Systematic measurement Systematic measurement of light vector mesons of light vector mesons at RHIC-PHNEIX at RHIC-PHNEIX Yoshihide Nakamiya Hiroshima University, Japan (for the PHENIX Collaboration) Quark Matter 2008, Variable Energy Cyclotron Centre,Jaipur,India
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Systematic measurement of light vector mesons at RHIC-PHNEIX
Systematic measurement of light vector mesons at RHIC-PHNEIX. Yoshihide Nakamiya Hiroshima University, Japan (for the PHENIX Collaboration) Quark Matter 2008, Variable Energy Cyclotron Centre,Jaipur,India. Outline. Physics motivation PHENIX experiments at RHIC Improved Analysis - PowerPoint PPT Presentation
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Systematic measurement of light Systematic measurement of light vector mesons at RHIC-PHNEIXvector mesons at RHIC-PHNEIX
Yoshihide NakamiyaHiroshima University, Japan
(for the PHENIX Collaboration)
Quark Matter 2008, Variable Energy Cyclotron Centre,Jaipur,India
Physics BackgroundPhysics BackgroundActa Phys. Pol. B 31 (2000) 3021
At RHIC
Heavy-ion collisions at RHIC hascapability of studying a phase transition In a cross over region.Measurements from various viewpointsIs needed to reveal the property ofa partoic matter.
<Light vector meson as probe >- deconfinement(shape of thermal radiation) -> Spectral function has been changed in a deconfined partonic matter.
- chiral phase transition (chiral symmetry restoration) -> Mass modification will be expected to happen in the deconfined partonic matter. - Hydrodynamic calculation expects that duration time of a deconfined matter is about 10 fm/c. -> Short lived vector mesons are desirable as the target of measurement ( τ
QGP = 10 fm/c, τ
φ = 46 fm/c, τ
ω = 23 fm/c, τ
ρ = 1.3 fm/c)
Measurement of mass state for light & short lived mesons are suitable for the study of the partonic matter.
⇒ φ and ω mesons can be measured in PHNIX.
R. Rapp J. Phys G31 (2005) S217R. Rapp J. Phys G31 (2005) S217R. Rapp J. Phys G31 (2005) S217
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Experimental setupExperimental setup
RHIC perspective
PHENIX overview
PHENIX spectrometer<Global detector>• BBC & ZDC : Event trigger, Collision vertex, Centrality <Central arm>• Acceptance ⇒ pseud-rapidity range : |η| < 0.35 azimuthal angle : 2x90 degree(2 arms)• DC & PC : tracking, momentum• RICH & EMC : electron ID• TOF, EMC : hadron ID<Muon arm>• MuID : muon ID⇒The PHENIX spectrometers are versatile devices to measure electrons,photons as well as hadrons at the same time.
RHIC accelerator Species : Au+Au, d+Au, proton+proton, Cu+Cu Energy : √s _NN = 22.5, 62.5, 200, 500 GeV
⇒The RHIC accelerator provides various collision systems at a broad range of c.m.s energy. (200Gev is the maximum energy for ion.)
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What has been measured in PHENIX?What has been measured in PHENIX?<Measured decay channels of light vector mesons in PHENIX>
•φ mesons φ→e+e- Branching Ratio ~ 10-4
φ→K+K- Branching Ratio ~ 50 %
•ω mesons ω→e+e- Branching Ratio ~ 10-5
ω→π0γ Branching Ratio ~ 9 % ω→π0π+π- Branching Ratio ~ 90 %
<How can we know the property of light vector mesons ?>
•Line shape analysis (Mass peak and width) ⇒ Line shape modification (Mass peaks and width) may be small due to small fraction of φ&ω decay inside a deconfined matter. (τ
QGP = 10 fm/c, τ
φ = 46 fm/c, τ
ω = 23 fm/c )
•Yield analysis (Branching ratio) ⇒ The yield of mesons in case of each decay mode can induce significant change (Yiels trough e+e- compared to K+K- channels could be changed because mφ~mk).
[GeV/c^2]
Magenta:BG1+BG2+BG3
The invariant mass spectra of 3γ
ω peak
BG2 : mixing between accidental π0 candidate andevent mixed γ.
Improved analysis :Improved analysis : Background estimation for ωBackground estimation for ω→→ππ00γγDifficulty : It is difficult to estimate background shape of the invariant mass spectra in case of three-bodied decay. Methodology : We assume the background shape consists of 3 components shown below and reproduced background shape by their linear combination.
BG3 : K0 contribution
BG1 : mixing between π0 candidate and event mixed γ.
(1) K+ and K- is identified by time of flight (TOF and EMCal)(2) Invariant mass is reconstructed
(1) Invariant mass is reconstructed(2) φ meson is identifiedby mass peak.
φ candidates
K+ K-h+ h-
φ candidates
K+ or K- h+ or h-
φ candidates
(1) K+ or K- is identified by time of flight (TOF and EMCal)(2) Invariant mass is Reconstructed(3) φ meson is identifiedby mass peak.
<Feature of analysis>No PID analysis : φ measurement is extended high pT regionSingle leg analysis : φ measurement is extended low pT region
Result : Result :
Yield Analysis Yield Analysis
mT spectra (phi -> e+e-)
Binary scaling
Npart scaling
-The left-top figure is mT spectra-The right-top figure is mT spectra scaled by Ncol-The right-bottom figure is mT spectra scaled by Npart
mT spectra (phi -> K+K-) : comparison between with PID, no PID and legPID
-The slope of mT spectrum is consistent between PID, single leg PID and no PIDanalysis in overlap region.-Measurable mT region is extended by no PID and one leg PID analysis.
Au+Au
p+p and d+Au
mT spectra (phi -> K+K-)
Binary scaling
Npart scaling
The left-top figure is mT spectraThe right-top figure is mT spectra scaled by NcolThe right-bottom figure is mT spectra scaled by Npart
The invariant dN/dy and temerature for phi mesons
mT spectra (omega -> e+e-)
Binary scaling
Npart scaling
The left-top figure is pT spectraThe right-top figure is pT spectra scaled by NcolThe right-bottom figure is pT spectra scaled by Npart
mT spectra (omega -> pi0 gamma, pi0pi+pi-)
Binary scaling
Npart scaling
The left-top figure is pT spectraThe right-top figure is pT spectra scaled by NcolThe right-bottom figure is pT spectra scaled by Npart
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Result : Result :
Line Shape Analysis Line Shape Analysis
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Line shape for φLine shape for φ →K→K++KK- - at AuAu 200GeV at AuAu 200GeVPRC 72 014903 (2007)
• Mass centroid
⇒ Mass centroid at all centralities are consistent with the PDG value within errors.
• Mass width
⇒There is no convincing evidence of φ width variation as a function of the number of participant nucleons.
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Line shape for ω mesons at dAu, pp 200 GeVLine shape for ω mesons at dAu, pp 200 GeVPRC 75 051902 (2007)
<Line shape>
ω mass measured in the π0π+π- decay as a function of pT in d+Au and p+p 200 GeVare consistent with the PDG value within errors.
SummarySummarySystematic Measurement of light vector mesons are powerful to study the property of the partonic matter.The phenix spectrometers are versatile devices to measure electrons, photons as well as hadrons at the same time.
<Line Shape Analysis > φ mesons : There is no convincing evidence of mass and width as a function of number of participants nucleons
ω mesons : Mass centroid and width is consitstent to the PDG value.<Yield Analysis>
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Thank you for inviting me to Quark Matter 2008 !I return thanks to all pariticipants and Collaborators!!