CDF measures matter-antimatter B0s transition

6 June 2006

The CDF collaboration at Fermilab has announced the precision measurement of the matter-antimatter transitions for the B0s meson, which consists of a bottom quark bound to a strange anti-quark. The announcement came less than a month after the news that the D0 collaboration had measured the first upper and lower bounds on the oscillation frequency.


In a seminar at Fermilab on 10 April, the CDF Collaboration reported on their analysis of 1 fb-1 of proton-antiproton collision data acquired by the CDF detector between February 2002 and January 2006, during Tevatron Run II. Within the 700-member CDF Collaboration – from 61 institutions and 13 countries – a team of 80 researchers from 27 institutions performed the data analysis leading to the precision measurement just one month after the data-taking was completed.

The team used semileptonic and hadronic decays of the B0s and found a signature consistent with B0s-Bbar0s oscillations, with a probability that the data could randomly fluctuate to mimic such a signature of 0.5%. Analysis yielded a preliminary result for the B0s-Bbar0s oscillation frequency, Δms, of 17.33+0.42-0.21(stat.)±0.07(sys.) ps-1 – in agreement with D0’s result of 17 < Δms Δ 21 ps-1. The CDF Collaboration also derived a value for the ratio of the related parameters of the Cabibbo-Kobayashi-Maskawa matrix, |Vtd|/|Vts| = 0.208+0.008-0.007 (stat.+sys.).

This precision measurement from CDF will immediately be interpreted within different theoretical models, in particular in the context of supersymmetry. General versions of supersymmetry predict an even faster transition rate than has been measured, so some of those theories can be ruled out based upon this result. More information will come from combining precise measurements of B0s-Bbar0s oscillations and searching for the rare decay of B0s mesons into muon pairs. Both the D0 and CDF experiments expect to achieve improved results in these areas in the near future.

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