1. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 1 First measurement of the  - meson production with PHENIX experiment at RHIC Victor Ryabov for the PHENIX Collaboration

2. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 2  Measurement of ω-meson production in different decay channels ( ω  π 0 π + π -,   π 0 ,   e + e - ) carries information about possible modification of the media produced in HI collisions.  Measurement of hadronic decays of the ω -mesons in p+p collisions creates a baseline for the comparison to other decay modes and collision systems: Comparison ω  hadrons vs. ω  di-electrons in p+p Comparison of the same ratio in A+A  ω is an important ingredient for calculation of electron cocktails used in various PHENIX analyses.  Vector-to-Pseudoscalar meson ratio (  /  0 ) at high p T tells us about the production of q-qbar bound states.  High p T results on ω and K 0 S add to the picture of the meson R dA in d+Au interactions measured at RHIC

3. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 3  Decays under study  Experimental setup  Analysis details: Acceptances Phase space Systematic errors  Results: Spectra, cross-checks and comparisons R dA ω/ π 0 ratio Measurement of the mass peak  Summary and Outlook

4. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 4 Charge particles      DC-PC1 Momentum resolution: No pID for π + π - Neutrals particles    EMC Energy and space resolution: PHENIX acceptance : -0.35 <  < 0.35 2 x 90 o for two arms π-π- π 0   π+π+ (see poster 203 in sec.6) Run 3

5. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 5  +  -  0 decay channel:  - meson: m = 548 MeV, BR = 23.1 %  - meson: m = 783 MeV, BR = 88.8 %  0  decay channel:  - meson: m = 783 MeV, BR = 8.5 %  0  0 decay channel: K 0 S - meson: m = 498 MeV, BR = 31.1 % M inv, GeV Run 3 data

6. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 6 K 0 S  π 0 π 0   ω  π 0 π + π -   π + π - ω  π 0    Geometrical acceptance Trigger efficiency Combined PHENIX has different acceptance and trigger efficiencies for the decays under study Consistency of the results is a powerful cross check

7. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 7 GEANT assumes uniform density of the phase-space We used measured ( e.g.:PRL(1962) 325 ) density distribution profile resulting in 5%-15% correction depending on p T Correction applies to ω  π 0 π + π - while ω  π 0  is unaffected and remains a cross check. π - E kin π + E kin π 0 E kin 1.0 0.5 3.0 5.0 7.0 9.0 p T [GeV/c]

8. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 8  Calorimeter related errors: Geometrical acceptance 4-8 % Energy resolution 1-5 % Energy scale 3-23 %  Tracking related errors: DC-PC1 tracking efficiency negligible Matching cuts 2 % Momentum cuts for charged tracks negligible Run by run variation 2-3 %  Trigger related errors: ERT trigger efficiency 3-7 % Trigger efficiency and correction 10 %  Analysis uncertainties:  0 selection cuts 3-10 % Conversion correction uncertainty 3-6 % Peak extraction uncertainty 9-13 % Branching ratio uncertainties 0.8-5 % Phase space correction 2-8 %

9. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 9 First result on the ω-meson production at RHIC energy. Broad p T coverage from 2.5-9.5GeV/c Good agreement between two independent decay modes

10. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 10 First result on the ω-meson production in d+Au. Broad p T coverage from 3 GeV/c to 9 GeV/c Good agreement between to independent decay modes

11. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 11 K 0 S spectra up to p T of 6.5 GeV/c in p+p and 8.5GeV/c in d+Au Gap between K 0 S and K + K - measurement prevents direct comparison to Time-of-Flight measurements (talk by Maya Shimomura). PHENIX results are consistent with measurements of STAR in the region of overlap and go to higher p T. Provides a good cross check for analysis approach hep-ex/0501059

12. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 12 CERES-TAPS measured ω-meson production in hadronic collisions at lower p T At √31 GeV (π+Be E706) spectrum have steeper slope Instead of comparing spectra we can compare ω/π 0 ratio

13. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 13 p+p d+Au First result on the Vector/Pseudo- scalar meson ratio at RHIC at high p T Ratios are similar in p+p and d+Au and close to 1 Ratios do not change in a range of p T from 2 GeV/c to 9 GeV/c within systematic errors PYTHIA (default) tuned to LEP data at lower √s suggests slightly higher ratio

14. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 14 π0π0 ηK0SK0S φ R dA measured for  - mesons is consistent with 1 within the systematic errors Heavier mesons tend to show higher value of R dA

15. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 15 PHENIX can measure position of the centers of ω-meson mass peaks at different p T. Current (run3) measurements are limited by statistics. Possibility to measure the width of ω is under investigation In run3 the widths of the peaks is about 22 MeV at natural width of 8.5 MeV M inv, GeV 0+-0+-

16. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 16 Au+Au miss-ID  combinatorics clear  peak PHENIX can measure  - mesons in AuAu at √s NN = 200 GeV See clear signal in  0  channel at p T > 7 GeV/c Statistics of Run4 let to measure centrality dependence at high p T (poster 193, session 6)  0  Counts Half of Run4 statistics, loose cuts

17. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 17  The first measurement of the ω-meson production at RHIC in p+p and d+Au systems is shown: The spectra are measured in p T range from 2.5 to 9.5 GeV/c, Two decay modes for ω-meson give consistent results, R dA = 1.3 ± 0.2 in the range of measurement, ω/ π 0 (inclusive) = 0.9 ± 0.1 in p+p, Ratio is independent of p T within systematic errors, ω-meson mass is consistent with the PDG value, Clear peaks are seen in Au+Au data at high p T  K-meson measurement is consistent with existing results and extended to substantially higher p T.  Future plans: Run5 p+p with x15 more statistics, Run4 Au+Au with 1.5B events on tape, Run5 Cu+Cu with statistics comparable to Au+Au, Other decay modes.

18. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 18

19. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 19

20. Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 20 d+Au counts Statistics of Run3 d+Au is sufficient only to see the indication of  -meson in  e + e - channel. No comparison can be done with hadronic channel Statistics of Run4 Au+Au allows to produce estimation of the dN/dy (poster 195, session 6)