• Issue front cover thumbnail

      Volume 74, Issue 5

      May 2010,   pages  675-855

    • Flavour physics and CP violation

      Rukmani Mohanta Anjan Kumar Giri

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      It is well known that the study of flavour physics and CP violation is very important to critically test the Standard Model and to look for possible signature of new physics beyond it. The observation of CP violation in kaon system in 1964 has ignited a lot of experimental and theoretical efforts to understand its origin and to look for CP violation effects in other systems besides the neutral kaons. The two 𝐵-factories BABAR and BELLE, along with other experiments, in the last decade or so made studies in flavour physics and CP violation a very interesting one. In this article we discuss the status and prospectives of the flavour physics associated with the strange, charm and bottom sectors of the Standard Model. The important results in kaon sector will be briefly discussed. Recently, mixing in the charm system has been observed, which was being pursued for quite some time without any success. The smallness of the mixing parameters in the charm system is due to the hierarchical structure of the CKM matrix. Interestingly, so far we have not found CP violation in the charm system but in the future, with more dedicated experiments at charm threshold, the situation could change. Many interesting observations have been made in the case of bottom mesons and some of them show some kind of deviations from that of the Standard Model expectations which are mainly associated with the $b \rightarrow s$ flavour changing neutral current transitions. It is long believed that the $B_{s}$ system could be the harbinger of new physics since it is a system in which both bottom and strange quarks are the constituents. Recently, D0 and CDF announced their result for the $B_{s}$ mixing which is claimed to be the first possible new physics signature in the flavour sector. We plan to touch upon all important issues pointing out both theoretical and experimental developments and future prospects in this review article.

    • Robust chaos synchronization using input-to-state stable control

      Choon Ki Ahn

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      In this paper, we propose a new input-to-state stable (ISS) synchronization method for a general class of chaotic systems with disturbances. Based on Lyapunov theory and linear matrix inequality (LMI) approach, for the first time, the ISS synchronization controller is presented not only to guarantee the asymptotic synchronization but also to achieve the bounded synchronization error for any bounded disturbance. The proposed controller can be obtained by solving a convex optimization problem represented by the LMI. Simulation studies are presented to demonstrate the effectiveness of the proposed ISS synchronization scheme.

    • Beam-induced radiation in the compact muon solenoid tracker at the Large Hadron Collider

      A P Singh P C Bhat N V Mokhov S Beri

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      The intense radiation environment at the Large Hadron Collider, CERN at a design energy of $\sqrt{s} = 14$ TeV and a luminosity of 1034 cm−2S−1 poses unprecedented challenges for safe operation and performance quality of the silicon tracker detectors in the CMS and ATLAS experiments. The silicon trackers are crucial for the physics at the LHC experiments, and the inner layers, being situated only a few centimeters from the interaction point, are most vulnerable to beam-induced radiation. We have recently carried out extensive Monte Carlo simulation studies using MARS program to estimate particle fluxes and radiation dose in the CMS silicon pixel and strip trackers from proton–proton collisions at $\sqrt{s} = 14$ TeV and from machine-induced background such as beam–gas interactions and beam halo. We will present results on radiation dose, particle fluxes and spectra from these studies and discuss implications for radiation damage and performance of the CMS silicon tracker detectors.

    • A comparative study of model ingredients: Fragmentation in heavy-ion collisions using quantum molecular dynamics model

      Sanjeev Kumar Suneel Kumar

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      We aim to understand the role of NN cross-sections, equation of state as well as different model ingredients such as width of Gaussian, clusterization range and different clusterization algorithms in multifragmentation using quantum molecular dynamics model. We notice that all model ingredients have sizable effect on the fragment pattern.

    • Analysis of pulsed wire method for field integral measurements in undulators

      Vinit Kumar Ganeshwar Mishra

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      Pulsed wire technique is a fast and accurate method for the measurement of first and second field integrals of undulators used in free-electron lasers and synchrotron light sources. In this paper, we present a theoretical analysis of this technique by finding out the analytic solution of the differential equation for the forced vibration of the wire taking dispersion due to stiffness into account. Method of images is used to extend these solutions to include reflections at the ends. For long undulators, the effect of dispersion of the acoustic wave in the wire could be significant and our analysis provides a method for the evaluation of the magnetic field profile even in such cases taking the effect due to dispersion into account in an exact way.

