La Materia Oscura
dell’Universo e i risultati
dell’esperimento DAMA
R. Cerulli
INFN-LNGS
Gennaio 2007
Evidenze sperimentali sull’esistenza
della Materia Oscura
9Prima evidenza sperimentale dell’esistenza di Materia
Oscura nell’Universo: misure delle velocità delle galassie che
compongono l’ammasso COMA eseguite da Zwicky nel 1933.
Queste osservazioni mostrarono che la sola componente visibile di
materia non poteva dare conto delle velocità misurate e che la materia
non luminosa era presente nell’ammasso in percentuale nettamente
superiore rispetto alla materia visibile.
9Pochi anni più tardi nel 1936 Smith confermò l’esistenza di Materia
Oscura studiando l’ammasso di galassie della Vergine.
9Uno studio sistematico che accredita l’esistenza di Materia Oscura anche a livello di singole
galassie è stato eseguito nel 1974 da due diversi gruppi, considerando molte galassie a spirale.
Vediamo qui in particolare come è stato possibile evidenziare
la presenza di Materia Oscura nelle galassie a spirale:
velocità di rotazione degli oggetti astrofisici di una galassia a spirale ad una
distanza R dal centro della galassia.
• Nel caso di sola materia luminosa, gli oggetti molto distanti dal centro della
galassia, al di fuori del disco luminoso, dovrebbero avere una velocità che
decresce all’aumentare di R (~1/√R).
• Le misure sperimentali mostrano, invece, che tali oggetti hanno velocità quasi
costante per grandi valori di R. Tale risultato indica che deve esistere un’altra
componente di materia, non visibile, detta alone oscuro.
In particular, spherical symmetry; mass inside a sphere:
M (r ) = ∫ ρdV
V
GM (r )m
v2
=m ;
r2
r
⇒
v2 =
• Solar system or solar-system-like:
v∝
• Galaxy: v about flat:
⇒
In fact:
M (r ) ∝ r ;
r02
ρ (r ) = ρ 0 2 ;
r
⇒
GM (r )
r
1
r
ρ∝
M (r ) = 4π ∫
r
0
1
r2
r02 2
ρ 0 2 r ' dr ' = 4πρ0 r02 r
r'
G 4πρ0 r02 r
GM (r )
v=
=
= 4πGρ 0 r02 = const.
r
r
4
V = πr 3
3
Altre evidenze sull’esistenza della
Materia Oscura
9 Studio del moto della Grande Nube di Magellano
intorno all nostra Galassia
9 Studio dei raggi-X emessi dai gas che circondano le
galassie ellittiche
9 Studio della distribuzione della velocità del plasma
caldo intergalattico negli ammassi
COMA Cluster
Anche la nostra Galassia (la Via Lattea)
contiene al suo interno un alone oscuro che la
pervade
La Via Lattea
Una recente prova dell’esistenza di
Materia Oscura D. Clowe et al., astro-ph/0608407
Collisione di due
ammassi di galassie
(1E0657-558 a
z=0.296) avvenuta
circa 100Myr fa
9 Nella collisione tra due ammassi le galassie si comportano come un gas di particelle non interagenti mentre
le nubi di plasma all’interno dell’ammasso - che si comportano come un fluido ed emettono raggi X – sono
fortemente interagenti e sono sottoposte alla “pressione di ariete”
9 Dopo la collisione le galassie precedono il plasma rallentato dalla “pressione di ariete” e le due componenti
si trovano in due regioni ben separate
9 Il profilo del potenziale gravitazionale ottenuto
studiando il lensing gravitazionale (contorno verde) è in
accordo con la distribuzione spaziale delle galassie e
non con la distribuzione del plasma
9 Questo si spiega ammettendo che la maggior parte
della materia presente nel sistema è non luminosa
9 Teorie della gravità modificata non sono in grado di dar
conto delle osservazioni
Indicazioni dalla presenza di Materia
Oscura dalla cosmologia
Le fondamenta del modello del Big Bang
9 La scoperta dell’espansione
dell’Universo – E. Hubble (1929)
L’espansione dell’Universo
9Nel 1917 si pensava che l’Universo fosse statico e consistesse
nella nostra Galassia e lo spazio vuoto che la circondava.
Galassia M31- Andromeda
9Negli anni venti, E. Hubble usando il nuovo telescopio da 2.5 m
sul monte Wilson riuscì a misurare:
La Via Lattea
; la distanza di alcune nebulose
dimostrando che erano galassie esterne
; le loro velocità di recessione
Le galassie si allontanano con una velocità
di recessione proporzionale alla distanza
Espansione generale dello spazio-tempo:
H0=500 km/s/Mpc
v = H 0d
H0=71 km/s/Mpc
Le galassie non si allontanano nello spazio ma è lo
spazio stesso che si espande, trascinando con sè
le galassie
Le dimensioni fisiche delle galassie non
cambiano→la gravità le “isola” dall’espansione
Effetto osservabile su scala
intergalattica: la stella più vicina al Sole
(Proxima Centauri), 4.22 anni-luce, si
allontana da noi per il solo effetto
dell’espansione con una velocità di
soltanto 10 cm/s !!
