Measurement of the beta beta-decay rate of 100Mo to the first excited 0(+) State of 100Ru

The double-beta beta beta(2 nu)-decay rate of 100Mo to the first excited 0(+) state of 100Ru has been measured by a gamma-gamma coincidence technique that uses two HPGe detectors to observe the two gamma rays ( E(gamma 1) = 590.76 keV; E(gamma 2) = 539.53 keV) from the 100Ru nucleus as it deexcites to the ground state via the 0(+)-->2(+)-->0(+) sequence. Unlike all previous beta beta-decay experiments, this technique provides data which have a large signal-to-background ratio. After a 440-day measurement of a 1.05-kg isotopically enriched (98.4%) disk of 100Mo, 22 detected coincidence events (with an estimated background of 2.5 events) yield a half-life of [5.9(+1.7)(-1.1)(stat)+/-0.6(syst)] x 10(20) years.     

Observation of B(+)-->pppi+, B0-->ppK0, and B(+)-->ppK(*+)

We report the first observation of a b-->u type charmless baryonic B decay, B+-->pppi(+), as well as b-->s type B0-->ppK0 and B+-->ppK(*+) decays. The analysis is based on a 78 fb(-1) data sample recorded on the Upsilon(4S) resonance with the Belle detector at KEKB. We find B(B+-->pppi(+))=(3.06(+0.73)(-0.62)+/-0.37)x10(-6), B(B0-->ppK0)=(1.88(+0.77)(-0.60)+/-0.23)x10(-6), and B(B+-->ppK(*+))=(10.3(+3.6+1.3)(-2.8-1.7))x10(-6). We also update B(B+-->ppK+)=(5.66(+0.67)(-0.57)+/-0.62)x10(-6) and present an upper limit on B(B0-->ppK(*0)) at the 90% confidence level. A common feature of the observed decay modes is threshold peaking in baryon pair invariant mass.     

J/ψ→∑0Σ0衰变研究（英文）

利用北京正负电子对撞机(BEPC)上的北京谱仪(BES)收集的7.8×106个J/Ψ事例,研究了J/Ψ→Σ0衰变.其衰变分支比为BR(J/Ψ→Σ0)=(0.97±0.04±0.24)×10-3,角分布具有dN/dcosθθ=N0(1+acos2θ)的形式,a值等于-0.21±0.27±0.13.     

High-Resolution Fourier Transform Emission Spectroscopy of the B(2)Sigma(+) (v = 0)-X(2)Sigma(+) (v = 0) Transition of the PN(+) Ion

Ultraviolet emission spectrum of the B(2)Sigma(+) (v = 0)-X(2)Sigma(+) (v = 0) transition of the PN(+) ion has been observed at a resolution of 0.05 cm(-1) by a Fourier transform spectrometer. The rotational analysis led to a great improvement of rotational constants in the B(2)Sigma(+) (v = 0) and X(2)Sigma(+) (v = 0) states as well as to the first determination of centrifugal distortion constants for both levels and spin-rotation interaction constant in the X(2)Sigma(+) (v = 0) state. Rotational perturbation in the B(2)Sigma(+) (v = 0) state was observed. Copyright 2000 Academic Press.     

Precise half-life measurement for the superallowed 0(+)-->0(+) beta emitter (74)Rb: first results from the new radioactive beam facility (ISAC) at TRIUMF

Presently, the world data for superallowed beta decay leads to a result in disagreement (at the 98% confidence level) with the predictions of the minimal standard model for the unitarity of the Cabibbo-Kobayashi-Maskawa matrix. Precise data for the superallowed 0(+)-->0(+) beta decay of (74)Rb would provide a critical test of the nucleus-dependent isospin symmetry-breaking corrections that must be calculated for these superallowed Fermi beta decays. The present work reports the first precise measurement of the half-life for (74)Rb ( t(1/2) = 64.761+/-0.031 ms). The data were obtained at the radioactive beam facility (ISAC) at TRIUMF using a beam of approximately 4000 (74)Rb ions s(-1).     

The KRb (2)(3)Sigma(+) Electronic State

High-resolution spectra of the (3)(1)Pi --> (2)(3)Sigma(+) system of the KRb molecule, obtained after excitation with fixed frequencies Ar(+) laser lines, were recorded on a Connes-type Fourier transform interferometer. Molecular constants of the first 14 vibrational levels of the (2)(3)Sigma(+) state are determined. The RKR potential energy curve is derived. The main spectroscopic constants for this triplet electronic state of the (39)K (85)Rb isotopic species are T(e) = 13 507.146(2) cm(-1), omega(e) = 48.6385(6) cm(-1), B(e) = 0.0254152(5) cm(-1), gamma = 0.00164(4) cm(-1), epsilon = -0.469(2) cm(-1), R(e) = 4.98345 ?, 𝒟(e) = 3447 cm(-1). Copyright 2000 Academic Press.     

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).     

Search for radiative penguin decays B(+)-->rho(+)gamma, B(0)-->rho(0)gamma, and B(0)-->omegagamma

A search for the decays B-->rho(770)gamma and B0-->omega(782)gamma is performed on a sample of 211 x 10(6) Upsilon(4S)-->BB events collected by the BABAR detector at the SLAC PEP-II asymmetric-energy e(+)e(-) storage ring. No evidence for the decays is seen. We set the following limits on the individual branching fractions: B(B+-->rho(+)gamma)<1.8 x 10(-6), B(B0-->rho(0)gamma)<0.4 x 10(-6), and B(B0-->omegagamma)<1.0 x 10(-6) at the 90% confidence level. We use the quark model to limit the combined branching fraction B [B-->(rho/omega)gamma]<1.2 x 10(-6), from which we determine a constraint on the ratio of Cabibbo-Kobayashi-Maskawa matrix elements |V(td)|/|V(ts)|.     

