complementary paths to discovery and beyond -...

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Dark matter in the coming decade:Complementary paths to discovery and beyond

*Suggestions and corrections are most welcome and should be directed to one or more of the following contributors: Jim Buckley, Jonathan Feng, Manoj Kaplinghat,

Konstantin Matchev, Dan McKinsey, and Tim Tait

Cosmic Frontier Workshop, March 6, 2013

(CliffsNotes version)

Snowmass 2013 Cosmic Frontier Working Group 4: Dark Matter Complementarity*

https://indico.fnal.gov/getFile.py/access?contribId=17&sessionId=73&resId=0&materialId=paper&confId=6199




Intro: part I• Dark matter is six times as prevalent as normal matter in

the Universe, but its identity is unknown. Dark matter is a grand challenge for fundamental physics and astronomy. Its mere existence implies that our inventory of the basic building blocks of nature is incomplete, and uncertainty about its properties clouds all attempts to understand how the universe evolved to its present state and how it will evolve in the future. At the same time, the field of dark matter will be transformed in the coming decade. This prospect has drawn many new researchers to the field, which is now characterized by an extraordinary diversity of approaches unified by the common goal of discovering the identity of dark matter.

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Intro: part II• As we will discuss, a compelling solution to the dark

matter problem requires synergistic progress along many lines of inquiry. Our primary conclusion is that the diversity of possible dark matter candidates requires a balanced program based on four pillars: direct detection experiments that look for dark matter interacting in the lab, indirect detection experiments that connect lab signals to dark matter in the galactic halos, collider experiments that elucidate the particle properties of dark matter, and astrophysical probes that determine how dark matter has shaped the evolution of large-scale structures in the Universe.

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Intro: part III• In this Report we summarize the many dark matter

searches currently being pursued in each of these four approaches. The essential features of broad classes of experiments are described, each with their own strengths and weaknesses. The goal of this Report is not to prioritize individual experiments, but rather to highlight the complementarity of the four general approaches that are required to sustain a vital dark matter research program. Complementarity also exists on many other levels,of course; in particular, complementarity within each approach is also important, but will be addressed by the Snowmass Cosmic Frontier subgroups that focus on each approach.

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Table of Contents• Introduction• Evidence and candidates• The four pillars of dark matter detection

– Direct detection– Indirect detection– Particle colliders– Astrophysical probes

• Complementarity– Basic features– Model-independent examples– Post-discovery complementarity

• Conclusions• Appendix: Dark matter projects 5

What is dark matter?• Overwhelming observational evidence for it

– 6 times as prevalent as normal matter

• We are completely ignorant about its properties– mass, spin, lifetime, gauge quantum numbers– there could even be several DM species

• It could couple to any of the SM particles– including hidden sector particles

• There are many possibilities, including:– WIMPs (studied by CF1, CF2)– Asymmetric DM (CF1)– Axions (CF3)– Sterile neutrinos (CF3)– Hidden sector DM (CF4) 6

DM interactions vs. DM probes• For the purposes of this report, DM candidates are

categorized according to their basic interactions

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• Different experimental probes fall in different regions – detailed explanation of these

plots will follow shortly

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Appendices: lists of experiments

9

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PRELIMINARY DRAFT VERSION 13 11

TABLE II: Current and planned indirect detection experiments.Status Experiment Target Location Major Support CommentsCurrent AMS e+/e−,

anti-nucleiISS NASA Magnet Spectrome-

ter, RunningFermi Photons,

e+/e−Satellite NASA, DOE Pair Telescope and

Calorimeter, Run-ning

HESS Photons,e−

Namibia German BMBF, Max Planck Society,French Ministry for Research, CNRS-IN2P3, UK PPARC, South Africa

AtmosphericCherenkov Tele-scope (ACT),Running

IceCube/DeepCore

Neutrinos Antarctica NSF, DOE, International *Belgium,Germany, Japan, Sweden)

Ice Cherenkov,Running

MAGIC Photons,e+/e−

La Palma German BMBF and MPG, INFN,WSwiss SNF, Spanish MICINN, CPAN,Bulgarian NSF, Academy of Finland,DFG, Polish MNiSzW

ACT, Running

PAMELA e+/e− SatelliteVERITAS Photons,

e+/e−Arizona,USA

DOE, NSF, SAO ACT, Running

ANTARES Neutrinos Mediter-ranean

France, Italy, Germany, Netherlands,Spain, Russia, and Morocco

Running

Planned CALET e+/e− ISS Japan JAXA, Italy ASI, NASA CalorimeterCTA Photons ground-

based(TBD)

