Fullcalculation ofclum piness boostfactors forantim attercosm ic raysin the lightofCD M N -body sim ulation results Abandoning hope in clum piness enhancem ent?

Context. Anti-proton and positron G alactic cosm icray spectra aream ong thekey targetsforindirectdetection ofdark m atter.Theboostfactors,correspondingtoan enhancem entofthesignal,and linked totheclum pinesspropertiesofthe dark m atterdistribution,havebeen taken ashigh asthousandsin thepast.Thedram aticim pactoftheseboostfactors forindirectdetection ofantiparticles,forinstancewith thePAM ELA satelliteorthecom ing AM S-02 experim ent,asks fortheirdetailed calculation. Aim s. W e takeinto accountthe state-of-the-artresultsofhigh resolution N-body dark m attersim ulationsto calculate the m ost likely energy dependent boost factors,which are linked to the cosm ic ray propagation properties,for anti- protonsand positrons.Theresultsfrom extrem e,butstillpossible,congurationsoftheclum py dark m attercom ponent are also discussed. M ethods. Starting from the m ass and space distributions ofsub-halos,the anti-proton and positron propagators are used to calculate them ean valueand thevarianceoftheboostfactorfortheprim aryuxes.W etakeadvantageofthe statisticalm ethod introduced in Lavalle etal.(2007)and cross-check the resultswith M onte Carlo com putations. Results. By spanning som e extrem e congurations ofsub-halo and propagation properties,wend that the average contribution oftheclum psisnegligible com pared to thatofthesm ooth dark m attercom ponent.Dark m atterclum ps donotlead toenhancem entofthesignals,unlessthey aretaken with som eextrem e(unexpected)properties.Thisresult isindependentofthe nature ofthe self-annihilating dark m attercandidate considered,and providesprecise estim ates ofthe theoreticaland thestatisticaluncertaintiesofthe antim atterux from sub-halos. Conclusions. Spectraldistortionscan stillbeexpected in antim atterux m easurem ents,butscenariosinvokinglargeand even m ild clum pinessboostfactors are strongly disfavoured by ouranalysis.Som e very extrem e congurationscould stilllead to large enhancem ents,e.g.(i)very sm allclum pswith m asses . 10 6 Mfollowing a Mm assdistribution with � & 2,highly concentrated with internal rproles with � & 1:5,and spatially distributed according to the sm ooth com ponent;or (ii) a big sub-halo ofm ass & 10 7 Mwithin a distance of . 1 kpc from the Earth.However,