The Search for! sub-gev Dark Matter

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1 The Search for! sub-gev Dark Matter Rouven Essig C.N. Yang Institute for Theoretical Physics, Stony Brook IPMU Seminar, Nov 15, 2013

2 Lots of evidence for dark matter X-ray: NASA/CXC/CfA/M.Markevitch et al. Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al. Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al.

3 The Search for Dark Matter What is dark matter? =) clearly, an important question Major experimental efforts are underway! =) real chance of success in coming years But are we looking everywhere we can and should?

4 The Dark Matter Paradigm The search for DM is dominated by the search for! Weakly Interacting Massive Particles (WIMPs) (1) ~ GeV (1) axions and other DM candidates often only get mentioned as a footnote

5 Beyond The Paradigm The intensive search for WIMPs is a no-brainer (2) but let s make sure they don t get all the attention many new physics models have non-wimp DM! many other ways to get correct DM abundance! no new physics at the LHC yet Many other well-motivated candidates exist that we can and should look for! (2) ditto for axions, which should really get much more attention

6 sub-gev Dark Matter simple, well-motivated, viable candidates exist very rich phenomenology,! plenty of room for new experimental investigation opportunities are still being actively explored This talk: broad, but biased, overview of: some constraints & models! experimental opportunities

7 Outline some constraints & models! experimental opportunities! direct detection! colliders (e + e - )! fixed-target (p & e - )! indirect detection

8 Is sub-gev DM allowed? Yes, must avoid a few! (model-dependent)! constraints

9 Constraints from relic abundance Lee-Weinberg bound: dark matter = heavy neutrino, interacting with weak-scale mediators (1977) m2 M GeV m 2 too much DM for low masses Easy to avoid w/ e.g. (new) light mediators: m2 M 4 small or 1 m 2 e.g. Boehm, Fayet;

10 Constraints on DM annihilation from Cosmic Microwave Background feffhsvi[cm 3 s 1 ] WMAP9 Current (WMAP9+Planck+ACT+SPT+BAO+HST+SN) Full Planck temp. and pol. forecast CMB Stage 4 forecast Cosmic Variance Limit w/ typical feff for a WIMP M c [GeV] e.g. Galli et.al.; Slatyer, Padmanabhan, Finkbeiner; Mathew Madhavacheril, Neelima Sehgal, Tracy Slatyer ( )

11 Constraints on DM annihilation from Cosmic Microwave Background e.g. Galli et.al.; Slatyer, Padmanabhan, Finkbeiner; Mathew Madhavacheril, Neelima Sehgal, Tracy Slatyer ( )

12 sub-gev Dark Matter s-wave standard freeze out is disfavored below ~10 GeV But constraints are model dependent & easy to avoid, e.g. p-wave suppressed non-thermal production asymmetric freeze-out with hidden-sector particles (WIMPless DM) freeze-in sub-dominant e.g. Kaplan, Luty, Zurek (2009),! Falkowski et.al. (2011) e.g. Feng & Kumar (2008) e.g. Hall et.al. (2009)

13 A simplified model Consider DM, χ, in a hidden sector SM? Dark Sector many possible mediators:! (pseudo-)scalar, (pseudo-)vector,

14 A simplified model Consider DM, χ, in a hidden sector SM X A0 Dark Sector A 0 + +? for concreteness, assume χ couples to dark photon A that mixes with photon via kinetic mixing L = 2 F Y,µ F 0 µ Holdom;! Galison, Manohar dark sector could be arbitrarily rich, but this is well-motivated and acts as a simplified model sub-gev scale can be generated naturally

15 A simplified model 4 parameters: m,m A 0,,g m m A 0 MeV 5 GeV A mediates DM-SM interactions (also DM-DM self-interactions) Aʹ g Aʹ e q, ` q, `+ (we re agnostic about how DM abundance is generated)

