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Critical Examination of RHIC Paradigms-mostly high p T

Critical Examination of RHIC Paradigms-mostly high p T. M. J. Tannenbaum Brookhaven National Laboratory Upton, NY 11973 USA.

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Critical Examination of RHIC Paradigms-mostly high p T

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  1. Critical Examination of RHIC Paradigms-mostly high pT M. J. Tannenbaum Brookhaven National Laboratory Upton, NY 11973 USA Workshop on “Critical Examination of RHIC Paradigms” The University of Texas At Austin Austin, Texas, USA April 16, 2010 Paradigms 2010

  2. The Quark Gluon Plasma (QGP) • The QGP should be in chemical (particle type) and thermal equilibrium <pT> ~T • The major problem is to relate the thermodynamic properties, Temperature, energy density, entropy of the QGP or hot nuclear matter to properties that can be measured in the lab. One paradigm that I don’t believe is that one can find the critical point by an energy scan at RHIC: Luciano Moretto says, “critical fluctuations depend on a first order phase transition below the critical point whose large fluctuations drive the critical fluctuations” i.e. is all the interesting physics just outside the E802 aperture? Paradigms 2010

  3. Given the QGP, what is my interest? The QGP is the only place in the universe where we can in principle and in practice understand QCD for color-charged quarks in a color charged medium. How long will it take before we understand this as well as we understand a muon in Cu in QED? slide by Jamie Nagle from PDG following a discussion with me. Paradigms 2010

  4. QED Bremsstrahlung in matter and Xtals • Even for such a seemingly simple reaction as muon bremsstrahlung, there is no simple formula: e.g. see • Apart from the LPM effect, there are also very interesting effects of electron bremsstrahlung in a solid: coherent Brems in a Xtal which increases the radiation; LPM effect which decreases the radiation at low x=k/E; and a medium effect on the forward outgoing photon from Compton scattering off the atomic electrons which if inside the coherence length, kills the dN/dk=1/k divergence. The coherence length is set by tmin. P. Amaral, et al, ATLAS TileCal Collab, EPJC 20(2001)487 Bethe Heitler: LPM Medium- “Dielectric” P.L.Anthony, et al PRD56(1997)1373 Paradigms 2010

  5. Coherent Brems in Diamond-from Texas-SSC Coherent peak at k=9.48 TeV from 10 TeV e Rudolf Baier requests preprint BNL-34614 from MJT dE/dx in QCD in a QGP is much more complicated than in QED. We have barely scratched the surface. MJT-Coherent photon beam from 10 TeV electrons at SSC--Fixed Target Workshop, The Woodlands TX, Jan 26-30, 1984 (based on original code from Roy Schwitters) Paradigms 2010

  6. The first opportunity to study weak interactions at high energy was provided by the development of neutrino beams at the new accelerators in the early 1960’s CERN-SpS , BNL-AGS. • However, it was soon recognized that the intermediate (weak) boson W, might be more favorably produced in nucleon-nucleon collisions. Why were some people studying “high pT”physics in the 1960’s? They were searching for the W boson. Paradigms 2010

  7. UA1,UA2, CERN 1983 W boson discovery The ‘Zichichi signature’ for the W boson PHENIX+STAR 4.0 Parity Violation Proc. 12th ICHEP, Dubna 1964 Paradigms 2010

  8. Searches for W boson in p-p collisions • 1965-1969 Beam dump experiments at ANL-ZGS and BNL-AGS looking for “large angle” muons didn’t find any. [ZGS-Lamb, et al PRL 15, 800 (1965), AGS-Burns, et al, ibid 830, AGS-Wanderer et al, PRL 23,729(1969)] • How do you know how many W should have been produced? • Chilton, Saperstein, Shrauner [PR148, 1380 (1966)] emphasize the importance of the timelike form factor, which is solved by • Y. Yamaguchi [Nuovo Cimento 43, 193 (1966)] Timelike form factor can be found by measuring the number of lepton pairs e+e- or +- “massive virtual photons” of the same invariant mass; BUT the individual leptons from these electromagnetically produced pairs might mask the leptons from the W. • This set off a spate of single and di-lepton experiments, notably the discovery by Lederman et al of “Drell-Yan” production at the BNL-AGS, E70 at FNAL and CCR at the CERN-ISR. Paradigms 2010

