Resolution Studies on Silicon Strip Sensors with fine Pitch

In June 2008 single-sided silicon strip sensors with 50 $\mu$m readout pitch were tested in a highly energetic pion beam at the SPS at CERN. The purpose of the test was to evaluate characteristic detector properties by varying the strip width and the number of intermediate strips. The experimental setup and first results for the spatial resolution are discussed.Comment: proceeding of the International Linear Collider Workshop 2008 (LCWS08); corrected typos, added reference for section

Measurements of time-dependent CP asymmetries in B→D∗∓π±B \to D^{*\mp} \pi^{\pm} decays using a partial reconstruction technique

We report results on time-dependent CP asymmetries in $B \to D^{*\mp}\pi^{\pm}$ decays based on a data sample containing 657 {\times} $10^6$ $B\bar{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider at the $\Upsilon(4S)$ resonance. We use a partial reconstruction technique, wherein signal $B \to D^{*\mp}\pi^{\pm}$ events are identified using information only from the fast pion from the B decay and the slow pion from the subsequent decay of the $D^{*\mp}$, where the former (latter) corresponds to $D^{*+} (D^{*-})$ final states. We obtain CP violation parameters $S^+ = +0.061 \pm 0.018(\mathrm{stat}) \pm 0.012(\mathrm{syst})$ and $S^- = +0.031 \pm 0.019(\mathrm{stat}) \pm 0.015(\mathrm{syst})$.Comment: 8 pages, 5 figures, 2 tables, submitted to Physical Review D (RC

Observation of D0−Dˉ0D^0-\bar{D}^0 Mixing in e+e−e^+e^- Collisions

We observe $D^0-\bar{D}^0$ mixing in the decay $D^0\rightarrow K^+\pi^-$ using a data sample of integrated luminosity 976 fb$^{-1}$ collected with the Belle detector at the KEKB $e^+e^-$ asymmetric-energy collider. We measure the mixing parameters ${x'}^2 = (0.09\pm0.22)\times 10^{-3}$ and $y' = (4.6\pm3.4)\times 10^{-3}$ and the ratio of doubly Cabibbo-suppressed to Cabibbo-favored decay rates $R_D = (3.53\pm0.13)\times 10^{-3}$, where the uncertainties are statistical and systematic combined. Our measurement excludes the no-mixing hypothesis at the 5.1 standard deviation level.Comment: 6 pages, 4 figure

First Observation of Radiative B^0 -> \phi K^0 \gamma Decays and Measurements of Their Time-Dependent CP Violation

We report the first observation of the radiative decay B^0 -> \phi K^0 \gamma using a data sample of 772 x 10^6 B B-bar pairs collected at the \Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+e^- collider. We observe a signal of 37+/-8 events with a significance of 5.4 standard deviations including systematic uncertainties. The measured branching fraction is ${\cal B}(B^0 -> \phi K^0 \gamma) = (2.74\pm 0.60 \pm 0.32) \times 10^{-6}$, where the uncertainties are statistical and systematic, respectively. We also report the first measurements of time-dependent CP violation parameters: ${\mathcal S}_{\phi K_S^0 \gamma} = +0.74^{+0.72}_{-1.05} (stat)^{+0.10}_{-0.24} (syst)$ and ${\mathcal A}_{\phi K_S^0 \gamma} = +0.35 +/- 0.58 (stat)^{+0.23}_{-0.10} (syst)$. Furthermore, we measure ${\mathcal B}(B^+ -> \phi K^+ \gamma) = (2.48 +/- 0.30 +/- 0.24) x 10^{-6}$, ${\mathcal A}_{CP} = -0.03 +/- 0.11 +/- 0.08$ and find that the signal is concentrated in the M_{\phi K} mass region near threshold.Comment: 6 pages, 3 figures, Modified version is to be published in PRD(RC

Search for the decay B+→K‾∗0K∗+B^+\rightarrow\overline{K}{}^{*0}K^{*+} at Belle

We report a search for the rare charmless decay $B^+\rightarrow\overline{K}{}^{*0}K^{*+}$ using a data sample of $772\times10^6$ $B\bar{B}$ pairs collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. No statistically significant signal is found and a 90% confidence-level upper limit is set on the decay branching fraction as $\mathcal{B}(B^+\rightarrow\overline{K}{}^{*0}K^{*+}) <1.31\times 10^{-6}$.Comment: 8 pages, 3 figures, submitted to PRD(RC

Search for the 0−−0^{--} Glueball in Υ(1S)\Upsilon(1S) and Υ(2S)\Upsilon(2S) decays

