Lectures on Dark Matter: Theory and Experiments
JENNIFER Summer School on Particle Physics and Detectors
Gianluca Inguglia- DESY
Sporthotel Grünberg
28-29/07/2016
1
Why shall we search for dark matter?
●
Various reasons to agree that dark matter (DM) exists
● But the nature of DM is unknown and understanding what dark matter is represents
one of the biggest challenges our community is facing this days
In these lectures we will see how dark matter was discovered through its gravitational
effects and and how we search for it in current experiments.
The first part of the lectures will be devoted to the study of the events that in the past have
lead to the gravitational discovery of dark matter. In the second part we will go through
some of the most used experimental techniques in the hunt for dark matter.
You might want to prepare pencil and paper...
From the virial theorem to the first anomaly in the Coma cluster
Fritz Zwicky 1898-1974
blackboard calculations...
From the virial theorem to the first anomaly in the Coma cluster
blackboard calculations...
Rotation curve of a galaxy: the case of NGC3198
blackboard calculations...
Keplerian distribution of velocity in the solar system
Rotation curve of a galaxy: the case of NGC3198
1kpc=3.26 ly=3.086x1013 km=2.063x108 AU
Gravitational lensing
Combining lensing with different observations:
Mapping the mass distribution
stars
galaxies
X-rays
The Bullet cluster: optical
X-rays
Combined Bullet cluster images (X-rays+Weak lensing)
Animation 1: The Bullet cluster
Baryonic Matter (With other interactions than gravitational)
Dark matter (only gravitational interaction)
Animation 2: The Bullet cluster
optical+X+DM
Animation 3: the Bullet cluster on a “longer”
timescale
The Planck Satellite Mission: Measuring the
Cosmic Microwave Background (CMB)
The Planck Satellite Mission: Measuring the
Cosmic Microwave Background (CMB)
The Planck Satellite Mission: How the CMB
Spectrum is obtained from the data
The Planck Satellite Mission: from the CMB to the
power spectrum
The Planck Satellite Mission: results suggests a very large
component of dark “stuffs” in the Universe
What's next?
●
Various reasons to agree that dark matter (DM) exists
● But the nature of DM is unknown and understanding what dark matter is represents
one of the biggest challenges our community is facing this days
What are possible dark matter candidates?
●
●
One possibility is represented by the lightest SUSY particle (which is stable)
● But why should we have only one DM particle when density of DM is 5 times larger
the density of visible matter (i.e. many SM particles)?
Many new models have been and are currently being developed to propose a more
complex sector for dark matter explaining also anomalies observed in astrophysical
process → dark sector(s).
Is dark matter mainly composed of “standard matter”?
Possible astronomical candidates: MACHOs – Massive Astrophysical
Compact Halo Objects
Brown Dwarfs: H/He spheres with m < 0.08 M⊙
(too light, H-burning will never start)
Jupiters: similar but with m < 0.001 M⊙
Black Holes with m ~ 100 M⊙
could be remnants of an early generation of stars which
were massive enough so that not many heavy elements
were dispersed when they exploded as supernovae
However, not enough MACHO's found to explain dark matter effects...
Is dark matter mainly composed of “standard matter”?
Possible particle candidates: neutrinos!
They are EM neutral, they have mass (remember mixing), their interaction with
matter is weak, and they are produced in the early Universe.
Density: nυ~300 cm-3
Before we used a quantity, called critical density:
ρc=5.1 GeV/m3 = 5100 eV/cm3.
If neutrino masses are such that
∑ m(νl )c 2 [l=e ,μ , τ]=44.3 eV
l
Then they could represent the whole energy content of the Universe, but 1)
experimentally
2
∑ m(νl )c [l=e ,μ , τ]<0.2 eV
l
(so they are “hot” dark matter candidates, they move fast and far)
and 2) “small” scale structures (galaxies, clusters..) formation require mDM>2KeV.
Is dark matter mainly composed of supersymmetric (SUSY)
particles?
Is dark matter mainly composed of supersymmetric (SUSY)
particles?
●
Space-time symmetry:
●
●
half integer spin SM ↔ integer spin SUSY
integer spin SM
↔ half integer spin SUSY
●
Soft SUSY breaking
●
(soft) SUSY breaking terms diagonal in flavour space
●
Introduce R-party
3(B − L)+2 S
P R (SM )=+1,
Q) What does this imply?
