1Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
Based on work done in collaboration with: E. Lisi, A. Marrone, A. Melchiorri, A. Palazzo, P. Serra, J. Silk, A. Slosar
Gianluigi Fogli
Dipartimento di Fisica dell’Università di Bari & Sezione INFN - Bari
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Venice, April 15, 2008
What we (would like to) know about the neutrino mass
Gianluigi Fogli
NO-VE 2008, IV International Workshop on “Neutrino Oscillations in Venice”
2Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
Outline
1. Updating neutrino oscillation parameters
2. Updating non-oscillation observables
3. Interplay of oscillation/non-oscillation bounds
4. Constraining (some) 02 theoretical
uncertainties
5. Conclusions
3Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
1. Updating neutrino oscillation parameters
GLF, Lisi, Marrone, Melchiorri, Palazzo, Serra, Silk, SlosarAddendum to arXiv:hep-ph/0608060 (in preparation)
GLF, Lisi, Palazzo, RotunnoGeo- analysis (in preparation)
Based on:
4Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
data provide a better determination of the two independent neutrino oscillation frequencies:
oscillations driven bym2 ~ 2.4 x 10-3 eV2
oscillations driven bym2 ~ 7.6 x 10-5 eV2
(Recent solar neutrino results from Borexino 2007 and SK-phase II 2008 do not affect yet the global analysis of neutrino mass/mixing parameters)
MINOS 2007 (preliminary) and KamLAND 2008
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2008
Visible progress from 2006 (dashed) to 2008 (solid)
“Solar” neutrinos
“Atmospheric” neutrinos
6Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
(Addendum to hep-ph/0608060, in preparation)
2008 parameter summary at 2 level (95 % CL)
This is what we know.
7Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
Concerning
Some aspect is currently “hidden” below 1 C.L.
What we would like to know
Hierarchy (normal or inverted)CP in the sector13 mixing
A recent example:
slight preference for
from the combination of solar+reactor 2008 data
(green curve in the figure)
sin213 ~ 0.01
8Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
[figure taken from the official Kamland site (2008)]
• Solar data (SNO dominated)
• KamLAND data (at 13 = 0)
when the two best-fits are compared in the usual plane (m2
12, tan212)
Slight disagreement between
Reason:
9Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
sin213 = 0 sin213 = 0.03
(figures prepared by A.M. Rotunno for this talk)
… thanks to the different dependence in SNO and KamLAND from (13 , 12).
Disagreement reduced for 13 > 0 …
10Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
Let’s now switch to the
but with some potential for improvement, once final SNO data and further KamLAND data will be available.
A tiny effect, of course,
11Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
2. Updating non-oscillation observables
12Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
Three absolute mass observables: m,
m, that depend on the parameters measured in oscillations:
1) decay
a very good approximation, valid if energy smearing prevents observation of separate “Kurie plot kinks”
2) 02 decay
expression basically exact (as far as no RH currents or new physics interfere with light neutrino exchange)
3) Cosmology
leading sensitivity related to the sum of the masses; in the (far) future, maybe some weak sensitivity to mass spectrum hierarchy
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2008
1) decay: None (waiting for KATRIN)
2) 02 decay: Final results from Klapdor et al. (2006); Revised nuclear matrix elements and uncertainties (2007);
Cuoricino results (2008)
3) Cosmology: WMAP 5 year data (2008)
Some updates in the last 1-2 years
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2008
Bounds on for increasingly rich data sets (assuming flat CDM model):
Limits depend on the input data sets:• CMB (WMAP3y + others)
• Sloan Digital Sky Survey (SDSS)
• Type Ia Supernovae (SN)
• Big Bang Nucleosynthesis (BBN)
• Large Scale Structure (LSS)
• Hubble Space Telescope (HST)
• Baryon Acoustic Oscillations
(BAO)
• Lyman-(Ly-)
Power Spectrum of density fluctuations
fν =ν
m
in terms of
Cosmology (one year ago)
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2008
Case 1: most “conservative” (only 1 data set: WMAP 3y)
Case 7: most “aggressive” (all available cosmological data)
Upper limits range from ~2 to ~0.2 eV at 95% C.L., but no consensus on a specific value yet
Constraints from Cosmology
(eV)
stan
dard
devia
tions
Constraints on from Cosmology (one year ago)
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2008
(Addendum to arXiv:hep-ph/0608060, in preparation)
preliminary
Unfortunately the global analysis is not ready: work is in progress.