  9. AGS-1969-71 Discovery of ‘Drell-Yan’ and ?? p+U+-+X sNN=7.4 GeV This is why I NEVER plot theory curves on any of my data long forgotten Christenson, Lederman…PRL 25, 1523 (1970) `Theory’ Altarelli, Brant Preparata PRL 26 42 (1971) Paradigms 2010

  10. E70-(F)NAL   yield exp -6pT worst imaginable background can suppress by 103  pT=MW/2 LML very excited in 1970: AGS-di continuum +Bj scalingW cross section at any s From Proposal E70 at FNAL + addendum Dec 1970  Paradigms 2010

  11. ?? explained by J/ in 1974 at AGS + SLAC Paradigms 2010

  12. The whole truth--‘Applied HEP’ NA50 PLB 477, 28 (2000) E70 PRL 39 252 (1977) Paradigms 2010

  13. The gold-plated signature for the QGPJ/ Suppression • In 1986, T. Matsui & H. Satz PL B178, 416 (1987) said that due to the Debye screening of the color potential in a QGP, charmonium production would be suppressed since the cc-bar couldn’t bind. • This is CERN’s Heavy Ion’s claim to fame: but the situation is complicated because J/ are suppressed in p+A collisions. [NA50 collaboration, M.C. Abreu, et al., PLB 477, 28 (2000)] Paradigms 2010

  14. How to discover the QGP-1990-91 • The Classical road to success in RHI Physics: J/ Suppression • Major background for e detection is photons and conversions from 0. but more importantly • Need an electron trigger for full J/ detection  EMCal plus electron ID at trigger level. • High pT0 and direct  production and two-particle correlations are the way to measure hard-scattering in RHI collisions where jets can not be detected directly---> segmentation of EMCal must be sufficient to distinguish 0 and direct  up to 25 GeV/c (also vital for spin) • Charm measurement via single e (Discovered by CCRS experiment at CERN ISR) • So we designed PHENIX to make these measurements Paradigms 2010

  15. As the expected energy in a typical jet cone is  R2 x1/ 2 x dET/d= R2/2 x dET/d ~ 300 GeV for R=1 at sNN=200 GeV where the maximum Jet energy is 100 GeV, Jets can not be reconstructed in Au+Au central collisions at RHIC. The first paradigm change:BDMPS 1997-1998 In 1998 at the QCD workshop in Paris, Rolf Baier asked me whether jets could be measured in Au+Au collisions because he had a prediction of a QCD medium-effect on colored partons in a hot-dense-medium with lots of unscreened color charge. But hard-scattering can be well studied by single inclusive and 2-particle correlation measurements as it was discovered at the CERN ISR in the 1970’s: “Everything you want to know about JETS can be measured with two particle correlations.” And it just so happened that the PHENIX detector was designed to trigger, measure and separate  and 0 out to pT> 25 GeV/c ! Paradigms 2010

  16. Three things are dramatically different in Relativistic Heavy Ion Physics than in p-p physics • the multiplicity is ~A~200 times larger in AA central collisions than in p-p huge energy in jet cone: 300 GeV for R=1 at sNN=200 GeV • huge azimuthal anisotropies which don’t exist in p-p which are interesting in themselves, and are useful, but sometimes troublesome. • space-time issues both in momentum space and coordinate space are important in RHI : for instance what is the spatial extent of parton fragmentation, is there a formation time/distance? Paradigms 2010

  17. Example of space-time issues • When in time and space does a parton fragment? Is this different for light and heavy quarks? When are particles formed? • Dokshitser textbook formula: F=ER2tF=R=ER/M=ERc • Would a proton embedded in a QGP dissolve? How long does this take? How is this related to J/Psi suppression? Paradigms 2010