International (MinCyT, CNEA, CON-

ICET, CNRS-INSU, CNRS-IN2P3,

Irfu-CEA, ANR, MPI, BMBF, DESY,

Helmholtz Association, MIUR, NOVA,

NWO, Poland, MICINN, CDTI, CPAN,

Swedish Research Council, Royal Swedish

Academy of Sciences, SNSF, Durham UK,

NSF, DOE

ACT

GAMMA-400

Photons Satellite Russian Space Agency, RussianAcademy of Sciences, INFN

Pair Telescope

GAPS Anti-deuterons

Balloon(LDB)

NASA, JAXA TOF, X-ray andPion detection

HAWC Photons,e+/e−

Sierra Ne-gra

NSF/DOE Water Cherenkov,Air Shower SurfaceArray

IceCube/PINGU

Neutrinos Antarctica NSF, Germany, Sweden, Belgium Ice Cherenkov

KM3NeT Neutrinos Mediter-ranean

ESFRI, including France, Italy, Greece,Netherlands, Germany, Ireland, Roma-nia, Spain, UK, Cyprus

Water Cherenkov

ORCA Neutrinos Mediter-ranean

ESFRI, including France, Italy, Greece,Netherlands, Germany, Ireland, Roma-nia, Spain, UK, Cyprus

Water Cherenkov

TO BE CONTINUED DRAFT


TABLE III: Current and proposed particle colliders.Status Collider Type ECOM, Luminosity Major Support CommentsCurrent LHC pp 8 TeV, 20 fb−1 DOE, NSF

Upcoming LHC pp 14 TeV, 300 fb−1 DOE, NSFProposed HL LHC pp 14 TeV, 3000 fb−1

Proposed VLHC pp 33-100 TeVProposed Higgs Factory e+e− 250 GeVProposed ILC, CLIC e+e− 0.5-3 TeVProposed Muon Collider µ+µ− 6 TeV

TO BE CONTINUED

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DRAFT


APPENDIX: DARK MATTER PROJECTS

TABLE I: Current and planned direct detection experiments.Status Experiment Target Technique Location Major Support CommentsCurrent LUX 350 kg liquid Xe Ion., Scint. SURF DOE, NSF, EuropeanPlanned LZ 7 ton liquid Xe Ion., Scint. SURF DOE, NSF, EuropeanCurrent Xenon100 62 kg liquid Xe Ion., Scint. LNGS DOE, NSF, EuropeanPlanned Xenon1T 3 ton liquid Xe Ion., Scint. LNGS DOE, NSF, EuropeanPlanned PandaX-1 1.2 ton liquid Xe Ion., Scint. Jinping ChinesePlanned PandaX-2 3 ton liquid Xe Ion., Scint. Jinping ChineseCurrent XMASS-I 800 kg liquid Xe Scint. Kamioka JapanesePlanned XMASS-1.5 5 ton liquid Xe Scint. Kamioka JapaneseCurrent DarkSide-50 50 kg liquid Ar Ion., Scint. LNGS DOE, NSF, EuropeanPlanned DarkSide-G2 5 ton liquid Ar Ion., Scint. LNGS DOE, NSF, EuropeanCurrent ArDM 1 ton liquid Ar Ion., Scint. Canfranc EuropeanCurrent MiniCLEAN 500 kg liquid Ar/Ne Scint. SNOLab DOECurrent DEAP-3600 3.6 ton liquid Ar Scint. SNOLab CanadianPlanned CLEAN 40 ton liquid Ar/Ne Scint. SNOLab DOECurrent COUPP-60 CF3I Bubbles SNOLab DOE, NSFPlanned COUPP-1T CF3I Bubbles SNOLab DOE, NSFCurrent PICASSO Bubbles SNOLab CanadianCurrent SIMPLE Bubbles Canfranc EuropeanCurrent SuperCDMS 10 kg Ge Ion., Phonons Soudan DOE, NSFPlanned SuperCDMS 100 kg Ge Ion., Phonons Soudan DOE, NSFCurrent Edelweiss 4 kg Ge Ion., Phonons Modane EuropeanCurrent CRESST 10 kg CaWO4 Scint., Phonons LNGS EuropeanPlanned EURECA Ge, CaWO4

Current CoGeNT Ge Ion. Soudan DOECurrent TEXONO Ge Ion. ChineseCurrent DAMA/LIBRA NaI EuropeanCurrent ELEGANT NaI JapanesePlanned DM-Ice NaIPlanned CINDMS NaI ChineseCurrent KIMS CsICurrent DRIFT Ion.Current DMTPC CF4 gas Ion. WIPPPlanned NEXT Xe gas Ion., Scint. CanfrancPlanned MIMAC Ion. ModanePlanned Superfluid He-4Planned DNA DNA

TO BE CONTINUED

DIRECT DETECTION INDIRECT DETECTION COLLIDERS

How to illustrate complementarity?

