Particle Physics and LHC Physics

Particle Physics and LHC Physics

David Krofcheck

Canterbury Teachers Workshop July 18th

D. Krofcheck Canterbury Teachers Workshop 1

Large Hadron Collider

CMSexperiment

Thanks to Lucas Taylor, 2012

The place to be for high energy physicists

CERN (CH)

CERN (FR)

Genevaairport

Lac LémanJura

Large Hadron Collider

CMSexperiment

Thanks to Lucas Taylor, 2012

Large Hadron Collider

3

• 27 km (17 miles) circumference

• 1600 superconducting magnets at 1.9° K (-271.3° C or – 459.7° F)

• 120 tonnes of liquid helium

• Accelerates beams of protons to 99.9999991% the speed of light

Large Hadron Collider

The CMS detector at the Large Hadron Collider

Muon Barrel

Tracker (Pixels and Strips)

EM Calorimeter Hadron Calorimeter

Muon Endcaps

Forward Calorimeter

Beam Scintillator Counters

CASTOR

ZDC

D. Krofcheck Pitt/CMU July 2011 4

New Zealand

D. Krofcheck Pitt/CMU July 2011 5

The really important CMS detectors

Aristotle : all matter is made up of various combinations of Earth, air, fire and water

What is matter?

This belief about the nature of matter lasted for 2000 years

solids

liquids

gases

change

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Democritus

Lucretius

John Dalton

Development of the Atomic Theory

Aristotle

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Ideas about Atoms

1800’s

John Dalton – meteorologist and teacher

- successfully explained chemical reactions by proposing all matter is made up of atoms.

- BUT they had no direct evidence!D. Krofcheck Canterbury Teachers Workshop 8

DmitriMendeleev

Russian

1834-1907

Periodic TableSimilar chemical properties

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Periodic Table

?

Atoms

Rutherford (1909)

Bohr (1913)D. Krofcheck Canterbury Teachers Workshop 10

...

proton neutron electron

• Are these the elementary particles, ?

• Are they composed of even more elementary particles??

• Particle and Nuclear Physics are the studies to answer this questionD. Krofcheck Canterbury Teachers Workshop 11

Matter Particles

1932 p, n, e ν

1937 μ

1940s mesons π, K

1950s particles Λ, Δ, Σ, ...

…hundreds of new particles were discovered!

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In 1964 the idea of quarks was proposed… quark

s

u

d

u

proton

d

u

d

neutron

Gell-Mann

Zweig

These were elementary particle of, fractional electric charge, different flavours

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What is the composition of the proton

d u

uq(u) = +2/3q(d) = -1/3

q(p) = +1

...and of the neutrond u

d q(n) = -1/3 - 1/3 + 2/3= 0

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What glues the quarks together?

u u

d protonGluons, of course

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Elementary particles of matter

1st family: u, d, e- , e

2nd family: c, s, - ,

3rd family: t, b, - ,

lept

ons

1897

1995

Higgs4 July, 2012D. Krofcheck Canterbury Teachers Workshop 16

Antimatter

Every particle has its antiparticle, of the same mass but opposite quantum numbers

eg. electron, e- : q(e-) =-1 , spin = -1/2 , m(e-) = 9.110-28 gr. positron, e+ : q(e+) =+1 , spin = +1/2 , m(e+) = 9.110-28 gr.

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Electromagnetic ForceGravitational Force

Strong Colour Force Weak Force

.... .

.átomo

nuclei n p + e- + e

d u + e- + e

1

10-2

10-5

10-40

All these interactions are manifestations of only

4 basic interactions

Interaction Type

Electromagnetic γ (photon)

Strong g (gluon)

Weak bosons W, Z

Gravitational G (graviton)

Still not detected experimentally

Mediating Particle

Example: Electromagnetic interaction

+ -+-p pe + e+

http://www.cerimes.education.fr/

The Fundamental Interactionsare produced by the exchange of a particle mediator

The particles of matter interact across a distance by exchanging a “messenger” particle

http://www.cerimes.education.fr/

The interaction range decreases as the mass of the messenger particle increases.

