| 日時: |
2013-02-19 16:00 - 17:00 |
| 場所: |
Room 345, Building #4, Tsukuba-campus |
| 会議名: |
Physics seminar / The observation of the violation of time reversal symmetry, and other selected results from the BaBar collaboration |
| 連絡先: |
中山浩幸 |
| 講演者: |
Christopher Hearty (University of British Columbia / IPP) |
| 講演言語: |
英語 |
| アブストラクト: |
The mechanism of CP violation in weak interactions has been validated by more than a decade of intense experimental work, particularly with studies with B mesons. Since the Standard Model theory is CPT invariant, it predicts a large time reversal (T) asymmetry to match the large observed matter-antimatter asymmetry in B mesons. However, there has been no direct observation of this T asymmetry prior to the recent result from the BaBar experiment located at the SLAC national laboratory. BaBar has undertaken an analysis where the decays of entangled neutral B mesons allow comparisons between the rates of four different transitions and their inverse, as a function of the time evolution of the B meson. The results lead to the first high significance, direct observation of T non-invariance.
Much of the focus of the BaBar physics program, and of the next generation of flavor experiments, is on the search for physics beyond the standard model. Although the search for the direct production of particles predicted by Supersymmetry is typically the domain of the Large Hadron Collider, a number of such theories predict the existence of a light CP-odd Higgs boson that can be produced in the radiative decay of Upsilon mesons, and are therefore accessible to B-factories. I will present the results of searches for such particles by BaBar.
At B-factories, searches for new physics more typically rely on the virtual production of heavy particles, whose existence modifies the value of an observable that can be predicted in the standard model. I will present a recent example of such an analysis using measurements of the decays B --> D(*) tau nu. The ratio of the branching fraction for this decay to D(*) mu nu or D(*) e nu is sensitive to the presence of a charged Higgs boson. The results disagree with the standard model at the level of 3.2 sigma. |
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