Title : Development of an SDD based Large Area X-ray Spectrometer with ASIC readout for future planetary mission

Abstract

Silicon drift detector-based X-ray spectroscopy has been employed for applications varying from solar studies, XRF experiments, X-ray imaging to various astronomical observations. We propose developing a multi-detector large area X-ray spectrometer using Silicon Drift Detectors (SDD) for X-rays in the energy range of 500 eV to 15 KeV. Using discrete components for the application will lead to a bulky system and hence the miniaturized system is desired. In this direction, we propose to develop the spectrometer using Application-Specific Integrated Circuit (ASIC) based readout which can process the signal from multiple detectors simultaneously. The VERDI ASIC reads out the signals from 8 independent detectors with controllable thresholds, shaping time and gains for each channel. The characterization and the performance of the ASIC will be discussed in the seminar.

Title : Cwebs beyond three loops in multiparton amplitudes

Abstract

The correlators of Wilson-line operators are fundamental objects for the study of the infrared properties in QCD and other non-abelian gauge theories. In perturbation theory, they are known to exponentiate, and their logarithm can be organized in terms of collections of Feynman diagrams called webs. In this talk, I will discuss some recent results regarding their organization at higher perturbative orders, determination of the colour structures that contribute to the soft anomalous dimension, and a new method of constructing the web mixing matrices.

Title : Hot Spring Mineral Assemblage on Earth: Implication and Linkage to Mars

Abstract

Hot spring localities on continents may represent the most likely locales for the formation of early life components on Earth. Apart from liquid water, an oxygenated atmosphere and carbohydrates, these components also include elements like boron that are crucial for stabilization of the complex organic molecules that constitute life. In this Context, characterization of the complete mineralogical assemblage of the Puga hot spring deposit, Ladakh, India, using detailed spectroscopic and X-ray diffraction studies have been done. This study has an importance for future detection of similar mineralogical assemblage on Mars using state of the art instruments on-board Perseverance Rover. Future work using various instruments of the Perseverance rover will be helpful for search for biosignature on Mars (which is one of the major science objective of the Rover mission). Earth based analog studies hold a key for future sensor development and finally for identification and characterization of the related minerals on Mars.

Title : Primordial noble gas component hosted by water-susceptible materials in less-altered CR chondrites

Abstract

Previous studies of noble gases in primitive meteorites have focused primarily on acid-resistant phases that contain most of the noble gases in the primitive meteorites. However, a new Ne-rich noble gas component hosted by water-susceptible materials was recently found in some aqueously less-altered CR chondrites. In this seminar, I will talk about the potential relationship between the Ne-rich materials in CR chondrites and cometary materials. The talk also briefly introduces basic knowledge of noble gases in primitive meteorites and why noble gases are unique tracers in cosmochemistry.

Title : Beyond Standard Model : A left-right theory approach

Abstract

In spite of being a successful theory, the Standard Model (SM) has several shortcomings. All these limitations of the SM give a clear hint of Beyond SM (BSM) physics and Left-Right (LR) theories are one of the successful BSM scenarios to provide a unified explanation to the origin of small neutrino mass and low-energy parity violation in weak phenomenology. The spontaneous breakdown of LR symmetry to SM can be achieved via the vacuum expectation values (vevs) of either (i) bidoublet + triplet Higgs, or (ii) bidoublet + doublet Higgs or (iii) combination of both (i) and (ii). We have considered such several variants of Higgs sectors in LR symmetry and studied certain phenomenological and cosmological signatures of these frameworks. Moreover, another approach to conventional LRSM, aka, ALRM can evade unavoidable FCNC constraints naturally. We have explored one of such ALRMs where we have studied the possibility of having significant contribution to neutrinoless double beta decay as well as low-scale leptogenesis.

Title : Disorder, strong correlations and unconventional superconductors

Abstract

Unconventional superconductivity is one of the key areas of research for past several decades, either due to high transition temperatures or due to exotic superconducting states with novel topological properties. Most of the unconventional superconductors are intrinsically dirty. They carry lots of impurities, therefore, relevant to this discussion is disorder that always exists in these systems. Here I will review the seminal work by Abrikosov and Gorkov that is widely used to understand the disorder effects in superconductors. I will then discuss the limitation of the Abrikosov-Gorkov theory in the case of electronic pairing. I will present some of my new results showing the effect of strong correlation on impurity scattering in d-wave superconductors that are relevant for cuprates. I will also discuss the implications of realistic impurities

Title : Isotopic variations of Carbon and Nitrogen in IAB iron meteorites

Abstract

The process of formation of IAB iron meteorites is still unclear, and many hypotheses have been put forward to explain the unique trace elemental and morphological trends in them. Hf-W ages after GCR correction suggest that, IAB parent body accreted about 3-5 Mya post CAI’s, which is old for widespread melting by 26Al nuclides, but makes impact melting a strong candidate. Our analysis was carried out on Kendall County meteorite sample mapped under SEM and analysed for δ13C under the Camera nano-SIMS 50. Graphite shows a range of different morphologies, in different host phases within the metal matrix. We made carbon isotope measurements on graphite, inside Troilite (FeS) and Schreibersite (Fe3P) and the metal matrix Kamacite/Taenite (Fe-Ni alloy) and also the metal surrounding the graphites. Our data conforms to the presence of unequilibrated primitive δ13C in graphites ranging from 4‰ to -21‰. We simulated two models based on Fast cooled kinetic fractionation and Rayleigh fractionation method respectively and tried to compare our data to these simulations. Using the simulated data and SIMS data we discuss the various parameters that might be influencing the δ13C of IAB irons, the petrology of the graphites and draw conclusion about the early solar system.

Title : New Insights into Glaciation and Gully Formation in the Mid-latitudes of Mars: A remote sensing perspective

Abstract

Late Amazonian geological history of mid-latitudes of Mars is dominated by a suite of landforms that substantiate geologically recent surface – atmosphere exchange of ice. In our study, we have investigated two of the most popular landforms: glaciers and gullies. We have used remote sensing datasets to examine the role they have played in modification of the Mars’ surface during the past few million years to hundreds of millions of years. Our observations and analysis have revealed (1) Glaciers and gullies, both common in the mid-latitudes, have been spatiotemporally related as implied by glaciation, followed by cyclic emplacement and removal of LDM cover, and subsequent formation of gullies on surfaces with and without LDM/glacial deposits. (2) The unique morphological and morphometric characteristics of alcoves and fans that we report on here do present evidence for a widespread occurrence of recent terrestrial debris-flow like process on Mars. (3) The nature of interaction between glaciers, LDM and gullies does present reasonable evidence for extensive presence of ice in their formation. However, both CO2 and H2O ices are often found in vicinity. While CO2 ice sublimation keeps the gullies active in the present-day, debris-flow process still stands out as the dominant mechanism of sediment transport in Martian gullies in the past epochs. In the seminar, I will discuss these findings and present a geological evolutionary model of Mars during the Late Amazonian.

Title : How hot and wet is the Moon: Insight from experiments

Abstract

The thermal profile of the Moon (selenotherm) is required to determine its present-day interior structure and composition, and yet it is not constrained well. How can we constrain the selenotherm better? Also, measurements on lunar samples indicate that the Moon is not ‘bone dry’ but does have some hydrogen in its interior. The bulk lunar hydrogen is an important constraint to understand the dynamics of the Moon-forming impact as well as determine the origin of volatiles in the Earth-Moon system. The estimates of bulk lunar hydrogen span across a few orders of magnitude, but how can we constrain it better? In this talk, I will discuss how we can better estimate both the thermal state and the bulk lunar hydrogen to improve our understanding of lunar evolution.