Session H9: Bottom Quark Physics

Recent Bottomonium Results from Belle

Using a 121 $fb^{-1}$ data sample collected in e+e- collisions near the peak of the $\Upsilon(5S)$ resonance, the Belle Collaboration has over the past year obtained several significant results concerning singlet-P ($h_b$) and singlet-S ($\eta_b$) states of the bottomonium system, and, additionally, for charged bottomonium-like states denoted $Z_b$. In this talk we will present results of measurements of the masses of singlet-P and singlet-S states, branching fractions for radiative transitions from singlet-P to singlet-S, and studies of the charged $Z_b$ states through which the singlet-P state production is understood to occur.   

A Search for Bottomonium-like Resonances at the Collider Detector at Fermilab

The Belle experiment recently reported evidence for two bottomonium-like charged resonances, \(Z_b^+(10610)\) and \(Z_b^+(10650)\), observed in decays from the \(\Upsilon(5S)\). We present a search for these resonances in CDF data. In contrast to the Belle observation, we search for \(Z_b\) states directly produced in \(p\bar{p}\) collisions and decaying to an \(\Upsilon(1S, 2S, 3S)\) plus a charged pion. Since such a state must both be charged and contain a bottom and an anti- bottom quark, it would indicate a new hadronic state, for example, a tetraquark state. Starting from a sample of \(\Upsilon(1S, 2S, 3S)\) candidates selected by their decay to \(\mu^+\mu^-\), we add a pion and search for the \(Z_b\) resonances. We check the sensitivity by reconstructing \(\Upsilon(2S, 3S) \to \Upsilon(1S)\mu^+\mu^-\) decay.   

Measurements of quark fragmentation using kaons produced in association with prompt \(D_{(s)}^+\) mesons at CDF

We report the first study of quark fragmentation through identification of kaons produced during the fragmentation of charm quarks, produced in \(1.96\,\mathrm{TeV}\) \(p\bar{p}\) collisions, to form \(D_s^+\) or \(D^+\) mesons. We apply particle identification techniques to measure the fraction of events in which a track produced in association with the prompt charm meson is a kaon and compare the observed kinematic properties with predictions of fragmentation models implemented in standard Monte Carlo event generators providing valuable validation and tuning information.   

Measurement of the \(B^0_s \to J/\psi\phi \) branching fraction at CDF

We present a measurement of the branching fraction of the decay \(B^0_s \to J/\psi\phi\) with the Collider Detector at Fermilab. Using a data sample corresponding to an integrated luminosity of \(10\,\mathrm{fb}^{-1}\) of \(p\bar{p}\) collisions at \(\sqrt{s}=1.96\,\mathrm{TeV}\), we utilize a low transverse momentum dimuon trigger to acquire a large sample of \(J/\psi\to\mu^+\mu^-\) decays. We form fully reconstructed \(B^0_s \to J/\psi\phi\) and \(B^0\to J/\psi K^{\ast}\) candidates using information from the central tracking system and determine the branching fraction of \(B^0_s \to J/\psi\phi\) by normalizing with the \(B^0\to J/\psi K^{\ast}\) decay. The measurement improves the current world average value and can be used to extract information about the ratio of fragmentation fractions \(f_s/f_d\) between \(B^0_s\) and \(B^0\) production rates.   

Search for $B^0_s\rightarrow\mu^+\mu^-$ at D0

In this talk we present an update of the search for $B^0_s\rightarrow\mu^+\mu^-$ using the full D0 data set, $\sim~11~\textrm{fb}^{-1}$. In this analysis, the backgrounds have been significantly reduced by adding isolation variables and reconstructing additional vertices near the $B^0_s$ decay vertex. Other changes from the previous D0 result include the addition of $4~\textrm{fb}^{-1}$ of additional data and the use of a Boosted Decision Tree to discriminate between signal and background.   

$b$-tagging calibration of ATLAS data using the System8 method

We present results of calibrating the efficiency of various $b$-tagging algorithms using data taken with the ATLAS detector in 2011. The calibration method, called $System8$, separates a sample of jets containing muons into 8 subsamples based on whether they pass or fail three different methods for selecting $b$-jets: passing a Soft Muon tagging algorithm, passing a Lifetime tagging algorithm, and the presence of a corresponding $b$-tagged jet opposite the one under study. A system of 8 equations, which relates the fraction of $b$-jets, the tagging efficiencies and the correlations between the three subsamples to the observed numbers of events in each subsample, is then solved to extract the $b$-tagging efficiencies. We will show the basic procedures behind System8 and the measured efficiencies with statistical and systematic uncertainties. These efficiencies will be compared to those obtained from Monte Carlo truth information. Scale factors relating the measured efficiencies to those obtained from Monte Carlo will also be presented.   

$B^{\pm}_{c}$ meson observation at ATLAS

We observed $B^{\pm}_{c}$ mesons with the ATLAS detector at the LHC through the hadronic decay of $B^{\pm}_{c}\rightarrow J/\psi(\mu^{+}\mu^{-}) \pi^{\pm}$, with 4.3 $fb^{-1}$ 2011 data from 7 TeV pp collisions. The resulting $B^{\pm}_{c}$ mass distribution is fitted with an unbinned maximum likelihood fit. The mass value is consistent with the world average value.   

Search for Double J/Psi Resonances in CMS at the LHC

We have analyzed an integrated luminosity of 4.5 fb$^{-1}$ of proton-proton collision data from the LHC with the CMS detector in search for the J/Psi J/Psi decay of the eta-b meson, the pseudo-scalar ground-state of bottomonium. The cross-section times decay width is predicted at a level of 10$^{-4}$ to 10$^{-8}$. We perform a maximum likelihood fit to the 4-muon invariant mass and the decay length to extract the signal yield.