< 1.3 eV at 2
We can only present the preliminary results coming from CMB data alone after WMAP 5y
Of course, we expect the limit strengthened in the sub-eV range by LSS + other data
Cosmology today
[Always adopting the usual caveats about the CDM model, its matter-energy content, and the way in which the other data sets are included.]
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2008
evidence …
no evidence?
02 decay update
or
A true dilemma …
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Klapdor et al.: MPLA 21, 1547 (2006)
Cuoricino, arXiv:0802.3439 [hep-ex]
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2008
(Addendum to arXiv:hep-ph/0608060, in preparation)
• Claim of 02 decay in 76Ge controversial, but:• Sensitivity to signal, in principle, is no longer disputed.• Final results by Klapdor et al.: MPLA 21, 1547 (2006).
lower and more conservative than it was adopted ~2 years ago
In combination with recent nuclear matrix elements and uncertainties from Simkovic et al., arXiv:0710.2055 [nucl-th], these results would provide the 2 preferred range:
02 decay - evidence
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2008
• Cuoricino has found no 02 decay signal in 130Te. • Recent results in arXiv:0802.3439 [hep-ex].• Half life in 1024 years: T > 3.1 (90% CL); T > 2.5 (95% CL)
In combination with recent nuclear matrix elements and uncertainties from Simkovic et al., arXiv:0710.2055 [nucl-th], these results would provide the 2 upper limits:
where the spread (…) is due to theoretical uncertainties.
02 decay - no evidence
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2008
• the preferred 2 range by Klapdor et al. m[0.16, 0.52] eV
• the 2 upper limits by Cuoricino m[0.23,
0.85] eV
we see that Cuoricino is starting to probe the 76Ge 02 claim, but current theory errors (in different isotopes) prevent definite statements.
So, concerning
What we would like to know
the Dirac or Majorananature of neutrinos
It is still hidden in the data, with further uncertainties arising from the theory of nuclear structure. [More about the attempt of error reduction later].
Let’s now switch to the
Comparing
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2008
3. Interplay of oscillation/non-oscillation bounds
GLF, Lisi, Marrone, Melchiorri, Palazzo, Serra, Silk, SlosarAddendum to arXiv:hep-ph/0608060 (in preparation)
Based on:
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2008
m
oscill.
allo
wed
i.e., if one observable increases, the other one (typically) must increase to match the mass2 splitting.
Oscillations fix the mass2 splittings, and thus induce positive correlations between any pair of the three observables (m, m, ), e.g.:
Interplay/1
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2008
m
oscill.
allo
wed
In the absence of new physics (beyond 3 masses and mixing), determinations of any two observables among (m, m, ) are expected to cross the oscillation band
This requirement provides either an important consistency check or, if not realized, an indication for new physics (barring expt. mistakes)
m
Interplay/2
Analysis of established oscillation data is an important ingredient
24Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
Bands from 2008 osc. data for normal and inverted hierarchy
Invert
ed
Deg
en
era
te (
overl
ap
)N
orm
al
Bands overlap when mass splittings are small with respect to the absolute masses:
Majoranaphase(s)spread
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2008
Check the overall consistency between oscill./nonoscill. data …
Identify the hierarchy …(inverted, in this case)
Probe the Majorana phase(s) …(i.e., reduce vertical spread in m)
e.g., if…
Intermezzo: Dreaming about future precise data below 0.1 eV…
Data = green “dot” in the figure, then …
in principle, one might, with some luck:
26Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
Relevant example including previous 2008 updates:
Constraints from
They admit a global combination at 2
(thick black wedge in the figure)
oscillations + WMAP 5y + 02 claim
… back to real life
But no combination if
from cosmology (WMAP + other data)
< 0.45 eV
27Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
Each (degenerate) neutrino mass should be found in the 2 range:
m1 m2 m3 0.15 - 0.80 eV
This range is largely accessible to the KATRIN expt. (except below ~0.2 eV). Possible outcomes within the reach of Katrin might be, e.g., (1 errors):
Assuming the previous combination
m = 0 0.12 (< 0.2 at 90% CL)
m = 0.30 0.10 (3 evidence)
m = 0.35 0.07 (5 discovery)
KATRIN discovery potential
Let’s now switch to the
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2008
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4. Constraining (some) 02 theoretical uncertainties
Based on:
Faessler, GLF, Lisi, Rodin, Rotunno, SimkovicarXiv:0711.3996 [nucl-th]
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In principle, any nuclear model used to calculate the 02 NME for a given nucleus, should also be able to describe all the other (allowed) weak-interaction processes for that nucleus:
*Quasiparticle Random Phase Approximation
22 decay, decay, EC, C, and charge-exchange reaction.
