CERN-Higgs Boson - Hans Raj College

Report
PREPARED BY
Anup Das – 2866
Jyoti Yadav- 2969
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 2013.
. 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
125.3 ± 0.4 (stat) ± 0.5 (sys) GeV/c2,[4] 126.0 ± 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.
Thank You

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