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AA versus pp (& dA): A puzzling scaling in HBT@RHIC

AA versus pp (& dA): A puzzling scaling in HBT@RHIC. Zbigniew Chaj ę cki 1 , Tom Gutierrez 2 , Mike Lisa 1 , Mercedes López-Noriega 1 1 Ohio State University 2 U.C. Davis, LBL. Outline. Indispensability of spacetime in RHI studies Femtoscopy in RHI collisions ( rhic )

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AA versus pp (& dA): A puzzling scaling in HBT@RHIC

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  1. AA versus pp (& dA):A puzzling scaling in HBT@RHIC Zbigniew Chajęcki1, Tom Gutierrez2, Mike Lisa1, Mercedes López-Noriega1 1 Ohio State University 2 U.C. Davis, LBL lisa - XXI Winter Workshop - Breckenridge CO

  2. Outline • Indispensability of spacetime in RHI studies • Femtoscopy in RHI collisions (rhic) • Rationality of systematics [important reminder] • The “puzzle” [refresher of one aspect] • Focus on mT (T) systematic • Underlying physics in AA: dynamically-driven geometric substructure • Do we understand AA relative to pp (and dA)? • If not, what is the matter?! • Not-really-a-conclusion lisa - XXI Winter Workshop - Breckenridge CO

  3. Spacetime - an annoying bump on the road to Stockholm? STAR, PRC66 (2002) 034904 STAR, PRL93 (2004) 252301 • Non-trivial space-time - the hallmark of rhic • Initial state: dominates further dynamics • Intermediate state: impt element in exciting signals • Final state: • Geometric structural scale is THE defining feature of QGP lisa - XXI Winter Workshop - Breckenridge CO

  4. Hanbury Brown-Twiss interferometry Rlong p1 x1 p2 qside Rside x2 qout qlong Rout • HBT: Quantum interference between identical particles 2 C (q) Gaussian model (3-d): 1 • Final-state effects (Coulomb, strong) also can cause correlations, need to be accounted for q (GeV/c) • Two-particle interferometry: p-space separation  space-time separation lisa - XXI Winter Workshop - Breckenridge CO

  5. Hanbury Brown-Twiss interferometry Rlong p1 x1 p2 Rside x2 Rout Rside Rout • Two-particle interferometry: p-space separation  space-time separation qside qout qlong lisa - XXI Winter Workshop - Breckenridge CO

  6. Spacetime - an annoying bump on the road to Stockholm? Ann.Rev.Nucl.Part.Sci. 46 (1996) 71 • Non-trivial space-time - the hallmark of rhic • Initial state: dominates further dynamics • Intermediate state: impt (neglected?) element in exciting signals • Final state: • Geometric structural scale is THE defining feature of QGP • Temporal scale sensitive to deconfinement transition (?) lisa - XXI Winter Workshop - Breckenridge CO

  7. Systematic decadence A.D. Chacon et al, Phys. Rev. C43 2670 (1991) G. Alexander, Rep. Prog. Phys. 66 481 (2003) AGS/SPS/RHIC HBT papers (expt) Heinz/Jacak Wiedemann/Heinz Csorgo 20 R = 1.2 (fm)•A1/3 Tomasik/Wiedemann Boal/Jennings/Gelbke 15 10 5 ‘85 ‘90 ‘95 ‘00 ‘05 “R = 5 fm” • Pion HBT @ Bevalac: “largely confirming nuclear dimensions” • Since 90’s: increasingly detailed understanding and study w/ high stats lisa - XXI Winter Workshop - Breckenridge CO

  8. Systematic decadence AGS/SPS/RHIC HBT papers (expt) Heinz/Jacak Wiedemann/Heinz Csorgo 20 Tomasik/Wiedemann Boal/Jennings/Gelbke 15 y 10 5 |b| ‘85 ‘90 ‘95 ‘00 ‘05 pT • Pion HBT @ Bevalac: “largely confirming nuclear dimensions” • Since 90’s: increasingly detailed understanding and study w/ high stats lisa - XXI Winter Workshop - Breckenridge CO

