Science Popularisation

2009
Discovery of the strange anti-matter

The STAR Experiment composed of 54 collaborating institutions from 13 countries: Brazil, PR China, Croatia, the Czech Republic, France, Germany, India, Korea, the Netherlands, Poland, Russia, the United Kingdom as well as the United States of America has reported in the journal Science [1], the evidence of the most massive antinucleus discovered to date. The new antinucleus is a negatively charged state of antimatter containing an anti-proton, an anti-neutron, and an anti‐Lambda particle. It is also the first anti-nucleus containing an anti‐strange quark.

All terrestrial nuclei, made of protons and neutrons (which in turn contain only up and down quarks), have a zero value for the quantum number 'strangeness'. The strangeness could be non‐zero in the core of collapsed stars, so the present measurements will help us distinguish between models that describe these exotic states of matter [2]. Since the discovery of hypernuclei in 1952, many major laboratories have dedicated experiments for hypernuclear studies, with on-going and future facilities at GSI and MAMI C in Germany, DAΦNE in Italy, J-PARC in Japan, JINR in Russia, and JLab in the USA. These experiments in near future could confirm the observations reported by STAR.

Paper published in 'Science' on this discovery

2010
Launch of a new experimental program to search for QCD Critical Point

Physical systems undergo phase transitions when external parameters such as the temperature (T) or a chemical potential (μ) are tuned. A phase diagram tells us how matter organizes itself under external conditions at a given degrees of freedom. The theory of strong interactions, Quantum chromodynamics (QCD), predicts that nuclear matter at high temperature and/or densities makes a transition from a state where quarks and gluons (color charge carrying basic constituents of matter) are confined in hadrons and chiral symmetry is broken to a state where quarks and gluons are de-confined and chiral symmetry is restored. QCD has several conserved quantities: the baryon number (B), electric charge (Q) and strangeness (S). Each of these is associated to a chemical potential. As a result, the QCD phase diagram in principle is four-dimensional. It has been observed that μQ and μS are relatively small compared to μB (baryonic chemical potential). The temperature T and μB are varied in a typical QCD phase diagram as shown in figure.

Paper published in 'Science' on the scale of QCD phase Diagram

2011
Discovery of heaviest anti-matter nuclei - The anti-alpha

About a billion collisions between gold nuclei using the Relativistic Heavy Ion Collider (RHIC) Facility in Brookhaven National Laboratory, USA, at center of mass energies of 200 and 62.4 GeV, were searched in the antimatter nucleus analysis reported by STAR [1]. The technique used is to first measure the ionization energy loss of charged particles produced in the collisions using a detector (called the Time Projection Chamber, TPC [11]) having gas as the sensitive medium and placed inside a magnetic field. The average energy loss (< dE/dx>) of these produced charged particles in the gas is proportional to mass of the charged particle and inversely proportional to the square of the velocity – the theoretical calculation of which was formulated by Bethe and Bloch [12]. The charge and the momentum of the particle are measured using a strong magnetic field of 0.5 Tesla. The < dE/dx> versus momentum per unit charge can be used for identifying the produced charged particles depending on their mass and momentum (as seen in Fig.1). The theoretical expectations as formulated by Bethe-Bloch are also shown in Fig. 1 as solid lines for different charged particles. The excellent agreement for lower mass particles provides a sound baseline for the claims of discovery for the heavier nuclei. One clearly observes four candidates of antimatter helium-4 nucleus (left panel) and several candidates of helium-4 nucleus (right panel) clearly separated from helium-3 nuclei at lower momenta.

Paper published in 'Nature' on this discovery

2012
Formation of perfect fluid in high energy heavy-ion collisions

Strongly coupled systems are characterized by the coupling parameter G that is the measure of the ratio of average potential energy to the average kinetic energy per particle. The strong coupling regime corresponds to G > 1. Recent work indicates that the coupling parameter for the QGP formed at RHIC and LHC is expected to be in the order of one [7]. The smallest value of h/s measured for any fluid at RHIC and LHC, has led to several interesting measurements for similar strongly coupled systems in condense matter physics – like Graphene [8] and dilute gases of ultracold fermions [9]. It is remarkable to note that both the coldest (ultracold fermionic gas) and the hottest matter produced (heavy-ion collisions at RHIC and LHC) on Earth exhibit very similar flow patterns, with η/s values close to the conjectured lower bound.

