Exploring the Geo-Exploring the Geo-reactor Hypothesis with reactor Hypothesis with

NeutrinosNeutrinos

Jelena Maričić KamLAND Collaboration

March 24th 2007DOANOW WorkshopUniversity of Hawai’i

OutlineOutline• The geo-reactor hypothesis• Limits on the geo-reactor

hypothesis with KamLAND experiment

• Prospects of verifying the geo-reactor hypothesis with future Hanohano experiment

• Summary and conclusion

Uranium in the Core?Uranium in the Core?

• Radical hypothesisRadical hypothesis • If it is there, it may undergo fission.• Natural nuclear reactor with power up to 10 TW operating in the center of the Earth, proposed by M. Herndon as the

energy source of geo-magnetic field (geo-

magnetic field reversals and higher ratios of 3He/4He observed in volcanic plumes in some places).

• Although not a mainstream theory, not ruled out by any evidence.• If the geo-reactor exists, its anti-neutrino

flux is visible in KamLAND and Hanohano in future!

Why do we Care about Verifying a Radical Why do we Care about Verifying a Radical Hypothesis such as Geo-reactor Sitting in the Hypothesis such as Geo-reactor Sitting in the

Earth’s Core? Earth’s Core?

It is a freebie. It can be verified with existing experiments and

future planned experiments

Geo-reactor

Discovered: Does not exist or/and too small: - revolutionize geology - independent check that there are no surprises in the energy region where we do not expect them

Differentiating between Geo-Differentiating between Geo-neutrinos and Geo-reactor Neutrinosneutrinos and Geo-reactor Neutrinos

- Geo-neutrinos emitted in the decay chains of 40K, 232Th, 238U and can have energies up to 3.4 MeV

- Geo-reactor neutrino’s energy spectrum approximately resembles the spectrum of a typical commercial nuclear reactor and these neutrinos may have energies that extend all the way to 9 MeV

- Any positive signal above 3.4 MeV limit for geo-neutrinos must be attributed to reactor like neutrinos

Inverse β-decay energythreshold1.8 MeV.

e p+ e+ + nInv. reaction:

No geo-neutrinos above 3.4 MeV

Geo-reactor Geo-reactor Search with KLSearch with KL

Geo-reactor Geo-reactor Search with KLSearch with KL

• KamLAND detects reactor anti-neutrinos

• The possible surplus of detected events implies that there may be another source of anti-neutrinos that have not been accounted for.

• Proposed 3-10 TW georeactor if exists would produce anti-

neutrino signal of 4-14% of the KamLAND signal.

• The goal is to set an upper limit on the power of the hypothetical geo-reactor.

Is it there and if so, how large is it?

Motivation for Geo-reactor SearchMotivation for Geo-reactor SearchMotivation for Geo-reactor SearchMotivation for Geo-reactor Search

• Incoming daily flux varies due to nuclear reactors varying work

regime.• Rate from the putative geo-reactor

very small!• It is assumed that geo-reactor

power is constant on the data taking time scale.

Small positive offset of 0.03e/daywith VERY LARGE ERROR may be present, for 0 ev/day expected! Phys.Rev.Lett.94:081801,2005

Small positive offset of 0.03e/daywith VERY LARGE ERROR may be present, for 0 ev/day expected! Phys.Rev.Lett.94:081801,2005

Time integratedplot

Survival probabilityLarge error!

90% C.L.KamLAND

Confidence Levels on Confidence Levels on the Geo-reactor the Geo-reactor

PowerPower

Very wide minimumVery wide minimum

Comparison of the Best Fit Result with Geological Data

The best fit value is 6 TWand 90% C.L. limit is 19 TW

Based on 515 days of livetimeBased on 515 days of livetimeBased on 515 days of livetimeBased on 515 days of livetime

0.0102 events/TW·day0.0102 events/TW·day

Simulation of the Improving Limits on Simulation of the Improving Limits on the Geo-reactor Power with 2.5 more the Geo-reactor Power with 2.5 more

datadata• Simulations with 2.5 more data!• Value of the geo-reactor power treated as a free parameter.

68%

90%

68%

90%

90%

68%

Rate onlyNo parameter constraints

Rate only+ parameter constraints

Rate + shape+ parameter constraints

Tightest Tightest limitlimit

Tightest Tightest limitlimit

R0 = (-6 10) TWR0 = 14 TW at 90%C.L.

R0 = (-4 5) TWR0 = 9 TW (90%C.L.)

R0 = (0 4) TWR0 = 7 TW (90%C.L.)

R0 = (0 4) TWR0 = 7 TW (90%C.L.)

