Exploring the Dark Sector with Neutrinos

Transcription

1 Exploring the Dark Sector with Neutrinos Sungkyunkwan University, Korea Exploring the Dark Sector 1503 Conference Room, 5th fl., KIAS March 16 (Mon) March 20 (Fri), 2015

2 Overview Motivation Neutrino Telescopes and Detectors Latest results Dark Matter Self-annihilation cross section WIMP Nucleon scattering cross section Future Prospects and Conclusions 2

3 3

4 ICECUBE Gigaton Neutrino Detector at the Geographic South Pole 5160 Digital optical modules distributed over 86 strings Completed in December 2010, start of data taking with full detector May 2011 Data acquired during the construction phase has been analyzed Neutrinos are identified through Cherenkov light emission from secondar y particles produced in the neutrino interaction with the ice νμ 4 μ

5 Neutrino Telescopes / Detectors ANTARES is located at a depth of 2475 m in the Mediterranean Sea, 40 km offshore from Toulon Consists PMTs on 12 lines with 25 storeys each. Detector was competed in May 2008 Baksan Underground Scintillator Telescope with muon energy threshold about 1 GeV using 3,150 liquid scintillation counters IceCube at the Geographic South Pole PMTs in Digital optical modules distributed over 86 strings instrumenting ~1km 3 Physics data taking since 2007 ; Completed in December 2010, including DeepCore lowenergy extension IceTop IceCube DeepCore Operating since Dec 1978 ; More than 34 years of continuous operation Lake Baikal, Siberia, at a depth 1.1 km NT36 in 1993 NT200 (since Apr 1998) consists of one central and seven peripheral strings of 70m length Super-Kamiokande at Kamioka uses 11K 20 PMTs 50kt pure water (22.5kt fiducial) watercherenkov detector Operating since

6 Motivation 6

7 Dark Matter at all scales Evidence Planck / WMAP A. Kravtsov Begeman, Broels & Sanders (1991) Gravitational Lensing in the Galaxy Cluster Abell 2218 NASA / A. Fruchter / STScI CMB Universe Local Group Structure formation Milky Way Galaxy clusters CRslocal e + e - Sun Rotation curves Earth direct Dwarf ~1kpc spheriodals ~100kpc gravitational lensing ~Mpc Extra-galactic Galactic Center Halo Sub-halos Galaxies Objects or sources expected to produce significant annihilation signals ~Gpc Rott, Neutrino 2012 Nucl.Phys.Proc.Suppl (2013) Indirect Targets for ν,γ Individual sources and diffuse 7

8 Dark Matter Annihilation Signals Interactions that determine the WIMP relic abundance also lead to self-annihilations in the present epoch Identify overdense regions of Dark Matter self-annihilation can occur at significant rates Pick prominent Dark Matter target Understand backgrounds Features in the signal enhance to chance distinguish backgrounds Line / End-point χ χ Annihilation Rate ~ρ 2 ( Decay Rate ~ρ ) non-relativistic Annihilation Products Decay Messengers W +,Z,τ +,b,... e ±,υ,γ, p,d,... W,Z,τ,b,... e,υ,γ, p,d,... χ e -,e + ν E mχ χ γ p 8

9 Galactic Halo <σav> 9

10 Galactic Halo as seen by IceCube Galactic Dark Matter Halo Most natural target for neutrino telescopes >99% duty cycle 4πsr field of view No known backgrounds very small halo profile dependence Jfactor for halo and galactic center similar 10

11 up-going down-going Galactic Halo Galactic Center (GC) on the southern hemisphere large backgrounds from down-going muons Search for anisotropy on Northern hemisphere high-purity neutrino sample (up-going muon events) IceCube 22-strings Halo Analysis Phys.Rev.D84:022004, days ( ) on-source / off-source Assume annihilation into νν, bb, µµ, ττ, WW IceCube 79-strings multipole analysis 316 days ( ) Galactic Center multipole expansion of ν arrival direction R. Abbasi et al., Phys. Rev. D 84 (2011) M. Ackermann et al., Astrophys. J. 761 (2012) 91. Eur. Phys. J. C75, 20 (Jan 2015) 11

