Brookhaven National Laboratory Overview of Resonance Production P. Fachini Brookhaven National Laboratory 4/21/2019 Patricia Fachini

Motivation Measured Resonances Masses and Widths Spectra and Yields Ratios Outlook 4/21/2019 Patricia Fachini

Motivation 4/21/2019 Patricia Fachini

Motivation - I Medium modification of mass and/or width  Chiral Symmetry Restoration, Collision Broadening and/or Phase Space? ρ0 leptonic decay channel  probes all stages of the collision R. Rapp and J. Wambach, Adv. Nucl. Phys. 25, 1 (2000); G. E. Brown and M. Rho, Phys. Rev. Let. 66 2720 (1991); P. Braun-Munzinger, GSI Internal Report ρ0 + - π- π+ ρ0 π- π+ ρ0 c = 1.3 fm ρ0 hadronic decay channel  probes late stages of the collision 4/21/2019 Patricia Fachini

Motivation - II Φ  information early stages of the collision Φ  modification mass shape and width Φ  different production for hadronic and leptonic channels Nucleon-nucleon collisions  η, ω and ρ0 at high pT  perturbative QCD A+A collisions  η, ω and ρ0 at high pT  nuclear effects can modify particle production Δ++  mass and width modification in medium K*  time between chemical and kinetic freeze-out Φ c = 44 fm S. Pal et al., Nucl.Phys. A707 (2002) 525-539 RHIC Δ++ Hees and Rapp Hot Quarks04 Hees and Rapp, HotQuarks04 4/21/2019 Patricia Fachini

Motivation - III If resonance decays before kinetic freeze-out  not reconstructed due to rescattering of daughters K*0 (c = 4 fm) survival probability  time between chemical and kinetic freeze-out, source size and pT of K*0 Chemical freeze-out  elastic interactions πK  K*0 πK regenerate K*0(892) until kinetic freeze-out K*0/K may reveal time between chemical and kinetic freeze-out K* measured π K K* K* lost π K K* π K* K K* measured Chemical freeze-out Kinetic freeze-out 4/21/2019 Patricia Fachini

Measured Resonances 4/21/2019 Patricia Fachini

Resonance Production Life Time ρ0(770)  π+ π- B.R. ~1 c = 1.3 fm Δ++(1232)  p π+ B.R. ~1 c = 1.6 fm K*(892)  π K B.R. ~1 c = 4 fm Σ(1385)  Λ π B.R. 0.88 c = 5.5 fm Λ(1520)  p K B.R. 0.45 c = 12.6 fm Ξ(1530)  Ξ π B.R. ~1 c = 21 fm ω(782)  π+ π- π0 B.R. 0.89 c = 23 fm ω(782)  π0 B.R. 0.089 c = 23 fm Φ(1020)  K+ K- B.R. 0.49 c = 44 fm Φ(1020)  e+e- B.R. 0.000296 c = 44 fm η(547)  π+ π- π0 B.R. 0.23 c = 167225 fm Life Time 4/21/2019 Patricia Fachini

Δ++(1232)  p π+ B.R. ~1 c = 1.6 fm √sNN = 200 GeV √sNN = 200 GeV STAR Preliminary STAR Preliminary √sNN = 200 GeV √sNN = 200 GeV 4/21/2019 Patricia Fachini

K*(892)  π K B.R. ~1 c = 4 fm √sNN = 200 GeV √sNN = 200 GeV STAR Preliminary STAR Preliminary √sNN = 200 GeV √sNN = 200 GeV √sNN = 62 GeV STAR Preliminary 4/21/2019 Patricia Fachini

Σ(1385)  Λ π B.R. 0.88 c = 5.5 fm Λ(1520)  p K B.R. 0.45 c = 12.6 fm Ξ(1530)  Ξ π B.R. ~1 c = 21 fm Ξ* STAR Preliminary Au+Au √sNN = 200 GeV √sNN = 200 GeV STAR Preliminary Λ* Minimum Bias d+Au STAR Preliminary 4/21/2019 Patricia Fachini

ω(782)  π+ π- π0 B.R. 0.89 c = 23 fm ω(782)  π0 B.R. 0.089 c = 23 fm η(547)  π+ π- π0 B.R. 0.23 c = 167225 fm p+p Au+Au PHENIX η,ω π+ π- π0 p+p ω π0 ω π0 PHENIX √sNN = 200 GeV PHENIX 4/21/2019 Patricia Fachini

