Observation of B+-->psi(3770)K+

We report the first observation of the decay B+-->psi(3770)K+ where the psi(3770) is reconstructed in the D0(-)D(0) and D+D- decay channels. The obtained branching fraction is B(B+-->psi(3770)K+)=(0.48+/-0.11+/-0.07)x10(-3). We have measured the branching fraction for the decay B+-->D0(-)D0K+ to be (1.17+/-0.21+/-0.15)x10(-3) and set a 90% confidence level upper limit of 0.90 x 10(-3) for the decay B+-->D+D-K+. We also present the results of a search for possible decays to D(-)D and D0(-)D(0)pi(0) of the recently observed X(3872) particle. The analysis is based on 88 fb(-1) of data collected at the Upsilon(4S) resonance by the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider.     

Hydrogen atoms in impurity-helium solids

Electron spin resonance (ESR) is employed to study atomic impurities (H and D) stabilized in impurity-helium (Im-He) solids at 1.35-1.5 K. The kinetics of the low temperature tunneling exchange reactions (D+H2-->H+HD, D+HD-->H+D2) are investigated in Im-He samples containing several different mixtures of hydrogen and deuterium impurities. The ESR line structures help determine the local environment of atoms trapped in Im-He solids. High concentrations of atomic hydrogen stored in Im-He solids may ultimately find applications in energy storage, matrix-isolation spectroscopy, and studies of different quantum statistical effects.     

Study of the semileptonic charm decays D(0)-->pi(-)l(+)nu and D(0)-->K(-)l(+)nu

We investigate the decays D(0)-->pi(-)l(+)nu and D(0)-->K(-)l(+)nu, where l is e or mu, using approximately 7 fb(-1) of data collected with the CLEO III detector. We find R(0) identical with B(D(0)-->pi(-)e(+)nu)/B(D(0)-->K(-)e(+)nu)=0.082+/-0.006+/-0.005. Fits to the kinematic distributions of the data provide parameters describing the form factor of each mode. Combining the form factor results and R(0) gives |f(pi)(+)(0)|(2)|V(cd)|(2)/|f(K)(+)(0)|(2)|V(cs)|(2)=0.038(+0.006+0.005)(-0.007-0.003).     

Measurement of B(D+-->K(*0)l(+)nu(l))

Using 13.53 fb(-1) of CLEO data, we have measured the ratios of the branching fractions R(+)(e),R(+)(mu) and the combined branching fraction ratio R(+)(l), defined by R(+)(l)=[B(D+-->K(*0)l(+)nu(l))]/[B(D+-->K-pi(+)pi(+))]. We find R(+)(e)=0.74+/-0.04+/-0.05, R(+)(mu)=0.72+/-0.10+/-0.05, and R(+)(l)=0.74+/-0.04+/-0.05, where the first and second errors are statistical and systematic, respectively. The known branching fraction B(D+-->K-pi(+)pi(+)) leads to B(D+-->K(*0)e(+)nu(e))=(6.7+/-0.4+/-0.5+/-0.4)%, B(D+-->K(*0)mu(+)nu(mu))=(6.5+/-0.9+/-0.5+/-0.4)%, and B(D+-->K(*0)l(+)nu(l))=(6.7+/-0.4+/-0.5+/-0.4)%, where the third error is due to the uncertainty in B(D+-->K-pi(+)pi(+)).     

Evidence for the decay D0-->K(-)pi(+)pi(-)e(+)nu(e)

