392
A. Ariga et al.
apart yielded a time resolution better than 1 ns. The setup was complemented by
a lead glass array and a hadron calorimeter followed by a muon spectrometer. Three
thousand eight hundred eighty-six neutrino interactions were located in the fiducial
volume of the target. One hundred and twenty-two events were tagged by the
presence of a secondary vertex in the target, 119 induced by neutrinos and 3 by antineutrinos. Events with a candidate charmed hadron in the final state were studied
in detail in order to detect the presence of heavily ionizing particles (baryons) and
fully reconstruct the kinematics at the decay vertex. Among those events, 57 were
classified as D 0 candidates.
The analysis of the charmed hadrons is reported in [38]. Re-analyses of these
results were conducted later and removed some biases present in the original studies
([39, 40]). The result on the cross-section measurements are given in [41]. In this
paper, the observation of one event with the D 0 − ¯
D 0 topology was reported,
interpreted as associated charm production in neutral current interactions. The
lifetime of charmed particles was extensively studied by E531 [42]. Limits were
also set on ν μ ↔ ν τ oscillations [43].
After the discovery of the b quark in 1977 [44], experiments with nuclear
emulsions aimed at the direct observation of the production and decay of B flavored
hadrons. A successful search was first performed by the WA75 experiment at CERN
by using a π − beam of 350 GeV [45]. Eight hundred and one of nuclear emulsion,
in the form of double-coated plates and stripped pellicles, was exposed in 1983 and
1984. The emulsion stacks were placed both parallel and perpendicular to the beam,
so exploiting the advantages of both approaches. Emulsions held perpendicular to
the beam in vertical position can in fact tolerate higher track densities, while those
placed parallel are more sensitive to short particle lifetimes.
The emulsion was delivered in gel form by FUJI (75 l) and ILFORD (5 l) and the
pouring was done in a facility set-up at CERN [46]. Each vertical stack was made of
25 double-coated plates (330 μm thick emulsion, poured on both sides of a 70 μm
thick Lexan support), 25×25 cm 2 wide and packed in vacuum. The horizontal stacks
were made of 60 stripped emulsion pellicles, 11 cm × 4 cm (4 cm along the beam)
and 600 μm thick, piled-up and clamped between two rigid Perspex plates. The
processing of the films was carried out in Nagoya for double-coated plates, in Rome
for pellicles, and at CERN for both. After processing, each double-coated plate was
cut into 64 squares, 3 ×3 cm in size, so-called mini-modules. Twenty-five squares
of a module were then stuck, in sequence, on a single Lucite foil. With such a
technique, the corresponding areas of consecutive emulsion plates were adjacient,
thus reducing the time needed to follow a track through the stack [47]. The size of
the beam was so small that it was necessary to move the target during each beam
spill in order to have a uniform irradiation, thus introducing the concept of target
mover. The WA75 experiment observed one event [48], schematically depicted in
Fig. 9.5 as recorded in the pellicles, where both B hadrons are observed to decay
into a charmed particle. The experiment also made the first observation of the purely
muonic D s decay measuring the decay constant f D s [49].
The Fermilab E653 experiment [50] was designed to measure the lifetime of B
hadrons. This detector was an extension of the hybrid emulsion technique developed
A. Ariga et al.
apart yielded a time resolution better than 1 ns. The setup was complemented by
a lead glass array and a hadron calorimeter followed by a muon spectrometer. Three
thousand eight hundred eighty-six neutrino interactions were located in the fiducial
volume of the target. One hundred and twenty-two events were tagged by the
presence of a secondary vertex in the target, 119 induced by neutrinos and 3 by antineutrinos. Events with a candidate charmed hadron in the final state were studied
in detail in order to detect the presence of heavily ionizing particles (baryons) and
fully reconstruct the kinematics at the decay vertex. Among those events, 57 were
classified as D 0 candidates.
The analysis of the charmed hadrons is reported in [38]. Re-analyses of these
results were conducted later and removed some biases present in the original studies
([39, 40]). The result on the cross-section measurements are given in [41]. In this
paper, the observation of one event with the D 0 − ¯
D 0 topology was reported,
interpreted as associated charm production in neutral current interactions. The
lifetime of charmed particles was extensively studied by E531 [42]. Limits were
also set on ν μ ↔ ν τ oscillations [43].
After the discovery of the b quark in 1977 [44], experiments with nuclear
emulsions aimed at the direct observation of the production and decay of B flavored
hadrons. A successful search was first performed by the WA75 experiment at CERN
by using a π − beam of 350 GeV [45]. Eight hundred and one of nuclear emulsion,
in the form of double-coated plates and stripped pellicles, was exposed in 1983 and
1984. The emulsion stacks were placed both parallel and perpendicular to the beam,
so exploiting the advantages of both approaches. Emulsions held perpendicular to
the beam in vertical position can in fact tolerate higher track densities, while those
placed parallel are more sensitive to short particle lifetimes.
The emulsion was delivered in gel form by FUJI (75 l) and ILFORD (5 l) and the
pouring was done in a facility set-up at CERN [46]. Each vertical stack was made of
25 double-coated plates (330 μm thick emulsion, poured on both sides of a 70 μm
thick Lexan support), 25×25 cm 2 wide and packed in vacuum. The horizontal stacks
were made of 60 stripped emulsion pellicles, 11 cm × 4 cm (4 cm along the beam)
and 600 μm thick, piled-up and clamped between two rigid Perspex plates. The
processing of the films was carried out in Nagoya for double-coated plates, in Rome
for pellicles, and at CERN for both. After processing, each double-coated plate was
cut into 64 squares, 3 ×3 cm in size, so-called mini-modules. Twenty-five squares
of a module were then stuck, in sequence, on a single Lucite foil. With such a
technique, the corresponding areas of consecutive emulsion plates were adjacient,
thus reducing the time needed to follow a track through the stack [47]. The size of
the beam was so small that it was necessary to move the target during each beam
spill in order to have a uniform irradiation, thus introducing the concept of target
mover. The WA75 experiment observed one event [48], schematically depicted in
Fig. 9.5 as recorded in the pellicles, where both B hadrons are observed to decay
into a charmed particle. The experiment also made the first observation of the purely
muonic D s decay measuring the decay constant f D s [49].
The Fermilab E653 experiment [50] was designed to measure the lifetime of B
hadrons. This detector was an extension of the hybrid emulsion technique developed