Spin dependent fragmentation function at Belle

The measurement of the so far unknown chiral-odd quark transverse spin distribution in either semi-inclusive DIS (SIDIS) or inclusive measurements in pp collisions at RHIC has an additional chiral-odd fragmentation function appearing in the cross section. These chiral-odd fragmentation functions (FF) can for example be the so-called Collins FF or the Interference FF. HERMES has given a first hint that these FFs are nonzero, however in order to measure the transversity one needs these FFs to be precisely known. We have used 29.0 fb$^{-1}$ of data collected by the Belle experiment at the KEKB $e^+e^-$ collider to measure azimuthal asymmetries for different charge combinations of pion pairs and thus access the Collins FF.Comment: Results presented at the DIS 2006 conference in Tsukuba, Japa

Scrutinizing LSP Dark Matter at the LHC

We show that LHC experiments might well be able to determine all the parameters required for a prediction of the present density of thermal LSP relics from the Big Bang era. If the LSP is an almost pure bino we usually only need to determine its mass and the mass of the SU(2) singlet sleptons. This information can be obtained by reconstructing the cascade $\tilde{q}_L \to \tilde{\chi}_2^0 q \to \tilde{\ell}_R \ell q \to \tilde{\chi}_1^0 \ell^+ \ell^- q$. The only requirement is that $m_{\tilde{\ell}_R} < m_{\tilde{\chi}_2^0}$, which is true for most of the cosmologically interesting parameter space. If the LSP has a significant higgsino component, its predicted thermal relic density is smaller than for an equal--mass bino. We show that in this case squark decays also produce significant numbers of $\tilde{\chi}_4^0$ and $\tilde{\chi}_2^\pm$. Reconstructing the corresponding decay cascades then allows to determine the higgsino component of the LSP

Sector logic implementation for the ATLAS endcap level-1 muon trigger

We present development of the Sector Logic for the ATLAS endcap Level-1 (LVL1) muon trigger. The muon tracks from the interaction point (IP) are bent by the magnetic fields induced by the ATLAS toroidal magnets. The Sector Logic reconstructs three dimensional muon tracks with six levels of transverse momentum (pT) by combining two sets (R-Z and φ-Z) of information from the Thin Gap Chamber (TGC) detectors. Then, it selects two highest pT tracks in each trigger sector. The Sector Logic module is designed in pipelined structure to achieve no-dead-time operation and shorter latency. Look-Up-Tables (LUTs) are used so that any pT threshold level can be set. To achieve these, we adopted SRAM embedded type FPGA devices. The design and its performance are given in this presentation

Observation of Radiative Decay D0→ϕγD^0 \to \phi \gamma

We report the observation of the decay $D^{0} \to \phi \gamma$ with a statistical significance of $5.4\sigma$ in 78.1 \ifb of data collected by the Belle experiment at the KEKB $e^+ e^-$ collider. This is the first observation of a flavor-changing radiative decay of a charmed meson. The Cabibbo- and color-suppressed decays $D^0 \to \phi \pi^0$, $\phi \eta$ are also observed for the first time. We measure branching fractions \br(D^{0} \to \phi \gamma) = [ 2.60^{+0.70}_{-0.61} \stat {}^{+0.15}_{-0.17} \syst ] \times 10^{-5}, \br(D^{0} \to \phi \pi^{0}) = [ 8.01 \pm 0.26 \stat \pm 0.47 \syst ] \times 10^{-4}, and \br(D^{0} \to \phi \eta) = [ 1.48 \pm 0.47 \stat \pm 0.09 \syst ] \times 10^{-4}.Comment: 9 pages, 4 figures, Belle Preprint 2003-24, KEK Preprint 2003-75, updated version of BELLE-CONF-0346 (contributed paper to the XXI International Symposium on Lepton and Photon Interactions at High Energies,Fermilab Aug 11-16,2003). to appear in Phys. Rev. Let

Search for time-dependent B0s - B0s-bar oscillations using a vertex charge dipole technique

We report a search for B0s - B0s-bar oscillations using a sample of 400,000 hadronic Z0 decays collected by the SLD experiment. The analysis takes advantage of the electron beam polarization as well as information from the hemisphere opposite that of the reconstructed B decay to tag the B production flavor. The excellent resolution provided by the pixel CCD vertex detector is exploited to cleanly reconstruct both B and cascade D decay vertices, and tag the B decay flavor from the charge difference between them. We exclude the following values of the B0s - B0s-bar oscillation frequency: Delta m_s < 4.9 ps-1 and 7.9 < Delta m_s < 10.3 ps-1 at the 95% confidence level.Comment: 18 pages, 3 figures, replaced by version accepted for publication in Phys.Rev.D; results differ slightly from first versio