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ISOTOPIC COMPOSITION OF LIGHT NUCLEI IN COSMIC RAYS: RESULTS FROM AMS-01
Aguilar, M.,Alcaraz, J.,Allaby, J.,Alpat, B.,Ambrosi, G.,Anderhub, H.,Ao, L.,Arefiev, A.,Arruda, L.,Azzarello, P.,Basile, M.,Barao, F.,Barreira, G.,Bartoloni, A.,Battiston, R.,Becker, R.,Becker, U.,Be IOP Publishing 2011 The Astrophysical journal Vol.736 No.2
<P>The variety of isotopes in cosmic rays allows us to study different aspects of the processes that cosmic rays undergo between the time they are produced and the time of their arrival in the heliosphere. In this paper, we present measurements of the isotopic ratios H-2/He-4, He-3/He-4, Li-6/Li-7, Be-7/(Be-9+Be-10), and B-10/B-11 in the range 0.2-1.4 GeV of kinetic energy per nucleon. The measurements are based on the data collected by the Alpha Magnetic Spectrometer, AMS-01, during the STS-91 flight in 1998 June.</P>
RELATIVE COMPOSITION AND ENERGY SPECTRA OF LIGHT NUCLEI IN COSMIC RAYS: RESULTS FROM AMS-01
Aguilar, M.,Alcaraz, J.,Allaby, J.,Alpat, B.,Ambrosi, G.,Anderhub, H.,Ao, L.,Arefiev, A.,Arruda, L.,Azzarello, P.,Basile, M.,Barao, F.,Barreira, G.,Bartoloni, A.,Battiston, R.,Becker, R.,Becker, U.,Be IOP Publishing 2010 The Astrophysical journal Vol.724 No.1
Cosmic-ray positron fraction measurement from 1 to 30 GeV with AMS-01
AMS-01 Collaboration,Aguilar, M.,Alcaraz, J.,Allaby, J.,Alpat, B.,Ambrosi, G.,Anderhub, H.,Ao, L.,Arefiev, A.,Azzarello, P.,Baldini, L.,Basile, M.,Barancourt, D.,Barao, F.,Barbier, G.,Barreira, G.,Bat North-Holland Pub. Co 2007 Physics letters: B Vol.646 No.4
A measurement of the cosmic ray positron fraction e<SUP>+</SUP>/(e<SUP>+</SUP>+e<SUP>-</SUP>) in the energy range of 1-30 GeV is presented. The measurement is based on data taken by the AMS-01 experiment during its 10 day Space Shuttle flight in June 1998. A proton background suppression on the order of 10<SUP>6</SUP> is reached by identifying converted bremsstrahlung photons emitted from positrons.
Compton scattering of quasi-real virtual photons at LEP
Achard, P.,Adriani, O.,Aguilar-Benitez, M.,Alcaraz, J.,Alemanni, G.,Allaby, J.,Aloisio, A.,Alviggi, M.G.,Anderhub, H.,Andreev, V.P.,Anselmo, F.,Arefiev, A.,Azemoon, T.,Aziz, T.,Bagnaia, P.,Bajo, A.,Ba Elsevier 2005 Physics letters: B Vol.616 No.3
<P><B>Abstract</B></P><P>Compton scattering of quasi-real virtual photons, γ<SUP>e±</SUP>→γ<SUP>e±</SUP>, is studied with 0.6 fb<SUP>−1</SUP> of data collected by the L3 detector at the LEP <SUP>e+</SUP><SUP>e−</SUP> collider at centre-of-mass energies s=189–209 GeV. About 4500 events produced by the interaction of virtual photons emitted by <SUP>e±</SUP> of one beam with <SUP>e∓</SUP> of the opposite beam are collected for effective centre-of-mass energies of the photon–electron and photon–positron systems in the range from <SUP>s′</SUP>=35 GeV up to <SUP>s′</SUP>=175 GeV, the highest energy at which Compton scattering was ever probed. The cross sections of the γ<SUP>e±</SUP>→γ<SUP>e±</SUP> process as a function of <SUP>s′</SUP> and of the rest-frame scattering angle are measured, combined with previous L3 measurements down to <SUP>s′</SUP>≃20 GeV, and found to agree with the QED expectations.</P>
Measurement of the running of the electromagnetic coupling at large momentum-transfer at LEP
Achard, P.,Adriani, O.,Aguilar-Benitez, M.,Alcaraz, J.,Alemanni, G.,Allaby, J.,Aloisio, A.,Alviggi, M.G.,Anderhub, H.,Andreev, V.P.,Anselmo, F.,Arefiev, A.,Azemoon, T.,Aziz, T.,Bagnaia, P.,Bajo, A.,Ba Elsevier 2005 Physics letters: B Vol.623 No.1
<P><B>Abstract</B></P><P>The evolution of the electromagnetic coupling, <I>α</I>, in the momentum-transfer range 1800 <SUP>GeV2</SUP><−<SUP>Q2</SUP><21600 <SUP>GeV2</SUP> is studied with about 40 000 Bhabha-scattering events collected with the L3 detector at LEP at centre-of-mass energies s=189–209 GeV. The running of <I>α</I> is parametrised as: [FORMULA OMISSION] where <SUB>α0</SUB>≡α(<SUP>Q2</SUP>=0) is the fine-structure constant and C=1 corresponds to the evolution expected in QED. A fit to the differential cross section of the <SUP>e+</SUP><SUP>e−</SUP>→<SUP>e+</SUP><SUP>e−</SUP> process for scattering angles in the range |cosθ|<0.9 excludes the hypothesis of a constant value of <I>α</I>, C=0, and validates the QED prediction with the result: [FORMULA OMISSION] where the first uncertainty is statistical and the second systematic.</P>
