A theoretical study of structural, elastic and thermal properties of heavy lanthanide monoantimonides

The structural, elastic and thermal properties of three heavy monoantimonides of holmium, erbium and thulium (LnSb, Ln=Ho, Er and Tm) have been investigated theoretically by using an interionic potential theory consisting of long-range Coulomb, short-range repulsive and van der Waal’s (vdW) interactions. These compounds exhibit first-order crystallographic phase transition from their initial NaCl-type structure to CsCl-type structure at pressures 27, 33.2 and 29.8 GPa for HoSb, ErSb and TmSb, respectively. The values of elastic constants and Debye temperatures as a function of pressure are also reported. The elastic properties such as Young modulus (E), Shear modulus (G), Poisson ratio (υ) and anisotropic ratio (A) in an NaCl-type structure are also predicted.     

Seesaw induced electroweak scale, the hierarchy problemand sub-eV neutrino masses

We describe a model for the scalar sector where all interactions occur either at an ultra-high scale, Λ_U~10¹⁶-10¹⁹ GeV, or at an intermediate scale, Λ_I = 10⁹-10¹¹ GeV. The interaction of physics on these two scales results in an SU(2) Higgs condensate at the electroweak (EW) scale, Λ_EW, through a seesaw-like Higgs mechanism, , while the breaking of the SM SU(2) x U(1) gauge symmetry occurs at the intermediate scale Λ_I . The EW scale is, therefore, not fundamental but is naturally generated in terms of ultra-high energy phenomena and so the hierarchy problem is alleviated. We show that the class of such "seesaw Higgs" models predict the existence of sub-eV neutrino masses which are generated through a "two-step" seesaw mechanism in terms of the same two ultra-high scales: . The neutrinos can be either Dirac or Majorana, depending on the structure of the scalar potential. We also show that our seesaw Higgs model can be naturally embedded in theories with tiny extra dimensions of size fm, where the seesaw induced EW scale arises from a violation of a symmetry at a distant brane; in particular, in the scenario presented there are seven tiny extra dimensions. Received: 19 August 2004, Revised: 27 July 2005, Published online: 14 October 2005     

Search for lepton flavor violating decays tau+/--->l+/-omega

A search for lepton flavor violating decays of a tau to a lighter-mass charged lepton and an omega vector meson is performed using 384.1 fb(-1) of e(+)e(-) annihilation data collected with the BABAR detector at the Stanford Linear Accelerator Center PEP-II storage ring. No signal is found, and the upper limits on the branching ratios are determined to be B(tau(+/-)-->e;{+/-}omega)<1.1 x10 (-7) and B(tau(+/-)-->micro(+/-)omega)<1.0 x 10(-7) at 90% confidence level.     

Evidence for CP violation in B0-->J/psipi0 decays

We present measurements of the branching fraction and time-dependent CP asymmetries in B0-->J/psipi0 decays based on 466 x 10(6) Upsilon(4S)-->BB over events collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. We measure the CP asymmetry parameters S= -1.23+/-0.21(stat)+/-0.04(syst) and C= -0.20+/-0.19(stat)+/-0.03(syst), where the measured value of (S, C) is 4.0 standard deviations from (0, 0) including systematic uncertainties. The branching fraction is determined to be B(B0-->J/psipi0)=[1.69+/-0.14(stat)+/-0.07(syst)]x10(-5).     

Measurement of the CP asymmetry in b-->sgamma using a sum of exclusive final states

We perform a measurement of the CP asymmetry in b-->sgamma decays using a sample of 383 x 10(6) B[over] B events collected by the BABAR detector at the SLAC PEP-II asymmetric B factory. We reconstruct 16 flavor-specific B decay modes containing a high-energy photon and a hadronic system X_(s) containing an s quark. We measure the CP asymmetry to be -0.011+/-0.030(stat)+/-0.014(syst) for a hadronic system mass between 0.6 and 2.8 GeV/c(2).     

Heavy Majorana neutrinos in the effective Lagrangian description: Application to hadron colliders

We consider the effects of heavy Majorana neutrinos N with sub-TeV masses and argue that the mere observation of these particles would be a signal of physics beyond the minimal seesaw mechanism. We describe the N interactions using an effective Lagrangian and exhibit the complete set of effective operators of dimension 6 involving the N and Standard Model fields. We argue that these interactions can be relatively easy to track at high-energy colliders. For example, we find that new physics (beyond the N) at the TeV-scale can yield thousands of characteristic same-sign lepton number violating ℓ⁺ℓ⁺jj events (j = light jet) at the LHC if m_N600 GeV, which can also have a distinctive forward-backward asymmetry signal; even the Tevatron has good prospects for this signature if m_N300 GeV.     

2p3/2?13x?1?3x?13d?1 X-ray satellites spectra in the Lα1 region of 4d transition elements

The X-ray satellite spectra arising due to 2p _3/2 ⁻¹3x ⁻¹−3x ⁻¹3d ⁻¹ (x ≡ s, p, d) transition array, in elements with Z = 40 to 48, have been calculated, using available Hartree-Fock-Slater (HFS) data on 1s ⁻¹−2p ⁻¹ 3x ⁻ and 2p _3/2 ⁻¹−3x ⁻¹,3x ⁻¹ Auger transition energies. The relative intensities of all the possible transitions have been estimated by considering cross — sections for the Auger transitions simultaneous to a hole creation and then distributing statistically the total cross sections for initial two hole states 2p _3/2 ⁻¹−3x ⁻¹ amongst various allowed transitions from these initial states to 3x ⁻¹ 3d ⁻¹ final states by Coster-Kronig (CK) and shake off processes. In both these processes initial single hole creation is the prime phenomenon. Each transition has been assumed to give rise to a Gaussian line and the overall spectrum has been computed as the sum of these Gaussian curves. The calculated spectra have been compared with the measured satellite energies in Lα₁ spectra. Their intense peaks have been identified as the observed satellite lines. The peaks in the theoretical satellite spectra were identified as the experimentally reported satellites α₃, α₄ and α₅, which lie on the high-energy side of the Lα₁ dipole line.     

The use of defocussed position of a Ronchi grating for evaluating the refractive index of lens

This report describes a Ronchi-grating shearing interferometric collimation method for determining the refractive index of a lens. A new formula has been deduced for the refractive index of the lens, which is independent of lens parameters. This newly developed device has two lenses. One of them collimates the light from a point source while the other acts as a decollimator. The point source acting as a test target is situated in the front focal plane of the collimator. The test lens is placed inside a glass cell in the back focal plane of the collimator. The Ronchi grating is exactly placed in the back focal plane of the decollimator, and a fringe-free space is observed in the common region. When the test lens is immersed in a liquid cell, it disturbs the focal point and hence interference fringes are observed. The combined system consisting of the test lens and the decollimator is moved to bring the focal point on the Ronchi grating. Thus, the difference between the two settings gives the amount of defocusing.