wounded nucleons wounded quarks and relativistic ion ... · wounded nucleons, wounded quarks, and...

11Kraków, 18/05/2007, HBKraków, 18/05/2007, HB

Wounded Nucleons,Wounded Nucleons,Wounded Quarks,Wounded Quarks,and Relativistic Ion and Relativistic Ion

CollisionsCollisionsHelena BiałkowskaHelena Białkowska

Sołtan Institute for Nuclear StudiesSołtan Institute for Nuclear StudiesWarsawWarsaw

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 22

The Founding Fathers:The Founding Fathers:

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 33

What is a wounded nucleon?What is a wounded nucleon?

• A.Białas, M.Błeszyński, W.CzyżNucl.Phys.B111, 461 (1976)

`It is a nucleon that underwent at least one inelastic collision’

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 44

The WNM (1976!) The WNM (1976!) –– as usual as usual ––started from experimental started from experimental

observationobservationss::• Series of Fermilab expt`s

on h-A• also European NA5• and lots of emulsion data• Average multiplicity and

increases more slowly than the number of collisions

ηddn /

hAhpA σσ=ν /

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 55

Observation: ratio of multiplicities (hA/hp) behaves as

21 ν+=><>=< hphAA nnR /

And this is just the ratio of participants in p-A(1 from p and ν from nucleus A) and in p-p (2 protons)

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 66

The Model:The Model:

Particle production in a nuclear collision -a superposition of independent contributionsfrom the wounded nucleons in the projectileand the targetThus you can:

1 just measure NN2 count the participants in h - A3 and you have particle multiplicity in h – A!

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 77

0 2 4 6 8 10 12 14 160

2

4

6

8

E178b)

partN21

= A R

chp

p/N

ch=N

AR

⟩ part N⟨

200 GeV d + Au

200 GeV d + Au Min-Bias

+ Pb+ K

+ Pb+π p + C

p + Cu

p + Pb

For p-A:works surprisingly well.from AGS energiesup to RHIC!

Notice:we check here both Npart scalingand pp scaling

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 88

New idea: not wounded New idea: not wounded nucleons but wounded quarksnucleons but wounded quarks

Andrzej Białas et al., 1977, Vladimir Anisovitch et al., 1978

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 99

Additive Quark ModelAdditive Quark Model

1982 Białas et al.:Specific predictions for nuclear collisions on the basis ofthe Additive Quark Model - with particle production fromthree sources:Breaking of the color strings between quarks fromthe projectile and the targetFragmentation of wounded quarks Fragmentation of spectator quarks

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 1010

Thus for the central region

Ratio of multiplicities in A-B to that in pp given by

ABqq

qBqABARσσσσ

=),(

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 1111

PrePre--history: 1980history: 1980

AQM

2.06.3 ±=dTaCTa Model: 3.0

1.07.1 ±=dTaTaα Model 1.6

P,d,α,C on Ta, 4.2 GeV/NJINR DUBNA

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 1212

First real high energy nuclearbeams:200 GeV/c O and Sfrom SPS

More history: NA35

K. Kadija et al., ZPhysC66,393(1995)consistent parametrization of production rates ofnegatives – proportional to the number ofwounded nucleonsand of kaons – proportional to wounded quarks

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 1313

WNAB works

for negatives

… andit does not

for K0s

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 1414

For kaons- need Wq

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 1515

Now for RHIC A – A data: PHOBOSWhite Paper

Notice: AuAuscaled by ppat twicethe energy!(to account for ‘leading baryon’)

s2

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 1616

Almost the same plot

Here it looks better

but…read the fine print!

AuAu normalizedto e+e-

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 1717

Intriguing scaling/universality for multiplicity/participant

ee

pp

AA central

Energy dependence

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 1818

Look more closely at total multiplicity per Npart

for Au - Au

Proportionality,but higher than for ppat the same energy

pp systematically lower

WNM does not work

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 1919

Still, the scaling withStill, the scaling with NNpartpartis surprisingis surprising

and not only for total multiplicities ::

Au+Au35-40%,Npart = 98

Cu+CuPreliminary

3-6%, Npart = 96

62.4 GeV

Cu+CuPreliminary

3-6%, Npart = 100

200 GeV

Au+Au35-40%, Npart = 99

PHOBOS

dN/dηPHOBOS

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 2020

PHOBOS Au+Au PRL 94,082304(2005)PLB578,297(2004)

Cu+Cu PRL96:212301(2006)

This ‘geometric’ scaling with Npart worksnot only for soft (low pt) data!