P R=(−1)
P R (SUSY )=−1,
P R (vertex)=+1
Is dark matter mainly composed of supersymmetric (SUSY)
particles?
●
Space-time symmetry:
●
●
half integer spin SM ↔ integer spin SUSY
integer spin SM
↔ half integer spin SUSY
●
Soft SUSY breaking
●
(soft) SUSY breaking terms diagonal in flavour space
●
Introduce R-party
3(B − L)+2 S
P R=(−1)
P R (SUSY )=−1,
P R (SM )=+1,
e
~
χ 10
-
~
e
e
+
~
χ 10
~
A
P R (vertex)=+1
~
B
C
~
χ 10
~
?
C
Lightest SUSY particle
can NOT decay!
Is our understanding of gravitation incomplete?
Can Modified Newtonian Dynamics (MOND) theories account
for dark matter?
MOND theories refer to a correction of Newton's law that take into
account a scale factor
GM
r
The correction is very simple:
F= 2 f ( )
r0
r
and
r 0 =few×kpc
f ( x)=1( x≤1)
f ( x)=x ( x ≫1)
MOND theories are then parametrised by only one free parameter:
mass-to-light ratio
The agreement between predicted rotation curves with MOND and observation
is astonishing
27
Is our understanding of gravitation incomplete?
Can Modified Newtonian Dynamics (MOND) theories account
for dark matter?
MOND theories however they cannot explain this...
A Study of the Dark Core in A520 with Hubble Space Telescope: The
Mystery Deepens
Astrophys.J. 747 (2012) 96
DOI: 10.1088/0004-637X/747/2/96
e-Print: arXiv:1202.6368 [astro-ph.CO]
Is DM interacting in region 3?
30
Is dark matter related to a dark sector with dark matter
particles and forces?
A very simple example...
γ - A 'mixing
χ1
A'
hD
( ... )
χ2 (?)
31
Is dark matter related to a new dark sector with dark forces?
Dark photon first proposed in
➔
➔
➔
P. Fayet, Phys. Lett. B 95, 285 (1980),
P. Fayet Nucl. Phys. B 187, 184 (1981).
(Holdom, 1986) A boson belonging to an additional U(1)' symmetry would mix
kinetically with the photon:
The kinetic mixing is a term in the Lagrangian expressed by
1
ϵ F Yμ ν F ' μ ν
2
For the dark photon to acquire mass an extended Higgs sector is required to break
the new U(1)' symmetry
Note: є is the strength of the kinetic mixing and it is supposed to be small,
10-5-10-2, the smaller the value of є the longer A' lifetime (i.e. long lived).
The Mass of the new boson should be in the range few MeV to few Gev (Nima
Arkani-Hamed et al. Phys. Rev. D 79, 015014, 2009).
32
Searching for dark matter
χ
SM
χ
SM
2
Searching for dark matter
SM
Direct detection
χ
Search for interaction of DM
particles with (usually)
underground detectors:
heat, scintillation light, etc..
χ
SM
2
Searching for dark matter
χ
Direct detection
SM
Search for interaction of DM
particles with (usually)
underground detectors:
heat, scintillation light, etc..
SM
χ
Indirect detection
Space/earth based
experiments: gamma ray
energy excess, anti-particle
excess, HE neutrinos etc.
2
Searching for dark matter
Direct production @ colliders
χ
Direct detection
SM
Search for events with
missing energy, particle
disappearance, dark
forces, etc.
Search for interaction of DM
particles with (usually)
underground detectors:
heat, scintillation light, etc..
SM
χ
Indirect detection
Space/earth based
experiments: gamma ray
energy excess, anti-particle
excess, HE neutrinos etc.
2
Searching for dark matter
Direct production @ colliders
χ
Direct detection
SM
Search for events with
missing energy, particle
disappearance, dark
forces, etc.
Search for interaction of DM
particles with (usually)
underground detectors:
heat, scintillation light, etc..
SM
χ
Indirect detection
Space/earth based
experiments: gamma ray
energy excess, anti-particle
excess, HE neutrinos etc.
