On the minimality of the order p^6 chiral Lagrangian

A method to find relations between the operators in the mesonic Lagrangian of Chiral Perturbation Theory at order p^6 is presented. The procedure can be used to establish if the basis of operators in the Lagrangian is minimal. As an example, we apply the method to the two-flavour case in the absence of scalar and pseudo-scalar sources (s=p=0), and conclude that the minimal Lagrangian contains 27 independent operators.Comment: 14 pages, 2 figure

Renormalization Group Analysis in NRQCD for Colored Scalars

The vNRQCD Lagrangian for colored heavy scalar fields in the fundamental representation of QCD and the renormalization group analysis of the corresponding operators are presented. The results are an important ingredient for renormalization group improved computations of scalar-antiscalar bound state energies and production rates at next-to-next-to-leading-logarithmic (NNLL) order.Comment: 19 pages, 8 figures; revtex4. References added; version to appear in Phys. Rev.

The Upsilon -> X gamma photon spectrum in the soft-energy region

The dominant contribution of the next-to-leading order perturbative QCD corrections to the Upsilon -> X gamma photon energy spectrum for photon energies w ~ m_b alpha_s can be obtained trivially from the knowledge of the corresponding O(alpha) correction to the positronium decay spectrum in the same region. The latter can be obtained from the NRQED computation of the orthopositronium photon spectrum, or by applying the threshold expansion to the 1-loop QED amplitude, as it is explained in this talk.Comment: 7 pages, 5 figures. Contribution to the proceedings of EFT'09 - International Workshop on Effective Field Theories: from the Pion to the Upsilon-, 1-6 February 2009, Valencia (Spain

Integrating out heavy particles with functional methods: a simplified framework

We present a systematic procedure to obtain the one-loop low-energy effective Lagrangian resulting from integrating out the heavy fields of a given ultraviolet theory. We show that the matching coefficients are determined entirely by the hard region of the functional determinant involving the heavy fields. This represents an important simplification with respect the conventional matching approach, where the full and effective theory contributions have to be computed separately and a cancellation of the infrared divergent parts has to take place. We illustrate the method with a descriptive toy model and with an extension of the Standard Model with a heavy real scalar triplet. A comparison with other schemes that have been put forward recently is also provided.Comment: 24 pages. Uses feynMF packag