Exclusive radiative decays ofΥin soft-collinear effective theory

Abstract

We study exclusive radiative decays of the Υ using soft-collinear effective theory and nonrelativistic QCD. In contrast to inclusive radiative decays at the endpoint we find that color-octet contributions are power suppressed in exclusive decays, and can safely be neglected, greatly simplifying the analysis. We determine the complete set of Lorentz structures that can appear in the SCET Wilson coefficients and match onto them using results from a previous calculation. We run these coefficients from the scale M Υ to the scale Λ ∼ 1 GeV, thereby summing large logarithms. Finally we use our results to predict the ratio of branching fractions B(Υ → γf 2 )/B(J/ψ → γf 2 ), B(J/ψ → γf 2 )/B(ψ ′ → γf 2 ), and the partial rate for Υ → γππ.

Radiative decays of theΥ(1S)to a pair of charged hadrons

“…These values are larger than, but the same order of magnitude as, the ratio of 0.04 expected from naive scaling arguments. The observed f 2 (1270) production is in agreement with the prediction in [3] and somewhat lower than the prediction in [2]. In both of the measured modes we can confirm by fits to the angular distributions of the photon and charged particles that the two daughter hadrons are indeed produced by a spin-2 parent.…”

“…The heavy-quarkonium system is usually described by non-relativistic QCD [1], while the gluonic hadronization has been treated using soft collinear effective theory [2], gluon distribution amplitudes [3], and perturbative QCD [4,5]. 2 Glueballs are a natural consequence of QCD, and predictions of their properties have been made using different approaches, such as potential models [6,7,8], lattice QCD calculations [9,10,11,12], bag models [13,14,15,16], flux-tube models [17], the QCD sum rules [18], the Bethe-Salpeter (B-S) equation [19,20], QCD factorization formalism models [21,22], weakly-bound-state models [23], and a three-dimensional relativistic equation [24]. However, despite intense experimental searches [25,26,27,28,29,30,31], there is no conclusive experimental evidence of their direct observation, although there are strong indications that glueballs contribute to the rich light scalar [32,33,34,35,36,37,38,39,40,41] and tensor [42,…”

Investigation of the bottomonium ground stateηbvia its inclusive charm decays

“…1 limit, the velocity and coupling expansions are no more valid in the vicinity of the end point. A proper treatment for this end point illness is to resum the large logarithms of log1 ÿ y 1 [23][24][25][26][27][28] and invoke the shape function [29]. For these kinds of content, readers should refer to the related references in the literature; and in this situation, the final state distribution results at the end point in this work should not be taken seriously.…”

Υ(1S)→γf2′(1525);Collaboration1, Besson2, Hogan3 et al. 2011Phys. Rev. D

“…A large f ′ 2 (1525) signal is observed in the di-K 0 S mass spectrum, with a branching fraction B(Υ(1S) → γf ′ 2 (1525)) = (4.0 ± 1.3 ± 0.6) × 10 −5 , consistent with previous measurements of Υ(1S) → γf ′ 2 (1525) [1]; f ′ 2 (1525) → K + K − . Although no predictions for this final state, per se, exist in the literature, we can nevertheless compare our calculated branching fraction, relative to the analogous branching fraction for J/ψ decays, with the predictions from SCET [2]. Combining our current result with the previous result for Υ(1S) → γf ′ 2 (1525) → γK + K − , we obtain an updated estimate B(Υ → γf ′ 2 (1525)) = (3.8 ± 0.9) × 10 −5 .…”

“…A comprehensive calculation using soft-collinear effective theory (SCET) and non-relativistic QCD has been implemented to calculate the ratio of 'non-exotic' branching fractions B(Υ(1S) → γf 2 )/B(J/ψ → γf 2 ) [2]. That theory calculation gives a predicted ratio of (0.13-0.18), slightly larger than the currently measured value for the f ′ 2 (1525) (0.08 ± 0.03 [1]), but not inconsistent with extant data, given the large errors.…”