Double-Modulation Submillimeter-Wave Spectroscopy of HOC(+) in the nu(2) Excited Vibrational State

The submillimeter-wave rotational transitions of HOC(+) in the nu(2) excited state are first detected using the double-modulation method, and the precise transition frequencies and the much improved molecular constants are obtained. The measurements of the ground state HOC(+) and DOC(+) submillimeter-wave lines are extended up to the 840-GHz region. It is found that the higher order centrifugal distortion constant, H, is necessary to fit the observed transition frequencies to the experimental accuracy. Copyright 2000 Academic Press.     

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.     

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).     

Ultrahigh-Pressure Equation of State for Copper at 0K

Based on the first-principles all-electron full-potential augmented-plane-wave plus local orbital method, an equation of state （EOS） at OK for copper up to 10000 GPa （10^8 bar） is presented. Our recommended EOS is in good agreement with the available experimental data. Furthermore, the agreement between theoretical EOS of hcp and fcc lattices at extremely compressed condition sets the foundation of spherical atom models for high density and high temperate plasmas.     

Dalitz analysis of D0-->K(0)(S)pi(+)pi(-)

In e(+)e(-) collisions using the CLEO detector, we have studied the decay of the D0 to the final state K(0)(S)pi(+)pi(-) with the initial flavor of the D0 tagged by the decay D(*+)-->D0pi(+). We use the Dalitz technique to measure the resonant substructure in this final state and clearly observe ten different contributions by fitting for their amplitudes and relative phases. We observe a K(*)(892)(+)pi(-) component which arises from doubly Cabibbo suppressed decays or D0-D0; mixing.     

Dipole–Dipole Polarizability of the Cadmium 1S0 State Revisited

Optics and Spectroscopy - Experimental results and high-level quantum chemical ab initio calculations of the static polarizability α0 = α(ω = 0) of the cadmium 1S0 state are still in...     

Observation of CP violation in B(0) --> K(+)pi(-) and B(0) --> pi(+)pi(-)

We report observations of CP violation in the decays B(0) --> K(+)pi(-) and B(0) --> pi(+)pi(-) in a sample of 383 x 10(6) Upsilon(4S) --> BB[over] events. We find 4372+/-82 B(0) --> K(+)pi(-) decays and measure the direct CP-violating charge asymmetry A(Kpi) = -0.107+/-0.018(stat)(-0.004)(+0.007)(syst), which excludes the CP-conserving hypothesis with a significance of 5.5 standard deviations. In the same sample, we find 1139+/-49 B(0) --> pi(+)pi(-) decays and measure the CP-violating asymmetries S(pipi) = -0.60+/-0.11(stat)+/-0.03(syst) and C(pipi) = -0.21+/-0.09(stat)+/-0.02(syst). CP conservation in B(0) --> pi(+)pi(-) (S(pipi) = C(pipi) = 0) is excluded at a confidence level 1-C.L. = 8 x 10(-8), corresponding to 5.4 standard deviations.     

Study of B0 --> J/psiK(*)0pi(+)pi(-) decays with the collider detector at Fermilab

We report a study of the decays B0 --> J/psiK(*)0pi(+)pi(-), which involve the creation of a uu or dd quark pair in addition to a b -->c(cs) decay. The data sample consists of 110 pb(-1) of pp collisions at square root[s] = 1.8 TeV collected by the CDF detector at the Fermilab Tevatron collider during 1992-1995. We measure the branching fractions to be B(B0 --> J/psiK(*0)pi(+)pi(-)) = (6.6 +/- 1.9 +/- 1.1)x10(-4) and B(B0 --> J/psiK0pi(+)pi(-)) = (10.3 +/- 3.3 +/- 1.5)x10(-4). Evidence is seen for contributions from psi(2S)K(*)0, J/psiK0rho(0), J/psiK(*+)pi(-), and J/psiK1(1270).     

Lifetime Measurement of the Metastable 23 P 0 State in Helium-like 197Au

Hyperfine Interactions - The determination of atomic lifetimes offers the possibility to investigate various aspects of the atomic structure. In the case of helium-like 197Au with nuclear spin 3/2,...     

粲夸克偶素P波态χ_（c0）宽度测量

利用北京谱仪在北京正负电子对撞机上采集的３５０万（２Ｓ）事例，通过（２Ｓ）→γπ－和γＫ＋Ｋ－反应道测量了Ｘｃ０的总宽度．由ＭｏｎｔｅＣａｒｌｏ模拟给出的质量分辨函数，利用拟合Ｘｃ２谱形得到的质量分辨作标定后，用于Ｘｃ０宽度的拟合，得到Ｘｃ０的宽度为（１５．０）ＭｅＶ．同时定出了ＸｃＪ（Ｊ＝０，２）到π＋π＝和Ｋ＋Ｋ－的衰变分支比．结果为Ｂ（Ｘｃ０→π＋π－）＝（４．２７±０．２３±Ｏ．６０）×１０－３；Ｂ（Ｘｃ０→Ｋ＋Ｋ－）＝（３．４４±０．２１±０．４７×１０－３；Ｂ（Ｘｃ２→π＋π－）＝（１．５２±０．１７±０．２９）×１０－３和Ｂ（Ｘｃ２→Ｋ＋Ｋ－）＝（５．２±１．１±１．８）×１０－４，其中第一项误差为统计误差，第二项为系统误差。