Φ(1020)  K+ K- B.R. 0.49 c = 44 fm Φ(1020)  e+e- B.R. 0.000296 c = 44 fm d+Au PHENIX Φ K+ K- STAR Preliminary √sNN = 200 GeV Au+Au PHENIX Φ e+e- √sNN = 200 GeV 4/21/2019 Patricia Fachini

Sub-Threshold Measurements K(892) (< 800 MeV) Σ(1385) (< 400 MeV) Σ*±   + ± K*0  K+ + - Al+Al 1.9 AGeV FOPI Al+Al 1.9 AGeV FOPI 4/21/2019 Patricia Fachini

π+π- Invariant Mass Distribution from Monte Carlo HIJING events with a realistic simulation of detector response K0S  π+ π- K0S STAR Preliminary ω(782)  (π+ π-) π0 and π+ π- ω sNN = 200 GeV ρ0(770)  π+ π- η  (π+ π-) π0 and (π+ π-)  η’  (π+ π-) η and (π+ π-) ρ0 η + η’ K*(892)0  K π with K misidentified as π K*0 + K*0 misidentified ρ0 Use ω and K*0 shape from HIJING to fit the data K*0 signal is fixed using STAR measurement 4/21/2019 Patricia Fachini

ρ0(770)  π+ π- B.R. ~1 c = 1.3 fm 40-100% dAu STAR Preliminary STAR Preliminary 40-100% dAu 0.6 ≤ pT < 0.8 GeV/c 20-40% dAu 0.6 ≤ pT < 0.8 GeV/c √sNN = 200 GeV √sNN = 200 GeV STAR Preliminary STAR Preliminary 40-80% Au+Au 0.6 ≤ pT < 0.8 GeV/c 0-20% dAu 0.6 ≤ pT < 0.8 GeV/c √sNN = 62 GeV √sNN = 200 GeV 4/21/2019 Patricia Fachini

Masses and Widths 4/21/2019 Patricia Fachini

K*  Mass and Width STAR Preliminary MC K*0  pT < 1 GeV  mass shift of ~10 MeV observed K*± and K*0  pT > 1 GeV  mass agrees with PDG for all systems within errors Width agrees with PDG for all systems within errors Systematic error shown for minimum bias d+Au 200 GeV PDG K*0 PDG K*± PDG STAR Preliminary 4/21/2019 Patricia Fachini

Δ++  Mass and Width PDG Δ++ mass shift observed in both minimum bias p+p and d+Au at √sNN = 200 GeV Width agrees with PDG for both systems within errors PDG 4/21/2019 Patricia Fachini

ω  Mass No mass shift observed in both minimum bias p+p and d+Au at √sNN = 200 GeV Statistical error shown PDG fit PDG fit 4/21/2019 Patricia Fachini

ρ0  Mass Mass shift observed for all systems STAR Preliminary Mass shift observed for all systems Towards the vacuum value at high pT? Systematic errors shown for Minimum Bias d+Au 200 GeV 4/21/2019 Patricia Fachini

ρ0  Hadronic channel  STAR (RHIC) Probing late of the collisions Mass shift ~70 MeV 4/21/2019 Patricia Fachini

ρ0  Dimuons channel  NA60 (SPS) Hees and Rapp, hep-ph/0603084 Probing all stages of the collisions Mass broadening 4/21/2019 Patricia Fachini

Mass Shift in A+A Hees and Rapp, hep-ph/0603084 SPS RHIC STAR ~70 MeV mass shift measured by STAR in peripheral Au+Au collisions and no apparent broadening Broadening measured by NA60 in central In-In collisions and no mass shift Are these measurements in agreement? RHIC  di-lepton measurements! 4/21/2019 Patricia Fachini

ρ0 Mass at High-PT 4/21/2019 Patricia Fachini

ρ0  Mass at High pT η production fixed according to PHENIX data K0s production fixed according to STAR data ρ0 mass = 775.9 MeV fixed ρ0 width = 160 MeV fixed f0 mass = 980 MeV fixed f0 width = 100 MeV fixed f2 mass = 1275 MeV fixed f2 width = 185 MeV fixed In p+p  ω and ρ0 production are assumed to be the same 4/21/2019 Patricia Fachini

