1 / 19

Akihisa Takahara CNS University of Tokyo,RIKEN For THE PHENIX collaboration

Measurement of the Ultra-peripheral J/psi Cross Section in Au+Au  Collisions with the PHENIX Detector. Akihisa Takahara CNS University of Tokyo,RIKEN For THE PHENIX collaboration. Ultra Peripheral Collision.

kelii
Download Presentation

Akihisa Takahara CNS University of Tokyo,RIKEN For THE PHENIX collaboration

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Measurement of the Ultra-peripheral J/psi Cross Section in Au+Au  Collisions with the PHENIX Detector Akihisa Takahara CNS University of Tokyo,RIKEN For THE PHENIX collaboration ATHIC 2010

  2. Ultra Peripheral Collision relativistic charged particle generates strong electromagnetic field intransverse plane ~ large gamma flux b>2R γ RHIC max. photon energies(EPA): 3 GeV~γ/R γ • Characteristics of UPC • →strong  - source • (X) Z2~ 6·103 • ()  Z4~ 4·107 • @Au(79) • No Nuclear overlap • →　low background We can study γγ,γA ,γp interaction without hadronic interaction ATHIC 2010

  3. Motivation to study J/psi in UPC We can see Q2≒2.5, x≒0.01 region by UPC J/psi cross section measurement at RHIC Phys.Rev.C78:044904,2008 Large Uncertainty UPC is good probe to study low x PDF ATHIC 2010

  4. Previous result RHIC average photon energy corresponds to 24GeV PHENIX 2004 • HERA -ZEUS measured γp-> J/psi photo production cross section. • However , In general σ(A)≠σ(p). • PHENIX measured UPC J/psi cross section at 2004. • The result includes all theoretical predictions within 1sigma • Motivation • To improve error to get enough quality to find fittest theoretical predicition -> • 2007 run has 4times statistics ATHIC 2010

  5. RUN7 central UPC trigger n Coherent UPC: γ+γ→ e+e-, γ+A→ X+J/ψ: lower pt<0.3GeV Incoherent UPC: γ+n → n+J/ψ : wider pt e+ e- Coherent UPC 50-60% ee pairs from UPC J/psi is measured by tagging forward neutron emission UPC trigger BBC detect no charge EMCal energy threshold 1.0GeV 1 or 2 ZDC detects neutron

  6. Background source of UPC J/psi cross section measurement pT^2distribution theoretical • UPC • Incoherent UPC(γ+n→n+J/Ψ)：signal • Coherent UPC • γAu→X+J/Ψ:signal • γγ→ee:background • γAu→jet A: • RHIC energy is too lowfor this process Coherent: low pt peak Incoherent: wider pt distribution (Incoherent + neutron tagged : Yellow shadow ) We will see coherent and incoherent J/psi and γγ->ee background. Other physics and non physics background are rejected by UPC trigger. ATHIC 2010

  7. characteristics of continuum and coherent J/psi STARLIGHT model with GEANT simulation • γγ→ee • Low pt peak • Exp fitting • (~exp(-2.1mass)) pT<0.8 Same simulation for coherent UPC J/psi • J/psi • Coherent • Low pt peak • Gaussian fitting Likesign unlikesign ATHIC 2010

  8. Invariant mass • No likesign pair • 43 ee pairs at mee>2GeV • Clear J/psi peak • Clear γγ→ee(Continumm) • Of course we have γγ→ee pair in J/psi region. • To estimate N(J/psi) • Fitting function should be • Gaussian(J/psi) +continuum curve • Continuum shape was estimated by • STARLIGHT simulation with PHENIX detectors and trigger efficiency for electrons NJ/psi:18.75+-5.05(sta)+-0.25(sys) ATHIC 2010

  9. Pair pt • Low J/psi pTpeak • suggest s • coherent UPC • Some higher pT • event s suggests • Incoherent UPC Red cross symbols correspond to this region Simulated data has 1000times larger Statistics. However their Max pT <0.8 At least, their incoherent events We can seeUPC coherent (γAu) &incoherent (γn) J/Ψ production ATHIC 2010