• Qualitatively: the presence of a signal in:

10

Colliders Directdetection

Indirectdetection

The point being this:

CPM Meeting, Fermilab 2012

How to illustrate complementarity?• Quantitatively: compare rates for the three probes

– Problem: different quantities are being reported

11

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CoGeNT

CDMS (2010/11)EDELWEISS (2011/12)

XENON10 (2011)

XENON100 (2011)

COUPP (2012)SIMPLE (2012)

ZEPLIN-III (2012)CRESST-II (2012)

XENON100 (2012)observed limit (90% CL)

Expected limit of this run:

expected! 2 ± expected! 1 ±

FIG. 3: New result on spin-independent WIMP-nucleon scat-tering from XENON100: The expected sensitivity of this runis shown by the green/yellow band (1σ/2σ) and the result-ing exclusion limit (90% CL) in blue. For comparison, otherexperimental results are also shown [19–22], together withthe regions (1σ/2σ) preferred by supersymmetric (CMSSM)models [18].

the benchmark region fluctuates to 2 events is 26.4% andconfirms this conclusion.

A 90% confidence level exclusion limit for spin-independent WIMP-nucleon cross sections σχ is calcu-lated, assuming an isothermal WIMP halo with a lo-cal density of ρχ = 0.3GeV/c3, a local circular veloc-ity of v0 = 220 km/s, and a Galactic escape velocity ofvesc = 544 km/s [17]. Systematic uncertainties in the en-ergy scale as described by the Leff parametrization of [6]and in the background expectation are profiled out andrepresented in the limit. Poisson fluctuations in the num-ber of PEs dominate the S1 energy resolution and arealso taken into account along with the single PE resolu-tion. The expected sensitivity of this dataset in absenceof any signal is shown by the green/yellow (1σ/2σ) bandin Fig. 3. The new limit is represented by the thick blueline. It excludes a large fraction of previously unexploredparameter space, including regions preferred by scans ofthe constrained supersymmetric parameter space [18].

The new XENON100 data provide the most strin-gent limit for mχ > 8GeV/c2 with a minimum ofσ = 2.0 × 10−45 cm2 at mχ = 55GeV/c2. The max-imum gap analysis uses an acceptance-corrected expo-sure of 2323.7 kg×days (weighted with the spectrum of a100GeV/c2 WIMP) and yields a result which agrees withthe result of Fig. 3 within the known systematic differ-ences. The new XENON100 result continues to challengethe interpretation of the DAMA [19], CoGeNT [20], andCRESST-II [21] results as being due to scalar WIMP-nucleon interactions.

We acknowledge support from NSF, DOE, SNF, UZH,Volkswagen Foundation, FCT, Region des Pays de laLoire, STCSM, NSFC, DFG, Stichting FOM, WeizmannInstitute of Science, and the friends of Weizmann Insti-tute in memory of Richard Kronstein. We are grateful toLNGS for hosting and supporting XENON.

∗ Electronic address: [email protected]† Electronic address: [email protected]

[1] N. Jarosik et al., Astrophys. J. Suppl. 192, 14 (2011);K. Nakamura et al. (PDG), J. Phys. G37, 075021 (2010).

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[3] G. Bertone, D. Hooper, and J. Silk, Phys. Rept. 405, 279(2005).

[4] M. W. Goodman and E. Witten, Phys. Rev. D31, 3059(1985).

[5] E. Aprile et al. (XENON100), Astropart. Phys. 35, 573(2012).

[6] E. Aprile et al. (XENON100), Phys. Rev. Lett. 107,131302 (2011).

[7] M. Aglietta et al. (LVD), Phys. Rev.D58, 092005 (1998).[8] E. Aprile et al. (XENON100) Astropart. Phys. 35, 43

(2011).[9] E. Aprile et al., Phys. Rev. C79, 045807 (2009).

