Quark matter '88, conference summary

Nuclear Physics A498 (1989) 355c-3FGc North-Holland, Amsterdam

QrJARK

MATTER

355c

‘88, C:ONFERENC:E

SUMMARY

Ii. KAJANTIE Department.

of Theordical

00170 Helsinki. 1. SOME

Physirs,

Some people

for the c~~~ark-gl~~o~l plasma

t,hink so, an anomymous

has been observecl,

it only remains

do not think an outsider certainly

coffee-time

t,o measure

C~onsicler the data” on asymmetric

symmetric about

colIisious

on K-

collisions

production

in central

of the type O+Au

S+S

p+A,

charge.

by

Probably

although

A+A

will be

data on the latter has

tlist,ribution

in rent,ral S+S

--+ x -+X

can be roughly

the Qriangulnr tlistribntion

near y = 0 in an average central

On top of that

nucleons

collision.

we could add 10 “nucleons”

although

pions per unit rapidity

Or about

100 pions of any

(= L?.(positives - negatives)

in

here the data so far is very preliminary.

One may now ask whet,her it is possible Transverse

but

for decades.

this experiment), produced

at 200 GeV/c.

would do as well,

You do not have to worry

(y is t.he CMS rapiclit,y) and we infer t,hat about. 33 negative are produced

But

vrry interesting

collisions

nurcle0i~s affect, your argument.

The clat,a for the rapidity parametrisecl

But, I

very compelling.

somebhing

or S+Au

to iderpret.

before the u1t.imat.e in asgmmdry,

been available

that

plasma

was quoted.

by the following simple numbers.

are so much easier

how t-he spectator

underst,oocl

stat~ement “quark-gluou

it,s propdies”

would agree wibh t~he statement

at tshis meeting?

stafse1-2

to the field would fiucl the evidence

and l~roniisillg is going on, as in&cat,& Data

20 C:

NUMBERS

Have we seen eviclenr~

he/she

Siltav~lorell~~ng~r

Finland

t,o fit. t,he 100 produced

pions and 10

of total

area z 100. 1.3 fm” + 10 - 2 fm” = 150 fmZ = 7r(7 fm)”

or of tot,al Volume = 120 fin3 in t,he initial Transverse

area = xRg = nf3.5

fm)” = 40 fin”

or Volume = 40 fm3 (assuming a longitudinal rapidity).

climeusiou

of 1 fm for these

The answer clearly is

0375-9474/89/$3.50 0 (North-Holland Physics

Elsevier Science Publishers Publishing Division)

B.V.

particles

wit,hin 1 unit

of

356~

WAY

NO The system factor

summary

K. Kajantie/Conference

has to expand

3 (or a combination

separate

ones.

particles-to-be still remains Usually

either transversally of bot,h), before

Initially

t,he system

strongly

overlap.

by a factor

2 or longitudinally

all the produced

particles

by a

can exist, as

t.hus must, have exist.ed in a st,at,e in which t,he

How close this st,ate is t,o the colour plasma

&ate

to be seen. the above qualitative

argument

mate for the initial energy density

is phrased

in terms of the Bjorken

esti-

(~0 z Ifm)

(2) and the previous essence

numbers

of t,he argument,

expanding

extended

2. EXTENDED

for S+S

correspond

is t,he same:

system,

somet,hing

the properties

to abollt, 1.4 GeV/fm3. ntw is going on.

of which we have to sort out,.

SYSTEMS

The physics we are doing, quark mat,ter physics, with t,he aim of studying containing

elements

- Particle

physics

- Nuclear

physics

- condensed

One might (including about

an extended

field,

science estimate

10% of the total

that

in total

about

in hot latt,ice particle

we broke up into parallel

500 experimentalists

QCD)

physics This sessions,

are engaged

population meeting

and 300 theorists

in this activity.

while t,he share was at,tendetl

This

of beam

is

time

by 250 ph)rsicists.

130 went, t.0 the experimental

and

6n to

one, GO spent) their time looking at posters.

To show some analogies, extended

int,erdiciplinary

physics

100 working

the theoretical

syst,em. It is a genuinely

physics

and cosmology

is less by an order of magnitude. When

could be called particle

from

matter

- Astrophysics - C!omputer

Bni, the

We have a hot,

let me give three examples

of some t,hroughly

stn~lir~l

systems:

Big Bang: This is clearly the biggest, ext,encled system we can st,udy and we stndy it from its interior.