The available weak-interactions data could then be used to benchmark the nuclear model parameter space and reduce NME uncertainties.
For example, QRPA* calculations involve a particle-particle interaction strength
gpp ~ O(1)
In principle, a single datum can be used to fix gpp (value error).
Benchmarking Nuclear Matrix Elements (NME)
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BUT: Data of different quality and not always in agreement with each other.
A lot of measurements available: ourCompilation
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To safest data set: lifetimes of 22 decay decay EC
to the only three nuclei for which all these data are available
100Mo 116Cd 128Te
We restrict ourselves
Note: Unfortunately this choice excludes, at the moment, 76Ge and 130Te, used in the two experiments discussed before.
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2008
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Debate between the two groups about which approach is better
Rodin, Faessler, Simkovic & Vogel:use 22 decay data to fix gpp
Civitarese & Suhonen:use decay (or EC) to fix gpp
[In any case, such experimental constraints cannot reduce those theoretical systematics which are peculiar of 02 decay, such as the so-called “short-range correlation” (SRC) effects]
Two conflicting approaches so far
Both approaches, however, face a severe problem:
Difficult to fit both 22 and decay (EC) data within the same gpp range
33Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
We suggest that this discrepancy may be related to unnecessarily restrictive choices for the effective axial coupling (gA) in nuclear matter.
Experimentally, the observed Gamow-Teller strength (~ gA2) in nuclei
is weaker than in vacuum:
gA < 1.25 “quenching”
Usually, quenching is implemented by taking gA ≈ 1 “standard quenching”
BUT:
Amount and origin of quenching in different nuclei is still debated.
Usual practice (gA ≈ 1) should not be considered as a “dogma”, and
data-driven departures may well be possible. In our case:
gA = 0.84 “strong quenching”
Our approach: Strong Quenching
34Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
E.g., 116Cd with gA = 1
QRPA estimates 1
EXPT data 1
Preferred gpp range
22
EC
-
Disjoint gpp ranges
[Twofold ambiguity for 22 and -]
Problem worse for gA = 1.25 (“bare”)
Q.: Can gA<1 help?
“standard” quenching
Yes.
35Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
22
EC
-
Common gpp range, 0.4-0.6
[Ambiguity solved]
gA = 0.84 not much lower than gA = 1
E.g., 116Cd with gA = 0.84
“stronger” quenching
QRPA estimates 1
EXPT data 1
Preferred gpp range
If we accept gA < 1, then …
36Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
Search for the regions allowed in the plane (gpp, gA)
116Cd
100Mo 128Te
This provides a possible way to reduce the uncertainties in the
parameters (gpp, gA), which also affect the 02 NME (Nuclear Matrix
Elements)
The panels show, for each nucleus, the 1 bands for the three
processes (22, EC and –) and the corresponding best fit
37Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
Apparently not very different, but big gain in understanding and controlling errors.
Implications for the 02 Nuclear Matrix ElementsWe compare …
Our results (theory in agreementwith 22, -, and EC data)
Previous results (gA=1 fixed, theory in agreement only with 22 data)
38Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
Some further remarks on 02 NME
The unconventional hypothesis gA < 1 must certainly pass further tests.Anyway, we hope that our approach may spark new interest towards a larger research program to benchmark the 02 nuclear models in more nuclei and with more data.
This is mandatory to reduce 02 theoretical uncertainties and make the best use of experimental results in terms of m.
Let’s now switch to the
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2008
5. Conclusions
40Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
… concerning what
We would like to know …
… we need to be patient, in particular to access absolute neutrino masses…
already a lot about neutrinos, mainly because of the extremely rapid progress in oscillation searches during the last decade 1998-2008 …
…
We know …
but …
Going back to the title …
41Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
“Moore’s law”
: factor of ~10 improvement every ~15 years
2000
2015
2000
2015
2030
2015 2000
?
?
KATRIN, MARE ?
CUORICINO,GERDA …
WMAP
42Gianluigi Fogli IV International Workshop on “Neutrino Oscillations in Venice”, Venice, April 15,
2008
See you there!
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
… but, on a much shorter timescale, let me invite all of you at
NOW 2008, Conca Specchiulla, Sept. 6-13 (www.ba.infn.it/~now2008)
Indeed, an impressive lot of time …