Wounded Nucleons, Wounded Quarks, and Relativistic Ion Collisions

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1 Zakopane, June 06, HB Zakopane, June 06, HB Wounded Nucleons, Wounded Nucleons, Wounded Quarks, Wounded Quarks, and Relativistic and Relativistic Ion Collisions Ion Collisions Helena Białkowska Helena Białkowska Institute for Nuclear Institute for Nuclear Studies Studies Warsaw Warsaw

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Wounded Nucleons, Wounded Quarks, and Relativistic Ion Collisions. Helena Białkowska Institute for Nuclear Studies Warsaw. What is a wounded nucleon?. Classic definition, given by Białas , Błeszyński & Czyż in 1976: It is a nucleon that underwent at least one inelastic collision. - PowerPoint PPT Presentation

Transcript of Wounded Nucleons, Wounded Quarks, and Relativistic Ion Collisions

  • Wounded Nucleons,Wounded Quarks,and Relativistic Ion CollisionsHelena BiakowskaInstitute for Nuclear StudiesWarsaw

    Zakopane, June 06, HB

  • What is a wounded nucleon?Classic definition, given by Biaas, Beszyski & Czy in 1976:

    It is a nucleon that underwent at least one inelastic collision

    Zakopane, June 06, HB

  • The WNM (1976!) as usual started from experimental observation:Series of Fermilab expt`s on h-Aalso European NA5and lots of emulsion dataAverage multiplicity and increases more slowly than the number of collisions

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  • Observation: ratio of multiplicities (hA/hp) behaves asAnd this is just the ratio of participants in p-A(1 from p and n from nucleus A) and in p-p (2 protons)

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  • 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!

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  • For p-A:works surprisingly well.from AGS energiesup to RHIC!Notice:we check here both Npart scalingand pp scaling

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  • New idea: not wounded nucleons but wounded quarksAndrzej Biaas et al., 1977, Vladimir Anisovitch et al., 1978

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  • Additive Quark Model1982 Biaas 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

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  • Pre-history: 1980P,d,,C on Ta, 4.2 GeV/NJINR DUBNAModel: 3.0Model 1.6AQM

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  • First real high energy nuclear beams:200 GeV/c O and S from SPSK. Kadija et al., ZPhysC66,393(1995) consistent parametrization of production rates of negatives proportional to the No of wounded nucleonsand of kaons proportional to wounded quarks More history: NA35

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  • WNAB works for negatives and it does not for K0s

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  • For kaons - need Wq

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  • Now for RHIC A A data:Notice: AuAuscaled by ppat twice the energy!(to account for leading baryon)PHOBOSWhite Paper

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  • Here it looks better

    but read the fine print!AuAu normalizedto e+e-Almost the same plot

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  • Look more closely at total multiplicity per NpartProportionality,but higher than for ppat the same energypp systematically lowerWNM does not workfor Au - Au

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  • Still, the scaling with Npartis surprisingand not only for total multiplicities ::

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  • PHOBOS Au+Au PRL 94,082304(2005) PLB578,297(2004) Cu+Cu PRL(2006) acceptedThis geometric scaling with Npart worksnot only for soft (low pt) data!(courtesy ofBarbara Wosiek)

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  • A very specific come-back of WNMA.Biaas & W.Czy, first presented in Zakopane in 2004:a two-component WNM to describe d-Au at 200 GeV/cBasic assumption:Superposition of independent contributionsfrom WN in the projectile and the targetApplies not only to the total charged multiplicitybut longitudinal spectra also

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  • Density of particles in A B collision:The model requiresAnd the first consequence is(F is a contribution from a singlewounded nucleon)

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  • A. Biaas, W. Czy, Acta Phys. Pol. B36, 905(2005)PHOBOSdAu 200 GeV

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  • For full (pseudo)rapidity range: construct symmetric and antisymmetric componentAnd compare to data:

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  • Symmetric and antisymmetric part for several centralities dAu:centrality

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  • Two step particle production:Multiple color exchanges between partons from projectileand targetParticle emission from color sources created in step 1(AB+Marek Jeabek, Phys.Lett.B590,233 (2004))

    Interpretation by the authors:

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

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  • Revival of wounded quarks concept for A - AS. Eremin & S.Voloshin, Phys.Rev.C67, 064905 (2003)As Recall:at midrapidity increase of dN/dhper participantwith Npart

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  • Try Nq-part instead of NNpartTo calculate: use same Nuclear Overlap Calculation(K.J.Eskola et al.,Nucl.Phys.B323,37(1989))as for N-N, but change density and s

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  • Calculating Nn-part and Nq-partMass 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.

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  • Compare NN, Nqtwo versions of

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  • Eremin & VoloshinScale bynucleon participantsScale byquark participantsincreaseperhaps slight decrease(full vs empty: different s)

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  • How does it work at SPS?Netrakanti & Mohanty, PRC70(2004)027901

    look at WA98 data 158 GeV/n Pb-PbNucleon participantsQuark participants

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  • Same trick at RHIC:

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

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  • 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)

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

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  • Now for the energy dependence:R.Nouicer, nucl-ex/051244,2005One step further: energy dependenceR.Nouicer nucl-ex/0512044Midrapidity charged particle density normalized to:Nucleon participants Quark participants

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  • Again: CaveatThe author normalizes pp data by the number of quark participants for most central pp collisionsIs this a correct procedue?

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  • p+p 200 GeV(Nq-part)inclusive 2.4 (Nq-part)central 3.5(plot stolen from Barbara Wosiek,who noticed the problem)

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  • An attempt at a summary:Wounded nucleons remarkably successful in parametrization of global characteristics of particle productionNobody expects everything to be just a multiplication of N-N but the proportionalitylooks intriguingWounded quarks - perhaps better scaling?

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  • DisclaimerI am fully aware that A-A collisions at high energy produce something that can not be fully described in terms of simple hadronic degrees of freedom and/or nuclear geometry

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