Probing Light Dark Matter at the LHC

Probing Light Dark Matter at the LHC Lian-Tao Wang University of Chicago Exploring Low-mass Dark Matter Candidates PACC, UPITT Nov. 14, 2011

Searching for WIMP dark matter DM DM Indirect detection: AMS2, PAMELA, Fermi-LAT... Collider searches: LEP LHC Tevatron SM Direct detection: CDMS CoGeNT COUPP CRESST DAMA XENON...

Searching for WIMP dark matter DM DM Indirect detection: AMS2, PAMELA, Fermi-LAT... Collider searches: LEP LHC Tevatron This talk. SM Direct detection: CDMS CoGeNT COUPP CRESST DAMA XENON...

Candidates, models, scenarios... Different spin different Z 2 LSNPs: SUSY LSP Extra Dim. LKP T-parity LTP LZP L...P Z 3

Candidates, models, scenarios... Model independent Effective operator Different spin different Z 2 LSNPs: SUSY LSP Extra Dim. LKP T-parity LTP LZP L...P Z 3 Extended Models dark sectors

This talk - Dark matter part of a rich TeV NP scenario. Search for SUSY dark matter, and measure its properties (Highlight challenges). - Connection between collider searches and direct detection, focusing on light dark matter. Effective operator. Searching for the mediator. - Signals from new model extensions. (brief)

Search for SUSY dark matter

Discovering dark matter: - DM candidate embedded in an extended TeV new physics scenario, such as SUSY. DM candidate Lightest superpartner (LSP) Neutral and stable. - Other new physics scenarios (extra-dim, compositeness...) similar.

Could be challenging to identify. - For example: the well tempered scenario. Nearly degenerate NLSP and LSP. soft l... N. Arkani-Hamed, A. Delgado, G. Giudice, hep-ph/06041 M A = 300 0.2 GeV tan β = NLSP LSP 0.1 LSP ( µ -M 1 )/ µ 0-00 -500 0 500 00-0.1-0.2 µ(gev) See also, S. Gori, P. Sechwaller, C. Wagner, 13.4138

LHC prospect for well tempered DM G. Giudice, T. Han, K. Wang and LTW, 04.4902 " (fb) 1 LHC at 14 TeV. Soft muon: 3 GeV < p T < GeV -1 - Light-ish gluino or squark. Discovery from jets+met. -2 125 130 135 140 145 150 M 2 (GeV) soft leptons well tempered, long term. FIG. : (a) Statistical significance S/ B of the g g signal for 1 fb 1 luminosity for 4j + E T + µ ± events - No light gluino or squark, very hard. with M 3 = 500 GeV. (b) Soft muon signal cross sections for 4j + E T + µ ± µ ± with M 3 =1 TeV. VBF, Drell-Yan. Given the encouraging results for an isolated soft lepton above, we are thus motivated to consider two like-sign soft muons as specified in Eq. (22) in the final state

In general, hard to interpret. Model space LHC data - After the discovery, we can derive some basic properties, such as whether the new particles are colored or not, whether they decay to leptons, and so on. - Many possible interpretations. Degeneracies! Quantum number, mass, spin... For example: in supersymmetry, bino vs wino, squark vs gluino... Arkani-Hamed, Kane, Thaler, and Wang, JHEP 0608:070,2006.

Possible degeneracies in: - The identity of new physics particles. For example: q, g,... q, g,... Two different SUSY spectra. W B Identity swap, hard to distinguish B W - In addition M LSP. Spin. - Crucial to combine with direct/indirect detections

Possible degeneracies in: - The identity of new physics particles. For example: q, g,... q, g,... Two different SUSY spectra. W B Identity swap, hard to distinguish B W - In addition M LSP. Spin. - Crucial to combine with direct/indirect detections Difficult task, but accomplishable.

