Line Intensities in the ν1, ν3, and 2ν2 Bands of H2Se

Using a high-resolution Fourier transform spectrum of hydrogen selenide in natural abundance, about 600 intensities of lines belonging to the ν₁, ν₃, and 2ν₂ bands of H₂⁸⁰Se were measured. A least-squares fit of these intensities was performed, allowing determination of the vibrational transition moments of these bands and their rotational corrections. Finally, the first derivatives of the dipole moment with respect to the normal coordinates q₁ and q₃ were found to be ∂μ_χ/∂q₁ = (−0.5938 ± 0.010) × 10⁻¹ and ∂μ_z/∂q₃ = (0.5683 ± 0.010) × 10⁻¹ Debye, respectively.     

Status of the CHORUS neutrino oscillation experiment

The CHORUS experiment is designed to search for ν_μ → ν_τ oscillation with a hybrid detector system containing 800 kg nuclear emulsions as target and vertex detector. Run I (320 000 recorded ν_μCC in 1994/5) and more than half of the run II (460 000 ν_μCC in 1996/7) data taking have been successfully completed. Approximately 80 000 events have been analyzed so far, searching for and τ⁻ → h⁻ (nπ⁰) ν_τ decays. No candidate has been found, leading to a limit sin² 2θ_μτ ≤ 4.5 10⁻³ for large Δm².     

New CP phase of – mixing on T violation in

A large CP-violating phase uncovered recently by CDF and DØ Collaborations in the time-dependent CP asymmetry (CPA) of the B_s→J/Ψ decay clearly indicates that a non-Cabibbo–Kobayashi–Maskawa (CKM) phase has to be brought into the b→s transition. We find that the model with SU(2)_L singlet exotic quarks cannot only provide the new phase induced from the Z-mediated flavor changing neutral current (FCNC) at tree level, but also strongly relate the B_s– mixing, B_q→V_qℓ⁺ℓ⁻ (V_d[s]=K^*[]) and B_s→μ⁺μ⁻ together. In particular, we show that the new CP phase can be unambiguously exposed by the large statistical significances of T violating observables in B_q→V_qℓ⁺ℓ⁻, while the branching ratio of B_s→μ⁺μ⁻ can be enhanced to be O(10⁻⁸).     

The bending energy levels of C2H2

Absorption spectra of C₂H₂ have been recorded between 50 and 1450 cm⁻¹, with a resolution always better than 0.005 cm⁻¹, using two different Fourier transform spectrometers. Analysis of the data provided two sets of results. First, the bending levels with Σ_t V_t(t = 4, 5) ≤ 2 were characterized by a coherent set of 34 parameters derived from the simultaneous analysis of 15 bands, performed using a matrix Hamiltonian. The following main parameters were obtained (in cm⁻¹): ω₄⁰ = 608.985196(14), ω₅⁰ = 729.157564(10); B₀ = 1.17664632(18), α₄ = −1.353535(86) × 10⁻³, α₅ = −2.232075(40) × 10⁻³; q₄⁰ = 5.24858(12) × 10⁻³, and q₅⁰ = 4.66044(12) × 10⁻³, with the errors (1σ) on the last quoted digit. Second, a more complete set of bending levels with Σ_t V_t ≤ 4, some of which have never previously been reported, and also including V₂ = 1 have been fitted to 80 parameters. This simultaneous fit involved 43 bands and used the same full Hamiltonian matrix. Some perturbations which affect the higher excited levels are discussed.     

The Microwave Spectrum of m-Tolunitrile: Methyl Internal Rotation and N Nuclear Quadrupole Coupling

The microwave spectrum of m-tolunitrile (3-methylbenzonitrile, m-C₆H₄CH₃CN) has been investigated in the frequency range from 1 to 4 and 8 to 26.5 GHz. The spectra in the two lowest states of internal methyl rotation (m = 0, ±1) were recorded by means of pulsed molecular beam Fourier transform microwave (MB-FTMW) spectrometers. The interpretation of the spectra was based on an asymmetric frame–symmetric top Hamiltonian with inclusion of centrifugal distortion terms and first-order contributions from ¹⁴N nuclear quadrupole coupling. A least-squares analysis yielded the rotational constants A = 3295.9103(10) MHz, B = 1199.1188(2) MHz, C = 883.9223(1) MHz, all elements of the nuclear quadrupole coupling tensor χ_aa = −3.626(1) MHz, χ_bb = 1.684(1) MHz, χ_cc = 1.943(1) MHz, and χ_ab = −1.870(3) MHz, as well as the threefold barrier to internal rotation, V₃ = 14.2 cm⁻¹, and the angle between the internal rotor axis and the principal moment of inertia a axis, θ = 42.66°, using fixed values for the sixfold barrier term V₆ (−11 cm⁻¹) and the moment of inertia of the methyl top I_α (3.16 u Ų).     