16 Constraints + prospects on visible A decays If m A 0 < 2 m then A decays visibly, e.g E774 A' Æ Standard Model a m, 5 s a m,±2 s favored a e KLOE MAMI APEXêMAMI Test Runs BaBar Aʹ e - e + What if A decays e DarkLight MESA APEX invisibly, to DM? 10-4 VEPP-3 E141 Orsay HPS Aʹ 10-5 U m A' HGeVL will come back! to this later

17 Outline some constraints & models! experimental opportunities! direct detection! colliders (e + e - )! fixed-target (p & e - )! indirect detection

18 The Future of Direct Detection push lower in cross-section w/ bigger detectors around 2020, this important program will have reached it s full potential Cross section [cm 2 ] (normalised to nucleon) dmtools.brown.edu WIMP Mass [GeV/c 2 ]

19 The Future of Direct Detection RE, Mardon, Volansky push much lower in mass by considering DM scattering off electrons or molecules Cross section [cm 2 ] (normalised to nucleon) Cross section [cm 2 ] (normalised to nucleon) dmtools.brown.edu WIMP Mass [GeV/c 2 ]

20 Cannot use elastic nuclear recoils for detection Recall: Heavy DM Atom

21 Cannot use elastic nuclear recoils for detection Recall: Heavy DM DM large recoil! no problem

22 Cannot use elastic nuclear recoils for detection nuclear recoil energy dmtools.brown.edu E NR kev ev MeV GeV TeV DM mass Cross section [cm 2 ] (normalised to nucleon) WIMP Mass [GeV/c 2 ] for sub-gev DM, nuclear recoil energy is too small to produce visible scintillation, ionization, or phonon signal limits absent! below ~few GeV

23 But, total energy available is much larger: kev Etot ev MeV GeV TeV DM mass enough energy to excite or ionize an atom, or dissociate molecules! (just not from nuclear recoils!)

24 How to detect sub-gev DM ionization! (DM-electron scattering)! excitation! (DM-electron scattering)! molecular dissociation (DM- or ν-nucleon scattering)

25 Ionization: DM scattering off electron DM Atom

26 Ionization: DM scattering off electron DM Atom threshold ~ 10 ev Signal: single (or few) electron events XENON10/100, LUX, DarkSide, could detect this!

27 A Proof of Principle (for ionization signal) First direct detection limits on! sub-gev Dark Matter from XENON10 RE, A. Manalaysay, J. Mardon, P. Sorensen, T. Volansky! ( , PRL)

28 The XENON10 experiment PMT s Xe Gas detector! schematic ~E Xe liquid (~14 kg) PMT s two-phase xenon time projection chamber operated for ~1 year in 2006/2007

29 How to detect usual WIMPs Xe! Xe, Xe + produces photons and electrons heavy! Two types of signal: DM e e e e Signal t

30 How to detect usual WIMPs Xe! Xe, Xe + produces photons and electrons Two types of signal: S1: prompt scintillation S2: proportional scintillation! (from ionization) Signal S1 S2 t

31 Background events e, e e e e Signal (small) S1 S2 t

32 Usual WIMP searches Signal Signal S1 S2 t S1 S2 t WIMP background S2 S2 S 1 WIMP S 1 What about light DM?

33 Light Dark Matter hitting an electron on average, a single electron produces about 27 detected photo-electrons DM S1: not measurable e S2: small signal Signal (nothing) S1 S2 t

34 The XENON10 data XENON10 was set-up to trigger on single e - events (with S1 = 0) for only 12.5 days in 2006 Can use this data to set the first! direct detection limits on sub-gev DM

35 The XENON10 data XENON10 used this data to set limits on ~10 GeV DM from nuclear recoils, constraining DAMA/CoGeNT region (2011)

36 The XENON10 data? XENON10 used this data to set limits on ~10 GeV DM from nuclear recoils, constraining DAMA/CoGeNT region (2011)

37 The XENON10 data ~500 events w/ 1-, 2-, or 3-electrons are observed Counts / 0.1 electrons single electron double electron Best fit Allowed at 90% upper limit triple electron Ionization Signal [electrons] 1-electron events 2-electron events 3-electron events

