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Semin.IFD/IPJ 06.10.06 1 Zakopane, June 06, HB Wounded Nucleons, Wounded Quarks, and Relativistic Ion Collisions Helena Białkowska Institute for Nuclear Studies Warsaw
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB2 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
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB3 The WNM (1976!) – as usual – started from experimental observation: 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
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB4 And this is just the ratio of participants in p-A (1 from p and from nucleus A) and in p-p (2 protons) Observation: ratio of multiplicities (hA/hp) behaves as
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB5 The Model: Particle production in a nuclear collision - a superposition of independent contributions from the wounded nucleons in the projectile and the target Thus you can: 1 just measure NN 2 count the participants in h - A 3 and you have particle multiplicity in h – A!
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB6 For p-A: works surprisingly well. from AGS energies up to RHIC! Notice: we check here both N part scaling and pp scaling
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB7 New idea: not wounded nucleons but wounded quarks Andrzej Białas et al., 1977, Vladimir Anisovitch et al., 1978
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB8 Additive Quark Model 1982 Białas et al.: Specific predictions for nuclear collisions on the basis of the Additive Quark Model - with particle production from three sources: Breaking of the color strings between quarks from the projectile and the target Fragmentation of wounded quarks Fragmentation of spectator quarks
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB9 Thus for central region Ratio of multiplicities in A-B to that in pp given by
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB10 Pre-history: 1980 P,d, ,C on Ta, 4.2 GeV/N JINR DUBNA Model: 3.0 Model 1.6 AQM
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB11 First real high energy nuclear beams: 200 GeV/c O and S from SPS K. Kadija et al., ZPhysC66,393(1995) consistent parametrization of production rates of negatives – proportional to the No of wounded nucleons and of kaons – proportional to wounded quarks More history: NA35
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB12 W N AB works for negatives … and it does not for K 0s
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB13 For kaons - need W q
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB14 Now for RHIC A – A data: Notice: AuAu scaled by pp at twice the energy! (to account for ‘leading baryon’) PHOBOS White Paper
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB15 Here it looks better but… read the fine print! AuAu normalized to e + e - Almost the same plot
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB16 Intriguing scaling/universality for multiplicity/participant ee pp AA central
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB17 Look more closely at total multiplicity per N part Proportionality, but higher than for pp at the same energy pp systematically lower WNM does not work for Au - Au
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB18 Still, the scaling with N part is surprising Au+Au 35-40%,N part = 98 Cu+Cu Preliminary 3-6%, N part = 96 62.4 GeV Cu+Cu Preliminary 3-6%, N part = 100 200 GeV Au+Au 35-40%, N part = 99 PHOBOS dN/d PHOBOS and not only for total multiplicities : :
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB19 Cu+Cu preliminary Au+Au PHOBOS Au+Au PRL 94,082304(2005) PLB578,297(2004) Cu+Cu PRL(2006) accepted This ‘geometric’ scaling with N part works not only for soft (low pt) data! (courtesy of Barbara Wosiek)
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB20 I jeszcze nowe dane: Gęstość barionów netto (ale tylko w midrapidity) też się skaluje z N part (PHOBOS, nucl-ex z 30.09.06)
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB21 A very specific come-back of WNM 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 contributions from WN in the projectile and the target Applies not only to the total charged multiplicity but longitudinal spectra also
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB22 Density of particles in A – B collision: The model requires And the first consequence is (F is a contribution from a single wounded nucleon)
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB23 A. Białas, W. Czyż, Acta Phys. Pol. B36, 905(2005) PHOBOS dAu 200 GeV
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB24 For full (pseudo)rapidity range: construct symmetric and antisymmetric component The Model predicts: where (c– centrality}
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB25 Symmetric and antisymmetric part of the inclusive xsection for several centralities dAu: centrality Comparison Model vs data (PHOBOS) for several centralities
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB26 Next step: Model looks OK for d hemisphere not so good for Au Next step: determine contribution from a single wounded nucleon
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB27 Two step particle production: 1.Multiple color exchanges between partons from projectile and target 2.Particle emission from color sources created in step 1 (AB+Marek Jeżabek, Phys.Lett.B590,233 (2004)) The contribution from one wounded nucleon extends over (almost) full rapidity range There is a big difference between its symmetric and antisymmetric part Authors interpretation:
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB28 Revival of wounded quarks concept for A - A S. Eremin & S.Voloshin, Phys.Rev.C67, 064905 (2003) As Recall: at midrapidity – increase of dN/d per participant with N part
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB29 Try N q-part instead of N Npart 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
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB30 Calculating N n-part and N q-part Mass numbers of colliding nuclei are 3 times larger, but their size is the same. For pp the same procedure with A=B=3, hard sphere R=0.8fm.
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB31
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB32 Compare N N, N q two versions of
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB33 Eremin & Voloshin Scale by nucleon participants Scale by quark participants increase perhaps slight decrease (full vs empty: different
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB34 How does it work at SPS? Netrakanti & Mohanty, PRC70(2004)027901 look at WA98 data 158 GeV/n Pb-Pb Nucleon participants Quark participants
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB35 Bhaskar De & S.Bhattacharyya PRC 71(2005) 024903 look at NA49 data (SPS) Notice log scale… nucleons quarks
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB36 Caveat: D & B write about ‘integrated yields’ in figure caption, but show integrated yields for p, K and midrapidity values for pbar, d (plots to be re-done by NA49)
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB37 Moreover... When you put together light and heavy nuclei, you see that Npart is not a good scaling variable for strange particles
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB38 Now for the energy dependence: R.Nouicer, nucl-ex/051244,2005 One step further: energy dependence R.Nouicer nucl-ex/0512044 Midrapidity charged particle density normalized to: Nucleon participants Quark participants
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB39 Again: Caveat The author normalizes pp data by the number of quark participants for ‘most central’ pp collisions Is this a correct procedue?
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB40 p+p 200 GeV (N q-part ) inclusive 2.4 (N q-part ) central 3.5 ( plot stolen from Barbara Wosiek, who noticed the problem)
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Semin.IFD/IPJ 06.10.06Zakopane, June 06, HB41 An attempt at a summary: Wounded nucleons remarkably successful in parametrization of global characteristics of particle production Nobody expects everything to be just a multiplication of N-N but the proportionality looks intriguing Wounded quarks - perhaps better scaling?
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