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TOPIC: top quark decay

Blobrana

L

Posts: 131433

Date: Jul 1 17:22 2011

Dimuon charge asymmetry	Permalink

Antimatter Tevatron mystery gains ground US particle physicists are inching closer to determining why the Universe exists in its current form, made overwhelmingly of matter. Physics suggests equal amounts of matter and antimatter should have been made in the Big Bang. In 2010, researchers at the Tevatron accelerator claimed preliminary results showing a small excess of matter over antimatter as particles decayed. Read more __________________

Blobrana

L

Posts: 131433

Date: Jun 30 17:55 2011

b-hadron decays	Permalink

Title: Measurement of the anomalous like-sign dimuon charge asymmetry with 9 fb^-1 of ppbar collisions Authors: The D0 Collaboration et al. We present an updated measurement of the anomalous like-sign dimuon charge asymmetry Ab_sl for semi-leptonic b-hadron decays in 9.0 fb^-1 of ppbar collisions recorded with the D0 detector at a center-of-mass energy of root s = 1:96 TeV at the Fermilab Tevatron collider. We obtain Ab_sl =(-0:787 ±0:172 (stat) ±0:093 (syst))%. This result differs by 3:9 standard deviations from the prediction of the standard model and provides evidence for anomalously large CP violation in semi-leptonic neutral B decay. The dependence of the asymmetry on the muon impact parameter is consistent with the hypothesis that it originates from semi-leptonic b-hadron decays. Read more (483kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Feb 23 20:54 2011

top quark decay	Permalink

Title: Interplay of t --> b W Decay and B_q Meson Mixing in Minimal Flavor Violating Models Authors: Jure Drobnak, Svjetlana Fajfer, Jernej F. Kamenik Precise measurements of the top quark decay properties at hadron colliders offer interesting new possibilities of testing the standard model. At the same time, recent intriguing experimental results concerning CP violation in the B_d and B_s systems have stimulated many studies of physics beyond the standard model. We investigate anomalous t W d_j interactions as a possible source of new effects in B_{d,s} - bar B_{d,s} oscillations within a model independent approach based on the assumptions of Minimal Flavor Violation. After matching our effective operators onto the low-energy effective Lagrangian describing B_{d,s} meson mixing and evolving it down to the B-mass scale, we extract the preferred ranges of the anomalous t W d_j interactions at the weak scale. These values are then compared to previously considered constraints coming from the rare radiative B --> X_s gamma decay. Finally, we reconsider the associated effects in the t --> b W decays and find that the W helicity fractions F_{L,+} can deviate by as much as 15%, 30% from their standard model values, respectively. The deviations in F_L in particular, can reach the level of expected precision measurements at the LHC. Read more (184kb, PDF) __________________

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