119210077
Refactorizing NRQCD short-distance coefficients in exclusive quarkonium production
In a typical exclusive quarkonium production process, when the center-of-mass energy, is much greater than the heavy quark mass in, large kinematic logarithms of s/m(2) will unavoidably arise at each order of perturbative expansion in the short-distance coefficients of the nonrelativistic QCD (NRQCD) factorization formalism, which may potentially harm the perturbative expansion. This symptom reflects that the hard regime in NRQCD factorization is too coarse and should be further factorized. We suggest that this regime can be further separated into "hard" and "collinear" degrees of freedom, so that the familiar light-cone approach can be employed to reproduce the NRQCD matching coefficients at the zeroth order of m(2)/s and order by order in alpha(s). Taking two simple processes, exclusive eta(b)+ gamma production in e(+)e(-) annihilation and Higgs boson radiative decay into gamma, as examples, we illustrate how the leading logarithms of s/m(2) in the NRQCD matching coefficients are identified and summed to all orders in alpha(s) with the aid of Brodsky-Lepage evolution equation. (C) 2009 Elsevier B.V. All rights reserved.
118456126
Broken S3 flavor symmetry of leptons and quarks: Mass spectra and flavor mixing patterns
Abstract We apply the discrete S 3 flavor symmetry to both lepton and quark sectors of the Standard Model extended by introducing one Higgs triplet and realizing the type-II seesaw mechanism for finite neutrino masses. The resultant mass matrices of charged leptons ( M l ), neutrinos ( M ν ), up-type quarks ( M u ) and down-type quarks ( M d ) have a universal form consisting of two terms: one is proportional to the identity matrix I and the other is proportional to the democracy matrix D . We argue that the textures of M l , M u and M d are dominated by the D term, while that of M ν is dominated by the I term. This hypothesis implies a near mass degeneracy of three neutrinos and can naturally explain why the mass matrices of charged fermions are strongly hierarchical, why the quark mixing matrix is close to I and why the lepton mixing matrix contains two large angles. We discuss a rather simple perturbation ansatz to break the S 3 symmetry and obtain more realistic mass spectra of leptons and quarks as well as their flavor mixing patterns. We stress that the I term, which used to be ignored from M l , M u and M d , is actually important because it can significantly modify the smallest lepton flavor mixing angle θ 13 or three quark flavor mixing angles.
118920016
On the Role of Charmed Meson Loops in Charmonium Decays
We investigate the effect of intermediate charmed meson loops on the M1 radiative decaysJ/ → �c and ' → � (') c as well as the isospin violating hadronic decays ' → J/ � 0 (�) using heavy hadron chiral perturbation theory (HHPT). The calculations include tree level as well as one loop diagrams and are compared to the latest data from CLEO and BES-III. Our fit constrains the couplings of 1S and 2S charmonium multiplets to charmed mesons, denoted g2 and g ' 2 , respectively. We find that there are two sets of solutions for g2 and g ' . One set, which agrees with previous values of the product g2gextracted from analyses that consider only loop contributions to ' → J/ � 0 (�), can only fit data on radiative decays with fine-tuned cancellations between tree level diagrams and loops in that process. The other solution for g2 and gleads to couplings that are smaller by a factor of 2.3. In this case tree level and loop contributions are of comparable size and the numerical values of the tree level contributions to radiative decays are consistent with estimates based on the quark model as well as non-relativistic QCD (NRQCD). This result shows that tree level HHPT couplings are as important as the one loop graphs with charmed mesons in these charmonium decays. The couplings g2 and gare also important for the calculations of the