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Kev Scale Sterile Neutrino Dark Matter keV scale sterile neutrino Dark Matter Fedor Bezrukov The University of Manchester Invisibles18 Workshop 3-7 September 2018 Karlsruhe Institute of Technology (KIT) Outline Introduction X-ray observations nMSM Beyond nMSM Laboratory searches Conclusions Outline 1 SM, Cosmology and sterile neutrinos 2 X-ray observations 3 Pure nMSM – just three sterile neutrinos 4 Other DM generation mechanisms 5 Laboratory searches Outline Introduction X-ray observations nMSM Beyond nMSM Laboratory searches Conclusions Standard Model – describes nearly everything Three Generations of Matter (Fermions) spin ½ CDHSW I II III Experimental CHORUS NOMAD NOMAD mass→ 2.4 MeV 1.27 GeV 171.2 GeV 0 NOMAD 0 KARMEN2 CHORUS charge→ ⅔ ⅔ ⅔ 0 10 MiniBo oNE u c t g Bugey LSND 90 /99 % name→ up charm top gluon Left Right Left Right Left Right Einstein problems: SuperK 90 /99 % CHOOZ 104 MeV 4.2 GeV 0 MINOS 4.8 MeV –3 10 K2K -⅓ -⅓ -⅓ 0 + all solar 95% γ Cl 95% d s b ] KamLAND down strange bottom photon 2 95% Left Right Left Right Left Right Quarks gravity [eV SNO 0 eV 0 eV 0 eV 91.2 GeV >114 GeV Laboratory 2 0 –6 95% m 10 0 0 0 0 0 Super-K e νμ ντ ∆ 95% ν Z 0 H electron muon tau weak Higgs Ga 95% neutrino force boson neutrinoLeft Left neutrinoLeft 105.7 MeV 1.777 GeV 80.4 GeV ? Neutrino 0.511 MeV spin 0 –9 ± 10 νe↔ν X -1 -1 -1 ± 1 νµ↔ν τ ν ↔ν μ e τ e τ W ν ↔ν e µ muon tau weak electron force All limits are at 90%CL Left Right Left Right Left Right Leptons Bosons (Forces) spin 1 oscillations unless otherwise noted 10 –12 10 –4 10 –2 10 0 10 2 tan2θ Describes Cosmology http://hitoshi.berkeley.edu/neutrino all laboratory experiments ? Baryon asymmetry of the Universe – electromagnetism, nuclear processes, etc. ? Dark Matter all processes in the evolution of the Universe after the Big Bang ? Inflation Nucleosynthesis (T < 1 MeV, t > 1sec) ? Dark Energy Outline Introduction X-ray observations nMSM Beyond nMSM Laboratory searches Conclusions Sterile neutrino as DM Nearly always present in SM extensions Feebly interacting Quite stable if light (keV scale) Outline Introduction X-ray observations nMSM Beyond nMSM Laboratory searches Conclusions Outline 1 SM, Cosmology and sterile neutrinos 2 X-ray observations 3 Pure nMSM – just three sterile neutrinos 4 Other DM generation mechanisms 5 Laboratory searches Outline Introduction X-ray observations nMSM Beyond nMSM Laboratory searches Conclusions DM properties – Radiative decay Leads to constraints from the X-ray observations Main decay channel N1 n t > tUniverse - easy: q Z 5 1 n¯ 2 4 10keV q < 3:3 10− M n × 1 not visible, really. Second decay channel: N ng 1 ! g 2 5 27 q1 M1 1 + Γ 5:5 10− 10 5 1keV s− q1 W ' × − N n 1 e; m;t Monochromatic: Eg = M1=2 We should see an X-ray ( keV) W + line following the DM distribution∼ in N1 n q1 g the sky Outline Introduction X-ray observations nMSM Beyond nMSM Laboratory searches Conclusions Bounds for the N1 – DM sterile neutrino 8 10− Excluded by X-ray observations ) 1 a q 10 10 2 − ( 2 sin a ∑ 12 10− 14 10− 1 2 5 10 20 50 M1, keV Universal constraint for all DM models [Boyarsky, Ruchayskiy, Shaposhnikov’09] Outline Introduction X-ray observations nMSM Beyond nMSM Laboratory