Paper on extracting the shear viscosity to entropy density ratio

2014
Properties of Fundamental Constituent of Visible Matter

The systems in nature that allows for studying the bulk properties of a strongly interacting matter are (a) the interior of atomic nucleus, (b) interior of nucleon, (c) interior of neutron star and (d) the de-confined state of quarks and gluons (fundamental constituent of any visible matter) called the quark gluon plasma (QGP). The latter state of matter has been created in the heavy-ion (Au, Pb, U) collisions at the Relativistic Heavy-Ion Collider (RHIC) facility, Brookhaven National Laboratory [1-4] and the Large Hadron Collider (LHC) Facility, CERN [5-11]. It has been found that the QGP behaves as, (i) a nearly inviscid liquid, and (ii) highly opaque to energetic colored (color charge) probes. Here we report the development towards establishing these properties both theoretically and experimentally. The 14 years of progress in this research towards arriving at the inviscid liquid property is summarized in the Figure 1 [12] and that towards the opaque property in Figure 2 [12]. Such has been the impact of this research that it has led to development in several new sub-fields of physics research, (a) relativistic viscous fluid dynamics, and (b) application of gauge-gravity duality to strongly coupled Quantum Field Theories.

Paper on Opacity Measurements in heavy-ion collisions

First Magazine by NISER Astronomy Club -
Kshitij, May 2020

A collection of events related to NISER Astronomy Club - made ny the stdudents in the Club. Astronomy is one of the oldest natural sciences and it also may be one of the first sciences we all come across as a kid. I am sure most of you while stargazing the night sky, start thinking unintentionally: what lies there? Richard Feynman had said: “Astronomy is older than physics. In fact, it got physics started by showing the beautiful simplicity of the motion of the stars and planets, the understanding of which was the beginning of physics. But the most remarkable discovery in all of astronomy is that the stars are made of atoms of the same kind as those on the earth.” When I was a child, during several evenings, my father and I used to gaze at the night sky together from the roof of our home. I distinctly remember the time, as there used to be a radio beside us gently playing. It used to start with Fauji Bhaiyon Ke Liye at 7 PM on Vividh Bharti, and end with the Hawa Mahal program at 8 PM. Every time I see the activities like those you have reported, I get reminded of those priceless personal moments. The realization going beyond that the stars are bright spots in the night sky, to the vastness of space and the immensity of the time that one experiences in the night sky are very humbling. It was so amazing to feel the harmony of infinite expanse.

Magazine

• Department of Science & Technology (DST), GOI sponsored 58th Innovation in Scientific Pursuit for Inspired Research (INSPIRE) Science Internship Camp ,from January 5-9, 2018
• Department of Science & Technology (DST), GOI sponsored 56th Innovation in Scientific Pursuit for Inspired Research (INSPIRE) Science Internship Camp ,from January 9-13, 2017
• Department of Science & Technology (DST), GOI sponsored 52nd Innovation in Scientific Pursuit for Inspired Research (INSPIRE) Science Internship Camp ,from September 13-17, 2016
• Department of Science & Technology (DST), GOI sponsored 50th Innovation in Scientific Pursuit for Inspired Research (INSPIRE) Science Internship Camp ,from March 09-13, 2016
• Department of Science & Technology (DST), GOI sponsored Innovation in Scientific Pursuit for Inspired Research (INSPIRE) Science Internship Camp ,from January 27-31, 2016
• Department of Science & Technology (DST), GOI sponsored 46th Innovation in Scientific Pursuit for Inspired Research (INSPIRE) Science Internship Camp ,from November 04-08, 2015
• Department of Science & Technology (DST), GOI sponsored 43rd Innovation in Scientific Pursuit for Inspired Research (INSPIRE) Science Internship Camp ,from August 18-22, 2015
• Department of Science & Technology (DST), GOI sponsored 36th Innovation in Scientific Pursuit for Inspired Research (INSPIRE) Science Internship Camp ,from August 19-23, 2014
• Department of Science & Technology (DST), GOI sponsored Innovation in Scientific Pursuit for Inspired Research (INSPIRE) Science Internship Camp ,from January 27-31, 2013
• INSPIRE Internship Program,sponsored by DST, Govt. of India ,from July 27-31, 2012
• July 2012: Recreating Early Universe in Laboratory [ Mentoring INSPIRE Internship Programme, Department of Science and Technology, Government of India for XI and XII students at KIIT University ]
• August 2012: Fundamental Building Blocks of Matter (Higgs Discovery) [ Mentoring INSPIRE Internship Programme, Department of Science and Technology, Government of India for XI and XII students at KIIT University ]
• January 2013: Recreating Early Universe in Laboratory [ Kendrapada Autonomous College, Odisha ]
• March 2014: Primodial Matter and its properties [ National Seminar on Recent Trends in Physics - Odisha Bigyan Academy, held at Utkal UNiversity ]