THE STATUS OF NEUTRALINO DARK MATTER

Transcription

1 THE STATUS OF NEUTRALINO DARK MATTER BIBHUSHAN SHAKYA CORNELL UNIVERSITY CETUP 2013 Workshop June 25, 2013 Based on hep-ph , with Maxim Perelstein, hep-ph

2 The favorite / most studied dark matter candidate: Lightest Neutralino in Supersymmetry

3 The Path(s) to Dark Matter Identification 3

4 The Path(s) to Dark Matter Identification Latest XENON100 update shows no signal, bounds cut into SUSY parameter space Strong evidence of signal at 130 GeV in the gamma ray spectrum in Fermi LAT data (possible signal at low mass) No superpartners at the LHC so far... But a 125 GeV SM-like Higgs 4

5 The Path(s) to Dark Matter Identification Latest XENON100 update shows no signal, bounds cut into SUSY parameter space Where does neutralino dark matter stand after these developments? Strong evidence of signal at 130 GeV in the gamma ray spectrum in Fermi LAT data (possible signal at low mass) No superpartners at the LHC so far... But a 125 GeV SM-like Higgs 5

6 THE FERMI LINE Fits well to a photon line from dark matter annihilation into γγ or γz Best fit cross section: σv γγ =1.27x10-27 cm 3 s -1 (for Einasto profile) Weniger, arxiv: A fit significance of 5.5σ for data from inner 3 of Galactic Center The long-awaited smoking-gun signature of dark matter annihilation in the galaxy! 6

7 The curse of the continuum (from Cohen, Lisanti, Slatyer, Wacker, arxiv: ) The derived constraints exclude neutralino dark matter as an explanation for the line. 7

8 Why go through a loop when there is something at tree level? Internal Bremsstrahlung (IB) This cross section is enhanced at photon energies close to m χ for kinematic reasons. Known to give a very sharp feature at the kinematic edge (~m χ ). Bringmann, Bergstrom, Edsjo, arxiv: (also Bergstrom, Bringmann, Eriksson, Gustafsson, hep-ph/ , Birkedal, Matchev, Perelstein, Spray, hep-ph/ ) 8

9 Neutralino Dark Matter and Internal Bremsstrahlung Bino dark matter: Annihilates to fermion pair via sfermion exchange, process is helicity suppressed by factor of (m f /m χ ) 2. Addition of a photon in the final state lifts this helicity suppression: can be as large as An extremely efficient way to suppress the continuum while producing a sizable signal! 9

10 Approach Use Fermi data from inner 3 of Galactic Center Scan over MSSM, optimised for bino dark matter, with sleptons (universal mass) within 20 GeV of the neutralino Peak normalization: (consistent fit with contracted NFW profile with slope α=1.3 in the region close to Galactic Center in Weniger s line fit) = 30.3 photons (number that gives best fit in continuum paper) Correct for energy dispersion and energy dependence of effective area of Fermi 10

11 Counting Photons Counts of Pass 7_Version 6 ULTRACLEAN events within 3 of Galactic Center (from Appendix A in Cohen, Lisanti, Slatyer, Wacker, arxiv: ) The Signal : A total of 24 photons in the energy range GeV to GeV Background gives ~7 (best fit falling power law) Can IB from neutralino dark matter provide the rest? 11

12 Counting Photons Number of photons contributed by dark matter in the energy range GeV to GeV. Peaks at ~13 photons at ~145 GeV: contribution from both IB and γz line in the right bins (best case scenario) In black: points with relic density within 2σ of the observed value. 12

13 Counting Photons...and as a function of slepton-neutralino mass difference. Intuition from earlier approximation verified: count increases with degeneracy. 13

14 Photon count seems to be a little low, but OK. What about the shape of the signal? Look at a few benchmark points to see how the shape fits 14

15 Benchmark Point 1 m χ : GeV Bino fraction: 0.99 M sleptons : GeV Ωh 2 : 0.19 N γ (IB) : 4.8 N γ (lines) : 2.0 Significance : 4.0 Pure bino, dominantly IB. Continuum essentially vanishes! 15

16 Benchmark Point 2 m χ : GeV Bino fraction: 0.90 M sleptons : GeV Ωh 2 : N γ (IB) : 1.8 N γ (lines) : 5.1 Significance : -- Bino helps suppress continuum (saturates data at GeV), but no IB since sleptons slightly heavier. Line signal dominates 16

17 Benchmark Point 3 m χ : GeV Bino fraction: 0.91 M sleptons : GeV Ωh 2 : N γ (IB) : 4.5 N γ (lines) : 5.2 Significance : -- Both IB and line signals prominent, gives large number of photons. 17

18 Benchmark Point 4 m χ : GeV Bino fraction: 0.97 M sleptons : GeV Ωh 2 : 0.11 N γ (IB) : 14.7 N γ (lines) : 4.4 Significance : 4.2 Enhance dark matter contribution by a factor of 3 (A steeper profile? Substructure?) to get the same number of photons as best fit line signal : a much better fit, and can get right relic density! 18

19 RECAP Neutralino dark matter can still provide a viable explanation of the Fermi signal! Bino dark matter comes with an efficient continuum suppression mechanism (helicity suppression of main channels), and a sharp feature from IB (if sleptons are approximately degenerate) can explain the Fermi signal, augmented by line contribution from a subdominant wino Relic density in the right ballpark (coannihilation with sleptons +small wino component) Steep halo profiles / O(1) boost from substructure might be needed 19

20 MESSAGE FROM THE LHC No superpartners observed so far SM-like Higgs at 125 GeV ( No significant invisible width: constrains light dark matter, in particular, CDMS signal not compatible with Higgs exchange ) 20

