MACRO Atmospheric Neutrinos

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1 MACRO Atmospheric Neutrinos 1. Neutrino oscillations 2. WIMPs 3. Astrophysical point sources Barry Barish 5 May 00

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8 µ Neutrino induced upward-travelling muons are identified by the time-of-fligth method ν scintillator Τ 1 streamer track Τ 2 scintillator 1/β = (T 2 -T 1 ) * c / l

9 External ν-interactions Internal ν-interactions 642 used in neutrino flux analysis 213 no cut L ABS > 2 m 55 detector construction 116 used in neutrino flux analysis Different data sets are used in the different searches in order to optimize the ratio SIGNAL / BACKGROUND

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28 Conclusions ƒ MACRO: through-going muons : angular distribution more regular than in the past, sterile neutrino disfavored at ~ 2 sigma low energy events: 90% region of oscillation parameters in favor of oscillation ƒ SuperKamiokande SOUDAN2 MACRO are consistent

29 WIMPS indirect detection ƒ WIMP capture in gravitational field of the sun or the earth ƒ WIMP-WIMP annihilation ƒ Detect the emitted neutrinos ν χ v<v esc Earth or Sun χ

30 WIMPS indirect detection ƒ high energy upward muons µ hadrons ν µ points to sun or earth s center

31 Supersymmetric WIMPS Neutralino ƒ The most interesting dark matter candidate is the Neutralino χ ~ γ 0 ~ ~ ~ 0 0 c c Z c H c H = ƒ In MSSM, mass, cross section, etc are determined by three parameters tan β v / v,, µ (where 0, χ photino M 2 M and when µ 0, χ Higgsino ~ ~ ~ 0 0 H = sinβ H + cosβ H ) ~ γ 0

32 WIMPS capture and annihilation ƒ Capture local dark matter density ρ = 0.3 GeV/cm 3 dark matter velocities Maxwell distribution Earth velocity relative to galaxy v = 300 km/sec Earth model (Anderson) ƒ WIMP Annihilation Cross Sections Capture rates calculated by Gould Annihilation process similar to e + e -, except for different branching ratios χχ uu, dd, ss, bb, cc, ττ, gg,... jets

33 WIMPS capture rate in the earth χχ uu, dd, ss, bb, cc, ττ, gg,... jets

34 WIMPS upward muon flux ƒ WIMP annihilation in the earth χχ uu, dd, ss, bb, cc, ττ, gg,... jets» mean free path for strong interaction in the center of earth (r ~ 13 g/cm 3 ) is short» length ~ 0.1cm, implies that any particle with τ >> sec will interact before it decays and will not make high energy neutrinos

35 WIMPS angular size of the signal ƒ Sun source size ~ 0.5 deg angle between neutrino and muon angular resolution of detector

36 WIMPS angular size of the signal ƒ Earth source size ~ 14 0 (20 GeV/M) 0.5 angle between neutrino and muon angular resolution of MACRO

37 WIMPS Upward muons from Earth ƒ Distribution relative to the zenith ƒ exposure 2620 m 2 yr ƒ 517 events

38 WIMPS upward muon flux limits ƒ Center of Earth (517 events) ƒ Sun (762 events, including semicontained)

39 WIMPS Upward muons from the Sun ƒ angular separation from sun ƒ exposure 890 m 2 sr ƒ 762 events (+semicontained)

40 WIMPS Supersymmetric Models ƒ MACRO flux limits from Earth ƒ Varying model parameters (Bottino et al)

41 WIMPS Supersymmetric Models ƒ MACRO flux limits from Sun ƒ Varying model parameters (Bottino et al)

42 WIMPS comparison with DAMA ƒ MACRO flux limits from Earth ƒ Varying model parameters (Bottino et al) ƒ DAMA requires relatively high cross section with earth elements and/or high local density.

43 MACRO WIMP Indirect Searches ƒ MACRO has performed searches for astrophysical point-sources of neutrinos, including earth and sun. ƒ No signal indicated from either the earth or sun ƒ For the Earth and Sun, flux limits have been interpreted with respect to neutralino dark matter models. ƒ These searches are complementary to both accelerator and direct CDM searches.