Espansione priva di un centro:
Un osservatore da una qualsiasi
galassia vede la stessa espansione →
l’unica legge di espansione compatibile
con il Principio Cosmologico
Le fondamenta del modello del Big Bang
9 La scoperta dell’espansione
dell’Universo – E. Hubble (1929)
9 Le abbondanze degli elementi
leggeri: H, He, Li – G. Gamow (1948)
Le abbondanze degli elementi (i primi 3 minuti)
Bariogenesi
QUARKS
1 secondo
Barioni
protoni, neutroni
Leptoni
elettroni, neutrini
non avverrà MAI PIU’
nella storia dell’Universo
Interazioni meno
frequenti
100 secondi
1 neutrone ogni
7 protoni,
fotoni
7
Formazione dei nuclei
atomici
H, He
Gamow:
La radiazione del Big Bang sopravvive
ma a causa dell’espansione si
raffredda
1
Previsione di Gamow:
Radiazione “fossile” = 5 K Æ -268 °C
due neutroni formano 1 nucleo di He
25% He
75% H
Le fondamenta del modello del Big Bang
9 La scoperta dell’espansione
dell’Universo – E. Hubble (1929)
9 Le abbondanze degli elementi
leggeri: H, He, Li – G. Gamow (1948)
9 La scoperta della radiazione di fondo
cosmico (CMB) – Penzias e Wilson (1965)
Radiazione Fossile del Big Bang
Viene scoperta da Penzias e Wilson (1965)
Temperatura della radiazione misurata: 3 K
(banda delle micro-onde)
Riempie uniformemente
il cielo!
nessuna sorgente
astrofisica sarebbe in
grado di produrre una
radiazione così uniforme!
L’immagine più antica dell’Universo
380’000 anni dopo il Big Bang la radiazione
si “libera” dalla materia ed inizia a propagarsi
Spettro della Radiazione
La radiazione fossile mantiene “memoria”
dello stato dell’Universo quando aveva lo
0.003% della sua età attuale
... e il lato oscuro dell’Universo?
Il miglioramento delle tecniche sperimentali ha
permesso di ottenere informazioni anche sul
lato oscuro dell’Universo
La radiazione cosmica di fondo ha permesso di
studiare il valore della densità totale dell’Universo
(Ω= ρ/ρ0) e i diversi contributi ad essa.
SN 1987A vista dal telescopio Hubble
La verifica della legge di Hubble su scala sempre più
grande permette di avere informazioni sull’espansione
accelerata → costante cosmologica ed energia oscura
La nucleosintesi primordiale ha permesso di
studiare quanti barioni ci sono oggi
nell’Universo → necessità di materia oscura
Fluttuazione nella radiazione fossile: gli embrioni delle galassie
(T2-T1)/T1=3×10-5
Immagine a tutto cielo
dell’Universo 380000 anni
dopo il Big Bang.
Le fluttuazioni di temperatura sono la traccia di
fluttuazioni di densità della materia: gli embrioni
delle galassie che cresceranno attraverso
l’amplificazione gravitazionale
Nel 1992, COBE rivelò per primo piccole fluttuazioni di
temperatura (indicate da variazioni di colore)
WMAP
WMAP nel 2003 ha messo a fuoco
l’immagine data da COBE
WMAP
Se Ω =1, è prevista la presenza
di un picco a l ∼ 200
Composizione dell’Universo (barioni)
Parametro di densità:
Ω = densità/densità critica
6 atomi di H/m3
La teoria cosmologica del Big Bang prevede,
negli scenari teorici più accreditati, Ω=1.
Verifica dalle misure sulla anisotropia di CMB
Ω = 1
Barioni (cioè protoni, nuclei e atomi):
Considerando:
a) la presente abbondanza di nuclei leggeri
b) la densità dei fotoni CMB
ΩB = 4%
E’ necessaria Materia Oscura Non Barionica:
- particelle relitte dall’Universo primordiale
- relativistiche (Hot DM) o non-relativistiche (Cold DM)
al tempo del disaccoppiamento
- Hot DM: neutrinos
- Cold DM: WIMPs, axions, axion-like, ...
Composizione dell’Universo (energia oscura)
Negli ultimi 10 anni, studio della legge di Hubble su scala
sempre più grande, attraverso l’utilizzo di “candele
standard”: supernovae Ia (SN Ia).
informazioni sull’espansione accelerata
→ costante cosmologica ed energia oscura
energia del vuoto caratterizzata
da una pressione negativa
Ω Λ ≈ 0.73;
Universo dominato da Λ
Ω M ≈ 0.27
Contributo della materia
(oscura e non)
Universo dominato dalla materia oscura
“Concordance model”
Ω = ΩΛ + ΩM =
1.02±0.02
Ω = densità/densità critica
6 atomi di H/m3
Supernovae IA
ΩΛ ≈ 0.73
ΩM ≈ 0.27
The Universe is flat
WMAP
Primordial
Nucleosynthesis
The baryons give “too small”
contribution
Observations on:
• light nuclei abundance
• microlensings
Structure formation
• visible light.
in the Universe
Ωbb∼∼4%
4%
Ω
ΩCDM
23%,
Ω
CDM∼∼23%,
Non baryonic Cold Dark
%
ΩHDM,ν
HDM,ν<<11%
Ω
Matter is dominant
∼ 90% of the matter in the Universe is non baryonic
A large part of the Universe is in form of non baryonic Cold Dark Matter particles
Relic CDM particles from primordial Universe
Light candidates:
axion, axion-like produced at rest
(no positive results from direct searches for relic axions with resonant cavity)
axion-like (light pseudoscalar
and scalar candidates)
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)
neutral
stable (or with half life ~ age of Universe)
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
mirror dark matter
Kaluza-Klein particles (LKK)
heavy exotic canditates, as
“4th family atoms”, ...
even a suitable particle not
yet foreseen by theories
µ
Indirect detection
DM particles may accumulate in Sun/Earth, in
galactic halo
↓
annihilate
↓
high energy neutrinos, g’s, anti-p and e+
↓
Search for an excess over the (largely
unknown) background
antimatter
signature
• Search for
antimatter excess in
cosmic rays
• Space detectors
γ signature
• Search for quasimonoenergetic γ’s in
cosmic rays
• Space detectors
EARTH
detector
DMp
DMp
νµ
DMp
DMp
DMp
DMpantiDMp
SUN
νµ signature
• Best signature from νµ
producing up-ward going µ
• Underground, underwater,
underice detectors
Similar searches can offer only results, which strongly
depend on the background modeling and on the
astrophysical, particle and nuclear Physics assumptions
La rivelazione diretta delle particelle di
Materia Oscura
Diffusione su nuclei-bersaglio
• Questa tecnica si basa (principalmente) sullo studio
dell’interazione elastica delle particelle di DM con i nuclei che
costituiscono il rivelatore utilizzato.