  18. p-p Thermally-shaped Soft Production: e-6pT indep. s Hard Scattering -- varies with s p0's in p+p s=200 GeV: Data vs. pQCD • Result from run2 published-a classic • PRL91 (2003) 241803 • New result from run5 • preliminary • Comparison of 0cross section • Next-to-leading order(NLO) pQCD • CTEQ6M + KKP or Kretzer • Matrix calculation by Aversa, et. al. • Renormalization andfactorization scales are set to be equal and set to 1/2pT, pT, 2pT • Calculated by W.Vogelsang NLO-pQCD described very well down even to pT ~ 1 GeV/c Inclusive invariant 0 spectrum is pure power law for pT≥3 GeV/c n=8.1±0.1 Paradigms 2010

  19. Soft Physics Dominates Particle production in both p-p and A+A (Relativistic Heavy Ion) collisions Paradigms 2010

  20. High pT particle High pT particle Au+Au p+p PRC 71 (2005) 034908 4% c0 Bj =5.40.6 GeV fm-2 0.5% AuAu Central Collisions cf. p-p STAR-Jet event in pp STAR Au+Au central PHENIX Au+Au central Paradigms 2010 per unit velocity || to beam

  21. 4% 0.5% p+p RHIC Au+Au ET spectra at AGS and RHIC are the same shape!!!   PRC 71 (2005) 034908 /8 0.76 /4 0.76 c0 Bj =5.40.6 GeV fm-2 3/8 0.76 /2 0.76 5/8 0.76 i.e no critical fluctuations 1600 3200 LHC ? Paradigms 2010

  22. AA Paradigm we should do away with Although it may be sensible for the average it makes no sense for the distribution which would look like the weighted sum of the Npart + Ncoll curves, which looks nothing like the actual distribution Paradigms 2010

  23. a soft physics question for the LHC • Will the QGP at the LHC be a superfluid like the liquid He coolant in the magnets? • [H. Song and U. Heinz Phys. Rev. C78 (2008) 024902] : viscous hydro is more sensitive to /s than to the peak energy density e0, so v2 shouldn’t change much 15-20% from RHIC to LHC. [Busza-Last Call LHC] extrapolation of measured v2 vs sNN predicts an increase by a factor of 1.6 from RHIC to LHC. Will this be the failure of hydro? Another paradigm about to fall soon? Paradigms 2010

  24. Now, Back To Hard-Scattering Paradigms 2010

  25. 1968--Deeply Inelastic scattering of electrons on protons observed at SLAC. First direct indication of sub-constituents of proton, “partons” as explained by Bjorken scaling [J.D. Bjorken, Phys. Rev. 179, 1547 (1969)] • 1971--High pT scattering of “partons” via QED predicted for p-p collisions by Bjorken, Berman, Kogut [BBK, Phys. Rev. D4, 3388 (1971)] • 1972 First evidence of hard-scattering of constituents discovered at CERN ISR--attention turns from spectroscopy to “high pT physics” • 1974--J/ discovered at BNL and SLAC-people start believing that partons are real and are the same as quarks. • 1972-1982 properties of hard-scattering and “Jets” mapped out at CERN-ISR for a decade 1975,1977-78 first theory papers on QCD applied to hard-scattering • 1982-Constituent-scattering Angular distribution measured at ISR in agreement with QCD. (Rutherford scattering of quarks). SppS (UA2)- first observation of unbiased Jets in hadron collisions. Timeline of hard-constituent Scattering Paradigms 2010

  26. Phys. Rev. 179, 1547 (1969) Phys. Rev. 185, 1975 (1969) Bjorken Scaling in Deeply Inelastic Scattering and the Parton Model---1968 Paradigms 2010

  27. BBK 1971 S.M.Berman, J.D.Bjorken and J.B.Kogut, Phys. Rev. D4, 3388 (1971) • BBK calculated for p+p collisions, the inclusive reaction • A+B C + Xwhen particle C has pT>> 1 GeV/c • The charged partons of DIS must scatter electromagnetically “which may be viewed as a lower bound on the real cross section at large pT.” Paradigms 2010