38 The XENON10 data ~500 events w/ 1-, 2-, or 3-electrons are observed Counts / 0.1 electrons single electron double electron Best fit Allowed at 90% upper limit triple electron Ionization Signal [electrons] What are these events? several possibilities exist, but virtually no attempt was made to understand their origin

39 The XENON10 data ~500 events w/ 1-, 2-, or 3-electrons are observed Counts / 0.1 electrons single electron double electron Best fit Allowed at 90% upper limit triple electron Ionization Signal [electrons] 90% c.l. upper bounds! on rates: 1 e - : 34.5 counts/kg/day 2 e - : 4.5 counts/kg/day 3 e - : 0.83 counts/kg/day Note: DM can give rise to 2- and 3-electron events: outgoing e - can ionize further e - s! ionizing an inner-shell e - gives a de-excitation photon that can ionize other e - s

40 The XENON10 data ~500 events w/ 1-, 2-, or 3-electrons are observed Counts / 0.1 electrons single electron double electron Best fit Allowed at 90% upper limit triple electron Ionization Signal [electrons] 90% c.l. upper bounds! on rates: 1 e - : 34.5 counts/kg/day 2 e - : 4.5 counts/kg/day 3 e - : 0.83 counts/kg/day since number of 3-electron events is so small, this sets the best limit for somewhat heavier DM

41 First direct detection limits on sub-gev DM 2 D Hidden- Photon models Excluded by XENON10 data 1 electron 2 electrons 3 electrons Dark Matter

42 Future? Cross section Sensitivity and Event Rate Hper kg yearl 2 D g D =0.1 g D =10-2 g D =10-3 MeV DM g D =10-4 Excluded by XENON10 Hidden photon F DM HqL = He Ar Xe Ge Event Rate Hse=10-37 cm 2 L XENON10! limit Helium Xenon Argon Germanium Dark Matter 1 kg-year XENON100 & LUX can do this analysis!

43 A proposal was submitted to XENON100 XENON100 (Budnik) w/ RE, Mardon, Volansky Possible sensitivity, assuming 0.02 events kg -1 day D Hidden- Photon models XENON10 limit Dark Matter XENON100 HestimatedL dashed: annual modulation realistic??? need to do analysis to know!

44 Future? Cross section Sensitivity and Event Rate Hper kg yearl 2 D g D =0.1 g D =10-2 g D =10-3 MeV DM g D =10-4 Excluded by XENON10 Hidden photon F DM HqL = He Ar Xe Ge Event Rate Hse=10-37 cm 2 L Dark Matter 1 kg-year NB: semi-conductors (e.g. Ge) =) reach to very low masses!

45 2 D Cross section Sensitivity and Event Rate Hper kg yearl g D =0.1 g D =10-2 g D =10-3 MeV DM g D =10-4 Excluded by XENON10 Hidden photon F DM HqL = He Ar Xe Ge Event Rate Hse=10-37 cm 2 L RE, Mardon, Volansky see also Graham, Kaplan, Rajendran, Walters NB: semi-conductors (e.g. Ge) =) reach to very low masses! Dark Matter band-gap only ~ 1 ev (much lower than Xe!) current thresholds: CDMS: ~300 e - CDMSlite (increase voltage)

se @cm 2 D 10-33 10-34 10-35 10-36 10-37 10-38 10-39 10-40 10-41 10-42 10-43 Cross section Sensitivity and Event Rate Hper kg yearl g D =0.

