Low-Q 2 Partons in p-p and Au-Au Collisions Tom Trainor ISMD 2005 – Kroměříž, CR August, 2005

Trainor2 Agenda Survey of p-p correlations Fragment distributions on (y t,y t ) in p-p Fragment distributions in Au-Au Angular correlations on (     ) in p-p Angular correlations in Au-Au p t correlations in p-p and Au-Au QCD from the bottom up

Trainor3 Low-Q 2 Partons in p-p Collisions subtract soft reference minijet fragments  √  ref √  same side 1D 2D p-p 200 GeV n ch =1 n ch =10 pt  ytpt  yt p t (GeV/c) string fragments away side hadron p t ~ 0.5 GeV/c y t1 y t2  √  ref n ch parton fragments minimum-bias: no trigger condition

Trainor4 Analysis Method (y t1,y t2 ) correlations (         ) correlations  √  ref modified Pearson’s coefficient: normalized covariance density in each 2D bin:  – bin size number of correlated pairs ‘per particle’ autocorrelations can be determined by pair counting or by inversion of fluctuation scale dependence joint autocorrelation on two difference variables average over a on k th diagonal x1x1 x2x2 k a+k a xDxD xSxS k (y t,  )            

Trainor5 p-p Correlations on (y t1,y t2 ) ASSS SS – same side AS – away side LS – like signUS – unlike sign string and parton fragmentation: first two-particle fragment distributions p t (GeV/c)  √  ref HBT string away-side parton fragmentation is independent of charge combination same-side parton fragmentation restricted to US pairs parton (except OPAL on  ) string

Trainor6 p-p Correlations on (  ,   ) local charge and momentum conservation PF SF SF – string fragments PF – parton fragments LS – like signUS – unlike sign  √  ref away-side parton fragmentation is independent of charge combination string fragmentation reflects local measure conservation HBT string parton HBT parton joint autocorrelation on two difference variables parton

Trainor7 p-p jets: 105, 225, 350, 625 GeVe-e jets: 14, 44, 91 GeV Single-particle Fragmentation – I  = ln(1/x p ) OPAL – 91 GeV TASSO – 14 GeV ln(p t ) conventional fragmentation functions on logarithmic variables e-e fragmentation functions on transverse rapidity y t – systematic variation described by single model function transverse rapidity y t x p =p t /E jet LEP PETRA e-e CDF PRD 68 (2003) OPAL PLB 247 (1990) 617 Biebel, Nason and Webber hep-ph/ sampling: not full data! LEP

Trainor8 Single-particle Fragmentation – II p = 2.9 q = , 44, 91 GeV e-e ~ independent of y t,max  n ch  and  peak values from Bethke hep-ex/ simple e-e systematics on transverse rapidity unidentified hadrons from unidentified partons A = 0.65 u peak slope = 0.41 mode u= mode: e-e  two-particle fragment distribution fit:  distribution

Trainor9 Two-particle Fragment Distributions US – same side STAR preliminary ytyt yt~yt~ y t,peak Q/  p ≡  ln(x p ) 1 10 Q/2 (GeV) an approach derived from fragmentation functions construct a surface representing frag- mentation functions vs parton momentum Q/2 parton momentum fragment rapidity symmetrize the surface to represent fragment-fragment correlations compare to data: general features agree; string fragments appear at small y t n ch one can sketch a two-particle minimum-bias fragment distribution starting with a surface from which fragmentation functions are conditional slices conditional: trigger particle data

Trainor10 Number Correlations on y t  y t peripheral central STAR preliminary evolution of fragment distribution with Au-Au centrality 200 GeV p-p  √  ref 200 GeV Au-Au R AA same-side - US

Trainor11 Jet Morphology Relative to Thrust z  p t1 p t2 jtjt jtjt x  jet thrust axis (parton momentum) p-p collision axis j t – transverse momentum relative to jet thrust axis jtjt jtjt y most-probable parton Q/2 at right is 1-2 GeV/c, comparable to the intrinsic parton k t parton k t hadron momenta  √  ref angular correlations

Trainor12 Symmetrized Angular Kinematics p out p t1,2,   independent random variables p t,2 p   remove the trigger/associated asymmetry p t,part   j t scaling (not generally valid) p t,1 asymmetric: symmetric: kinematic limit symmetrize: trigger, associated  particles 1, 2 J. Rak, J. Jia T. Trainor, J. Porter remove trigger-associated asymmetry