Using a 281 pb{-1} data sample collected at the psi(3770) with the CLEO-c detector, we present the first absolute branching fraction measurement of the decay D0-->K(-)pi(+)pi(-)e(+)nu(e) at a statistical significance of about 4.0 standard deviations. We find 10 candidates consistent with the decay D0-->K(-)pi(+)pi(-)e(+)nu(e). The probability that a background fluctuation accounts for this signal is less than 4.1 x 10{-5}. We find B(D0-->K(-)pi(+)pi(-)e(+)nu(e)) = [2.8{-1.1}{+1.4}(stat)+/-0.3(syst)]x10{-4}. By restricting the invariant mass of the hadronic system to be consistent with K1(1270), we obtain the product of branching fractions B(D{0}-->K{1}{-}(1270)e{+}nu{e})xB(K1-(1270)-->K{-}pi{+}pi{-})=[2.5{-1.0}{+1.3}(stat)+/-0.2(syst)]x10{-4}. Using B(K1-(1270)-->K{-}pi{+}pi{-})=(33+/-3)%, we obtain B(D{0}-->K{1}{-}(1270)e{+}nu{e})=[7.6{-3.0}{+4.1}(stat)+/-0.6(syst)+/-0.7]x10{-4}. The last error accounts for the uncertainties in the measured K1-(1270)-->K{-}pi{+}pi{-} branching fractions.     

Coincident fragment detection in strong field photoionization and dissociation of H2

Electron-ion momentum spectroscopy is used to investigate the correlated electronic and nuclear motion in fragmentation of H2 in 4 x 10(14) W/cm(2), 25 fs laser pulses at 795 nm. Reaction channel dependent photoelectron spectra indicate that besides the main, stepwise H2 ionization H2(+) dissociation mechanism resulting in the products H(1s) + H(+) + e(-) a second new mechanism has to be assumed. The momentum distribution of H(+) ions in the dissociation channels H(1s) + H(+) + e(-) and 2H(+) + 2e(-) is found to be independent of the kinetic energy of the photoelectrons.     

Study of the suppressed decays B- -->[K+pi-](D)K- and B- -->[K+pi-]Dpi-

We report a study of the suppressed decays B--->[K(+)pi(-)](D)K- and B--->[K(+)pi(-)](D)pi(-), where [K(+)pi(-)](D) indicates that the K+pi(-) pair originates from a neutral D meson. These decay modes are sensitive to the unitarity triangle angle varphi(3). We use a data sample containing 275 x 10(6) BB pairs recorded at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric e(+)e(-) storage ring. The signal for B--->[K(+)pi(-)](D)K- is not statistically significant, and we set a limit r(B)<0.27 at 90% confidence level, where r(B) is the magnitude of the ratio of amplitudes |A(B--->D 0K-)/A(B--->D0K-)|. We observe a signal with 6.4sigma statistical significance in the related mode, B--->[K(+)pi(-)](D)pi(-).     

Measurement of direct photon emission in K+-->pi(+)pi(0)gamma decay

We have performed a measurement of the K+-->pi(+)pi(0)gamma decay and have observed 2x10(4) events. The best fit to the decay spectrum gives a branching ratio for direct photon emission of (4.7+/-0.8+/-0. 3)x10(-6) in the pi(+) kinetic energy region of 55 to 90 MeV and requires no component due to interference with inner bremsstrahlung.     

Observation of accurate ion dissociation thresholds in pulsed field ionization-photoelectron studies

We report the first observation, together with a mechanism for such an observation, of a steplike feature in the pulsed field ionization photoelectron measurement of CH4(C2H2), marking the 0 K dissociation threshold for the formation of CH3(+) + H(C2H(+) + H) from CH4(C2H2). The nonexistence of a step in the spectrum for C 2H4 at its dissociation threshold for C2H2(+) formation provides strong support for the proposed mechanism. This experiment shows that, for a range of molecules, where the ion dissociation lifetimes near the dissociation thresholds are <10(-7) s, pulsed field ionization photoelectron measurements will yield not only highly accurate ionization energies, but also 0 K dissociation thresholds.     

Search for the rare decays B-->Kl(+)l(-) and B-->K(*)l(+)l(-)

We present results from a search for the flavor-changing neutral current decays B-->Kl(+)l(-) and B-->K(*)l(+)l(-), where l(+)l(-) is either an e(+)e(-) or mu(+)mu(-) pair. The data sample comprises 22.7 x 10(6) Upsilon(4S)-->B(-)B decays collected with the BABAR detector at the PEP-II B Factory. We obtain the 90% C.L. upper limits B(B-->Kl(+)l(-))<0.51 x 10(-6) and B(B-->K(*)l(+)l(-))<3.1 x 10(-6), close to standard model predictions for these branching fractions. We have also obtained limits on the lepton-family-violating decays B-->Ke+/-mu(-/+) and B-->K(*)e(+/-)mu(-/+).     

