The
p
̄
p
annihilation at rest into the
φη final state was measured for three different target densities: liquid hydrogen, gaseous hydrogen at NTP and at a low pressure of 5 mbar. The yield of this ...reaction in the liquid hydrogen target is smaller than in the low-pressure gas target. The branching ratios of the
φη channel were calculated on the basis of simultaneous analysis of the three data samples. The branching ratio for annihilation into
φη from the
3S
1
protonium state turns out to be about ten times smaller as compared to the one from the
1P
1
state.
The study of the
I=1,
J
PC
=0
++ states with the OBELIX detector in the channel
p
̄
p→K
±K
0
Sπ
∓
at three different target densities is reported. The data show the evidence for an extra scalar state ...with mass 1.29±0.01 GeV/
c
2 and width 0.080±0.005 GeV/
c
2.
New experimental results on
pd
annihilation at rest into pions plus a high momentum proton in the final state are discussed. The data sample was collected using the OBELIX spectrometer at the LEAR ...facility (CERN). The annihilation probabilities, or more precisely the yields (
Y) via channels
pd → 2π
−π
+π
0p
and
pd → 3π
−2π
+π
0p
with proton momenta
p > 400 MeV/
c have been measured for the first time:
Y = (93.2 ± 1.6) × 10
−4 and
Y = (52.2 ± 1.4) × 10
−4, respectively. The signal in the invariant mass distribution of the
pπ
+ system in the region of the well-known
Δ
++(1232)-isobar is clearly seen in reactions
pd → 2π
−π
+p
,
pd → 2π
−π
+π
0p
,
pd → 3π
−2π
+p
and
pd → 3π
−2π
+π
0p
. The upper limit on reaction
p (Δ
−Δ
++) → 2π
−π
+p
in the
p
d
annihilation at rest, which could be interpreted as a manifestation of the ΔΔ component of the deuteron, was found to be
Y ≤ 6.5 × 10
−5 with a 90% confidence level.
The study of the
K
±
K
miss
0
π
∓
π
+
π
− channel (7016 events), from
pp
annihilations in a gaseous hydrogen target at NTP, with the OBELIX spectrometer at LEAR (CERN), is presented. A spin-parity ...analysis provides evidence for two axial vectors, one in the low
K
Kπ
mass region, the well established
f
1(1285), decaying to
a
0(980)
π, the second, the 1
++ component of the old puzzling
E
l
, the
f
1(1420), decaying mainly to
K
∗
K
, seen for the first time in
pp
annihilation at rest. The analysis confirms the dominant production of the pseudoscalar η(1405), decaying mainly to
(Kπ)
S
K
, and the existence of a second pseudoscalar in the same mass region, the η(1460), decaying mainly to
K
∗
K
.
The signals of the
K
K
decays of two
J
PC
= 0
++ isoscalars, f
0(1.4) and f
0(1.5), are directly observable in the channels of annihilations at rest
p
p → K
SK
Sπ
0
in liquid H
2 and
pn → K
SK
Sπ
−
...in liquid D
2. Both states are relatively narrow: Γ(1.4)∼ 200 MeV, Γ(1.5) ∼ 100 MeV. The ratios between the invariant couplings to
K
K
and ππ of f
0(1.4) and f
0(1.5) are of the order of 0.5. A prominent structure mainly generated by the
a
0(1.4) and f
0(1.4) amplitudes is one of the main features of the
K
+
K
−
π
0 channel of
p
p
annihilations in liquid H
2. The existence of the f
0(1.4) and f
0(1.5) besides the f
0(0.98) makes one of these three mesons in excess to be accomodated in the 0
++ nonet. The ratios between the invariant couplings
K
K
and ππ are not compatible with ideal mixing of the 0
++ nonet and support the hypothesis that both f
0(1.4) and f
0(1.5) may have a large
gg component. Spontaneous polarization of
p
p
annihilations at rest causes striking effects in the
K
+
K
−
π
0 final state. A global polarization and isospin analysis of
pN → K
Kπ
annihilation channels is necessary for reliable determinations of mass, width and decays of the f
0 mesons.
Progress in TPG construction [particle detector] Ableev, V.; Ambrosino, F.; Apollonio, M. ...
Proceedings of the 21st IEEE Instrumentation and Measurement Technology Conference (IEEE Cat. No.04CH37510),
2004, Letnik:
2
Conference Proceeding
TPG is the acronym for a 3D imaging gas chamber with GEM amplification, hexaboard read-out and FADC electronics. We have constructed a TPG-head with three GEM foils (30 cm diameter) and a read-out ...board (30 cm diameter active surface) covered with 710000 hexagonal pads of 300 /spl mu/m size. The aligned pads are connected in parallel to one strip out of three sets of 576 parallel strips (500 /spl mu/m pitch). The three sets of strips run at 120 degrees from each other and at three different depths inside the hexaboard multi-layer structure. Each strip is read by FADC electronics. The TPG-head is under initial test in a small container with a drift volume 33 mm long and of 30 cm diameter. A 150 cm long drift volume inside a 0.7 Tesla solenoidal magnetic field has been prepared by using HARP-TPC instrumentation as a test bed.
Currently, nanopore-based technology for the determination of the functional activity of single enzyme molecules continues its development. The use of natural nanopores for studying single enzyme ...molecules is known. At that, the approach utilizing artificial solid-state nanopores is also promising but still understudied. Herein, we demonstrate the use of a nanotechnology-based approach for the investigation of the enzymatic activity of a single molecule of horseradish peroxidase with a solid-state nanopore. The artificial 5 nm solid-state nanopore has been formed in a 40 nm thick silicon nitride structure. A single molecule of HRP has been entrapped into the nanopore. The activity of the horseradish peroxidase (HRP) enzyme molecule inserted in the nanopore has been monitored by recording the time dependence of the ion current through the nanopore in the course of the reaction of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) oxidation reaction. We have found that in the process of ABTS oxidation in the presence of 2.5 mM hydrogen peroxide, individual HRP enzyme molecules are able to retain activity for approximately 700 s before a decrease in the ion current through the nanopore, which can be explained by structural changes of the enzyme.
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