HIGGS BOSON A SEARCH FOR THE GOD PARTICLE

PREPARED BY Anup Das – 2866 Jyoti Yadav Md. Yusuf Jamal – 2902 Ritu BSc (Zoology) Honours First year, semester-1 Hansraj College

INTRODUCTION

A GENERAL IDEA To have + parity and zero spin, two fundamental attributes of a Higgs boson—making it also the first known scalar particle to be discovered in nature.. It would explain why some fundamental particles have mass when the symmetries controlling their interactions should require them to be massless, The Higgs boson is named after Peter Higgs, one of six physicists who, in 1964, proposed the mechanism that suggested the existence of such a particle.. Higgs boson has often been called the "God particle"

FUNDAMENTAL FORCES Electromagnetic Force: felt by all electrically charged particles, mediated by the photon, long range force Strong Nuclear Force: holds nuclei and nucleons together, felt by quarks and gluons, mediated by gluons, short range force Weak Nuclear Force: felt by all matter particles, mediated by W and Z bosons, short range force, responsible for beta decay Gravity: felt by all matter particles, mediated by the graviton, holds celestial objects in orbit, keeps us on the ground, long range force

STANDARD MODEL OF PHYSICS It is an elegant model that describes the fundamental particles theory of how the universe works at the subatomic level grew out of combining special relativity and quantum mechanics successfully predicted the existence of the top quark, the W Boson, and the Z Boson.

HIGGS BOSON The Higgs boson or Higgs particle is an elementary particle initially theorised in 1964,[6][7] and tentatively confirmed to exist on 14 March It would explain why some fundamental particles have mass when the symmetries controlling their interactions should require them to be massless, The Higgs boson is named after Peter Higgs, one of six physicists who, in 1964, proposed the mechanism that suggested the existence of such a particle.

GENERAL CHARACTERISTICS Composition-Elementary particle Statistics-Bosonic Status-A Higgs boson of mass ~ 125 GeV has been tentatively confirmed by CERN on 14 March 2013, although unclear as yet which model the particle best supports or whether multiple Higgs bosons exist. Symbol-Ho Theorised-R. Brout, F. Englert, P. Higgs, G. S. Guralnik, C. R. Hagen, and T. W. B. Kibble (1964) Mass ± 0.4 (stat) ± 0.5 (sys) GeV/c2,[4] ± 0.4 (stat) ± 0.4 (sys) GeV/c2 Mean lifetime 1.56×10−22 s Decays into (observed) W and Z bosons, two photons. Electric charge -0 Color charge-0 Spin-0 (tentatively confirmed at 125 GeV) Parity-+1 (tentatively confirmed at 125 GeV)

HOW THE HIGGS MECHANISM WORKS— EINSTEIN ANALOGY 1.Numerous physicists chat quietly in a fairly crowded room.

2.Einstein enters the room causing a disturbance in the field.

Followers cluster and surround Einstein as this group of people forms a “massive object”.

The Higgs Mechanism operates in a way similar to the case of Einstein in the crowded room. Particles that normally would have mass (e.g. Fermions, weak force carriers) move through the Higgs field interacting with Higgs particles. Through this interaction or disturbance particles may acquire mass. Heavier particles interact more with the Higgs field taking on more mass. Those particles that normally do not have mass, do not interact with the Higgs field, and therefore do not acquire it.

WHY DO WE NEED THE HIGGS? In order for the Standard Model to retain its symmetry, all particles would have to be massless. This is not possible since we know through experiments that the weak force carriers have mass The Higgs mechanism was originally introduced to allow the W and Z bosons to have mass. Physicists found to their delight that this was a way to give fermions mass as well. The current Standard Model provides no explanation of how some particles come to have mass. The presence of the Higgs and its corresponding Higgs field rectifies this problem.

SPONTANEOUS SYMMETRY BREAKING Developers of the Higgs mechanism used spontaneous symmetry breaking to introduce mass while retaining the SM’s overall symmetry. This is because the SM must be symmetric under gauge transformations

Without the Higgs mechanism, the SM remains symmetric only if mediators remain massless and produces nonsense results if weak force mediators have mass. The SM’s symmetry is broken only at a single point.

SPONTANEOUS SYMMETRY BREAKING ANALOGIES Set a ball on the tip of a Mexican Hat—the ball decides “spontaneously” where to fall. There is no influence on the ball’s path of choice In the diagram, the trough of the sombrero represents the Higgs field lowest energy states. The chosen field is spontaneously chosen breaking the symmetry.

CERN CERN is the European Particle Physics Laboratory and was founded in 1954 to bring together European nations divided by the Second World War. CERN was founded on two basic principles - first and foremost to be a world-class laboratory for research and discovery at the frontier of knowledge, but also to bring together European nations divided by the war. Since then it has continued to foster international co-operation and countries with strained diplomatic relationships can be found working together in many of its projects. CERN is the birthplace of the World Wide Web

THE LARGE HADRON COLLIDER (LHC) The LHC is CERN’s newest facility. It is set in a 27 km tunnel underground, crossing the border between France and Switzerland near Geneva. In fact it is in about the same size tunnel as the Circle Line! Within the LHC, two beams of protons (which belong to the family of particles known as hadrons) are accelerated to near the speed of light and then collided head on. In each collision two bunches of 100 billion particles meet. Where the particles crash into each other, new ones are formed, spraying out in all directions around the collision point. When the bunches meet, only about 20 proton-proton collisions happen – leading one physicist to describe it as being like ‘trying to throw two oranges so that the pips hit each other.’ To improve the odds, the particle beams cross about 40 million times per second!

ATLAS (THE DETECTOR) Atlas is designed to explore the fundamental nature of matter and the basic forces that shape our universe. The ATLAS detector searches for new discoveries in the head on collisions of protons of extraordinarily high energy. ATLAS is one of the largest collaborative efforts ever attempted in the physical sciences. There are 2900 physicists participating from more than 170 universities and laboratories in 37 countries. ATLAS will search for the Higgs particle, dark matter, supersymmetry and the unknown. ATLAS was assembled underground in a cavern the size of the nave of Westminster Abbey.

In mainstream media the Higgs boson has often been called the "God particle", from a 1993 book on the topic; the nickname is strongly disliked by many physicists, including Higgs, who regard it as inappropriate sensationalism. In 2013 Peter Higgs and François Englert were awarded the Nobel Prize in Physics for their discovery.

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