Download GeoNeutrino Analysis in KamLAND: Input and Desiderata

XXXIXth RENCONTRES DE MORIOND 2004 –
ELECTROWEAK INTERACTIONS
AND UNIFIED THEORIES
La Thuile, Aosta Valley, Italy (March 21-28, 2004)
GeoNeutrino Analysis in KamLAND:
Input and Desiderata
Anna Maria Rotunno
Dip.to di Fisica & Sez. INFN, Bari, ITALY
[email protected]
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Outline:
GeoNeutrinos
GeoNeutrinos
Geochemical
GeochemicalInput
Input
Desiderata
Desideratafor
forKamLAND
KamLANDData
DataAnalysis
Analysis
Conclusions
Conclusions
Report on WORK IN PROGRESS with:
G.L. Fogli, E. Lisi, A. Palazzo
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
Geoneutrinos
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Anna Maria Rotunno
XXXIXth RENCONTRES
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MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
Earth is an Anti-Neutrino Star
νe
Radioactive Decays in
U,Th,K …
CRUST and MANTLE
νe
- Radiogenic Heat (40-60 % of 40 TW)
- Geo – Antineutrinos observable by terrestrial detectors (liquid scintillators)
Geo – νe detection
Important Constraints for
Earth’s energetics
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
Geochemical Input
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
Radioactive decay of U, Th, and K in the Earth is thought to be the
main source of the Earth heat flux (*)
νe events from Th and U decay are accessible for the first time in
KamLAND (νe from K decay are below threshold for detection).
ΦTh(νe)
and
ΦU(νe)
in KamLAND are weighted by 1/L2
&
(Th, U, K) are more abundant in the CRUST than in the MANTLE
some INPUT on the relative Th, U (and K) abundances
in different Earth reservoirs is needed
to make sense of
(*) For a recent review See
FUTURE GEONEUTRINO DATA
G. Fiorentini et al., hep-ph/0309013
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
QUESTIONS:
What do we really know about such aboundances?
What do we expect to know from Th,U Geo-νe data ?
Usually advertised goal:
“ measure the Earth Radiogenic Heat”
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
HOWEVER,
even if the Th and U components were known with no error,
there would be INTRINSIC LIMITATIONS to this goal:
1) K component unmeasurable (in KamLAND);
must be inferred from K/U or K/Th estimates
2) K/U, K/Th bulk ratios not constrained by meteoritic data, since K is
geochemically “volatile” (= lower condensation temperature than Th, U)
3) Crust+Mantle sampling data + geochemical arguments
unlikely to reduce the K/U, K/Th uncertainty below, say, 10÷15%
(*)
4) Possible significant amount of Potassium (but not of Th, U) in Earth’s core (**)
5) Possible severe overestimation of the usually quoted Earth’s heat flux,
44±1 TW (***) , by oceanic component systematics.
Possible revisited value of Earth’s heat flux : 31±1 TW (****)
(*)
K.P. Jochum et al., Nature 306, 431 (1983)
(**) V. Rama Murthy et al., Nature 423, 163 (2003); Lee & Jeanloz, Geophys. Rev. Lett. 30, 2212 (2003)
(***) H.N. Pollack et al., Rev. Geophys. 31, 267 (1993)
(****) Hofmeister & Criss, preprint, submitted to Tectonophysics
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
QUESTION:
Can one say something useful
to GEOPHYSICS by
JUST MEASURING
Th and U νe fluxes ?
YES.
ONE EXAMPLE
. . .
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
•
Bulk Th/U ratio in the Earth should be close to meteoritic value:
(Th/U)Earth = (Th/U)chondritic ~ 3.8
•
No geochemical or cosmochemical arguments
to think otherwise
Th more easily partitioned than U in melt (= Crust) than in solid (= Mantle)
(Th/U)Crust > 3.8
(Th/U)Mantle < 3.8
(probably 4.5÷5.5)
(probably 2 ÷ 3)
observations
match expectations
•
Geo-ν experiments dominated by Crust contribution (including KamLAND)
should then observe
(Th/U)Crust-dominated > 3.8
(up to local crust fluctuations)
•
This datum + Crust and Upper Mantle sampling might provide an estimate of:
(Th/U)Lower-Mantle by mass balance arguments (*)
Can infer MANTLE LAYERING if
(Th/U)Lower-Mantle (Th/U)Upper-Mantle
(*) D.L. Turcotte et al., J. Of Geophys. Res. 106, 4265 (2001)
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
PROBLEM:
How do we ATTACH ERRORS to (Th,U) estimates?
1st ORDER SOLUTION (Fiorentini et al.):
evaluate central values and errors from spread of published (Th,U) estimates;
e.g., attach ±3 σ significance to extremal values.
A good starting approach but . . .
