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Particle Physics (C4)

Where do the particles get their mass from?

What is dark matter made of?

Where has all the anti-matter gone?

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2

CMS

LHCb ATLAS

ALICE

A thorough grounding in the Particle Physics

Standard Model and a brief introduction to why

it cannot be complete.

What to expect:

High-energy collider experiments.

Non-accelerator physics.

Physics beyond the Standard Model.

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The Particle Physics Syllabus

Introduction to relativistic quantum mechanics. Matrix elements. Discrete and

continuous symmetries. Gauge symmetries and the Standard Model.

Elementary introduction to radio-frequency acceleration and beam optics.

Colliders and fixed targets. Event rates and luminosity.

Triggering and event selection. Physics of particle detectors, wire chambers,

silicon detectors, calorimeters, muon chambers, Cerenkov radiation detectors.

Particle identification. Applications to real experiments.

Quark structure of hadrons. Deep inelastic scattering, the quark-parton model

and quantum chromodynamics (QCD). Heavy quark states.

Electroweak interactions, charged and neutral currents. Electroweak symmetry

breaking. W and Z bosons. Fundamental particles of the Standard Model.

Discovery of the top quark and searches for the Higgs boson.

Oscillations in the K0 and B0 systems, CP violation. Neutrino oscillations. Ideas

beyond the Standard Model and future projects.

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Snapshots from the Standard Model

Forces

Matter particles

Masses &

potentials

(Untested)

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The Particles and Forces

Why is it like this?

3 generations of

matter (fermions)

Carriers of forces

(bosons)

(eight coloured gluons)

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LHC experiments are taking data

Higgs Results

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https://twiki.cern.ch/twiki/pub/AtlasPublic/HiggsPublicResults//Hgg-

FloatingScale-Short2.gif

More to do:

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Question: is there any evidence for a Higgs boson

– Answer: there is 5s evidence for a new boson.

As usual in science one answer generates many new questions

…

– Does this boson couple to mass in the way predicted by the SM? Need

much more LHC data and ILC.

– Does it have the predicted narrow width? Need ILC data.

– Theory needs f4 term self coupling multiple H. Need HL-LHC.

– In SM, Higgs prevents unitarity violation in WW scattering need to

measure WW at HL-LHC.

– Are there more Higgs bosons (simplest SUSY model needs 5)? Need

more LHC and HL-LHC data.

– Why is the Higgs light compared to Planck scale? Need experiments at

the TeV scale more LHC data

This is the start of a new chapter in physics not the end …

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LHCb: CP violation measurement

Separate samples into B0 and B0 using particle ID

Raw asymmetries clearly visible in data: direct CP Violation > 3σ

Central values consistent with expectations and previous measurements

Bd0

Bs0

CP violation

NB: corrections from production and detector asymmetry not yet corrected for

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Beyond the Standard Model

Standard Model is very successful, but ….

Too many free parameters (19).

Why 3 generations?

Origin of mass.

Hierarchy problem.

Dark matter.

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Dark Matter Searches

A mile underground…

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Neutrinos (T2K)

http://t2k-experiment.org/

• the discovery of νμ → νe ( i.e. the confirmation that θ13 > 0 )

• precision measurements of oscillation parameters in νμ disappearance

• a search for sterile components in νμ disappearance by observation of

neutral-current events

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The Essentials Based on material covered in A3, B2 and B4

C4 website (or via Lecturer Material):

www.physics.ox.ac.uk/users/kraus/Teaching/C4-home.htm

Vacation problem set is on the web site

(will be discussed as part of the first class in MT)

For new students

Coordinator (from MT16): Tony.Weidberg@physics.ox.ac.uk