Muonium emission into vacuum from mesoporous thin films at cryogenic temperatures

We report on muonium (Mu) emission into vacuum following μ(+) implantation in mesoporous thin SiO(2) films. We obtain a yield of Mu into vacuum of (38±4)% at 250 K and (20±4)% at 100 K for 5 keV μ(+) implantation energy. From the implantation energy dependence of the Mu vacuum yield we determine the Mu diffusion constants in these films: D(Mu)(250 K)=(1.6±0.1)×10(-4) cm(2)/s and D(Mu)(100 K)=(4.2±0.5)×10(-5) cm(2)/s. Describing the diffusion process as quantum mechanical tunneling from pore to pore, we reproduce the measured temperature dependence ～T(3/2) of the diffusion constant. We extract a potential barrier of (-0.3±0.1) eV which is consistent with our computed Mu work function in SiO(2) of [-0.3,-0.9] eV. The high Mu vacuum yield, even at low temperatures, represents an important step toward next generation Mu spectroscopy experiments.     

Observation of exclusive B --> D(*)K(*-) decays

We report the first observation of the exclusive decays B-->D((*))K(*-), using 9.66 x 10(6) BB pairs collected at the Upsilon(4S) with the CLEO detector. We measure the following branching fractions: B(B--->D(0)K(*-)) = (6.1+/-1.6+/-1.7)x10(-4), B(B(0)-->D(+)K(*-)) = (3.7+/-1.5+/-1.0)x10(-4), B(B(0)-->D(*+)K(*-)) = (3.8+/-1.3+/-0.8)x10(-4), and B(B--->D(*0)K(*-)) = (7.7+/-2.2+/-2.6)x10(-4). The B-->D(*)K(*-) branching ratios are the averages of those corresponding to the 00 and 11 helicity states. The errors shown are statistical and systematic, respectively.     

EPR in LiTbF4 using an HCN laser

The Tb³⁺ electron paramagnetic resonances of a spherically shaped LiTbF₄ single crystal were measured with the static magnetic field along the c-axis, using an HCN laser at 890.8 and 964.3 GHz. At 4.2 K the measured spectrum consists of four hyperfine lines which have a spacing of 25.0± 0.2 mT and a width of roughly 10 mT. The g-factor is 17.75 ± 0.1 at both frequencies. In each hyperfine line of the spectrum at 4.2 K a superimposed structure is seen. This structure is explained by changes in the dispersion of the LiTbF₄ crystal.     

Direct measurement of a pure rotation transition in H2(+)

The N = 1<--0 pure rotation transition in the nu = 19 level of the ground electronic state of H2(+) was observed at 14,961.7+/-1.1 MHz. Recent theory predicts significant electric dipole intensity in forbidden rotation and rotation-vibration transitions involving levels near the dissociation limit; the relevant levels are bound by only 0.74 and 0.22 cm(-1). The transition was predicted to have a transition moment of 0.42 D; our measurement is consistent with this value.     

Effects of Gd<Superscript>3+</Superscript> doping on structural and dielectric properties of PZT (Zr:Ti = 52:48) piezoceramics

The purpose of this research is to study the effect of doping Gd into Pb(Zr_0.52Ti_0.48)O₃ ceramics prepared by solid state reaction. X-ray diffraction patterns show that all PGZT samples are of tetragonal structure and the highest doping should be no more than 2 mole % Gd at which the unreacted oxides start to appear. The electron spin resonance (ESR) spectra of PGZT's indicate that Gd³⁺ can enter both A site of the perovskite structure instead of only A site as widely believed. The ESR peaks resonance shift towards low fields as the concentration is higher, which is due to the change in crystal field experienced by Gd³⁺ ions. At x =0.001, 0.005 and 0.01 dopings, two sets of powder ESR signals arising from Gd³⁺ (4f⁷, spin 7/2) ions at A site. The first set shows some fine structure having strong absorption peaks centered at 76.26 mT (g = 8.550). The second is a seven-peak spectrum centered at 206.01 mT (g = 3.165), which belongs to the Gd³⁺ ions at B sites. Furthermore, the overlapped ESR strong absorption peaks from 309.17 mT to 314.49 mT (g = 2.2818-2.1087) belong to Gd³⁺ of unreacted Gd₂O₃. The local environments of Gd³⁺ ions were verified from the calculated ESR spectra using appropriate spin Hamiltonian parameter, i.e. gyromagnetic tensor g, zero-field splitting D and hyperfine tensor A.     