KARMEN: Neutrino oscillation limits and new results with the upgrade

The neutrino experiment KARMEN is situated at the beam stop neutrino source ISIS which provides ν_μ's, ν_e's and from the π⁺−μ⁺-decay at rest. The oscillation channels ν_{μ → νe} and are investigated with a 56 t liquid scintillation calorimeter. No evidence for oscillations could be found with KARMEN, resulting in 90% CL exclusion limits of sin²(2Θ) < 8.5 · 10⁻³ ( ) and sin²(2Θ) < 4.0 · 10⁻² (ν_μ → ν_e) for Δm² > 100 eV². In 1996, the experiment has been upgraded by an additional veto counting system with a total coverage of 300 m². The new system allows the identification of cosmic muons in the vicinity of the detector. Vetoing these muons suppresses energetic neutrons from deep inelastic scattering of muons as well as from μ-capture by a factor of 40. Up to 1996, these neutrons represented the main background for oscillation search. The experimental sensitivity for will be significantly enhanced towards sin²(2Θ) 1.0 · 10⁻³ after a further measuring period of 2–3 years.     

Methyl and skeletal torsion interaction in methyl thiolfluoroformate

The microwave spectrum of methyl thiolfluoroformate (FCOSCH₃) is reported for the ground state and seven vibrational satellites. The methyl group is in the syn conformation to the carbonyl group. The dipole moment components are μ_a = 2.89(2) D, μ_b = 0.30(8) D, and μ_c = 0. Spacings of A and E levels due to methyl internal rotation are analyzed for the ground state, the first excited methyl torsional state, and the first excited skeletal torsional state. An anomalous sequence of A and E levels occurring in the latter satellite arises from torsional interaction, according to two-dimensional model calculations. Potential parameters consistent with the three observed level separations are V₃ = 304(5) cm⁻¹, V₆ = 23(1) cm⁻¹ for the methyl torsion and either k = 1.912 or k = 2.936 cm⁻¹ deg⁻² for the skeletal torsional force constant.     

Dispersive Estimates for Schrödinger Equations with Threshold Resonance and Eigenvalue

Let H=−Δ+V(x) be a three dimensional Schrödinger operator. We study the time decay in L^p spaces of scattering solutions e^−itHP_cu, where P_c is the orthogonal projection onto the continuous spectral subspace of L²(R³) for H. Under suitable decay assumptions on V(x) it is shown that they satisfy the so-called L^p-L^q estimates ||e^−itHP_cu||_p≤(4π|t|)^{−3(1/2−1/p)}||u||_q for all 1≤q≤2≤p≤∞ with 1/p+1/q=1 if H has no threshold resonance and eigenvalue; and for all 3/2<q≤2≤p<3 if otherwise.     

A 20 nm gate-length ultra-thin body p-MOSFET with silicide source/drain

As the scaling of CMOS transistors extends to the sub-20 nm regime, the most challenging aspect of device design is the control of the off-state current. The traditional methods for controlling leakage current via the substrate doping profile will be difficult to implement at these dimensions. A promising method for controlling leakage in sub-20 nm transistors is the reduction in source-to-drain leakage paths through the use of a body region which is significantly thinner then the gate length, with either a single or a double gate. In this paper we present ultra-thin body PMOS transistors with gate lengths down to 20 nm fabricated using a low-barrier silicide as the source and drain. Calixarene-based electron-beam lithography was used to define critical device dimensions. These transistors show 260 μ A μ m ^{− 1}on-current and on/off current ratios of 10⁶, for a conservative oxide thickness of 40 Å and | V_g − V_t| = 1.2 V. Excellent short-channel effect, with only 0.2 V reduction in | V_t| is obtained in devices with gate lengths ranging from 100 to 20 nm.     