ρ0  Mass at High pT STAR Preliminary Background STAR Preliminary p+p 200GeV Central Au+Au 200GeV STAR Preliminary ρ0 mass at high pT  pure relativistic BW function ρ0 mass at high pT  equivalent measurement e+e- Mass shift observed at low pT is not a detector effect! Phys. Rev. Lett. 92 (2004) 092301 Minimum Bias Au+Au 200GeV 4/21/2019 Patricia Fachini

Masses and Widths No mass or width modification of η, ω, Φ, Λ*, Σ* or Ξ* Mass shift observed for K*, Δ++ and ρ0 at low-pT  possible explanations π+ π- rescattering in p+p collisions Medium modifications Bose-Einstein correlations ρ0 at high-pT  No apparent mass shift! P. Fachini et.al., J.Phys.G33:431-440,2007 R. Rapp, Nucl.Phys. A725, 254 (2003), E.V. Shuryak and G.E. Brown, Nucl. Phys. A 717 (2003) 322 G.D. Lafferty, Z. Phys. C 60, 659 (1993); R. Rapp, Nucl.Phys. A725 (2003) 254-268 S. Pratt et al., Phys.Rev. C68 (2003) 064905 4/21/2019 Patricia Fachini

Spectra 4/21/2019 Patricia Fachini

Spectra-I STAR Preliminary STAR Preliminary 4/21/2019 Patricia Fachini

Spectra-II K*0 Au+Au √sNN = 62 GeV √sNN = 200 GeV 4/21/2019 STAR Preliminary STAR Preliminary √sNN = 200 GeV 4/21/2019 Patricia Fachini

Spectra-III Φ  K+ K- 4/21/2019 Patricia Fachini STAR Preliminary

Spectra-IV Au+Au 62 GeV 4/21/2019 Patricia Fachini

Φ Production  K+K- and e+e- The leptonic channel yield is a little higher than hadronic channel More accurate measurement is required to confirm whether there is branch ratio modification 4/21/2019 Patricia Fachini

Φ Production  K+K- J. Rafelski et al.,Phys.Rev. C72 (2005) 024905 STAR Φ production  there is a factor of ~2 difference between PHENIX and STAR! BRAHMS measurement agrees with STAR at midrapidity PHENIX STAR + PHENIX √sNN = 200 GeV 4/21/2019 Patricia Fachini

Ratios 4/21/2019 Patricia Fachini

Φ  Ratios Φ/K- independent of centrality STAR Preliminary Φ/K- independent of centrality UrQMD does not reproduce data  kaon coalescence not the main production mechanism for Φ! Φ/K- reproduced by thermal models  no rescattering (or regeneration) due to c = 44 fm 4/21/2019 Patricia Fachini

Resonance to stable particle ratios √sNN = 200 GeV c = 1.3 fm c = 4 fm c = 1.6 fm c = 12.6 fm c = 5.5 fm STAR Preliminary ρ0, Δ++ and Σ*  ratios independent of centrality or system size K* and Λ*  suppression compared to p+p collisions 4/21/2019 Patricia Fachini

Time between freeze-outs If rescattering is the dominant process, And the time between chemical and kinetic freeze-out should be Δt = 2 ± 1 fm If no regeneration is present  Δt = 2 ± 1 fm Blast-Wave fit to π±, K±, p, and p  Δt > 6 fm N(Δt) = N0 e c t - e = c Δt - K*0 K- Au+Au p+p = 0.23 0.35 4/21/2019 Patricia Fachini

K*  Ratios STAR Preliminary Statistical errors only K*/K- ratio in central collisions at 62 GeV and 200 GeV are comparable  same time between chemical and kinetic freeze-outs 4/21/2019 Patricia Fachini

η, ω and ρ0  Ratios η STAR Preliminary ω/π0 ratio constant for pT > 2 GeV  lower than PYTHIA  ω/π0 = 1.0 ρ0/π- ratio constant for 5 < pT < 10 GeV  lower than PYTHIA η/π0 ratio  comparable to PYTHIA ω/π0 and ρ0/π- measured  comparable √sNN = 200 GeV ρ0  π+ π- 4/21/2019 Patricia Fachini

Ratios Φ/K- independent and constant for all collision systems  kaon coalescence not the main production mechanism for Φ! Φ/K- reproduced by thermal models  no rescattering (or regeneration) due to c = 44 fm ρ0, Δ++ and Σ*  ratios independent of centrality K* and Λ*  suppression compared to p+p collisions K*/K- ratio in central collisions at 62 GeV and 200 GeV are comparable  same time between chemical and kinetic freeze-outs ρ0/π- ratio constant for 5 < pT < 10 GeV  lower than PYTHIA ω/π0 and ρ0/π0 measured  comparable 4/21/2019 Patricia Fachini

