The gamma-ray telescope Gamma-1

French and Soviet specialists have designed and built the gamma-ray telescope GAMMA-1 to detect cosmic gamma rays above 50 MeV. The sensitive area of the detector is 1400 sq cm, energy resolution is 30% at 300 MeV, and angular resolution 1.2 deg at 300 MeV (and less than 20' arc when a coded aperture mask is used). Results on calibration of the qualification model and Monte-Carlo calculations are presented

Measurement of J/ψ→γηcJ/\psi\to\gamma\eta_{\rm c} decay rate and ηc\eta_{\rm c} parameters at KEDR

Using the inclusive photon spectrum based on a data sample collected at the $J/\psi$ peak with the KEDR detector at the VEPP-4M $e^+e^-$ collider, we measured the rate of the radiative decay $J/\psi\to\gamma\eta_{\rm c}$ as well as $\eta_{\rm c}$ mass and width. Taking into account an asymmetric photon lineshape we obtained $\Gamma^0_{\gamma\eta_{\rm c}}=2.98\pm0.18 \phantom{|}^{+0.15}_{-0.33}$ keV, $M_{\eta_{\rm c}} = 2983.5 \pm 1.4 \phantom{|}^{+1.6}_{-3.6}$ MeV/$c^2$, $\Gamma_{\eta_{\rm c}} = 27.2 \pm 3.1 \phantom{|}^{+5.4}_{-2.6}$ MeV.Comment: 6 pages, 3 figure

Measurement of B(J/psi->eta_c gamma) at KEDR

We present a study of the inclusive photon spectrum from 6.3 million J/psi decays collected with the KEDR detector at the VEPP-4M e+e- collider. We measure the branching fraction of the radiative decay J/psi -> eta_c gamma, eta_c width and mass. Taking into account an asymmetric photon line shape we obtain: M(eta_c) = (2978.1 +- 1.4 +- 2.0) MeV/c^2, Gamma(eta_c) = (43.5 +- 5.4 +- 15.8) MeV, B(J/psi->eta_c gamma) = (2.59 +- 0.16 +- 0.31)%$.Comment: 6 pages, 1 figure. To be published in the proceedings of the 4th International Workshop on Charm Physics (Charm2010), October 21-24, 2010, IHEP, Beijin

Measurement of J/psi to eta_c gamma at KEDR

We present a study of the inclusive photon spectra from 5.9 million J/psi decays collected with the KEDR detector at the VEPP-4M e+e- collider. We measure the branching fraction of radiative decay J/psi to eta_c gamma, eta_c width and mass. Our preliminary results are: M(eta_c) = 2979.4+-1.5+-1.9 MeV, G(eta_c) = 27.8+-5.1+-3.3 MeV, B(J/psi to eta_c gamma) = (2.34+-0.15+-0.40)%.Comment: To be published in Proceedings of the PhiPsi09, Oct. 13-16, 2009, Beijing, Chin

Search for double charmonium decays of the P-wave spin-triplet bottomonium states

Using a sample of 158 million $\Upsilon(2S)$ events collected with the Belle detector, we search for the first time for double charmonium decays of the $P$-wave spin-triplet bottomonium states ($\Upsilon(2S) \to \gamma \chi_{bJ}$, \chi_{bJ} \to \jpsi \jpsi, \jpsi \psp, \psp \psp for J=0, 1, and 2). No significant $\chi_{bJ}$ signal is observed in the double charmonium mass spectra, and we obtain the following upper limits, \BR(\chi_{bJ} \to \jpsi \jpsi)<7.1\times 10^{-5}, $2.7\times 10^{-5}$, $4.5\times 10^{-5}$, \BR(\chi_{bJ} \to \jpsi \psp)<1.2\times 10^{-4}, $1.7\times 10^{-5}$, $4.9\times 10^{-5}$, \BR(\chi_{bJ} \to \psp \psp)<3.1\times 10^{-5}, $6.2\times 10^{-5}$, $1.6\times 10^{-5}$ for J=0, 1, and 2, respectively, at the 90% confidence level. These limits are significantly lower than the central values (with uncertainties of 50% to 70%) predicted using the light cone formalism but are consistent with calculations using the NRQCD factorization approach.Comment: 7 pages, 4 figures, 1 tabl

Self-Trapped Excitons in Ionic-Covalent Silver Halide Crystals and Nanostructures: High-Frequency EPR, ESE, ENDOR and ODMR Studies

