fermilab’s tevatron & large hadron collider (lhc) teruki...

1Hadron Collisions at the Tevatron and the LHC

FermilabFermilab’’s Tevatron s Tevatron &&Large Large Hadron Collider Hadron Collider (LHC)(LHC)

Teruki KamonPHYS 627

Taken from slides by Ron Moore, Paul Derwent, Mike Syphers (FNAL) (Apr 2005)Modified/updated by Teruki Kamon for PHYS 627

Hadron Collisions at the Tevatron and the LHC 2

A little bit of EinsteinA little bit of Einstein……Recall the well-known equation:

Measure energy in “electron volts” = eV

(1 eV ≈ 1.6 x 10−19 Joule)

Measure mass in units of eV/c2…

(1 eV/c2 ≈ 1.78 x 10−36 kg)

…but often use units where c ≡ 1,

so mass can also be measured in eV

For a moving particle:

Total Energy = Rest Energy + Kinetic Energy

Ultra-relativistic: γ >> 1 can neglect rest mass

2222 )()( mcpcmcE γ=+=

2mcE =

21

1

βγ

−=

c

v≡β

22 1 mc)(mcE −+= γ


Fixed Target vs. Fixed Target vs. CollidersCollidersw/o calculusw/o calculus


Fixed Target vs. Fixed Target vs. CollidersColliders

Energy E

FixedTarget Center of Mass Energy

mEs 2=

Energy E Energy EEs 2=

Head-On Collision

ultrarelativistic limit

Compare protons @ 1 TeV:

Fixed Target: ECM = 43 GeV Collider: ECM = 2000 GeV

Big advantage for colliders! ⇒ Most efficient use of beam energy for physics!

Challenge to get a high collision rate to look for interesting (rare) processes

Fixed target still essential for secondary beams: antiprotons, kaons, µ’s, ν’s

w/ calculusw/ calculus



3.46 x 109

crossings

Aintσ

intσ intσ

Skip


LuminosityLuminosityLuminosity is measure of the collision rate in a collider

Units are cm− 2 s−1

Peak luminosity ~ 1.2 ×1032 cm− 2 s− 1

Goal ~ 4.0 ×1032 cm− 2 s− 1

10−24 cm2 = 1 barn; 1032 cm− 2 s− 1 = 360 nb− 1/hr

To reach higher luminosity…More beam

May be hard…Tevatron needs more antiprotons

Higher collision frequency (more bunches)Not for Tevatron – will keep using 36 bunches of protons and antiprotons

Smaller beamTevatron beams are ~30 µm wide at interaction pointsLinear colliders have nm size beams

All can be hard to achieve due to instabilities that may develop

Want high luminosity to study rare processesLuminosity × Cross Section = Event Ratee.g., 1 × 1032 cm−2 s− 1 × 10 pb = 3.6 events/hr

221

4πσNN

fL =

sizebeam is

beam each in particles # are

frequency collision is

21

σ

NN

f

,


Model of AcceleratorModel of AcceleratorAccelerating device + magnetic field to bring it back to accelerate again

+ =



Where is the Where is the FermilabFermilab??


Looking Down on the Looking Down on the FermilabFermilab Accelerator ComplexAccelerator Complex

CDF

D0

~5 mi.


Closely Looking Down on the Closely Looking Down on the FermilabFermilab

1 kmMain Injector

Tevatron

Wilson Hall

8 GeVBooster

980 GeVTEVATRON

150 GeVMain injector

400 MevLinac

750 keVCockroft Walton

Highest EnergyAccelerator

NuMI (120 GeV protons)MiniBoone

(8 GeV)

2

3

1

4

5

6

9

7

10

8


Machine Energies (Machine Energies (cc = 1)= 1)Comparing relativistic β, γ for electrons and protons at various energies…

rest mass

Machine KE β γ β γCockroft-Walton 750 keV 0.926794588 2.47 0.707389304 1.00

FNAL Linac 400 MeV 0.999999186 784 0.818829208 1.43

FNAL Booster 8 GeV 0.999999998 15657 0.994538328 9.53

Main Injector 150 GeV 1 293543 0.999980691 161

ILC 500 GeV 1 978475 0.999998247 534

Tevatron 980 GeV 1 1.918E+06 0.999999543 1046

LHC 7 TeV 1 1.761E+07 0.999999995 9596

VLHC? 100 TeV 1 1.957E+08 1 106611

electron511 keV

proton938 MeV

1 keV = 103 eV 1 MeV = 106 eV 1 GeV = 109 eV 1 TeV = 1012 eV

Mass of top quark ≈ 175 GeV


HiHi--rise Buildingrise Building

•25 keV H− ion source

•750 keV Cockcroft-Walton accelerator


CockcroftCockcroft--WaltonWalton

•25 keV H− ion source

•750 keV Cockcroft-Walton accelerator


H− ions

LinacLinac

Accelerate H− ions to 400 MeV

116 MeV Alvarez linac (201.25MHz)

400 MeV side-coupled cavity linac (805 MHz)


BoosterBooster

Booster: 8 GeV Synchrotron

Runs at 15 Hz

Stripper foil at injection removes electrons from H− ions

Accelerates protons from 400 MeV to 8 GeV

Most protons (>75%) going through Booster are delivered to MiniBoone (eventually NuMI)


