On the muon neutrino mass Angelov, N.; Balestra, F.; Batusov, Yu ...
Nuclear physics. A,
12/2006, Letnik:
780, Številka:
1
Journal Article
Recenzirano
During the runs of the PS 179 experiment at LEAR of CERN, we photographed an event of antiproton–Ne absorption, with a complete
π
+
→
μ
+
→
e
+
chain. From the vertex of the reaction a very slow ...energy
π
+
was emitted. The
π
+
decays into a
μ
+
and subsequently the
μ
+
decays into a positron. At the first decay vertex a muon neutrino was emitted and at the second decay vertex an electron neutrino and a muon antineutrino. Measuring the pion and muon tracks and applying the momentum and energy conservation and using a classical statistical interval estimator, we obtained an experimental upper limit for the muon neutrino mass:
m
ν
<
2.2
MeV
at a 90% confidence level. A statistical analysis has been performed of the factors contributing to the square value of the neutrino mass, to deduce the possibility to reach experimentally the lowest muon neutrino mass limit from the
π
→
μ
ν
decays.
The
p
̄
Ne
annihilation cross section is measured for the first time in the momentum interval (53÷63) MeV/c. About 9000 pictures collected by the Streamer Chamber Collaboration (PS179) at LEAR-CERN ...have been scanned. Four events are found, corresponding to
σ
ann=2210±1105 mb. The result is compared to the set of measurements presently available in the region of low p̄ momentum.
A note on “overfishing” Pontecorvo, Giulio
Marine policy,
11/2008, Letnik:
32, Številka:
6
Journal Article
Recenzirano
The continuing public concern with overfishing ignores the underlying problems that face fishery mangers. Attention needs to be given to (1) the transitory nature of the ocean environment, (2) the ...natural variation in fish stocks, (3) the role of the fishing industry and market forces in fishery management, and (4) the failure to focus on what it is we most need from the oceans, in what form we need it, and at what price.
Double-spin asymmetries for production of charged pions and kaons in semi-inclusive deep-inelastic muon scattering have been measured by the COMPASS experiment at CERN. The data, obtained by ...scattering a 160 GeV muon beam off a longitudinally polarised NH
3 target, cover a range of the Bjorken variable
x between 0.004 and 0.7. A leading order evaluation of the helicity distributions for the three lightest quarks and antiquark flavours derived from these asymmetries and from our previous deuteron data is presented. The resulting values of the sea quark distributions are small and do not show any sizable dependence on
x in the range of the measurements. No significant difference is observed between the strange and antistrange helicity distributions, both compatible with zero. The integrated value of the flavour asymmetry of the helicity distribution of the light-quark sea,
Δ
u
¯
−
Δ
d
¯
, is found to be slightly positive, about 1.5 standard deviations away from zero.
First measurements of azimuthal asymmetries in hadron-pair production in deep-inelastic scattering of muons on transversely polarised LiD6 (deuteron) and NH3 (proton) targets are presented. The data ...were taken in the years 2002–2004 and 2007 with the COMPASS spectrometer using a muon beam of 160 GeV/c at the CERN SPS. The asymmetries provide access to the transversity distribution functions, without involving the Collins effect as in single hadron production. The sizeable asymmetries measured on the NH3 target indicate non-vanishing u-quark transversity and two-hadron interference fragmentation functions. The small asymmetries measured on the LiD6 target can be interpreted as indication for a cancellation of u- and d-quark transversities.
Catch of marine fish grew from after WW II–1989, at which point it stabilized. In 1996 it began to decline. It continues to decline now, at a time when earth's population is expected to reach 10 ...billion by 2050. Since the factors driving the increase are primarily the growth in income, population, technology of catching fish and ever increasing fishing effort, it is to be expected that the aggregate marine catch will continue to decline. This decline has important implications for marine ecosystems but primarily its importance relates to the human use of other global resources such as food, water and world's climate.
► Ocean catch has trended downward for nearly 15 years and will continue to do so. ► The North Atlantic and North Pacific fishing share declined from 74% to less than half. ► Catch share of seven Asian countries plus Peru and Chile rose from 15% to 44%.
There has been significant progress in tsunami research, monitoring and mitigation within the last decade. This book summarizes the state-of-the-art knowledge on tsunamis. It presents a comprehensive ...overview of tsunamis, seaquakes and other catastrophic ocean phenomena. It describes up-to-date models of tsunamis generated by a submarine earthquake, landslide, volcanic eruption, meteorites impact, and moving atmospheric pressure inhomogeneities. Models of tsunami propagation and run-up are also discussed. The book investigates methods of tsunami monitoring including satellite altimetry and the study of paleotsunamis. Non-linear phenomena in tsunami source are discussed in the context of their contribution to the wave amplitude and intensification of the vertical exchange in ocean. The book is intended for scientists, researchers and specialists in oceanography, geophysics, seismology, hydro-acoustics, geology, geomorphology, including the engineering and insurance industries.
The ratio of the total exclusive production cross sections for
η' and
η mesons has been measured in the
pp reaction at
p
beam=3.67 GeV/
c. The observed
η
′/
η ratio is (0.83±0.11
+0.23
−0.18)×10
−2 ...from which the exclusive
η
′ meson production cross section is determined to be (1.12±0.15
+0.42
−0.31) μb. Differential cross section distributions have been measured. Their shape is consistent with isotropic
η
′ meson production.
Previous observations that platelet guanosine 3′, 5′-monophosphate (cyclic GMP) accumulation occurred during platelet aggregation and also in the presence of nitroprusside, which inhibits ...aggregation, prompted an evaluation of the effects of nitroprusside, nitric oxide, and related agents on human platelet aggregation. Adenosine diphosphate (ADP) was employed to induce irreversible aggregation of human platelets in platelet-rich plasma. Nitroprusside, nitric oxide, and N-methyl-N′-nitro-N-nitrosoguanidine, in a concentration-dependent manner, inhibited ADP-induced platelet aggregation, markedly activated soluble platelet guanylate cyclase (70–280-fold), and markedly elevated platelet cyclic GMP levels (100–200-fold). The gaseous phase of cigarette smoke, which contains nitric oxide, also inhibited platelet aggregation and elevated platelet cyclic GMP levels. In addition to attenuating aggregation, these agents were effective in disaggregating platelets, which was associated with a concomitant rise in cyclic GMP levels. Thus, cyclic GMP accumulation was associated with both inhibition and reversal of platelet aggregation. Partial inhibition of platelet aggregation was observed also with the lipophilic 8-bromo derivative of cyclic GMP. Inhibition of platelet aggregation, activation of guanylate cyclase, and elevation of cyclic GMP levels elicited by nitroprusside, nitric oxide, and related agents were partially blocked by methemoglobin, a hemoprotein with a high binding affinity for nitric oxide. These data suggest that nitric oxide may be one common reactive intermediate responsible for guanylate cyclase activation, cyclic GMP accumulation, and inhibition of platelet aggregation elicited by nitroprusside, nitrosuguanidine, and cigarette smoke. Moreover, the observations that platelet cyclic GMP formation is associated with inhibition of platelet aggregation by agents related to nitric oxide indicate that a reevaluation of the role of cyclic GMP in platelet aggregation is warranted.
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