DMp
DMp
Nucleo
• A seguito di una interazione elastica di una particella con un
nucleo, questo rincula.
Energia di
rinculo
• L’energia di rinculo del nucleo è, quindi, la grandezza
misurata.
• Si possono utilizzare rivelatori a scintillazione (NaI(Tl), LXe,
CaF2(Eu),etc.), a ionizzazione (Ge, Si), Bolometri (TeO2, Ge)
Conversione in radiazione elettromagnetica
• A seguito della conversione della particella
nell’interazione con il nucleo, vengono prodotti
γ, raggi-X o e- con energia circa uguale alla
sua massa
Diffusione elastica sul nucleo con eccitazione
di elettroni legati
• Si misura l’energia di rinculo del nucleo e
la radiazione e.m. prodotta
a
X-ray
γ
eNOTA: i segnali prodotti da questi
candidati sono perduti in esperimenti
basati sulle procedure di reiezione del
fondo elettromagnetico
Main recipes for the Dark Matter particle direct detection
• Underground site
• Low bckg hard shields
against γ’s, neutrons
Reduction
from the
underground
site
• Lowering bckg: selection of
materials, purifications,
growing techniques, ...
• Rn removal systems
Background sources
- Background at LNGS:
muons
→
neutrons
→
Radon in the hall →
0.6 µ/(m2h)
1.08·10-6 n/(cm2s) thermal
1.98·10-6 n/(cm2s) epithermal
0.09·10-6 n/(cm2s) fast (>2.5 MeV)
≈30 Bq/m3
Example of
background
reduction
during many
years of work
- Internal Background:
selected materials (Ge, NaI, AAS, MS, ...)
Shielding
Example of
the effect of a
passive shield
Passive shield: Lead (Boliden [< 30 Bq/kg from 210Pb], LC2
[<0.3 Bq/kg from 210Pb], lead from old roman galena), OFHC
Copper, Neutron shield (low A materials, n-absorber foils)
Active shield: Low radio-activity NaI(Tl) surrounding the
detectors
The “traditional” approach
several assumptions
and modeling required Exclusion plot
σnucleus
• Experimental vs Expected spectra (with or without bckg rejection )
Excluded at
given C.L.
+
experimental and
theoretical
uncertainties generally
not included in
calculations
MW
by model: σp
An exclusion plot not an absolute
limit. When different target nuclei,
no absolute comparison possible.
• No discovery potentiality
• Uncertainties in the exclusion plots and in their comparison
• Warning: limitations in the recoil/background discrimination (always not event
by event): PSD (τ of the pulse depends on the particle) in scintillators
(NaI(Tl), LXe), Heat/Ionization (Ge), Heat/Scintillation (CaF2(Eu), CaWO4).
To have a potentiality of discovery a
model independent signature is needed !
A model independent signature is needed
Directionality Correlation of
nuclear recoil track with
Earth's galactic motion due to
the distribution of Dark
Matter particles velocities
very hard to realize
Nuclear-inelastic scattering
Detection of γ’s emitted by
excited nucleus after a nuclearinelastic scattering.
very large exposure and very low
counting rates hard to realize
Diurnal modulation Daily variation of
the interaction rate due to different
Earth depth crossed by the Dark Annual modulation Annual variation
Matter particles
of the interaction rate due to Earth
only for high σ
motion around the Sun.
at present the only feasible one
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, lowradioactive set-up with an efficient control of the running conditions would point out its presence.
Drukier, Freese, Spergel PRD86
Freese et al. PRD88
30
~
km 232
/s
June
30
k
m/
km December
/s
• 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)]
60°
s
Requirements of the annual modulation
S k [η (t )] =
∫
∆E k
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
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/LXe: results on rare processes
NIMA482(2002)728
Dark Matter Investigation
• Limits on recoils investigating the DMp-129Xe
elastic scattering by means of PSD
PLB436(1998)379
PLB387(1996)222, NJP2(2000)15.1
• Limits on DMp-129Xe inelastic scattering
PLB436(1998)379, EPJdirectC11(2001)1
• Neutron calibration
• 129Xe vs 136Xe by using PSD → SD vs SI signals to
increase the sensitivity on the SD component
foreseen/in progress
Other rare processes:
Astrop.Phys5(1996)217
• Electron decay into invisible channels
129
Xe during CNC processes PLB465(1999)315
• Nuclear level excitation of
• N, NN decay into invisible channels in 129Xe
PLB493(2000)12
• Electron decay: e- → νeγ
PRD61(2000)117301
• 2β decay in 134Xe
PLB527(2002)182
• Improved results on 2β in 134Xe,136Xe
• CNC decay 136Xe → 136Cs
• N, NN, NNN decay into invisible channels in
PLB546(2002)23
Beyond the Desert (2003) 365
136Xe
EPJA27 s01 (2006) 35
DAMA/R&D set-up: results on rare processes
• Particle Dark Matter search with CaF2(Eu)
NPB563(1999)97, Astrop.Phys.7(1997)73
2β decay in 136Ce and in 142Ce
2EC2ν 40Ca decay
2β decay in 46Ca and in 40Ca
2β+ decay in 106Cd
2β and β decay in 48Ca
2EC2ν in 136Ce, in 138Ce
and α decay in 142Ce
• 2β+ 0ν and EC β+ 0ν decay in 130Ba
• Cluster decay in LaCl3(Ce)
•
•
•
•
•
•
Il Nuov.Cim.A110(1997)189
Astrop. Phys. 7(1999)73
NPB563(1999)97
Astrop.Phys.10(1999)115
NPA705(2002)29
NIMA498(2003)352
NIMA525(2004)535
NIMA555(2005)270
Il Nuovo Cim. A112 (1999) 545-575, EPJC18(2000)283, Riv. N.