It started

from an initial period dominated

some 3. 101’ s ago and was filled with quark-gluon neutrinos)

during the first, 10M5 s of its exist,ence.

now want to study. alternative

possible

Star developing

Unfortunately scenarios. to a supernova:

by effects of quantum

gravity

plasma (plus phot,ons,leptons It is this t,ruly ancient

and

period we

t.here is only one big bang, no way of observing

K. Kajantie/Conference

An interst,ellar the

end

until

behind.

cloud

the

core

In a truly

beginning made

to the

of each

condenses,

collapses,

impressive end.

mant,le

manner

After

of the

nuclear the

this

supernova

stages.

The

357c

summary

react,ions

st,art,

is blown

out

ent,irc

1987A

frequency

nuclear and

seyucnce

is burnt, star

is underst,ood

diagnost,ic

of these

fuel

a neutron

observations

ext,cnded

from

t,hc

have

systems

to

is left, been

is roughly

l/galaxy/century. Nucleus-Nucleus This created,

expands

different,. a star

we are st,ndying

as quark

In part,icular, remains

excitation these

collisions:

is the system

of the

syst.em

can

relat,ive

for

disintegrates

long

t,he collision,

be formed

wit,h a large

of stellar

10-3

?

Here

B is the nuclear

Not,e

the

vastly

contrast,

binding physics

(l/H=) only

the three

the

Hubble

Although so similar

the t,hat

concepts

directly

like

l

One

but

l

One

of many

scales:

\
Tnpl

10’9

100 t,he magnit,ucles

are

as given

given

in GeV

by t,he Planck

collisions

is ahnost

units.

mass.

scale

In

free:

!l?

(6)

1.5

(100)

c

t,o count.

increase

gravit.y

and t.he really

of fi

enters

and

is crucial

t.hereby

but

also

basic

t,hing

its effect

a vastly

is

only

different

mat,ter

the

luminosity,

we always to separate

ways

diagnostics

we picture has

line

the

a stellar

intensit,y

and

have

to face

the

great

signals

from

the

different,

phenomena

analogy: interferomrtry

quark

matter

phases

are

ast.ronomenter handicap:

of format,ion,

DIAGNOSTIC%

seem

wants

wants

side,

clisintegrat,ion.

art,ificial

actually

nosphere

But

the

posit,ive

0.2

so different,,

of quark

difficult.

and

It may

are

the

while

aft,er

at T z A.

t,emperat,ure,

STTPERNOVA

event,,

scales

work.

it. is extremely evolution

l/Hc

velocit,y,

lO’/s.

111

seem

The

are completely

conditions, On

is

A,T

cnt,ries

In cosmology

radius

much

in our

initial

around

in nucleus-nucleus

cent,ermost,

scales

is due to t,he exist,ence

and

RA and A,T.

10 between

N In s or ln’ s.

scale,

3.

frequency,

0.02

fact,or

the

the syst,em

wit,h light

hypothetical.

of gravit,y,

RA

Here goes

energy

magnit,ude

mat,ter

(lo-“0)

the

the

0.2

different

quark

Only

A

1” r , B

mu

ical

are

physics

scenario:

essent,ially Also

periods.

by

simplicity

an analogous

and disintegrates.

t,hc syst,em

stationary

systems

The

mat,ter

assuming

t.here

to

vs.

prove

quark

t,o compare are t)he

a supernova

1ot.s of parallels. existence

of

One

with might

something

matter

to measure

its temperat.ure

and

radius

a nucleus-nucleus

collision

mention

physically

expected,

neutri-

K. Kajantie/Conference

358~

The angular

l

resolutions

summary

are quite similar: SIZE

10 km =----m = 10-l’ 1O”ly

DISTANCE

10 fm =--zz 10P 10 111 (and actually

SNlS87A

l5

QM

would he the same for a supernova

in our galaxy)

A surface signal (the light. pulse from the supernova)

l

mation

from the interior

The diagnosis Lifetime

one needs infor-

by neutrinos)

went on roughly as follows:

:

This was measured pulse.

