W. Park USC Physics Seminar 1
Recent ATLAS results
Woochun Park@ USC Physics Seminar
April 13, 2011
• The ATLAS detector• Heavy Flavor Physics at ATLAS
• Observation of Charmonium, Upsilon & Charm Mesons• Inclusive differential cross-section of J/y production and Charm
Mesons.• Measurement of the fraction of non-prompt J/y decays & non-
prompt cross sections• Exclusive B-meson decays.
• Higgs Search at ATLAS (not today) • Summary and Outlook
April 13, 2011
W. Park USC Physics Seminar 3
The ATLAS Muon Spectrometer
• Great stand-alone performance thanks to air core toroidal magnet field (0.3 – 1.2T)
• Designed for high pt muon sensitive to new physics.
• Fast Trigger Chambers– RPC (Resistive Plate Chambers)– TGC (Thin Gap Chambers)
• High-precision tracking chambers– MDT (Monitored Drift Tube Chambers)– CSC (Cathode Strip Chambers) 2.0 < |
h| < 2.7
• Crucial measurement by CSC before toroidal field and materials. • High counting rate area near the
beam axis ( > 200Hz/cm2)• Excellent track resolution ~60mm.• Good two track resolution• Good time resolution ~7ns
• 3 planes of trigger and precision chambers individuallyo Barrel: sagitta measuremento Endcap: point-angle measurement
MDT
TGC
CSC
RPC
April 13, 2011
W. Park USC Physics Seminar 7
Observation of ccJ (1P) • Measurement of the cc cross-section in 7TeV pp collision is interesting
topic being actively worked by many theorists. Theoretical prediction of the cc production cross-sections is difficult due to P-wave divergences in the theory.
• One of the significant uncertainty of J/y cross-section measurement is cc
contribution through g J/ . y Measurement of cc cross-section will benefic J/y cross-section measurement.
• Two approaches:– Calorimetric Photon Information – Tracking Photon Information (ee pair conversion)
April 13, 2011
Mass (MeV) Mass-M(J/ )y BF(%) of g J/y
cc0 3414.75 317.83 1.16 ± 0.08
cc1 3510.66 413.74 34.4 ± 1.5
cc2 3556.20 459.28 19.5 ± 0.8
Very Preliminary
W. Park USC Physics Seminar 12
D*+ Cross-section Measurement using D0K3p
April 13, 2011
Validated result with independent decay channel.
W. Park USC Physics Seminar 16
Evaluate Tracking Performance
D*+D0p; D0K3p D*+D0p; D0Kp
Preliminary
April 13, 2011
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