We report the first search for the $J^{PC}=0^{--}$ glueball in $\Upsilon(1S)$ and $\Upsilon(2S)$ decays with data samples of $(102\pm2)$ million and $(158\pm4)$ million events, respectively, collected with the Belle detector. No significant signals are observed in any of the proposed production modes, and the 90\% credibility level upper limits on their branching fractions in $\Upsilon(1S)$ and $\Upsilon(2S)$ decays are obtained. The inclusive branching fractions of the $\Upsilon(1S)$ and $\Upsilon(2S)$ decays into final states with a $\chi_{c1}$ are measured to be \BR(\Upsilon(1S)\to \chi_{c1}+ anything) = (1.90\pm 0.43(stat.)\pm 0.14(syst.))\times 10^{-4} with an improved precision over prior measurements and \BR(\Upsilon(2S)\to \chi_{c1}+ anything) = (2.24\pm 0.44(stat.)\pm 0.20(syst.))\times 10^{-4} for the first time.Comment: 19 pages, 17 figures, Fig.10b was polished, but all the results unchanged. Paper was published in PR

Measurement of eta_c(1S), eta_c(2S) and non-resonant eta' pi+ pi- production via two-photon collisions

We report the measurement of gamma gamma to eta_c(1S), eta_c(2S) to eta' pi+ pi- with eta' decays to gamma rho and eta pi+ pi- using 941 fb^{-1} of data collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. The eta_c(1S) mass and width are measured to be M = [2984.6\pm0.7 (stat.)\pm2.2 (syst.)] MeV/c^{2} and \Gamma = [30.8^{+2.3}_{-2.2}~(stat.) \pm 2.5~(syst.)] MeV, respectively. First observation of eta_c(2S) to eta' pi+ pi- with a significance of 5.5sigma including systematic error is obtained, and the eta_c(2S) mass is measured to be M = [3635.1\pm3.7~(stat.)\pm2.9~(syst.)] MeV/c^{2}. The products of the two-photon decay width and branching fraction (B) of decays to eta'pi+ pi- are determined to be \Gamma_{gamma gamma}B = [65.4\pm2.6~(stat.)\pm6.9~(syst.)] eV for eta_c(1S) and [5.6^{+1.2}_{-1.1}~(stat.)\pm1.1~(syst.)] eV for eta_c(2S). A new decay mode for the eta_c(1S) to eta'f_0(2080) with f_0(2080) to pi+ pi- is observed with a statistical significance of 20sigma. The f_0(2080) mass and width are determined to be M = [2083^{+63}_{-66}~(stat.)\pm 32~(syst.)] MeV/c^{2} and \Gamma = [178^{+60}_{-178}~(stat.) \pm 55~(syst.)] MeV. The cross sections for gamma gamma to eta' pi+ pi- and eta'f_{2}(1270) are measured for the first time.Comment: 19 pages, 14 figure

Observation of an alternative χc0(2P)\chi_{c0}(2P) candidate in e+e−→J/ψDDˉe^+ e^- \rightarrow J/\psi D \bar{D}

We perform a full amplitude analysis of the process $e^+ e^- \rightarrow J/\psi D \bar{D}$, where $D$ refers to either $D^0$ or $D^+$. A new charmoniumlike state $X^*(3860)$ that decays to $D \bar{D}$ is observed with a significance of $6.5\sigma$. Its mass is ($3862^{+26}_{-32}{}^{+40}_{-13}$) MeV/$c^2$ and width is ($201^{+154}_{-67}{}^{+88}_{-82}$) MeV. The $J^{PC}=0^{++}$ hypothesis is favored over the $2^{++}$ hypothesis at the level of $2.5\sigma$. The analysis is based on the 980 $\mathrm{fb}^{-1}$ data sample collected by the Belle detector at the asymmetric-energy $e^+ e^-$ collider KEKB.Comment: 17 pages, 11 figure

Search for B+ -> l+ nu gamma decays with hadronic tagging using the full Belle data sample

We search for the decay B+ -> l+ nu gamma with l+ = e+ or mu+ using the full Belle data set of 772 x 10^6 BBbar pairs, collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We reconstruct one B meson in a hadronic decay mode and search for the B+ -> l+ nu gamma decay in the remainder of the event. We observe no significant signal within the phase space of E_gamma^sig > 1 GeV and obtain upper limits of BR(B+ -> e+ nu gamma) mu+ nu gamma) l+ nu gamma) < 3.5 x 10^-6 at 90 % credibility level.Comment: Submitted to Phys. Rev.