Roy Briere

Professor, Physics

Education

Research

My research field is high-energy particle physics.  I am interested in "flavor physics" as well as other topics.  Flavor physics is the study of the decays and other properties of the different types (or flavors) of quarks.  The weak interaction, which is responsible for these decays, has several unique features, including the violation of discrete symmetries such as parity (mirror reflection) and CP (combined parity and matter-antimatter inversion).  In addition, it is the only force which results in a change of particle type upon emission of one of its force carriers, the W boson.  As such, it is responsible for all fundamental decays.

My main activity involves the BESIII experiment at the BEPCII collider in Beijing.  Electron-positron collisions are used to produce various bound states of charm quarks.  I joined in 2008, shortly before first data-taking, along with several other US colleagues with the aim of focusing on charm physics via weak decays of D mesons.  Many key measurements needed for progress in flavor physics, such as decay constants, semileptonic form factors, and absolute hadronic branching ratios, can be made by our experiment.  Key results will be compared with modern Lattice QCD.  In many cases, our goal is to validate the LQCD results in the charm sector to give confidence in other LQCD results.  These other calculations are a critical input to interpretations of already existing data about
bottom quark decays, but are not easy to directly validate as they are in the case of charm.  The world's best charm results are from CLEO (another experiment I collaborate on), but greater precision is desirable to perform even more stringent tests. 

My interest in flavor physics stems from my Ph.D. research measuring CP violation and performing tests of CPT symmetry (CP plus reversal of time flow) in the neutral K meson system, involving weak interactions of strange quarks.  Since 1995, I have been a member of the CLEO collaboration, which also used electron-positron collisions to study bottom and charm quarks. Data-taking finished in 2008, and while final results are still being extracted, my focus is now shifting toward extending key CLEO results at BESIII. 

In addition to physics analysis, other interests include calibration of wire drift chambers (both for tracking and for dE/dx particle identification), and work on other software infrastructure, particularly "D Tagging" tools.  I also served as CLEO's co-spokesperson from 2005-7, and earlier as CLEO Analysis Coordinator.

Selected Publications

• M. Ablikim et al., Evidence for the Direct Two-Photon Transition from ψ(3686) to J/ψ, Physical Review Letters 109, 172002 (2012)
• Xue-Xiang Cao et al., Studies of dE/dx measurements with the BESIII, Chinese Physics C 34, 1852 (2010)
• R. Briere et al., Inclusive χ_bJ(nP) decays to D⁰X, Physical Review D 78, 092007 (2008)
• S. Dobbs et al., Measurement of absolute hadronic branching fractions of D mesons and e⁺e^-→DD̅ cross sections at the ψ(3770), Physical Review D 76, 112001 (2007)
• D. Asner et al., Antideuteron production in Υ(nS) decays and the nearby continuum, Physical Review D 75, 012009 (2007)
• Q. He et al., Measurement of Absolute Hadronic Branching Fractions of D Mesons and e⁺e^-→DD̅ Cross Sections at E_c.m.=3773  MeV, Physical Review Letters 95, 121801 (2005)   Erratum: Physical Review Letters 96, 199903 (2006)
• G. Huang et al., Study of the Semileptonic Charm Decays D⁰→π^-ℓ⁺ν and D⁰→K^-ℓ⁺ν, Physical Review Letters 94, 011802 (2005)
• S. Csorna et al., Measurements of the branching fractions and helicity amplitudes in B→D*ρ decays, Physical Review D 67, 112002 (2003)
• Roy Briere, Bruce Winstein, Determining the Phase of a Strong Scattering Amplitude from Its Momentum Dependence to Better Than 1°: The Example of Kaon Regeneration, Physical Review Letters 75, 402 (1995)  Erratum: Physical Review Letters 75, 2070-2070 (1995)
• B. Schwingenheuer et al., CPT Tests in the Neutral Kaon System, Physical Review Letters 74, 4376 (1995)
• Roy Briere, Lynne Orr, Possible test of CPT invariance in neutral-kaon regeneration, Physical Review D 40, 2269 (1989)