Cim. 26 n.1 (2003)1-73, IJMPD13(2004)2127
• Reduced standard contaminants (e.g. U/Th of order of ppt) by material selection and growth/handling protocols.
• PMTs: Each crystal coupled - through 10cm long tetrasil-B light guides acting as optical windows - to 2 low background
EMI9265B53/FL (special development) 3” diameter PMTs working in coincidence.
• Detectors inside a sealed Cu box maintained in HP Nitrogen atmosphere in slight
overpressure
• Very low radioactive shields: 10 cm of Cu, 15 cm of Pb + shield from neutrons: Cd foils +
polyethylene/paraffin+ ~ 1 m concrete moderator largely surrounding the set-up
• Installation sealed: A plexiglas box encloses the whole shield and is also maintained in HP
Nitrogen atmosphere in slight overpressure. Walls, floor, etc. of inner installation sealed by
Supronyl (2×10-11 cm2/s permeability).Three levels of sealing.
• Installation in air conditioning + huge heat capacity of shield
• Calibration using the upper glove-box (equipped with compensation chamber) in HP
Nitrogen atmosphere in slight overpressure calibration → in the same running conditions
as the production runs.
• Energy and threshold: Each PMT works at single photoelectron level. Energy threshold: 2
keV (from X-ray and Compton electron calibrations in the keV range and from the features
of the noise rejection and efficiencies). Data collected from low energy up to MeV region,
despite the hardware optimization was done for the low energy
• Pulse shape recorded over 3250 ns by Transient Digitizers.
• Monitoring and alarm system continuously operating by self-controlled computer processes.
+ electronics and DAQ fully renewed in summer 2000
Main procedures of the DAMA data taking for the DMp annual modulation signature
• data taking of each annual cycle starts from autumn/winter (when cosω(t-t0)≈0) toward summer (maximum expected).
• routine calibrations for energy scale determination, for acceptance windows efficiencies by means of radioactive sources
each ~ 10 days collecting typically ~105 evts/keV/detector + intrinsic calibration from 210Pb (~ 7 days periods) +
periodical Compton calibrations, etc.
• continuous onon-line monitoring of all the running parameters with automatic alarm to operator if any out of allowed range.
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
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),
EPJC47(2006)263
data taking completed
on July 2002
total exposure collected in 7 annual cycles 107731 kg×d
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
Time (day)
Acos[ω(t-t0)]
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.
What we can also learn from the multiple/single hit rates. A toy model
A
A’
Rmult
N σ
= Rsingle ⋅ T 2T
4πr
What about the nuclear cross sections of the particle
(A) responsible of the modulation in the single-hit rate
and not in the multiple-hit rate?
N T σ T = N Naσ Na + N I σ I = N ⋅ (σ Na + σ I )
The 8 NaI(Tl) detectors in (anti-)coincidence have 3.1×1026 nuclei of Na and
3.1×1026 nuclei of Iodine. N= 3.1×1026
Rmult
N ⋅ (σ Na + σ I )
≈ Rsingle ⋅
2
4π ⋅ rmed
rmed ∼ 10-15 cm
Therefore, the ratio of the modulation amplitudes is:
From the experimental data:
Hence:
Amult
N ⋅ (σ Na + σ I )
≈
2
Asingle
4π ⋅ rmed
Amult ≈ −(4 ± 8) ⋅10 −4 cpd/kg/keV < 10 −3 cpd/kg/keV;
Asingle ≈ 2 ⋅10 −2 cpd/kg/keV;
Amult
< 5 ⋅10 − 2
Asingle
In conclusion, the particle (A) responsible of the modulation in the single-hit rate and not in the multiple-hit rate
must have:
σ Na + σ I < 0.2 barn
Since for fast neutrons the sum of the two cross sections (weighted by 1/E,
ENDF/B-VI) is about 4 barns:
It (A) cannot be a fast neutron
Running conditions
Temperature
Nitrogen Flux
an example:
DAMA/NaI-6
hardware rate
Distribution of some parameters
Radon
outside the
shield
Pressure
Running conditions stable at level < 1%
Modulation amplitudes obtained by fitting the time behaviours of main
running parameters, acquired with the production data, when including
a modulation term as in the Dark Matter particles case.
outside the
shield
All the measured amplitudes well
compatible with zero
+ none can account for the observed effect
(to mimic such signature, spurious effects and
side reactions must not only be able to
account for the whole observed modulation
amplitude, but also simultaneously satisfy all
the 6 requirements)
[for details and for the other annual cycles see for
example: PLB424(1998)195, PLB450(1999)448,
PLB480(2000)23, RNC26(2003)1-73,
EPJC18(2000)283, IJMPD13(2004)2127]
Can a hypothetical background modulation
account for the observed effect?
Integral rate at higher energy (above 90 keV), R90
• R90 percentage variations with respect to their mean values for single
crystal in the DAMA/NaI-5,6,7 running periods
→ cumulative gaussian behaviour with σ ≈ 0.9%,
fully accounted by statistical considerations
Period
Mod. Ampl.