    • Absolute parametric instability of low-frequency waves in a 2D nonuniform anisotropic warm plasma

      N G Zaki

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      Using the separation method, absolute parametric instability (API) of electrostatic waves in a magnetized pumped warm plasma is investigated. In this case the effect of static strong magnetic field is considered. The problem of strong magnetic field is solved in two-dimensional (2D) nonuniform plane plasma. Equations which describe the spatial part of the electric potential are obtained. Also, the growth rates and conditions of the parametric instability for periodic and aperiodic cases are obtained. It is found that the spatial nonuniformity of the plasma exerts a stabilizing effect on the API. It is shown that the growth rates of periodic and aperiodic API in warm plasma are less when compared to that in cold plasma.

    • Molecular conformation and liquid structure of 2-propanol through neutron diffraction

      A Sahoo S Sarkar P S R Krishna R N Joarder

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      The neutron diffraction data analysis of deuterated liquid 2-propanol at room temperature to define its molecular conformation is presented. 2-Propanol being a large molecule with twelve atomic sites, the conformation analysis is tricky and an improved method of data analysis is given. The intermolecular structural correlations, i.e., hydrogen-bonded liquid structure, can be modelled accurately to extract the nature of the average hydrogen-bonded molecular association in liquid state at room temperature. Like other alcohols these are mostly hexamer ring chain (HRC) clusters. The cluster analysis of recent X-ray data available in the literature also support the same liquid structure.

    • A linear polymerized photopolymer orienting a nematic liquid crystal within nonextensive formalism

      Ozhan Kayacan

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      The distribution function of photogenerated cross-links in thin films of poly(vinyl cinnamate) or poly(vinyl 4-methoxy-cinnamate) is investigated within nonextensive statistics, in terms of the irradiation time of these films with linearly polarized UV light. The scalar order parameter is obtained from the generalized distribution function, and is compared to the measured birefringence for some values of the entropic index q. The exposure time dependence of the nematogen scalar order parameter is plotted, and the effect of the nonextensive formalism on its exposure time dependence is presented.

    • Harmonic dynamical behaviour of thallous halides

      Sarvesh K Tiwari L J Shukla K S Upadhyaya

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      Harmonic dynamical behaviour of thallous halides (TlCl and TlBr) have been studied using the new van der Waals three-body force shell model (VTSM), which incorporates the effects of the van der Waals interaction along with long-range Coulomb interactions, three-body interactions and short-range second neighbour interactions in the framework of rigid shell model (RSM). Phonon dispersion curves (PDC), variations of Debye temperature with absolute temperature and phonon density of state (PDS) curves have been reported for thallous halides using VTSM. Comparison of experimental values with those of VTSM and TSM are also reported in the paper and a good agreement between experimental and VTSM values has been found, from which it may be inferred that the incorporation of van der Waals interactions is essential for the complete harmonic dynamical behaviour of thallous halides.

    • Transmission gaps in one-dimensional Fibonacci quasiperiodic structure containing epsilon-negative materials

      Hadi Rahimi Abdolrahman Namdar Samad Roshan Entezar Habib Tajalli

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      We investigate the transmission properties of one-dimensional Fibonacci quasiperiodic structure consisting of dispersive and lossless epsilon-negative (ENG) materials. It is found that for both TE and TM polarizations with normal and oblique incidences, there exist transmission gaps which are invariant with a change of scale and sensitive to incident angles. Analytical methods based on transfer matrices and effective medium theory have been used to explain the properties of transmission gaps.

    • Synthesis and characterization of germanium monosulphide (GeS) single crystals grown using different transporting agents

      G K Solanki Dipika B Patel Sandip Unadkat M K Agarwal

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      This paper reports the growth of germanium monosulphide (GeS) single crystals by vapour phase technique using different transporting agents. The single crystallinity and composition of the grown crystals have been verified by transmission electron microscopy (TEM) and energy dispersive analysis of X-rays (EDAX) respectively. Resistivity measurements have been carried out in different temperature ranges. Transport parameters, e.g. resistivity, Hall coefficient, carrier concentration and mobility have been measured at varying magnetic fields. All the experimental results have been explained.

