BNL May 17, 2002 Falk Meissner, LBNL Jim Thomas for Falk Meissner Lawrence Berkeley National Laboratory The STAR Collaboration Workshop on Diffraction and Glueball Searches at RHIC Photon-Pomeron and Photon-Photon Photon-Pomeron and Photon-Photon Interactions in Interactions in Ultra-Peripheral Heavy Ion Collisions Ultra-Peripheral Heavy Ion Collisions at STAR at STAR •Exclusive Meson Production •Data Sets and Analysis •Photon-Photon Interactions •Cross Sections •Outlook 2002 Data •Summary
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Photon-Pomeron and Photon-Photon Interactions in Ultra-Peripheral Heavy Ion Collisions at STAR
Photon-Pomeron and Photon-Photon Interactions in Ultra-Peripheral Heavy Ion Collisions at STAR. Jim Thomas for Falk Meissner Lawrence Berkeley National Laboratory The STAR Collaboration Workshop on Diffraction and Glueball Searches at RHIC. Exclusive Meson Production - PowerPoint PPT Presentation
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BNL May 17, 2002 Falk Meissner, LBNL
Jim Thomas for Falk Meissner
Lawrence Berkeley National LaboratoryThe STAR Collaboration
Workshop on Diffraction and Glueball Searches at RHIC
Photon-Pomeron and Photon-Photon Interactions Photon-Pomeron and Photon-Photon Interactions in in
Ultra-Peripheral Heavy Ion CollisionsUltra-Peripheral Heavy Ion Collisions at STAR at STAR
•Exclusive Meson Production•Data Sets and Analysis•Photon-Photon Interactions•Cross Sections•Outlook 2002 Data•Summary
• Separation by ZDC signals Impact parameter tagging.• Hadronic AuAu: multiple neutrons in ZDC• UPC: Coulomb excitation GDR
single neutron emission & (1n,1n) ~ 6% of & (xn,xn)
• Compare to RHIC measurement of Coulomb Dissociation
(1n,1n) = 4% of Tot
M.Chiu et.al nucl-ex/0109018
0
UPC b>2RUPC+hadronic b~2Radditional vertex tracks
0
BNL May 17, 2002 Falk Meissner, LBNL
RapidityRapidityExtrapolationExtrapolation
• Y-Distribution differs between prod. with and without breakup (A. Balz,S. Klein,J. Nystrand,
nucl-th/0205031) • Included in MC simulation
Nucl.Breakup
STAR Data
• Acceptance is flat in pT and Mass
• Rapidity acceptance only |y|<1• Need to extrapolate• All/|y|<1 = 2.0 for nucl. breakup
Monte Carlo
BNL May 17, 2002 Falk Meissner, LBNL
Electromagnetic Electromagnetic
Interaction Interaction ->e->e++ee-- Identified e+e- Pairs• Minimum bias trigger• Calorimeter STAR in progressdE/dx for identification only at low momentum only p<0.13 GeV
• Here, background to production
• Reconstruct e+e- as if M hypothesis
• MC simulation: extrapolate M spectrum to all momenta.
e+e- Pairs are all at low p_T AuAu->Au*Au*e+e Transverse momentum pT < 2ħc/b
Physics Topics: Strong field QED Z ~ 0.6 Large cross section Z44