Dr. R. Cerulli talk at SIF 2006, Torino (Italy - people@roma2

Investigazione di sottostrutture
nell'alone galattico mediante la
segnatura della modulazione annuale
R. Cerulli
INFN-LNGS
XCII Congresso Nazionale SIF
Torino, Settembre 2006
Roma2,Roma1,LNGS,IHEP/Beijing
DAMA/LXe
DAMA/R&D
low bckg DAMA/Ge
for sampling meas.
DAMA/NaI
DAMA/LIBRA
http://people.roma2.infn.it/dama
DAMA/NaI(Tl)~100 kg
Performances: N.Cim.A112(1999)545-575, EPJC18(2000)283,
Riv.N.Cim.26 n. 1(2003)1-73, IJMPD13(2004)2127
Results on rare processes:
• Possible Pauli exclusion principle violation
PLB408(1997)439
• CNC processes
PRC60(1999)065501
• Electron stability and non-paulian transitions in
Iodine atoms (by L-shell)
PLB460(1999)235
• Search for solar axions
PLB515(2001)6
• Exotic Matter search
EPJdirect C14(2002)1
• Search for superdense nuclear matter
EPJA23(2005)7
• Search for heavy clusters decays
EPJA24(2005)51
Results on DM particles:
PLB389(1996)757
• PSD
• Investigation on diurnal effect
N.Cim.A112(1999)1541
PRL83(1999)4918
• Exotic Dark Matter search
• Annual Modulation Signature
PLB424(1998)195, PLB450(1999)448, PRD61(1999)023512, PLB480(2000)23,EPJ
data taking completed on July 2002
C18(2000)283, PLB509(2001)197, EPJ C23 (2002)61, PRD66(2002)043503,
Riv.N.Cim.26 n.1 (2003)1-73, IJMPD13(2004)2127, IJMPA21(2006)1445),
(still producing results)
EPJC47(2006)263 + other works in progress....
total exposure collected in 7 annual cycles
107731 kg×d
Relic DM particles from primordial Universe
Light candidates: axion, sterile neutrino, axion-like particles cold or warm DM
(no positive results from direct searches for relic axions with resonant cavity)
Heavy candidates:
•
•
•
•
•
•
In thermal equilibrium in the early stage of Universe
Non relativistic at decoupling time <σann.v> ~ 10-26/ΩWIMPh2 cm3s-1 → σordinary matter ~ σweak
Expected flux:
Φ ~ 107 . (GeV/mW) cm-2 s-1 (0.2<ρhalo<1.7 GeV cm-3)
Form a dissipationless gas trapped in the gravitational field of the Galaxy (v ~10-3c)
stable (or with half life ~ age of Universe)
neutral massive & weakly interacting
self-interacting dark matter
the sneutrino in the Smith
&
and Weiner scenario
SUSY
(R-parity conserved → LSP is stable)
neutralino or sneutrino
a heavy ν of the 4-th family
even a suitable particle not
yet foreseen by theories
mirror dark matter
Kaluza-Klein particles (LKK)
heavy exotic canditates, as
“4th family atoms”, ...
axion-like (light pseudoscalar
and scalar candidate)
etc…
The annual modulation: a model independent signature for the
investigation of Dark Matter particles component in the galactic halo
With the present technology, the annual modulation is the main model independent signature for the DM
signal. Although the modulation effect is expected to be relatively small a suitable large-mass,
low-radioactive set-up with an efficient control of the running conditions would point out its presence.
