The $b rightarrow s gamma$, $b rightarrow d gamma$ and $b rightarrow s ell^+ ell^-$ processes are allowed at higher order via the electroweak loop or box diagrams in the Standard model. It is sensitive probe to search for new physics beyond the Stand
ard model because new particles might enter in the loop. We present preliminary results of branching fraction of the $bar{B} rightarrow X_s gamma$, $CP$ asymmetry in the $bar{B} rightarrow X_{s+d} gamma$, and the forward-backward asymmetry in the $bar{B} rightarrow X_s ell^+ ell^-$. The results are based on a data sample containing $772 times 10^6 Bbar{B}$ pairs recorded at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider.
We report the first measurement of the lepton forward-backward asymmetry ${cal A}_{rm FB}$ as a function of the squared four-momentum of the dilepton system, $q^2$, for the electroweak penguin process $B rightarrow X_s ell^+ ell^-$ with a sum of excl
usive final states, where $ell$ is an electron or a muon and $X_s$ is a hadronic recoil system with an $s$ quark. The results are based on a data sample containing $772times10^6$ $Bbar{B}$ pairs recorded at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. ${cal A}_{rm FB}$ for the inclusive $B rightarrow X_s ell^+ ell^-$ is extrapolated from the sum of 10 exclusive $X_s$ states whose invariant mass is less than 2 GeV/$c^2$. For $q^2 > 10.2$ GeV$^2$/$c^2$, ${cal A}_{rm FB} < 0$ is excluded at the 2.3$sigma$ level, where $sigma$ is the standard deviation. For $q^2 < 4.3$ GeV$^2$/$c^2$, the result is within 1.8$sigma$ of the Standard Model theoretical expectation.
We report a measurement of the CP-violation parameter sin2$phi_1$ at the $Upsilon(5S)$ resonance using a new tagging method, called $B$-$pi$ tagging. In $Upsilon(5S)$ decays containing a neutral $B$ meson, a charged $B$, and a charged pion, the neutr
al $B$ is reconstructed in the $J/psi K_S^0$ CP-eigenstate decay channel. The initial flavor of the neutral $B$ meson at the moment of the $Upsilon(5S)$ decay is opposite to that of the charged $B$ and may thus be inferred from the charge of the pion without reconstructing the charged $B$. From the asymmetry between $B$-$pi^+$ and $B$-$pi^-$ tagged $J/psi K_S^0$ yields, we determine sin2$phi_1$ = 0.57 $pm$ 0.58(stat) $pm$ 0.06(syst). The results are based on 121 fb$^{-1}$ of data recorded by the Belle detector at the KEKB $e^+ e^-$ collider.
We fabricated a readout ASIC with the fully depleted silicon-on-insulator (FD-SOI) technology for the pair-monitor. The pair-monitor is a silicon pixel device that measures the beam profile of the international linear collider. It utilizes the direct
ional distribution of a large number of electron-positron pairs created by collision of bunches, and is required to tolerate radiation dose of about a few Mrad/year. The irradiation might cause the buried oxide layer of SOI to accumulate charges which interfere with intended functions. We thus performed extensive irradiation tests on the prototype ASIC, and the results are described in this paper.