Modelling the quark propagator

We are interested in developing covariant, confining, and asymptotically free models of hadrons. With this goal in mind we have carried out a study of dynamical chiral symmetry breaking without imposing the frequently used approximation α_s(−(p−k)²) α₅(−p_>²), where p_>² ≡ max(p², k²) for the running coupling constant in the quark Schwinger-Dyson equation. We present numerical results in Landau gauge and compare these with earlier results obtained when using this approximation. We see in this context that a gluon propagator which has the form 1/q⁴ in the infrared is too singular and must be regulated. We derive a suitably generalized expression for the pion decay constant f_π. With essentially one free parameter we are able to reproduce reasonable results for various physical quantities of interest including , and Λ_QCD.     

Study of radiative leptonic events with hard photons and search for excited charged leptons at GeV

During the last 1995 data acquisition period at LEP, the DELPHI experiment collected an integrated luminosity of 5.9 pb⁻¹ at centre-of-mass energies of 130 GeV and 136 GeV. Radiative leptonic events (e, μ, τ) with high energy photons were studied and compared to Standard Model predictions. The data were used to search for charged excited leptons decaying through an electromagnetic transition. No significant signal was found. From the search for pair produced excited leptons, the limits m_e^* > 62.5 GeV/c², m_μ^* > 62.6 GeV/c² and m_τ^* > 62.2 GeV/c² at 95% confidence level were established. For single excited lepton production, upper limits on the ratio λ/m_l^* of the coupling of the excited charged lepton to its mass were derived.     

An energy-momentum tensor in gauge theories

We consider the renormalization of the twist two, dimension four gauge invariant operator O_μν⁽¹⁾ = − F_μσF_νσ − g_{μν 0}. By using the general theory of renormalization of gauge invariant operators, we find the gauge noninvariant operator O⁽²⁾ with which it mixes. We construct a finite combination of O⁽¹⁾ and O⁽²⁾ and show that it is an acceptable energy momentum tensor for gauge theories. We compare our energy momentum tensor with that constructed by Freedman, Muzinich, and Weinberg.     

Update on the search for μ→ e oscillations by the 2 experiment

The neutrino experiment sets the most stringent exclusion limits for _μ→ _e oscillations. Analyzing the data set recorded from Feb.1997 up to March 2000 with the upgraded experimental configuration, the search of _e appearance via the p( _e, e⁺)n reaction yields no hints for neutrino oscillations. Applying a likelihood method to the measured event sample of 11 events (background expectation 12.3 events), we deduce an upper limit of sin² (2Θ) < 1.3 · 10⁻³ for large Δm² > 100 eV² and Δm² < 0.049 eV² for sin² (2Θ)=1.     

Kerr property of cubic K0.95Li0.05Ta0.60Nb0.40O3 single crystal

The Kerr (quadratic electro-optic) property of K_0.95Li_0.05Ta_0.60Nb_0.40O₃ was measured by using an automated scanning Mach–Zehnder interferometer. K_0.95Li_0.05Ta_0.60Nb_0.40O₃ has large Kerr effect with R₁₁ = 7.2 × 10⁻¹⁶ m²/V² and R₁₂ = −1.2 × 10⁻¹⁶ m²/V² at 632.8 nm near its phase-transition temperature. The dielectric and Kerr properties as function of temperature were also investigated, thus the quadratic polarization-optic coefficients were calculated. The values of g₁₁ and g₁₂ are 0.083 m⁴/C² and −0.014 m⁴/C², respectively, and do not depend on temperature within the measurement accuracy of 5%.     

predictions of PMNS and CKM angles

Generalizing a previous model to accommodate the third quark family and CP violation, we present a T^′ model which predicts tribimaximal neutrino (PMNS) mixings while the central predictions for quark mixings are |V_td/V_ts|=0.245 and |V_ub/V_cb|=0.237 with a predicted CP violating KM phase δ_KM=65.8°. All these are acceptably close to experiment, including the KM phase for which the allowed values are 63°<δ_KM<72°, and depend only on use of symmetry T^′×Z₂ to define the model and no additional parameters.     

Search for squark production in events with jets, hadronically decaying tau leptons and missing transverse energy at

A search for supersymmetric partners of quarks is performed in the topology of multijet events accompanied by at least one tau lepton decaying hadronically and large missing transverse energy. Approximately 1 fb⁻¹ of collision data from the Fermilab Tevatron Collider at a center of mass energy of 1.96 TeV recorded by the DØ detector is analyzed. Results are combined with the previously published DØ inclusive search for squarks and gluinos. No evidence of physics beyond the Standard Model is found and lower limits on the squark mass up to 410 GeV are derived in the framework of minimal supergravity with tanβ=15, A₀=−2m₀ and μ<0, in the region where decays to tau leptons dominate. Gaugino masses m_1/2 are excluded up to 172 GeV.     

