Discovering the Unknown at the CERN Large Hadron Collider (LHC)

Amy GladwinUniversity of Arizona

2

Introduction

High energy physics or particle physics seeks to understand how the universe works at its most basic level What are the fundamental forces? What are the fundamental types of

particles (matter)? What is the nature of space and time?

Are there additional dimensions? How can we use these answers to

understand how the universe works?

3

Introduction

What is the universe made of? Dark energy – 65% Dark matter – 30% Baryons (protons and neutrons) – 4% Stars – 0.5% Neutrinos – 0.5%

Dark is just another word for “dunno” so, in short, we don’t know what most of the universe is made of!!!

Fundamental Forces

4

5

Fundamental Particles

6

Fundamental Particles

Or another pattern to unravel?

7

Particle AcceleratorsWe study nature using high energy

collisions between particlesParticle accelerators can be thought

of as giant microscopes that are used to study extremely small dimensions The higher the energy, the smaller the

wavelength the higher the resolving power

The higher the energy, the more massive the particles that can be created (E=mc2)

8

LHC (Large Hadron Collider)CERN is

located near Geneva, Switzerland

The energy of the LHC will be 7 TeV + 7 TeV But right now

it’s 3.5 TeV + 3.5 TeV

The ring circumference is 27 km

8

9

LHC (Large Hadron Collider)

At four points around the ring the two beams are brought together where collisions occur

The beams are actually composed of many “bunches” of protons

These bunch crossings (collisions) occur every 25 ns

At an energy of 7 TeV it takes 90μs for a proton to make one revolution

1010

LHC Bending Dipoles

1232 LHC superconducting dipoles

1111

What is the B Field?You might recall from your study of E&M

that a particle of momentum p in a uniform magnetic field B undergoes circular motion with radius R

The LHC circumference is ~27 km Packing fraction of ~64% gives R~2.8 km Thus B needed for p=7 TeV is ~8.3 T

Magnet current at this field is about 12000 A!! Magnet energy at this field is about 8000 J 1 kg of TNT has potential energy of about 5000 J This is amount of energy is substantial

GeVpTmBR 334.0

12

First Beam in the LHCSept 10, 2008 in the ATLAS control

room

13

September 19th IncidentAn electrical arc destroyed the busbars

14

September 19th IncidentHuge magnet displacements caused by

uncontrollable evaporation of liquid helium

15

Over a Year to Repair the LHC

asdf

LHC Experiments

Particle detectors are used to record the results of these high energy collisions

16

17

ATLAS Experiment

Visiting ATLAS

18

19

Particle Detectors

The type of particles produced are identified by how they interact in the various detectors

The momentum of charged particles is determined by their bend in a magnetic field

The energy of most particles (except muons and neutrinos) is determined by their deposited energy in calorimenters

20

Particle Detectors

21

ATLAS Experiment

Z → ee Candidate

22

W → e Candidate

23

What’s Happening at the LHC?

Since late March, the LHC has been running at 7 TeV This is only one half the design energy

The LHC is now increasing the beam intensity By adding more protons per bunch, more

bunches, and squeezing the beam

The LHC will run until the end of 2011 Followed by a year shutdown to fix

magnet splice problems Followed by running at 14 TeV

24

What’s Happening at ATLAS Now?

http://op-webtools.web.cern.ch/op-webtools/vistar/vistars.php?usr=LHC1

http://op-webtools.web.cern.ch/op-webtools/vistar/vistars.php?usr=LHC3

http://atlas-live.cern.ch/

25

What Do We Hope to Discover?

Some (or none!) of the following Higgs boson Supersymmetric particles (dark matter) Extra spatial dimensions Gravitons Evidence for quark substructure Your bright ideas here

In the best scenario we will discover phenomena that no one to date has predicted or thought of

26

27

LHC Surprises

27

28

ATLAS at ArizonaHere at the University of Arizona we

are analyzing data from ATLAS being collected now

We are also working on electronics and detectors to be used in the next generation of experiments at the SLHC (Super LHC) It may seem odd to be working on new

electronics for an experiment that has just started to run, but the lead time for developing new ideas and then building and testing them approaches a decade!

Readout Driver (ROD)The ROD is used to collect and process

data from the liquid argon detector front-end electronics

29

12 x 1 fibers

FEB (1524 modules) ROD (108 modules)

12 x 4 fibers

12 x 7 fibers

12 x 2 fibers

1Pre-Sampler

7Front

2Back

4Middle

LVL1Interface

text

text

text

ROBInterface

280 mm

320 mm

1

2

3

14

FPGA

~10 Gbps12

FPGA12

FPGA12

FPGA12

Readout Driver (ROD)The ROD must receive and process

1000 Gbits/s = 1Tbit/s !! Need state-of-the-art optics Need state-of-the-art FPGAs And be able to guess what might be

available a few years hence

In addition to managing the data, calculations must be performed on the data

And a system architecture developed to handle 200 such ROD cards

30

Summer OpportunitiesWhile it’s difficult to jump right in and

begin working on the ROD design, this summer you will learn basic skills of electronics design including some of Schematic design Layout design FPGA programming Electronics debugging using external and

internal logic analyzers Data acquisition software Particle physics at the LHC

31

Summer Opportunities

Data analysis If you are a very strong programmer,

you may also have an opportunity to analyze LHC data

But this demands strong C++ (or C) programming skills

32