<div align="justify">Today, the building blocks of matter are considered to be quarks and leptons. There are six quarks, with the first four having names like up, down, strange, charm. Leptons are represented by the familiar electron and the unfamiliar muon and neutrino. Like all particles, quarks and leptons also have antiparticles. Normal matter (protons and neutrons) and some of the mesons are made up of Up and Down quarks in different proportions. <br /><br />The strange particles are made up of a Strange quark and other quarks. Charm quarks come together to form several other particles like J/psi, which was detected in the 1970s. Both quarks and leptons are grouped under Fermions. However, what binds these Fermions are group of particles called Bosons, which are the force carriers. Photon, the light particle, is the force carrier when electrons interact. The exchange particles for quarks are called gluons.<br /><br />The revolutionary aspect of quarks, when it was proposed in 1964, was their fractional charges. While proton and electron have charge of +1 and -1, quarks have 1/3 and 2/3 charge. It was also realised that quarks cannot be registered the way protons and electrons can be recorded through detectors. Therefore, it was hypothesised that quarks are confined within the nucleon; they are relatively free but when one tries to take the quark out of the proton, the quarks stick together and come out as either baryons or mesons. <br /><br />Detecting Quark-Gluon Plasma<br />However it was expected that at sufficiently high temperature and density, the nuclear matter can be melted down to a new state of matter where quarks and gluons are relatively free. It was hypothesised that this state of matter, called the Quark-Gluon Plasma (QGP), did exist in the initial moments after the Big Bang. The single force existing at the very beginning split into the four forces after a pico second. Immediately after this is the beginning of the quark epoch which lasted till a microsecond. During this time, all fundamental particles existed together in this primordial soup, the QGP. The temperature of the universe at that time was eight trillion degree Celsius, which is a hundred thousand times hotter than the centre of the sun. <br /><br />It was also realised after some experimentation that higher energy density in a space much larger than that of proton size is necessary to produce QGP. Therefore, it was suggested that it could be achieved in collisions of heavy nuclei. Gold and lead were considered the best.<br /><br />From the late 1900s, experiments at Brookhaven Laboratory in USA and the European Organisation for Nuclear Research (CERN) in Europe have been trying to detect the QGP. Earlier experiments at CERN reached about 1,500 billion degrees Kelvin. This increased to 4000 billion degrees Kelvin in 2010 in the Relativistic Heavy Ion Collider (RHIC) by gold-gold collisions. The ALICE (A Large Ion Collider Experiment) experiment, which is apart of the Large Hadron Collider (LHC), had reached a temperature of 5,500 billion degrees Kelvin in 2012 by using lead ions instead of gold. This is the highest temperature ever achieved in the laboratory.<br /><br />The scenario for QGP formation is that the enormous amount of heat liberates the quarks and gluons which coalesce immediately into a plasma state. After existing like a fireball for very short time it cools down and transforms itself into single particles. The high energy nucleus collisions produce enormous number of particles and the proof for the QGP could be found in the composition and behaviour of these particles.<br /><br />Distinctive signatures<br />The search started in CERN with the Super Proton Synchrotron (SPS) with lead ions at an energy of 33 TeV in 1994. There were seven experiments looking for the effect, and detection of QGP was announced six years late. Evidence of a new state of matter where quarks and gluons are not confined was revealed in 2000. RHIC and ALICE have studied the phenomenon more extensively. <br /><br />There are several important signatures for the QGP formation such as the enhanced strangeness production from QGP, which was predicted in the 1980s, and the J/PSi suppression in which the screening effects are expected to dominate, which results in charm quarks producing particles other than J/Psi. Both these signatures have been seen in experiments in USA and Europe. There are also other signatures like that of thermal photons which have not yet been realised.<br /><br />However, the exciting result in the last few weeks has been the possible formation of QGP in unexpected conditions. The ALICE collaboration published an article the April 2017 edition of Nature Physics that it is possible to detect QGP in collisions of light particles like protons. While there has to be more signatures to believe that QGP has been formed, this new aspect of proton collisions is exciting and needs more study.</div>