• Fitting the behaviour with time,
adding a term modulated according DAMA/NaI-5 (0.09±0.32) cpd/kg
DAMA/NaI-6 (0.06±0.33) cpd/kg
period and phase expected for
DAMA/NaI-7 -(0.03±0.32) cpd/kg
Dark Matter particles:
→consistent with zero + if a modulation present in the
whole energy spectrum at the level found in the lowest
energy region → R90 ∼ tens cpd/kg → ∼ 100 σ far away
Energy regions closer to that where the effect is observed e.g.:
Mod. Ampl. (6-10 keV): -(0.0076 ± 0.0065), (0.0012 ± 0.0059) and (0.0035 ± 0.0058) cpd/kg/keV for
DAMA/NaI-5, DAMA/NaI-6 and DAMA/NaI-7; → they can be considered statistically consistent with zero
In the same energy region where the effect is observed:
no modulation of the multiple-hits events (see elsewhere)
No
Nomodulation
modulationin
inthe
thebackground:
background:
these
results
also
account
for
the
bckg
these results also account for the bckgcomponent
componentdue
dueto
toneutrons
neutrons
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
EFFICIENCIES
BACKGROUND
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
+ 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
First case: the case of DM particle scatterings on target-nuclei.
The recoil energy is the detected quantity
DM particle-nucleus elastic scattering
SI+SD differential cross sections:
gp,n(ap,n) effective DM particle-nucleon couplings
⎛ dσ ⎞
⎛
dσ
⎟ + ⎜ dσ ⎞⎟ =
(v,ER ) = ⎜
dER
⎝ dER ⎠ SI ⎝ dER ⎠ SD
2
F
[
2 2
J +1
2G mN ⎧
a p Sp + an Sn
⎨ Zgp + (A− Z)gn FSI (ER ) + 8
2
J
πv ⎩
[
]
] F (E )⎬⎭⎫
2
2
SD
R
<Sp,n> nucleon spin in the nucleus
F2(ER) nuclear form factors
mWp reduced DM particle-nucleon mass
Note: not universal description. Scaling laws assumed to define point-like cross sections from nuclear
a
ones. Four free parameters: mW, σSI, σSD , tgθ = n
ap
Preferred inelastic DM particle-nucleus scattering: χ-+N→ χ++N
• DM particle candidate suggested by D. Smith and N.
Weiner (PRD64(2001)043502)
• Two mass states χ+ , χ- with δ mass splitting
• Kinematical constraint for the inelastic scattering of
χ- on a nucleus with mass mN becomes increasingly
severe for low mN
2δ
1 2
µv ≥ δ ⇔ v ≥ vthr =
2
µ
Three free parameters: mW, σp, δ
Ex.
Sm/S0 enhanced with
respect to the elastic
scattering case
mW =100 GeV
mN
µ
70
41
130
57
Differential energy distribution depends on the assumed scaling laws, nuclear form factors, spin factors,
free parameters (→ kind of coupling, mixed SI&SD, pure SI, pure SD, pure SD through Z0 exchange,
pure SD with dominant coupling on proton, pure SD with dominant coupling on neutron, preferred
inelastic, ...), on the assumed astrophysical model (halo model, presence of non-thermalized components,
particle velocity distribution, particle density in the halo, ...) and on instrumental quantities (quenching
factors, energy resolution, efficiency, ...)
Spin Independent
Examples of different Form
−α (qr )
−α (qr )
from Helm
Ae
+
(1
−
A
)
e
127
I available −(qrn )2 /5
Factor for
e
Helm
in literature
1
Similar situation
for all the target
nuclei considered
in the field
2
2
n
2
charge
spherical
distribution
• Take into account the
structure of target nuclei
• In SD form factor: no
decoupling between nuclear
and Dark Matter particles
degrees of freedom;
dependence on nuclear
potential.
n
−( qrn )2 /5
e
2
−α1(qrn )
Ae
Spin Dependent from
−α2 (qrn )2
+(1− A)e
“thin shell”
distribution
Smith et al.,
Astrop.Phys.6(1996) 87
Ressell et al.
The Spin Factor
Spin Factors for some target-nuclei
calculated in simple different models
Spin Factors calculated on the basis of
Ressell et al. for some of the possible θ
values considering some target nuclei
and two different nuclear potentials
Spin factor = Λ2J(J+1)/ax2
(ax= an or ap depending on the unpaired nucleon)
Spin factor = Λ2J(J+1)/a2
tgθ =
Large differences in the measured counting rate can be expected:
an
ap
(0≤θ<π)
• when using target nuclei sensitive to the SD component of the interaction (such as e.g. 23Na and 127I) with the respect
to those largely insensitive to such a coupling (such as e.g. natGe, natSi, natAr, natCa, natW, natO);
• when using different target nuclei although all – in principle – sensitive to such a coupling, depending on the
unpaired nucleon (compare e.g. odd spin isotopes of Xe, Te, Ge, Si, W with the 23Na and 127I cases).
Quenching factor
recoil/electron response ratio measured with a
neutron source or at a neutron generator
Quenching factors, q, measured by
neutron sources or by neutron beams
for some detectors and nuclei
Ex. of different q determinations for Ge
Astrop. Phys.3(1995)361
• differences are often present in different
experimental determinations of q for the
same nuclei in the same kind of detector
• e.g. in doped scintillators q depends on
dopant and on the impurities/trace
contaminants; in LXe e.g.on trace impurities,
on initial UHV, on presence of
degassing/releasing materials in the Xe, on
thermodynamical conditions, on possibly
applied electric field, etc.