Drukier, Freese, Spergel PRD86
Freese et al. PRD88
30
June
30
k
~
km 232
/s
m/
km December
/s
60°
s
Requirements of the annual modulation
• vsun ~ 232 km/s (Sun velocity in the halo)
• vorb = 30 km/s (Earth velocity around the Sun)
• γ = π/3
• ω = 2π/T
T = 1 year
• t0 = 2nd June (when v⊕ is maximum)
v⊕(t) = vsun + vorb cosγcos[ω(t-t0)]
S k [η (t )] =
∫
∆Ek
dR
dER ≅ S 0,k +S m ,k cos[ω (t − t0 )]
dER
Expected rate in given energy bin changes
because the annual motion of the Earth around
the Sun moving in the Galaxy
1) Modulated rate according cosine
2) In a definite low energy range
3) With a proper period (1 year)
4) With proper phase (about 2 June)
5) For single hit events in a multi-detector set-up
6) With modulation amplitude in the region of maximal sensitivity
must be <7% for usually adopted halo distributions, but it can
be larger in case of some possible scenarios
To mimic this signature, spurious
effects and side reactions must
not only - obviously - be able to
account for the whole observed
modulation amplitude, but also
to satisfy contemporaneously all
the requirements
Final model independent result by DAMA/NaI
Experimental residual rate of the single hit
events in 2-6 keV over 7 annual cycles
7 annual cycles: total exposure ~ 1.1 x 105 kg×d
Riv. N. Cim. 26 n. 1 (2003) 1-73, IJMPD 13 (2004) 2127
Power spectrum
2-6 keV
experimental residual rate of the multiple hit
events (DAMA/NaI-6 and 7) in the 2-6 keV
energy interval: A = -(3.9±7.9) ·10-4 cpd/kg/keV
2-6 keV
6-14 keV
Acos[ω(t-t0)]
Time (day)
P(A=0) = 7⋅10-4
Solid line: t0 = 152.5 days, T = 1.00 years
from the fit:
A = (0.0192 ± 0.0031) cpd/kg/keV
from the fit with all the parameters free:
A = (0.0200 ± 0.0032) cpd/kg/keV
t0 = (140 ± 22) d
T = (1.00 ± 0.01) y
All the peculiarities of the
signature satisfied
Principal mode
→ 2.737 · 10-3 d-1 ≈ 1 y-1
experimental residual rate of the single hit events
(DAMA/NaI-1 to 7) in the 2-6 keV energy interval:
A = (0.0195±0.0031) cpd/kg/keV
Multiple hits events = Dark Matter particle “switched off”
No systematics or side reaction able to account
for the measured modulation amplitude and to
satisfy all the peculiarities of the signature
model independent evidence of a particle Dark Matter
6.3σ
component in the galactic halo at 6.3
σ C.L.
Summary of the results obtained in the investigations of
possible systematics or side reactions
(see Riv. N. Cim. 26 n. 1 (2003) 1-73, IJMPD13(2004)2127 and references therein)
Source
Main comment
RADON
TEMPERATURE
NOISE
ENERGY SCALE
Sealed Cu box in HP Nitrogen atmosphere,etc
Installation is air conditioned+
detectors in Cu housings directly in contact
with multi-ton shield→ huge heat capacity
+ T continuously recorded
Effective noise rejection
Periodical calibrations + continuous monitoring
of 210Pb peak
Cautious upper
limit (90%C.L.)
<0.2% Smobs
<0.5% Smobs
<1% Smobs
<1% Smobs
Regularly measured by dedicated calibrations
<1% Smobs
No modulation observed above 6 keV + this limit
<0.5% Smobs
includes possible effect of thermal and fast neutrons
+ no modulation observed in the multiple-hits events
in 2-6 keV region
SIDE REACTIONS Muon flux variation measured by MACRO
<0.3% Smobs
EFFICIENCIES
BACKGROUND
+ even if larger they cannot
satisfy all the requirements of
annual modulation signature
Thus, they can not mimic
the observed annual
modulation effect
Summary of the DAMA/NaI Model Independent result
Presence of modulation for 7 annual cycles at ~6.3σ
C.L. with the proper distinctive features of the
signature; all the features satisfied by the data over 7
independent experiments of 1 year each one
Absence of known sources of possible
systematics and side processes able to
quantitatively account for the observed effect
and to contemporaneously satisfy the many
peculiarities of the signature
No other experiment whose result can be directly
compared in model independent way is available so far
To investigate the nature and coupling with ordinary matter of the possible DM candidate(s), effective
energy and time correlation analysis of the events has to be performed within given model frameworks
Corollary quests for candidate(s)
astrophysical models: ρDM, velocity
distribution and its parameters
nuclear and particle Physics models
+
experimental
parameters
e.g. for WIMP class particles: SI, SD, mixed SI&SD,
preferred inelastic, scaling laws on cross sections, form
factors and related parameters, spin factors, halo models,
etc.
+ different scenarios
+ multi-component?
THUS
uncertainties on models
and comparisons
Few examples of corollary quests for
the WIMP class in given scenarios
(Riv. N.Cim. vol.26 n.1. (2003) 1-73, IJMPD13(2004)2127)
DM particle with elastic SI&SD interactions
(Na and I are fully sensitive to SD interaction, on the
contrary of e.g. Ge and Si) Examples of slices of the
allowed volume in the space (ξσSI, ξσSD, mW, θ) for
some of the possible θ (tgθ =an/ap with 0≤θ<π) and mW
DM particle with dominant SI coupling
Region of interest for a neutralino in
supersymmetric schemes where
assumption on gaugino-mass
unification at GUT is released and for
“generic” DM particle
not exhaustive
+ different
scenarios?