2
Searching for dark matter
χ
Direct detection
ct
e
r
Di
d
pr o
u
n
o
i
t
c
@
l
Be
le 2
SM
Search for events with
missing energy, particle
disappearance, dark
forces, etc.
Search for interaction of DM
particles with (usually)
underground detectors:
heat, scintillation light, etc..
SM
χ
Indirect detection
Space/earth based
experiments: gamma ray
energy excess, anti-particle
excess, HE neutrinos etc.
2
Searching for dark matter: direct detection
SM
Direct detection
χ
Search for interaction of DM
particles with (usually)
underground detectors:
heat, scintillation light, etc..
χ
SM
2
Principles of direct detection
χ
χ
N
Detector
Principles of direct detection
χ
χ
N
Detector
Type of detectors:
●
●
●
●
Liquid gas (2-phase)
Cryogenic detectors
Scintillation
Bubble chambers...
Type of interactions:
●
●
●
Collisions with atomic nuclei
Elastic scattering
Low energy recoil
Galactic halo
General galaxy structure: baryonic matter in the bulge+disk
surrounded by a halo of dark matter particles
Maxwell-Boltzmann velocity distribution:
2
−3|v|
2
2σ
f ( v)=Ne
Galactic halo
General galaxy structure: baryonic matter in the bulge+disk
surrounded by a halo of dark matter particles
Galactic kinematics provides information about
properties of DM halo:
Earth moves through the halo at v0=220 km/s,
WIMP escape velocity: vesc=544 km/s
WIMP density (local): 0.3 GeV/cm3 (0.2-0.56)
Maxwell-Boltzmann velocity distribution:
2
−3|v|
2
2σ
f ( v)=Ne
Principles of direct detection
χ
χ
N
Detector
ρχ
×⟨ v ⟩
Assuming WIMP masses of the order of 100 GeV/c2, the flux on Earth is: ϕ χ =
mχ
NA
-38
2
If A=100 and cross-section 10 cm :
R=
×ϕχ ×σ∼0.1 events / kg / year
A
Principles of direct detection
χ
Recoil energy is calculated from the
scattering angle in the cms:
2
|q|
ER=
2 mN
q = mom. transfer=
χ
2
N
So
Detector
2μ 2 v 2 (1−cos θ)
2
μ v (1−cos θ )
ER=
mN
mχ mN
μ=
mχ + mN
Where v and θ are the WIMP mean
velocity (relative to the detector and
typically ~ 1-200 km/s) and the
scattering angle in the cms
χ
θ
θ
N
Principles of direct detection
Minimal wimp speed to cause recoil:
√
√
2 ER
ER mN
mχ +m N
v min = (
)= (
)=
2
r mχ
mχ
2μ
√
ER
(
)
2 mN
Principles of direct detection
−E R
r
0
R0 E
dR
=
e
dE R E0 r
R is event rate per mass unit, ER is the nuclear recoil energy, R0 is the total event rate, E0 is
the most probable WIMP energy according to M-B distribution, and r is the kinematic factor,
r=
4 mχ mN
2
(m χ + m N )
∞
dR
dR
R0 =∫
dE R → ⟨ E R ⟩=∫ E R
dE R = E 0 r
dE R
0 dE R
0
log(dR/ER)
∞
ER
Principles of direct detection
−E R
r
0
R0 E
dR
=
e
dE R E0 r
R is event rate per mass unit, ER is the nuclear recoil energy, R0 is the total event rate, E0 is
the most probable WIMP energy according to M-B distribution, and r is the kinematic factor,
r=
4 mχ mN
2
(m χ + m N )
∞
∞
dR
dR
R0 =∫
dE R → ⟨ E R ⟩=∫ E R
dE R = E 0 r
dE
dE
0
R
0
R
Let's assume for simplicity that:
1)
m χ =m N =100 GeV / c 2 → r =1
2) Stationary DM halo: mean WIMP velocity wrt to detector v~220km/s=0.75x10-3 c
1
1
2
⟨ E R ⟩= E 0= m χ v = 100 GeV / c 2 (0.75×10−3 c)2
2
2
Mean recoil energy deposit: ⟨ E R ⟩ = 30 KeV
CDMS: Cryogenic Dark Matter Search
When dark matter interact with a nucleus of the detector, the recoiling nucleus
produces crystal lattice vibrations (phonons) and e-h pairs (electron-hole). Through
a technique called photolithography, phonon and charge signals are
detected/captured by electrodes applied to the faces of the crystal.
