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DØ and Hunting the Higgs at Arizona• Faculty: Erich Varnes
• Postdocs: Amitabha Das (departing in January for postdoc at SMU), Xiaowen Lei (joined in Summer 2011), Ruchika Nayyar (joined January 3)
• Students: Fionbarr O’Grady (half-time, joined in summer 2011)
• Thanks to DOE for continued strong support of the DØ program!
Physics in 2011• Completed top quark analyses
– Measurement of W helicity fractions in top quark decays published in PRD
– Working with CDF on Tevatron combination
• Paper has been ~ready to go for some time, waiting for final approval from CDF
• SM is safe on this front2
• Presented as preliminary result in Summer 2011:
Physics in 2011• Transitioned to Higgs boson search (Varnes, Lei, O’Grady)
– Looking in ZH bb channel, which is complementary to LHC search (and sensitive at low mass)
• Contributions include:
– Increasing signal acceptance (for WH) by improving sensitivity to spurious missing ET and expanding trigger menu
– Updating analysis software to use newer data and Monte Carlo
– Studies of optimal use of b ID information (both in terms of statistical and systematic uncertainty)
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Example: better c jetidentification to reduce background
Physics in 2011• Limit on Higgs production cross section from DØ in ZH bb
shown at EPS’11:
• Aiming for update at Moriond, followed by publication
– Additional data + analysis improvements should increase sensitivity by ~30%
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Service in 2011• Varnes: DØ algorithms/physics coordinator
– Preparation of new data reconstruction and MC versions
– Coordinating selection of subset of data that is being reprocessed for “final” DØ results in summer 2012
– One of three nominees for spokesperson in 2011 election
• Das: shifts, L1MU trigger expert, refined version of fake track discriminant
• Lei: contributing to b ID studies
– Focusing on introducing additional information into boosted decision tree used to classify jets
• Preliminary estimate is ~5% improvement in b ID efficiency for the same background rejection
• Nayyar: EM ID convener
– Will oversee measurements of EM ID efficiency on reprocessed data
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