DAMA detection claim is still compatible with all other DM searches 1

We show that the annual modulation signal observed by DAMA can be reconciled with all other negative results from dark matter searches with a conventional halo model for particle masses around 5 to 9 GeV. We also show which particular dark matter stream could produce the DAMA signal. Given the country which hosts this conference, TAUP2005, I was tempted to change the title into a well known spanish aphorism “Los muertos que vos matais gozan the buena salud”. Although the DAMA signal may not be entirely in“good health”, the point of this talk, based on Ref. [1], is to show that, even with the usual assumptions on the dark halo of our galaxy, the DAMA claim has not yet been rejected by other experimental results. The DAMA collaboration [2], has found an annual modulation in its data compatible with the signal expected from dark matter (DM) particles bound to our galactic halo. Other such experiments, CDMS [3, 4], EDELWEISS [5, 6], and CRESST [7, 8], have not found any signal from weakly interacting massive particles (WIMPs). It has been difficult to reconcile a WIMP signal in DAMA with the other negative results [9]. In Ref. [1] we showed that it is possible to have a dark matter signal above the WIMP speed threshold for DAMA and below the WIMP speed threshold for CDMS and EDELWEISS, so that the positive and negative detection results can be compatible. Our idea is based on attributing the DAMA signal to scattering off Na, instead of I, and can be tested in the immediate future by detectors using light nuclei, such as CDMS-II (using Si) and CRESST-II (using O). We found: (1) that with the standard dark halo model there is a solution for WIMP masses about 5-9 GeV and WIMP-proton scattering cross section of about 1 femtobarn (10−39 cm2), and (2) that this region of solutions can be enlarged if a dark matter stream is suitably added to the standard dark halo. DM streams have been considered before [13], but we looked for a stream with speed above threshold for Na in DAMA and below threshold for Ge in CDMS and with the right arrival direction to produce the annual modulation seen by DAMA. The stream should come from the general direction of the Galactic rotation (it cannot be the Sagittarius stream). See Figs. 1 and 2. The region in point (1) could certainly also be enlarged by considering more general halo models, even in the absence of dark matter streams (see e.g. the models in [10]). Light neutralinos as WIMPs with masses as low as 2 GeV [11] or, with updated bounds, 6 GeV [12] have been considered, but their cross sections are about one order of magnitude smaller than those needed here. In Ref [1] we proceeded in a purely phenomenological way in choosing the WIMP mass and cross section. For simplicity we concentrated on spin-independent cross sections only. 1 Talk given at TAUP2005, Sept. 10-14 2005, Zaragoza (Spain) Figure 1. Comparison of the DAMA annual modulation region with other direct detection bounds for spin-independent WIMP-proton interactions (a) (left panel) for just the conventional dark halo model, and (b) (right panel) this halo model with the addition of a DM stream with density 3% of the conventional local halo density, heliocentric arrival direction of ecliptic coordinates (λstr, βstr) = (340 ◦, 0◦), and heliocentric speed of 900 km/s. In the hatched region, the WIMP-proton cross section σp at WIMP mass m reproduces the DAMA annual modulation results at the 90% and 3σ C.L. (inner densely hatched region and outer hatched region, respectively). The region above each other line is excluded at 90% C.L. by the corresponding experiment (CDMS-Soudan is denoted by CDMS-S). In (a), we use the 2-4 and 6-14 keVee DAMA bins; in (b), the 2-6 and 6-14 keVee bins. In (b) the gap in the DAMA modulation region is due to our requirement that χmin < 2 (see Ref. [1]). The experimental upper limits change when the stream is included. Our basic idea is very simple. The minimumWIMP speed required to produce a nuclear recoil