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Register a new userFirst experimental study of photon polarization in radiative $B^{0}_{s}$ decays
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The polarization of photons produced in radiative $B^{0}_{s}$ decays is studied for the first time. The data are recorded by the LHCb experiment in $pp$ collisions corresponding to an integrated luminosity of 3fb$^{-1}$ at center-of-mass energies of $7$ and $8$TeV. A time-dependent analysis of the $B^{0}_{s} to phi gamma$ decay rate is conducted to determine the parameter ${mathcal{A}}^Delta$, which is related to the ratio of right- over left-handed photon polarization amplitudes in $b to s gamma$ transitions. A value of ${mathcal{A}}^Delta=-0.98^{,+0.46,+0.23}_{,-0.52,-0.20}$ is measured. This result is consistent with the Standard Model prediction within two standard deviations.
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Radiative penguin decays provide an indirect probe for physics beyond the Standard Model and contribute to the determination of the CKM matrix elements. Copious quantities of B mesons produced at the B-Factories permit precision measurements of radiative penguin decays. We review the experimental status of the radiative penguin processes b --> s(d) gamma.
The radiative decays of $b$-baryons facilitate the direct measurement of photon helicity in $bto sgamma$ transitions thus serving as an important test of physics beyond the Standard Model. In this paper we analyze the complete angular distribution of ground state $b$-baryon ($Lambda_{b}^{0}$ and $Xi_{b}^{-}$) radiative decays to multibody final states assuming an initially polarized $b$-baryon sample. Our sensitivity study suggests that the photon polarization asymmetry can be extracted to a good accuracy along with a simultaneous measurement of the initial $b$-baryon polarization. With higher yields of $b$-baryons, achievable in subsequent runs of the Large Hadron Collider (LHC), we find that the photon polarization measurement can play a pivotal role in constraining different new physics scenarios.
A measurement of the photon polarization in radiative penguin $B$ decays provides a test of the Standard Model and a probe for New Physics, that can lead to a deviation from the Standard Model prediction of left-handed photons in $bto s gamma$. We propose a new method to measure the photon polarization using the baryonic decay $B^- to Lambdabar{p} gamma$. The $P$-violating $Lambda$-hyperon decay allows a measurement of the $Lambda$ helicity to be performed, which can be uniquely related to the photon polarization in a model-independent way. The $B^- to Lambdabar{p} gamma$ decay was recently measured to have a large branching fraction providing a possibility to get meaningful results with the data already available at LHC and B-factory experiments. An increase of the $B$-meson sample at high luminosity LHC experiments and Belle II should provide a really stringent test by using this method already in the near future.
We report a search for charmless hadronic decays of charged $B$ mesons to the final states $K^{0}_{S} K^{0}_{S} K^{pm}$ and $K^{0}_{S} K^{0}_{S} pi^{pm}$ . The results are based on a $711 {fb}^{-1}$ data sample that contains $772 times 10^6$ $B bar{B}$ pairs, and was collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. For $B^{pm} to K^{0}_{S} K^{0}_{S} K^{pm}$ decays, the measured branching fraction and direct $CP$ asymmetry are $[10.64pm0.49(stat)pm 0.44(syst)]times10^{-6}$ and [$-0.6pm3.9(stat)pm 3.4(syst)$] %, respectively. In the absence of a statistically significant signal for $B^{pm}to K^{0}_{S} K^{0}_{S} pi^{pm}$, we set the 90 % confidence-level upper limit on its branching fraction at $1.14 times 10^{-6}$.
A search for previously unobserved decays of beauty baryons to the final states $K^0_{mathrm{S}}ppi^-$ and $K^0_{mathrm{S}}pK^-$ is reported. The analysis is based on a data sample corresponding to an integrated luminosity of $1.0,mathrm{fb}^{-1}$ of $pp$ collisions. The $Lambda^0_b rightarrow K^0_{mathrm{S}}ppi^-$ decay is observed for the first time with a significance of $8.6,sigma$, and a measurement is made of the $CP$ asymmetry, which is consistent with zero. No significant signals are seen for $Lambda^0_b rightarrow K^0_{mathrm{S}}pK^-$ decays, $Xi^0_b$ decays to both $K^0_{mathrm{S}}ppi^-$ and $K^0_{mathrm{S}}pK^-$ final states, and the $Lambda^0_b rightarrow D^-_s (K^0_{mathrm{S}}K^-)p$ decay, and upper limits on their branching fractions are reported.
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