(carried

is useless;

to be z 10 s by directly

This clearly is something

one cannot

observing

reproduce

the length

of t,he neutrino

in heavy ion collisions.

Temperature: The physical core becomes system.

basis for the existence

of t,he neut,rinosphere

so dense t,hat the neutrino

On their way out the neutrinos

expects

their energy distribution

are thus t,hermalised

observed.

Folding

The neutrino

the observed

neutrino

exp(E,/T) cletertors

(3)

+ 1’

on thp earth

and thus only the high energy

the detector

efficiency

energies

and one

E;

nE,where T M 5 MeV.

by collisions

to be

dN

of the order of 10 MeV

is that the collapsing

mean free pat)h is less than the size of the

if, indeed,

had an energy

curve with the spectrum T z 5 MeV.

total

of 1O58 gave this result.

total

of lo3 pions but. st,ill the int,erpret,ation

In quark matter

physics

threshold

t,ail of the spectrum

And 10 neutrinos we observe

of the emission

was

(3) reproduced out of the

almost

process

all of a

is in no way

unique. Radius: If t,he surface temperature Thus the total energy carried

is T, the energy flux em&ted from t,he system is N T4. away by neutrinos

is

EtOt M N T4R2At. v ” On the other star =: O.lM~2.

hand, this must equal the gravit,at,ional binding energy of a neutron Observing t,he energy carried by the neutrinos crossing the eartlt

and knowing the distance The above results prove the analysis, da,ta.

Unfortunately,

permitt,ed

for instance,

by including

t,here is no way to initiate

and wait for the next, nearby much better.

one to measure

R z 20 km.

were based on first measurements

supernova.

cooling.

and one would like to imFor this one needs bet,ter

an experiment,

one just

must sit

In this respect, quark mat,ter physics

does

K. Kajantie/Conference summary

FICIJRE Emission

359c

1.

from a radial flow

4. TEMPERATURE,

FLOW

If we have an honestly

equilibrat~ecl syst,em, t.hen for sure (for bosons/fermions) dN

d3p

where d3p = xdyd& lisions thermalise

and E =

(2f)3

dpv

the photons

1

__-

-=

m

(or possibly

cash y. A st,ar is a prototype neutrinos!)

outside the star aft,er each photon has undergone It is an old observation

that

hadron

(4)

* 1’

exp( E/T)

spectra

example:

col-

and we observe the spectrum

a last, collision in the photosphere.

in hadronic

collisions,

integrated

over

y or at fixed y, behave like dN

@ Does t,he para.met,er temperature

It is very suggestive quanta

lG0 MeV

T z

T in (4)?

direct,

observed

in (5) have anyt,hing

to do with temperature.

t,he mere observat,ion

of the thermal-like

volume-related

dist,ribution?

is blue-shifted:

Wit,h nnclear system

becomes

collisions

is already

more credible.

spectrum

(or wit.11 ~11

far greater

than

Cllearly even here

(5) is no proof; one must find

effect,s. This is again in analogy

wit,h astronomy,

where

effect, one could study is collect,ive flow. How could t,his affect If a star is a disc approaching

the energy

and the T effectively cylindrically,

assumption

of

or at least

from the strict, t,hermal shape (4) give lot,s of information.

The first, modifying a t,hermal

for decades.

For t,hem t.he T in (5) is rat,her a reflection

size 1 fm of a hadron.

1 fm and t,he thermalisation more subtle

bo do with t.he

hypothesis

from a system of size 1 fm can have anything,

at large Nch) the size of t.he emitting

deviat,ions

(5)

).

T

but most people have refused to believe that the spectrum

of the nonperturbative collisions

&pi7

This has been a very cont,roversial

of size 1 fm emitted

anything

exP(--

from the flow motion

increases.

the modification

lls, t,he distribution

clearly

is added t,o the thermal

energy

If t,he flow is radial is more complex.

(Fig.l),

either

spherically

or

K. Kajantie/Conference

360~

If the replace

flow velocity

in the

now depends the

above

is v w&h

v G t,anh

fact,or

exp(-E/‘I’)

Boldzmann on the relative

situation

are

- p . v)/T

the

This

effective

type

temperat,ure

really

of concave

what,

integration is only

one over

make

the

y and

assume

outcome

ancl we have m=O:

= E/TcY.