Cu+Cupreliminary

Au+Au

dydp/NdNdydp/NdR

Tpp2

coll

TAA2

AA =

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 2121

Still new data:Still new data:

also scaleswith Npart

Net baryon density at midrapidity

PHOBOS, PhysRev C75:024910,2007

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 2222

A very specific comeA very specific come--back of back of WNMWNM

A.Białas & W.Czyż, first presented in Zakopane in 2004:a two-component WNM to describe d-Au at 200 GeV/c

Basic assumption:Superposition of independent contributionsfrom WN in the projectile and the targetApplies not only to the total charged multiplicitybut longitudinal spectra also

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 2323

Density of particles in A – B collision:

)()( yFwyFwdy

dNBBAA

AB +=

)()( yFyF AB −=The model requires

(F is a contribution from a singlewounded nucleon)

And the first consequence is

)(21)0( BAAB wwyR +==

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 2424

R (y = 0)Au-d

8

7

6

5

4

3

2

1

W +W

2Au d

W +W

2Au d

1 2 3 4 5 6 7 8 9

PHOBOSdAu 200 GeV

A. Białas, W. Czyż, Acta Phys. Pol. B36, 905(2005)

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 2525

For full (pseudo)rapidity range: construct symmetric and antisymmetric component

ηη

ηηη

ddN

ddNG )()()( −

±=

aa )(2

)( ηη ++ Φ+

= dAu wwG )(2

)( ηη ++ Φ+

= dAu wwG

The Model predicts:

where

2/][)()( c

dcAuc

cc

wwG

+ΣΣ

=Φ+

+ ηη(c– centrality}

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 2626

Symmetric andSymmetric and antisymmetricantisymmetric part part of the inclusiveof the inclusive xsectionxsection for several for several

centralitiescentralities dAudAu::ηddN

cent

ralit

yη

Comparison Model vs data (PHOBOS)for several centralities

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 2727

Next step: Next step:

)()0()( ppddNRdAu

ddN

dAu ηη−

Model looks OK for d hemispherenot so good for Au

Next step: determine contribution from a single wounded nucleon

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 2828

The contribution from one wounded nucleonextends over (almost) full rapidity rangeThere is a big difference between its symmetricand antisymmetric part

Authors interpretation:

Two step particle production:1. Multiple color exchanges between partons from projectile

and target2. Particle emission from color sources created in step 1

(AB+Marek Jeżabek, Phys.Lett.B590,233 (2004))

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 2929

Revival of wounded quarks Revival of wounded quarks concept for A concept for A -- AA

S. Eremin & S.Voloshin, Phys.Rev.C67, 064905 (2003)

As Recall:at midrapidity –increase of dN/dηper participantwith Npart

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 3030

TryTry NNqq--partpart instead ofinstead of NNNpartNpart

To calculate: use same Nuclear Overlap Calculation(K.J.Eskola et al.,Nucl.Phys.B323,37(1989))as for N-N, but change density and σ

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 3131

CalculatingCalculating NNnn--partpart andand NNqq--partpart

partnN −

fm53.0dfm)A86.0A12.1(R

fm17.0n]d/)Rrexp[(1

n)r(n

3/13/1

30

0A

=−=

=

−+=

−

−

}]A

)s(T1[1){bs(sTd

}]B

)bs(T1[1){s(sTd|N

AAinelNN

B2

BBinelNN

A2

ABpartn

rrr

rrr

σ−−−+

−σ−−=

∫

∫−

)zb(dzn)b(T 22A∫

+∞

∞−+=

partqN −

30

q0 fm51.0n3n −==

9/inelNNqq σ=σ

Mass numbers of collidingnuclei are 3 times larger,but their size is the same.

For pp the same procedurewith A=B=3, hard sphere R=0.8fm.