12 Galactic Center <σav> 12

13 Galactic Center Search Use IceCube external strings as a veto: 3 complete layers around DeepCore (~ 375m) Full sky sensitivity: access to southern hemisphere up-going down-going Separate Low energy and High energy optimizations: GC is above the horizon Fiducial volume in central strings refined muon veto from surrounding layers Use scrambled data for background estimation sensitivity to reach down to WIMP masses of 30GeV 13

14 ANTARES Preliminary result shown at Moriond 2014 ANTARES - Galactic Center Dataset: 1321days from Neutrino spectra from Cirelli et al (arxiv: ) ANTARES is on the Northern Hemisphere, benefit from low backgrounds in upgoing neutrino sample Preliminary 14

15 Super-K - Galactic Search Search for a diffuse signal from GC + Milky Way halo Assume annihilation into νν, bb, or WW Use all samples e-like + mulike FC + PC (2806 days) +UPMU (3109 days) Use all neutrino flavors and topologies FC UPMU PC R. Wendell Neutrino Preliminary 15

16 Galactic Center 10 years Super K 5 years ANTARES 1 year IceCube Exclude positron fraction excess AMS02 / PAMELA Preliminary More results by the summer 16

17 Dark Matter Decay 17

18 High-energy neutrino search 37 events (9 track-like, 28 showers) observed in 3 years of IceCube data 4th year yielded 17 events ( ) Mesons including charm quarks in the atmosphere decay immediately to produce neutrinos, known as prompt neutrinos which are not observed yet. ERS, or Enberg et al. Phys. Rev. D 78, (2008) is used as a baseline prompt model Significance are based on the exact neutrino flux model, not including the uncertainty of the model. Atmospheric Bkg : CR Muon ( 8.4±4.2 ), Conv. Neutrino ( ), IceCube Collaboration, Science 342, (2013), IceCube Collaboration, Phys. Rev. Lett 113, (2014) E -2 spectrum predicts too may neutrinos above ~2 PeV. So, a cutoff or steeper spectrum needed. 18

19 Origin of the high-energy neutrinos? Extra Galactic Gamma Ray Burst Galactic Galactic Center Waxman & Bahcall IC40 limit IC40 Guetta et al. IC40+59 Combined limit IC40+59 Guetta et al. IceCube Collaboration - Nature Vol 484, 351 (2012) Galactic Plane Neutrino energy (GeV) Active Galactic Nuclei / Starburst Galaxies 19

20 Heavy Dark Matter Intriguing overlap in energy of the first two 1 PeV cascade events of IceCube high energy event sample Could this be dark matter? example: B. Feldstein, A. Kusenko, S. Matsumoto, and T. Yanagida arxiv: v1 [hep-ph] Evidence: - 2.4PeV Dark Matter Particle mass - Flux can be related to the lifetime τdm IceCube Bound on lifetime ~10 27 s Phys.Rev.D84:022004,2011 Models Singlet fermion in an extra dimension Hidden Sector Gauge Boson Gravitino Dark Matter with R-Parity Violation 20

21 Heavy Dark Matter Heavy Decaying DM (example χ νh) Focus on most detectable feature (neutrino line) Backgrounds steeply falling with energy, highest energy events provide best sensitivity Continuum and spacial distribution could help identify a signal Bounds from Fermi-LAT and PAMELA derived from search for bb annihilation channel (dominant decay channel of Higgs). Bounds on Dark Matter Lifetime / Br( x) [s] Decay Heavy DM bounds with neutrinos, see also Murase and Beacom JCAP 1210 (2012) 043 Esmaili, Ibarra, and Perez JCAP 1211 (2012) Decay x Rott Kohri Park arxiv: This analysis IceCube PRD (2011) Fermi LAT ApJ (2012) Esmaili et al. (2012) PAMELA Data JCAP (2013) * m [GeV]

22 Solar WIMPs σscatt 22

23 Solar WIMPs ν µ 23

24 Overview of limits ANTARES JCAP 1311 (2013) 032 IceCube Phys. Rev. Let. 110, (2013) Super Kamiokande Astrophys.J. 742 (2011) 78 Baksan JCAP 1309 (2013) 019 Spin-independent scattering Spin-dependent scattering M. Danninger & C. Rott Solar WIMPs Unraveled -- Invited Review for Physics of the Dark Universe (Nov 2014) Neutrino Telescopes provide world best limits on SD WIMP proton scattering 24

