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Systematics of high-pT hadron spectra

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1 Systematics of high-pT hadron spectra
Julia Velkovska

2 Most-cited paper from RHIC:
What can we learn from the systematics of high pT single particle measurements ? pT GeV/c intermediate Intermediate pT High-pT This talk Most-cited paper from RHIC: “Suppression of hadrons with large transverse momentum in central Au+Au collisions at √sNN= 130 GeV ”, K. Adcox et al. , Phys.Rev.Lett. 88: (2002), nucl-ex/ Nov 16,2006 J.Velkovska

3 h+/-, p0 , p+/-, h, w, p, K0s ,L, e(from c & b)
RHIC data sets p+p d+Au Au+Au Cu+Cu T A L K F L O W 22.4 GeV 62.4 GeV 130 GeV 200 GeV Reference sQGP ? h+/-, p0 , p+/-, h, w, p, K0s ,L, e(from c & b) Nov 16,2006 J.Velkovska

4 Outline Using different QCD probes at high pT Production in pp
How well do we know the FFs ? Production in d+Au Do we understand initial state effects ? 200 GeV Au+Au Are all probes the same ? Test: dE/dxg ~ 0 dE/dxQ < dE/dxq < dE/dxg ? Can we use RAA to constrain theoretical models ? Sustem size comparison (Cu+Cu) Energy dependence: What changes and why ? Conclusions Nov 16,2006 J.Velkovska

5 High pT Particle Production in pp
Fragmentation Function hadrons leading particle Jet: A localized collection of hadrons which come from a fragmenting parton c a Hard-scattering cross-section Parton Distribution Functions Parton Distribution Functions Hard-scattering cross-section Fragmentation Function b d “Collinear factorization” Nov 16,2006 J.Velkovska

6 High pT Particle Production in A+A
(pQCD context…) Parton Distribution Functions Intrinsic kT , Cronin Effect Shadowing, EMC Effect Fragmentation Function leading particle suppressed c d hadrons a b Hard-scattering cross-section Partonic Energy Loss Nov 16,2006 J.Velkovska

7 pp reference @ 200 GeV vs pQCD
poster by A. Bazilevsky A closer look at pions Compilation by D. d’Enterria nucl-ex/ Good agreement with theory Nov 16,2006 J.Velkovska

8 Strange hadrons in pp @ 200 GeV
Poster A.Milov The same FFs that describe the pions do not work so well for strange particles FFs based on Opal e+e- flavor tagged data (AKK) in agreement with RHIC pp data Measured pp reference is essential for understanding AA Nov 16,2006 J.Velkovska

9 Non-photonic electrons in pp
hep-ex/ Accepted by PRL Theoretical Uncertainty Band Ratio: 1.72 +/-0.02 (stat) +/ (sys) (0.3 < pT < 9.0 GeV/c) ~factor 2 D0 CDF, PRL 91, (2003) For heavy quarks, the agreement with FONLL marginal (at the edge of the error band) Nov 16,2006 J.Velkovska

10 Extending the systematics to w
To be submitted to PRL on Nov 18 Talk by Y.Riabov : session 3.1 First world measurement of w in pp and dAu collisions Nov 16,2006 J.Velkovska

11 d+Au collisions @ 200 GeV p0 h/p0
Star: nucl-ex/ p0 Phenix:nucl-ex/ h/p0 Baryon/meson difference at intermediate pT (cent dependent) Mesons: no strong initial state effects Universal behavior at high pT Nov 16,2006 J.Velkovska

12 RAA in AuAu collisions @ 200 GeV
p 0 h Talks: T. Isobe: 3.3 B. Salhmueller: 3.2 Medium transparent to direct photons (except maybe at the highest pT –expected for fragmentation g) Completely opaque out to 20 GeV/c for light hadrons ! Eloss at partonic level (before fragmentation and hadronization) – challenge for models with pre-hadron absorption in the medium Nov 16,2006 J.Velkovska

13 Inclusive charged hadrons @ 200 GeV
Au+Au Inclusive charged hadrons equally absorbed at high pT Can we find a probe that has a different suppression pattern ? Nov 16,2006 J.Velkovska

14 Can we distinguish gluon from quark energy loss ?
STAR : PRL 97, (2006) Talk 2.2 B. Mohanty Protons are expected to have larger contribution from gluons compared to pions => larger energy loss But above pT ~ 6 GeV/c – same suppression pattern ! Nov 16,2006 J.Velkovska