Probing light dark matter, collider searches in connection with direct detection

Probe NP with direct detection -39 XENON 0, 14.2549 DAMA/Na ] 2 WIMP-Nucleon Cross Section [cm -40-41 -42-43 CoGeNT CRESST CDMS DAMA/I EDELWEISS XENON0 (20) -44 XENON0 (2011) Buchmueller et al. -45 6 7 8 9 20 30 40 50 0 200 300 400 00 2 WIMP Mass [GeV/c ]

Probe NP with direct detection -39 XENON 0, 14.2549 DAMA/Na ] 2 WIMP-Nucleon Cross Section [cm -40-41 -42-43 CoGeNT CRESST CDMS DAMA/I EDELWEISS XENON0 (20) -44 XENON0 (2011) Buchmueller et al. -45 6 7 8 9 20 30 40 50 0 200 300 400 00 2 WIMP Mass [GeV/c ] - M WIMP = O( 2 ) GeV. - DM of Typical scenarios: SUSY LSP,...

Probe NP with direct detection -39 XENON 0, 14.2549 DAMA/Na ] 2 WIMP-Nucleon Cross Section [cm -40-41 -42-43 CoGeNT CDMS DAMA/I EDELWEISS XENON0 (20) -44 XENON0 (2011) Buchmueller et al. -45 6 7 8 9 20 30 40 50 0 200 300 400 00 2 WIMP Mass [GeV/c ]

Probe NP with direct detection -39 XENON 0, 14.2549 DAMA/Na ] 2 WIMP-Nucleon Cross Section [cm m WIMP : O(1-) GeV Much larger σ dir -40-41 -42-43 -44 CoGeNT CDMS XENON0 (2011) DAMA/I EDELWEISS XENON0 (20) Buchmueller et al. -45 6 7 8 9 20 30 40 50 0 200 300 400 00 2 WIMP Mass [GeV/c ]

Probe NP with direct detection -39 XENON 0, 14.2549 DAMA/Na ] 2 WIMP-Nucleon Cross Section [cm m WIMP : O(1-) GeV Much larger σ dir -40-41 -42-43 -44 CoGeNT CDMS XENON0 (2011) DAMA/I EDELWEISS XENON0 (20) Buchmueller et al. -45 6 7 8 9 20 30 40 50 0 200 300 400 00 2 WIMP Mass [GeV/c ] - Collider searches provide stronger bounds/potential

Basic channel - Pair production + additional radiation. γ, jet DM p χ DM DM SM p χ DM jet, or γ+ E T - Large Standard Model background, about times the signal. - Very challenging.

Effective operator approach DM SM DM

Effective operator approach DM momentum exchange q 0 MeV << m Φ effectively, SM DM

Effective operator approach DM momentum exchange q 0 MeV << m Φ effectively, SM DM Use colliders to constrain and probe the same operator

Recent studies. 1. Beltran, Hooper, Kolb, Krusberg, Tait, 02.4137 2. Goodman, Ibe, Rajaraman, Shepherd, Tait, Yu, 05.1286 3. Bai, Fox, Harnik, 05.3797 4. Goodman, Ibe, Rajaraman, Shepherd, Tait, Yu, 08.1783 5. Goodman, Ibe, Rajaraman, Shepherd, Tait, Yu, 09.0008 6. Fox, Harnik, Kopp, Tsai, 13.0240 7. Fortin, Tait, 13.3289 8. Cheung, Tseng, Yuan, 14.5329 9. Fox, Harnik, Kopp, Tsai, 19.4398. Goodman, Shepherd, 1111.2359

For example, 08.1783 Goodman, Ibe, Rajaraman, Shepherd, Tait, Yu, 08.1783-38 -39 CRESST monojet ) 2 (cm SI! N -40-41 -42 CoGeNT favored D1 LHC reach CoGeNT D11 Tevatron exclusion Xenon CDMS D5 LHC reach -43-44 Xenon 0 SCDMS reach Xenon 0 reach -45-46 D11 LHC reach 1 m " (GeV) 2 3