• Some time increases at low energy in
scintillators (dL/dx)
assumed 1 (but 0.91 ±
0.03 in astro-ph/0607502 )
Consistent Halo Models
• Isothermal sphere ⇒ very simple but unphysical halo model; generally not considered
• Several approaches different from the isothermal sphere model: Vergados PR83(1998)3597,
PRD62(2000)023519; Belli et al. PRD61(2000)023512; PRD66(2002)043503; Ullio & Kamionkowski
JHEP03(2001)049; Green PRD63(2001) 043005, Vergados & Owen astroph/0203293, etc.
Models accounted in the following
(Riv. N. Cim. 26 n.1 (2003)1-73 and previously in
PRD66(2002)043503 )
• Needed quantities
→ DM local density
ρ0 = ρDM (R0 = 8.5 kpc)
→ local velocity
v0 = vrot (R0 = 8.5kpc)
r
→ velocity distribution f (v )
• Allowed ranges of ρ0 (GeV/cm3) have been
evaluated for v0=170,220,270 km/s, for each
considered halo density profile and taking
into account the astrophysical constraints:
v0 = (220± 50)km⋅ s −1
1⋅1010 M ⊕ ≤ M vis ≤ 6 ⋅1010 M ⊕
0.8 ⋅ v0 ≤ vrot (r = 100kpc) ≤ 1.2 ⋅ v0
NOT YET EXHAUSTIVE AT ALL
Halo modeling
• Needed quantities for Dark Matter direct searches:
→ DM local density ρ0 = ρDM (R0 = 8.5 kpc)
→ local velocity
v0 = vrot (R0 = 8.5kpc)
r
→ velocity distribution f (v )
Axisymmetric ρDM → q flatness
Isothermal sphere: the most widely used (but not correct) model
density profile: ρ DM (r ) ∝ r −2
2
gravitational potential: Ψ 0 ∝ log(r )
Ψ 0 (r , z ) = −
→ Maxwellian velocity distribution
Spherical ρDM, isotropic velocity dispersion
Evans’
logarithmic
ρ DM (r ) =
v
3R + r
4π G ( Rc2 + r 2 ) 2
2
0
2
c
2
Ψ 0 (r ) = −
Triaxial ρDM → p,q,δ
2
0
v
log( Rc2 + r 2 )
2
2
(r ) = vc2
vrot
2
r
(R + r 2 )
2
c
Evans’
βΨ a Rcβ 3Rc2 + r 2 (1 − β )
Ψ a Rcβ
βΨ a Rcβ r 2
2
ρ
Ψ
(
)
=
,
(
β
≠
0)
(
)
(
r
)
=
r
v
r
=
0
rot
power-law DM
( Rc2 + r 2 ) β / 2
( Rc2 + r 2 )( β + 2) / 2
4π G ( Rc2 + r 2 )( β + 4) / 2
γ
Others:
α
⎛ R ⎞ ⎡1 + ( R0 / a) ⎤
ρ DM (r ) = ρ 0 ⎜ 0 ⎟ ⎢
α ⎥
⎝ r ⎠ ⎣ 1 + (r / a) ⎦
( β −γ ) / α
Spherical ρDM with non-isotropic velocity dispersion →
Constraining the models
⎛
v02
z2 ⎞
log ⎜ Rc2 + r 2 + 2 ⎟
q ⎠
2
⎝
v0 = (220 ± 50)km ⋅ s −1
β0 = 1 −
vφ2
vr2
1 ⋅1010 M ⊕ ≤ M vis ≤ 6 ⋅1010 M ⊕
⎛ 2 y2 z2 ⎞
v02
Ψ 0 ( x, y, z ) = − log ⎜ x + 2 + 2 ⎟
2
p
q ⎠
⎝
δ = free parameter → in
spherical limit (p=q=1)
quantifies the anisotropy of
the velocity dispersion tensor
vφ2
2
r
v
=
2 +δ
2
0.8 ⋅ v0 ≤ vrot (r = 100kpc) ≤ 1.2 ⋅ v0
Few examples of corollary quests
for the WIMP class
(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
An example of the effect induced by a non-zero
SD component on the allowed SI regions
• Example obtained considering Evans’ logarithmic axisymmetric C2 halo model
with v0 = 170 km/s, ρ0 max at a given set of parameters
• The different regions refer to different SD contributions with θ=0
a) σSD = 0 pb;
c) σSD = 0.04 pb;
e) σSD = 0.06 pb;
b) σSD = 0.02 pb;
d) σSD = 0.05 pb;
f) σSD = 0.08 pb;
A small SD contribution ⇒
drastically moves the allowed region in
the plane (mW, ξσSI) towards lower SI
cross sections (ξσSI < 10-6 pb)
Similar effect for whatever
considered model framework
• There is no meaning in bare comparison
between regions allowed in experiments
sensitive to SD coupling and exclusion plots
achieved by experiments that are not.
• The same is when comparing regions allowed
by experiments whose target-nuclei have
unpaired proton with exclusion plots quoted
by experiments using target-nuclei with
unpaired neutron where θ ≈ 0 or θ ≈ π.
Supersymmetric expectations in MSSM
•Assuming for the neutralino a
dominant purely SI coupling
•when releasing the gaugino
mass unification at GUT scale:
M1/M2≠0.5 (<);
(where M1 and M2 U(1) and
SU(2) gaugino masses)
low mass configurations
are obtained
figure taken from PRD69(2004)037302
scatter plot of theoretical configurations vs DAMA/NaI allowed region in the given model
frameworks for the total DAMA/NaI exposure (area inside the green line);
(for previous DAMA/NaI partial exposure see PRD68(2003)043506)
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.