15 HQ Energy Loss and Flow nucl-ex/0611018
(submitted to Phys. Rev. Lett.) Heavy quarks are expected to loose less energy than light quarks, but at ~ 6 GeV/c – equally suppressed as pions Radiative energy loss only fails to reproduce v2HF. Heavy quark transport model has reasonable agreement with both RAA and v2HF. Small relaxation time t or diffusion coefficient DHQ inferred for charm. Heavy flavor RAA consistent with energy loss q_hat = 14 GeV^2/fm (as for light quarks) but does not reproduce v2 (purely geometrical). Heavy quark transport calculations – with elastic scattering and resonance excitation – do a fair job on both. Third curve, parameters calculated in model using diffusion coefficient (can’t et both sets of data with the same value). Emphasize the power of using multiple measurements to constrain models – a necessary evolution of sophistication at RHIC! Talk: F. Kajihara (2.1.07) Nov 16,2006 J.Velkovska

16 What Can We Learn From RAA?
C. Loizides hep-ph/ v2 Ivan Vitev William Horowitz Nov 16,2006 J.Velkovska

17 Comparing p0 RAA to theory
Add stat and uncorr point-to-point syst err in quadrature – c2 minimization fit to obtain the probability of a given parameter Then offset the data points by +/- 1 RMS of the correlated syst errors and do the same Sum up 1 & 2 to obtain the curves above Little sensitivity to model parameters Nov 16,2006 J.Velkovska

18 RAA vs reaction plane: more information ?
nucl-ex/ (submitted to Phys. Rev. C.) Out of Plane 0-10% 50-60% In Plane Le Le = matter thickness calculated in Glauber model Little/no energy loss for Le < 2 fm Poster: D. Winter Talk: V. Pantuev (2.2.05) Nov 16,2006 J.Velkovska

19 RAA – Reaction systems p 0 Au+Au Cu+Cu Au+Au 30-40 %, NPart = 114.2
200 GeV Au+Au Cu+Cu Au+Au %, NPart = 114.2 Cu+Cu 0-10 %, NPart = 98.2 Similar suppression at similar Npart Systematic comparison possible Advantage of smaller system: less uncertainty in Glauber model calculations for peripheral collisions Nov 16,2006 J.Velkovska

20 Integrated RAA vs Npart system comparison
Steeper slope at low Npart in CuCu Geometrical model with “corona”: describes v2 and RAA Nov 16,2006 J.Velkovska

21 RAA – Energy dependence
Vitev nucl-th/ Au+Au Cu+Cu dNg/dy= p 0 Vitev nucl-th/ 62 GeV 22.4 GeV Supression (and dNg/dy) decreases as we go down in energy – consistent with SPS data Nov 16,2006 J.Velkovska

22 WA98 √s = 17.3 GeV : RAA -> PbPb/pPb Tab
0-12.7% central PRELIMINARY p 0 Interesting way to subtract initial state effect shown at this conference Suppresion observed with p+Pb reference Nov 16,2006 J.Velkovska

23 Energy dependence of Eloss Summary and model comparison
nucl-ex/ Data is better described by Non-Abelian energy loss

24 Conclusions In pp collisions:
pQCD works (better for light quarks than for heavy quarks) Measurements of reference spectra in pp is essential In dAu collisions at 200 GeV No strong initial state effects: RdA ~ 1 Uniform behavior for different hadrons at high pT In AA collsions Hadron suppression at high pT , flat out to 20 GeV/c evolving with c.m. energy Photons are not suppressed dE/dxg ~ 0 But, dE/dxQ < dE/dxq < dE/dxg – doesn’t seem to hold. Additional collisional energy loss maybe needed to describe the data Little sensitivity to model parameters from RAA alone RAA depends on the pathlength in the medium Nov 16,2006 J.Velkovska

25 Nov 16,2006 J.Velkovska

26 p0 and h nucl-ex/0601037 Au+Au d+Au p+p
Similar suppression pattern p0 and h h/p0 ~ in all systems and for all centralities Universal suppression for light mesons Suppression at partonic level before fragmentation !(?) Nov 16,2006 J.Velkovska

27 Energy comparison of p and pi
Similar Eloss of partons STAR : PRL 97, (2006) Nov 16,2006 J.Velkovska

28 In plane emission shows no energy loss in peripheral bins.
RAA vs. Reaction Plane Au+Au collisions at 200GeV nucl-ex/ (submitted to Phys. Rev. C.) Out of Plane In Plane Le In plane emission shows no energy loss in peripheral bins. 3<pT<5 GeV/c Nov 16,2006 J.Velkovska

29 RAA Le Dependence nucl-ex/0611007 Au+Au collisions at 200GeV
(submitted to Phys. Rev. C.) Au+Au collisions at 200GeV 50-60% The pathlength weighted integral over the density is done on a Glauber model by assuming that the density goes like the Ncoll density. The data seem to imply that we don’t reach a regime that matches the energy dependence of purely radiative energy loss until high pT. Is this a signal that at lower pT’s collisional losses are significant? This is all in pretty good agreement with Magdelena’s calculations (see backup slide). 0-10% Le = matter thickness calculated in Glauber model Poster: D. Winter Talk: V. Pantuev (2.2.05) Little/no energy loss for Le < 2 fm Nov 16,2006 J.Velkovska

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