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 3232

0 2 4 6 8 10 12 14 16 180

200

400

600

800

1000

1200

par

tN

Impact parameter b (fm)

Nucleon

a)

Constituent Quarks

: Au+Au at 200 GeVn-part

N

: Au+Au at 130 GeVn-part

N

: Au+Au at 62.4 GeVn-part

N

: Au+Au at 19.6 GeVn-part

N

: Au+Au at 200 GeVq-part

N

: Au+Au at 130 GeVq-part

N

: Au+Au at 62.4 GeVq-part

N

: Au+Au at 19.6 GeVq-part

N0 1 2 3 4 5

350

355

360

365

370

375

380

par

tN

Impact parameter

Nucleon

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 3333

Compare NCompare NNN,, NNqqtwo versions of qqσ

0

200

400

600

800

1000

1200

0 2 4 6 8 10 12 14 16b (fm)

NN-part

Quark participantsNucleon participants

(a)

0

0.5

1

1.5

2

2.5

0 50 100 150 200 250 300 350 400NN-part

Nq-part/NN-part

(b)

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 3434

Eremin & Voloshin

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 50 100 150 200 250 300 350NN-part

(dNch/d

η)/(

<Npart>/2)

- √s=200 GeV

- √s=130 GeV

Scale bynucleon participants

increase

Scale byquark participants

perhaps slight decrease

(full vs empty: different σ)

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 3535

How does it work at SPS?Nucleon participants

0.6

0.8

1

1.2

1.4

chγET

((dN

,dE

T)/

dη)/

NN

-par

t

0

0.2

0.4

0.6

0.8

1

0 50 100 150 200 250 300 350 400NN-part

((dN

,dE

T)/

dη)/

Nq-

part

Netrakanti & Mohanty, PRC70(2004)027901

look at WA98 data 158 GeV/n Pb-Pb

Quark participants

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 3636

Bhaskar De & S.Bhattacharyya PRC 71(2005) 024903look at NA49 data (SPS)

nucleons

Noticelog scale…

quarks

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 3737

Caveat:

D & B write about ‘integrated yields’ in figure caption,

but show integrated yields for p, Kand midrapidity values for pbar, d

(plots to be re-done by NA49)

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 3838

Moreover...

When you put together light and heavy nuclei,you see that Npart is not a good scaling variablefor strange particles

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 3939

Now for the energy Now for the energy dependence:dependence:

R.Nouicer, nucl-ex/051244,2005

One step further: energy dependenceR.Nouicer nucl-ex/0512044

Midrapidity charged particle density normalized to:

Nucleon participants Quark participants

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 4040

Again: Caveat

The author normalizes pp databy the number of quark participantsfor ‘most central’ pp collisions

Is this the correct procedure?

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 4141

1 10 210 3100

1

2

3

4

5

-0.02 + 0.27 ln (s)

/2)

⟩p

art

N⟨/(η

/dch

dN

(GeV)NN s

) + p p p(

A + A

)n-partAuAu (norm. N) n-partCuCu (norm. N n-partPbPb (norm. N

)n-part

p (norm. Np)n-partpp (norm. N

)q-partAuAu (norm. N) q-partCuCu (norm. N q-partPbPb (norm. N

)q-part

p (norm. Np)q-partpp (norm. N

p+p 200 GeV(Nq-part)inclusive ≈2.4

(Nq-part)central ≈3.5

(plot stolen from Barbara Wosiek,who noticed the problem)

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 4242

SpinSpin--off/extensions:off/extensions:

• `Used nucleon model’• `Wounded quarks and diquarks’

• `Dissipating energy participants’(E.Sarkisyan, A.Sakharov)

A. Bzdak, A.Białas (next talk)

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 4343

For pp: ‘practically’ only single quark contributesFor central AA: ‘practically’ all 3 quarks from each nucleon contribute

(Sarkisyan&Sakharov)

Note differentenergy scale:

Kraków, 18/05/2007, HBKraków, 18/05/2007, HB 4444

An attempt at a summary:An attempt at a summary:

Wounded nucleons remarkably successful in parameterization of global characteristics of particle production

Nobody expects everything to be just a multiplication of N-N but the proportionalitylooks intriguing

Wounded quarks - perhaps better scaling?