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 Sagittarius Dwarf satellite galaxy
(SagDEG) for WIMPs
EPJC47 (2006)
263
Possible contributions due to the tidal
stream of Sagittarius Dwarf satellite
(SagDEG) galaxy of Milky Way
DAMA/NaI: seven annual cycles 107731 kg d for some
SagDEG modelling
Few examples
stream
sun
pure SD case:examples of slices of the
3-dim allowed volume
pure SI case
green areas:
no SagDEG
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 - 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
What about the indirect searches of DM particles in the space?
It was already noticed in 1997 that the
EGRET data showed an excess of gamma ray
fluxes for energies above 1 GeV in the
galactic disk and for all sky directions.
The EGRET Excess of Diffuse Galactic Gamma Rays
astro-ph/0211286
PLB536(2002)263
EGRET data, W.de Boer, hep-ph/0508108
interpretation, evidence itself, derived mW and
cross sections depend e.g. on bckg modeling, on DM
spatial velocity distribution in the galactic halo, etc.
Hints from indirect searches are not in conflict
with DAMA/NaI for the WIMP class candidate
In next years new data from DAMA/LIBRA (direct detection)
and from Agile, Glast, Ams2, Pamela, ... (indirect detections)
... not only neutralino, but also e.g. ...
... sneutrino, ...
PLB536(2002)263
... or Kaluza-Klein DM
PRD70(2004)115004
... or neutrino of 4th family
hep-ph/0411093
Example of joint analysis of DAMA/NaI and
positron/gamma’s excess in the space in the light of two
DM particle components in the halo
in the given frameworks
in the given frameworks
Another class of DM candidates:
light bosonic particles IJMPA21 (2006) 1445
The detection is based on the total conversion
of the absorbed bosonic mass into electromagnetic radiation.
In these processes the target nuclear recoil is negligible and not involved in the
detection process (i.e. signals from these candidates are lost in experiments
applying rejection procedures of the electromagnetic contribution)
Axion-like particles: similar phenomenology with ordinary matter as the axion, but
significantly different values for mass and coupling constants allowed.
A wide literature is available and various candidate particles have been and can be
considered.
A complete data analysis of the total 107731 kgxday exposure from DAMA/NaI has been
performed for pseudoscalar (a) and scalar (h) candidates in some of the possible scenarios.
Main processes involved in the detection:
They can account for the
DAMA/NaI observed effect as
well as candidates belonging to
the WIMPs class
,h
,h
h
a
S0
S0,Sm
S0,Sm
h
S0,Sm
S0
S0,Sm
The pseudoscalar case
IJMPA21 (2006) 1445
Analysis of 107731 kg day exposure from DAMA/NaI.
Allowed multi-dimensional volume in the space defined by ma and all coupling
constants to charged fermions (3σ C.L.) in the given frameworks
Maximum allowed
photon coupling
Axioelectric contribution dominant in all “natural”
cases → allowed region almost independent on
the other fermion coupling values
only electron coupling
coupling model
cosmological interest:
at least below
Di Lella, Zioutas
AP19(2003)145
UHECR - PRD64(2001)096005
Majoron as in PLB99(1981)411; coupling to photons vanish at first order:
g aγγ ≈
1 g
4 g
α ⎡ g ae e
⎛ g ae e g ad d
g
9 ad d
9 au u ⎤
3
3
+
+
=
= − au u
⎥ ≈ 0 ⎜⎜
⎢
π ⎣ me
md
mu ⎦
md
mu
⎝ me
⎞
⎟⎟
⎠
Also this can account for the DAMA/NaI observed effect
The scalar case
Allowed multi-dimensional volume in the space defined by mh and all the coupling
constants to charged fermions (3σ C.L.) in the given frameworks
IJMPA21(2006)1445
1) electron coupling does not provide modulation
2) from measured rate: ghee < 3 10-16 to 10-14 for mh ≈ 0.5 to 10 keV
3) coupling only to hadronic matter: allowed region in g h N N vs. mh
(3σ C.L.)
DAMA/NaI allowed region in
the considered framework.
If all the couplings to
quarks of the same order:
lifetime dominated by u
and d loops:
g hγγ
(
)
ghNN = ghuu + 2ghdd +
(
Z
ghuu − ghdd
A
2
1 g
α ⎡4 g
2 α Qq g hq q
9 hd d ⎤
≈ ∑−
≈ − 2 ⎢ 9 hu u +
⎥
3 π mq
π ⎣ mu
md ⎦
q
)
h configurations of cosmological
interest in ghuu vs ghdd plane
Many other configurations of cosmological interest
are possible depending on the values of the
couplings to other quarks and to gluons….
• Annual modulation signature present for a scalar
particle with pure coupling to hadronic matter
(possible gluon coupling at tree level?).
• Compton-like to nucleus conversion is the dominant
process for particle with cosmological lifetime.
• Allowed by DAMA/NaI (for mh > 0.3 keV )
• τh > 15 Gy (lifetime of cosmological interest)
• mu = 3.0 ± 1.5 MeV md = 6.0 ± 2.0 MeV
Also this can account for the DAMA/NaI observed effect
FAQ:
... DAMA/NaI “excluded” by CDMS-II (and others)?
OBVIOUSLY NO
They give a single model dependent result using natGe target
DAMA/NaI gives a model independent result using 23Na and 127I targets
Even assuming their expt. results as they give them …
Case of DM particle scatterings on target-nuclei
N
in o d
co dep ire
m en ct
pa d m
ris en od
on t el
po
ssi
bl
e
•In general? OBVIOUSLY NO
The results are fully “decoupled” either because of the different sensitivities to the various kinds
of candidates, interactions and particle mass, or simply taking into account the large uncertainties
in the astrophysical (realistic and consistent halo models, presence of non-thermalized components,
particle velocity distribution, particle density in the halo, ...), nuclear (scaling laws, FFs, SF) and
particle physics assumptions and in all the instrumental quantities (quenching factors, energy
resolution, efficiency, ...) and theor. parameters.
