Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Power counting and effective field theory for charmonium

Sean Fleming, Adam K. Leibovich, I. Z. Rothstein

TL;DR

This paper argues that charmonium dynamics may be better described by a new effective field theory power counting based on $\Lambda_{\rm QCD}/m_c$ (NRQCD$_c$) rather than the conventional velocity expansion (NRQCD$_b$). It contrasts the two schemes, deriving distinct hierarchies for color-octet matrix elements, and yields testable predictions across lifetimes, hadroproduction, polarization, and $B$ decays—most notably, polarization quenching at high $p_T$ and altered fixed-target cross-section ratios. The authors propose concrete experimental tests to distinguish the frameworks and discuss factorization and perturbative convergence concerns. If validated, NRQCD$_c$ would provide a more accurate description of $J/\psi$ and related charmonia, guiding future theoretical and experimental efforts."

Abstract

We hypothesize that the correct power counting for charmonia is in the parameter Lambda_QCD/m_c, but is not based purely on dimensional analysis (as is HQET). This power counting leads to predictions which differ from those resulting from the usual velocity power counting rules of NRQCD. In particular, we show that while Lambda_QCD/m_c power counting preserves the empirically verified predictions of spin symmetry in decays, it also leads to new predictions which include: A hierarchy between spin singlet and triplet octet matrix elements in the J/psi system. A quenching of the net polarization in production at large transverse momentum. No end point enhancement in radiative decays. We discuss explicit tests which can differentiate between the traditional and new theories of NRQCD.

Power counting and effective field theory for charmonium

TL;DR

This paper argues that charmonium dynamics may be better described by a new effective field theory power counting based on (NRQCD) rather than the conventional velocity expansion (NRQCD). It contrasts the two schemes, deriving distinct hierarchies for color-octet matrix elements, and yields testable predictions across lifetimes, hadroproduction, polarization, and decays—most notably, polarization quenching at high and altered fixed-target cross-section ratios. The authors propose concrete experimental tests to distinguish the frameworks and discuss factorization and perturbative convergence concerns. If validated, NRQCD would provide a more accurate description of and related charmonia, guiding future theoretical and experimental efforts."

Abstract

We hypothesize that the correct power counting for charmonia is in the parameter Lambda_QCD/m_c, but is not based purely on dimensional analysis (as is HQET). This power counting leads to predictions which differ from those resulting from the usual velocity power counting rules of NRQCD. In particular, we show that while Lambda_QCD/m_c power counting preserves the empirically verified predictions of spin symmetry in decays, it also leads to new predictions which include: A hierarchy between spin singlet and triplet octet matrix elements in the J/psi system. A quenching of the net polarization in production at large transverse momentum. No end point enhancement in radiative decays. We discuss explicit tests which can differentiate between the traditional and new theories of NRQCD.

Paper Structure

This paper contains 11 sections, 25 equations, 1 figure, 2 tables.

Table of Contents

  1. Introduction
  2. background
  3. NRQCD power counting
  4. New Power Counting
  5. Lifetimes
  6. Hadro-Production
  7. Collider experiments
  8. Fixed-target experiments
  9. Polarization
  10. $B$ decays
  11. Conclusion

Figures (1)

  • Figure 1: Predicted polarization in NRQCD$_c$ for $J/\psi$ and $\psi'$ at the Tevatron as a function of $p_T$. The three lines correspond to $R_{M/E}$=(0 (dashed), 1 (dotted), $\infty$ (solid)). The dashed line is also the prediction for NRQCD$_b$.