MACROAtmospheric Neutrinos

Barry Barish

5 May 00

1. Neutrino oscillations2. WIMPs3. Astrophysical point sources

Neutrino inducedupward-travelling muons

are identified by thetime-of-fligth method

scintillator

scintillator

streamertrack

T2-T1) * c / l

External -interactions 642 used in neutrino flux analysis213 no cut LABS > 2 m 55 detector construction

Internal -interactions 116 used in neutrino flux analysis

Different data sets are used in the different searchesin order to optimize the ratio SIGNAL / BACKGROUND

Conclusions

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

SuperKamiokande SOUDAN2 MACRO are consistent

WIMPSindirect detection

WIMP capture in gravitational field of the sun or the earth

WIMP-WIMP annihilation Detect the emitted neutrinos

v<vesc

Earthor Sun

WIMPSindirect detection

high energy upward muons

hadrons

points to sun or earth’s center

Supersymmetric WIMPSNeutralino

The most interesting dark matter candidate is the Neutralino

In MSSM, mass, cross section, etc are determined by three parameters

tan / ,

sin cos

~

~ ~ ~

v v ,

(where , photino

and when 0 , Higgsino

)

2 1 2

2

0

0

1

0

2

0

0

MM

H H H

1

0

2

0

3 1

0

4 2

0

c c Z c H c H~ ~ ~ ~

WIMPScapture and annihilation

Capture local dark matter density

= 0.3 GeV/cm3

dark matter velocitiesMaxwell distribution

Earth velocity relative to galaxyv = 300 km/sec

Earth model (Anderson)

WIMP Annihilation Cross Sections Capture rates calculated by Gould Annihilation process similar to e+e-,

except for different branching ratios

uu, dd, ss, bb, cc, , gg, .... jets

WIMPScapture rate in the earth

uu, dd, ss, bb, cc, , gg, .... jets

WIMPSupward muon flux

WIMP annihilation in the earth

» mean free path for strong interaction in the center of earth (r ~ 13 g/cm3) is short

» length ~ 0.1cm, implies that any particle with >> 10-11 sec will interact before it decays and will not make high energy neutrinos

uu, dd, ss, bb, cc, , gg, .... jets

WIMPSangular size of the signal

Sun source size ~ 0.5 deg angle between neutrino and muon angular resolution of detector

WIMPSangular size of the signal

Earth source size ~ 140 (20 GeV/M)0.5

angle between neutrino and muon angular resolution of MACRO

WIMPSUpward muons from Earth

Distribution relative to the zenith exposure 2620 m2yr 517 events

WIMPSupward muon flux limits

Center of Earth (517 events) Sun (762 events, including

semicontained)

WIMPSUpward muons from the Sun

angular separation from sun exposure 890 m2sr 762 events (+semicontained)

MACRO flux limits from Earth Varying model parameters

(Bottino et al)

WIMPSSupersymmetric Models

MACRO flux limits from Sun Varying model parameters

(Bottino et al)

WIMPSSupersymmetric Models

MACRO flux limits from Earth Varying model parameters (Bottino

et al) DAMA requires relatively high cross

section with earth elements and/or high local density.

WIMPScomparison with DAMA

MACRO has performed searches for astrophysical “point-sources” of neutrinos, including earth and sun.

No signal indicated from either the earth or sun

For the Earth and Sun, flux limits have been interpreted with respect to neutralino dark matter models.

These searches are complementary to both accelerator and direct CDM searches.

MACROWIMP Indirect Searches

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.

Future MACRO data will be able to confront most of the allowed model region.

MACROWIMP Indirect Searches

Neutrino Astronomy External interactions

No 2 m cut Detector construction

Internal interactions 1026 upgoing to search for

• point sources• correlation with GRB

}

The angle evaluated by means of simulation :

• spectra dN /dE ~ E

• kinematics of CC interactions

• multiple scattering of through the rock

• detector angular resolution

What cone for point source search ?