Z-boson production with two unobserved, back-to-back, hard photons at LEP
Achard, P.,Adriani, O.,Aguilar-Benitez, M.,Alcaraz, J.,Alemanni, G.,Allaby, J.,Aloisio, A.,Alviggi, M.G.,Anderhub, H.,Andreev, V.P.,Anselmo, F.,Arefiev, A.,Azemoon, T.,Aziz, T.,Bagnaia, P.,Bajo, A.,Ba Elsevier 2005 Physics letters: B Vol.613 No.3
<P><B>Abstract</B></P><P>The double-radiative process <SUP>e+</SUP><SUP>e−</SUP>→Zγγ→qq¯γγ where the two hard photons escape detection at low polar angles into opposite directions, is studied in 0.62 fb<SUP>−1</SUP> of data collected with the L3 detector at LEP at centre-of-mass energies between 188.6 and 209.2 GeV. The cross sections are measured and found to be consistent with the Standard Model expectations.</P>
Search for an invisibly-decaying Higgs boson at LEP
Achard, P.,Adriani, O.,Aguilar-Benitez, M.,Alcaraz, J.,Alemanni, G.,Allaby, J.,Aloisio, A.,Alviggi, M.G.,Anderhub, H.,Andreev, V.P.,Anselmo, F.,Arefiev, A.,Azemoon, T.,Aziz, T.,Bagnaia, P.,Bajo, A.,Ba Elsevier 2005 Physics letters: B Vol.609 No.1
<P><B>Abstract</B></P><P>A search for a Higgs boson produced in <SUP>e+</SUP><SUP>e−</SUP> collisions in association with a Z boson and decaying into invisible particles is performed. Data collected at LEP with the L3 detector at centre-of-mass energies from 189 to 209 GeV are used, corresponding to an integrated luminosity of 0.63 fb<SUP>−1</SUP>. Events with hadrons, electrons or muons with visible masses compatible with a Z boson and missing energy and momentum are selected. They are consistent with the Standard Model expectations. A lower limit of 112.3 GeV is set at 95% confidence level on the mass of the invisibly-decaying Higgs boson in the hypothesis that its production cross section equals that of the Standard Model Higgs boson. Relaxing this hypothesis, upper limits on the production cross section are derived.</P>
Neutral-current four-fermion production in <sup>e+</sup><sup>e−</sup> interactions at LEP
Achard, P.,Adriani, O.,Aguilar-Benitez, M.,Alcaraz, J.,Alemanni, G.,Allaby, J.,Aloisio, A.,Alviggi, M.G.,Anderhub, H.,Andreev, V.P.,Anselmo, F.,Arefiev, A.,Azemoon, T.,Aziz, T.,Bagnaia, P.,Bajo, A.,Ba Elsevier 2005 Physics letters: B Vol.616 No.3
<P><B>Abstract</B></P><P>Neutral-current four-fermion production, <SUP>e+</SUP><SUP>e−</SUP>→ff¯<SUP>f′</SUP><SUP>f¯′</SUP>, is studied in 0.7 fb<SUP>−1</SUP> of data collected with the L3 detector at LEP at centre-of-mass energies s=183–209 GeV. Four final states are considered: qq¯νν¯, qq¯<SUP>ℓ+</SUP><SUP>ℓ−</SUP>, <SUP>ℓ+</SUP><SUP>ℓ−</SUP><SUP>ℓ′+</SUP><SUP>ℓ′−</SUP> and <SUP>ℓ+</SUP><SUP>ℓ−</SUP>νν¯, where <I>ℓ</I> denotes either an electron or a muon. Their cross sections are measured and found to agree with the Standard Model predictions. In addition, the <SUP>e+</SUP><SUP>e−</SUP>→Z<SUP>γ∗</SUP>→ff¯<SUP>f′</SUP><SUP>f¯′</SUP> process is studied and its total cross section at the average centre-of-mass energy 〈s〉=196.6 GeV is found to be 0.29±0.05±0.03 pb, where the first uncertainty is statistical and the second systematic, in agreement with the Standard Model prediction of 0.22 pb. Finally, the mass spectra of the qq¯<SUP>ℓ+</SUP><SUP>ℓ−</SUP> final states are analysed to search for the possible production of a new neutral heavy particle, for which no evidence is found.</P>
Achard, P.,Adriani, O.,Aguilar-Benitez, M.,van den Akker, M.,Alcaraz, J.,Alemanni, G.,Allaby, J.,Aloisio, A.,Alviggi, M.G.,Anderhub, H.,Andreev, V.P.,Anselmo, F.,Arefiev, A.,Azemoon, T.,Aziz, T.,Bagna Elsevier 2005 Astroparticle physics Vol.23 No.4
<P><B>Abstract</B></P><P>The shadowing of high-energy cosmic rays by the Moon has been observed with a significance of 9.4 standard deviations with the L3+C muon spectrometer at CERN. A significant effect of the Earth magnetic field is observed. Since no event deficit on the east side of the Moon has been observed, an upper limit at 90% confidence level on the antiproton to proton ratio of 0.11 is obtained for primary energies around 1TeV.</P>