For example, 08.1783 Goodman, Ibe, Rajaraman, Shepherd, Tait, Yu, 08.1783-38 -39 CRESST monojet ) 2 (cm SI! N -40-41 -42 CoGeNT favored D1 LHC reach CoGeNT D11 Tevatron exclusion Xenon CDMS D5 LHC reach -43-44 Xenon 0 SCDMS reach Xenon 0 reach -45-46 D11 LHC reach 1 m " (GeV) 2 3 For small m X, collider rates controlled by larger mass scales, i.e., p T cut; does not depend on m X. Collider bounds flat and stronger.

More recently WIMP nucleon cross section ΣN cm 2 37 38 39 40 41 42 43 44 45 46 ATLAS 7TeV, 1fb 1 VeryHighPt Solid : Observed Dashed : Expected ΧΓ Μ Χ qγ Μ q CoGeNT Α s ΧΧ G ΜΝ G ΜΝ Spin independent DAMA q ± 33 CRESST 90 C.L. 1 0 1 2 3 WIMP mass m Χ GeV XENON CDMS XENON 0 WIMP nucleon cross section ΣN cm 2 34 35 36 37 38 39 40 41 ATLAS 7TeV, Solid : Observed Dashed : Expected 1 0 DAMA q ± 33 ΧΓ Spin depend WIMP ma Figure Fox, 5: ATLAS Harnik, limits Kopp, and on Tsai, (a) spin-independent 19.4398 and (b) spin-dependent dark compared to limits from the direct detection experiments. In particular, we independent scattering from CDMS [42], XENON- [43], XENON-0 [44], 47] and CRESST [48], and constraints on spin-dependent scattering from DA

Effective operator effective? DM SM DM Independent of the details?

Effective operator effective? DM SM DM Use colliders to constrain and probe the same operator However, E cm = 0s GeV m Φ (mediator mass), probing more structure of the s-matrix. Depending on more details of the mediator. Moreover, the mediator itself should be within reach! The dependence on the mass of the mediator has been explored in: 15.3797, 13.0240, 1111.2359

Mediator, two typical examples. x gd gsm N= Ar, Ge, Xe,... x mediator, ϕ - ϕ=higgs g SM (0 MeV)/(0 GeV) m x 0 GeV σ n -43 - -45 cm -2 - Φ=0 GeV spin-1, D=dirac fermion σ n -36 - -39 cm -2

Probe NP with direct detection -39 DAMA/Na ] -40 2 WIMP-Nucleon Cross Section [cm -41-42 -43 CoGeNT CDMS DAMA/I EDELWEISS XENON0 (20) -44 XENON0 (2011) Buchmueller et al. -45 6 7 8 9 20 30 40 50 0 200 300 400 00 2 WIMP Mass [GeV/c ] SUSY, typically Higgs mediated.

Probe NP with direct detection -39 DAMA/Na ] -40 Light DM spin-1 mediator. 2 WIMP-Nucleon Cross Section [cm -41-42 -43 CoGeNT CDMS DAMA/I EDELWEISS XENON0 (20) -44 XENON0 (2011) Buchmueller et al. -45 6 7 8 9 20 30 40 50 0 200 300 400 00 2 WIMP Mass [GeV/c ] SUSY, typically Higgs mediated.

Case study: a spin-1 Z Xiang-Dong. Ji, Haipeng An, LTW in progress Only couples to SM quarks and DM. x x gd mediator, Z gz N= Ar, Ge, Xe,...