= E/(T/ cash y). in E varies

< T clet.ermined with

in the

m # 0) and

interpretation

T at, small

small

p”T spect,rum

11~ and

(alt,hough

it, is clearly

and mnch

from

Doppler is affected

of flow.

effect.

T at large

large

it also

suggest,ive

furt,her

T,E =

a blueshifted

by t,he t,ransverse

But

experimental

data

spe&a

large

YT

by the

again,

this

is needed

to

numbers

of

c* J/$suppression on the

(in some

thermal

conditions

spectrum

(4)

emission)

lines.

stellar

An example’

have

is given

in Fig.

Q Leonis BlIb

0

The

flow is to

The

case.

intensities

Superposed absorption

of the

If t,hey are parallel

if we furt,hcr

= E(y - p)/T

of the spectrum

spectrum

observes

one possible

5. Line

and

y, t,he effect

E by y(E - p . v).

perpendicular,

TeY > T t.o the T,tf = T/co&y is just,

the

disc

y( E - p . v)/T Thus

y, y = cash

of p and v.

of an approaching

r(E If they

orient,at,ion

summary

cont~inuum/observe~l

435 nm

spect,rum

rat,io

for t,wo st.ars.

See bext.

2.

K. Kajantie/Conference

Here is 100)

the

r&o

ront,inuum/observetl

is plotted

of X near deeper

the

for two st,ars,

hydrogen

in the

lower

star

has

T z 25000

has

more

plasma,

and

thus

the

One very

inlplies

suppression

of work.

how

mat,ter

det,ail

about,

wit,h

on this

one

cornerst.ones

is one

of the

effect:

levels

split,

can 6.

This

lack

are some

day

and

upper

upper

one

n = 2 state

level

in great,

(what

is r(

and

to doubt,

physics

devotecl

J/q exactly

and

qp -

We

J/q?), how

/IP but since

E one

suppression

a cent,ury

by 99 -

from only

and

understood.

is not, surprising

have

that

after

.J/$ + p)?)

co~ues

niat,ter

plasma

is completely

det,ail

uniquely

that, a

In quark QC’D

(dominant,ly

Al it. for sure

data

more

of understanding

of unclerst,anding

nlatter

of the line.

is at. present,

product,ion

one knows

t,he

what.

we so far

year

of work

will one day be one

as al)sorption

line

suppression

of ast,rophysirs.

width

t,here

is much

the

the

in the

physics

t,o iniply

.J/,$ is produced

large

of t.he donGiant,

by expcrin~ei1t~al

t,he St,ark

line

is that

to this

atones

III stellar

the

not,hing

aft,rr (for

of quark

the

is it, caused

hydrogen

is understood

how

matter

rornerst,ones

Incidentally, nor

physics

I see no reason

of the

Due

and suppression

everyt,hing

set, of experiniental

problem.

for this

Ii.

ront,inuum

as a function

t,hat, t,he H,

reason

is conject,urrd

However,

behaves

Ad % 3 C:eV?). only

ET

underst,and

I~ackgrouncl

the

(bott,om)

oIlserves

The

less

so t,hat

68 Tauri

T zz 10000

has

plasnla

tnore

In quark

it, interacts

have

QED

physics

One

.I/$ suppression.

line.

J/i,

and

(normalised and

star. has

3Glc

is suppressed. t,o

more

In stellar

in any

&muon

line

(top) nm.

lower

ionised

collisions

of t,he

different..

the

is nlore

in nuclear

at 435

in t,lie upper

has an analogy

hot star

do not

than

int,ensit,y

(1 Leonis

line

Ii while

absorpt,ion

thus

physics

H,

summary

are

so strong

t,he lines

be observed

line in Fig.

or l>opplrr

electric

broadened.

also

H,

resoliit.ion

fields

Maybe

in quark

niatter

2 is not

the

I~roatlening.

in stellar

intrinsic

one

Jt. is caused

atmospheres

this kind of detailed

that,

by t,he

phenonlenon

physics.

INTERFEROMETRY This

is one of t,he unexpect.ed

Although st,utly,

we cannot, we ran

direct,ly

observe

them

classical

ast,ronomy.

