Searching for decaying axion-like dark matter from clusters of galaxies

We consider the possibility of constraining the lifetime of radiatively decaying dark matter particles in clusters of galaxies inspired from generic axions of the Kaluza-Klein type. Such axions have been invoked as a possible explanation for the coronal X-ray emission from the Sun. These axions, or similar particles, can be produced inside stars and some of them remain confined by the deep gravitational potential of clusters of galaxies. Specifically, we consider regions within merging galaxy clusters (Abell 520 and the "Bullet Cluster"), where gravitational lensing observations have identified massive, but baryon poor, structures. From an analysis of X-ray observations of these mass concentrations, and the expected photon spectrum of decaying solar KK-axions, we derive lower limits to the lifetime of such axions of tau approx. 10^23 sec. However, if KK-axions constitute less than a few percent of the dark matter mass, this lifetime constraint is similar to that derived from solar KK-axions.Comment: Submitted to PRL, 4 pages, 3 figure

CAST constraints on the axion-electron coupling

In non-hadronic axion models, which have a tree-level axion-electron interaction, the Sun produces a strong axion flux by bremsstrahlung, Compton scattering, and axiorecombination, the "BCA processes." Based on a new calculation of this flux, including for the first time axio-recombination, we derive limits on the axion-electron Yukawa coupling gae and axion-photon interaction strength ga using the CAST phase-I data (vacuum phase). For ma <~ 10 meV/c2 we find ga gae < 8.1 × 10−23 GeV−1 at 95% CL. We stress that a next-generation axion helioscope such as the proposed IAXO could push this sensitivity into a range beyond stellar energy-loss limits and test the hypothesis that white-dwarf cooling is dominated by axion emission

Numerical Study of the Electron Lateral Distribution in Atmospheric Showers of High Energy Cosmic Rays

Abstract: The study of the lateral distribution of electrons in an atmospheric cascade can lead to useful conclusions on the mass and energy of the primary cosmic particle. In this work we compare the results we get from simulations by the CORSIKA program, with the theoretical NKG function expressing the lateral distribution of electrons. We then modify the original NKG function to fit better the data of the simulation. Finally, we propose this procedure as a method to approach the mass of the primary particle which started the atmospheric cascade

