1 / 17

Exploring Nucleons and Nuclei: Update on EVMP from A.A. Horowitz, University of Cape Town

This presentation discusses the interplay between nucleons and nuclei through the lens of many-body quantum chromodynamics (QCD). It emphasizes the importance of understanding small-x nuclear profiles for accurately extracting relevant properties such as energy loss and spatial geometry. A key focus is on the independent, direct measurements provided by the Extended Vector Meson Production (EVMP) framework, alongside insights from previous studies leveraging gluon distribution in nuclear interactions. It highlights the challenges and potential impacts of coherence and saturation in future research.

quemby-warner
Télécharger la présentation

Exploring Nucleons and Nuclei: Update on EVMP from A.A. Horowitz, University of Cape Town

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. EVMP: Nucleons vs. NucleiAn Update W. A. Horowitz University of Cape Town February 2, 2012 CPTEIC

  2. Motivation • Many-body QCD: • Quantitative extraction of properties (h/s, E-loss,...) requires quantitative knowledge of the geometry • Physics of “the edge” very important, not under good theoretical control (non-perturbative) • EVMP provides an independent, direct measurement of the small-x nuclear profile • Very sensitive to edge physics CPTEIC

  3. Motivating EVMP • Recall e + A exps. on A at rest • Invert Dirac => Woods-Saxon distribution! Hahn, Ravenhall, and Hofstadter, Phys Rev 101 (1956) CPTEIC

  4. Gluon Distribution of A • Coherent vector meson production in e + A e e J/y g* A A • Invert ds/dt to measure gluon distribution • See diff. in ds/dt from diff. gluon evolution? CPTEIC

  5. ds/d2b: DGLAP • First Work: Compare DGLAP and KLN 2-gluon exchange straw men • 1) Assume incoherent interaction with nucleons (a la Caldwell & Kowalksi) & DGLAP • T: glue distribution in nucleon: • Integrate over WS distribution of nucleons in nucleus CPTEIC

  6. ds/d2b: KLN • 2) small-x evo. approx. by KLN • xgA is integrated KLN UGD: coherent nuclear effect • Simple KLN form for UGD • Back of the envelope calc. of Qs CPTEIC

  7. EVMP ds/dt Result • Huge growth in DGLAP Glauber x-scn • Nuclear shape changes for KLN, not for DGLAP Glauber WAH, arXiv:1102.5058 Must reject incoherent collisions at ~100% CPTEIC

  8. Two Issues 1) Only 2 gluon exchange • Expect mult. int. at saturation • Both straw men can violate black-disc limit 2) Pathology in nuclear size for KLN DGLAP Glauber (Blue) KLN CGC (Black) IPSat (Red) r = 1 GeV-1 x = 10-3 ds/d2b CPTEIC b (fm)

  9. First, Unitarize • Cut off DGLAP dipole at 1 • Exponentiate KLN r = 1 GeV-1 x = 10-6 ds/d2b DGLAP Glauber (Blue) KLN CGC (Black) IPSat (Red) b (fm) CPTEIC

  10. Unitarized Results DGLAPU (B, P, G; solid) DGLAP (B, P, G; dashed) DGLAPU (B, P, G) KLNU (Teal Band) • Little Change at “large” x • Sig. shape diff. from unitarization. NB esp. changes due to MSTW uncertainties, KLN’s slower dropoff x = 10-3 x = 10-6 ds/dt ds/dt t (GeV2) t (GeV2) CPTEIC

  11. Conclusions & Future Work • Conclusions: • 10-6 Results tantalizing proof of principle • See effect of coherence, saturation • Large effects from unconstrained PDF • Future Work • ds/dt directly from ds/d2b = 2N from rcBK • Comparison over range in x, including “large” x • Smaller PDF uncertainties • Explicitly see evolution of nuclear size with x CPTEIC

  12. CPTEIC

  13. ds/d2b • Simple 2-gluon exchange • Assume DGLAP evo. of glue & incoherent interaction with nucleons • Assume small-x evo. approx. by KLN • xgA is integrated KLN UGD, coherent nuclear effect CPTEIC

  14. KLN Gluon Distribution • Obtain GD from UGD • Simple KLN form for UGD • Back of the envelope Qs formula CPTEIC

  15. Gluon Distribution of A at x ~ 10-3 • Coherent vector meson production in e + A e e Must reject incoherent collisions at ~100% J/y g* A A WAH, arXiv:1102.5058 CPTEIC

  16. X-scn: CPTEIC

  17. ds/d2b • Simple 2-gluon exchange • Assume DGLAP evo. of glue & incoherent interaction with nucleons • Assume small-x evo. approx. by KLN • xgA is integrated KLN UGD, coherent nuclear effect CPTEIC

More Related