Standard Model of Particle Physics In a quantum description of matter and the laws of interaction

between them still do not know how to incorporate gravitation, but the rest of interactions are well described by a mathematical theory, the

Standard Model, able to make predictions that have been confirmed in experiments.

lept

ons

•M

esse

nger

s •

inte

ract

ions

Standard Model

(~1980)

Components of matter Interactions

Symmetry

This model requires that the particle messengers are massless,But the W and Z are very heavy!! problem of the origin of mass

Higgs Boson The British physicist Dr. Peter Higgs proposed (1964) the so-called Higgs mechanism:All the particles would be generated in the Big Bang without mass, but by interacting with the field created by the Higgs particle, the particles would acquire mass, the greater, the greater the interaction. This field would fill the whole universe.

Interaction with the Higgs field

Friction with a viscous liquid≡

Higgs BosonThe British physicist Dr. Peter Higgs proposed (1964) the so-called Higgs mechanism:All the particles would be generated in the Big Bang without mass, but by interacting with the field created by the Higgs particle, the particles would acquire mass, the greater, the greater the interaction. This field would fill the whole universe.

Unico “Higgs” observado hasta ahora en un experimento…el propio Dr. Higgs!!

Friction with a viscous liquid≡Interaction with the

Higgs field

Higgs Boson

≡

.

A recent view of a Higgs at the CMS experiment

This particle predicted has not yet been unambiguously detected in experiments, hopefully we are hot on the trail!

!!?? H Z0 Z0 μ+ μ- μ+ μ-

Gauge Bosons – Z0 First detection in HI collisions!

First step is to find Z0 bosons in PbPb collisions

Z0 → μ+μ - observed for the first time in HI collisions!

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Z0 → e+e- observed for the first time in HI collisions!

Z0 → e+e- event candidate

lead + lead collisions may liberate quarks

Jet production in pp collisions

jet-jet correlation in QCD “vacuum”

D. Krofcheck Dijet Probes of Hot Nuclear Matter at the LHC 31

Jet

Jet

Jet production in PbPb collisionsjet-jet correlation in QCD “medium”

γ – jet correlation to probe the medium?

D. Krofcheck Dijet Probes of Hot Nuclear Matter at the LHC 32

E-ΔΕ1

E-ΔΕ2

Dijet imbalance in PbPb collisionsΔφ

Phys. Rev. C 84, 024906 (2011)

D. Krofcheck Dijet Probes of Hot Nuclear Matter at the LHC 33

Jet production in PbPb collisions

D. Krofcheck Dijet Probes of Hot Nuclear Matter at the LHC 34

gamma-jet correlation in QCD “medium”

Gamma

Nuclear remnant Nuclear remnant

• Momentum ratio shifts/decreases with centrality– jets shifting below the 30 GeV pT threshold not included

Submitted to PLB, arXiv:1205.0206

Observed momentum imbalance in γ – jet correlation

D. Krofcheck Dijet Probes of Hot Nuclear Matter at the LHC 35

Energy Units!

1 eV = 1 electron VoltEnergy to ionise hydrogen = 13.6 eV

1 keV(kilo) = 1,000 eV = 103 eVMedical X-ray ~ 200 keV

1 MeV(Mega) = 1,000,000 eV = 106 eVAlpha particle decay of uranium 4.2 MeV

1 GeV(Giga) = 1,000,000,000 eV = 109 eVLEP collider beam (1989-2000) = 45 GeV

1 TeV(Tera) = 1,000,000,000,000 eV = 1012 eVHighest energy accelerator in world = 1 TeV (Tevatron)

Electron Volt – Energy gained by an electron when accelerated in an electric field through a potential difference of 1 volt.

Highest energiesfound in cosmic rays (>1020 eV)

Interactions between matter particles

Why are there so many different substances in the world?

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