Most of these allowed volumes/regions
are unexplorable e.g. by Ge, Si,TeO2, Ar,
Xe, CaWO4 targets
Model dependent lower
bound on neutralino mass
as derived from LEP data
in supersymmetric
schemes based on GUT
assumptions (DPP2003)
higher mass region
allowed for low v0,
every set of
parameters’ values
and the halo
models: Evans’
logarithmic C1 and
C2 co-rotating,
triaxial D2 and D4
non-rotating, Evans
power-law B3 in
setA
DM particle with dominant SD coupling
volume allowed in
the space (mW,
ξσSD,θ); here
example of a slice
for θ=π/4 (0≤θ<π)
DM particle with preferred
inelastic interaction:
W + N → W* + N (Sm/S0
enhanced): examples of slices of
the allowed volume in the space
(ξσp, mW,δ) [e.g. Ge disfavoured]
Regions above 200
GeV allowed for low
v0, for every set of
parameters’ values
and for Evans’
logarithmic C2 corotating halo models
Some open scenarios on astrophysical aspects
In the galactic halo, fluxes of Dark
Matter particles with dispersion
velocity relatively low are expected:
some relics of the hierarchical assembly of
the Milky Way are already observed in the
visible: Sagittarius dwarf galaxy since 1994,
Canis Major galaxy early discovered…
This scenario foreseen streams of Dark Matter particles with low
velocity dispersion, very interesting for direct detection: Sm/S0
enhanced in A.M., new signature for streams
La galassia “nana” Sagittario (Sgr) e l’alone di materia oscura…
Nel 1994 –1995 e’ stato osservato un
nuovo oggetto “Sagittarius Dwarf
Elliptical Galaxy” nelle vicinanze della
Via Lattea, nella direzione del centro
galattico, ed in posizione opposta ad esso
rispetto al Sistema Solare
La direzione di moto della Sgr era molto diversa da quella degli altri oggetti luminosi
nella Via Lattea, così si è scoperto che le stelle osservate appartenevano ad una galassia
nana satellite della Via Lattea, che sta per essere catturata. La galassia nana ha assunto
una forma molto allungata a causa delle forze di marea subite durante le circa 10
rivoluzioni effettuate attorno alla Via Lattea.
Ipotesidi formazione delle code della Sgr
Simulazione della deformazione della galassia
Sgr causata dalle forze di marea durante le sue
rivoluzioni attorno alla Via Lattea
La Sgr era, originariamente, una galassia
satellite di forma ellissoidale, simile alla
LMC e SMC. A causa della relativa
vicinanza con la Via Lattea, le stelle piu’
esterne sperimentano una attrazione
gravitazionale relativamente minore da
quelle piu’ interne; le prime ruotano,
attorno alla Via Lattea, piu’ lentamente
rispetto al centro della Sgr e quindi si
trovano in ritardo e formano la cosiddetta
coda trascinata “trailing tail”. Le
seconde, ruotando con maggiore velocità,
si trovano in anticipo e formano la coda
trainante “leading tail”.
La galassia sferoidale “nana” Sagittario, satellite della Via Lattea
(Ibata et al. 1994)
E’ atteso un flusso di particelle
costituenti la materia oscura
dell’alone galattico di Sgr, con
velocità ortogonale al nostro
piano galattico di circa 300 km/s.
il Sole disterebbe
pochi kpc dal
centro della coda
trainante...:
da astro-ph/0309279:
Densità dello stream attesa:
[1 -- 80] 10-3 GeV/cm3 (0.3-25)% di ρhalo
Velocità locale media dello stream ricavata dalle
misure su 8 stelle locali attribuite alla coda
trainante di Sgr:
sgr
(290±26) km/s nella direzione (l,b)=(116,-59):
(Vx,Vy,Vz)=(-65±22, 135±12,-249±6)km/s
Dispersione delle velocità:
(σvx,σvy,σvz)=(63,33,17)km/s
sun
stream
Altri stream di materia oscura da
galassie satelliti della Via Lattea
vicini al Sole?
.....molto probabile....
Posizione del Sole:
(-8,0,0)kpc
E’ ipotizzato che le galassie a
spirale come la Via Lattea si
formano per cattura delle vicine
galassie satelliti come la Sgr,
Canis Major ecc…
Canis Major simulation:
Astro-ph/0311010 Ibata et
al.