  9. Does HBT in rhic make sense? more central YES… • Size [R(Npart1/3)] • Shape [R( )] lisa - XXI Winter Workshop - Breckenridge CO STAR, PRL93 012301 (2004)

  10. Does HBT in rhic make sense? YES… • Size [R(Npart1/3)] • Shape [R( )] • Dynamic substructure[R(mT)] lisa - XXI Winter Workshop - Breckenridge CO

  11. Why do the radii fallwith increasing momentum ?? lisa - XXI Winter Workshop - Breckenridge CO

  12. Decreasing R(pT) • usually attributed to collective flow • flow integral to our understanding of R.H.I.C.; taken for granted • femtoscopy the only way to confirm x-p correlations – impt check Kolb & Heinz, QGP3 nucl-th/0305084 lisa - XXI Winter Workshop - Breckenridge CO

  13. Decreasing R(pT) • usually attributed to collective flow • flow integral to our understanding of R.H.I.C.; taken for granted • femtoscopy the only way to confirm x-p correlations – impt check • Non-flow possibilities • cooling, thermally (not collectively) expanding source • combo of x-t and t-p correlations early times: small, hot source late times: large, cool source lisa - XXI Winter Workshop - Breckenridge CO

  14. Decreasing R(pT) • usually attributed to collective flow • flow integral to our understanding of R.H.I.C.; taken for granted • femtoscopy the only way to confirm x-p correlations – impt check • Non-flow possibilities • cooling, thermally (not collectively) expanding source • combo of x-t and t-p correlations 1500 fm/c (!) MAL et al, PRC49 2788 (1994) lisa - XXI Winter Workshop - Breckenridge CO

  15. Decreasing R(pT) • usually attributed to collective flow • flow integral to our understanding of R.H.I.C.; taken for granted • femtoscopy the only way to confirm x-p correlations – impt check • Non-flow possibilities • cooling, thermally (not collectively) expanding source • combo of x-t and t-p correlations • hot core surrounded by cool shell • important ingredient of Buda-Lund hydro picturee.g. Csörgő & LörstadPRC54 1390 (1996) lisa - XXI Winter Workshop - Breckenridge CO

  16. Each scenario generates x-p correlations • Decreasing R(pT) • usually attributed to collective flow • flow integral to our understanding of R.H.I.C.; taken for granted • femtoscopy the only way to confirm x-p correlations – impt check but… x2-p correlation: yes x-p correlation: yes • Non-flow possibilities • cooling, thermally (not collectively) expanding source • combo of x-t and t-p correlations • hot core surrounded by cool shell • important ingredient of Buda-Lund hydro picturee.g. Csörgő & LörstadPRC54 1390 (1996) x2-p correlation: yes x-p correlation: no t x2-p correlation: yes x-p correlation: no lisa - XXI Winter Workshop - Breckenridge CO

  17. pT T • flow-dominated “models” can reproduce soft-sector x-space observables • imply short timescales • however, are we on the right track? [flow] • puzzles?  check your assumptions! • look for flow’s “special signature”x-p correlation • In flow pictures, low-pT particles emitted closer to source’s center (along “out”) • non-identical particle correlations(FSI at low v) probe: • (x1-x2)2 (as does HBT) • x1-x2  K p [click for more details on non-id correlations] lisa - XXI Winter Workshop - Breckenridge CO F. Retiere & MAL, Phys. Rev. C70 044907 (2004) Csanád, Csörgő, Lörstad nucl-th/0311102 and nucl-th/0310040

  18. T T x (fm) x (fm) A. Kisiel (STAR) QM04 • extracted shift in emission point x1-x2 consistent w/ flow-dominated blastwave • In flow pictures, low-pT particles emitted closer to source’s center (along “out”) • non-identical particle correlations(FSI at low v) probe: • (x1-x2)2 (as does HBT) • x1-x2 lisa - XXI Winter Workshop - Breckenridge CO