21 Guiding Idea: NATURALNESS 21

22 Natural SUSY: The LHC perspective SM-like Higgs at 125 GeV MSSM Need large loop corrections from stops, sub-percent level fine tuning 22

23 Natural SUSY: The LHC perspective SM-like Higgs at 125 GeV MSSM Need large loop corrections from stops, sub-percent level fine tuning NMSSM Additional contribution to tree level higgs mass λ-susy Push λ ~ 2 and accept Landau pole below GUT scale (Hall, Pinner, Ruderman; hep-ph ) 23

24 Latest XENON100 update sees no dark matter signals Does this have any implications for naturalness in the aforementioned SUSY models? 24

25 Quantifying (EWSB) Fine-tuning Tree level relation for m Z : If terms on r.h.s. are not ~100 GeV, need cancellations to make things work. Fine-tuning! Calculate sensitivity to small changes in Lagrangian parameters: In general, larger µ gives greater fine-tuning. 25

26 Spin independent scattering h i

27 Spin independent scattering h i Direct detection cross section depends only on gaugino masses and parameters in the Higgs sector Ignore this contribution (usually subdominant, only need an approximate lower bound for the cross section) Scan parameters: MSSM: µ, m A, M 1, M 2, tanβ NMSSM, λ-susy: µ, M 1, M 2, tanβ, κ, λ, A λ, A κ 27

28 The Approach Define Lagrangian parameters independently at EW scale (ie assume no relations such as unification), scan over parameters (allowed to be negative) Ignore accidental cancellations: want to make general statements true in most of parameter space Ignore relic density (some exceptions) Other Requirements: neutralino LSP; charginos heavier than 103 GeV; light neutralinos satisfy experimental constraint on Z invisible width; Higgs sector: MSSM: set mass of lighter higgs to 125 GeV; NMSSM / λ-susy: require a non-singlet Higgs with tree-level mass GeV, physical Higgs masses nontachyonic (no additional collider constraints imposed) 28

29 MSSM 29

30 MSSM XENON100 bound 30

31 MSSM XENON100 bound Pure gaugino: requires µ to be raised relative to M 1 or M 2. fine tuned! Pure higgsino: Need mass ~ TeV to give the right relic density è µ~tev è < 1% tuned! 31

32 MSSM Lines: analytic bounds (see ) ( see also Amsel, Freese, Sandick, arxiv 1108:0448 ) Red: M LSP > 1 TeV Green: M LSP > 100 GeV Cyan: M LSP > 10 GeV 32

33 MSSM XENON100 (2011) XENON100 (2012) XENON 1T Red, green, blue: FT<10,100,1000 M LSP > 50 (400) GeV is worse than 10% (1%) fine-tuned. XENON1T can probe entire MSSM parameter space down to 1% tuning 33

34 MSSM with negative/complex parameters Can get cancellations, destroys aforementioned correlations. ( But these cancellations themselves require a fine-tuning of parameters ) With (left) and without (right) points with accidental cancellations in the cross section. Correlation restored!

35 Dark Matter in NMSSM, λ-susy New singlet superfield S. Fermionic component of S gives an additional neutralino: singlino. Mixes with the four MSSM neutralinos. CP even singlet higgs: mixes with higgs doublet. 35

36 Dark Matter in NMSSM, λ-susy H physical = s j H j, H j = {H u, H d, S} χ physical = n j χ j, χ j = {B, W 3, H u0, H d0, S} 36

37 Dark Matter in NMSSM, λ-susy H physical = s j H j, H j = {H u, H d, S} χ physical = n j χ j, χ j = {B, W 3, H u0, H d0, S} 125 GeV higgs must be mostly doublet } large cross section if gaugino-higgsino λ~0.6 for 125 GeV higgs, large contribution if higgsino-singlino Are deviations from gaugino-higgsino or higgsino-singlino fine-tuned? 37

38 Dark Matter in NMSSM, λ-susy Similar insight: large µ is fine-tuned In λ-susy: fine-tuning suppressed by a factor of (λ/g) 2 NMSSM λ-susy 38

39 Dark Matter in NMSSM, λ-susy Are deviations from gaugino-higgsino or gaugino-singlino fine-tuned? Pure gaugino or gaugino-singlino: requires lifting µ far above M 1, M 2 Higgsino: relic density too low unless TeV scale Singlino: Large λ introduces large mixing between higgsinos and singlino. Beating this mixing by lifting the mass scales requires large µ and is fine-tuned. 39

40 Dark Matter in NMSSM, λ-susy NMSSM λ-susy (Points with accidental cancellations removed) Again, a clear correlation between lower direct detection cross section and fine-tuning. 40

41 Dark Matter in NMSSM, λ-susy NMSSM λ-susy Red, green, blue, yellow: FT is 41

42 Dark Matter in NMSSM, λ-susy NMSSM λ-susy Red, green, blue, yellow: FT is NMSSM tuned to ~10% or worse Natural to evade XENON bound in λ-susy XENON1T will probe both down to 1% level tuning 42

43 SUMMARY Neutralino Dark Matter: Messages from the Most Recent Experimental Results Indirect Detection: Fermi 130 GeV signal is (pushing things to the limit) compatible with internal bremsstrahlung from mostly bino dark matter, continuum under control Collider+Direct Detection: LHC results prefer nonminimal supersymmetric models (NMSSM, λ-susy). Null results at XENON100 require ~10% fine-tuning in MSSM and NMSSM, but do not constrain λ-susy. XENON1T will probe all three down to sub-percent level tuned regions. STAY TUNED! 43