ExpectationWith 2.5 moredata

Geo-reactor Search with KamLAND Geo-reactor Search with KamLAND SummarySummary

Geo-reactor Search with KamLAND Geo-reactor Search with KamLAND SummarySummary

• 90% C.L. is 19 TW.90% C.L. is 19 TW.• Simulations with Simulations with 2.5 times more data 2.5 times more data shows that shows that

there will be improvement in the limits, but it is still there will be improvement in the limits, but it is still insufficient to give any final say about the geo-insufficient to give any final say about the geo-reactor. Based on the simulation:reactor. Based on the simulation:– 90 % C.L. limit 90 % C.L. limit will be loweredwill be lowered to 7 TW. to 7 TW.– The best fit The best fit will be loweredwill be lowered: (0 : (0 4) TW 4) TW

• Final result is greatly influenced by:Final result is greatly influenced by:– Error on the input neutrino mixing parameters that will not Error on the input neutrino mixing parameters that will not

improve greatly in near futureimprove greatly in near future– Background from man-made nuclear reactors that is 10-20 Background from man-made nuclear reactors that is 10-20

times larger than geo-reactor signaltimes larger than geo-reactor signal– Detector backgrounds will be decreased by a new radioactive Detector backgrounds will be decreased by a new radioactive

source calibration measurement at KamLANDsource calibration measurement at KamLAND• KamLAND size detector far away from nuclear KamLAND size detector far away from nuclear

reactorsreactors needed for high confidence (>99.99%) measurement.needed for high confidence (>99.99%) measurement. • Hawaii presents an excellent choice for a definite geo-reactor measurement ( ).

Making a more decisive Making a more decisive measurement of measurement of

geo-neutrinos with geo-neutrinos with future Hanohano future Hanohano

experimentexperiment

Hano Hano - KamLAND in Hano Hano - KamLAND in OceanOcean• Hano Hano = Hawaii Antineutrino

Detector- Hanohano = Hawaiian for “glorious, Distinctive”

• Basic Idea:- KamLAND-style anti-neutrino detector in the ocean @ 4km depth- Design: measurement of 238U and 232Th in the mantle - 25% measurement of mantle geo-

neutrinos (U/Th) - Will be able to distinguish between different geological models of the Earth.

- Will be able to detect geo-reactor neutrinos from the

1 TW or larger geo-reactor if one exists with > 4 C.L.

Planned Detector Design and Planned Detector Design and LocationLocation

Planned Detector Design and Planned Detector Design and LocationLocation

nepe Big Island

Hanohano

Oahu- Designed as 10 kton liquid scintillator detector. - Detection reaction:

4 km depth

Pier constructionconstraint!

Why Hawaii Represents Such a Why Hawaii Represents Such a Good Location for Geo-reactor Good Location for Geo-reactor

DetectionDetection• Japan presents one of

the worst locations for the geo-reactor detection while Hawaii presents one of the best locations for geo-reactor detection.

Japan

Hawaii

Commercial nuclear reactor background

Commercial nuclear reactor background

Significance and Signals for Significance and Signals for the Geo-reactor Detectionthe Geo-reactor Detection

Significance and Signals for Significance and Signals for the Geo-reactor Detectionthe Geo-reactor Detection

• Signal significance: σ = S / √(S+B)• Background rate: 30 events per 10 kT-y (3.4 < Eν(MeV) < 9.3)

• 1 TW geo-reactor signal38 events per 10 kT-y (3.4 < Eν(MeV) < 9.3)

• If the goals for backgrounds are achieved:

= 4.6 C.L. for 1 TW geo-reactor discovery

Summary and Summary and ConclusionConclusion

Summary and Summary and ConclusionConclusion

• Current upper limit on the power on the hypothetical geo-reactor has been set at 19 TW at 90% C.L.

• Simulations with larger data set show improvements but insufficient to give any final say about the existence of geo-reactor.

• Destiny of the geo-reactor will be far better resolved with Hanohano detector.

Geo-reactor Geo-reactor Pros and Cons Pros and Cons

…can explain the following unresolved question:- provide the energy source for driving the Earth’s magnetic field (0.02-10 TW of power running for more than 3 billion years!!!).- perhaps explains reversals of

the geo-magnetic field (171 reversals recorded in the last 70 million years).- provide explanation for the up to 40 times higher measured ratios

(comparing to average atmospheric ratio) of 3He/4He observed in volcanic plumes in Hawaii, Iceland some other places.

…requires substationally different inner core content:

Traditional Model (BSE): content of the inner core based on meteorites called carbonaceous chondrites. As a result, U and Th are in the form of oxides, act as lithophiles and can exist in the crust and mantle only.

Nuclear Earth Model (by M. Herndon): content of the inner core based on rare type of meteorites called enstatite chondrites. U and Th are alloyed with Fe or S, act as siderophiles and due to high density can exist in the inner core and particularly the Earth’s center.