Fraction of signal in 30 half cone

cos 0.15 0.77 0.72

0.35 0.90 0.85

0.55 0.91 0.87

0.75 0.91 0.87

0.95 0.91 0.87

Atmospheric background simulation : in declination bands = 50, 100 mixingsof local coordinates and times of real events

Cumulative analysis for selected sources

30 half-cone

50 half-cone

1.50 half-cone

Sources : 40 selected, 7 with TeV -emission, 220 SN remnants, 129 Egret sources

Expected rates in MACRO assuming ~ :5x10-3 ev/yr from Crab Nebula1x10-2 ev/yr from MKN 421

No excess (Flux limits are ~ 20 times higher thanlargest expected signal)

dataexpected bck

Normalized distributions for 40 sources

Search for clusters of upward-going muons

Normalized distributions

30 half-cone

50 half-cone

1.50 half-cone

dataexpected bck

No statistically significant clusters

Probability for to produce a with E > 1 GeV observed in MACRO

E (GeV) P P

101 1.27 x 10-10 9.25 x 10-11

102 9.73 x 10-9 6.68 x 10-9

103 5.99 x 10-7 4.12 x 10-7

104 1.56 x 10-5 1.14 x 10-5

105 1.39 x 10-4 1.21 x 10-4

MACRO Areafor

AstronomyAnalysis

yield

Source Eventsin 30

BackGround

in 30

Classical fluxlimit

(10-14 cm-2 s-1)

FeldmanCousinslimit

(10-14 cm-2 s-1)

Previousbestlimit

(10-14 cm-2 s-1)

fluxlimit

(10-5 cm-2 s-1)

SMC X1 -73.50 3 1.9 0.58 0.64 --- 0.18

LMC X4 -69. 50 0 1.8 0.28 0.160.36

(Baksan)0.09

SN1987A -69.30 0 1.8 0.28 0.161.15

(Baksan)0.09

Vela P -45.20 1 1.4 0.54 0.510.78

(IMB)0.16

SN1006 -41.40 1 1.2 0.56 0.56 --- 0.17

Gal Cen -28.90 0 0.9 0.46 0.340.95

(Baksan)0.14

Kep1604 -21.50 2 0.8 1.00 1.12 --- 0.31

Geminga 18.30 0 0.4 1.29 1.143.1

(IMB)0.40

Crab 22.00 1 0.4 2.14 2.372.6

(Baksan)0.66

MRK 501 38.80 0 0.1 5.19 5.22 --- 1.59

Flux Limits for Selected Sources

Limits at 90 % c.l. (E > 1 GeV, = 2.1)

Search for and GRB correlation

GRBs and neutrino events vs year

GRBs from April 1991 up to May 1999from BATSE Catalogues (3B and 4B)

The transience of GRBs improves the association withobserved events using arrival direction and time

“Cumulative” analysisSearch cones of 30, 50, 100 have to contain

71%, 85% and 97% of the signal

Background estimate : 100 random associations of local angles fromupward-going events with times + a shift in the local angles of ± 100

100 half-cone

30 half-cone

Normalized distributions of the number of upward-going ’s and expected background in cones with respect to direction of GRBs

No evidence for an excess of events from GRB directions

50 half-cone

Expected background

Space-Time correlationSearch window : 100 around GRBs and ± 200 s

Background estimate : 40 shifts of time difference(minimum -4000 ÷ 4000 s; maximum -80000 ÷ 80000 s)between upward-going ’s and GRBs

MACRO area for average burst : 130 m2

Time GRB/upgoing vs angular separation

cos GRB-UP

0 events observed in 100, 0.04 expected

Upper limit 7.3 x 10-10 cm-2 for average burst

GR

B-U

P

time

(s)

100

CONCLUSIONS

MACRO data on atmospheric neutrinos favor

oscillation hypothesis

Limits for WIMPs (neutralinos) constrain MSSM models

Upper limits for Dark Matter searches and astronomy :

No signal

MACRO is monitoring the “visible” sky using one of the largest sample of high energy neutrinos