  10. Cross section compared to theoretical calculation Some coherent prediction looks enough to explain the result. However measured pT spectra suggest both coherent and incoherent J/psi production J. Nystrand, Nucl. Phys. A 752(2005)470c; A.J. Baltz, S.R. Klein, J. Nystrand, PRL 89(2002)012301; S.R. Klein, J. Nystrand, Phys. Rev. C 60(1999)014903 M. Strikman, M. Tverskoy and M. Zhalov, Phys. Lett. B 626 72 (2005) V. P. Goncalves and M. V. T. Machado, arXiv:0706.2810 (2007). Yu. P. Ivanov, B. Z. Kopeliovich and I. Schmidt, arXiv:0706.1532 (2007). Run7:54.1±14.6 +10.3/-9.7μb Run4(published data):76±31(stat)±11(sys) μb Run 4& 7 combined 60.8±13.7(stat)+10.5−10.1(sys) μb. ATHIC 2010

  11. Cross section compared to theoreticalcalculations(coh +incoh) Run7:54.1±14.6 +10.3/-9.7μb Run4(published data):76±31(stat)±11(sys) μb • Run7 result is lower than run4 • Relatively , half statistical error • Statistical error is close enough • systematical error . At 2010 run analysis, • we need to improve systematical error. ATHIC 2010

  12. 2004-2007 combined result Run 4& 7 combined 60.8±13.7(stat)+10.5−10.1(sys) μb. • Compared to statistical error • Strikman: • Color dipole model • Impluse or glauber approximation • +0.47- -0.62sigma • Kopeliovich: • Color dipole model+ • gluon saturation effects • KST or GBW parameterization • +1.78- +1.05sigma 1.2<|y|< 2.4 covered by PHENIX muon arm, and we have taken data at RUN 10 &7. Muon UPC will be analyzed Strikman looks better ATHIC 2010

  13. Comparison with HERA data HERA data; Please note this calculation is just a trial. We don’t have enough statistic to separate coherent and incoherent Alpha=1Hard probe scaling Alpha=2/3 Soft probe scaling ATHIC 2010

  14. Summary and outlook Summary • 2007 neutron tagged UPC J/psi cross section is 54.1±14.6 +10.3/-9.7μb • Combined cross section is 60.8±13.7(stat)+10.5−10.1(sys) μb. • Lower statistical error . Now it equal to systematic error. • Good agreement with theoretical calculations. Especially, Strikman result. • pT distribution shows both coherent and incoherent process. Outlook • 2010 forward UPC(μμ) will be analyzed • future eRHIC & LHC programs. ATHIC 2010

  15. Back up ATHIC 2010

  16. The experimental signaturesand the analysis • Analysis cut • Vertex cut:|Zvertex|<30cm • ZDC north || south>30GeV • Number of electron candidate • tracks==2 • No real track other than • 2 electron candidate tracks. • BBC veto(offline) • Electron(positron) id • RICH associated • Emcal matching • UPC signatures • Only e+ e- pair in central arm • At least 1 neutron ATHIC 2010

  17. UPC measurement in PHENIX(at 2007) n e+ e- Coherent UPC 50-60% • UPC trigger • No MB trigger:BBC VETO • 1 or 2 neutron :ZDC • Emcal (>1GeV) • ee pair • DC and PC, tracking • RICH and Emcal, e id ATHIC 2010

  18. RHIC and PHENIX • Relativistic Heavy Ion Collider, • at the Brookhaven National • Laboratory (NY,USA) • About 4km circumference • (Second largest of Ion collider) • Center of mass energy per nucleons • ~200GeV(AuAu),~500GeV(pp) • AuAu, pp, d+Au,CuCu • 2007-RUN • AuAu • “200GeV • Integrated Luminosity is4 times larger than last 2004 AuAu run ATHIC 2010

  19. ATHIC 2010

More Related