Combinaison de tous les e ff ets

En définitive, les processus modifiant l’énergie des antiprotons ayant été revus un à un, nous

les prenons désormais tous en compte et aboutissons aux spectres représentés par les courbes en

trait continu de la Fig. 6.9. Il apparaît que ces effets peuvent drastiquement modifier le spectre

des antiprotons primaires quasiment d’un facteur 3 à 100 MeV et d’environ 15% à 1 GeV. Il

est donc nécessaire de les prendre correctement en compte afin de dériver des contraintes

so-lides sur la section efficace d’annihilationhσvides particules de matière noire. Dans ce but, nous

avons calculé les spectres des antiprotons primaires correspondant à 23 canaux d’annihilation,

ainsi que de désintégration, des WIMPs dans les cas M_in, M_ed et M_ax. Nous l’avons fait pour

les six profils de densité de matière noire tabulés dans la Sec.1.1.3. Ces résultats sont disponibles

dans la dernière version du Poor Particle Physicist Cookbook for Dark Matter Indirect

Detec-tion (P_ppc4_dmidrelease 4.0) que Marco Cirelli et ses collaborateurs ont installé sur la page web

http://www.marcocirelli.net/PPPC4DMID.html.

1e-08

1e-07

1e-06

1e-05

1e-04

1e-03

1e-02

0.1 1 10 100

φ

-

[m

p -2

GeV

-1

s

-1

sr

-1

]

T

-p

[GeV]

Primary Antiproton Spectrum, Channel b, m = 200GeV

MIN With Tert/Diff Reac MED With Tert/Diff Reac MAX With Tert/Diff Reac MIN Without Tert/Diff Reac MED Without Tert/Diff Reac MAX Without Tert/Diff Reac

F_igure6.9 –Idem que la Fig.6.5où cette fois, les courbes en trait continu ont été calculées en rajoutant

tous les mécanismes détaillés dans cette section.

Bibliographie

[1] O. Adriani et al. PAMELA Measurements of Cosmic-Ray Proton and Helium Spectra.

Science, 332 :69, April 2011.

[2] Lars Bergstrom, Joakim Edsjo, and Piero Ullio. Cosmic antiprotons as a probe for

super-symmetric dark matter ? Astrophys. J., 526 :215–235, 1999.

[3] Torsten Bringmann and Pierre Salati. Galactic antiproton spectrum at high energies :

Back-ground expectation versus exotic contributions. Phys. Rev. D, 75(8) :083006, apr 2007.

[4] Mattia di Mauro, Fiorenza Donato, Andreas Goudelis, and Pasquale Dario Serpico. New

evaluation of the antiproton production cross section for cosmic ray studies. Phys. Rev. D,

90(8) :085017, oct 2014.

[5] R. P. Duperray, C.-Y. Huang, K. V. Protasov, and M. Buénerd. Parametrization of the

anti-proton inclusive production cross section on nuclei. Phys. Rev. D, 68(9) :094017, nov 2003.

[6] J. Engel, T. K. Gaisser, P. Lipari, and T. Stanev. Nucleus-nucleus collisions and

interpre-tation of cosmic-ray cascades. Physical Review D (Particles and Fields), 46 :5013–5025,

December 1992.

[7] T. K. Gaisser and R. K. Schaefer. Cosmic-ray secondary antiprotons - A closer look.

Astro-physical Journal, 394 :174–183, July 1992.

[8] D Maurin, F Donato, R Taillet, and P Salati. Cosmic Rays below Z=30 in a diffusion model :

new constraints on propagation parameters. Astrophys. J., 555(2) :19, jan 2001.

[9] L. C. Tan and L. K. Ng. Parameterization of the invariant cross section in p-p collisions

using a new scaling variable. Physical Review D (Particles and Fields), 26 :1179–1182,

September 1982.

[10] L. C. Tan and L. K. Ng. Calculation of the equilibrium antiproton spectrum. Journal of

Physics G Nuclear Physics, 9 :227–242, February 1983.

Chapitre 7

A fussy revisitation of antiprotons as a tool

for Dark Matter searches

Les antiprotons sont considérés comme une sonde fiable vis à vis de la détection indirecte

de matière noire dans la Voie Lactée. En effet, les données de la collaboration PAMELA ont

permis d’établir des contraintes fortes sur ses propriétés. Toutefois, afin d’exploiter correctement

leur pouvoir contraignant (ou de découverte), et surtout, en prévision de l’extrême précision des

données à venir de la collaboration AMS-02, une grande attention doit être portée aux effets

provenant de leur propagation dans la Voie Lactée. Ces effets, souvent perçus comme étant

sous-dominants, peuvent en fait se révéler très importants.

Nous revisitons le calcul du fond astrophysique d’antiprotons secondaires et du signal

pri-maire issu de l’annihilation de WIMPs, en prenant en compte les effets de la réaccélération

dif-fusive et des pertes d’énergie incluant la composante tertiaire. Nous montrons qu’ils peuvent

modifier les limites actuelles de manière appréciable, même pour de grandes masses de particule

de matière noire. Les données risquent d’être mal interprétées si ces mécanismes ne sont pas

incorporés dans le calcul. Les résultats numériques pour le fond astrophysique sont synthétisés

sous forme de fonctions paramétriques ; les résultats pour la matière noire sont incorporés dans la

nouvelle version du P_ppc4_dmid.

