Dipali Pal for the PHENIX collaboration Vanderbilt University

1. Nuclear modification and elliptic flow measurements for f mesons at sNN = 200 GeV d+Au and Au+Au collisions by PHENIX Dipali Pal for the PHENIX collaboration Vanderbilt University

2. Outline • Motivation • f meson spectra at different centralities • Nuclear modification factors for the f mesons • Elliptic flow of the f mesons • Summary and outlook

3. Motivation: Baryon/meson anomaly Au + Au @ √sNN = 200 GeV Baryon/meson puzzle  Scaling properties of yields  Different suppression  Elliptic flow Quark number scaling of the elliptic flow parameter v2 “Mass effect” or “baryon/meson effect”? PHENIX fmeson has a mass similar to a proton. • Appropriate probe to address the baryon/meson puzzle.

4. f  K+K- measurement in PHENIX Number of events analyzed: Spectra: 409 M for TOF 170M for PbSc Elliptic flow: 800 M p/K separation in TOF: 0.3 < p (GeV/c) < 2.5 p/K separation in EMCal: 0.3 < p(GeV/c) < 1.0 K+K- pairing topology Four independent K+K- pairing TOF – TOF (9% of the total f’s) TOF – PbSc (East) (27% of the total f’s) PbSc(East) – PbSc(East) (9% of the total f’s) PbSc(West) – PbSc(West) (55% of the total f’s)  Allows a self-consistent measurement on f.

5. Combinatorial background (CB) is estimated by event mixing. • Normalized to 2(N++.N--), N++ and N– are like sign measured yields. • Signal = Same event - CB • Experimental mass resolution ~ 1 MeV/c2 • Better than f mass width. Subtracted spectrum is fitted with Relativistic Breit Wigner convolved with Gaussian f mass resolution. Centroid and width are consistent with PDG. Number of f mesons analyzedSpectra: ~ 44K Elliptic flow :~ 180K f meson reconstruction technique <m> = 1.01891 ± 0.00003 (stat) ± 0.00085 (syst) GeV/c2 G = 4.22 ± 0.09 (stat) ± 0.506 (syst) MeV/c2 Subtracted spectrum

6. Spectra: raw yields to absolutely normalized spectra • Raw yield extraction  Nf (rec) (mT) = Same event (mT) – CB(mT) Yield is extracted by integrating the subtracted mass spectrum over a fixed mass window of ± 5 MeV with respect to the centroid.  Optimized signal and S/B ratio. • Corrections • Acceptance: K+K- pair MC through PHENIX simulation chain. • Efficiency: time (experimental run) dependent variations. • Occupancy dependent corrections: Embedding simulated fK+K- pairs into the real data.

7. Minimum-bias spectra • Excellent agreement between the subsystems • Understanding of the systematics. • Run4 result is consistent with Run2.

8. f meson spectra at different centralities Talk by A. Kozlov [6(b)] Poster by D. Pal (158) Centrality dN/dy T (MeV) MB 1.08 ± 0.04 ± 0.20 388 ± 5 ± 27 0-10% 3.80 ± 0.30 ± 0.72 372 ± 11 ± 26 10-20% 2.32 ± 0.16 ± 0.44 394 ± 10 ± 27 20 – 30% 1.62 ± 0.11 ± 0.31 397 ± 10 ± 28 30 – 40% 0.95 ± 0.07 ± 0.18 401 ± 10 ± 28 40 – 50% 0.75 ± 0.04 ± 0.13 377 ± 8 ± 26 50 – 60% 0.35 ± 0.03 ± 0.06 392 ± 12 ± 27 60 – 90% 0.11 ± 0.01 ± 0.02 348 ± 11 ± 24 Au + Au @ 200 GeV pp 0.0074 ± 0.0007 ± 0.0020 391 ± 25 ± 50

9. Scaling of protons and f spectra Ncoll scaled f spectra vs pT compared to protons • Radial Flow at low-pT • At intermediate pT, (anti)protons scale with Ncoll • No Ncoll scaling for f • Baryon/meson effect? Or mass effect? Quantify nuclear effects by Central-to-peripheral ratios (Rcp) and ratio of Au-Au central to pp yields (RAA).