Observation of χb production in the exclusive reaction ′→γγχb→γγ→γγ(eeorμμ−)

We report on the observation of 1 ³P_J (χ_b) production in the reaction ′→γχ_b→γγ→γγ(e⁺e⁻ or μ⁺μ⁻). The data were recorded with the nonmagnetic CUSB detector at the Cornell Electron Storage Ring, CESR. We observe 124 γγ events with either an electron or muon pair in the final state. In the γγ correlation plot about 40% of the events cluster around (120, 430) MeV.     

The sub-micrometer thickness n-InSb/i-GaAs epilayers for magnetoresistor applications at room temperatures of operation

Magnetotransport at fields up to 500 mT and LF-noise characteristics are reported for miniature magnetoresistors with ferrite concentrators based on Sn-doped n-InSb/i-GaAs heterostructures grown by MBE. The thickness of the InSb epilayers lie in the range 0.55–1.5 μm giving room temperature mobilities of 2.5–5.5 m² V⁻¹ s⁻¹ with carrier densities of (0.5–1.5)×10¹⁷ cm⁻³. The room temperature magnetoresistance (MR) for our two terminal devices could be as high as 115% at 50 mT which is comparable to the extraordinary MR (ExMR) recently reported in microscopic composite van der Pauw disks four terminal devices [Science 289 (2000) 1530]. In addition, a high signal-to-noise ratio and a good temperature stability of R(B)/R₀=0.5–0.83% K⁻¹ was observed for B<60 mT (below the saturation field B_sat for ferrite). Device resistance stability R₀(T) was equal to 0.27–0.66% K⁻¹ in zero field with a nominal device resistance R₀=197–224 Ω for DC currents in the range I=0.01–1.0 mA. The minimum detectable magnetic field is estimated from the reduced differential MR (∂R/∂B)/R=2000% T⁻¹ at B=31 mT and normalised 1/f current noise power spectral density measured at the same field. The resolution limit B_min=2.6 nT at 10² Hz and B_min=0.82 nT at 10³ Hz. These resolution limits are seven times better than those recently reported for the same material n-InSb/i-GaAs and ferrite fabricated Hall sensors [Magnetotransport and Raman characterization of n-InSb/i-GaAs epilayers, for Hall sensors applications over extremely wide ranges of temperature and magnetic field, Proceedings NGS 10, IPAP Conference Series 2, IPAP, Tokyo, 2001, pp. 151–154].     

The Electric Dipole and the Nuclear Quadrupole Moment of Methyl Bromide in the Ground Vibrational State

A set of high-resolution Stark measurements at millimeter-wave frequencies is reported for CH₃⁷⁹Br and CH₃⁸¹Br. These results are analyzed together with previous data available in the literature to find new sets of molecular (rotational, hyperfine, and dipole moments) constants for both isotopic species. A particular improvement is obtained in the evaluation of the dipole moments, whose values are μ(79) = 1.82171 (26) 0, μ(8l) = 1.82185 (26) D, and for the hyperfine-structure parameters, which are estimated by assuming the most recent model for centrifugal distortion (M. R. Aliev and J. T. Hougen, J. Mol. Spectrosc.106, 110-123 (1984)), obtaining eqQ⁷⁹₀ = 577.1088 (57) MHz, χ⁷⁹_J = −0.63 (16) kHz, χ⁷⁹_K = 12.6 (16) kHz and eqQ⁸¹₀ = 482.1030 (94) MHz, χ⁸¹_J = −0.57 (17) kHz, χ⁸¹_K = 9.3 (22) kHz.     

Limits on the neutrino magnetic moment from solar neutrino experiments

If neutrinos have non-vanishing mass and non-vanishing magnetic moments, then electron neutrinos emitted in nuclear reactions in the solar interior may undergo flavour oscillations, spin precession or resonant spin-flavour precession. Assuming equal values for the magnetic moments of all neutrino flavours and using the data from Homestake and SuperKamiokande we obtain an upper limit on the neutrino magnetic moment and find μ_νe ≤ (2.2 − 2.3) × 10⁻¹⁰μ_B, within four standard solar models. We also point out that this limit may be further reduced if the detector threshold energy for the ν_e,χe⁻ scattering is decreased.