searches Conclusions Bounds from observed structure in the Universe Look at the compact object with DM (dwarf spheroidals) Check that sterile neutrinos can “fit” there – Pauli blocking MDEG > 0:5keV Stricter bound – phase space density arguments M > 1 2keV − Tremaine, Gunn 79; Gorbunov, Khmelnitsky, Rubakov 08; Boyarsky, Ruchayskiy, Iakubovskyi 08 Light sterile neutrino being relativistic after generation (warm) provides cut off in the structure formation at smaller (sub-Mpc) scales. Presence of this cut off can be searched by the analysis of the Lyman-a absorption line of the intergallactic hydrogen. The bound depends on velocities of the neutrinos, not on masses – bound depends on distribution function – production mechanism Boyarsky, Lesgourgues, Ruchayskiy, Viel’08; Viel, Becker, Bolton, Haehnelt’13; Baur et.al.17 Outline Introduction X-ray observations nMSM Beyond nMSM Laboratory searches Conclusions Bounds for the N1 – DM sterile neutrino 8 10− Excluded by X-ray observations ) 1 a q 10 10 2 − ( 2 sin a ∑ 12 10− Excluded by phase space analysis 14 10− 1 2 5 10 20 50 M1, keV Universal constraints for all models 3 Dataset Exposure χ2/d.o.f. Line position Flux ∆χ2 6 2 [ksec] [keV] 10− cts/sec/cm +1.6 M31 ON-CENTER 978.9 97.8/74 3.53 0.025 4.9 1.3 13.0 ± − M31 OFF-CENTER 1472.8 107.8/75 3.53 0.03 < 1.8 (2σ) ... ±+0.044 +2.6 PERSEUS CLUSTER (MOS) 528.5 72.7/68 3.50 0.036 7.0 2.6 9.1 − +3− .1 PERSEUS CLUSTER (PN) 215.5 62.6/62 3.46 0.04 9.2 3.1 8.0 ±+0.019 +2.2 − PERSEUS (MOS) 1507.4 191.5/142 3.518 0.022 8.6 2.3 (Perseus) 25.9 Outline Introduction X-ray observations nMSM − Beyond−+1nMSM.4 Laboratory searches Conclusions +M31ON-CENTER 4.6 1.4 (M31) (3 dof) − BLANK-SKY 15700.2 33.1/33 3.53 0.03 < 0.7 (2σ) ... ± TABLE I: Basic properties of combinedSearch observations used for in this paper. the Second line column denotesin X-rays the sum of exposures of individual observa- tions. The last column shows change in ∆χ2 when 2 extra d.o.f. (position and flux of the line) are added. The energies for Perseus are quoted in the restUnidentified frame of the object. line at 3.5 keV in X-rays 10.00 0.36 M31 ON-center 0.34 M31 ON-center No line at 3.5 keV 0.32 1.00 0.30 0.28 [cts/sec/keV] 0.10 [cts/sec/keV] 0.26 0.24 Normalized count rate Normalized count rate 0.22 0.01-2 -2 1⋅10 No line at 3.5 keV 1⋅10 No line at 3.5 keV -3 8⋅10-3 8⋅10 Line at 3.5 keV -3 6⋅10 6⋅10-3 -3 4 10 -3 ⋅ 4⋅10 2⋅10-3 2⋅10-3 0⋅100 [cts/sec/keV] [cts/sec/keV] 0 -3 0⋅10 Data - model -2⋅10 Data - model -3 -4⋅10-3 -2⋅10 -6⋅10-3 -4⋅10-3 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 3.0 3.2 3.4 3.6 3.8 4.0 Energy [keV] Energy [keV] seen by two different satellites (XMM-Newton and FIG. 1: Left: Folded count rate (top) and residuals (bottom) for the MOS spectrum of the central region of M31. Statistical Y-errorbarsonthe top plot are smallerChandra) than the point size. The line around 3.5 keV is not added,hencethegroupofpositiveresiduals.Right:zoomontotheline region. the line has proper redshift for different sources with such a largethe exposure intensity requires special is consistent analysis (as de- theThe observed Dark brightness Matter of a decaying profiles DM line should be pro- scribed in [16]). This analysis did not reveal any