Interpretation of the "$f_{D_s}$ puzzle" in SM and beyond

TL;DR

This paper investigates the $f_{D_s}$ puzzle by analyzing leptonic and semileptonic D and $D_s$ decays within the Standard Model using a lightfront quark model, and explores unparticle physics as a new physics explanation.

Contribution

It demonstrates that tuning phenomenological parameters in a lightfront quark model can resolve the $f_{D_s}$ puzzle without conflicting with other decay data, and examines unparticle effects as an alternative explanation.

Findings

Parameter tuning can explain the $f_{D_s}$ discrepancy.

Unparticle physics can induce constructive interference and CP violation.

The model remains consistent with existing decay measurements.

Abstract

The recent measurement on the decay constant of $D_s$ shows a discrepancy between theory and experiment. We study the leptonic and semileptonic decays of $D$ and $D_s$ simultaneously within the standard model by employing a lightfront quark model. There is space by tuning phenomenological parameters which can explain the "$f_{D_s}$ puzzle" and do not contradict other experiments on the semileptonic decays. We also investigate the leptonic decays of D and $D_{s}$ with a new physics scenario, unparticle physics. The unparticle effects induce a constructive interference with the standard model contribution. The nontrivial phase in unparticle physics could produce direct CP violation which may distinguish it from other new physics scenarios.