  19. Does HBT in rhic make sense? x (fm) A. Kisiel (STAR) QM04 x (fm) YES… • Size [R(Npart1/3)] • Shape [R( )] • Dynamic structure [R(mT)] lisa - XXI Winter Workshop - Breckenridge CO

  20. Does HBT in rhic make sense? Heinz & Kolb, WW18 hep-ph/0204061 YES… • Size [R(Npart1/3)] • Shape [R( )] • Dynamic structure [R(mT)] … and NO • Model disagreement [transport] lisa - XXI Winter Workshop - Breckenridge CO

  21. Does HBT in rhic make sense? T=106 MeV; <b> = 0.55; R = 12.5 fm Lifetime (t) = 8.4 ± 0.2 fm/c Emission duration () = 1.9 ± 0.2 fm/c YES… • Size [R(Npart1/3)] • Shape [R( )] • Dynamic structure [R(mT)] … and NO • Model disagreement [transport] • Too-short timescales [BW] F. Retiere & MAL, Phys. Rev. C70 044907 (2004) F. Reiere, QM04 nucl-ex/0405024 lisa - XXI Winter Workshop - Breckenridge CO

  22. Does HBT in rhic make sense? RX RY t = 0 “initial” t =  “final” T=106 MeV; <b> = 0.55; R = 12.5 fm Lifetime (t) = 8.4 ± 0.2 fm/c Emission duration () = 1.9 ± 0.2 fm/c YES… • Size [R(Npart1/3)] • Shape [R( )] • Dynamic structure [R(mT)] … and NO • Model disagreement [transport] • Too-short timescales [BW] • BW fits: flow velocity max() • at edge • at freezeout • Surely… • R(,t=) < R(,t=0) + max()*  lisa - XXI Winter Workshop - Breckenridge CO STAR nucl-ex/0411036 [subm PRC]

  23. Does HBT in rhic make sense? RX RY t = 0 “initial” t =  “final” YES… • Size [R(Npart1/3)] • Shape [R( )] • Dynamic structure [R(mT)] … and NO • Model disagreement [transport] • Too-short timescales [BW] • Inconsistent dynamical picture lisa - XXI Winter Workshop - Breckenridge CO STAR nucl-ex/0411036 [subm PRC]

  24. Does HBT in rhic make sense? YES… • Size [R(Npart1/3)] • Shape [R( )] • Dynamic structure [R(mT)] … and NO • Model disagreement [transport] • Too-short timescales [BW] • Inconsistent dynamical picture • No large rise in RO, RL[general] lisa - XXI Winter Workshop - Breckenridge CO

  25. Does HBT in rhic make sense? YES…? • Size [R(Npart1/3)] • Shape [R( )] • Dynamic structure [R(mT)] … and NO • Model disagreement [transport] • Too-short timescales [BW] • Inconsistent dynamical picture • No large rise in RO, RL [general] Simultaneously reasonable? lisa - XXI Winter Workshop - Breckenridge CO

  26. 2 p+p+X Rlong Rout / Rout(pp) Rside / Rside(pp) Rout 1 Rside p+pstring fragmentation Au+AuCollective expansion Rlong / Rlong(pp) 0.25 0.5 pT • 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, QM04 lisa - XXI Winter Workshop - Breckenridge CO transverse plane

  27. local x-p corr. NB: p-space observables identical in the two cases • 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 lisa - XXI Winter Workshop - Breckenridge CO

  28. local x-p corr. NB: p-space observables identical in the two cases • 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 lisa - XXI Winter Workshop - Breckenridge CO

  29. Focus on RLONG Rlong p1 x1 p2 Rside qside x2 qout Rout qlong • Sinyukov: Boost-invariant: (+ flow effects) lisa - XXI Winter Workshop - Breckenridge CO