Stellar

can

the

sizes

give

angular

and excit,ing observe

the

indirectly discs

via

cannot,

for nearby

developnients

dinlensions

in quark

interferomrtry. be

stars.

observed

The

matter

of t.he ext,ended

llnclrr

this

is also

If anything directly,

st,andard

but

physics.

systenl

interfernmetr~

interferonletric

condition

is size of st,ar dist,anre where

also

t,ypiral

wavelength quark different

gives

nlatt,er scales.

stellar

values

a nieasurelnent,

physics Now

size of det,ect,or

t,o st.ar

wavelength in ni are cluot,etl. of the

t,he fundamental both

size

angular

I?[!.

of det,ector

ZZ

1_‘o” N

1 10’6

(!hanging size

(6)

lo-” size of detector

(size/dist.ance)

of the

(6) st,ill l~o1tls, but again M distance

t,o object

with

at fixed star.

In

complet.ely

N” 1 m so that,

the

K. Kajantie/Conference

3mc

condition

(6) demands

that

summary

size of objc=ct/wavelength

z

1, usually

written

in the

form AZ. Ak = 1. However, system

even in this application

is ext,remely

interferometry

we have to face t,he fact that

time dependent,.

is straightforward

vrry complex

and non-unique

results

obtained

is plotted

and unique.

of an expanding

of the transverse

to see a 20 MeV scale appearing The angular surements

resolution,

line interferometric of course, 7. A+B

radioast,ronomy

ClOLLISIONS

The experimentsal indicat,ions system

10-l’.

of QC:D plasma,

showed that the charged

For example,

N,h collisions

the pT distribution small (large)

emit,ting

collisions up

t0

but t,his int.erpretation

is not unique.

fluctuat,ions

in p + p collisions

x

collisions

4 GeV/fm3

28 were observed. for the Tevatron

energy densit,ies as A+B

collisions

at the C:ERN ISR 10. Similarly, T,E at

can also produce

are large rompared at, fi

= 1800 CieV impressively

collisions,

they still lack t,he t,ot,al large volame

in A+B

it would t,hus be important

collisions

for J/d] suppression.

even there if Nch is large enough.

in A+B event,s

experiments. estimated) at~tainable to check all

also in large Nch p + p collisions.

It has so far not been tested

but it is by no means excluded t,hat t,his suppression

of the phenomenon.

with those

= 20 GeV t,he data runs out before

at, large Nch seem t,o have as large (naively

effect,s observed

This holds, in particular,

t,hese result,s is that

The est,imat.e (2) then gives energy densit,ies

To really sort out volume effects,

the int,eresting collisions,

measurements

pions grows from 1 fm t,o 2 fm when

while in the new Tevat,ron dat,a at, fi

Albhough p + p collisions in A+B.

are observed in p+p

pi.

7(dN,h/dy)

of about

several

of an extended

at large Nch has t,he concave shape wit,11 a small (large)

at large A,B. In O+Au

2(dN&/dq)

contain

grows from the average 2 to about

The reason why p + p (or p + JT)collisions multiplicity

is,

with the behaviour

interferometric

the size of the system pion rapiclity density

The good resolut,ion

on A+R

However, it also seems that many of these phenomena at large multiplicit,ies.

mea-

att,ained in very large base-

AT LARGE

or BNL

which are compat.ible

and the appearance

physics rontext,!

M l/tnrr, used.

VS p + p ClOLLISIONS

of phenomena

funct,ion

in t,hese heavy ion interferometric

are today about

data from C:ERN

suggestive

t,ransfer it is quite impressive

The best resolutions

caused by the small wavelength,

even surprisingly

in a particle

attained

is also quite impressive.

in which

Still, the experiment,al

When the t,wo-pion correlation momentum

naturally

10-15,

phase space.

and perhaps

syst,em.

of

In quark mat,ter physics one is lead to

ecluat,ions and t,o a very lengt.hy data analysis,

so far are very suggestive

as a function

our extended

A st,ar sits there calmly and the applicat,ion

the signal is found in a tiny part of t,he accessible of the behaviour

(‘i)

in p + p

would not be observed

This would shecl new light on the interpretations

K. Kajan tie/ Conference summary

8.