line-like portional to the dark matter column density DM = ρDMdℓ – residuals in the range 3.45 3.58 keV with the 2σ upper bound integral along the line of sight of the DM densityS distribution: the line7− is2 absent in the blanc sky observations ! on the flux being 7 10− cts/cm /sec.Theclosestdetected line-like feature (∆×χ2 =4.5)isat3.67+0.10 keV, consistent 0.05 cts Ωfov 3 − 6 with the instrumental Ca Kα line. FDM 2.0 10− 2 (1) Bulbul, Markevitch, Foster, Smith et.al.’14, Boyarsky,≈ × Ruchayskiy,cm2 sec 500 arcmin × " # 29 · CombinedIakubovskyi, fit of M31 + Perseus. Franse’14Finally, we have performed DM 10 s keV S 2 . asimultaneousfitoftheon-centerM31andPerseusdatasets 500 M /pc τDM mDM " # " # (MOS), keeping common position of the line (in the rest- ! frame) and allowing the line normalizations to be different. The line improves the fit by ∆χ2 =25.9 (Table I), which M31 and Perseus brightness profiles. Using the line flux constitutes a 4.4σ significant detection for 3 d.o.f. of the center of M31 and the upper limit from the off-center observations we constrain the spatial profile of the line. The Results and discussion. We identified a spectral feature at DM distribution in M31 has been extensively studied (see an +0.019 E =3.518 0.022 keV in the combined dataset of M31 and overview in [13]). We take NFW profiles for M31 with con- − Perseus that has a statistical significance 4.4σ and does not centrations c =11.7 (solid line, [22]) and c =19(dash-dotted coincide with any known line. Next we compare its properties line). For each concentration we adjust the normalization so with the expected behavior of a DM decay line. that it passes through first data point (Fig. 2). The c =19 profile was chosen to intersect the upper limit, illustratingthat the obtained line fluxes of M31 are fully consistent with the density profile of M31 (see e.g. [22, 24, 25] for a c =19 22 3 Previously this line has only been observed in the PN camera [9]. model of M31). − Outline Introduction X-ray observations nMSM Beyond nMSM Laboratory searches Conclusions Sterile neutrino N1 parameters would be NR production ( 8 10− m j a = Excludedj 0) by X-ray observations ) 1 a q 10 10 2 − ( 2 sin a ∑ 12 10− Excluded by phase space analysis 14 10− 1 2 5 10 20 50 M1, keV Outline Introduction X-ray observations nMSM Beyond nMSM Laboratory searches Conclusions Current status of 3.5 keV line and future Not seen in Seen in Coma, Virgo and Perseus, Coma, and Ophiuchus clusters Ophiuchus galaxy clusters Galaxy center Galaxy center Stacked galaxies Stacked clusters Dwarf spheroidals M31 (Adromeda galaxy) Bullet cluster Future High resolution X-ray missions XARM LYNX Athena+ (2030?) Outline Introduction X-ray observations nMSM Beyond nMSM Laboratory searches Conclusions Outline 1 SM, Cosmology and sterile neutrinos 2 X-ray observations 3 Pure nMSM – just three sterile neutrinos 4 Other DM generation mechanisms 5 Laboratory searches Outline Introduction X-ray observations nMSM Beyond nMSM Laboratory searches Conclusions Summary of sterile neutrino Dark Matter constraints Dark Matter stay like DM Decay constraints – small enough radiative decay width (X-ray observations) always there behave like
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