46 2 D Cross section Sensitivity and Event Rate Hper kg yearl g D =0.1 g D =10-2 g D =10-3 MeV DM g D =10-4 Excluded by XENON10 Hidden photon F DM HqL = He Ar Xe Ge Event Rate Hse=10-37 cm 2 L RE, Mardon, Volansky see also Graham, Kaplan, Rajendran, Walters NB: semi-conductors (e.g. Ge) =) reach to very low masses! Dark Matter band-gap only ~ 1 ev (much lower than Xe!) current thresholds: CDMS: ~300 e - CDMSlite (increase voltage) CDMSlite result, 170 evee

47 2 D Cross section Sensitivity and Event Rate Hper kg yearl g D =0.1 g D =10-2 g D =10-3 MeV DM g D =10-4 Excluded by XENON10 Hidden photon F DM HqL = He Ar Xe Ge Event Rate Hse=10-37 cm 2 L RE, Mardon, Volansky see also Graham, Kaplan, Rajendran, Walters NB: semi-conductors (e.g. Ge) =) reach to very low masses! Dark Matter band-gap only ~ 1 ev (much lower than Xe!) current thresholds: CDMS: ~300 e - CDMSlite (increase voltage) DAMIC (Si, CCD s): current threshold ~40 ev ( ) future: ~4 ev? Field developing fast!! exciting potential

48 How to detect sub-gev DM ionization! (DM-electron scattering)! excitation! (DM-electron scattering)! molecular dissociation (DM-nucleon or scattering) { Danger:! work in! progress!

49 Excitation: DM scattering off electron DM Atom

50 Excitation: DM scattering off electron DM Atom Excite atom

51 Excitation: DM scattering off electron DM threshold <O(10 ev) Atom Excite atom & look for! de-excitation photon Signal: photons Use Microwave Kinetic Inductance Detectors (MKIDs) to detect these photons?

52 How to detect sub-gev DM ionization! (DM-electron scattering)! excitation! (DM-electron scattering)! molecular dissociation (DM-nucleon scattering)

53 Molecular Dissociation: DM or ν scattering off nuclei RE, Mardon, Oren Slone, Volansky etc.! work in progress threshold ~ few ev Signal: various possibilities under investigation We are calculating rates & talking w/ several experimentalists/chemists to investigate feasibility

54 Outline some constraints & models! experimental opportunities! direct detection! colliders (e + e - )! fixed-target (p & e - )! indirect detection

55 O(GeV) DM & mediators best probed at low-energy e + e - coliders huge luminosity at e.g. B-factories large cross sections / 1 E 2 cm signal: mono-photon events

56 Existing BaBar analysis BaBar searched for: (3S)! + A 0! +invisible e b e + (3S) b A 0 A 0( ) Analysis appeared in a conference proceeding ( ), improvements + paper expected soon mono-photon trigger for only 30/fb on Υ(3S)

57 { Sensitive to DM production in e + e - collisions RE, Mardon, Papucci, Volansky, Zhong! (see also Izaguirre, Krnjaic, Schuster, Toro; Fayet; Borodatchenkova et.al., ) e e + A 0( ) invisible A can be on- or off-shell if A on-shell, get a bump!

58 The BaBar Data 3.2 GeV <E < 5.5 GeV

59 On-shell A w/ decays to any invisible state(s) Hidden Photon Æ invisible Hm A' > 2 m c L a m, 5 s a m,±2 s favored ô DarkLight ô KÆpA' E787, E949 BaBar Improved BaBar RE, Mardon, Papucci, Volansky, Zhong g-2 regions Pospelov VEPP-3 & DarkLight Wojtsekhowski, Nikolenko, Rachek Kahn, Thaler a e ô ô e 10-4 VEPP-3 KÆpA' ORKA Belle II rare Kaon decays see also deniverville, Pospelov, Ritz m BaBar and Belle II best at higher masses

60 On-shell A w/ decays to any invisible state(s) 10-2 Hidden Photon Æ invisible Hm A' > 2 m c L BaBar RE, Mardon, Papucci, Volansky, Zhong existing data 10-3 a m, 5 s a e a m,±2 s favored ô DarkLight ô ô ô KÆpA' E787, E949 BaBar Improved Converted Mono-photon potential improvement from reducing / background (private communication) e 10-4 VEPP-3 KÆpA' ORKA Belle II projected Belle II! 50/ab, better resolution potential improvement using converted photons m Belle II working on implementing monophoton trigger