THEORY 8.1.

Hot

The

lat,tice

actually In

363c

lattice

formulation

quit,e

view

simple,

of the

as the att,empt.s

of finite

but,

of the

to first

Ising

perform

computations.

of confinement

solut.ion

so far

to

such

a simple

simplification

and

been

discovered can

only

only

and

statistical There

model have

embark

the

at, present

and

quantitatively.

them

preserving

be obtained

compact

solve

be no surprise.

no approximation

on nu-

crucial

it, seems

property

t,hat

by a numerical

been

realiable

solut,ion

of t,he

t,heory. the

study

of finite

T QC!D

of latt,ire

Act,ually

Monbe

C!arlo

met,hods,

since

exist,ence

of a phase

an

of magnitude)

order

contrasted

with

has

been

the

equat,ion In

spite

transition,

is no systemat,ic

no means

and

energy

screening

dependent, modes, QclD

scale

Q

?_’+ p 3 range

have have

QClD

the

by

is t,o be which

prediction

for

-

new are

effects

that

one

problem

*

st,udied.

and

is

still

There

so

t,he problem

by

made

seems

it is quite

t,hese

surface

C’learly before

can

be

in the real

limit.at,ion

world

of what

wit,11 real happens

t,ime.

in the

t,o heavy t,ime

it, does

This

not

would

phase

viscosity

on t,he time

applied on real

is that.

in

ent,ropy

shear

lot,.s of assumptions

these

limited

t,he pressure, energy,

t.o give us no information

A related

int,uit,ion

formulation,

ion

collective

say

us what

be very

useful

t,ransition.

t)heory

>> A.

For + X

example, at

entirely key

&=

fragmentation

from to the

t,heory

theory

< ET < 100 GeV The

This

it. seems

det,ails

volllme

(the

change

t,ime.

QC!D

if the

sllscept,ibilit.y,

studied.

QCTD is t,he correct

jet,(&)

a computation functions,

been t,o be

also

like”

physical

that,

lattice

success

spectrmii,

t,o verify

Among

quantities.

number

of QCTD perturbation

5 GeV

experiment,.

is a complet,e

oscillations.

Perturbation

successes

Clarlo

quark

“looks

We know

lat,tice

syst,em

mass

t,ake a long

completer

et,c.,

finit,e

ec~uilibrium

Latt,ice

in developing

better

of the

us only lengths

matter

-

THE somet,hing

in advance.

remains may

of hot

problem,

density,

like plasma

8.2.

nlonte

dynamics

collisions.

this

in the

the hadron

it, still

and

problem a new

densities

to reproduce

be called

predict,ecl

with.

latt,ice

in giving

density,

not, measurctl

has

successes

cont,rol

is dealt,

Although

one

Of course,

circle

-+ again

could

one has really

various

experimentally

of tShe qualit,ative

computer

on t,he lat,tice here

in which

att,empls

for decades.

of st,ate

in a vicious

better

scope

which

the failing

known

t,rapped far

should

is complete,

problem

of even

t,his

an analyt.ir

consequences

QC!D

a formidable

model,

However,

has

nonpert,urbat,ive

temperature

present,s

complexit,y

t,wo dimensional

mrrical

full

QCD

when

the

prediction

540

GeV

first

is that, can

over

ra.te

of the

9 orders

something be

fact.orrd

from

with

inclusive Actually

must, soft the

a large process

of magnit,ude

alwa,ys

t,he uncomput,able

quantitative

physics

well wit,11 experiment,.

principles;

mechanisms)

of the impressive to pnrt,icle

of the

varies

and agrees

success

because applied

over

be t,aken

parts

t,he

t,his is not from

(structure

comput,able

hard

K. Kajantie/Conference

364c

parts

(QCID

radiation,

computable The tially

part

present

on the

collision).

permits

heavy

uncomputable Iris,

At,tila,

and

make

further

predictions.

grow

with

energy

so that

the

0 t,he relevant,

where

<

matt,er

the

where

size

screening of these

system

thus

of this

are

9. EARLY

extends

the

evident,

writt,en,

that,

at, RHIC!

the

depend

t,han

essen-

it woldd

not

programs

(Fritjof,

reproduce hard

be

t,he clata

comput,ahle

part

energies.

originally

T >

about

hoped

A?