Outlook What’s next? We need: Systematic study of K*0 and Δ++ mass and width in Au+Au (RUN4) ρ0 in central Au+Au  overwhelming combinatory background ρ0 in central Cu+Cu  doable… Λ(1520), Σ(1385), Ξ(1530)… Other higher state resonances… High-pT and v2 measurements of resonances a1  γ π±  e+e- π± Leptonic Channel Φ, ρ  Comparison between leptonic and hadronic channels in A+A!!! Requires Large statistics RHIC Upgrades Low mass dileptons  PHENIX (HBD) and STAR (TOF) TOF full coverage  STAR 4/21/2019 Patricia Fachini

Backup Slides 4/21/2019 Patricia Fachini

Φ  Mass and Width STAR Preliminary pT > 1 GeV  mass and width agree with MC and PDG for all systems pT < 1 GeV  mass agrees with MC for all systems within errors pT < 1 GeV  width higher than MC for all systems  real physics or detector effect? No significant mass or width modification observed PDG STAR Preliminary PDG 4/21/2019 Patricia Fachini

Elliptic Flow - I KS0 and Λ v2  scale number constituent quarks  v2/n Resonance v2  πK  K*  n = 4 qq  K*  n = 2 Significant K*0 v2 measured Fitting K*0 v2 to a, b, c, and d  constants extracted using KS0 and Λ v2 K*0 v2  n= 2.0 ± 0.3 C. Nonaka et al., Phys.Rev. C69 (2004) 031902 X. Dong et al., Phys.Lett. B597 (2004) 328 v2(pT,n) = - dn 1 + exp[-(pT/n – b)/c] an Minimum Bias Au+Au 200GeV STAR Preliminary 4/21/2019 Patricia Fachini

Elliptic Flow - II Significant Φ v2 measured v2 increases with decreasing centrality Φ not produced via kaon coalescence  Φ information from early stages  non-zero Φ v2  s-quarks flow  Partonic collectivity Intermediate pT  Φ v2 consistent with KS0 than Λ  favors NCQ=2  Recombination/ Coalescence models Φ v2  n= 2.3 ± 0.4 Au+Au 200GeV 4/21/2019 Patricia Fachini

Elliptic Flow s-quarks flow as u- and d-quarks Φ not produced via kaon coalescence and do not participate strongly in hadronic interactions  evidence for partonic collectivity! Φ and K*  intermediate pT  formed via quark-quark coalescence 4/21/2019 Patricia Fachini

Nuclear Modification Factor K*(892) and Φ  mesons K*(892) and Φ  mass closer to Λ mass K* and Φ RCP  intermediate pT  closer to KS0 than Λ  evidence for baryon/meson effect  favors parton recombination 4/21/2019 Patricia Fachini

Φ  Ratios Chemical freeze-out Chemical = Kinetic freeze-out STAR Φ/K-  ratio reproduced by thermal model  Φ has long lifetime!  not affected by rescattering (or regeneration) 4/21/2019 Patricia Fachini

K*  Ratios STAR Chemical freeze-out Kinetic freeze-out Chemical = Kinetic freeze-out K*/K-  p+p ratio reproduced by thermal model at chemical freeze-out  Au+Au reproduced by thermal model at kinetic freeze-out 4/21/2019 Patricia Fachini

Previous Measurements? ρ0 No detailed mass measurements Mass integrated in pT, xF, xp STAR measurement  ρ0 mass shifted ~40 MeV in minimum bias p+p Considerably large mass shift Mass shift observed before! Previous ρ0 mass measurements  NA27, OPAL, DELPHI, and ALEPH NOTE: Previous experiments interested in cross-sections and NOT in mass! 4/21/2019 Patricia Fachini

ρ0-meson Measured in p+p  NA27 √s = 27.5 GeV The ρ0 mass obtained by fitting same event distribution of π+π- to BG + PS x BW = BG + BGxBW = BG(1 + BW) BW = Breit-Wigner BG = Background PS = Phase Space π+π- pT > 0 xF > 0 PS = BG xF = pLongitudinal pTotal Signal Signal π+π- distribution after background subtraction Background  exponential function Signal Same event distribution π+π- 4/21/2019 Patricia Fachini