    • Fabrication of single-grain GdBa2Cu3O$_{7−x}$ bulk superconductors with a new kind of liquid source by the top seeded infiltration and growth technique

      Guo-Zheng Li Wan-Min Yang Xiao-Fang Cheng Jing Fan Xiao-Dan Guo

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      Compared to the conventional melt growth (MG) method, the top seeded infiltration and growth (TSIG) process is an effective way for preparing bulk REBa2Cu3O$_{7−x}$ (RE-123) with finely dispersed RE2BaCuO5 (RE-211) particles. However, it is more complicated and time-consuming, because three kinds of precursor powders, namely, RE-211, RE-123 and BaCuO2, have to be prepared for the conventional TSIG process. In this paper, a new liquid source (NLS) composed of RE-211 and Ba3Cu5O8, was proposed for simplifying the TSIG process, which is different from the regular liquid source (RLS) composed of RE-123 and Ba3Cu5O8. In this modified TSIG technique, we need to prepare only RE-211 and BaCuO2 powders. Single-grain GdBa2Cu3O$_{7−x}$ (GdBCO) bulk super-conductors have been fabricated using the RLS and NLS separately. The morphology, microstructure and levitation force of the bulk GdBCO have also been investigated. The results indicate that the NLS can be used to simplify the process flow and improve the efficiency on the fabrication of single-grain GdBCO superconductors.

    • The effect of spin dilution on magnetism of the linear chain system 𝛽-Cu$_{2−x}$Zn$_{x}$V2O7

      S N Bhatia Niharika Mohapatra R Nirmala S K Malik

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      We have measured the magnetic susceptibility (𝜒) and heat capacity ($C_{p}$) of 𝛽-Cu$_{2−x}$Zn$_{x}$V2O7 ($x$ = 0, 0.05, 0.1, 0.15, 0.2, 0.3, 2) in the temperature range 2–300 K. A one-dimensional alternating exchange Heisenberg antiferromagnetism (HAF) is observed in all compositions with chains of infinite length. The intra-chain exchange remains uniform and decreases marginally with dilution of the magnetic state. A cooperative ordering is seen in the magnetic chains for all Zn concentrations ($x \leq 0.3$). The temperature of occurrence of this transition decreases with increasing Zn concentration. Though the conventional spin-wave theory has been used here to describe the properties of the ordered phase, the presence of some contributions like the lattice heat capacity in $C_{p}$ and the Curie–Weiss term in susceptibility introduces some uncertainties in the estimation of the proportions contributed by the spin system. Therefore, the nature of the ordered phase could not be ascertained unambiguously.

    • Molecular structure, vibrational spectroscopic studies and natural bond orbital analysis of 7-amino-4-trifluoromethyl coumarin

      M K Subramanian P M Anbarasan S Manimegalai

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      Quantum mechanical calculations of energies, geometries and vibrational wave numbers of 7-amino-4-trifluoromethyl coumarin (7A4TFMC) were carried out using Hartree–Fock (HF) and density functional theory (DFT) using hybrid functional BLYP and B3LYP with 6-31G(d,p) as basis set. The optimized geometrical parameters obtained by HF and DFT calculations are in good agreement with the experimental X-ray data. The best method to reproduce the experimental wave numbers is B3LYP method with the 6-31G(d,p) basis set. The difference between the observed and scaled wave number values of most of the fundamentals is very small. A detailed interpretation of the infrared spectra of 7A4TFMC was also reported. The entropy of the title compound was also performed at HF using the hybrid functional BLYP and B3LYP with 6-31 G(d,p) as basis set levels of theory. Natural bond orbital (NBO) analysis of the title molecule is also carried out. The theoretical spectrogram for FTIR spectra of the title molecule has been constructed.

    • Cohesive energy of zincblende (A$^{III}$ B$^{V}$ and A$^{II}$B$^{VI}$) structured solids

      A S Verma B K Sarkar V K Jindal

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      In this paper we present an expression relating the cohesive energy ($E_{\text{coh}}$ in kcal/mol) of A$^{III}$B$^{V}$ and A$^{II}$ B$^{VI}$ semiconductors with the product of ionic charges ($Z_{1}Z_{2}$) and nearest-neighbour distance d (Å). The cohesive energy values of these solids exhibit a linear relationship when plotted on a log–log scale against the nearest-neighbour distance 𝑑(Å), but fall on different straight lines according to the ionic charge product of the solids. A good agreement has been found between the experimental and calculated values of the cohesive energy of A$^{III}$B$^{V}$ and A$^{II}$B$^{VI}$ semiconductors.

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