Les résultats de cette analyse sont présentés à travers l’article [9] publié dans la revue

scien-tifiqueJournal of Cosmology and Astroparticle Physics.

A fussy revisitation of antiprotons

as a tool for Dark Matter searches

Mathieu Boudauda1,Marco Cirellib2,Gaëlle Giesenb3,Pierre Salatia4

a LAPTh, Université Savoie Mont Blanc, CNRS,

BP 110, 74941 Annecy-le-Vieux, France

bInstitut de Physique Théorique, CNRS, URA 2306&CEA/Saclay,

F-91191 Gif-sur-Yvette, France

Abstract

Antiprotons are regarded as a powerful probe for Dark Matter (DM) indirect

detec-tion and indeed current data from PAMELA have been shown to lead to stringent

constraints. However, in order to exploit their constraining/discovery power properly

and especially in anticipation of the exquisite accuracy of upcoming data from

AMS-02, great attention must be put into effects (linked to their propagation in the

Ga-laxy) which may be perceived as subleading but actually prove to be quite relevant.

Using a semi-analytic code for rapidity, we revisit the computation of the

astrophysi-cal background and of the DM antiproton fluxes. Like in the fully numeriastrophysi-cal standard

calculations, we include the effects of : diffusive reacceleration, energy losses

inclu-ding tertiary component and solar modulation (in a force field approximation). We

show that their inclusion can somewhat modify the current bounds, even at large DM

masses, and that a wrong interpretation of the data may arise if they are not taken into

account. At the present level of accuracy of the data from P_amela, the inclusion of the

above effects amounts to changing the constraints, with respect to the case in which

they are neglected, of up to about 40% at a DM mass of 1 TeV and 30% at 10 TeV.

When the A_ms-02 level of precision is reached, including them would strengthen

(les-sen) the bounds on the annihilation cross section by up to a factor of 15 below (above)

a DM mass of 300 GeV. The numerical results for the astrophysical background are

provided in terms of fit functions ; the results for Dark Matter are incorporated in the

new release of theP_ppc4_dmid.

1. mathieu.boudaud@lapth.cnrs.fr

2. marco.cirelli@cea.fr

3. gaelle.giesen@cea.fr

7.1 Introduction

The evidence for Dark Matter (DM) comes nowadays from a number of different astrophysical and

cosmological probes, sensitive to its gravitational effects. However, we are still eagerly awaiting

an explicit manifestation of it. A possibility would be detecting anomalous fluxes of cosmic rays

(charged antimatter, photons, neutrinos. . . ), which is the aim of the so-called Indirect Detection

strategy. Such anomalous fluxes could indeed originate from DM pair annihilations or decays in

the Milky Way halo, subsequently propagated to us within the Galactic environment.

In particular, antiprotons are a sensitive probe for DM. Indeed, since the initial proposal [51],

many studies have stressed the importance of this channel, including several recent ones [19,26,

33, 15, 6, 30, 48, 14, 56, 18, 12, 17, 37]. This is both for intrinsic and contingent reasons. An

intrinsic reason is that the production of antiprotons is rather universal in DM models : as long

as DM particles annihilate or decay into quarks or gauge bosons (but also into leptons, thanks to

ElectroWeak corrections, i.e. the emission of EW gauge bosons from the final state particles), ¯p

copiously emerge from the hadronization process. Other reasons are that the determination of the

astrophysical background is relatively under control (at least if compared to other channels) and

that the Galactic propagation of antiprotons can be better modeled than the one of other charged

particles. We will actually come back to these last two points in great detail, as they constitute one

of the main focus of our paper. A contingent reason, on the other hand, is that in other channels

(most notably positrons and gamma rays) sizable excesses have shown up, which cannot be easily

attributed neither to DM nor to known astrophysical processes. Until their origin is clarified, they

greatly limit the robustness of DM analyses based on these channels. Finally, another motivation

stems from the great precision of the ¯pdata already available from the PAMELA satellite and the

even better precision expected soon from AMS-02.

In this context, it is clearly timely to refine previous predictions of antiproton production

from astrophysics and from DM, in order to obtain fluxes as accurate as possible to be compared

with the precise data. This is what we aim to do in this work. In particular, we upgrade previous

computations by incorporating energy losses and diffusive reacceleration, which will be discussed

in detail below. We anticipate that these effects have a sizable impact, especially on the low energy

portion of the spectrum. Hence, they cannot be neglected if one aims at precision predictions.

One should nevertheless keep in mind that other sources of uncertainties could also possibly play

a role, yet to be determined, such as the nuclear antiproton production cross sections or the way

cosmic ray propagation is modeled.

The rest of this paper is organized as follows. In sec.7.2we discuss the main concepts related

to the propagation of antiprotons in the Galactic environment, in particular the phenomena of

energy losses, diffusive reacceleration and, to some extent, solar modulation. In sec.7.3we discuss

the antiproton inputs, both from Dark Matter and from astrophysics. In sec.7.4we derive updated

constraints on Dark Matter (using existing PAMELA data) and updated expected sensitivities

(using projected AMS-02 mock data). Finally, in sec.7.5we conclude.

We provide numerical results in the form of fit functions for the astrophysical fluxes (see

sec.7.3.1) and in the form of a new release of the P_oorP_articleP_hysicistC_{ookbook for}D_ark

Dans le document Recherche indirecte de matière noire à travers les rayons cosmiques d'antimatière (Page 187-192)