Transcript Slide 1
Overview of Resonance Production P. Fachini Brookhaven National Laboratory 7/18/2015 Patricia Fachini 1 Motivation Measured Resonances Masses and Widths Spectra and Yields Ratios Outlook 7/18/2015 Patricia Fachini 2 Motivation 7/18/2015 Patricia Fachini 3 Motivation - I • Medium modification of mass and/or width Chiral Symmetry Restoration, Collision Broadening and/or Phase Space? 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 + - π- - π- ρ0 π+ + ρ0 π- ρ0 ρ0 π+ ρ0 + ρ0 c = 1.3 fm π+ • ρ0 leptonic decay channel probes all stages of the collision • ρ0 hadronic decay channel probes late stages of the collision 7/18/2015 Patricia Fachini 4 Motivation - II • Φ information early stages of the collision Φ c = 44 fm • Φ modification mass shape and width • Φ different production for hadronic and leptonic channels S. Pal et al., Nucl.Phys. A707 (2002) 525-539 • Nucleon-nucleon collisions η, ω and ρ0 at high pT perturbative QCD • A+A collisions η, ω and ρ0 at RHIC high pT nuclear effects can modify particle production Δ++ • Δ++ mass and width modification in medium Hees and Rapp Hot Quarks04 Hees and Rapp, HotQuarks04 • K* time between chemical and kinetic freeze-out 7/18/2015 Patricia Fachini 5 Motivation - III π K* K K* measured π K* π K* K K* lost π K* K K Chemical freeze-out 7/18/2015 Kinetic freeze-out π K K* measured • 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 Patricia Fachini 6 Measured Resonances 7/18/2015 Patricia Fachini 7 Resonance Production 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 + π- π0 η(547) π 7/18/2015 B.R. 0.23 Patricia Fachini c = 167225 fm Life Time ρ0(770) π+ π- 8 Δ++(1232) p π+ B.R. ~1 STAR Preliminary STAR Preliminary √sNN = 200 GeV 7/18/2015 c = 1.6 fm Patricia Fachini √sNN = 200 GeV 9 K*(892) π K B.R. ~1 c = 4 fm STAR Preliminary STAR Preliminary √sNN = 200 GeV √sNN = 200 GeV √sNN = 62 GeV STAR Preliminary 7/18/2015 Patricia Fachini 10 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 STAR Preliminary Λ* √sNN = 200 GeV Minimum Bias d+Au STAR Preliminary 7/18/2015 Patricia Fachini 11 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 7/18/2015 Patricia Fachini PHENIX 12 Φ(1020) K+ KΦ(1020) e+e- B.R. 0.49 c = 44 fm B.R. 0.000296 c = 44 fm d+Au PHENIX Φ K+ KSTAR Preliminary √sNN = 200 GeV Au+Au 7/18/2015 Patricia Fachini Φ e+e- PHENIX √sNN = 200 GeV 13 Sub-Threshold Measurements Σ*± + ± K(892) (< 800 MeV) Σ(1385) (< 400 MeV) Al+Al 1.9 AGeV FOPI 7/18/2015 Patricia Fachini K*0 K+ + Al+Al 1.9 AGeV FOPI 14 π+π- Invariant Mass Distribution from Monte Carlo STAR Preliminary • HIJING events with a realistic simulation of detector response ρ0(770) π+ π- sNN = 200 GeV K0S π+ πω(782) (π+ π-) π0 and π+ π- ρ0 K0S ω η + η’ η (π+ π-) π0 and (π+ π-) η’ (π+ π-) η and (π+ π-) ρ0 K*(892)0 K π with K misidentified as π K*0 + K*0 misidentified • Use ω and K*0 shape from HIJING to fit the data • K*0 signal is fixed using STAR measurement 7/18/2015 Patricia Fachini 15 ρ0(770) π+ π- B.R. ~1 STAR Preliminary STAR Preliminary 20-40% dAu 0.6 ≤ pT < 0.8 GeV/c 40-100% 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 7/18/2015 c = 1.3 fm √sNN = 200 GeV Patricia Fachini 16 Masses and Widths 7/18/2015 Patricia Fachini 17 K* Mass and Width STAR Preliminary MC PDG K*0 PDG K*± PDG • 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 STAR Preliminary 7/18/2015 Patricia Fachini 18 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 7/18/2015 Patricia Fachini 19 ω Mass PDG fit PDG fit 7/18/2015 Patricia Fachini • No mass shift observed in both minimum bias p+p and d+Au at √sNN = 200 GeV • Statistical error shown 20 ρ0 Mass 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 7/18/2015 Patricia Fachini 21 ρ0 Hadronic channel STAR (RHIC) STAR • Probing late of the collisions • Mass shift ~70 MeV 7/18/2015 Patricia Fachini 22 ρ0 Dimuons channel NA60 (SPS) Hees and Rapp, hep-ph/0603084 • Probing all stages of the collisions • Mass broadening 7/18/2015 Patricia Fachini 23 Hees and Rapp, hep-ph/0603084 Mass Shift in A+A 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! 