Investigating halo substructures by underground expt
through annual modulation
Possible contributions due to the tidal stream of
Sagittarius Dwarf satellite (SagDEG) galaxy of Milky Way
spherical
EPJC47(2006)263
oblate
sun
stream
Examples of the effect
of SagDEG tail on the
phase of the signal
annual modulation
V8*
Vsph V
obl
Expected phase in the absence of
streams t0 = 152.5 d (June 2nd)
mW=70 GeV
160
140
NFW spherical isotropic non-rotating,
v0 = 220km/s, ρ0max + 4% SagDEG
NFW spherical isotropic non-rotating,
v0 = 220km/s, ρ0min+ 4% SagDEG
V8* from 8 local stars: PRD71(2005)043516
180
t0 (day)
simulations from Ap.J.619(2005)807
Ex. NaI:
3 105 kg d
120
5
E (keVee)
DAMA/NaI results:
(2-6) keV t0 = (140±22) d
10
Investigating the effect of SagDEG contribution for WIMPs
EPJC47(2006)263
DAMA/NaI: seven annual cycles 107731 kg d
for different SagDEG velocity dispersions (20-40-60 km/s)
ρSagDEG < 0.1 GeV
cm-3
(bound by M/L ratio considerations)
mixed SI&SD case
green area:
no SagDEG
pure SD case
pure SI case
Constraining the SagDEG stream by DAMA/NaI - 1
EPJC47(2006)263
•
The high exposure of DAMA/NaI allows to obtain information about the presence of substructures in the halo as the
SagDEG stream.
•
Statistical analysis approach: likelihood ratio function to investigate the SagDEG parameters
value of the likelihood
function maximized
with respect to the σ
asymptotically
distributed as χ2 (dof=1)
by fixing:
i) a SagDEG velocity set and a velocity dispersion (index is);
ii) the WIMP mass (labeled mW) and θ;
iii) the galactic halo model and all the other parameters involved in the calculation (index im),
Example of the results of this analysis
3 representative cases
a model where the SagDEG contribution worsens the data fit;
a model where the SagDEG contribution
improves the data fit providing a C.L. lower than 3σ
a model where the SagDEG contribution improves the data fit
providing a C.L. better than 3σ
Constraining the SagDEG stream by DAMA/NaI - 2
for different SagDEG velocity dispersions (20-40-60 km/s)
EPJC47(2006)263
pure SI case
pure SD case
This analysis shows the possibility to investigate local halo features by annual modulation
signature already at the level of sensitivity provided by DAMA/NaI, allowing to reach
sensitivity to SagDEG density comparable with M/L evaluations.
The higher sensitivity of DAMA/LIBRA will allow to more effectively investigate the
presence and the contributions of streams in the galactic halo
Constraining the SagDEG stream by DAMA/NaI - 3
EPJC47(2006)263
Studying the ρsgr best-fit values achieved for the various considered models
Cumulative percentage
distribution of ρsgr best-fit
values providing a C.L. better
than 2σ with the respect to
the absence of SagDEG.
Example: pure SI
candidate and fixed
SagDEG stream with
velocity set Vsph and
velocity dispersion
v0,sgr=40 km/s.
• About 60% of these models gives ρsgr best-fit values below 0.1 GeV/cm3;
• The distribution peaks around ρsgr
0.04 GeV/cm3
• These latter values are intriguing, considering the expectations on the stream density at sun
position – that is few % of the local dark halo – based on some theoretical studies about the
disruption of the satellite galaxies falling in the Milky Way halo (see PRD64(2001)083516).
Summary
DAMA/NaI data show a 6.3σ C.L. model independent evidence for the
presence of a Dark Matter particle component in the galactic halo
Corollary model dependent quest for the candidate particle:
• WIMP particles with mw~ (few GeV to TeV) with coupling pure SI or
pure SD or mixed SI/SD as well as particles with preferred inelastic
scattering
(Riv.N.Cim. 26 n.1. (2003) 1-73, IJMPD 13 (2004) 2127)
• several other particles suggested in literature by various authors
(see literature)
• bosonic particles with ma~ keV having pseudoscalar, scalar coupling
• halo substructures (SagDEG) effects
• and more in progress...
(IJMPA21(2006)1445)
(EPJC 47 (2006) 263)
The presently running DAMA/LIBRA will allow to further increase the
C.L. of the model independent result, to restrict the nature of the
candidate and to investigate the phase space structure of the dark halo
+ a new R&D towards a possible ton set-up we proposed in 1996 in progress
... wait for more in the near future