Manoranjan Dutta

Our research involves both high-energy physics and cosmology. 

HIGH ENERGY PHYSICS:

The Standard Model (SM) of particle physics is the best theoretical framework to explain the physics of elementary particles. However, there exists a plethora of physical phenomena that can not be addressed within the SM framework, hinting towards physics beyond the Standard Model (BSM). Dark matter (DM), neutrino mass and matter-antimatter asymmetry are the three great mysteries of physics that the SM fails to answer.

Dark Matter: Astrophysical observations like galaxy rotation curves, gravitational lensing and anisotropies in cosmic microwave background (CMB) provide ample shreds of evidence towards the existence of DM. In fact, satellite-borne experiments like PLANCK and WMAP have shown that DM constitutes almost 85% of the total matter content and 26.7% of the total energy budget of the Universe. Despite the irrefutable evidence, the true particle nature of DM remains yet unknown. Since the SM does not provide a viable DM candidate, several BSM scenarios have been proposed to explain DM, among which the weakly interacting massive particles (WIMP) have been the most popular ones. However, null detection of WIMPS at the terrestrial DM search laboratories inspires us to look beyond the minimalistic WIMP scenarios.

Neutrino Mass: In the SM, no right-handed neutrino (RHN) fields are introduced, and hence neutrinos remain massless due to the absence of a Yukawa interaction involving the SM Higgs, leptons and RHNs. However, the discovery of neutrino oscillation by the solar and atmospheric neutrino oscillation experiments proves that at least two of the three neutrino states are massive, however tiny that mass may be! Moreover, 'whether neutrinos are Dirac or Majorana particles' is hitherto unknown. Assuming the light neutrinos to be Majorana, several BSM frameworks have been invoked to explain neutrino mass popularly known as the seesaw mechanisms.

Matter-Antimatter Asymmetry:  In physical cosmology, the matter–antimatter asymmetry problem, also known as the baryon asymmetry problem, is the observed imbalance in baryonic matter (the type of matter experienced in everyday life) and antibaryonic matter in the observable universe. Neither the standard model of particle physics, nor the theory of general relativity provides a known explanation for why this should be so, and it is a natural assumption that the universe is neutral with all conserved charges. The Big Bang should have produced equal amounts of matter and antimatter. Since this does not seem to have been the case, it is very likely that some physical laws must have acted differently or did not exist for matter and antimatter. Several competing hypotheses exist to explain the imbalance of matter and antimatter that resulted in baryogenesis. However, there is as of yet no consensus theory to explain the phenomenon.

COSMOLOGY:

In the Standard Model of Cosmology or the ΛCDM model, DM is postulated to be Cold and Collisionless and is supposed to have facilitated the structure formation in the early Universe by providing the necessary gravitational potential for the primordial density fluctuations to grow. A typical WIMP fits well to be cold and collisionless. Predictions of the ΛCDM are in excellent agreement with the observed large-scale cosmological structures like CMB. However, in recent times, cosmological simulation with better resolution reveals several discrepancies between astrophysical observations and the predictions ofΛCDM, leading to small-scale anomalies such as the ‘cusp-core problem’, ‘missing satellite problem’ and ‘too-big-to-fail problem’. 

Research Group: The following students are currently pursuing MSc Project with me.

1. Mr. Trinayan Saikia,
2. Ms. Nischita Kataky