TeV dark matter in the disk F. Nozzoli To cite this version: F. Nozzoli. TeV dark matter in the disk. Astroparticle Physics, Elsevier, 2011, 35 (4), pp.165. 10.1016/j.astropartphys.2011.07.004. hal-00806360 HAL Id: hal-00806360 https://hal.archives-ouvertes.fr/hal-00806360 Submitted on 30 Mar 2013 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Accepted Manuscript TeV dark matter in the disk F. Nozzoli PII: S0927-6505(11)00136-8 DOI: 10.1016/j.astropartphys.2011.07.004 Reference: ASTPHY 1616 To appear in: Astroparticle Physics Received Date: 8 April 2011 Revised Date: 9 July 2011 Accepted Date: 14 July 2011 Please cite this article as: F. Nozzoli, TeV dark matter in the disk, Astroparticle Physics (2011), doi: 10.1016/ j.astropartphys.2011.07.004 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. 1 2 TeV dark matter in the disk 3 4 F. Nozzoli 5 Dipartimento di Fisica, Universit´adegli Studi di Roma “Tor Vergata” 6 Via della Ricerca Scientifica 1, I-00133 Rome, Italy 7 8 9 10 11 12 Abstract 13 14 DAMA and CoGeNT annual modulation data and, CDMS-II, EDELWEISS-II, CRESST excesses of events over the expected 15 background are reanalyzed in terms of a dark matter particle signal considering the case of a rotating halo. It is found that the 16 configurations of very high mass dark matter particles in a corotating cold flux are favored by data. A similar high-mass/low- 17 velocity solution could be of interest in the light of the positron/electron excess measured by Pamela and Fermi in cosmic rays. 18 19 Keywords: dark matter experiments, dark matter theory 20 21 LS R − 22 1. Introduction ~v⊙ = ~v⊙ ~vLS R = (10.0, 5.25, 7.17) km/s is the Sun veloc- ≃ 23 ity relative to the Local Standard of Rest (LSR), and ~vLS R 24 Since 1996 the sodium iodide experiments of DAMA col- (0, 220 ± 30, 0) km/s [22]. Therefore assuming a rotating dark 25 laboration (DAMA/NaI and DAMA/LIBRA) have measured an matter halo (~vDM , 0) one can write: ~vLS R − ~vDM ≃ (0, vlag, 0), 26 annual modulation of the single-hit counting rate which has the where vlag is the LSR velocity with respect to the dark matter 27 proper features expected for a dark matter induced signal [1]. flux. Fixing vlag = v0 ≃ 220 km/s the eq. (1) provides the 28 More recently, other experiments (CoGeNT [2], CDMS-II isothermal halo model, however, in this analysis, the v0 and vlag 29 [3, 4], EDELWEISS-II [5], CRESST [6]) have reported a pre- parameters are kept free and it is important to note that config- 30 liminary observation of some excess of events relative to the urations of v0 and vlag that are far from the isothermal halo ones 31 expected backgrounds; in particular, the CoGeNT experiment can be physically meaningful 2. 32 has reported the possible presence of a modulated signal in the To avoid parameter proliferation, only the case of dominant 33 data collected during fifteen months [7]. spin independent interaction for elastically scattering dark mat- 34 The DAMA and CoGeNT annual modulation signals and the ter will be considered and the effects of uncertainties in the val- 35 other experiment excesses, if interpreted as dark matter with ues adopted for other parameters (quenching factor, form fac- 36 dominant spin independent interaction1 in the isothermal halo tor, possible presence of channeling, etc..) will be neglected3. 37 model, implies that dark matter particles possess a mass in the Therefore a four-parameter space (v , v , M , ξ σ ) will be 38 0 lag W 0 p 39 range of 5-15 GeV and an elastic scattering cross section with considered here, where MW is the particle mass, σp is the proton nucleons in the order of 10−4 pb [13, 14, 15, 16, 17, 18, 19, 20, cross section and ξ = ρDM is the density of the considered 40 0 0.3GeV/cm3 41 21]. dark matter component4 in units of 0.3 GeV/cm3. 