Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 1

First measurement of the

First measurement of the

- meson production with

- meson production with

PHENIX experiment at RHIC

PHENIX experiment at RHICV

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Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 2

Measurement of ω-meson production in different decay channels (ωπ0π+π-, π0, 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 ωhadrons vs. ωdi-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 pT tells us about the production of q-qbar bound states.

High pT results on ω and K0S add to the picture of the

meson RdA in d+Au interactions measured at RHIC

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 RdA

ω/π0 ratio Measurement of the mass peak

Summary and Outlook

Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 4

Charge particles DC-PC1Momentum resolution:

No pID for π+π-

Neutrals particles EMCEnergy and space resolution:

%7.0%1.1 TT

T ppp

%,3%1.8 EE

E

ppL

El z 7.5

55.1PHENIX acceptance : -0.35 < < 0.35

2 x 90o for two arms

π-

π0

π+

(see poster 203 in sec.6)

Run 3

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:K0

S - meson: m = 498 MeV, BR = 31.1 %

Minv, GeV

Minv, GeV

Minv, GeV

Run 3 data

Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 6

K0Sπ0π0 ωπ0π+π-π+π-ωπ0

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

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 pT

Correction applies to ωπ0π+π- while

ωπ0 is unaffected and remains a cross check.

π- E kin π + E

kin

π0 Ekin

1.0

0.53.0 5.0 7.0 9.0 pT [GeV/c]

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 negligibleMatching 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 %

Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 9

First result on the ω-meson production at RHIC energy.

Broad pT coverage from 2.5-9.5GeV/c

Good agreement between two independent decay modes

Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 10

First result on the ω-meson production in d+Au.

Broad pT coverage from 3 GeV/c to 9 GeV/c

Good agreement between to independent decay modes

Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 11

K0S spectra up to pT of 6.5 GeV/c in p+p and 8.5GeV/c in d+Au

Gap between K0S 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 pT. Provides a good cross check for analysis approach

hep-ex/0501059

Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 12

CERES-TAPS measured ω-meson production in hadronic collisions at lower pT

At √31 GeV (π+Be E706) spectrum have steeper slope

Instead of comparing spectra we can compare ω/π0 ratio

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 pT

Ratios are similar in p+p and d+Au and close to 1

Ratios do not change in a range of pT from 2 GeV/c to 9 GeV/c within systematic errors

PYTHIA (default) tuned to LEP data at lower √s suggests slightly higher ratio

Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 14

π0 η K0S φ

RdA measured for - mesons is consistent with 1 within the systematic errors

Heavier mesons tend to show higher value of RdA

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 pT. 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

Minv, GeV

0+-

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 √sNN = 200 GeV

See clear signal in 0 channel at pT > 7 GeV/c

Statistics of Run4 let to measure centrality dependence at high pT

(poster 193, session 6)

0

Co

un

ts

Half of Run4 statistics, loose cuts

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 pT range from 2.5 to 9.5 GeV/c,

Two decay modes for ω-meson give consistent results, RdA = 1.3 ± 0.2 in the range of measurement, ω/π0 (inclusive) = 0.9 ± 0.1 in p+p, Ratio is independent of pT within systematic errors, ω-meson mass is consistent with the PDG value, Clear peaks are seen in Au+Au data at high pT

K-meson measurement is consistent with existing results and extended to substantially higher pT.

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.

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

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

Victor Ryabov (PNPI) for the PHENIX Collaboration QM2005 Budapest Aug,06,2005 20

d+Au

cou

nt

s

cou

nt

s

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)