ρ0-meson Measured in p+p  NA27 CERN  √s = 27.5 GeV ρ0 mass = 762.6 ± 2.6 MeV/c2  only p+p measurement used in average by PDG PDG average “other reactions” hadroproduced  ρ0 mass = 769.0 ± 0.9 MeV/c2 PDG average e+e- (exclusive)  ρ mass = 775.9 ± 0.5 MeV/c2  The position of the ρ0 peak is clearly below reported value 762.6 MeV/c2 775.9 MeV/c2 “scanned version” 4/21/2019 Patricia Fachini

ρ0-meson Measured in p+p  NA27 BW(M) = Γ(M) (M2 – Mρ2)2 + Mρ2 Γ(M)2 Γ(M) = Γρ M2 – 4mπ2 Mρ2 – 4mπ2 3 2 Mρ M Fitting to a p-wave BW function  M = 747.6 ± 2.0 MeV 4/21/2019 Patricia Fachini

ρ0-meson Measured in e+e-  LEP √s = 90 GeV OPAL  ρ0 mass shifted by ~70 MeV/c2 at low xp and no shift at high xp (xp ~1) OPAL  -10 to -30 MeV/c2 shift in the position of the maximum of the resonance ρ±  consistent with ρ0 measurement DELPHI  0.1 < xp < 0.4  ρ0 peak fit to (BWxBG) + BG  ρ0 mass = 757 ± 2 MeV/c2  five standard deviations below PDG value ALEPH  same ρ0 mass shift observed by OPAL ­ Jetset 7.3 + ALEPH Data xp = E(meson) E(beam) ρ0 ­ Jetset 7.2 ● OPAL Data ρ0 4/21/2019 Patricia Fachini

Phase Space -  M2 + pT2 M e T Phase Space =  M2 + pT2 π+ ρ0 π- M = Invariant Mass; pT = transverse momentum; T = Inverse Slope pp  particle composition reasonably reproduced by statistical model  T = 160 MeV  also dAu F. Becattini, Nucl. Phys. A 702, 336 (2002); Z. Phys. C 69, 485 (1996); F. Becattini and U. Heinz, Z. Phys. C 76, 269 (1997) Au+Au  between chemical and kinetic freeze-out  resonances formed until particles too far apart  resonances emitted T = 120 MeV E.V. Shuryak and G.E. Brown, Nucl. Phys. A 717 (2003) 322 Γ(M) = Γρ M2 – 4mπ2 Mρ2 – 4mπ2 3 2 Mρ M BW(M) = Γ(M) (M2 – Mρ2)2 + Mρ2 Γ(M)2 P. Braun-Munzinger et.al., CERES Int. Note, March 2000, unpublished; E.V. Shuryak and G.E. Brown, Nucl. Phys. A 717 (2003) 322; P.K. Kolb and M. Prakash, nucl-th/0301007; H.W. Barz et al., Phys. Lett. B 265, 219 (1991); R. Rapp, hep-ph/0305011. 4/21/2019 Patricia Fachini

Transport Model - UrQMD Au+Au Au+Au b ≤ 3 fm b ≤ 3 fm 0 ρ0 √sNN = 200 GeV 1.2 ≤ pT < 1.4 GeV/c |y| ≤ 0.5 0.2 ≤ pT < 0.4 GeV/c |y| ≤ 0.5 BW × PS Mρ = 769 MeV/c2 UrQMD  Only imaginary part  No medium modification Central Au+Au  ρ0 mass shifted ~30 MeV at low pT ρ0 shape reproduced by p-wave Breit-Wigner × Phase Space Mρ= 765.6 MeV for 0.2 ≤ pT < 0.4 GeV/c Mρ = 761.2 MeV for 1.2 ≤ pT < 1.4 GeV/c Mρ = 769 MeV/c2 input Г = 150 MeV 4/21/2019 Patricia Fachini

Nuclear Modification Factor If no “effects”: R < 1 in regime of soft physics R = 1 at high-pt where hard scattering dominates 4/21/2019 Patricia Fachini

Nuclear Modification Factor 4/21/2019 Patricia Fachini

Elliptic Flow  v2 Coordinate-space-anisotropy  Momentum-space-anisotropy Nuclei Non-central Collisions  Hot System Elliptic Shape y x py Px  4/21/2019 Patricia Fachini

