Is the QGP at RHIC Non Perturbative?

Is the QGP at RHIC Non Perturbative? Perspectives from Hydrodynamics and Heavy Quark energy loss Azfar Adil Columbia University Yale-Columbia Fest ‘07

Reasons QGP might be Non Perturbative • Hydrodynamics • Models with ideal hydrodynamics in the QGP stage “work” at RHIC • Implied viscosity to entropy ratio (work by Teaney) is small ~ 0.2 • Perturbative QCD calculations of this ratio get nowhere close but calculations based on AdS/CFT methods in the strongly coupled Field Theory limit do • Heavy Quark Energy Loss • Perturbative radiative energy loss using reasonable parameter sets does not get close • Some claim this is because certain physical parameters are non perturbatively large (AdS/CFT? See WH) Yale-Columbia Fest '07

Is this it for pQCD? Yale-Columbia Fest '07

Hirano, nucl-th/0410017 PHOBOS, PRC 72, 051901 It’s the Hydro… !! Kolb & Heinz !! Yale-Columbia Fest '07

Hirano et al. Nucl-th/0511046 !! Need high viscosity with CGC !!!! PHOBOS, PRL 88, No 20 Adil et al. arXiv:nucl-th/0605012 Hirano et al. Nucl-th/0511046 … or is it ??? Statement should be… Assuming Part initial state, data is consistent with ideal hydrodynamics in QGP stage Yale-Columbia Fest '07

Not weird, just eccentric… Why is the CGC so weird??? More eccentric bulk naturally leads to higher elliptic flow Yale-Columbia Fest '07

The Upshot • We might not need ideal hydro in the QGP stage: • A CGC initial state needs more viscosity to explain data • Need independent way to tie down initial state • Then we can determine whether ideal hydro is needed • We propose as a probe… Yale-Columbia Fest '07

Jet Tomography - Now in 3D • The two kinds of initial bulk matter we need to differentiate are CGC type and NPart type. • They have similar gross properties but different Local densities Part(xT,y;b) and CGC(xT,y;b) • We propose detailed Jet Tomography RAA(pT,y,) in order to probe the initial state • The differences in bulk eccentricities should give different high pT v2. • The long range bulk correlations over rapidity y, will help us differentiate the initial states Yale-Columbia Fest '07

xT Local Rapidity Triangle Figure from BGK 1977. • Get rapidity dependent local participant density with BGK • Note global multiplicity is boost invariant for A = B but not local density • Binary un-twisted Yale-Columbia Fest '07

How to use Tomography xT • Different rapidity regions effected by different initial nuclei (as seen from BGK model) • Asymmetry apparent in Participant density (rotation around y-axis) • Binary density unaffected (symmetric) • Asymmetry can be probed via jet quenching • Long range rapidity anti correlations can be recorded. • Note : The RAA v1 as a function of pT,  and y is a good probe. Yale-Columbia Fest '07

The fishy CGC Dashed Lines Positive Rapidity Solid Lines Negative Rapidity CGC • Figures show <x> in fm as function of pT and y • CGC affects the high pT part as well (unlike BGK), generates “fish diagrams”. Yale-Columbia Fest '07

RAA > 0 RAA > 0 RAA < 0 RAA < 0 Opposite Tomographic Twist xT • Use v1(pT,y) to probe higher twist for higher pT • v1(pT,y) changes sign both as a function of pT and y Yale-Columbia Fest '07

Nuclear Modification Factor • Nuclear Modification Factor is used to track nuclear effects • Calculated using model similar to Drees, Feng, Jia. •  ~ 0.06 Yale-Columbia Fest '07

V1(pT,y) Calculations • CGC generally gives smaller v1 values than participant density • For monojets, there is a finite rapidity at which the v1 flips sign; lower rapidity for higher pT • Sensitive to nuclear edge effects • Sensitive to high ‘x’ assumptions Yale-Columbia Fest '07

V1(pT,y) Calculations cont’d… • Can extrapolate energies and nuclei to LHC (5500 GeV and Lb-Lb) • All parameters fit at RHIC, prediction of multiplicity from CGC/KLN • Multiplicity dN/dy(y=0, b=0) ~ 2300. Previous prediction in range ~ 1900-2500 • Counteracting effects of higher multiplicity and lower gradients give small energy dependence of effect. Yale-Columbia Fest '07

What about Heavy Quarks?? Yale-Columbia Fest '07

arXiv:hep-ph/0601107 Non Perturbative??? This is one way of going about the problem… Ramp up the parameter as much as you can… and worry about it later Note… qhat = 14 GeV2/fm is a pure parameter, with no perturbative explanation Can also do this with GLV, it’s just that they don’t… Yale-Columbia Fest '07

Yale-Columbia Fest '07

Conclusions • (s?)QGP at RHIC not yet “perfect” • Uncertainty in initial state needs to be resolved • Early thermalization a problem • Even if the current model is good, we need fully viscous hydro to test sensitivity • There are many perturbative avenues left for jet quenching • Collisional vs. radiative. (WHDG) • Correct geometry and fluctuations • In medium fragmentation for heavies • Point of theory is to test fundamental processes not “fit data”… avoid ramping up parameters • One should find possible missing effects before trying to interpret parameters • Still some work left with no strings attached Yale-Columbia Fest '07

Acknowledgments I would like to thank the following people for valuable discussions B. Cole, M. Gyulassy, W. Horowitz, D. Molnar, I. Vitev, S. Wicks Thanks to RHIG at Yale for hosting Yale-Columbia fest Yale-Columbia Fest '07

Model for Part Yale-Columbia Fest '07

CGC Distribution • Use kT factorization formula, with unintegrated gluon distributions • Unintegrated distributions depend on QSAT (KLN Model) • QSAT determined using participant density (not explicitly factorized!!! See, Drescher & Nara (2006)) • Free parameters are normalizations of xG and dNg/dy • Set to make dNg/dy ~ 1000 at midrapidity, b =0 • Set to make Q2S,A/B ~ 2 GeV2 at midrapidity, b =0 Yale-Columbia Fest '07

RAA for RHIC and LHC Yale-Columbia Fest '07

Measurements of v2 at y = 0 probably not enoughLets extend our reach and go off midrapidity Yale-Columbia Fest '07

Is the QGP at RHIC Non Perturbative?