  28. CCR at the CERN-ISRDiscovery of high pT0production in p-p F.W. Büsser, et al., CERN, Columbia, Rockefeller Collaboration Phys. Lett. 46B, 471 (1973) Bjorken scaling PR179(1969)1547  BermanBjKogut scaling PRD4(71)3388  Blankenbecler, Brodsky, Gunion xT=2pT/s Scaling PL 42B, 461 (1972) neff gives the form of the force-law between constituents: neff=4 for QED • e-6pT breaks to a power law at high pT with characteristic s dependence • Large rate indicates that partons interact strongly (>> EM) with other. • Data follow xT=2pT/s scaling but with neff=8!, not neff=4 as expected for QED Paradigms 2010

  29. CCOR 1978--Discovery of “REALLY high pT>7 GeV/c” at ISR CCOR A.L.S. Angelis, et al, Phys.Lett. 79B, 505 (1978) 8 QCD: Cahalan, Geer, Kogut, Susskind, PRD11, 1199 (1975) 5 neff=5 (=4++) as predicted for QCD Paradigms 2010

  30. 1978-neff(xT, s) WORKS neff5=4++ C.Kourkoumelis, et al Phys.Lett. 84B, 279 (1979) A.Adare, et al, PHENIX PRD79 (2009) 012003 cross sections vary by factor of 2 But n(xT,s) agrees Paradigms 2010

  31. CCRS-1974 Discovery of direct e~10-4 at ISR not due to internal conversion of direct photons CCRS PLB53(1974)212; NPB113(1976)189 Data points (e++e-)/2 lines 10-4 (++-)/2 Farrar and Frautschi PRL36(1976)1017 proposed that direct leptons are due to internal conversion of direct photons with /~10-20% to e+e- (d/dm~1/m) for pT>1.3 GeV/c. CCRS looks, finds very few events, sets limits excluding this. p.s. these direct e are due to semi-leptonic decay of charm particles not discovered until 1976, 2 year later: Hinchliffe and Llewellyn-Smith NPB114(1976)45 Paradigms 2010

  32. J/Psi and direct e First Best Not cause of direct e CCRS PLB56(1975)482 2nd J/ in Europe CSZ NPB142(1978)29 pT=1.100.05 GeV/c CCRS NPB113(1976)189 direct e not due to J/ Paradigms 2010

  33. isolatedphotons  q Compton g q  q Annihilation g q Cross Section /0 Correlations pTtrig>6 GeV/c ISR direct photon production + correlations QCD Fritzsch and Minkowski, PLB 69 (1977) 316-320--ISR discovery R806-A2BC-PLB 87(1979)292. No evidence for bremss. contribution to direct --same side correlation is zero--see CMOR NPB327, 541 (1989) for full list of references. Paradigms 2010

  34. Status of ISR single particle measurements 1978 kT is what made n=4++ n=8 Paradigms 2010

  35. Status of QCD Theory in 1978 • The first modern QCD calculation and prediction for high pT single particle inclusive cross sections including non-scaling and initial state radiation was done in 1978 by J. F. Owens, E. Reya, M.Gluck, PRD 18, 1501 (1978), “Detailed quantum-chromodynamic predictions for high-pT processes,” and J.F. Owens, J. D. Kimel, PRD 18, 3313 (1978), “Parton-transverse-momentum effects and the quantum-chromodynamic description of high-pT processes”. • This work was closely followed and corroborated by Feynman, Field, Fox PRD 18, 3320 (1978), “Quantum-chromodynamic approach for the large-transverse-momentum production of particles and jets.” • Unfortunately jets in 4 Calorimeters at ISR energies or lower are invisible below GeV, which led to considerable confusion in the period 1980-1982. Paradigms 2010

  36. QCD and Jets are now a cornerstone of the standard model • Incredibly at the famous Snowmass conference in July 1982, many if not most people in the U.S. were skeptical e.g. MJT Seminar in 1982 • The International HEP conference in Paris, three weeks later, July 26--31, 1982 changed everything. Paradigms 2010

  37. At the CERN ISR from 1975-1982 two-particle correlations showed unambiguously that high pT particles come from jets Paradigms 2010

  38. pTt pT pout=pT sin xE pTt How everything you want to know about JETS was measured with 2-particle correlations CCOR, A.L.S.Angelis, et al Phys.Lett. 97B, 163 (1980) PhysicaScripta 19, 116 (1979) pTt > 7 GeV/c vs pT Away side pout~pT is not constant i.e  1/pT, indicating jets not collinear in azimuth kT Paradigms 2010