Quark or Hadron Combination v2(pT,n) = - dn 1 + exp[-(pT/n – b)/c] an Number of constituent quarks Constants extracted by fitting the K0s and Λ v2 4/21/2019 Patricia Fachini

K*0 Mass and Width  pp and Au+Au √sNN = 200 GeV |y|< 0.5 Central Au+Au STAR Preliminary STAR Preliminary Central Au+Au PDG value pp pp PDG value K*0 mass  shifted in pp and Au+Au at low pT K*0 width  agrees with the MC (GEANT) calculation Systematic and statistical error added in quadrature 4/21/2019 Patricia Fachini

Spectra Change of Φ spectra from Levy function shape in peripheral Au+Au to exponential in central Au+Au collisions  different production mechanisms of Φ? Matter formed in central Au+Au collisions favors soft Φ production 4/21/2019 Patricia Fachini

Φ  Number of Participants STAR Preliminary STAR Preliminary Φ production increases with Npart (size of the collision system) Same Npart  production increases with collision energy There is still a difference in Φ production between STAR and PHENIX 4/21/2019 Patricia Fachini

K*  Number of Participants STAR Preliminary STAR Preliminary K* production seems to scale with Npart (size of the collision system) for all systems 4/21/2019 Patricia Fachini

Φ  Ratios Φ yield increases faster than π- STAR Preliminary Φ yield increases faster than π- Ratio in Au+Au enhanced compared to p+p Same enhancement for √sNN > 10 GeV  no clear conclusion strangeness enhancement Φ/K- independent of centrality UrQMD does not reproduce data  kaon coalescence not the main production mechanism for Φ! Φ/K- reproduced by thermal models  no rescattering (or regeneration) due to c = 44 fm STAR Preliminary 4/21/2019 Patricia Fachini

Spectra and Yields K* production scales with the size of the collision system Change of Φ spectra from Levy function shape in peripheral Au+Au to exponential in central Au+Au collisions  different production mechanisms of Φ Φ production increases with participant pair  something happening towards central collisions? Φ  the leptonic channel yield is a little higher than hadronic channel  more accurate measurement is required to confirm whether there is branch ratio modification 4/21/2019 Patricia Fachini

Φ and K*  Spin Alignment Proposed pT dependence on different hadronization mechanism  the deviation from ρ00 = 1/3 are predicted to be small  not enough sensitivity in the data! K*0 (0.8<pT<5.0 GeV/c) ρ00 = 0.33 ± 0.04 ± 0.12 Φ (0.4<pT<5.0 GeV/c) ρ00 = 0.34 ± 0.02 ± 0.03 4/21/2019 Patricia Fachini

Motivation - I Medium modification of mass and/or width  Chiral Symmetry Restoration, Collision Broadening and/or Phase Space? ρ0 leptonic decay channel  probes all stages of the collision R. Rapp and J. Wambach, Adv. Nucl. Phys. 25, 1 (2000); G. E. Brown and M. Rho, Phys. Rev. Let. 66 2720 (1991); P. Braun-Munzinger, GSI Internal Report ρ0 + - π- π+ ρ0 π- π+ ρ0 c = 1.3 fm ρ0 hadronic decay channel  probes late stages of the collision Φ  information early stages of the collision Φ c = 44 fm Φ  modification mass shape and width M.Asakawa and C.M. Ko, Nucl. Physics A575, 732 (1994); Phys. Lett. B322, 33 (1994); C. Song, Phys. Lett. B388, 141 (1996); C.M. Ko and D.Seibert, Phys. Rev. C49, 2198 (1994); W. Smith and K.L. Haglin, Phys. Rev C57, 1449 (1998) 4/21/2019 Patricia Fachini

Motivation - II Φ  different production for hadronic and leptonic channels Nucleon-nucleon collisions  η, ω and ρ0 at high pT  perturbative QCD A+A collisions  η, ω and ρ0 at high pT  nuclear effects can modify particle production Δ++  mass and width modification in medium Vector mesons  K* and Φ  global polarization measured via spin alignment K*  time between chemical and kinetic freeze-out S. Pal et al., Nucl.Phys. A707 (2002) 525-539 RHIC Δ++ Hees and Rapp Hot Quarks04 Hees and Rapp, HotQuarks04 Z. Liang and X. Wang, Phys. Lett B629, 20 (2005) 4/21/2019 Patricia Fachini