25 1 year IceCube completed detector 25

26 Future Prospects 26

27 Future of IceCube Make it better Precision detector with ~GeV threshold Make it bigger 27

28 Future of IceCube Make it better Precision detector with ~GeV threshold Make it bigger 28

29 Galactic Center IceCube Gen 2 arxiv:

30 High Mass DM Sensitivity RKP14 τdm= s Murase, Laha, Ando, Ahlers Sensitivity for M31 + Virgo Cluster through-going muon tracks 5x sensitivity assumed for Gen2 (1) ES13 (mdm=3.2pev) DM νeνe(12%) qq(88%) (2) RKP14 (mdm=2.4pev) DM νh (3) HKS14 (mdm=2.4pev) DM l ± W DM νz DM νh 2 : 1 : 1 A. Esmaili and P. D. Serpico, JCAP1311, 054 (2013) T. Higaki, R. Kitano, and R. Sato, JHEP1407, 044 (2014), C. Rott, K. Kohri, and S. C. Park (2014), VHDM scenario can be ruled out or in three-to-five years 30

31 PINGU LOI arxiv: PINGU - Precision IceCube Next Generation Upgrade PINGU upgrade plan Instrument a volume of about 5MT with ~40 strings each containing optical modules Dense instrumentation energy threshold ~1GeV Rely on well established drilling technology and photo sensors Create platform for calibration program and test technologies for future detectors Physics Goals: Precision measurements of neutrino oscillations (mass hierarchy,...) Test low mass dark matter models y(m) An example PINGU geometry (40 strings) Note: PINGU geometry is still being optimized λscat eff 47m ~ 2 scattering length λabs [2011] The Pygos Group IceCube String DeepCore String Infill String (PINGU) x(m) 31

32 PINGU Dark Matter Sensitivity Spin-dependent scattering Spin-independent scattering Explore Low mass WIMP region PINGU capable to comfortably test DAMA/Libra 32

33 Impact of astrophysical uncertainties M. Danninger & C. Rott Solar WIMPs Unraveled -- Physics of the Dark Universe (Nov 2014) interactive tool to study impact of astrophysical parameters Note: direct detection limits shown for standard halo assumptions / velocity dependence not yet implemented 33

34 WIMP Sensitivity Super-K / Hyper-K Neutrinos from stopped π + decay at rest in the Sun: Consistent results with Bernal et al JCAP 1308 (2013) 011 Rott, Siegal-Gaskins, Beacom PHYSICAL REVIEW D 88, (2013) C. Savage et al. JCAP 0904 (2009) 010 Previous searches relied on high energy neutrinos directly f r o m t h e d e c a y s o f annihilation products Model the full hadronic shower in the Sun WIMP sensitivity continues to improve for low masses Minimal dependence on mix annihilation channels New key detection channel t o c o m p l i m e n t o t h e r searches Super-K data can already be used to test DAMA/Libra Great Prospect for future detectors 34

35 Conclusions Striking WIMP signatures provide high discovery potential for indirect searches Super-K and IceCube provide world best limits on the SD WIMP-Proton scattering cross section Neutrinos extremely sensitive to test low-mass WIMP scenarios at current and future detectors New detection channel with low-energy neutrinos offers additional discovery potential PeV Decaying DM scenarios testable at IceCube Gen2 35

36 Thanks! 36

37 Impact of velocity distribution Explore the change in capture rate using different velocity distributions obtained from dark matter simulations f(v) in Galactic frame at solar circle Choi, Rott, Itow JCAP 1405 (2014) 049 A comparison of captures rates for different WIMP velocity distributions show that overall changes in the capture rate are smaller than 20% 43

38 Halo Uncertainties on the capture rate C.Rott, T. Tanaka, Y. Itow, JCAP09(2011)029 Effect on Capture Rate ΓC WIMP Mass Assume a Maxwellian velocity distribution of the WIMPs outside the potential well of the Sun with a dispersion of vd Circular velocity of the Sun is assumed to be vsun=220km/s While uncertainties in the dark matter distribution can result in significantly different annihilation rates in the Sun, results tend to be on the conservative side Direct detections have to deal with the same uncertainties, and interpretations of results is by no means simpler Sun irons out fluctuations in the local density or velocity distribution 44