Connection with direct detection 2.0 Tevatron rate for Monojet + (MET> 80 GeV) Σ pb 1.5 1.0 MD 50 GeV MD 150 GeV - - - - - - - - - - MD 50 GeV Contact Interaction - - - - - - - - - - MD 150 GeV Contact Interaction 0.5 0 200 400 600 800 00 1200 1400 M Z' GeV g D =g Z, fix g Z /M Z

Connection with direct detection resonance prod. Z 2.0 Tevatron rate for Monojet + (MET> 80 GeV) Σ pb 1.5 1.0 MD 50 GeV MD 150 GeV - - - - - - - - - - MD 50 GeV Contact Interaction - - - - - - - - - - MD 150 GeV Contact Interaction 0.5 0 200 400 600 800 00 1200 1400 M Z' GeV g D =g Z, fix g Z /M Z

Connection with direct detection resonance prod. Z 2.0 Tevatron rate for Monojet + (MET> 80 GeV) 1.5 MD 50 GeV MD 150 GeV contact-like Σ pb 1.0 - - - - - - - - - - MD 50 GeV Contact Interaction - - - - - - - - - - MD 150 GeV Contact Interaction 0.5 0 200 400 600 800 00 1200 1400 M Z' GeV g D =g Z, fix g Z /M Z

Connection with direct detection 2.0 Tevatron rate for Monojet + (MET> 80 GeV) Σ pb 1.5 1.0 MD 50 GeV MD 150 GeV - - - - - - - - - - MD 50 GeV Contact Interaction - - - - - - - - - - MD 150 GeV Contact Interaction 0.5 0 200 400 600 800 00 1200 1400 M Z' GeV g D =g Z, direct detection rate only depends on g Z /M Z

Connection with direct detection Tevatron rate for Monojet + (MET> 80 GeV) 2.0 Σ pb 1.5 1.0 MD 50 GeV MD 150 GeV - - - - - - - - - - MD 50 GeV Contact Interaction - - - - - - - - - - MD 150 GeV Contact Interaction A factor of 3 in σ collider a factor of 3 in (g Z ) 2 σ dir (g Z ) 4 a factor of 9 0.5 0 200 400 600 800 00 1200 1400 M Z' GeV g D =g Z, direct detection rate only depends on g Z /M Z

Operators for direct detection Operator Structure DM-nucleon Cross Section O 1 Nγ µ N χγ µ χ SI, MI O 2 Nγ µ N χγ µ γ 5 χ SI, MD p N s χ, (σ χ ) 9g 2 Z g 2 D M 2 N M 2 χ πm 4 Z (M N +M χ ) 2 g 2 Z g 2 D5 M 4 N M 2 χv 2 πm 4 Z (M N +M χ ) 4 O 3 Nγ µ γ 5 N χγ µ χ SD, MD s N p χ g 2 Z 5 g2 D M 2 N M 2 χ [(M N +M χ ) 2 +2M 2 N ]v2 2πM 4 Z (M N +M χ ) 4 O 4 Nγ µ γ 5 N χγ µ γ 5 χ SD, MI s N s χ 3g 2 Z 5 g2 D5 M 2 N M 2 χ πm 4 Z (M N +M χ ) 2

Operators for direct detection Operator Structure DM-nucleon Cross Section O 1 Nγ µ N χγ µ χ SI, MI O 2 Nγ µ N χγ µ γ 5 χ SI, MD p N s χ, (σ χ ) 9g 2 Z g 2 D M 2 N M 2 χ πm 4 Z (M N +M χ ) 2 g 2 Z g 2 D5 M 4 N M 2 χv 2 πm 4 Z (M N +M χ ) 4 O 3 Nγ µ γ 5 N χγ µ χ SD, MD s N p χ g 2 Z 5 g2 D M 2 N M 2 χ [(M N +M χ ) 2 +2M 2 N ]v2 2πM 4 Z (M N +M χ ) 4 O 4 Nγ µ γ 5 N χγ µ γ 5 χ SD, MI s N s χ 3g 2 Z 5 g2 D5 M 2 N M 2 χ πm 4 Z (M N +M χ ) 2 σ SI = 9g2 Z g 2 D M N 2 M D 2 ( πmz 4 (M N + M D ) 2 3.9 39 cm 2 g ) Z 2 ( gd ) ( ) 2 200 GeV 4 0.3 0.3 M Z Will also show results for O4

