1 / 9

SCET Insights Into Heavy-to-Light Form Factors

SCET Insights Into Heavy-to-Light Form Factors. Matthias Neubert - Cornell. Some Open Issues. Field-theoretic understanding of the “ soft overlap ” contribution Systematic separation of short- and long-distance contributions Sudakov suppression of the soft contribution?

harry
Download Presentation

SCET Insights Into Heavy-to-Light Form Factors

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. SCET Insights Into Heavy-to-Light Form Factors Matthias Neubert - Cornell Vxb Workshop - SLAC

  2. Some Open Issues • Field-theoretic understanding of the “soft overlap” contribution • Systematic separation of short- and long-distance contributions • Sudakov suppression of the soft contribution? • pQCD vs. QCD factorization

  3. Soft Overlap • Have used SCET to define the soft overlap term: [Lange, Neubert: hep-ph/0311345] • Combination of soft, collinear and messenger contributions

  4. More Artistic View • Messenger exchange: soft collinear messenger sector

  5. Sudakov Resummation • Can use SCET to systematically resum all short-distance Sudakov logarithms: • for physical values of the B-meson mass, there is no sizable Sudakov suppression • E-dependence of the low-energy matrix element remains, which can only be controlled using a truly non-perturbative approach (lattice?) 0.5 0.75 αs(μ) = 1

  6. Importance of Non-Valence Fock States ? • SCET shows that 3-particle Fock states (in both B and π) contribute at the same order in Λ/mbas the leading Fock states • Not suppressed by any small parameter • A puzzle (to us) is why their effect appears to be tiny (<3%) in the light-cone sum rule approach

  7. Toy Model • Regularize endpoint singularities using cut-offs adjusted such that the leading Fock states reproduce LCSR (crude):

  8. Result • Find potentially large effects, which tend to reduce the values of the form factors • Effects tend to be larger for B V form factors • Is this effect real? Could it indicate a problem with light-cone sum rules (continuum model)?

  9. Summary • Physics of heavy-to-light form factors is subtle: • Transformation of soft collinear partons • Subleading quantities in SCET power counting (vanish at leading order) • This physics is not captured in quark models (ISGW, BSW, …) based on wave-function overlap integrals

More Related