7/18/2015 Patricia Fachini 24 0 ρ 7/18/2015 Mass at High-PT Patricia Fachini 25 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 7/18/2015 Patricia Fachini 26 ρ0 Mass at High pT STAR Preliminary Background p+p 200GeV STAR Preliminary Central Au+Au 200GeV • 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! STAR Preliminary Minimum Bias Au+Au 200GeV 7/18/2015 Patricia Fachini Phys. Rev. Lett. 92 (2004) 092301 27 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 P. Fachini et.al., J.Phys.G33:431-440,2007 – Medium modifications R. Rapp, Nucl.Phys. A725, 254 (2003), E.V. Shuryak and G.E. Brown, Nucl. Phys. A 717 (2003) 322 – Bose-Einstein correlations 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 • ρ0 at high-pT No apparent mass shift! 7/18/2015 Patricia Fachini 28 Spectra 7/18/2015 Patricia Fachini 29 Spectra-I STAR Preliminary STAR Preliminary 7/18/2015 Patricia Fachini 30 Spectra-II K*0 Au+Au √sNN = 62 GeV STAR Preliminary STAR Preliminary √sNN = 200 GeV 7/18/2015 Patricia Fachini 31 Spectra-III Φ K+ K- STAR Preliminary STAR Preliminary STAR Preliminary 7/18/2015 Patricia Fachini 32 Spectra-IV Au+Au 62 GeV 7/18/2015 Patricia Fachini 33 Φ Production K+K- and e+e- e+e- K+K- • The leptonic channel yield is a little higher than hadronic channel • More accurate measurement is required to confirm whether there is branch ratio modification 7/18/2015 Patricia Fachini 34 Φ Production K+KJ. Rafelski et al.,Phys.Rev. C72 (2005) 024905 STAR PHENIX STAR + PHENIX • Φ production there is a factor of ~2 difference between PHENIX and STAR! • BRAHMS measurement agrees with STAR at midrapidity √sNN = 200 GeV 7/18/2015 Patricia Fachini 35 Ratios 7/18/2015 Patricia Fachini 36 Φ Ratios 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 7/18/2015 Patricia Fachini 37 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 7/18/2015 Patricia Fachini 38 Time between freeze-outs • If rescattering is the dominant process, - ct N(Δt) = N0 e - Δt c e = K*0 K- Au+Au 0.23 = 0.35 K*0 K- p+p • 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 7/18/2015 Patricia Fachini 39 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 7/18/2015 Patricia Fachini 40 η, ω and ρ0 Ratios η STAR Preliminary • • 7/18/2015 √sNN = 200 GeV ρ0 π+ π- • • 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 Patricia Fachini 41 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 7/18/2015 Patricia Fachini 42 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 7/18/2015 Patricia Fachini 43 Backup Slides 7/18/2015 Patricia Fachini 44 Φ Mass and Width STAR Preliminary PDG STAR Preliminary PDG 7/18/2015 Patricia Fachini • 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 45 Elliptic Flow - I • KS0 and Λ v2 scale number constituent quarks v2/n • Resonance v2 C. Nonaka et al., Phys.Rev. C69 (2004) 031902 – πK K* n = 4 – qq K* n = 2 • Significant K*0 v2 measured • Fitting K*0 v2 to X. Dong et al., Phys.Lett. B597 (2004) 328 an v2(pT,n) = - dn 1 + exp[-(p /n – b)/c] Minimum Bias Au+Au 200GeV T a, b, c, and d constants extracted using KS0 and Λ v2 • K*0 v2 n= 2.0 ± 0.3 STAR Preliminary 7/18/2015 Patricia Fachini 46 Elliptic Flow - II Au+Au 200GeV 7/18/2015 • 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 Patricia Fachini 47 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 7/18/2015 Patricia Fachini 48 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 7/18/2015 Patricia Fachini 49 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) 7/18/2015 Patricia Fachini 50 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 7/18/2015 Patricia Fachini 51 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! 