. . . LIMITATIONS:
1) published estimates are often “duplicates” (≡ may agree too well )
2) without a criterion to discard obsolete estimates or unreliable
outliers, NO PROGRESS POSSIBLE with this approach
No other way out than carefully sifting the available geo-literature, identifying
virtues and problems of each estimate, selecting the more reliable and complete ones,
WORK IN PROGRESS
and evaluating from scratch the uncertainties
UNFORTUNATELY: error evaluation
not common practice in geo-sciences !
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
E.G. only recently (2003) a geochemical Earth model has appeared, where
input uncertainties are at least well-defined (although questionable in size)
and correctly propagated to output element abundances (*)
Palme 2003 estimates for the bulk silicate Earth (= Mantle + Crust) at 1σ:
[Th] = 83.5 (1±0.12) ppb
(part per billion in weight)
[ U ] = 21.9 (1±0.12) ppb
(part per billion in weight)
with correlation ρ = 0.38 (our provisional estimate)
Th/U 3.8 (1±0.14)
(bulk Earth)
This estimate can actually be refined through a
more careful use of meteoritic (chondritic) data
IMPORTANT TASK
since (Th/U)Earth plays a pivotal role in Mantle-Crust balances:
(Th/U)Crust > (Th/U)Earth
(testable by KamLAND)
(*)
WORK IN PROGRESS
(Th/U)Mantle < (Th/U)Earth
(useful to test Lower/Upper Mantle differences)
H. Palme & H. O’Neill, in “Treatise on Geochemistry”, Elsevier, 2003
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
This global information must be folded with careful estimates of
“geometrical” (Th/U) variations,
both VERTICAL (Crust layers + Mantle layers) and HORIZONTAL (Crust types)
In principle, large amount of data and constraints are available, but dedicated
global studies are still lacking.
Interaction with geo-science community would be beneficial.
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
Desiderata for
KamLAND Data Analysis
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
What can we know from KamLAND?
A model-independent check that, e.g., (Th/U)Crust > 3.8, requires
Th, U
Current (binned) data
FREE
constraints, of course, very weak
BINNED ANALYSIS
Since the statistics will be
very low for quite some
time,
it is necessary to use
Th/U = 3.8
as much information
as possible.
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
FIRST STEP:
avoid binning and tag each event in energy
(recoverable from KamLAND plots)
Unbinned analysis of KamLAND data (through maximum likelihood)
yields slightly TIGHTER CONSTRAINTS on Th, U contributions.
It should be used as a default.
UNBINNED ANALYSIS
Th/U = 3.8
DESIDERATUM 1: the KamLAND Collaboration should
provide energy of each event
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
NOTICE THAT
unbinned analysis provides
BETTER CONSTRAINTS either on
Th, U contribution
or
on oscillation parameters
See also:
T. Schwetz, hep-ph/0306226
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
SECOND STEP:
use also TIME INFORMATION.
Geo-ν flux is constant
BUT
total reactor flux follows ~ seasonal variations + possible shut-downs
(info completely known to
KamLAND Collaboration)
additional handle TO SEPARATE
constant Geo-ν
from
variable reactor signal (*)
IF AN UNBINNED
ENERGY-TIME
MAXIMUM LIKELIHOOD
IS USED
(*) See comments in
Ethreshold= 2.6 MeV
E. Lisi, A.M. R. and A. Palazzo et al., hep-ph/0403036
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
DESIDERATUM 2:
for each KamLAND event,
ENERGY + TIME INFORMATION should
be released
&
REACTOR FLUX HISTORY should also be provided
Concerning the future,
the list of desiderata must
certainly include
NEW EXPERIMENTS
in sites with both
LOWER & HIGHER FLUX
- BOREXINO ?
- LENA ?
- Sudbury ?
- Hawaii ?
- Backsan ?
. . . . .
More experiments also needed to average out local uncertainties
in (Th,U) distributions
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
Conclusions
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)
•
KamLAND will start the NEW FIELD of geo-ν observations, and might be followed
by other similar experiments
• LARGE UNCERTAINTIES might hide the underlying (geo)physics for quite some
time, but steady progress can be envisaged, if the particle physics and geo-physics
communities identify COMMON GOALS.
In particular:
An effort can and should be made to characterize the
GEOPHYSICAL and GEOCHEMICAL input in “particle physics
language”: central values, errors and correlations, e.g. on Th/U ratio.
Missing input should be identified and worked out by the two
communities.
The FEW GEO-ν EVENTS which will be COLLECTED BY
KamLAND (and possibly other experiments) in the future deserve
our best analysis tools, so as to squeeze the maximum amount of
information. TIME & ENERGY TAGGING of each individual event
can help the geo-ν/reactor discrimination. Full publicity and full
information for each event and each reactor history is essential to
achieve this goal.
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Anna Maria Rotunno
XXXIXth RENCONTRES
DE
MORIOND
2004 – La Thuile, Aosta Valley, Italy (March 21-28, 2004)