aa versus pp (& da): a puzzling scaling in hbt@rhic

AA versus pp (& dA):A puzzling scaling in HBT@RHICZbigniew Chajcki1, Tom Gutierrez2, Mike Lisa1, Mercedes Lpez-Noriega11 Ohio State University2 U.C. Davis, LBL

lisa - XXI Winter Workshop - Breckenridge CO

OutlineIndispensability of spacetime in RHI studiesFemtoscopy in RHI collisions (rhic)Rationality of systematics [important reminder]The puzzle [refresher of one aspect]Focus on mT (T) systematicUnderlying physics in AA: dynamically-driven geometric substructureDo we understand AA relative to pp (and dA)?If not, what is the matter?!

Not-really-a-conclusion


Spacetime - an annoying bump on the road to Stockholm?Non-trivial space-time - the hallmark of rhicInitial state: dominates further dynamicsIntermediate state: impt element in exciting signalsFinal state:Geometric structural scale is THE defining feature of QGP


Hanbury Brown-Twiss interferometryTwo-particle interferometry: p-space separation space-time separation


Hanbury Brown-Twiss interferometryqoutqsideqlongTwo-particle interferometry: p-space separation space-time separation


Spacetime - an annoying bump on the road to Stockholm?Non-trivial space-time - the hallmark of rhicInitial state: dominates further dynamicsIntermediate state: impt (neglected?) element in exciting signalsFinal state:Geometric structural scale is THE defining feature of QGPTemporal scale sensitive to deconfinement transition (?)


Systematic decadencePion HBT @ Bevalac: largely confirming nuclear dimensionsSince 90s: increasingly detailed understanding and study w/ high statsR = 5 fm


Systematic decadencePion HBT @ Bevalac: largely confirming nuclear dimensionsSince 90s: increasingly detailed understanding and study w/ high stats


Does HBT in rhic make sense?YESSize [R(Npart1/3)]Shape [R( )]STAR, PRL93 012301 (2004)


Does HBT in rhic make sense?YESSize [R(Npart1/3)]Shape [R( )]Dynamic substructure [R(mT)]


Why do the radii fallwith increasing momentum ??


Kolb & Heinz, QGP3 nucl-th/0305084Decreasing R(pT)usually attributed to collective flowflow integral to our understanding of R.H.I.C.; taken for grantedfemtoscopy the only way to confirm x-p correlations impt check


Decreasing R(pT)usually attributed to collective flowflow integral to our understanding of R.H.I.C.; taken for grantedfemtoscopy the only way to confirm x-p correlations impt check

Non-flow possibilitiescooling, thermally (not collectively) expanding sourcecombo of x-t and t-p correlations

early times: small, hot sourcelate times: large, cool source




MAL et al, PRC49 2788 (1994)1500 fm/c (!)




hot core surrounded by cool shellimportant ingredient of Buda-Lund hydro picture e.g. Csrg & Lrstad PRC54 1390 (1996)




hot core surrounded by cool shellimportant ingredient of Buda-Lund hydro picture e.g. Csrg & Lrstad PRC54 1390 (1996)tEach scenario generatesx-p correlationsbutx2-p correlation:yesx-p correlation:yesx2-p correlation:yesx-p correlation:nox2-p correlation:yesx-p correlation:no


flow-dominated models can reproduce soft-sector x-space observablesimply short timescales

however, are we on the right track? [flow]puzzles? check your assumptions!look for flows special signature x-p correlation

In flow pictures, low-pT particles emitted closer to sources center (along out)non-identical particle correlations (FSI at low v) probe:(x1-x2)2 (as does HBT)x1-x2 Csand, Csrg, Lrstad nucl-th/0311102 and nucl-th/0310040[click for more details on non-id correlations]F. Retiere & MAL, Phys. Rev. C70 044907 (2004)Kp


In flow pictures, low-pT particles emitted closer to sources center (along out)non-identical particle correlations (FSI at low v) probe:(x1-x2)2 (as does HBT)x1-x2 extracted shift in emission point x1-x2 consistent w/ flow-dominated blastwave


Does HBT in rhic make sense?YESSize [R(Npart1/3)]Shape [R( )]Dynamic structure [R(mT)]



and NOModel disagreement [transport]



and NOModel disagreement [transport]Too-short timescales [BW]F. Retiere & MAL, Phys. Rev. C70 044907 (2004)F. Reiere, QM04 nucl-ex/0405024



and NOModel disagreement [transport]Too-short timescales [BW]BW fits: flow velocity max() at edge at freezeout