7/18/2015 Patricia Fachini 52 ρ0-meson Measured in p+p NA27 π+πpT > 0 xF > 0 xF = pLongitudinal pTotal • √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 PS = BG BG = Background PS = Phase Space Signal π+π- distribution after background subtraction Background exponential function 7/18/2015 Signal Same event distribution π+π- Patricia Fachini 53 ρ0-meson Measured in p+p NA27 762.6 MeV/c2 775.9 MeV/c2 “scanned version” 7/18/2015 Patricia Fachini • 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 54 ρ0-meson Measured in p+p NA27 BW(M) = Γ(M) (M2 – Mρ2)2 + Mρ2 Γ(M)2 Γ(M) = Γρ M2 – 2 4mπ 3 2 Mρ2 – 4mπ2 Mρ M Fitting to a p-wave BW function M = 747.6 ± 2.0 MeV 7/18/2015 Patricia Fachini 55 ρ0-meson Measured in e+e- LEP √s = 90 GeV Jetset 7.3 + ALEPH Data ρ0 Jetset 7.2 ● OPAL Data ρ0 7/18/2015 • OPAL ρ0 mass shifted by ~70 MeV/c2 at low xp and no shift at high xp (xp ~1) E(meson) xp = E(beam) • 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 Patricia Fachini 56 Phase Space M Phase Space = M2 + pT2 • • - M2 + pT2 e T π+ ρ0 π+ π- 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 BW(M) = Γ(M) (M2 – Mρ2)2 + Mρ2 Γ(M)2 Γ(M) = Γρ M2 – 3 4mπ2 2 Mρ2 – 4mπ2 Mρ M 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. 7/18/2015 Patricia Fachini 57 Transport Model - UrQMD Au+Au b ≤ 3 fm 0 1.2 ≤ pT < 1.4 GeV/c √sNN = 200 GeV |y| ≤ 0.5 Au+Au b ≤ 3 fm ρ0 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 Г = 150 MeV – Mρ = 769 MeV/c2 input 7/18/2015 Patricia Fachini 58 Nuclear Modification Factor pp 2 AA inel d N / dpT dy RAA ( pT ) 2 NN N binary d / dpT dy If no “effects”: R < 1 in regime of soft physics R = 1 at high-pt where hard scattering dominates 2 central N peripheral d N / dpT dy binary RCP ( pT ) central 2 peripheral N binary d N / dpT dy 7/18/2015 Patricia Fachini 59 Nuclear Modification Factor 7/18/2015 Patricia Fachini 60 Elliptic Flow v2 • Coordinate-space-anisotropy Momentum-space-anisotropy y x y 2 x 2 2 2 y x v 2 cos2 , tan ( 1 py px ) • Nuclei Non-central Collisions Hot System Elliptic Shape 7/18/2015 Patricia Fachini 61 Quark or Hadron Combination v2(pT,n) = 7/18/2015 Number of constituent quarks an 1 + exp[-(pT/n – b)/c] - dn Patricia Fachini Constants extracted by fitting the K0s and Λ v2 62 K*0 Mass and Width pp and Au+Au √sNN = 200 GeV |y|< 0.5 STAR Preliminary Central Au+Au 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 7/18/2015 Patricia Fachini 63 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 7/18/2015 Patricia Fachini 64 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 7/18/2015 Patricia Fachini 65 K* Number of Participants STAR Preliminary K* STAR Preliminary • K* production seems to scale with Npart (size of the collision system) for all systems 7/18/2015 Patricia Fachini 66 Φ Ratios STAR Preliminary STAR Preliminary 7/18/2015 • 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 Patricia Fachini 67 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 7/18/2015 Patricia Fachini 68 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! 00( frag ) 00( frag ) 7/18/2015 1 Pq2 • K*0 (0.8<pT<5.0 GeV/c) ρ00 = 0.33 ± 0.04 ± 0.12 3 Pq2 1 Pq2 3 Pq2 00( rec ) 1 Pq2 3 Pq2 Patricia Fachini • Φ (0.4<pT<5.0 GeV/c) ρ00 = 0.34 ± 0.02 ± 0.03 69 Motivation - I • Medium modification of mass and/or width Chiral Symmetry Restoration, Collision Broadening and/or Phase Space? 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 + - π- - π- ρ0 π+ + ρ0 π- ρ0 ρ0 π+ ρ0 + ρ0 c = 1.3 fm π+ • ρ0 leptonic decay channel probes all stages of the collision • ρ0 hadronic decay channel probes late stages of the collision • Φ information early stages of the collision • Φ modification mass shape and width Φ c = 44 fm 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) 7/18/2015 Patricia Fachini 70 Motivation - II • Φ different production for hadronic and leptonic channels S. Pal et al., Nucl.Phys. A707 (2002) 525-539 • 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 Hees and Rapp, HotQuarks04 • Vector mesons K* and Φ global polarization measured via spin alignment RHIC Δ++ Hees and Rapp Hot Quarks04 Z. Liang and X. Wang, Phys. Lett B629, 20 (2005) • K* time between chemical and kinetic freeze-out 7/18/2015 Patricia Fachini 71