10. Nuclear modification factors, RAA Two extreme centrality classes show Completely different scales of suppression. Mesons (f and p0) in Au+Au 0 – 10% (most central) are suppressed to the same extent. They are least (or almost not) suppressed in 60-90% (most peripheral) Protons are not suppressed anywhere.  Baryons and mesons show a clear difference. Two extreme centrality classes show completely different scales of suppression. Mesons (f and p0) in Au+Au 0 – 10% (most central) are suppressed to the same extent. They are least (or almost not) suppressed in 60-90% (most peripheral) Suppression of mesons increases from peripheral to central. Protons are not suppressed anywhere.  Baryons and mesons show a clear difference. Suppression of the mesons decreases from central to peripheral. What about other centralities?

11. Nuclear modification factor, Rcp Au + Au @ √sNN = 200 GeV • Au + Au collisions show suppressions • for mesons(f and p0) and no suppression for the protons and L’s. • d+Au collisions (cold nuclear matter) shows no suppression for baryons or mesons. • The anomalous meson suppression is a property of the hot and dense matter. d + Au @ √sNN = 200 GeV Poster by D. Pal (158), D. Mukhopadhyay (154)

12. Elliptic Flow of baryons and mesons At low pT hydro works remarkably well Above ~ 2 GeV/c : a split between mesons and baryons Universal behavior in flow per quark: expected from recombination Need to measure v2 of f

13. v2 measurement in PHENIX • Event reaction plane is determined by beam beam counter -- BBC South and BBC north Reaction plane Extraction of uncorrected v2 from azimuthal distribution Reaction plane resolution correction factor 1/D. v2 = v2(obs).1/D 100 – centrality(%) 100 – centrality(%)  Peripheral Central   Peripheral Central  • Reaction plane resolution: • D = sqrt(2 <cos2(2(BBCS)-2(BBCN))>)

14. 2.0 ≤pT (GeV/c) < 3.0 1.0 < pT (GeV/c) < 1.5 1.5 ≤pT (GeV/c) < 2.0 v2(obs) = 0.0198 +/- 0.0071 v2(obs) = 0.0250 +/- 0.0137 v2(obs) = 0.0338 +/- 0.0091 Minimum bias Minimum bias Minimum bias v2 extraction of f Azimuthal distribution of f mesons Fitted with the function: dN/d(f-Y2)=A [1+2v2(obs)cos2(f-Y)] The p1 parameter in the figure is the uncorrected v2. v2(obs) v2 = R.P. Resolution correction

15. v2 vs pT Minimum bias PHENIX Preliminary Non-zero v2 observed for f mesons Statistically, it is consistent with other hadrons. With present error bar, the quark number-scaled f meson v2 is consistent with other hadrons. Talk by H. Masui, Poster by A. Taranenko (identified hadron v2)

16. Summary • PHENIX has measured f mesons in K+K- decay channel with its full central arm. fK+K- spectra at seven centrality bins have been measured within 1.2 < mT (GeV/c2) < 4.4. • Nuclear modification factors, Rcp and RAA in Au-Au collisionsexhibits dramatic suppression of f’s like other mesons. • Rcp in d-Au clearly demonstrate absence of any suppression for the f mesons. • v2 of f has been measured for the first time. It is non-zero for intermediate pT. v2 of f scaled with number of quark follows universal quark number scaling within statistical errors.

17. Outlook Considerable improvements expected over the next few months - A factor of 4 increase in statistics for spectra analysis: finer pT bins and a wider range - Measurement of v2 as a function of centrality - Fine tuning of the cuts and additional statistics for elliptic flow analysis may enable us to increase statistical significance of the v2 signal.

18. Backup slides

19. v2 analysis methods • Method 1: dN/d(f-Y2) = A(1+2v2(obs)cos2(f – Y2)) -- Fit azimuthal distribution of f with this function with v2 as a fitting parameter. • Method 2: v2 (obs) = <cos2(f-Y2)> for the f mesons. Methods 1 and 2 are mathematically equivalent. • Method 3: Mesure v2 from the azimuthal distributions of the same event and CB and then extract uncorrected v2 of f as: v2(obs) = [NS+B v2(S+B) – NB v2(B)]/NS S+B = Signal + CB v2 = v2(obs)/D • = Reaction plane resolution = 1/sqrt(2 <cos2(Y2(BBCS) – Y2(BBCN))>) Three methods have extracted the same v2 value for Phi mesons. Method 1 has been applied to the full statistics of the data.

20. fKK in pp collisions: Comparison with STAR