Surely R(,t=) < R(,t=0) + max()* STAR nucl-ex/0411036 [subm PRC]



and NOModel disagreement [transport]Too-short timescales [BW]Inconsistent dynamical pictureSTAR nucl-ex/0411036 [subm PRC]



and NOModel disagreement [transport]Too-short timescales [BW]Inconsistent dynamical pictureNo large rise in RO, RL [general]


Does HBT in rhic make sense? YES?Size [R(Npart1/3)]Shape [R( )]Dynamic structure [R(mT)]

and NOModel disagreement [transport]Too-short timescales [BW]Inconsistent dynamical pictureNo large rise in RO, RL [general]Simultaneously reasonable?


latest puzzle in HBT?

HBT radii from pp fall with pT (as observed previously, usually attributed to string kT kick)

but as much (proportionally) as dAu and AuAu ??coincidence?something deeper?STAR, QM04transverse plane


latest puzzle in HBT?

HBT radii from pp fall with pT (as observed previously, usually attributed to string kT kick)

but as much (proportionally) as dAu and AuAu ??coincidence?something deeper?

What it does NOT mean:AA=N*(strings)AA=N*(little blastwaves)

AA: global x-p correlations


Focus on RLONGSinyukov: Boost-invariant:

(+ flow effects)



(+ flow effects)Au+Au - reasonableBut* hydro alone : 0~15 fm/c* Heinz & Kolb, hep-ph/0204061STAR nucl-ex/0411036 [subm PRC]



(+ flow effects)Au+Au - reasonableBut* hydro alone : 0~15 fm/c

In p+p (e+e): often understood via Heisenberg

Identical experimental behaviorVERY different physics ! (right?)* Heinz & Kolb, hep-ph/0204061G. Alexanderhep-ph/0108194Hadronic Z0 decays~ 1 fm/c


Geometrical RSAA understood (?) in terms of collective flowSpooky that pp ~ AA/5But pp, dAu apparent global x-p correlations, but no expansion?p+p fair comparison?F. Retiere, QM04


Bummerpp = little AA physics-wise ?hey, why not? (Csorgo)different driving physics just looks the same ? [coincidence]resonances (Wiedemann, Schlei,)uncertainty principle morphs (weirdly) into thermal/collective scenario?kicks in string-breaking dynamicsHBT just doesnt measure geometry/dynamics anywaybecause it doesnt work (Gyulassy, based on convenience)source HBT not so simple (Kapusta, Wong,Cramer)it cannot be that wrong (Lisa, based on systematics)

It it our oversimplified Gaussian radii?


Worst-case picture of d-Au [prelim]Not great fitOne imagines one could do a better job, but fit must work in 3D; we see tiny portion of spaceWhat is going on in the normalization region? (indep of Gaussian ansatz)ad hoc fixes dangerous!

Problem with projectionscannot see systematics in 3Dexperiments w/same CF will have different projectionsSTAR Preliminary


Whole CF at a glanceCartesian-space (out-side-long) naturally encodes physics, but is poor/inefficient representationRecognize symmetries of Q-space -- decompose by spherical harmonics!

Direct connection to source shapes [Danielewicz,Pratt]~immune to acceptancefull information content at a glance [thanx to symmetries]


L=0L=2L=4M=0M=2M=4Simple, Gaussiansource calculationsRL < RTRL > RTRO < RSRO > RSRinvBut better!!~acceptance free!


L=0L=2L=4M=0M=2M=4Gaussian source fit(Coulomb in fit)d+Au kT-integrated

RO = 1.74 fmRS = 1.69 fmRL = 2.14 fm= 0.36

dataSTAR Preliminary


Mikes shortest summary ever(lets discuss)Along most axes, HBT systematics make senseits the geometry, stupid & geometry defines R.H.I.C.so, take puzzles seriouslyrecent puzzle: pp/dA/AA HBT versus mT too similartimescales from RL? Heisenberg or Boost-invariant thermal bulk?dynamically-induced RS(mT)? pp = little AA?is lack of expansion in pp comforting? Is pp valid reference?insensitivity of HBT to different underlying physics?

fitting artifact? Ylm decomp (+ imaging) promising & underwayIMHO* : issues with data but they are not the root cause (also Gaussian is not at root)* IMHO = In Mikes Humble Opinion


Is this what weve come (back) to?


