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.
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.
Front end electronics and first results of the ALICE V0 detector Zoccarato, Y.; Tromeur, W.; Aguilar, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2011, Letnik:
626
Journal Article
Recenzirano
This paper gives a detailed description of the acquisition and trigger electronics especially designed for the V0 detector of ALICE at LHC. A short presentation of the detector itself is given before ...the description of the Front End Electronics (FEE) system, which is completely embedded within the LHC environment as far as acquisition (DAQ), trigger (CTP), and detector control (DCS) are concerned. It is able to detect on-line coincident events and to achieve charge (with a precision of 0.6 pC) and time measurements (with a precision of 100
ps). It deploys quite a simple architecture. It is however totally programmable and fully non-standard in discriminating events coming from Beam–Beam interaction and Beam-Gas background. Finally, raw data collected from the first LHC colliding beams illustrate the performance of the system.
The NA60 experiment at the CERN SPS has studied low-mass muon pairs in 158 A GeV In–In collisions. A strong excess of pairs is observed above the yield expected from neutral meson decays. The ...unprecedented sample size close to 400000 events and the good mass resolution of about 2% made it possible to isolate the excess by subtraction of the decay sources. The shape of the resulting mass spectrum shows some non-trivial centrality dependence, but 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 pT-differential mass spectra show the excess to be much stronger at low pT than at high pT. The results are compared to theoretical model predictions; they tend to rule out models linking hadron masses directly to the chiral condensate.
Radiation effects on ALICE V0 detector components Cheynis, B.; Ducroux, L.; Grossiord, J.-Y. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2006, Letnik:
569, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The 60
MeV proton beam delivered by the RADEF facility of the University of Jyväskylä (Finland) was used to measure the radiation effects on the counter components of the V0 detector of ALICE. There ...are the scintillator BC404, the wavelength shifting fibres BCF9929A and the optical fibres BCF98 from Bicron (Saint-Gobain). The light yield and the time resolution given by a counter of the inner ring of the V0C array, mounted within a dedicated device, were measured as a function of the radiation dose up to about 300
krad. A global light attenuation of the order of 30% can be anticipated during 10 years of ALICE running.
Charmonium production in p–A collisions is a unique tool for the study of the interaction of bound cc states in nuclear matter. It can provide details on the basic features of the resonance formation ...mechanism and, in particular, on its non-perturbative aspects. In this Letter, we present an experimental study of charmonia and Drell–Yan production in proton–nucleus collisions at 450 GeV/c. The results are analyzed in the framework of the Glauber model and lead to the values of the nuclear absorption cross-section σabspA for J/ψ and ψ′. Then, we compare the J/ψ absorption in proton–nucleus and sulphur–uranium interactions, using NA38 data. We obtain that, for the J/ψ, σabspA and σabsSU are compatible, showing that no sizeable additional suppression mechanism is present in S–U collisions, and confirming that the anomalous J/ψ suppression only sets in for Pb–Pb interactions.
Three different Artificial Neural Network architectures have been applied to perform neutron/γ discrimination in neda based on waveform and time-of-flight information. Using the coincident γ-rays ...from agata, we have been able to measure and compare on real data the performances of the Artificial Neural Networks as classifiers. While the general performances are quite similar for the data set we used, differences, in particular related to the computing times, have been highlighted. One of the Artificial Neural Network architecture has also been found more robust to time misalignment of the waveforms. Such a feature is of great interest for online processing of waveforms.
The NA60 experiment at the CERN SPS has studied $\phi$ meson production in In-In collisions at 158A GeV via both the $K^+K^-$ and the $\mu^+\mu^-$ decay channels. The yields and inverse slope ...parameters of the $m_T$ spectra observed in the two channels are compatible within errors, different from the large discrepancies seen in Pb-Pb collisions between the hadronic (NA49) and dimuon (NA50) decay channels. Possible physics implications are discussed.
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.
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