Constraints on Unparticle Interaction from $b\to s \gamma$

TL;DR

This paper investigates how unparticles could influence the decay process $b o s \gamma$, deriving experimental constraints on unparticle couplings that vary with the unparticle dimension and suggesting polarization measurements as additional probes.

Contribution

It provides the first detailed analysis of unparticle effects on $b o s \gamma$ decay and derives constraints on unparticle couplings based on experimental data.

Findings

Constraints on vector unparticle couplings are stringent near $d_U o 1$.

Scalar unparticle couplings are less constrained than vector ones.

Polarization measurements in $\Lambda_b o \Lambda \gamma$ can further restrict unparticle interactions.

Abstract

We study unparticle effects on $b\to s \gamma$. The unparticle contributions can contribute significantly to both left- and right-handed chirality amplitudes. Using available experimental data and SM calculation for $B\to X_s \gamma$, we obtain constraints on various vector and scalar unparticle couplings. We find that the constraints sensitively depend on the unparticle dimension $d_\U$. For $d_\U$ close to one, the constraints can be very stringent. The constraints become weak when $d_\U$ is increased. In general the constraints on scalar unparticle couplings are weaker than those for vector unparticle couplings. Sizeable coupling strength for unparticles with quarks is still allowed. We also show that polarization measurement in $\Lambda_b \to \Lambda \gamma$ can further constrain the couplings.