42 In this paper the same data are reanalyzed relaxing the hy- 43 pothesis of isothermal halo model, however it is assumed that 2. Experimental observables 44 the dark matter local velocity distribution can still be approxi- mated as a single Maxwellian flux: 45 In this section the data used in the analysis are listed for each 46 2 experiment under consideration: 47 1 − ~v+~v /v2 f (~v,~v ) = e ( e) 0 . (1) 48 e 3/2 πv2 2.1. DAMA/NaI and DAMA/LIBRA 49 0 50 The total exposure of 1.17 ton×yr of NaI(Tl) provides three Here the Earth velocity relative to the dark matter flux is 51 LS R complementary observables: given by: ~v = ~v⊕(t) + ~v⊙ − ~v = ~v⊕(t) + ~v + ~v − ~v ; 52 e DM ⊙ LS R DM 53 where: ~v⊕(t) is the Earth velocity in the solar system frame; 54 2In particular, it is plausible that the whole dark halo has a not negligible an- 55 gular momentum [23, 24, 25], moreover ΛCDM halo simulations with baryons [email protected] ∼ / ∼ / 56 Email address: () predict also a corotating dark disk having v0 50 km s and vlag 50 km s 1Many other possible Dark Matter candidates have been suggested for the [26, 27] 57 interpretation of DAMA and of the other direct detection experiments. Some 3it is important, however, to keep in mind the possible relevant role of some 58 examples are (beyond the WIMPs class): axion-like particles [8], sterile neu- of these uncertainties. 4 59 trino or light dark matter [9], leptophilic dark matter [10], inelastic dark matter ξ0 << 1 could be possible if the considered dark matter population is a 60 [11], mirror matter [12], etc. subdominant component of a multicomponent dark matter halo. 61 Preprint submitted to Astroparticle Physics July 9, 2011 62 63 64 65 1 a) A modulated time behavior in the 2-6 keV window (see data in fig. (3) taken from fig. (4) of ref. [1]) 2 300 3 b) The energy distribution of the observed modulation ampli- 4 tude, assuming a fixed phase t0 = 152.5 d (see data in fig. (4) 5 taken from fig. (6) of ref. [1]). In the following analysis the 250 6 data in the 2-8 keV interval will be considered. 7 c) The energy distribution of the unmodulated counting rate 8 (see data in fig. (5) taken from fig. (27) of ref. [28]). This 200 9 energy distribution provides a limit for the sum of background 10 and unmodulated dark matter induced signal and therefore the 11 × 150 limit of 0.25 cpd/(kg keV) for the possible unmodulated dark (km/s) 0 12 matter induced signal, is cautiously assumed in the following v 13 analysis; this choice allows large space for the presence of a 100 14 low energy background component in the measured counting 15 rate. 16 50 17 18 2.2. CoGeNT 19 The data of fig. (1) and (4) of ref. [7] are considered for 0 20 the exposure of 330g × 442d collected by CoGeNT germanium 0 50 100 150 200 250 300 350 400 450 500 v (km/s) 21 detector. lag 22 The annual modulation data of fig. (4) of ref. [7] have been 23 considered for the evaluation of the dark matter allowed con- Figure 1: Horizontally hatched areas: allowed configurations (90% and 24 99% C.L.) for unconstrained DAMA/NaI + DAMA/LIBRA data. Cross figurations in the hypothesis that this signal is induced by dark hatched areas: allowed configurations (90% and 99% C.L.) for DAMA/NaI 25 matter elastic scattering; however the data of the inset of fig. (1) + DAMA/LIBRA data combined with CoGeNT, CDMS-II and CRESST data. 26 of ref. [7] is considered for the evaluation of the upper limit. Filled area: configurations having a C.L. better than the one of isothermal halo 27 model (v0 = 220 km/s and vlag = 220 km/s) for DAMA/NaI + DAMA/LIBRA 28 data unconstrained. 2.3. CDMS-II and EDELWEISS-II 29 30 The exposure of 969 kg × d collected by CDMS-II germa- 31 nium detectors [4] is considered. Eleven events were observed recoil are induced by dark matter elastic scattering will be con- 32 within the recoil acceptance region passing the rejection cuts in sidered; this example will be generically addressed as CaWO4. 33 the 10-150 keV energy range. The neutron background is not 34 able to explain the CDMS-II measured events; however some 35 of these events could be ascribed to surface background, in par- 3. Parameter estimation 36 ticular for the low energy region.