Search For New Physics at BABAR

Using a full BABAR data sample of 426 $fb^{-1}$, we present improved measurements of the ratio ${\cal{R}}(D^{(*)}) = {\cal{B}} (\bar{B} \to D^{(*)}\tau^{-}\bar{\nu}_{\tau})/$ ${\cal{B}} (\bar{B} \to D^{(*)}\ell_{\ell}^{-}\bar{\nu}_{\ell})$, where $\ell$ is either electron or muon. We measure ${\cal{R}}(D) = 0.440 \pm 0.058 \pm 0.042$ and ${\cal{R}}(D^*) = 0.332 \pm 0.024 \pm 0.018$. These ratios exceed the Standard Model predictions by $2.0\sigma$ and $2.7\sigma$, respectively. The results disagree with the Standard Model predictions at the level of $3.4\sigma$. The ratios are sensitive to new physics contributions in the form of a charged Higgs boson. However, the access cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model.Comment: Contributed to the Proceedings of Hadron Collider Physics Symposium 2012, Kyoto, Japan, November 12-16 201

Search for Muonic Dark Forces at BABAR

Many models of physics beyond Standard Model predict the existence of light Higgs states, dark photons, and new gauge bosons mediating interactions between dark sectors and the Standard Model. Using a full data sample collected with the BABAR detector at the PEP-II e+e− collider, we report searches for a light non-Standard Model Higgs boson, dark photon, and a new muonic dark force mediated by a gauge boson (Z′) coupling only to the second and third lepton families. Our results significantly improve upon the current bounds and further constrain the remaining region of the allowed parameter space

Measurement of the Absolute Branching Fraction of D^0 to K^- \pi^+

The authors measure the absolute branching fraction for D{sup 0} {yields} K{sup -} {pi}{sup +} using partial reconstruction of {bar B}{sup 0} {yields} D*{sup +} X {ell}{sup -} {bar {nu}}{sub {ell}} decays. Only the charged lepton and the soft pion from the decay D*{sup +} {yields} D{sup 0} {pi}{sup +} are used. Based on a data sample of 230 million B{bar B} pairs collected at the {Upsilon}(4S) resonance with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC, they obtain {Beta}(D{sup 0} {yields} K{sup -} {pi}{sup +}) = (4.025 {+-} 0.038 {+-} 0.098)%, where the first error is statistical and the second error is systematic