A. Putze

The pinching method for Galactic cosmic ray positrons: implications in the light of precision measurements

Two years ago, the AMS collaboration released the most precise measurement of the cosmic ray positron flux. It confirms that pure secondary predictions fall below the data above 10 GeV, suggesting the presence of a primary component, e.g. annihilations of WIMPs dark matter. Most analyses have focused on the high-energy part of the spectrum, disregarding the GeV energy region where cosmic ray transport is harder to model and solar modulation comes into play. Given the high quality of AMS measurements, it is timely to re-examine the positron anomaly over the entire energy range, taking into account transport processes so far neglected, e.g. convection or diffusive re-acceleration. We devise a new semi-analytical method to take into account transport processes so far neglected, but important below a few GeV. It is based on the pinching of inverse Compton and synchrotron energy losses inside the Galactic disc. It allows to carry out extensive scans over the cosmic ray propagation parameters, which we strongly constrain by requiring that the secondary component does not overshoot the AMS measurements. Only models with large diffusion coefficients survive this test. The positron flux is a powerful and independent probe of cosmic ray propagation, complementary to the boron-to-carbon ratio. We then scan over WIMP mass to fit the annihilation cross section and branching ratios, exploring both direct annihilations into standard model particles or through light mediators. In the former case, the best fit yields a p-value of 0.4\% for a mass of 264 GeV, a value that does not allow to reproduce the highest energy data points. Worse quality fits are found in the latter case. The interpretation of the positron excess in terms of single DM species annihilations is strongly disfavored. This conclusion is based solely on the positron data, and no other observation needs to be invoked.

A new look at the cosmic ray positron fraction

Mathieu Boudaud∗a, Sandy Aupetita, Sami Caroffb, Antje Putzea, Geneviève Bélangera, Yoann Genolinia, Corrine Goyb, Vincent Poireaub, Vivian Poulina, Sylvie Rosierb, Pierre Salatia, Li Taob, and Manuela Vecchic aLAPTh, Université Savoie Mont Blanc & CNRS, 9 Chemin de Bellevue, B.P.110 Annecy-le-Vieux, F-74941, France bLAPP, Université Savoie Mont Blanc & CNRS, 9 Chemin de Bellevue, B.P.110 Annecy-le-Vieux, F-74941, France cInstituto de Fisica de Saõ Carlos Av. Trabalhador saõ-carlense, 400 CEP: 13566-590 Saõ Carlos (SP), Brazil

Uncertainties on propagation parameters: impact on the interpretation of the positron fraction

Mathieu Boudauda, Sandy Aupetita, Sami Caroffb, Antje Putzea, Genevieve Belangera, Yoann Genolini∗a, Corine Goyb, Vincent Poireaub, Vivian Poulina, Sylvie Rosierb, Pierre Salatia, Li Taob, and Manuela Vecchic aLAPTh, Universite Savoie Mont Blanc & CNRS, 9 Chemin de Bellevue, B.P.110 Annecy-le-Vieux, F-74941, France bLAPP, Universite Savoie Mont Blanc & CNRS, 9 Chemin de Bellevue, B.P.110 Annecy-le-Vieux, F-74941, France cInstituto de Fisica de Sao Carlos Av. Trabalhador sao-carlense, 400 CEP: 13566-590 Sao Carlos (SP), Brazil

Approaching the Spectral Knee in High Energy Cosmic Rays with CREAM

The balloon-borne Cosmic Ray Energetics And Mass (CREAM) experiment flew for the third time in Antarctica between 19 December 2007 and 16 January 2008. This ∼29-day flight resulted in an accumulation of almost 100 days of exposure for the CREAM payload. The instrument included double layers of finely segmented Silicon detectors and an imaging Cherenkov Camera for charge measurements. A finely segmented tungsten-scintillator fiber ionization calorimeter was used for energy measurements. Energy spectra of cosmic ray particles for 1 ≤ Z ≤26 were measured at the top of atmosphere with excellent charge and energy resolution. CREAM extends direct measurements of cosmic-ray composition to energies where ground-based air shower measurements are possible, thereby providing calibration for those indirect measurements. The instrument performance during the flight and results from the on-going data analysis are presented. The project status, including preparations for the next flight and results from the beam test ca...