We present the measurement of the lifetime of the
Ω
c
0
we have performed using three independent data samples from two different decay modes. Using a
Σ
− beam of 340
GeV
c
we have obtained clean ...signals for the
Ω
c
0
decaying i
Ξ
−
K
−
π
+
π
+ and
Ω
−π
+π
−π
+
, avoiding topological cuts normally used in charm analysis. The short but measurable lifetime of the
Ω
c
0
is demonstrated by a clear enhancement of the signals at short but finite decay lengths. Using a continuous maximum likelihood method we determined the lifetime to be
τ
ω
c
0
= 55
−11
+13(stat)
−23
+18(syst) fs. This makes the
Ω
c
0
the shortest living weakly decaying particle observed so far. The short value of the lifetime comfirms the predicted pattern of the charmed baryon lifetimes and demonstrates that the strong interaction plays a vital role in the lifetimes of charmed hadrons.
Eur.Phys.J.C50:535-538,2007 We report on the observation of a K$_s$p resonance signal at a mass of
1765$\pm$5 MeV/c$^2$, with intrinsic width $\Gamma = 108\pm 22$ MeV/c$^2$,
produced inclusively in ...$\Sigma^-$-nucleus interactions at 340 GeV/c in the
hyperon beam experiment WA89 at CERN. The signal was observed in the kinematic
region $x_F>0.7$, in this region its production cross section rises
approximately linearly with $(1-x_F)$, reaching $BR(X\to K_S p)\cdot d\sigma
/dx_F = (5.2\pm 2.3) \mu b $ per nucleon at $x_F=0.8$. The hard \xf spectrum
suggests the presence of a strong leading particle effect in the production and
hence the identification as a $\Sigma^{*+}$ state. No corresponding peaks were
observed in the $K^- p$ and $\Lambda \pi^{\pm}$ mass spectra.
Summary form only. Load capacitance is the most significant parameter determining the noise level of readout electronics. In the case of silicon microstrip detectors, it is represented by the ...capacitance of one strip to all the adjacent strips. Measurements of this capacitance on the p- and n-side of detectors with various geometries have been performed. Double-sided detectors with a second metal layer and different readout patterns were also studied.< >
A new measurement of the b ¯ b production cross section in 920 GeV proton-nucleus collisions is presented by the HERA-B Collaboration. The b ¯ b production is tagged via inclusive bottom quark decays ...into J / ψ mesons by exploiting the longitudinal separation of J / ψ → l + l − decay vertices from the primary proton-nucleus interaction point. Both e + e − and μ + μ − channels are reconstructed for a total of 83 ± 12 inclusive b → J / ψ X events found. The combined analysis yields a b ¯ b to prompt J / ψ cross section ratio of Δ σ ( b ¯ b ) Δ σ J / ψ = 0.032 ± 0.005 stat ± 0.004 sys measured in the x F acceptance ( − 0.35 < x F < 0.15 ), extrapolated to σ ( b ¯ b ) = 14.9 ± 2.2 stat ± 2.4 sys nb/nucleon in the total phase space.
We report on the observation of a K\(_s\)p resonance signal at a mass of 1765\(\pm\)5 MeV/c\(^2\), with intrinsic width \(\Gamma = 108\pm 22\) MeV/c\(^2\), produced inclusively in ...\(\Sigma^-\)-nucleus interactions at 340 GeV/c in the hyperon beam experiment WA89 at CERN. The signal was observed in the kinematic region \(x_F>0.7\), in this region its production cross section rises approximately linearly with \((1-x_F)\), reaching \(BR(X\to K_S p)\cdot d\sigma /dx_F = (5.2\pm 2.3) \mu b \) per nucleon at \(x_F=0.8\). The hard \xf spectrum suggests the presence of a strong leading particle effect in the production and hence the identification as a \(\Sigma^{*+}\) state. No corresponding peaks were observed in the \(K^- p\) and \(\Lambda \pi^{\pm}\) mass spectra.
Inclusive differential cross sections $d\sigma_{pA}/dx_F$ and $d\sigma_{pA}/dp_t^2$ for the production of \kzeros, \lambdazero, and \antilambda particles are measured at HERA in proton-induced ...reactions on C, Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to $\sqrt {s} = 41.6$ GeV in the proton-nucleon system. The ratios of differential cross sections \rklpa and \rllpa are measured to be $6.2\pm 0.5$ and $0.66\pm 0.07$, respectively, for \xf $\approx-0.06$. No significant dependence upon the target material is observed. Within errors, the slopes of the transverse momentum distributions $d\sigma_{pA}/dp_t^2$ also show no significant dependence upon the target material. The dependence of the extrapolated total cross sections $\sigma_{pA}$ on the atomic mass $A$ of the target material is discussed, and the deduced cross sections per nucleon $\sigma_{pN}$ are compared with results obtained at other energies.
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