Flavour physics and CP violation

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 → 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.     

Higher-order squeezing and sub-poissonian photon statistics in CARS and CAHRS

The Squeezing and sub-poissonian photon statistics of an optical field are a purely quantum mechanical phenomenon and has been accepted as means of achieving noise below the quantum shot-noise limit. The effect of higher-order squeezing and sub-poissonian nature of an optical field in coherent anti-Stokes Raman scattering (CARS) and coherent anti-Stokes hyper Raman scattering (CAHRS) are investigated under short-time approximation. The coupled Heisenberg equations of motion involving real and imaginary parts of the quadrature operators are established and solved under short-time scale. The dependence of squeezing on the number of photons is also investigated. It is also shown that higher-order squeezing allows a much larger fractional noise reduction than lower-order squeezing. The occurrence of amplitude squeezing effects of the radiation field in the fundamental mode is investigated in both the processes. The present work shows that squeezing is greater in CAHRS than the corresponding squeezing in CARS. It is also shown that squeezing is greater in stimulated process than corresponding squeezing in spontaneous interaction. The conditions for obtaining maximum and minimum squeezing are obtained. The photon statistics of the pump mode in the processes has also been investigated and found to be sub-poissonian in nature.     

The non-commutative oscillator, symmetry and the Landau problem

The isotropic oscillator on a plane is discussed where the coordinate and momentum space are both considered to be non-commutative. We also discuss the symmetry properties of the oscillator for three separate cases when the non-commutative parameters Θ and for x and p-space, respectively, satisfy specific relations. We compare the Landau problem with the isotropic oscillator on non-commutative space and obtain a relation between the two non-commutative parameters and the magnetic field of the Landau problem.     

Inequivalent Quantization in the Field of a Ferromagnetic Wire

We argue that it is possible to bind neutral atom (NA) to the ferromagnetic wire (FW) by inequivalent quantization of the Hamiltonian. We follow the well known von Neumann’s method of self-adjoint extensions (SAE) to get this inequivalent quantization, which is characterized by a parameter Σ∈ℝ(mod2π). There exists a single bound state for the coupling constant η ²∈[0,1). Although this bound state should not occur due to the existence of classical scale symmetry in the problem. But since quantization procedure breaks this classical symmetry, bound state comes out as a scale in the problem leading to scaling anomaly. We also discuss the strong coupling region η ²<0, which supports bound state making the problem re-normalizable.     

Role of Yb and Tm ions in upconversion emission of Tb under 798 and 980 nm laser excitations in Tb-Tm-Yb doped tellurite glass

Upconversion emission and energy transfer processes in singly, doubly and triply doped tellurite glasses have been studied under 798 and 980 nm laser excitations. Emissions have been observed at 482, 544, 584, 655 nm and at 477, 655, 698, 800 nm corresponding to Tb³⁺: ⁵D₄ → ⁷F₆, ⁷F₅, ⁷F₄, ⁷F_J (J = 0, 1, 2, 3) and Tm³⁺: ¹G₄ → ³H₆, ¹G₄ → ³F₄, ³F₃ → ³H₆, ³H₄ → ³H₆ transitions, respectively. Among Tm³⁺, Yb³⁺and Tb³⁺ ions only Tm³⁺ has a ground state absorption at 798 nm excitation due to ³H₄ ← ³H₆ transition. For 980 nm excitation only Yb³⁺ can absorb the incident radiation. However, for both types of excitations, emission from all the three ions Tb, Yb and Tm has been observed. Possible mechanisms are proposed as follows: under 798 nm excitation Tm³⁺ ions are excited which excite Yb³⁺ ions through energy transfer. Finally “cooperative energy transfer” from a pair of Yb³⁺ ions to Tm³⁺ and Tb³⁺ ions takes place. Under 980 nm excitation Yb³⁺ ions absorb the incident energy and excite Tm³⁺ and Tb³⁺ ions via cooperative energy transfer. Variation of emission intensity with the ion concentrations of Yb³⁺, Tm³⁺ and Tb³⁺ has been studied. The lifetime of the ¹G₄ level has also been measured.     

Synthesis and characterizations of water-based ferrofluids of substituted ferrites [Fe1−xBxFe2O4, B=Mn,Co (x=0–1)] for biomedical applications

Nanomagnetic particles have great potential in the biomedical applications like MRI contrast enhancement, magnetic separation, targeting delivery and hyperthermia. In this paper, we have explored the possibility of biomedical applications of [Fe_1−xB_xFe₂O₄, B=Mn, Co] ferrite. Superparamagnetic particles of substituted ferrites [Fe_1−xB_xFe₂O₄, B=Mn, Co (x=0–1)] and their fatty acid coated water base ferrofluids have been successfully prepared by co-precipitation technique using NH4OH/TMAH (Tetramethylammonium hydroxide) as base. In vitro cytocompatibility study of different magnetic fluids was done using HeLa (human cervical carcinoma) cell lines. Co²⁺-substituted ferrite systems (e.g. CoFe₂O₄) is more toxic than Mn²⁺-substituted ferrite systems (e.g. MnFe₂O₄, Fe_0.6Mn_0.4Fe₂O₄). The later is as cytocompatible as Fe₃O₄. Thus, Fe_1−xMn_xFe₂O₄ could be useful in biomedical applications like MRI contrast agent and hyperthermia treatment of cancer.     

Lewis acid-catalyzed one-pot, three-component route to chiral 3,3'-bipyrroles

3,3'-Bipyrroles 3 could be synthesized using a double Michael addition reaction involving diaroyl acetylene 1 and the appropriate 1,3-dicarbonyls 2 using ammonium acetate as a nitrogen source. The axial chirality of bipyrrole was anticipated from the X-ray crystal structure and DFT calculations and confirmed by separating the racemates on a chiral column and subsequent CD spectra of the enantiomers. The absolute configuration of the enantiomers was achieved by theoretical CD spectra calculation using the ZINDO method.