61 Outline some constraints & models! experimental opportunities! direct detection! colliders (e + e - )! fixed-target (p & e - )! indirect detection

62 Proton-beam fixed target experiments Batell, Pospelov, Ritz! Deniverville, Pospelov, Ritz! Deniverville, McKeen, Ritz! Aguilar-Arevalo et.al. Produce DM in a proton dump via A! χ recoils of e - /nucleon in detector p A 0 0! A 0 χχ χ e - /N χ Target Decay pipe Shield Detector plenty of room for future exploration at neutrino facilities, e.g.! LSND, OscSNS, MiniBooNE, MicroBooNE, MINOS, NOvA, LBNE, Project X,

63 LSND sets powerful limits for ma > 2 m Χ 10-2 Hidden Photon Æ invisible Hm A' > 2 m c L BaBar deniverville, Pospelov, Ritz plot from RE, Mardon, Papucci, Volansky, Zhong e 10-3 a m, 5 s a e a m,±2 s favored ô DarkLight ô ô ô KÆpA' E787, E949 BaBar Improved Converted Mono-photon limit depends on D = g2 D VEPP-3 KÆpA' ORKA Belle II a proposal has also been submitted to MiniBoONE Aguilar-Arevalo et.al. LSND a D = m

64 10-2 a D =0.1 Limits depend on m Χ Hidden Photon HinvisibleL m c = 10 MeV BaBar 10-2 Batell, Pospelov, Ritz Hidden Photon HinvisibleL m c = 100 MeV plot from RE, Mardon, Papucci, Volansky, Zhong BaBar 10-3 a m, 5 s a m,±2 s favored ô DarkLight ô KÆpA' E787, E a m, 5 s a m,±2 s favored ô KÆpA' E787, E a e LSND a D =0.1 Belle II Standard m ô ô KÆpA' ORKA 10-4 a e KÆpA' ORKA no more! LSND limit! Belle II Standard m

Electron-beam fixed target experiments Gordan Krnjaic, Eder Izaguirre, Schuster, Toro Gordan & Eder are at workshop Example: produce χ directly from on/off-shell

65 Electron-beam fixed target experiments Gordan Krnjaic, Eder Izaguirre, Schuster, Toro Gordan & Eder are at workshop Example: produce χ directly from on/off-shell Aʹ χ recoils of e - /nucleon in detector e - A (*) χ χ χ e - /N χ Target Shield Detector new parasitic experiments possible at! e.g. JLab, Mainz, SLAC, SuperKEK, ILC,

66 Constraint from past SLAC beam dump E Hidden Photon Æ invisible Hm A' > 2 m c L Brian Batell, RE, Ze ev Surujon! (work in progress) a m, 5 s a e a m,±2 s favored E137 a D =0.1 VEPP-3 DarkLight LSND a D =0.1 ô BaBar Improved BaBar Belle II Converted Mono-photon Belle II Standard m ô ô ô KÆpA' ORKA KÆpA' E787, E949 preliminary! E137 Bjorken et.al. Constraint (not shown) also exists from SLAC milli-charge experiment Diamond, Schuster!

67 Examples of all constraints/prospects see e.g. NLWCP Snowmass report 10-2 a m, 5 s A' Æ invisible Hm c = 1 MeVL BaBar collection of work by B. Batell,! P. deniverville, E. Izaguirre, G. Krnjaic,! J. Mardon, M. Papucci, M. Pospelov, A. Ritz,! T. Volansky, Y. Zhong, Philip, Natalia, RE! (probably forgot someone!) 10-3 a m,±2 s favored ô DarkLight E787, E949 not shown:! e 10-4 a e MiniBooNE VEPP-3 KÆpA' ORKA ô ILC JLab Belle II SLAC mq! E137 Diamond, Schuster Batell, RE, Surujon! (work in progress) 10-5 LSND a D =0.1 for LSND, JLab, ILC, MiniBooNE m