A CONTRIBUTION TO THE STUDY OF POSITION ANNIHILATION IN AMORPHOUS METALLIC ALLOYS

THE POSITRON ANNIHILATION IN TRANSITION METAL-METALLOID AMORPHOUS ALLOYS HAS BEEN STUDIED. THE TEMPERATURE DEPENDENCE OF POSITRON ANNIHILATION (BETWEEN 12K AND 293K) WAS EXPLAINED BY ACCEPTING THE EXISTENCE OF A VARIETY OF STRUCTURAL "DEFECTS" WHICH RESULTS TO POSITRON TRAPPING. THE POSITRON BINDING ENERGY IN SHALLOW TRAPS WAS FOUND NOT EXCEEDING 0.1 EV. STRUCTURAL RELAXATION WAS OBSERVED TO RESULT TO A DECREASE OF THE FREE VOLUME, NOT AFFECTING SUBSTANTIALLY SHALLOW TRAPS. THESE TRAPS SEEMS TO BE A KIND OF LINEAR DEFECTS. RECRYSTALLIZATION OF AMORPHOUS ALLOYS (BY RELATIVELY HIGH TEMPERATURE ANNEALING) AFFECTS SIGNIFICANTLY POSITRON ANNIHILATION CHARACTERISTICS. THE MAIN FEATURES ARE: A) A MONOTONOUS DECREASE IN POSITRON LIFETIME AND S-PARAMETER DURING THE GROWTH OF SINGLE PHASE CRYSTALLINE GRAINS AND B) THE EXISTENCE OF A MINIMUM DUE TO RECRYSTALLIZATION OF METASTABLE CRYSTALLINE PHASES WHICH HAVE APPEARED AT THE FIRST STAGES OF CRYSTALLIZATION.ΜΕΛΕΤΗΘΗΚΕ Η ΕΞΑΥΛΩΣΗ ΠΟΖΙΤΡΟΝΙΩΝ ΣΕ ΑΜΟΡΦΑ ΜΕΤΑΛΛΙΚΑ ΚΡΑΜΑΤΑ ΜΕΤΑΒΑΤΙΚΟΥ ΜΕΤΑΛΛΟΥ-ΜΕΤΑΛΛΟΕΙΔΩΝ. Η ΕΞΑΡΤΗΣΗ ΤΗΣ ΕΞΑΥΛΩΣΗΣ ΑΠΟ ΤΗ ΘΕΡΜΟΚΡΑΣΙΑ (ΜΕΤΑΞΥ 12Κ ΚΑΙ 293K) ΕΡΜΗΝΕΥΤΗΚΕ ΜΕ ΤΗΝ ΥΠΑΡΞΗ ΜΙΑΣ ΠΟΙΚΙΛΙΑΣ "ΑΤΕΛΕΙΩΝ" ΔΟΜΗΣ ΠΟΥ ΠΡΟΚΑΛΟΥΝ ΠΑΓΙΔΕΥΣΗ ΤΩΝ ΠΟΖΙΤΡΟΝΙΩΝ. Η ΕΝΕΡΓΕΙΑ ΣΥΝΔΕΣΗΣ ΣΤΙΣ ΡΗΧΕΣ ΠΑΓΙΔΕΣ ΒΡΕΘΗΚΕ ΜΙΚΡΟΤΕΡΗ ΤΟΥ 0,1 EV. Η ΔΟΜΙΚΗ ΧΑΛΑΡΩΣΗ ΠΡΟΚΑΛΕΙ ΚΥΡΙΩΣ ΜΕΙΩΣΗ ΤΟΥ ΕΛΕΥΘΕΡΟΥ ΟΓΚΟΥ, ΧΩΡΙΣ ΕΠΗΡΕΑΣΜΟ ΤΩΝ ΡΗΧΩΝ ΠΑΓΙΔΩΝ. ΟΙ ΤΕΛΕΥΤΑΙΕΣ ΦΑΙΝΕΤΑΙ ΟΤΙ ΑΠΟΤΕΛΟΥΝ ΚΑΠΟΙΟ ΕΙΔΟΣ ΓΡΑΜΜΙΚΩΝ ΑΤΕΛΕΙΩΝ . Η ΑΝΑΚΡΥΣΤΑΛΛΩΣΗ ΤΩΝ ΑΜΟΡΦΩΝ ΚΡΑΜΑΤΩΝ (ΠΟΥ ΠΡΟΚΑΛΕΙΤΑΙΜΕ ΑΝΑΠΤΗΣΗ ΣΕ ΥΨΗΛΕΣ ΣΧΕΤΙΚΑ ΘΕΡΜΟΚΡΑΣΙΕΣ) ΕΠΗΡΕΑΖΕΙ ΣΗΜΑΝΤΙΚΑ ΤΑ ΧΑΡΑΚΤΗΡΙΣΤΙΚΑ ΕΞΑΥΛΩΣΗΣ. ΤΑ ΓΕΝΙΚΑ ΧΑΡΑΚΤΗΡΙΣΤΙΚΑ ΤΗΣ ΕΞΑΡΤΗΣΗΣ ΑΥΤΗΣ ΕΙΝΑΙ: Α) ΜΟΝΟΤΟΝΗΜΕΙΩΣΗ ΤΟΥ ΧΡΟΝΟΥ ΖΩΗΣ ΤΩΝ ΠΟΖΙΤΡΟΝΙΩΝ ΚΑ S-ΠΑΡΑΜΕΤΡΟΥ ΚΑΤΑ ΤΗΝ ΑΝΑΠΤΥΞΗ ΚΡΥΣΤΑΛΛΙΚΩΝ ΚΟΚΚΩΝ ΑΠΛΗΣ ΦΑΣΗΣ ΚΑΙ Β) ΕΜΦΑΝΙΣΗ ΕΛΑΧΙΣΤΟΥ ΣΤΙΣ ΚΑΜΠΥΛΕΣ ΛΟΓΩ ΑΝΑΚΡΥΣΤΑΛΛΩΣΗΣ ΜΕΤΑΣΤΑΘΩΝ ΚΡΥΣΤΑΛΛΙΚΩΝ ΦΑΣΕΩΝ, ΕΜΦΑΝΙΣΘΕΝΤΩΝ ΣΤΑ ΠΡΩΙΜΑ ΣΤΑΔΙΑ ΤΗΣ ΚΡΥΣΤΑΛΛΩΣΗΣ

Study of the performance of the ATLAS monitored drift tube chambers under the influence of heavily ionizing α\alpha-particles

The MDT chambers of the ATLAS Muon Spectrometer will operate in a heavy LHC background environment mainly from photons and neutrons. The ionization produced by neutron recoils is much higher than the one from photons or muons and can be simulated by the use of alpha particles. A systematic study of the behavior of the ATLAS Monitored Drift Tubes (MDTs) under controlled irradiation has been performed. The presence of alpha particles results in the reduction of the gas gain due to space charge effects. The gas gain reduction has been studied in a single tube set up using a well controlled radium (/sup 226/Ra) source in order to enrich the tube gas (Ar/CO/sub 2/) with the alpha emitter /sup 220/Rn and irradiate the tubes internally. The results are confronted with Garfield simulations