[10] X. Du et al., Rev. Sci. Instr. 75, 3224 (2004).[11] E. Aprile et al. (XENON100), (2012), arXiv:1207.3458.[12] E. Aprile et al. (XENON100), Phys. Rev. D84, 052003

(2011).[13] S. Yellin, Phys. Rev. D66, 032005 (2002).[14] G. Plante et al., Phys. Rev. C84, 045805 (2011).[15] E. Aprile et al., Phys. Rev. Lett. 97, 081302 (2006).[16] M. M. Szydagis et al., JINST 6, P10002 (2011).[17] M. C. Smith et al., Mon. Not. R. Astron. Soc. 379, 755

(2007).[18] Combined region using C. Strege et al., JCAP 1203,

030 (2012); A. Fowlie et al. (2012), arXiv:1206.0264;O. Buchmueller et al. (2011), arXiv:1112.3564.

[19] C. Savage et al., JCAP 0904, 010 (2009).[20] C. E. Aalseth et al. (CoGeNT), Phys. Rev. Lett. 106,

131301 (2011).[21] G. Angloher et al. (CRESST-II), Eur. Phys. J. C72, 1971

(2012).[22] Z. Ahmed et al. (CDMS), Science 327, 1619 (2010);

Z. Ahmed et al. (CDMS), Phys. Rev. Lett. 106,131302 (2011); E. Armengaud et al. (EDEL-WEISS), Phys. Lett. B 702, 329 (2011); J. Angleet al. (XENON10), Phys. Rev. Lett. 107, 051301 (2011);M. Felizardo et al. (SIMPLE), Phys. Rev. Lett. 108,201302 (2012); E. Behnke et al. (COUPP) (2012),arXiv:1204.3094; D. Y. Akimov et al. (ZEPLIN-III), Phys. Lett. B 709, 14 (2012); E. Armengaudet al. (EDELWEISS) (2012), arXiv:1207.1815.

Figure 1: Comparison of current (solid lines) and projected (dashed lines) limits on the DM annihila-tion cross section from different gamma-ray searches as a function of WIMP mass. Limits for Fermi(magenta lines) and H.E.S.S. (solid black line) are calculated for a 100% branching ratio to bb. Pro-jected limits for CTA are shown for WIMP annihilation to bb and a 500 hour observation of Sculptor(red dashed line) and for WIMP annihilation to bb (black dashed line), WW (green dashed line),and ττ (cyan dashed line) and a 500 hour observation of the GC. Filled circles represent pMSSMmodels satisfying WMAP7 constraints on the relic DM density and experimental constraints fromATLAS and CMS SUSY searches and XENON100 limits on the spin-independent WIMP-nucleoncross section (Cahill-Rowley et al., 2012; Conley et al., 2011). Models indicated in red would beexcluded by the CTA 95% C.L. upper limit from a 500 hour observation of the Galactic Center.

ration with 61 MSTs corresponding to the baseline MST array with an additional US contribution of36 MSTs. This configuration has comparable point-source sensitivity to previously studied CTA con-figurations below 100 GeV but 2–3 times better point-source sensitivity between 100 GeVand 1 TeV.

Figure 1 shows the projected sensitivity of our candidate CTA configuration to a WIMP particleannihilating through the bb channel. For the Sculptor dSph, one of the best dSph candidates in thesouth, CTA could reach∼ 10−24 cm2 s−1 at 1 TeV which is comparable to current limits from H.E.S.S.observations of the GC halo. For an observation of the GC utilizing the same 0.3–1.0 annular searchregion as the H.E.S.S. analysis CTA could rule out models with cross sections significantly below thethermal relic cross section down to ∼ 3 × 10−27 cm2 s−1. Overlaid in the figure are WIMP modelsgenerated in the pMSSM framework that satisfy all current experimental constraints from colliderand direct detection searches (Cahill-Rowley et al., 2012; Conley et al., 2011). Approximately halfof the models in this set could be excluded at the 95% C.L. in a 500 hour observation

3

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I. Specific theory models• Choose a complete new physics model with a

dark matter candidate– See tomorrow afternoon’s CF4 sessions for talks on

• MSSM (Baer)• MSUGRA (Sanford)• NMSSM (McCaskey)• UED (Kong)• Hidden charged DM (Yu)

• Compute the three types of signals as a function of the model parameters. Impose constraints.

• Problem: too many free input parameters– fewer parameters come at the cost of introducing

model dependent assumptions 12

II. Model-independent approaches • Alternatively, be agnostic about the underlying

theory model• Parameterize our ignorance about

– the origin of SUSY breaking• pMSSM talks (Ismail, Cotta, Cahill-Rowley, Drlica-Wagner)

– the type of DM-SM interactions and their mediators• effective operators (Shepherd)

• Effective Lagrangian considered in the complementarity document:

13

DRAFT


if dark matter annihilation is insignificant now, for example, as in the case of asymmetricdark matter.

