5 research outputs found
Production of pions, kaons and protons in pp collisions at GeV with ALICE at the LHC
The production of , , , , p, and pbar at mid-rapidity
has been measured in proton-proton collisions at GeV with the
ALICE detector. Particle identification is performed using the specific energy
loss in the inner tracking silicon detector and the time projection chamber. In
addition, time-of-flight information is used to identify hadrons at higher
momenta. Finally, the distinctive kink topology of the weak decay of charged
kaons is used for an alternative measurement of the kaon transverse momentum
() spectra. Since these various particle identification tools give
the best separation capabilities over different momentum ranges, the results
are combined to extract spectra from = 100 MeV/ to 2.5 GeV/.
The measured spectra are further compared with QCD-inspired models which yield
a poor description. The total yields and the mean are compared with
previous measurements, and the trends as a function of collision energy are
discussed.Comment: 24 pages, 18 captioned figures, 5 tables, published version, figures
at http://aliceinfo.cern.ch/ArtSubmission/node/388
Ultrahigh energy neutrinos at the Pierre Auger observatory
The observation of ultrahigh energy neutrinos (UHEνs) has become a priority in experimental astroparticle physics. UHEνs can be detected with a variety of techniques. In particular, neutrinos can interact in the atmosphere (downward-going ν) or in the Earth crust (Earth-skimming ν), producing air showers that can be observed with arrays of detectors at the ground. With the surface detector array of the Pierre Auger Observatory we can detect these types of cascades. The distinguishing signature for neutrino events is the presence of very inclined showers produced close to the ground (i.e., after having traversed a large amount of atmosphere). In this work we review the procedure and criteria established to search for UHEνs in the data collected with the ground array of the Pierre Auger Observatory. This includes Earth-skimming as well as downward-going neutrinos. No neutrino candidates have been found, which allows us to place competitive limits to the diffuse flux of UHEνs in the EeV range and above.P. Abreu ... K. B. Barber ... J. A. Bellido ... R. W. Clay ... M. J. Cooper ... B. R. Dawson ... T. A. Harrison ... A. E. Herve ... V. C. Holmes ... J. Sorokin ... P. Wahrlich ... B. J. Whelan ... et al
Sediment metal enrichment and ecological risk assessment of ten ports and estuaries in the World Harbours Project
Ten global harbours were assessed for sediment quality by quantifying the magnitude of anthropogenic change and ecological risk. Anthropogenic change (enrichment) was high for Derwent River and Sydney estuary, moderate for Santander Harbour, Rio de Janeiro and Dublin Port, slight for Hong Kong, minimal for Darwin. All 10 enrichment indices used showed similar results. Derwent River sediment was rated at high ecological risk, followed by Sydney and Santander estuaries with moderate risk. Auckland and Darwin sediments exhibited minimal ecological risk and sediment in the remaining harbours (Dublin, Hong Kong, Ravenna, Ria de Vigo and Rio de Janeiro) were assessed at slight ecological risk. The extraordinary variety of environments and types/quantities/qualities of data investigated resulted in as much a critique and development of methodology, as an assessment of human impact, including unique techniques for elemental normalisation and contaminant classification. Recommendations for an improved technical framework for sediment quality assessment are provided
Search for photons with energies above 1018eV using the hybrid detector of the Pierre Auger Observatory
A search for ultra-high energy photons with energies above 1EeV is performed
using nine years of data collected by the Pierre Auger Observatory in hybrid operation mode.
An unprecedented separation power between photon and hadron primaries is achieved by
combining measurements of the longitudinal air-shower development with the particle content
at ground measured by the fluorescence and surface detectors, respectively. Only three photon
candidates at energies 1\u20132EeV are found, which is compatible with the expected hadron induced
background. Upper limits on the integral flux of ultra-high energy photons of 0.027,
0.009, 0.008, 0.008 and 0.007 km 122 sr 121 yr 121 are derived at 95% C.L. for energy thresholds of
1, 2, 3, 5 and 10EeV. These limits bound the fractions of photons in the all-particle integral
flux below 0.1%, 0.15%, 0.33%, 0.85% and 2.7%. For the first time the photon fraction at EeV
energies is constrained at the sub-percent level. The improved limits are below the flux of
diffuse photons predicted by some astrophysical scenarios for cosmogenic photon production.
The new results rule-out the early top-down models 12 in which ultra-high energy cosmic rays
are produced by, e.g., the decay of super-massive particles 12 and challenge the most recent
super-heavy dark matter model
Search for ultrarelativistic magnetic monopoles with the Pierre Auger Observatory
We present a search for ultrarelativistic magnetic monopoles with the Pierre Auger observatory. Such
particles, possibly a relic of phase transitions in the early Universe, would deposit a large amount of energy
along their path through the atmosphere, comparable to that of ultrahigh-energy cosmic rays (UHECRs).
The air-shower profile of a magnetic monopole can be effectively distinguished by the fluorescence
detector from that of standard UHECRs. No candidate was found in the data collected between 2004 and
2012, with an expected background of less than 0.1 event from UHECRs. The corresponding
90% confidence level (C.L.) upper limits on the flux of ultrarelativistic magnetic monopoles range from
10^ 1219(cm2 sr s)^ 121 for a Lorentz factor \u3b3 = 10^9 to 2.5
7 10 1221(cm2 sr s)^ 121 for \u3b3 = 10^12. These results\u2014the
first obtained with a UHECR detector\u2014improve previously published limits by up to an order of
magnitude