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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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