features similar to above signal: correlations are broader and not as strong

1. 5.0 4.0 3.0 2.0 1.0 0.5 near-side (small-angle) peak structure Soft and Semi-hard Components in p-p Collisions at sNN= 200 GeV R. Jeff Porter, Brookhaven National Laboratory & University of Washington (STAR Collaboration) Abstract: transverse rapidity two-particle correlations yt,1 x yt,2 correlations (STAR Preliminary data) pt (GeV/c) evaluated from same event pairs To examine correlation structure at larger pt, we change variables to transverse rapidity yt. This variable compresses data at larger pt and reduces density variation on the transverse momentum variable. evaluated from sibling (mixed-event) pairs where semi-hard-component autocorrelations Correlations on yt x yt provide a transparent cut space on which one can separate correlations due to soft-string fragmentations from hard scattering jet-like features: small-angle peak plus broad hD-independent peak on fD at fD~p Correlations from semi-hard scattering emerge above pt ~ 0.5GeV/c Autocorrelations on fD,hD at moderate pt have features in common with those found with “jet-finding” selections 2-particle correlations are part of a continuum: jets, jet-remnants and mini-jets In this analysis we forgo reliance on trigger-particle selections and map out these correlations over the entire pt range. “jet-finding” selection: e.g., trigger particle pt > 4GeV/c soft-component autocorrelations Histogram Key LS=Like-sign pairs US=Unlike-sign pairs CD=LS – US CI=LS + US STAR Preliminary data g-conversion to e+e-pairs Low-yt structure: local charge conservation near hD ~ 0 for US pairs LS pairs have a strong small-angle peak consistent with HBT Results from Pythia show no HBT signal but do reveal a charge conservation structure similar to data 0.8<pt1,pt2<2.3 GeV/c features similar to above signal: correlations are broader and not as strong HBT local charge conservation about hD ~ 0 Summary • - Two-particle correlations on yt x yt (and Nch) • provide a transparent cut space to study soft • and semi-hard scattering components • Low-pt correlations reveal local charge • conservation and HBT signals • At higher pt (> 0.5 GeV/c), structures asso- • ciated with jet correlations show a continuum • of features resulting from semi-hard scattering • These p-p minijet correlation studies provide • an essential reference for A-A collisions model function description Pythia 6.2 Minbias No HBT charge conservation broader than data away-side structure about f~p small charge-dependent band about h~0 STAR Preliminary data model fit correlation dependence on Nch Autocorrelations reveal simple structures easily modeled by standard functions. Correlations at moderate pt are well fit by gaussians and share features (near-side peak or “jet-cone”) with those obtained from Pythia. Data structures are sharper and more eccentric than Pythia but converge with Pythia at pair pt ~ 6 GeV/c. The integrated correlation strengths from Pythia grow with total pt while those for data remain flat up to pt ~ 6 GeV/c. Signal pushes out to larger ytxyt with increasing Nch while correlation strength at moderate yt grows.