Performance of the ALEPH Time Projection Chamber

Heavy flavour production and decay with prompt leptons in the ALEPH detector

“…For the data used in these analyses, taken in 1990 and 1991, charged tracks are measured over the range jcos( )j < 0:95, where is the polar angle, by an inner cylindrical drift chamber (itc) and a large cylindrical time projection chamber (tpc). These chambers are immersed in a magnetic eld of 1.5 Tesla and together measure the momentum of charged particles with a resolution [3] of P=P = 0 : 0008P (P in GeV=c)…”

“…The calorimeters and muon chambers cover nearly the entire 4 solid angle. 3 The simulation of heavy avour processes in Z decays at LEP…”

“…Within the Standard Model this is related to the e ective electroweak mixing angle through the relation g V f =g A f = 1 2 Q f T 3 f (sin 2 eff W + C f ) where Q f is the fermion charge and T 3 f is the third component of the fermion weak isospin. The residual vertex correction, C f , is equal to zero by de nition for leptons.…”

Search for particles with unexpected mass and charge in Z decays

“…Due to the nite two track resolution of the TPC, two same-sign tracks with momenta larger than 5 GeV=c and an opening angle less than two degrees often are not properly resolved [14]. In order to increase the rejection of such candidates, additional cuts were applied in the track selection and dE=dx evaluation.…”

“…1 the expected ionization loss (dE=dx) curves of known particles in the ALEPH TPC are shown, normalized to a minimum ionizing particle (MIP), as a function of the apparent momentum (momentum divided by the magnitude of the charge). These lines are drawn according to the empirical formula [13], dE dx = q 2 p (K + 2 ln () p ()) ; (1) where q is the charge in units of the electron charge, and are the usual Lorentz variables, and , p, K, and the polynomial () are obtained from the ALEPH data [14]. A scatter-plot of dE=dx versus apparent momentum from part of the data sample is shown in Fig.…”