the higgs boson - institut franÇais de suÈde · 10 november 2015 johann collot : [email protected]...
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Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot10 November 2015 1
The Higgs boson
Johann Collot Laboratoire de Physique Subatomique
et de Cosmologie de Grenoble
Université Grenoble Alpes , CNRS/IN2P3
Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot10 November 2015 2
Higgs boson : a very simple particle
● No electrical charge
● No spin (self-rotation)
● Almost simpler than a photon
● But an unpredicted mass that turned out to be equal to that of a cesium atom
● Then was very difficult to produce and observe becausehighly unstable
● And a rôle which is a bit obscure
Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot10 November 2015 3
Zoo of elementary particles
electron
neutrino
u quark
d quark
Q = 0
Q= - |e|
leptons
Q = -1/3 |e|
Q = 2/3 |e|quarks
muon
neutrino
c (charm) quark
s (strange)quark
tau
tauneutrino
t (top) quark
b (bottom) quark
electron muon
Strong color interactionElectromagnetic Interaction
WeakInteraction
Gluons
Photon
weak bosons
Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot10 November 2015 4
Proton
UP UP
DOWN
Simulation
Art CatherineChariot
The proton structure is more complex than that of a star
Proton is sort of microscopic bubbling of quarks and gluons 100000 times smaller than the size of an atom.
Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot10 November 2015 5
Mass
P=mg gravitational mass Galileo
F=ma inertial mass Newton
E=γmc2 mass-energy equivalence Einstein
All these masses are identical.
Initially all elementary particles are massless, but in physics, mass is found almost everywhere.
Generating a proper energy to a particle automatically creates an inert and gravitational mass.
Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot10 November 2015 6
masses of elementary particles in cartoon
Everywhere in space, there's anew field : the Higgs field
A free and massless particle gets immersed
The Higgs field gets polarized around the particle, generatinga mass term.
Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot10 November 2015 7
The Higgs boson
The Higgs field gets excited .
The quantum perturbationpropagates and almostinstantaneously decays into elementary particles.
Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot10 November 2015 8
Large Hadron Collider7 TeV Proton + 7 TeV Proton 14 TeV collisions
Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot10 November 2015 9
ATLAS
Collaboration of 3000 physicists (1000 Ph. D. students) working in 174 universities and laboratories of 38 countries
http://atlas.ch
Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot10 November 2015 11
Production of a Higgs boson
t quark
t antiquark
Higgs boson
proton
protongluon
gluon
Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot10 November 2015 12
Higgs boson decay
Higgs boson
W boson
W boson
photon
photon
Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot10 November 2015 13
Higgs boson decaying into two photons
Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot10 November 2015 14
ATLAS CMS
The same particle is observed with more than 5 sigma significance in two different detectors operated by two independent collaborations..
The discovery
Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot10 November 2015 15
Is it really the Higgs boson ?
It really seems like it, sinceHiggs boson is the only particlethat couples to all other elementaryparticles proportionally to theirmass.
Confirmed by experiments
coupling toother elementaryparticles
Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot10 November 2015 16
French-Swedish collaboration● Started at the beginning of the 90's : LPSC Grenoble and KTH
Stockholm together with 5 institutes of Morocco : design and construction of ATLAS detector
● 2 young French Ph.Ds came and stayed in Sweden : Arnaud Ferrari , U. of Uppsala and Christophe Clément , U. of Stockholm
● Collaboration is still going on :
– search for additional Higgs bosons : neutral or charged LAL Orsay, LPSC Grenoble, KTH Stockholm and U. of Uppsala
– upgrade of ATLAS detector for LHC phase 2
– 2 cosupervised and cofinanced PhDs :
● Alexander Madsen (defended May 2015) ● Joakim Gradin (defence in 2017)
Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot10 November 2015 17
People involved in French-Swedish collaboration
● LPSC Grenoble : – Johann Collot, Joakim Gradin (also U. of Uppsala)
● LAL Orsay :– Zhiquing Zhang
● U. of Uppsala– Elin Bergeås-Kuutmann, Richard Brenner, Tord Ekelöf, Arnaud
Ferrari, Joakim Gradin (also LPSC)
● KTH Stockholm :– Bengt Lund-Jensen, Jonas Strandberg
Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot11 April 2014 19
Universe history and its contentThe evolution and the structure of universe depend upon its content !
t = 380 000 ans
Will LHC be capable of producing a bit of Dark matter ?
énergie sombre
From observations of the evolution and the structure of our Universe, we can infer that as of today ourordinary matter (us, planets, stars, galaxies ...) accounts for only 5 % of universe. The essential eludes us ....
Johann Collot : [email protected] ; http://lpsc.in2p3.fr/collot11 April 2014 20
Supersymmetric particles
Each existing elementary particle would have a supersymmetric partner of heavier mass, then never produced till now by accelerators
If one of these particles were neutral, stable and weakly interacting with matter,it could then constitute the missing Dark Matter (27% of Universe density)