CERN, 21 February 2001 Egil Lillestøl, CERN & Univ. of Bergen Recorded at .

CERN, 21 CERN, 21 February 2001February 2001CERN, 21 CERN, 21 February 2001February 2001Egil Lillestøl, CERN & Univ. of BergenEgil Lillestøl, CERN & Univ. of BergenEgil Lillestøl, CERN & Univ. of BergenEgil Lillestøl, CERN & Univ. of Bergen

Recorded at http://www.cern.ch/wlap


Where are we with the Higgs ?


Why all the excitement about the Higgs ?

Like all the other fields the Higgs field is omnipresent.

The role of the Higgs field is to give mass to all particles.

Understanding the Higgs field could mean understandingthe masses of the fundamental particles (fields)

The Higgs field could naturally contribute to an explanationof the accelerating expansion of the Universe.

Does the Higgs particle exist and will its existencebe confirmed at CERN or at Fermilab ?


Other questions for the LHC

- What happened to the Antimatter in the Universe ?- Can all the Forces and Particles be unified ? (Super Symmetry)- Did the Universe go through a Phase of Quark-Gluon Plasma ?

Super Strings- Can General Relativity and Quantum Mechanics be unified ?- Are the Fundamental Particles two-dimensional Strings ?- Does the Universe have more than three Spatial Dimensions ?

- Accelerating Expansion of the Universe and Dark Matter


Matter

Anti MatterWhat happened to the Anti Matter ?


Was there a perfect symmetry between matterand antimatter in the early Universe ?

The answer must be no !


Before time = 1 microsecond (after Big Bang):

Energy protons + antiprotons

After time = 1 microsecond:

Energy protons + antiprotons

Small excess (1/1000 000 000) of protons ?( CP violation)

time = 1 µs : The big antimatter massacre:

1 000 000 001 protons+ 1 000 000 000 antiprotons= 1 proton + energy


CP violation observed

Needs tree quark-lepton families to be explained

Studied at CERN, SLAC, KEK, Fermilab

Does not yet explain the Matter Antimatter asymmetry

CP violation to be studied extensively at the LHC


The Supersymmetry Puzzlethere has to be some sort of connection

between the matter and the force particles !

Putting the matter particles and the force carrying particlestogether in a common scheme is a strange puzzle.The final puzzle is full of holes that has to be filled bynew particles. These are the Supersymmetric Particles, and the Higgs fields are needed !


the Supersymmetric Particles? may be produced in pairs at the LHC ?

- The lightest SS Particle “must” be stable,- it must have been produced together with all

the other matter particles in the Big Bang- it must be much heavier than protons, and

- will therefore dominate the mass content of the universe

Supersymmetric particles may explain the Dark Matter problem in Astrophysics


Unification of forces:the electromagnetic, weak and strong forces

These forces are very different at low energies,but may they come together at very high energies ?

and what about gravity ?

superstrings and extra dimensions

How heavy are the Higgses, andthe supersymmetric particles

(can they be produced at the LHC ? Energy? Intensity?)

The lightest Higgs particle was within reach of LEP ??

For answers to the others we have to look at:


How the forces vary with distance

Classical electrostatics (Coulomb’s law):

F = k (q1 q2)/r2

Classical gravitation (Newton):

F = (M1 M2)/r2

In a quantum field theory the “constants”k and will vary with energy (Vacuum Polarization)

Is it possible that all the forces of Nature havethe same strength at a certain (very high) energy?


The “strength” of the strong force(running of the Coupling “Constant” S)


Unification of the Coupling Constantsin the SM and the minimal MSSM


Unification of Gravity with the other forces

From a simple extrapolation this should happen at anenergy scale of 1019 GeV or a length scale of 10-35 m

But only superstring theory is capable of unifying all the forces.Superstring theory contains supersymmetry.

Superstrings are objects with 1 spatial dimension moving in a worldof 9, but where all but three dimensions are curled up on an unobservable scale !

The # of dim. for the EM field is tested to be 3 down to 10-18 m,but gravity is tested only down to mm scale ! !

Is unification of all the forces possible at the TeV scale ?


How many macroscopic dimensions can we “see”?

gravitation and light (electromagnetism) tell us:three macroscopic dimensions

In N dimensions:field lines spread out,i.e. field weakens as

1/rN-1


“One-dimensional” garden hose


One curled-up dimension


Two curled-up dimensions


Two curled-up dimensions (another topology)


Six curled-up dimensions (Calabi - Yau topology)


Particles as Super Strings

Strings and extra dimensions:

.. . .

Two-dimensional(“normal”) Space

Extra Dimension Graviton


10-3

to10-14 m

Gravity may curl up differently than the other forces.

Gravity may be weak because it has continued to spreadout in more than 3 dimensions up to a larger scale thanthe other fields.


Gravitons may have the freedom to move in moredimensions than other particles

Gravitons may be produced in large numbers at the unification scaleand disappear into the hidden dimensions (missing energy)

New particles and micro black holes corresponding to 10-19 m sizeswould be produced.


1 mm

1 mm

billions of light years

Parallel universesgravity curled up at millimeter scale

Gravity from galaxy on neighboring sheet may be weakly felt


1 mm

1 mm

One universe (folded)Gravity from galaxy on neighboring sheet (mm distance )can be weakly felt. Light has to go billions of light years.

billions of light years


Need large, hermetic and very performant detectors


See: http://na49info.cern.ch/alice/html/intro/


CMS


Supersymmetric particles (or something unforeseen)will turn up around TeV energies

Free Energy ( EF ):

EF prop. to EProton

EF equal to 2xEProton

Fixed target

Collider

BUT:

EQuark is on average only

1/6 of EProton


With decreasing probability the quarks can carryan increasing fraction of the proton energySo, in order to produce new particles of up to a few TeVwe need a collider with total energy of at least 10-15 TeV

-quark quark collisions are in themselves rare-Some of the hypothetical particles will appear with very low probabilities High Luminocity needed.

Also total Energy may be traded with Luminocity

The will do the job !

CERN, 21 February 2001 Egil Lillestøl, CERN & Univ. of Bergen Recorded at .

Documents

Transcript of CERN, 21 February 2001 Egil Lillestøl, CERN & Univ. of Bergen Recorded at .