At, T =

for.

scaling

over clist.ances

starts

to work

(and

< 0.2 fm.

In hot

QClD

are:

and

l/g?’

and

a conjectured

small

experiment,ally

perturbative

The

scales

1 /$‘I’

form coupling

only

t,he l-loop

const,ant

are essent,ially

pert,urbative

are

of t,he magnetic

of the length.

g is, in practice,

the same.

The

always

to T = 0 the

In contrast

< l/T.

at. clist,ances

value

screening

full implications

UNIVERSE we already

have

t,o T z and

t.he period

annihilated.

of the

as thermalisation

goes

consequences A handle

+

The

nucleosynthesis.

lever

hadron

The

was the

could

events

arm

good

phase then

quark

was

earlier

even

phase

weak

of a&on

hleV,

of 10 km

10’“frn

=

10”

than

out. somet,hing early

and goes t,ransition

period

interactions

must,

at, T ‘V 200

in today’s

at that

though,

-+ hadron

find

nucleosynthesis

well-underst,ood

lot,s of action:

by a factor

is to

be observed

t.his

period

t,ransition

is better

problem

long,

Act,uallg

s.

of and observational

t,he light, element

at, a dist,ance

in t,he Universe

is very

underst,anding

during

t,here

next

t,he situation

now

of which on the

t zs 100 The

Universe

Act,ually

collisions.

and

t M 1 s, when

1 MeV, e*

of t,he quark

horizon

a reasonably

on in the ITniverse

T E 0.1 MeV

when

decoupled

gest,ed.

and

on what, was going

period,

on

so far unknown.

We believe handle

at which

of t,he syst,em

being

of soft, QC!D

been

complicat,ed

are non-pert,urbat,ive. st,arts

BNL that

so well at, T = 0 for 42 >> A, what

scales

t,he t,hree

and

not, mean

array have

It is also

is thus

length

crucially

are as follows:

scale

system

corresponding

1 and thus

The

is the

The

L is the

Both z

1 GeV

1).

Hijet)

t,o be more scales

depencls

C!ERN

does

it will be sizable

works

seems

distance

Qo x

o(~(Q~)

electric

theory

situation

st,ill

from

This

an impressive

will

If pert,urbation

ion data

Marco,

well

Here

result

it.

physics.

understood;

MCIFM,

The

us to test

experimental

soft

phenomenologically Venus,

hard

and

summary

have t z

been

10

and

’ 5.

RS far

in heavy

ion

non-thermal,

the

Universe. time

has been

via the period may

create

recently

of light

sug-

element

inhomogeneities,

K. Kajar tie/ Conference summary

which sion

lead

to a separation

propdies.

This

t,he lever like

arm

-

and

difficulty

hadron

are

phase

differ

clarify

transition

physics: IO.

by

because

of their

nucleosgnthesis

abnnclancies

different

cliffu-

and t,oday’s

of primordial

a factor

it reveals

no firm knowledge

and can only formulate

t,hey

only 10

situation

light

end of

element,s

apply

do justice

mankind

scenarios.

t,o equilibrium

can

of t,hr birt,h

sales

of the

of the gauge

quark

met,hods

Alt,hough

hopefully

to t,lie standard

t,he secrets

Lattice

methods.

I8 , heavy _ ion collisions

and

of the kinetics

t,he time

in t,he end

argument

for

help

part,irle

ITnivrrse.

FITTtlRE In trying

plasma and

to correctly

it may

finally

were

preclictecl

large

was

sit,uation were

ISR,

which The

know

goilig

had

moral

quit,e

that,

with

after

for

the rewards

t,hat, proper that

CXRN

we gain is shown has

S+S

pidare

been +

proper

past,ecl

dill

A and

had

at. the have

and

t,he

tortuous.

stadecl

The operating.

but

also

t.o be satisfied: When

proper

at

the

A and

must is

mat t,er physics larger

tliagnost,ic

A possible

one

equipment

In quark

larger

correct.

JS?

st,udying

although

ohServed.

collider

br great,.

means

the

been

t.ime.

equipment,.

suddeuly

missing

larger

in Fig.

4.