Trainor13 Symmetrize  | j t  |  and  | k t  |  p t (GeV/c) y t2 ytyt ytyt   SS autocorrelation (     ) ytyt y t1 same for STAR preliminary p t (GeV/c) y t2 ytyt ytyt ytyt y t1 ASSS   AS no small-angle approximation, similar fragment p t

Trainor14 Angular Correlation Measurements ytyt SS - same sideAS - away side SS AS jtjt jtjt ktkt    large same-side (  asymmetry STAR preliminary j t scaling

Trainor15 Fragment Asymmetry about Thrust two-particle fragmentation jtjt jtjt previously unexplored region! pQCD STAR preliminary evolution with Q 2 of soft jet angular asymmetry small Q 2 larger Q GeV p-p Small-Q 2 partons down to 1 GeV are detectable These softest jets are strongly elongated in the azimuth  direction in p-p collisions no trigger particle lohi lo y t cut space p t combinations determine Q 2 of parton interaction softest jets ever! big non-perturbative effects ytyt 1:1 aspect ratio

Trainor16 Interpretation  contact plane contact plane water drops v rel = 6 m/s   ptpt low-Q 2 fragmentation broadened in contact plane ( ,p t ), narrowed perpendicular to it (  ) z z hydrodynamics of parton collisions

Trainor17 Minijet Deformation on (  ) in Au-Au  p-p HI p-p HI peripheral central  centrality    130 GeV Au-Au widths minbias p-p low Q 2 fragmentation asymmetry reverses – p-p  Au-Au 130 GeV Au-Au mid-central p-p Au-Au low Q 2

Trainor18 The Other k t Broadening azimuth broadening p t,part,1 p t,part,2 k ty,1 + k ty,2 p t,part,1 p t,part,2 largest k t effects: small q/2, q/2 -q/2 US  y t2 y t1 ytyt ytyt STAR preliminary interaction between intrinsic k t and momentum transfer q p t broadening the alignment between parton k t s and q determines whether relative azimuth or relative p t of fragments will broaden condition on (y t1,y t2 ) biases away-side azimuth broadening SS - intrajet AS - interjet  √  ref

Trainor19  p t  Fluctuations and p t Correlations   70-80% 20-30% 0-5% full STAR acceptance variance excess fluctuation scaling fluctuation inversion subtract multipoles autocorrelation STAR preliminary centrality  p t  fluctuations partons and velocity correlations: how is p t distributed on (  )?  p t  fluctuations invertible to p t autocorrelations  √  ref T. A. Trainor, R. J. Porter and D. J Prindle, J. Phys. G: Nucl. Part. Phys. 31 (2005) ; hep-ph/

Trainor20 Compare with p-p p t Autocorrelations Hijing Au-Au 200 GeV p-p 200 GeV minbias data Au-Au 200 GeV p-p 200 GeV n ch > 9 CI=LS+US CD=LS–US direct – from pair counting from fluctuation inversion 70-80% STAR preliminary  √  ref net-charge correlations

Trainor21 Model Fits 20-30% data  fit peak fit residuals fitdata fit peak red shifts and blue shifts 0-10% 70-80% quench off quench on Hijing collision centrality hijing B1B1 B3B3 B2B2 Hijing does not predict strong  broadening or negative structure peak amplitudespeak widths negative structure is unanticipated – what is the origin?

Trainor22  red shift low-x partons parton fragments Au-Au p t autocorrelation STAR preliminary p-p p t autocorrelation Au-Au 200 GeV bulk medium Response of medium to minimum-bias parton stopping Momentum transfer to medium Velocity structure of medium Medium recoil observed via same-side p t correlations red shift: particle production may be from a recoiling source Recoil Response to Parton Stopping 20-30% data  model peak recoil fit residuals fit data model peak STAR preliminary 80-90% ~ p-p 20-30% 0-5% 40-50%

Trainor23 Energy Dependence: SPS  RHIC CERES NPA 727 (2003) 97 dramatic increase of  p t  fluctuations with increasing  s NN STAR preliminary CERES STAR Hijing full acceptance centrality STAR string structure in Hijing does not appear in Au-Au data !

Trainor24 Summary Precision survey of p-p correlation structure Model-independent access to low-Q 2 partons Hydrodynamic aspects of parton scattering? The other k t broadening: p t asymmetry Low-Q 2 partons as Brownian probes of A-A Dissipation: p-p fragment distributions modified in A-A Non-pQCD p-p angular correlations modified in A-A p t correlations: temperature/velocity structure of A-A Strong disagreement with pQCD Hijing Monte Carlo Recoil response of A-A bulk medium: viscosity  0