Searching for the Higgs

Tara Shears

University of Liverpool

What is particle physics?

Study of the infinitessimally small, fundamental parts of matter and their interactions

How small is small?

???

Particle physics

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WEAKELECTROMAGNETICSTRONG

GRAVITY

What is mass?

… energy? … Resistance to gravity?

…..property mediated by “Higgs Particle”

AnalogyInteraction with Higgs field ( mass) ~ movement of body through medium

Light particles do not interact much (move fast)

More interaction – slower movement – more mass conferred

Heaviest particles …. most interaction

What is mass?

…property mediated by “Higgs Particle”

nb …… we haven’t seen it yet …..

???

Where is the Higgs?

LEP (1990-2000)

Electrons and positrons collide 40 million x a second

Four experiments

?

?

Le Boson de Higgs en ligne de mire

Hints of new particle may be massive find for physicists

Svelata la particella di Dio

Das Teilchen GottesCzastka Higgsa

zlapana?

Atom smasher shut as ‘holy grail’ glimpsed

Scientists find “God’s particle”

11th hour stuff …

Where is the Higgs?

September …… December 2000

Where is the Higgs?

CDF:706 people

12 countries

D0:650 people

18 countries

Fermilab: 2001…2005….

World’s most powerful accelerator

…. still no sign …….

Looking for Higgs - LHCWorld’s most powerful particle accelerator

2 beams of protons collide 40 million x a second

4 large experiments

Due to start in 2007

27 km

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?

?

aside: LHC vs. circle line

LHC Circle line

Length 27km 22.5km

Depth 100m 15m

Diameter 3.8m 3.4m

Looking for Higgs - experiment

eg. …the ATLAS experiment:

5 storey building 7,000 tonnes 42m long 22m wide 22m high2,000 Physicists 150 Institutes 34 Countries

Starting from this event…

We look for this “signature”Selectivity: 1 in 1013

Like looking for 1 person in a thousand world populations

Or for a needle in 20 million haystacks!

Finding Higgs• 800,000,000 proton-

proton interactions per second

• ~100,000,000 electronic channels

• 0.0002 Higgs per second

HOW do we find the Higgs?

Distributed Computing Solution – Grid

Concorde(15 Km)

Balloon(30 Km)

CD stack with1 year LHC data!(~ 20 Km)

Mt. Blanc(4.8 Km)

…. a needle in 20 million haystacks!

LHC produces enough data to fill 14 million cds / year (1,000,000 times world annual book production!!)

Estimated we need 100,000 computers to analyse it all …..

grid!

summarySearch for origin of mass and Higgs major unanswered question

Hope for discovery at LHC

Immense technological and computing challenge: grid!