• Particle Colliders provide the opportunity to study dark matter in a highly-controlled labo-ratory environment, may be used to precisely constrain many dark matter particle properties,and are sensitive to the broad range of masses favored for WIMPs. Hadron colliders are rel-atively insensitive to dark matter that interacts only with leptons, and colliders are unableto distinguish missing momentum signals produced by a particle with lifetime ∼ 10−7 s fromone with lifetime >∼ 1017 s, as required for dark matter.

• Astrophysical Probes are unique probes of the “warmth” of dark matter and hidden darkmatter properties, such as its self-interaction strength, and they directly measure the effectsof dark matter properties on large-scale structure in the Universe. Astrophysical probes aretypically unable to distinguish various forms of CDM from each other or make other precisionmeasurements of the particle properties of dark matter.

B. Model-Independent Examples

The qualitative features outlined above may be illustrated in a simple and fairly model-independent setting by considering dark matter that interacts with standard model particlesthrough four-particle contact interactions, which represent the exchange of very heavy particles.

To do this, we may choose representative couplings of a spin-1/2 dark matter particle χ withquarks q, gluons g, and leptons given by

1M2

qχγµγ5χ

q

qγµγ5q +αS

M3g

χχGaµνGaµν +

1M2

χγµχ

γµ . (1)

The interactions with quarks mediate spin-dependent direct signals, whereas those with gluonsmediate spin-independent direct signals. The coefficients Mq, Mg, and M characterize the strengthof the interaction with the respective SM particle, and in this representative example should bechosen such that the annihilation cross section into all three channels provides the correct relicdensity of dark matter. The values of the three interaction strengths together with the mass of thedark matter particle mχ completely defines this theory and allows one to predict the rate of bothspin-dependent and spin-independent direct scattering, the annihilation cross section into quarks,gluons, and leptons, and the production rate of dark matter at colliders.

Each class of dark matter search outlined in Sec. III is sensitive to some range of the interactionstrengths for a given dark matter mass. Therefore, they are all implicitly putting a bound on theannihilation cross section into a particular channel. Since the annihilation cross section predictsthe dark matter relic density, the reach of any experiment is thus equivalent to a fraction of theobserved dark matter density. This connection can be seen in the plots in Fig. 2, where the left(right) vertical axis shows the annihilation cross-section normalized to σth (the relic density Ωχ

normalized to ΩDM ). If the discovery potential for an experiment with respect to one of theinteraction types maps on to one times the observed dark matter density (the horizontal dashedlines in Fig. 2), that experiment will be able to discover dark matter which interacts only with thatSM particle. If an experiment were to observe an interaction consistent with a DM fraction largerthan one (yellow-shaded regions in Fig. 2), it would have discovered dark matter but we wouldinfer that there were still important annihilation channels still waiting to be observed. Finally, ifan experiment were to observe an interaction consistent with a fraction less than one (green-shadedregions in Fig. 2), it would have discovered one species of dark matter, which, however, could notaccount for all of the dark matter, and there are still important other DM species still waiting tobe discovered.

D11D8 D5

14DRAFT








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q

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Colliders Direct detection

Indirect detection

σ(qq → χχ+X)

σ(χχ → qq).v

σp(Mq) (Mq)

(Mq)

Complementarity parameter space

15

Ωχ

ΩDM∼ σthermal

σ(χχ → qq) + σ(χχ → other)

DM coupling exclusively to quarks

• Flavor universal axial vector coupling (D8 operator)

16DRAFT








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qχγµγ5χ

q

qγµγ5q +αS

M3g

χχGaµνGaµν +

1M2

χγµχ

γµ . (1)




1

M2

χγµχ

γµ

DM coupling exclusively to leptons

• Flavor universal vector coupling (D5 operator)

17

DM coupling exclusively to gluons

• 4-point interaction (D11 operator)

18

αS

M3g

χχ GaµνGaµν

Action items

• Collect feedback at the CF workshop– suggestions are already coming in– are there any major points missing?

• Finish writing– Write conclusions section

• Venn diagram?

– References: more or fewer?– Complete the tables with DM experiments– Authorship?

• Draft an executive summary document• Anything else?

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complementary paths to discovery and beyond -...

Documents