Silver halides have unique features in solid state physics because their properties are considered to be of borderline nature between ionic and covalent bonding. In AgCl, the self-trapped hole (STH) is centered and partly trapped in the cationic sublattice, forming an Ag2+ ion inside of a (AgCl6)4− complex as a result of the Jahn–Teller distortion. The STH in AgCl can capture an electron from the conduction band forming the self-trapped exciton (STE). Recent results of a study of STE by means of high-frequency electron paramagnetic resonance, electron spin echo, electron–nuclear double resonance (ENDOR) and optically detected magnetic resonance (ODMR) are reviewed. The properties of the STE in AgCl crystals, such as exchange coupling, the ordering of the triplet and singlet sublevels, the dynamical properties of the singlet and triplet states, and the hyperfine interaction with the Ag and Cl (Br) nuclei are discussed. Direct information about the spatial distribution of the wave function of STE unpaired electrons was obtained by ENDOR. From a comparison with the results of an ENDOR study of the shallow electron center and STH, it is concluded that the electron is mainly contained in a hydrogen-like 1s orbital with a Bohr radius of 15.1 ± 0.6 Å, but near its center the electron density reflects the charge distribution of the hole. The hole of the STE is virtually identical to an isolated STH center. For AgCl nanocrystals embedded into the KCl crystalline matrix, the anisotropy of the g-factor of STE and STH was found to be substantially reduced compared with that of bulk AgCl crystals, which can be explained by a considerable suppression of the Jahn–Teller effect in nanoparticles. A study of ODMR in AgBr nanocrystals in KBr revealed spatial confinement effects and allowed estimating the nanocrystal size from the shape of the ODMR spectra

Search for CP Violation in the Decays D0→KS0P0D^0\rightarrow K^0_S P^0

We have searched for CP violation in the decays $D^0\rightarrow K^0_S P^0$ where $P^0$ denotes a neutral pseudo-scalar meson which is either a $\pi^0$, $\eta$, or $\eta'$ using KEKB asymmetric-energy $e^+e^-$ collision data corresponding to an integrated luminosity of 791 fb$^{-1}$ collected with the Belle detector. No evidence of significant CP violation is observed. We report the most precise CP asymmetry measurement in the decay $D^0\rightarrow K^0_S\pi^0$ to date: $A_{CP}^{D^0\rightarrow K^0_S\pi^0}=(-0.28\pm0.19\pm0.10)$. We also report the first measurements of CP asymmetries in the decays $D^0\rightarrow K^0_S\eta$ and $D^0\rightarrow K^0_S\eta'$: $A_{CP}^{D^0\rightarrow K^0_S\eta}=(+0.54\pm0.51\pm0.16)$ and $A_{CP}^{D^0\rightarrow K^0_S\eta'}=(+0.98\pm0.67\pm0.14)$, respectively

Search for Lepton Flavor and Lepton Number Violating tau Decays into a Lepton and Two Charged Mesons

We search for lepton flavor and lepton number violating tau decays into a lepton (ell = electron or muon) and two charged mesons (h,h' = pi^\pm or K^\pm), tau- -> ell-h+h'- and tau- -> ell+h-h'-, using 671 fb^{-1} of data collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. We obtain 90% C.L. upper limits on the branching fractions in the range (4.4-8.8)x10^{-8} for tau -> ehh', and (3.3-16)x10^{-8} for tau -> muhh' processes. These results improve upon previously published upper limits by factors between 1.6 to 8.8.Comment: 15 page, 7 figures, submitted to Phys. Lett.

Evidence for B to K eta' gamma Decays at Belle

We present the results of a search for the radiative decay (B -> K eta' gamma) and find evidence for (B^+ -> K^+ eta' gamma) decays at the 3.3 standard deviation level with a partial branching fraction of (3.6 +/- 1.2 +/- 0.4) x 10e-6, where the first error is statistical and the second systematic. This measurement is restricted to the region of combined (K eta') invariant mass less than 3.4GeVc^2. A 90% confidence level upper limit of 6.4 x 10e-6 is obtained for the decay (B^0 -> K^0 eta' gamma) in the same (K eta') invariant mass region. These results are obtained from a 605 fb^-1 data sample containing 657 x 10e6 B anti-B pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+e^- collider.Comment: 5 pages, 4 figures. Submitted to PRD-RC on 6/8/0