Main Injector & Recycler RingMain Injector & Recycler Ring

Main InjectorRecycler


Main Injector (MI)Main Injector (MI)Replaced Main Ring (formerly in Tevaron tunnel)

Higher repetition rate for stacking pbarsSimultaneous stacking and fixed target running

Many operating modesPbar production: ~ 6-7 x 1012 120-GeV protons to pbar target

“Slip-stacking” – merge two booster batches of beam on 1 MI ramp cycle

“Tevatron protons/pbars”:

Accelerate 8 GeV to 150 GeV

Coalesce 7-9 proton bunches at 90% eff into “270-300 x 109 proton” bunch

Coalesce 5-7 pbar bunches at 75-90% eff into “20-80 x 109 antiproton” bunch

Transfer 8-GeV protons/pbars to the Recycler

Provide protons for neutrino production

8-GeV protons for MiniBoone

120-GeV protons for NuMI

120-GeV protons to Switchyard (fixed target area)


Debuncher

Accumulator

Debuncher Debuncher & & AccemulatorAccemulator

Two rings


PbarPbar (Antiproton) Source(Antiproton) Source

(1) > 6 x 1012 120-GeV protons per pulse strike Ni target every 2-3 sec;

(2) Li lens (740 Tesla/m) collects negative secondaries;

(3) Pulsed dipole “PMAG” bends pbars down AP-2 line to Debuncher

ε ≈ (14-18) x 10−6 pbars/proton on target

Pbars “debunched”, cooled briefly in Debuncher prior to Accumulator


PbarPbar (Antiproton) Source(Antiproton) SourceStack rate = 6-14 mA/hr

Depending on stack size; Limited by stochastic cooling systems in Accumulator

Transverse beam size increases linearly with stack size - That’s a drawback…

In a really good 24 hour period, nearly 200 x 1010 pbars can be accumulated.

Pbar Production Rate = 3.3 x 10−12 g/day (Mpbar ≈ 1.67 x 10−24 g)

800 million years to make 1 g of antimatter!


TevatronTevatron OverviewOverviewProton-pbar collisions (Ebeam = 980 GeV)

Revolution time ~ 21 µs

Virtually all of the Tevatron magnets are superconducting (Cooled by liquid helium, operate at 4 K)

150 GeV beams are injected from MIProtons injected from P1 line at F17; Pbars injected from A1 line at E48

36 bunches of proton and pbars circulate in same beam pipe, but separated by “electrostatic separators”

3 trains of 12 bunches with 396 ns separation (see the next page)

2 low β (small beam size) intersection points (CDF and D0)

8 RF cavities (near F0) to keep beam in bucket, acceleration1113 RF buckets (53.1 MHz ⇒ 18.8 ns bucket length)


Proton Bunch PositionsProton Bunch Positions3 trains of 12 bunches with 396 ns separation

P1

P12

P13

P24P25 P36


Protons and Protons and PbarsPbars at HEPat HEP

Collide @ D0

Collide @ CDF

Proton bunches

A1-A12A13-A24P25-P36

A25-A36A1-A12P13-P24

A13-A24A25-A36P1-P12

P25~P36

A24~P

13


ProtonProton--PbarPbar Collision PointCollision Point


First Collisions at the Tevatron

October 13, 1985

Run 493 Event 11

Run 493 Event 15

Large Large Hadron ColliderHadron Collider

HighlightsHighlights~27km circumference

1232 bends

Main bends are 14.3 meters long

The strength of each magnet is 8.33 Tesla

Huge synchrotron radiation loss.


2

3

2

22

3

22

22

2

ret

3

2

sin444

44

vc

eP

Θvπc

e)βn(n

πc

eER

π

c

dΩ

dP

nEπ

cBE

π

cS

R

)βn(n

c

eE

a

a

a

&r

&r&rrr

rrrrr

&rrr

=

=××==

=×=

⎥⎦

⎤⎢⎣

⎡ ××=

Accelerated charges produce radiation.

ττ d

pd

d

dE

c

r

<<1

22

4

BUm

qP ⎟

⎠⎞

⎜⎝⎛∝γ

m

qvBv

γ=&

2

32

2

6⎟⎠⎞

⎜⎝⎛=

dt

pd

cm

qP

r

επ ογ

Useful equations for ideal conditions in SI

Above we integrated over the angle Θ, and below switched to more familiar units SI

From here were can get if

Synchrotron RadiationSynchrotron Radiation

Go to, for example, Jackson’s Classical Electrodynamics book, find more convenient expression in terms of v, ρ, γ

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