68 Examples of all constraints/prospects see e.g. NLWCP Snowmass report 10-2 a m, 5 s A' Æ invisible Hm c = 10 MeVL BaBar collection of work by B. Batell,! P. deniverville, E. Izaguirre, G. Krnjaic,! J. Mardon, M. Papucci, M. Pospelov, A. Ritz,! T. Volansky, Y. Zhong, Philip, Natalia, RE! (probably forgot someone!) 10-3 a m,±2 s favored ô DarkLight E787, E949 not shown:! e 10-4 a e MiniBooNE KÆpA' ORKA LSND ô ILC JLab Belle II SLAC mq! E137 Diamond, Schuster Batell, RE, Surujon! (work in progress) 10-5 a D =0.1 for LSND, JLab, ILC, MiniBooNE m

69 Examples of all constraints/prospects e a m, 5 s a e A' Æ invisible Hm c = 100 MeVL a m,±2 s favored E787, E949 KÆpA' ORKA ô ILC MiniBooNE JLab BaBar Belle II see e.g. NLWCP Snowmass report collection of work by B. Batell,! P. deniverville, E. Izaguirre, G. Krnjaic,! J. Mardon, M. Papucci, M. Pospelov, A. Ritz,! T. Volansky, Y. Zhong, Philip, Natalia, RE! (probably forgot someone!) not shown:! SLAC mq! E137 Diamond, Schuster Batell, RE, Surujon! (work in progress) 10-5 a D =0.1 for JLab, ILC, MiniBooNE m

70 Various proposals now exist to probe both visible and invisible A decays 10-2 A' Æ Standard Model 10-2 A' Æ invisible Hm c = 1 MeVL a m, 5 s BaBar 10-3 E774 a m,±2 s favored a e KLOE MAMI APEXêMAMI Test Runs BaBar 10-3 a m, 5 s a m,±2 s favored ô DarkLight E787, E949 e 10-4 DarkLight VEPP-3 MESA E141 Orsay APEX HPS e 10-4 a e MiniBooNE VEPP-3 KÆpA' ORKA ô ILC JLab Belle II 10-5 U m A' HGeVL 10-5 LSND a D =0.1 for LSND, JLab, ILC, MiniBooNE m

71 Outline some constraints & models! experimental opportunities! direct detection! colliders (e + e - )! fixed-target (p & e - )! indirect detection RE, Eric Kuflik, Sam McDermott, T. Volansky, K. Zurek;

72 There is lots of X-ray & γ-ray data! Data RE, Eric Kuflik, Sam McDermott, T. Volansky, K. Zurek; many others Eg 2 cm -2 s -1 sr -1 D HEAO-1: {ŒH58,109L H238,289L,»b»ŒH20,90L INTEGRAL:»{»ŒH0,30L,»b»ŒH0,15L COMPTEL:»{»ŒH0,60L,»b»ŒH0,20L EGRET: {ŒH0,360L,»b»ŒH20,60L FERMI: {ŒH0,360L,»b»ŒH8,90L E set conservative constraints on specific and simplified models

73 3 êsecd p-wave, x kd =10-6 DM annihilation p-wave, x kd =10-4 c cæe + e - s-wave m HEAO-1 INTEGRAL COMPTEL EGRET FERMI galactic constraints can be stronger than CMB for p-wave suppression

74 DM decay (example) fæe + e - +FSR m HEAO-1 INTEGRAL COMPTEL EGRET FERMI opportunities exist for collaborations to optimize data analysis for DM

75 Summary many simple, well-motivated, viable candidates of sub-gev DM exist rich phenomenology: direct, indirect, colliders, fixed-target many opportunities for new experiments Cross section [cm 2 ] (normalised to nucleon) ? 10-1 Cross section [cm 2 ] (normalised to nucleon) WIMP Mass [GeV/c 2 ]

Direct Detection of! sub-gev Dark Matter

Direct Detection of! sub-gev Dark Matter Rouven Essig C.N. Yang Institute for Theoretical Physics, Stony Brook Sackler Conference, Harvard, May 18, 2014 An ongoing program Direct Detection of sub-gev Dark