4,207 research outputs found
Massive relic neutrinos in the galactic halo and the knee in the cosmic ray spectrum
Despite many efforts to find a reasonable explanation, the origin of the
"knee" in the cosmic ray spectrum at energy around 10**15.5 eV remains
mysterious. In this letter we suggest that the "knee" may be due to a GZK-like
effect of cosmic rays interacting with massive neutrinos in the galactic halo.
Simple kinematics connects the location of the "knee" with the mass of the
neutrinos, and, while the required interaction cross section is larger than
that predicted by the Standard Model, it can be accommodated by a small
neutrino magnetic dipole moment. The values for the neutrino parameters
obtained from the analysis of existing experimental data are compatible with
present laboratory bounds.Comment: 8 pages, 1 figure, uses RevTe
Hadronic interactions models beyond collider energies
Studies of the influence of different hadronic models on extensive air
showers at ultra-high energies are presented. The hadronic models considered
are those implemented in the well-known QGSJET and SIBYLL event generators. The
different approaches used in both codes to model the underlying physics is
analyzed using computer simulations performed with the program AIRES. The most
relevant observables for both single collisions and air showers are studied for
primary energies ranging from eV up to eV. In addition,
the evolution of lateral and energy distributions during the shower development
is presented. Our analysis seems to indicate that the behaviour of shower
observables does not largely reflect the strong differences observed in single
collisions.Comment: 31 RevTex pages - 14 ps figure
Particle density distributions of inclined air showers
The Nishimura-Kamata-Greisen cascade theory is re-analyzed in order to consider inclined showers. A new parameterization of the lateral distribution function including azimuth angle dependence is presented. Monte Carlo studies for 1019 eV proton-induced air showers indicate that the proposed lateral distribution function fits the data very well
A new composition-sensitive parameter for Ultra-High Energy Cosmic Rays
A new family of parameters intended for composition studies in cosmic ray
surface array detectors is proposed. The application of this technique to
different array layout designs has been analyzed. The parameters make exclusive
use of surface data combining the information from the total signal at each
triggered detector and the array geometry. They are sensitive to the combined
effects of the different muon and electromagnetic components on the lateral
distribution function of proton and iron initiated showers at any given primary
energy. Analytical and numerical studies have been performed in order to assess
the reliability, stability and optimization of these parameters. Experimental
uncertainties, the underestimation of the muon component in the shower
simulation codes, intrinsic fluctuations and reconstruction errors are
considered and discussed in a quantitative way. The potential discrimination
power of these parameters, under realistic experimental conditions, is compared
on a simplified, albeit quantitative way, with that expected from other surface
and fluorescence estimators.Comment: 27 pages, 17 figures. Submitted to a refereed journa
A depression before a bump in the highest energy cosmic ray spectrum
We re-examine the interaction of ultra high energy nuclei with the microwave
background radiation. We find that the giant dipole resonance leaves a new
signature in the differential energy spectrum of iron sources located around 3
Mpc: A depression before the bump which is followed by the expected cutoff.Comment: revisited version, 5 pages RevTex, 5 figure
Confronting models on cosmic ray interactions with particle physics at LHC energies
Inelastic pp collisions are dominated by soft (low momentum transfer) physics
where perturbative QCD cannot be fully applied. A deep understanding of both
soft and semi-hard processes is crucial for predictions of minimum bias and
underlying events of the now coming on line pp Large Hadron Collider (LHC).
Moreover, the interaction of cosmic ray particles entering in the atmosphere is
extremely sensitive to these soft processes and consequently cannot be
formulated from first principles. Because of this, air shower analyses strongly
rely on hadronic interaction models, which extrapolate collider data several
orders of magnitude. A comparative study of Monte Carlo simulations of pp
collisions (at the LHC center-of-mass energy ~ 14 TeV) using the most popular
hadronic interaction models for ultrahigh energy cosmic ray (SIBYLL and QGSJET)
and for collider physics (the PYTHIA multiparton model) is presented. The most
relevant distributions are studied including those observables from diffractive
events with the aim of discriminating between the different models.Comment: 8 pages revtex, 8 figures, added reference
Protein Z Plasma Levels are Not Elevated in Patients with Non-Arteritic Anterior Ischemic Optic Neuropathy
Z boson production in p+Pb collisions at sNN√=5.02 TeV measured with the ATLAS detector
The ATLAS Collaboration has measured the inclusive production of Z bosons via their decays into electron and muon pairs in p+Pb collisions at √ sNN = 5.02 TeV at the Large Hadron Collider. The measurements are made using data corresponding to integrated luminosities of 29.4 nb−1 and 28.1 nb−1 for Z → ee and Z → µµ, respectively. The results from the two channels are consistent and combined to obtain a cross section times the Z → `` branching ratio, integrated over the rapidity region |y ∗ Z | < 3.5, of 139.8 ± 4.8 (stat.) ± 6.2 (syst.) ± 3.8 (lumi.) nb. Differential cross sections are presented as functions of the Z boson rapidity and transverse momentum, and compared with models based on parton distributions both with and without nuclear corrections. The centrality dependence of Z boson production in p+Pb collisions is measured and analyzed within the framework of a standard Glauber model and the model’s extension for fluctuations of the underlying nucleon-nucleon scattering cross sectionFil: Aad, G.. Aix-Marseille Université; FranciaFil: Abbott, B.. Oklahoma State University; Estados UnidosFil: Abdallah, J.. Academia Sinica; ChinaFil: Abdinov, O.. Azerbaijan Academy of Sciences; AzerbaiyánFil: Aben, R.. University of Amsterdam; Países BajosFil: Alconada Verzini, María Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Alonso, Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Arduh, Francisco Anuar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Dova, Maria Teresa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Monticelli, Fernando Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Wahlberg, Hernan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Otero y Garzon, Gustavo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Piegaia, Ricardo Nestor. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Reisin, Hernan Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Sacerdoti, Sabrina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Zieminska, D.. Indiana University; Estados UnidosFil: Zimine, N. I.. Joint Institute for Nuclear Research ; RusiaFil: Zimmermann, C.. Universität Mainz; AlemaniaFil: Zimmermann, S.. Albert-Ludwigs-Universität; AlemaniaFil: Zinonos, Z.. Georg-August-Universität; AlemaniaFil: Zinser, M.. Universität Mainz; AlemaniaFil: Ziolkowski, M.. Universität Siegen ; AlemaniaFil: Živković, L.. University of Belgrade; SerbiaFil: Zobernig, G.. University of Wisconsin; Estados UnidosFil: Zoccoli, A.. Università di Bologna; ItaliaFil: Nedden, M. zur. Humboldt University; AlemaniaFil: Zurzolo, G.. Università di Napoli; ItaliaFil: Zwalinski, L.. Cern - European Organization For Nuclear Research; SuizaFil: The ATLAS Collaboration. No especifica
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