BaBar Experiment

The BaBar Collaboration consisted of about 600 physicists and engineers from 75 institutions in 10 countries. Main interest of this Collaboration was the study of CP violation in the B meson sector and of heavy flavour physics.

To realize this scientific program an asymmetric-energy collider PEP-II was constructed by SLAC , LBL , and LLNL. To use the full luminosity provided by this b-factory a new detector, named BaBar, was realized in the period 1994-98. In the period 1999-2008 BaBar has recorded an integrated luminosity of 527.5 fb^-1.

BaBar main scientific achievements: First observation of mixing-induced CP violation in B⁰ decays [Phys. Rev. Lett.87,091801 (2001), Press release], discovery of new particles [Phys. Rev. Lett.90, 242001 (2003), Press release; Phys. Rev. Lett.95, 142001 (2005), Press release;], direct CP violation in B⁰ decays to K⁺π^- [Phys. Rev. Lett.93,131801 (2004), Press release], measurement of α angle of the Unitary Triangle using B⁰→π⁺π^-, B⁰→ρ⁺ρ^- , and B⁰→ρ⁺π^- , measurement of CP violation parameters in several B decay modes, observation of many B rare decays, evidence of neutral D mixing [Phys. Rev. Lett.98, 211802 (2007), Press release], observation of bottomonium ground state in Upsilon(3S) in η_b gamma decays [ Phys. Rev. Lett. 101,071801 (2008), Press release], first direct observation of time-reversal symmetry violation [Phys. Rev. Lett.109, 211801 (2012) ,Press release].

BaBar has been mentioned by name in the 2008 Nobel Prize in Physics press release

For more details on BaBar scientific achievements, see Physics Results BaBar Public Web Home Page .

BaBar-Milan

Components (30/10/2009): Fernando Palombo (Principal Investigator), Alfio Lazzaro (Post-doc), Vincenzo Lombardo (Post-doc), Simone Stracka (PhD), Pietro Biassoni (PhD), Paolo Gandini (PhD).

High Density Interconnect (HDI) and tails of the BaBar Silicon Vertex Tracker were designed, realized and tested in Milan by me and my students (in particular dr Francesco Lanni, now at Brookhaven National Laboratory) ( F. Lanni and F. Palombo, Nucl. Instr. and Meth. A379, 300 (1996)).

We are very active in data analysis. We have measured branching fractions and time-dependent CP-violating parameters in B decays to η'K. We have observed for the first time the CP-violation in a B decay mode dominated by penguin diagrams (Phys. Rev. Lett. 98, 031801 (2007)). Here you can find the SLAC press-release for this important measurement. We have also measured the branching fraction (or upper limit at 90% CL) of several B decay modes (ηK⁰, ηη, η'η', ηω , η'ω) (Phys. Rev. Lett.87, 031101 (2001); Phys. Rev. Lett.93 181806 (2004), Phys. Rev.Lett. 95, 131803 (2005)).

Another important line of our research was the measurement of the CKM angle α in the decays B⁰ to a₁⁺(1260) π^- (Phys. Rev. Lett.97 051802 (2006)). We have measured for the first time the branching fractions and the time-dependent CP-violation parameters in these decay modes (Phys. Rev. Lett.98, 181803 (2007)). We have also observed the decays B⁰ to a₁⁺(1260) K^- and B⁺ to a₁⁺(1260) K⁰ (Phys. Rev. Lett. 100, 051803 (2008)). Based on these results, we have estimate the weak phase α in the decays B⁰ to a₁⁺(1260) π^- (Phys. Rev. D81, 052009 (2010)).

We have studied the radiative decays B⁺ to η^{( ')} K⁺ gamma, B⁰ to η^{( ')} K⁰ gamma (Phys. Rev.D74, 031102 (2006)), the three-body decay modes B⁺ to η^{( ')} η^{( ')} K⁺ and B⁰ to η^{( ')} η^{( ')} K⁰ (Phys. Rev. D74, 031105 (2006)), and the B⁰ decay to a₁⁺(1260) a₁^-(1260) (in this mode measuring also the polarization) (Phys. Rev. D80, 092007(2009).

We were active also in the study of the di-pion bottomonium transitions and search for the h₁(1P) (Phys. Rev. D.84, 011104 (2011) and in the study of two-photon interactions (Phys. rev. D84, 012004 (2011), Phys. Rev. D86, 072002 (2012).