Double-electron transfer in H(-) + H(+) collisions

Absolute cross sections for double-electron transfer in H(-) + H(+) collisions have been measured for center-of-mass energies from 0.5 to 12 keV. Clear oscillations in the cross section are observed shedding new light on earlier measurements. Calculations based on a diabatic approach are shown to reproduce this behavior, but require a larger diabatic ion-pair splitting than previously assumed.     

ZnS:Ag的ESR及结构相变研究

ESR实验表明Ag在ZnS微晶中是以Ag⁺离子的形式存在,没有测到Ag²⁺离子的信号.以Mn²⁺为探针的ESR和X射线衍射分析研究发现,在ZnS微晶由立方点阵(β相)变为六角点阵(α相)的结构相变中,Ag⁺离子对相变的影响与掺杂浓度和煅烧温度有关,当掺Ag量为5×10^-4g/g时相变在1100~1200℃出现逆转现象.由Mn²⁺的ESR谱得出α相的朗德因子g为2.006,越精细常数a为6.76mT,β相的g为2.002,a为6.81mT.     

Observation of B(+)-->phiphiK(+) and evidence for B(0)-->phiphiK(0) below eta(c) threshold

We report measurements of the decays B(+)-->phiphiK(+) and B(0)-->phiphiK(0) using a sample of 231 x 10(6) BB pairs collected with the BABAR detector at the PEP-II asymmetric-energy B factory at the Stanford Linear Accelerator Center. The branching fractions are measured to be B(B(+)-->phiphiK(+))=(7.5+/-1.0(stat)+/-0.7(syst)) x 10(-6) and B(B(0)-->phiphiK(0))=(4.1(-1.4)(+1.7)(stat)+/-0.4(syst)) x 10(-6) for a phiphi invariant mass below 2.85 GeV/c(2).     

Ni(C3H10N2)2NO2(ClO4)晶体的ESR研究

报道了Ni(C₃H₁₀N₂)₂NO₂(ClO₄)晶体在T=1.5K温度和W波段的ESR实验.建立了d⁸离子基态³A₂(F)的零场分裂参量D,E,和g因子与斜方对称晶场势参量间的关系,并应用于Ni(C₃H₁₀N₂)₂NO₂(ClO₄)晶体.计算值与实验数据符合很好,表明所给关系式是合理的.     

Search for B+/--->[K(-/+)pi(+/-)](D)K+/- and upper limit on the b-->u amplitude in B+/--->DK+/-

We search for B+/--->[K(-/+)pi(+/-)](D)K+/- decays, where [K(-/+)pi(+/-)](D) indicates that the K-/+pi(+/-) pair originates from the decay of a D0 or D (0). Results are based on 120x10(6) Upsilon(4S)-->BB decays collected with the BABAR detector at SLAC. We set an upper limit on the ratio R(Kpi) identical with[Gamma(B+-->[K(-)pi(+)](D)K+)+Gamma(B--->[K(+)pi(-)](D)K-)][Gamma(B+-->[K(+)pi(-)](D) / K+)+Gamma(B--->[K(-)pi(+)](D)K-)]<0.026 (90% C.L.). This constrains the amplitude ratio r(B) identical with|A(B--->D 0K-)/A(B--->D0K-)|<0.22 (90% C.L.), consistent with expectations. The small value of r(B) favored by our analysis suggests that the determination of the Cabibbo-Kobayashi-Maskawa phase gamma from B-->DK will be difficult.