44 MACRO WIMP Indirect Searches ƒ The comparison between MACRO limits and neutralino models suggested by the positive observation from DAMA are of particular interest.! The current MACRO data significantly limit the allowed range of models, particularly at lower M χ.! Future MACRO data will be able to confront most of the allowed model region.

45 Neutrino Astronomy } External interactions No 2 m cut Detector construction Internal interactions 1026 upgoing µ to search for point sources correlation with GRB

46 What cone for point source search? The angle Θ µ ν evaluated by means of simulation : ν spectra dn /de ~ E γ kinematics of ν µ CC interactions multiple scattering of µ through the rock detector angular resolution Fraction of signal in 3 0 half cone cos θ γ = 2.0 γ = Atmospheric ν background simulation : in declination bands δ = 5 0, 100 mixings of local coordinates and times of real events

47 Cumulative analysis for selected sources Sources : 40 selected, 7 with TeV γ-emission, 220 SN remnants, 129 Egret sources Expected rates in MACRO assuming Φ ν ~ Φ γ : 5x10-3 ev/yr from Crab Nebula 1x10-2 ev/yr from MKN Normalized distributions for 40 sources half-cone data expected bck Events inside cone 3 0 half-cone Events inside cone 5 0 half-cone Events inside cone No excess (Flux limits are ~ 20 times higher than largest expected signal)

48 Search for clusters of upward-going muons Events Events Normalized distributions half-cone data expected bck N o of events in the cone 3 0 half-cone N o of events in the cone 5 0 half-cone n o of events in the cone No statistically significant clusters

49 MACRO Area for Astronomy Analysis Probability for ν to produce a µ with E µ > 1 GeV observed in MACRO E ν (GeV) P ν µ P ν µ + µ yield x x x x x x x x x x 10-4

50 Flux Limits for Selected Sources Limits at 90 % c.l. (E µ > 1 GeV, γ = 2.1) Source δ Events in 3 0 Back Ground in 3 0 Classical µ flux limit Feldman Cousins µ limit Previous µ best limit ν flux limit (10-14 cm -2 s -1 ) (10-14 cm -2 s -1 ) (10-14 cm -2 s -1 ) (10-5 cm -2 s -1 ) SMC X LMC X SN1987A Vela P (Baksan) 1.15 (Baksan) 0.78 (IMB) SN Gal Cen (Baksan) 0.14 Kep Geminga Crab (IMB) 2.6 (Baksan) MRK

51 Search for ν and GRB correlation GRBs from April 1991 up to May 1999 from BATSE Catalogues (3B and 4B) GRBs and neutrino events vs year events year The transience of GRBs improves the association with observed ν events using arrival direction and time

52 Cumulative analysis Search cones of 3 0, 5 0, 10 0 have to contain 71%, 85% and 97% of the signal Background estimate : 100 random associations of local angles from upward-going events with times + a shift in the local angles of ± Normalized distributions of the number of upward-going µ s and expected background in cones with respect to direction of GRBs Expected mc background data 3 0 half-cone Events inside cone half-cone Events inside cone 10 0 half-cone Events inside cone No evidence for an excess of events from GRB directions

53 GRB-UPµ time (s) Space-Time correlation Search window : 10 0 around GRBs and ± 200 s Background estimate : 40 shifts of time difference (minimum s; maximum s) between upward-going µ s and GRBs MACRO area for average burst : 130 m 2 γ-burst - µ TIMES (S) γ-burst - µ TIMES (S) Time GRB/upgoing µ vs angular separation Cos (γ-burst - µ DIRECTIONS) events observed in 10 0, 0.04 expected 0 cos θ GRB-UPµ Upper limit x µ 0 cm for 0.4average burst 1 Cos (γ-burst - µ DIRECTIONS) 10 0

54 CONCLUSIONS MACRO data on atmospheric neutrinos favor ν µ Æ ν τ oscillation hypothesis Upper limits for Dark Matter searches and ν astronomy : No signal Limits for WIMPs (neutralinos) constrain MSSM models MACRO is monitoring the visible sky using one of the largest sample of high energy neutrinos