The end


Well, if not puzzling, then at least disturbing

We all know there is a problem with HBT. My goal is to emphasize another (related??) problem which, if it can be addressed seriously by the theorists (yet to happen), might shed insight.1st bullet: The amazing proclivity of some to ignore HBT as an annoying distraction is unscientific and misguided

2nd bullet: yes, we all know there is HBT puzzle. But lets keep in mind its context and that not ALL systematics are puzzling

iSpace-time more important to rhic than to any other accelerator-based physics

Unlike Jlab or so, where beam energy dictates scale probed, the main goal of rhic is to find QGP, in which FUNDAMENTAL physics sets the scale

Evolution: system GROWS and changes SHAPE

FINAL STATE PROBED BY HBT (NEXT)Space-time more important to rhic than to any other accelerator-based physics

Unlike Jlab or so, where beam energy dictates scale probed, the main goal of rhic is to find QGP, in which FUNDAMENTAL physics sets the scale

Evolution: system GROWS and changes SHAPEWell, some folks would say that since it has generated little insight (grrr.), spending so muchEffort on HBT has indeed been decadent

BTW, *I* do not claim that Bevalac (and MSU for that matter) was trivial, but its been stated that wayWell, some folks would say that since it has generated little insight (grrr.), spending so muchEffort on HBT has indeed been decadent

BTW, *I* do not claim that Bevalac (and MSU for that matter) was trivial, but its been stated that wayNeed to ask this question (does it make sense) and be reminded that YES-- HBT certainly IS probing geometry

On the tepid root(s) dependence: even FORGETTING models, expect some change in geometry due to QGP or at least to changing physics with hugely different energy!

Hard to build consistent picture -- I.e. THEORISTS-- DONT GIVE UP!Need to ask this question (does it make sense) and be reminded that YES-- HBT certainly IS probing geometry

On the tepid root(s) dependence: even FORGETTING models, expect some change in geometry due to QGP or at least to changing physics with hugely different energy!

Hard to build consistent picture -- I.e. THEORISTS-- DONT GIVE UP!We noticed this on the asHBT slide[This is an internal CAT SCAN of geometric substructure.]consequencesNOT BAD!

Hey, you know, this is not trivial. WE ARE MEASURING DETAILS OF GEOMETRY! Dont forget it!

But the riddler doesnt like it because its not a riddle!Heinz and Kolb: An oldie but a goodie (Still reflects models versus data today)We all know this ad infinitum, and its not the point of my talk, so I move on now. (But cant give this talk without showing one such plot!)Heinz and Kolb: An oldie but a goodie (Still reflects models versus data today)We all know this ad infinitum, and its not the point of my talk, so I move on now. (But cant give this talk without showing one such plot!)OK, so maybe this means that HBT has some kind of internal scaling factor-- I.e. all the radii are off by 1.5, either experimentally or theoretically.Despite our best efforts, this could be true, and has been claimed.

Even so, the next thing, which is root(s) dependence, is still puzzling, since we expect on quite general grounds (I.e. without reference to a particularscale) a jump in HBT radii when physics changesSo, from the specific (hydro, transport) to the very general,There seems to be a puzzle.

But hey, at least we understand the dynamic substructure, right?Well, lets revisit what we think makes sense

Although Im known to focus on shape, I wanna go back to Npart and mT dependence SIMULTANEOUSLY (individually they seemed to make sense)So, from the specific (hydro, transport) to the very general,There seems to be a puzzle.

But hey, at least we understand the dynamic substructure, right?Well, lets revisit what we think makes sense

Although Im known to focus on shape, I wanna go back to Npart and mT dependence SIMULTANEOUSLY (individually they seemed to make sense)AA is not N*pp

Its more like pp is a little AA!Interesting that they both involve timescale, but they ARE different!

One has hbar, the other not.So pp LOOKS like flow by itself

But there is no expansion, so its probably not flow(or no time, but then how does flow develop?!)

Should I feel better??IS pp like AA? Hey, that would not be the firsttime that (in soft sector) our reference is a lotlike the system under study(e.g. chemical & kinetic temperatures, Dimas born thermaletc)

Each of these, I would call a bummer.

aa versus pp (& da): a puzzling scaling in hbt@rhic

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