•At least in the purely SI coupling they only consider? OBVIOUSLY NO
still room for compatibility either at low DM particle mass or simply accounting for the large
uncertainties in the astrophysical, nuclear and particle physics assumptions and in all the expt. and
theor. parameters.
Case of bosonic candidate (full conversion into electromagnetic radiation)
•These candidates are lost by these expts. OBVIOUSLY NO
(see also in Riv. N. Cim. 26 n. 1(2003)1-73 and IJMPD13(2004)2127,
several papers in literature, astro-ph/0511262)
Thenew
newDAMA/
DAMA/LIBRA
set-up~250
~250kg
kgNaI(Tl
NaI(Tl)
The
LIBRA set-up
)
(Largesodium
sodiumIodide
IodideBulk
Bulkfor
forRAre
RAreprocesses)
processes)
(Large
As a result of a second generation R&D for more radiopure NaI(Tl)
by exploiting new chemical/physical radiopurification techniques
(all operations involving crystals and PMTs - including photos - in HP Nitrogen atmosphere)
PMT
+HV
divider
Cu etching with
super- and ultrapure HCl solutions,
dried and sealed in
HP N2
storing new crystals
improving installation
and environment
etching staff at work
in clean room
(all operations involving crystals and PMTs -including photos- in HP N2 atmosphere)
detectors during installation; in
the central and right up
detectors the new shaped Cu
shield surrounding light guides
installing DAMA/LIBRADAMA/LIBRA
detectors
in data taking since March 2003,
(acting also as optical windows)
waiting
for
a
larger
exposure
than
DAMA/NaI
assembling a DAMA/ LIBRA detector
and PMTs was not yet applied
filling the inner Cu box with
further shield
closing the Cu box
housing the detectors
view at end of detectors’
installation in the Cu box
Some infos about DAMA/LIBRA data acquisition
DAMA/LIBRA in operation since March 2003
e.g. up to March 2006: exposure: of order of 105 kg x d
overall sources’ data: of order of 4 x 107 events
Few examples of operational features
(here from March 2003 to August 2005):
Stability of the low energy
calibration factors
routine calibrations
(all the detectors together)
σ
E
σ=0.9%
σ=0.4%
frequency
241Am
frequency
ratio of the peaks’ positions
Stability of the high
energy calibration
factors
(60keV ) = 7.4%
E (keV)
tdcal − tdcal
tdcal
α ≈2
f HE − f HE
f HE
Perspectives of DAMA/LIBRA
Model independent approach:
reachable C.L. as function of running time
and of the low energy bckg rate. The
shaded regions account for several model
frameworks.
Example of corollary model dependent
quests for the candidate particle in a single
simplified model/analysis framework:
e.g., role of the increase of statistics and of the
improvement in the bckg rate to identify a SI/SD coupled
WIMP candidate in a particular given model framework of
the many possible
Assumptions:
• 1σ C.L.
• v0=220km/s,
fixed params
• isothermal
spherical halo
• etc.
• Allowed regions evaluated by simulating the response of
the ~250 kg NaI(Tl) set-up to a WIMP having
mW=60GeV, σSI=10-6 pb, σSD=0.8 pb and θ=2.435rad.
• Various exposure times are considered (from 1 to 5y).
• In each panel different bckg rate.
More complete scenarios would be investigated and
several uncertainties accounted for
(see e.g. Riv.N.Cim.26n.1(2003)1-73)
… other astrophysical scenarios?
Possible non-thermalized multicomponent galactic halo? In the galactic halo, fluxes
of Dark Matter particles with dispersion velocity relatively low are expected :
Possible contribution due to
the tidal stream of Sagittarius
Dwarf satellite galaxy of
Milky Way
stream
Possible presence of caustic rings
⇒ streams of Dark Matter particles
sun
K.Freese et al. astro-ph/0309279
Fu-Sin Ling et al. astro-ph/0405231
Interesting scenarios for DAMA
Effect on |Sm/So|
respect to “usually”
adopted halo models?
Effect on the phase of
annual modulation
signature?
Canis Major
simulation:
astro-ph/0311010
Other dark matter stream from satellite galaxy
of Milky Way close to the Sun?
Position of the Sun:
.....very likely....
(-8,0,0) kpc
Can be guess that spiral galaxy like Milky Way have been formed
capturing close satellite galaxy as Sgr, Canis Major, ecc…
An example of possible signature for the
presence of streams in the Galactic halo
Phase (day of maximum)
The effect of the streams on the phase depends on the galactic halo model
Expected phase in the absence of
streams t0 = 152.5 d (2nd June)
Evans’log axisymmetric non-rotating,
v0=220km/s, Rc= 5kpc, ρ0 max + 4% Sgr
NFW spherical isotropic non-rotating,
v0=220km/s, ρ0 max + 4% Sgr
Example, NaI: 3 105 kg d
The higher sensitivity of DAMA/LIBRA
will allow to more effectively investigate
the presence or contributions of streams
E (keVee)
in the galactic halo
DAMA/NaI results:
(2-6) keV
t0 = (140 ± 22) d
Conclusions
Dark Matter investigation is a crucial challenge in the incoming years for
cosmology and for physics beyond the standard model
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
(IJMPA21(2006)1445)
• halo substructures (SagDEG) effects
(EPJC 47 (2006) 263)
• and more in progress...
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