Monojet search q g q Z! Z q!! g q - Tevatron. CDF 1 fb -1, MET>80 GeV. - LHC. ATLAS 1 fb -1 LowPT Selection requires E T > 120 GeV, one jet p T (j 1 ) > 120 GeV, η(j1) < 2, events are vetoed if they contain a second jet with p T (j 2 ) > 30 GeV and η(j 2 ) < 4.5. HighPT Selection requires E T > 220 GeV, p T (j 1 ) > 250 GeV, η(j1) < 2, events are vetoed if there is a second jet with p T (j 2 ) > 60 GeV or φ(j 2, E T ) < 0.5 and η(j 2 ) < 4.5. Any further jets with η(j 3 ) < 4.5 must have p T (j 3 ) < 30 GeV. verthighpt Selection requires E T > 300 GeV, one jet with p T (j 1 ) > 350 GeV, η(j 1 ) < 2, and events are vetoed if there is a second jet with η(j 2 ) < 4.5 and with either p T (j 2 ) > 60 GeV or (j 2, E T ) < 0.5. Any further jets with η(j 3 ) < 4.5 must have p T (j 3 ) < 30 GeV.

Limits and reaches: monojet+met Dashed: Tevatron 1 fb -1, MET > 80 GeV, CDF, PRL 1, 2008 33 Atlas 1 fb 1 90 C.L. Solid: LHC, 7 TeV 1 fb -1 Very High PT Dotted: LHC 14 TeV, 0 fb -1 MET > 500 GeV ΣSI cm 2 36 39 42 CDF 1 fb 1 90 C.L. 14 TeV LHC reach 0 fb 1 XENON 0 CDMS 45 1 5 50 0 500 WIMP Mass GeV g Z =g D, g Z 5 =g D5 =0 M Z = 0 GeV, 300 GeV, 1 TeV Xiangdong Ji, Haipeng An, LTW, appearing soon.

Spin dependent Dashed: Tevatron 1 fb -1, MET > 80 GeV, CDF, PRL 1, 2008 Solid: LHC, 7 TeV 1 fb -1 Very High PT 36 XENON COUPP 20 PICASSO 2009 ΣSD cm 2 38 40 SIMPLE 2011 42 1 5 50 0 500 WIMP Mass GeV M Z = 0 GeV, 300 GeV, 500 GeV, 1 TeV, 1.5 TeV

LHC reach in monojet+met. 38 ΣSI cm 2 39 40 41 42 0 500 00 1500 2000 2500 M Z' GeV More scenarios are under study. Xiangdong Ji, Haipeng An, LTW, appearing soon.

LHC reach in monojet+met. 38 ΣSI cm 2 39 40 41 42 0 500 00 1500 2000 2500 LHC rate dominated by MET cut, insensitive to M Z. LHC bounds only on g Z Bounds on σ SI (M Z ) -4 M Z' GeV More scenarios are under study. Xiangdong Ji, Haipeng An, LTW, appearing soon.

LHC reach in monojet+met. ΣSI cm 2 38 39 40 41 LHC rate falls off rapidly with M Z, faster than (M Z ) -4 42 0 500 00 1500 2000 2500 LHC rate dominated by MET cut, insensitive to M Z. LHC bounds only on g Z Bounds on σ SI (M Z ) -4 M Z' GeV More scenarios are under study. Xiangdong Ji, Haipeng An, LTW, appearing soon.

