Flavor Physics in the Quark Sector

One of the major challenges of particle physics has been to gain an in-depth understanding of the role of quark flavor and measurements and theoretical interpretations of their results have advanced tremendously: apart from masses and quantum numbers of flavor particles, there now exist detailed measurements of the characteristics of their interactions allowing stringent tests of Standard Model predictions. Among the most interesting phenomena of flavor physics is the violation of the CP symmetry that has been subtle and difficult to explore. Till early 1990s observations of CP violation were confined to neutral $K$ mesons, but since then a large number of CP-violating processes have been studied in detail in neutral $B$ mesons. In parallel, measurements of the couplings of the heavy quarks and the dynamics for their decays in large samples of $K, D$, and $B$ mesons have been greatly improved in accuracy and the results are being used as probes in the search for deviations from the Standard Model. In the near future, there will be a transition from the current to a new generation of experiments, thus a review of the status of quark flavor physics is timely. This report summarizes the results of the current generation of experiments that is about to be completed and it confronts these results with the theoretical understanding of the field

Measurement of hadron and lepton-pair production at 130 GeV<root s<140 GeV at LEP

Contains fulltext : 26240.pdf (publisher's version ) (Open Access

Measurement of hadron and lepton-pair production at 161 GeV<root s<172 GeV at LEP

Contains fulltext : 26256.pdf (publisher's version ) (Open Access

Flavor physics in the quark sector.

In the past decade, one of the major challenges of particle physics has been to gain an in-depth understanding of the role of quark flavor. In this time frame, measurements and the theoretical interpretation of their results have advanced tremendously. A much broader understanding of flavor particles has been achieved; apart from their masses and quantum numbers, there now exist detailed measurements of the characteristics of their interactions allowing stringent tests of Standard Model predictions. Among the most interesting phenomena of flavor physics is the violation of the CP symmetry that has been subtle and difficult to explore. In the past, observations of CP violation were confined to neutral K mesons, but since the early 1990s, a large number of CP-violating processes have been studied in detail in neutral B mesons. In parallel, measurements of the couplings of the heavy quarks and the dynamics for their decays in large samples of K,D, and B mesons have been greatly improved in accuracy and the results are being used as probes in the search for deviations from the Standard Model. In the near future, there will be a transition from the current to a new generation of experiments; thus a review of the status of quark flavor physics is timely. This report is the result of the work of physicists attending the 5th CKM workshop, hosted by the University of Rome “La Sapienza”, September 9–13, 2008. It summarizes the results of the current generation of experiments that are about to be completed and it confronts these results with the theoretical understanding of the field which has greatly improved in the past decade

Measurement of hadron and lepton-pair production at 130 GeV<root s<140 GeV at LEP

We report on the first measurements of e(+)e(-) annihilations into hadrons and lepton pairs at centre-of-mass energies between 130 GeV and 140 GeV. In a total luminosity of 5 pb(-1) collected with the L3 detector at LEP we select 1577 hadronic and 401 lepton-pair events. The measured cross sections and leptonic forward-backward asymmetries agree well with the Standard Model predictions

Search for neutral Higgs boson production through the process e(+)e(-)->Z(*)H(0)

The results of the searches for neutral Higgs boson production in the process e(+)e(-) --> Z* H-0 are reported, focusing on Higgs boson masses below 70 GeV. The data sample consists of three million hadronic Z(0) decays collected by the L3 experiment at LEP from 1991 through 1994. No signal is found leading to a lower limit on the mass of the Standard Model Higgs boson of 60.2 GeV at 95% C.L. These results are also interpreted in the framework of the General Two Doubler Model and limits on the nonstandard Higgs boson production through the process e(+)e(-) --> Z*h(0) are set. A lower limit of 66.7 GeV at 95% C.L. is obtained for the case where the Higgs decays into an invisible final state

Search for supersymmetric particles at 130 GeV<root s<140 GeV at LEP

Contains fulltext : 26248.pdf (publisher's version ) (Open Access

Measurement of the Bd0_{d}^{0} meson oscillation frequency

Time-dependent \Bd-\Bbd\ mixing is studied using 1.5 million hadronic Z decays collected by L3. Semileptonic B decays are selected by requiring at least one reconstructed lepton in both thrust hemispheres. Charge correlations between the tagged leptons are studied as a function of proper time. The proper time of the b-hadron decay is measured by reconstructing the production and decay vertices using a silicon microvertex detector. The measured \Bd\ meson oscillation frequency corresponds to a mass difference \Dmd\ between the two \Bd\ mass eigenstates of \begin{displaymath} \Dmd = \left( 0.496 ^{+ 0.055}_{- 0.051}\ \mathrm{(stat)} \pm{ 0.043}\ \mathrm{(syst)} \right)\ \mathrm{ps}^{-1}. \end{displaymath

Measurement of the B-d(0) meson oscillation frequency

Time-dependent B-d(0)-(B) over bar(d)(0) mixing is studied using 1.5 million hadronic Z decays collected by L3. Semileptonic B decays are selected by requiring at least one reconstructed lepton in both thrust hemispheres. Charge correlations between the tagged leptons are studied as a function of proper time. The proper time of the b-hadron decay is measured by reconstructing the production and decay vertices using a silicon microvertex detector: The measured B-d(0) meson oscillation frequency corresponds to a mass difference Delta m(d) between the two B-d(0) mass eigenstates of Delta m(d) = (0.496(-0.051)(+0.053) (stat) +/- 0.043 (syst)) ps(-1)