  39. xE distribution measures fragmentation fn. xE ~ z/<ztrig> same data (pTt>7 GeV/c) <ztrig>=0.85 measured Dq(z)~e-6z independent of pTt See M. Jacob’s talk Proc. EPS 1979 Geneva (CERN). p512 Regarding CDF PRD79,112005, this plot from 1979 showed that there were NO di-jets each of a single particle as claimed by another ISR exp’t (p511) since there was no peak at xE=1 At RHIC we learned that the xE distribution from a trigger fragment does not measure the fragmentation function. Paradigms 2010

  40. Where did I (and everybody in HEP) get this idea?---from Feynman, Field and Fox FFF Nucl.Phys. B128(1977) 1-65 “There is a simple relationship between experiments done with single-particle triggers and those performed with jet triggers. The only difference in the opposite side correlation is due to the fact that the ‘quark’, from which a single-particle trigger came, always has a higher p than the trigger (by factor 1/ztrig). The away-side correlations for a single-particle trigger at p should be roughly the same as the away side correlations for a jet trigger at p (jet)= p (single particle)/ <ztrig>”. Paradigms 2010

  41. THE UA2 Jet-Paris 1982 From 1980--1982 most high energy physicists doubted jets existed because of the famous NA5 ET spectrum which showed NO JETS. This one event from UA2 in 1982 changed everybody’s opinion. Paradigms 2010

  42. CCOR Jets after 8 orders of mag. PL 126B, 132 (1983) Also Paris 1982-Jets in ET distribution s=24.3 GeV NA5-1980 ICHEP-No Jets 7 orders of magnitude Paradigms 2010

  43. C A a c X b B d LO-QCD in 1 slide Paradigms 2010

  44. Also Paris1982-first measurement of QCD subprocess angular distribution using 0-0 correlations DATA: CCOR NPB 209, 284 (1982) QCD Paradigms 2010

  45. British French Scandinavian “Ridge” Split Field magnet, horrible magnetic field uniformity. Track recon took ~5 yrs to develop + 1 hour of CDC7600 per hour of data! Great acceptance when it finally worked. BFS NPB145(1978) 308 Paradigms 2010

  46. For the past decade these single and two-particle techniques were used exclusively at RHIC for hard-scattering, with outstanding results... Paradigms 2010

  47. 19% norm uncertainty p-p collisions at RHIC: 0 production (PHENIX) s=200 GeV hard component is difference between exp-5.6pT and data No surprise (to me) that NLO pQCD agrees with data PRD76(2007)051006(R) Paradigms 2010

  48. 0 are suppressed in Au+Au eg 200 GeV p-p Nuclear Modification Factor 0 invariant cross section in p-p at s=200 GeV is a pure power law for pT > 3 GeV/c, n=8.10.1 ISR 0 vs RHIC p-p  RHIC pp vs AuAu Paradigms 2010

  49. PHENIX PRL 91 (2003) 172301 p/ ratio much larger than from jet fragmentation or bulk: The Baryon Anomaly-still not understood ps: If this is ‘recombination’  QGP: Fries,Muller, Nonaka PRL 90 202303 (2003) The baryon anomaly is not due to recombination PHENIX PLB 649 (2007) 359 Trigger mesons and baryons in the region of the baryon anomaly both show the same trigger (near) side and away side jet structure. This ‘kills’ the elegant recombination model of the baryon anomaly. Paradigms 2010

  50. L RAA0 in AuAu sNN=200 GeV vs. Reaction Plane to probe details of the theory-learn something new! Phys Rev C 76, 034904 (2007) Phys Rev C 80, 054907 (2009) L = distance from edge to center of participants calculated in Glauber model Little/no energy loss for Le< 2 fm 3 < pT < 5 GeV/c RAA is absolute, v2 is relative so no hint of this in v2 measurements. This result also suggests that v2 for pT>2GeV/c is due to anisotropic energy loss not flow. RAA() vs. centrality varies density of and distance through medium Paradigms 2010

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