Di-jet resonance searches. We could, and should, search for the mediator directly! - Resonance searches. ATLAS: 1 fb -1 18.6311 CMS: 1 fb -1 17.4771 CDF: Phys. Rev. D79 (2009). - Compositeness. CMS 36 pb -1 : Phys. Rev. Lett. 6 (2011) Dzero: Phys. Rev. Lett. 3 (2009)

Combining di-jet with monojet Assume gz = gd 38 Atlas LowPT CDF monojet Atlas HighPT ΣSI cm 2 40 LHC reach CDF dijet pole Atlas VeryHighPT 42 Atlas dijet pole 44 0 200 500 00 2000 5000 Z' Mass GeV

Varying y=(g D /g Z ) 38 ΣSI cm 2 40 42 44 0 200 500 00 2000 5000 M Z' GeV 1, 3, 5,, 20

Signals from new model extensions

Dark light Higgs - NMSSM near PQ limit. Very light GeV- GeV scalars. Singlino-like light dark matter. Large σ SI. (GeV) m χ 2 140 120 0 h 2 χ χ 1 h 2 χ χ 1 h 2 χ χ 2 1 2 2 dominant dominant dominant h 2 bb dominant 80 60 40 20 0 80 85 90 95 0 5 1 115 120 125 m h2 (GeV) hiding Higgs? FIG. 1: Dominant decay modes of the SM-like Higgs. A points are allowed by the current experimental bounds, with right relic density at 3σ level (for detailed discussions, see [8]

CDM embedded in a dark sector? χ DM G dark ɛ Standard Model Dark Sector - Dark force, suppressed couplings to the SM. - Force carriers part of the dark sector, expected to be light. Direct detection rate could still be significant.

Small Z mass. 29 31 ΣSI cm 2 33 35 37 CDF 1 fb 1 Atlas LowPT Atlas HighPT Atlas VeryHighPT 1 2 5 20 Z' Mass GeV

Very light Z -> Lepton Jets" - Decay of the dark photon arising from a heavier particle (Z boson, MSSM LSP) leads to a highly collimated lepton pair. Lepton jet. γ e ±,µ ± δθ < 0.1 Lepton Jet Typical E γ > GeV m γ GeV δθ m γ /E γ < 0.1 - Arkani-Hamed, Weiner 08.0714; - Baumgart, Cheung, Ruderman, LTW, Yavin 0901.0283; Cheung, Ruderman, LTW, Yavin 0909.0290

Conclusion. - One of the most exciting opportunities: Discovering the WIMP dark matter and measuring its properties. - LHC will play a crucial role in this pursuit. - Multiple aspects and approaches. Search for conventional CDM. More model independent searches. Alternative models with distinct signatures.

extra

TeV dark matter: WIMP miracle. DM SM DM - If dark matter is Rate in thermal eq. Freeze out: dropping out of thermal eq. Stronger coupling, lower abundance. Weakly interacting: g D 0.1 Weakscale: M D s GeV - TeV We get the right relic abundance of dark matter. - A major hint of TeV scale new physics. We can produce and study them at the LHC!

Spin measurements. Supersymmetry?

Spin measurements. Supersymmetry?

Spin measurements. Supersymmetry? l l q E T p q Ñ l p g q E T q

Spin measurements. Supersymmetry? l l q E T p q Ñ l p g q E T q

Spin measurements. Supersymmetry? l l q E T Side? p q Ñ l p g q E T q

Spin measurements. Supersymmetry? l l q E T Side? p q Ñ l p g q E T q - No universally applicable method. Different strategies will be used in different scenarios. A review: LTW and Yavin, arxiv:0802.2726 - More information of the signal, masses and underlying processes, is crucial.

SUSY dark force. - Dark matter self-interaction, mediated by 0 GeV MSSM superpartners λ 1 Jdark LSP 1 GeV dark sector A dark µ J µ EM e + e Arkani-Hamed, Finkbeiner, Slatyer, Weiner 08.0713 Arkani-Hamed, Weiner 08.0714 also see Pospelov, Ritz, Voloshin 0711.4866 Correct thermal relic density fixes D

Supersymmetric dark force - Most natural way of generating the GeV scale. - Spectacular signal. - Early discovery. leptons h DS leptons L Jet MET χ 0 χ DS E T E T L Jet L Jet χ DS χ 0 h DS leptons L Jet leptons