  30. Focus on RLONG Nparticipants • Sinyukov: Boost-invariant: (+ flow effects) • Au+Au - reasonable • But* hydro alone : 0~15 fm/c lisa - XXI Winter Workshop - Breckenridge CO * Heinz & Kolb, hep-ph/0204061 STAR nucl-ex/0411036 [subm PRC]

  31. Focus on RLONG RZ (fm)  mT (GeV) R (fm) K  p, m (GeV) G. Alexander hep-ph/0108194 Hadronic Z0 decays • Sinyukov: Boost-invariant: (+ flow effects) • Au+Au - reasonable • But* hydro alone : 0~15 fm/c • In p+p (e+e): often understood via Heisenberg • Identical experimental behavior • VERY different physics ! (right?) ~ 1 fm/c lisa - XXI Winter Workshop - Breckenridge CO * Heinz & Kolb, hep-ph/0204061

  32. “Geometrical” RS RX RY t = 0 “initial” t =  “final” • AA “understood” (?) in terms of collective flow • “Spooky” that pp ~ AA/5 • But…pp, dAu apparent global x-p correlations, but no expansion? • p+p fair comparison? F. Retiere, QM04 lisa - XXI Winter Workshop - Breckenridge CO

  33. Bummer… • pp = “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 dynamics • HBT just doesn’t measure geometry/dynamics anyway • because it doesn’t 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? lisa - XXI Winter Workshop - Breckenridge CO

  34. Worst-case picture of d-Au [prelim] • Not great fit • One imagines one could do a better job, but fit must work in 3D; we see tiny portion of space • What is going on in the normalization region?(indep of Gaussian ansatz) • ad hoc “fixes” dangerous! • Problem with projections • cannot see systematics in 3D • experiments w/same CF will have different projections STAR Preliminary lisa - XXI Winter Workshop - Breckenridge CO

  35. Whole CF at a glance • Cartesian-space (out-side-long) naturally encodes physics, but is poor/inefficient representation • Recognize symmetries of Q-space -- decompose by spherical harmonics! • Direct connection to source shapes [Danielewicz,Pratt] • ~immune to acceptance • full information content at a glance[thanx to symmetries] lisa - XXI Winter Workshop - Breckenridge CO

  36. L=0 L=2 L=4 “Rinv” But better!! ~acceptance free! RL < RT M=0 RL > RT RO < RS M=2 RO > RS Simple, Gaussian source calculations M=4 lisa - XXI Winter Workshop - Breckenridge CO

  37. L=0 L=2 L=4 M=0 STAR Preliminary M=2 • d+Au kT-integrated • RO = 1.74 fm • RS = 1.69 fm • RL = 2.14 fm • = 0.36 data Gaussian source fit (Coulomb in fit) M=4 lisa - XXI Winter Workshop - Breckenridge CO

  38. Mike’s shortest summary ever(let’s discuss) • Along most axes, HBT systematics make sense • it’s the geometry, stupid & geometry defines R.H.I.C. • so, take “puzzles” seriously • recent “puzzle”: pp/dA/AA HBT versus mT “too similar” • timescales 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 & underway • IMHO* : issues with data but they are not the root cause (also Gaussian is not at root) * IMHO = In Mike’s Humble Opinion lisa - XXI Winter Workshop - Breckenridge CO

  39. Is this what we’ve come (back) to? A.D. Chacon et al, Phys. Rev. C43 2670 (1991) G. Alexander, Rep. Prog. Phys. 66 481 (2003) Take the problem seriously, and nobody gets hurt R = 1.2 (fm)•A1/3 lisa - XXI Winter Workshop - Breckenridge CO

  40. The end lisa - XXI Winter Workshop - Breckenridge CO

  41. local x-p corr. NB: p-space observables identical in the two cases • 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 lisa - XXI Winter Workshop - Breckenridge CO

  42. local x-p corr. NB: p-space observables identical in the two cases • 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 lisa - XXI Winter Workshop - Breckenridge CO

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