg&Goldstein, hep-ph/0506127.

  8. Fermi Lab E866/NuSea experiment Drell-Yan events Analyzed (4.5<M<9, M>11) including pp+- X; pd+- X High Mass Setting: dset7-39k, dset8-85k (+ polarity) dset11-25k (- polarity) Low Mass Setting: dset5-68k (+ polarity)

  9. Muon momenta Blue: simulation Red: data (dset8) +! -!

  10. Comparison of data and simulation Blue: simulation Red: data (dset8)

  11. Extraction of azimuthal cos2distribution Fit Func: p1[1+p3/2 cos2+ p2cos( + p4)] Data M.C. Data/M.C.

  12. Azimuthal cos2distribution for Drell-Yan processes Very Preliminary

  13. Summary • Large cos2 azimuthal asymmetry has been observed in unpolarized -induced Drell-Yan. • The are a few possible explanations including the non-trivial vacuum effect and the non-zero Boer-Mulders function h1? . The latter is related to the Sivers function f1T?. • The unpolarized p-induced Drell-Yan data seem to suggest small cos2 azimuthal asymmetry. This may disfavor the flavor blind explanation such as vacuum effect.

More Related