It, is

method.

scenario

for

t.lie pion

3. t,ogether

~~~ + X,

of A+A

t,he value

from

both

be

for

and jet,s

was well set for

difficulty lid

1,p collider

condit,ions

equipment

we st,ill are

st,age However,

cOidd

for a long

may

The

searched

in 1972-3

hat1 already

operating.

just,

clarity

for them

heing

t.0 br extremely jet.5

the

extreme

and one must, have

clear

figure

collision

in 1982

hIit,

for quark-gluon

predicted,

into

iii 19i5.

soon

proved 12~

were

and Fermilab

start,ed

search large

searching

corrrrtly,

could

dat,a

SPS

in t,hr search

came

mat.ter

ISR

of t,his is t,hat, t,wo obvious

densit,y

This

(for

seen

possible

What, rapid&y

only

been

how to look

it is rat,her

and quark

at

sit,uat.ion of how jets

freedom

the C!ERN the

011

suddenly

t,o look

ing:

both

and CERN

was solved

Jets

aged

t,liereafter

was so obvious,

fblii&ilig

present. oneself

and asympt,otir

since

phenomena

prediction

also

soon

th?

to remind

QClD

of jet,s,

pr

assess

be useful

found.

t,he search

from

surprisingly

(which

implies

at, y = 0 increases

the following good

scaling

by a factor

facts

validity

heard

at, this

meet-

of t,he independent

as A413 ), the

2 and t.liat, t,liere

Tevatron

N+N

observation

is an ext,endetl

plateau

(~1 < 2.8). Even

st,aying

energy

density

perhaps CERN

even

an increase the

at &= (Eq.

more

is st.rong

the rapiclit.y with

prot,ons

element

of cosmic

is t,hat. we have

since

the

and

light

‘Li.

hear

of no help,

scales to

is an observat,ion

deut,erium The

of neutrons

in t,urn affds

3G5c

(2)

of 5” 50% increasing

Fig.

importantly,

indeed.

plateau,

20 CieV but going and Going

t.o large

A, A = Pb,

3 wit.11 (12~) = 0.4GeV in volume.

furt,her

The

case

to t,he RHIC

for the Pb+Pb

energy

inrreases

hot.11 it.s heights and also

in energy

densit,y,

broad

rapidity

but probably

plateau

say, one thus

gains

give F, zz 5 GeV/fm3) of &=

< ~q

>.

experiments 200 GeV

This

could

t,he most, import,ant,

t,he interpret.at,ion

in

and,

opens

at, up

add up to gain

of t,he result,s

is that,

becomes

3FGc

K. Kajantie/Conference

dN/dy

t

-6

Possible more And

pion

rapidit,y

straight~forward, with

nuclei

will have

reached

Providd almost,

(all charges)

and

lead

t,he Brookhavrn

A+h

I~rcomc

beam

collisions

0l)vious

at, larger

expcriment,al

t,lre field of quark

predict,

(fixed

heavy

wc shall

This

t,he properties

as no one could

predict.

t.argrt

ion collider

in schrcliile,

by the end of t,his century. just

6

mat,ter

JS fact,s.

physics

mat,urity.

we cannot

Lagrangian,

in ceidral

at, J s in t,he TeV range,

can he const,ruct,ed

physics

3

Y

hint,s of new phenomena

colliding

20 GeV),

necessary:

clensit,ies

0

t,hat, hot.11 t,he ClERN

= 100 GeV) esting

-3

summary

l’l~+F’h (Au+Au

learn

at, fi at. fi

a lot, of new

experimeltt,al

of quark-gluon

collisions collisions

guidance plasma

superconductivity

from

ant1 in&-

is absolutely from

the

bhe Q(!D

Schriidinger

ecpat,ion. REFERENCES

1)

Proceedings Physics

2)

of Quark

Matt,er

‘86, etls. I,. S. Srhrordcr

Proceedings

of Quark

fiir Physik

C138 (1988).

Mat,ter

‘87, etls.

3) John Harris, this volume. 4) Clharles J. C:owley, The Theory Publishers,

and M. Gyulassg,

Nuclear

A461 (1987).

New York)

Fig.

H. Satz,

of St,ellar

2-1.2.

Spedra

II. J. Specht)

(Gordon

and

R. Stock,

and Breach

Z.

Science