<div align="justify">Today, the building blocks of matter are considered to be quarks and leptons. There are six quarks, with the first four having names like up, down, strange, charm. Leptons are represented by the familiar electron and the unfamiliar muon and neutrino. Like all particles, quarks and leptons also have antiparticles. Normal matter (protons and neutrons) and some of the mesons are made up of Up and Down quarks in different proportions. <br /><br />The strange particles are made up of a Strange quark and other quarks. Charm quarks come together to form several other particles like J/psi, which was detected in the 1970s. Both quarks and leptons are grouped under Fermions. However, what binds these Fermions are group of particles called Bosons, which are the force carriers. Photon, the light particle, is the force carrier when electrons interact. The exchange particles for quarks are called gluons.<br /><br />The revolutionary aspect of quarks, when it was proposed in 1964, was their fractional charges. While proton and electron have charge of +1 and -1, quarks have 1/3 and 2/3 charge. It was also realised that quarks cannot be registered the way protons and electrons can be recorded through detectors. Therefore, it was hypothesised that quarks are confined within the nucleon; they are relatively free but when one tries to take the quark out of the proton, the quarks stick together and come out as either baryons or mesons. <br /><br />Detecting Quark-Gluon Plasma<br />However it was expected that at sufficiently high temperature and density, the nuclear matter can be melted down to a new state of matter where quarks and gluons are relatively free. It was hypothesised that this state of matter, called the Quark-Gluon Plasma (QGP), did exist in the initial moments after the Big Bang. The single force existing at the very beginning split into the four forces after a pico second. Immediately after this is the beginning of the quark epoch which lasted till a microsecond. During this time, all fundamental particles existed together in this primordial soup, the QGP. The temperature of the universe at that time was eight trillion degree Celsius, which is a hundred thousand times hotter than the centre of the sun. <br /><br />It was also realised after some experimentation that higher energy density in a space much larger than that of proton size is necessary to produce QGP. Therefore, it was suggested that it could be achieved in collisions of heavy nuclei. Gold and lead were considered the best.<br /><br />From the late 1900s, experiments at Brookhaven Laboratory in USA and the European Organisation for Nuclear Research (CERN) in Europe have been trying to detect the QGP. Earlier experiments at CERN reached about 1,500 billion degrees Kelvin. This increased to 4000 billion degrees Kelvin in 2010 in the Relativistic Heavy Ion Collider (RHIC) by gold-gold collisions. The ALICE (A Large Ion Collider Experiment) experiment, which is apart of the Large Hadron Collider (LHC), had reached a temperature of 5,500 billion degrees Kelvin in 2012 by using lead ions instead of gold. This is the highest temperature ever achieved in the laboratory.<br /><br />The scenario for QGP formation is that the enormous amount of heat liberates the quarks and gluons which coalesce immediately into a plasma state. After existing like a fireball for very short time it cools down and transforms itself into single particles. The high energy nucleus collisions produce enormous number of particles and the proof for the QGP could be found in the composition and behaviour of these particles.<br /><br />Distinctive signatures<br />The search started in CERN with the Super Proton Synchrotron (SPS) with lead ions at an energy of 33 TeV in 1994. There were seven experiments looking for the effect, and detection of QGP was announced six years late. Evidence of a new state of matter where quarks and gluons are not confined was revealed in 2000. RHIC and ALICE have studied the phenomenon more extensively. <br /><br />There are several important signatures for the QGP formation such as the enhanced strangeness production from QGP, which was predicted in the 1980s, and the J/PSi suppression in which the screening effects are expected to dominate, which results in charm quarks producing particles other than J/Psi. Both these signatures have been seen in experiments in USA and Europe. There are also other signatures like that of thermal photons which have not yet been realised.<br /><br />However, the exciting result in the last few weeks has been the possible formation of QGP in unexpected conditions. The ALICE collaboration published an article the April 2017 edition of Nature Physics that it is possible to detect QGP in collisions of light particles like protons. While there has to be more signatures to believe that QGP has been formed, this new aspect of proton collisions is exciting and needs more study.</div>
