Study of B0(s) oscillations and lifetime using fully reconstructed D(s)- decays

A search for B0s oscillations is performed using approximately 4 million Z→qq¯ events collected by the ALEPH experiment during 1991–1995. B0s candidates are partially reconstructed by combining tracks with fully reconstructed D−s candidates. The B0s production flavour is estimated from the sign of the opposite hemisphere charge, a fragmentation kaon in the same hemisphere, or a lepton in the opposite hemisphere. From a total sample of 1620 candidates, with a B0s purity estimated to be 22%, all values of Δms below 3.9 ps −1 and between 6.5 and 8.8 ps −1 are excluded at 95% CL. From the same sample, the B0s lifetime is measured to be τs=1.47±0.14(stat)±0.08(syst) ps. This analysis selects mainly hadronic B0s decays and is statistically independent of a previous ALEPH analysis selecting B0s→D(∗)−sℓ+ν candidates. Combining these two analyses yields Δms>7.9 ps −1 at 95% CL and τs=1.51±0.11 ps

K0(S) production in tau decays

From a sample of about 160k Z→τ+τ− candidates collected with the ALEPH detector at LEP between 1991 and 1995, τ lepton decays involving K0S→π+π− are studied. The K0SK0L associated production in τ decays is also investigated. The branching ratios are measured for the inclusive decay B(τ−→K0SX−ντ)=(9.70\pm0.58±0.62)×10−3 , where X− can be anything, and for the exclusive decays B(τ−→K¯¯¯0π−ντ)=(8.55±1.17±0.66)×10−3, B(τ−→K¯¯¯0π−π0ντ)=(2.94±0.73±0.37)×10−3, B(τ−→K¯¯¯0K−ντ)=(1.58±0.42±0.17)×10−3, B(τ−→K¯¯¯0K−π0ντ)=(1.52\pm0.76±0.21)×10−3. The decay τ−→K0SK0Lπ−ντ is studied for the first time, giving a branching ratio B(τ−→K0SK0Lπ−ντ)=(1.01±0.23±0.13)×10−3. The channels τ−→K0SK0Sπ−ντ , τ−→K0SK0Sπ−π0ντ , τ−→K0SK0Lπ−π0ντ , τ−→K¯¯¯0π−π0π0ντ , τ−→K0K−π0π0ντ and τ−→K0h+h−h−ντ are also investigated. In addition, mass spectra in the K0Sh− and K0Sh−π0 final states are analysed to provide information on the intermediate states produced in the decays

Search for the standard model Higgs boson at the LEP2 collider near root s=183 GeV (vol 440, pg 403, 1998)

During 1997 the ALEPH experiment at LEP gathered 57 pb(-1) of data at centre-of-mass energies near 183 GeV. These data are used to look for possible signals from the production of the Standard Model Higgs boson in the reaction e(+)e(-) --> HZ. No evidence of a signal is found in the data; seven events are selected, in agreement with the expectation of 7.2 events from background processes. This observation results in an improved lower limit on the mass of the Higgs boson: m(H) greater-than 87.9 GeV/c(2) at 95% confidence level. (C) 1999 Elsevier Science B.V. All rights reserved