The NA60 experiment has studied low-mass muon pair production in proton–nucleus collisions with a system of Be, Cu, In, W, Pb and U targets, using a 400 GeV proton beam at the CERN SPS. The ...transverse momentum spectra of the
ρ
/
ω
and
ϕ
mesons are measured in the full
p
T
range accessible, from
p
T
=
0
up to
2
GeV/c
. The nuclear dependence of the production cross sections of the
η
,
ω
and
ϕ
mesons has been found to be consistent with the power law
σ
pA
∝
A
α
, with the
α
parameter increasing as a function of
p
T
for all the particles, and an approximate hierarchy
α
η
≈
α
ϕ
>
α
ω
. The cross section ratios
σ
η
/
σ
ω
,
σ
ρ
/
σ
ω
and
σ
ϕ
/
σ
ω
have been studied as a function of the size A of the production target, and an increase of the
η
and
ϕ
yields relative to the
ω
is observed from p–Be to p–U collisions.
•Quantitative estimation of beta + emitters production rates with the GEANT4 simulation toolkit at 55, 65, 120 and 220 MeV.•Comparison of the 55 MeV simulated production rates to data from Dendooven ...et al.•Comparison of the simulated β+ activity profiles to those extracted from experimental data.•Study of 12N which, from the work of Dendooven et al., is known to be the main isotope for in-beam PET.
The purpose of this work is to evaluate the precision with which the GEANT4 toolkit simulates the production of β+ emitters relevant for in-beam and real-time PET in proton therapy.
An important evolution in proton therapy is the implementation of in-beam and real-time verification of the range of protons by measuring the correlation between the activity of β+ and dose deposition.
For that purpose, it is important that the simulation of the various β+ emitters be sufficiently realistic, in particular for the 12N short-lived emitter that is required for efficient in-beam and real-time monitoring.
The GEANT4 toolkit was used to simulate positron emitter production for a proton beam of 55 MeV in a cubic PMMA target and results are compared to experimental data.
The three β+ emitters with the highest production rates in the experimental data (11C, 15O and 12N) are also those with the highest production rate in the simulation. Production rates differ by 8% to 174%. For the 12N isotope, the β+ spatial distribution in the simulation shows major deviations from the data. The effect of the long range (of the order of 20 mm) of the β+ originating from 12N is also shown and discussed.
At first order, the GEANT4 simulation of the β+ activity presents significant deviations from the data. The need for precise cross-section measurements versus energy below 30 MeV is of first priority in order to evaluate the feasibility of in-beam and real-time PET.
The NA60 experiment at the CERN SPS has studied low-mass dimuon production in 158A GeV In-In collisions. An excess of pairs above the known meson decays has been reported before. We now present ...precision results on the associated transverse momentum spectra. The slope parameter Teff extracted from the spectra rises with dimuon mass up to the rho, followed by a sudden decline above. While the initial rise is consistent with the expectations for radial flow of a hadronic decay source, the decline signals a transition to an emission source with much smaller flow. This may well represent the first direct evidence for thermal radiation of partonic origin in nuclear collisions.
The NA60 experiment at the CERN SPS has studied low-mass muon pairs in 158 AGeV In-In collisions. A strong excess of pairs is observed above the yield expected from neutral meson decays. After ...subtraction of the decay sources, the shape of the resulting mass spectrum is largely consistent with a dominant contribution from
π
+
π
−
→
ρ
→
μ
+
μ
−
annihilation. The associated
ρ spectral function exhibits considerable broadening, but essentially no shift in mass. The acceptance-corrected
p
T
spectra have a shape atypical for radial flow. They also significantly depend on mass, pointing to different sources in different mass regions. Both mass and
p
T
spectra are compared to recent theoretical predictions.
Light and heavy ions particle therapy, mainly by means of protons and carbon ions, represents an advantageous treatment modality for deep-seated and/or radioresistant tumours. An in-beam quality ...assurance principle is based on the detection of secondary particles induced by nuclear fragmentations between projectile and target nuclei. Three different strategies are currently under investigation: prompt γ rays imaging, proton interaction vertex imaging and in-beam positron emission tomography. Geant4 simulations have been performed first in order to assess the accuracy of some hadronic models to reproduce experimental data. Two different kinds of data have been considered: β(+)-emitting isotopes and prompt γ-ray production rates. On the one hand simulations reproduce experimental β(+) emitting isotopes production rates to an accuracy of 24%. Moreover simulated β(+) emitting nuclei production rate as a function of depth reproduce well the peak-to-plateau ratio of experimental data. On the other hand by tuning the tolerance factor of the photon evaporation model available in Geant4, we reduce significantly prompt γ-ray production rates until a very good agreement is reached with experimental data. Then we have estimated the total amount of induced annihilation photons and prompt γ rays for a simple treatment plan of ∼1 physical Gy in a homogenous equivalent soft tissue tumour (6 cm depth, 4 cm radius and 2 cm wide). The average annihilation photons emitted during a 45 s irradiation in a 4 π solid angle are ∼2 × 10(6) annihilation photon pairs and 10(8) single prompt γ whose energy ranges from a few keV to 10 MeV.
The NA60 experiment studies open charm and prompt dimuon production in proton-nucleus and nucleus-nucleus collisions at the CERN SPS. During 2003 the experiment collected data in Indium-Indium ...collisions at 158 GeV per nucleon. Almost 240 million dimuon events were recorded. New results on J/\(\psi\) suppression, open-charm production and low mass dimuons should help clarify some interesting questions left open by previous experiments. After a brief detector description, this paper focuses on the analysis of the low mass dimuons. Preliminary results are presented on the \(\phi/\omega\) production cross section ratios and on the \(\phi\) transverse momentum distributions, both as a function of collision centrality.
Drake Passage, extending from the southern tip of South America to the northern Antarctic Peninsula, is a dynamic oceanographic region with well-defined habitats delineated by the three strong ...frontal jets of the Antarctic Circumpolar Current (ACC). Here, we describe seabird species distribution patterns across Drake Passage and test the hypothesis that species assemblages broadly reflect physical characteristics of the hydrographic fronts. Strip-transect seabird surveys were conducted between Tierra del Fuego and the South Shetland Islands (700 km track line) during January–March (austral summer) over 14 years (48 crossings). Locations of the latitudinally variable fronts were assessed using in situ shipboard data on sea surface temperature and salinity; areas of high variance were used to indicate frontal features. We quantified five distinct species assemblages that correspond to biogeographic regions and relate to the positions of the Sub-Antarctic Front, Polar Front and ACC Southern Front. Dense seabird concentrations coincided with regions characterized by highly variable sea surface temperature and salinity, suggesting that associated species assemblages reflect the mesoscale hydrographic surface as indicated by sea surface conditions.
PDF