When phonons reach one face of
the crystal they break apart weekly
bound electron pair in a (thin)
superconducting aluminum layer.
The resulting quasiparticles heat a
transition-edge sensor bonded to
the aluminum layer, causing a
detectable change in its resistance
R(t).
Thanks to the presence of a small
electric field, charge carriers are
drifted to one face of the crystal,
and are detected with a a sensitive
amplifier, Q(t).
The Large Underground
Xenon experiment
A massive particle interacts inside the
LUX detector with Xenon atoms and it
produces ultraviolet photons (~175
nm) and electrons.
Signal 1 (S1)
The photons move at the speed of
light and are immediately detected by
PMT.
An electric field applied to the liquid
xenon drifts the electrons toward the
surface.
An electric field much higher than that
applied to the liquid xenon is applied
above the liquid surface. This pulls
out the electrons of the liquid into the
gas.
In the gas electrons produce
electroluminescence photons.
Signal 2 (s2): electroluminescence
photons are detected by PMT.
The detector is isolated from background thanks to surrounding water tank and shielded
from cosmic background by above earth. A signal of single particle interaction with liquid
xenon is identified by the pair of S1 and S2 signals.
21-07-2016
2 x 10-46 for
M=50 GeV/c2
Searching for dark matter: indirect detection
χ
SM
χ
SM
Indirect detection
Space/earth based
experiments: gamma ray
energy excess, anti-particle
excess, HE neutrinos etc.
2
Different signatures → different experiments
Gamma:
HESS, MAGIC, VERITAS
FERMI-LAT
CTA
Neutrino:
Amanda, Icecube
Antares, Nemo, Nestor,
Km3Net
Antimatter:
PAMELA
AMS-02
Examples of neutrino telescopes
Examples of neutrino telescopes
Searching for dark matter: direct production @ colliders
Direct production @ colliders
χ
SM
χ
SM
Search for events with
missing energy, particle
disappearance, dark
forces, etc.
2
Typical events containing neutralino in the final state when
searching dark matter in pp collisions
ATLAS results with 20.3 fb-1 of data
Dark sector searches
A'= dark photon, HD= dark Higgs boson, χ= dark matter
Most dark sector models require an additional U(1) symmetry responsible for the
“interactions” between dark sector particles and SM particles through its gauge boson A' .
1
Y
μν
ϵ Fμν F '
2
P. Fayet, Phys. Lett. B 95, 285 (1980),
P. Fayet Nucl. Phys. B 187, 184 (1981).
B. Holdom, Phys. Lett. B 166, 196 (1986)
Kinetic mixing strength
A massive force mediator of the extra U(1) symmetry requires the U(1) symmetry
to be broken: extended Higgs sector
●
M(A') ~ GeV scale → mixing with the photon, SM final states accessible
●
M(A') ~ EW scale → mixing with Z0, effects in rare decays (Y, B, ..) through loops1
●
M(A') ~ TeV scale → effects in rare decays (Y, B, ..) through loops1
●
M(hD)~ GeV scale → dark higgs-strahlung, rare decays
●
M(χ) ~ GeV scale: B→χχ,B→νχ; Y(1S)→χχ;Y(3S)→χχγ, A' → χχ
Invisible B/Y decays not accessible at hadron colliders→BELLE2!
Remember the lesson from the past, new particles are first seen indirectly or
in loops: Z0, charm, top
1
Dark sector searches: constraining the kinetic mixing
Most dark sector models require an additional U(1) symmetry responsible for the
“interactions” between dark sector particles and SM particles through its gauge boson A' .
1
Y
μν
ϵ Fμν F '
2
P. Fayet, Phys. Lett. B 95, 285 (1980),
P. Fayet Nucl. Phys. B 187, 184 (1981).
B. Holdom, Phys. Lett. B 166, 196 (1986)
Kinetic mixing strength
A massive force mediator of the extra U(1) symmetry requires the U(1) symmetry
to be broken: extended Higgs sector
BaBar, ArXiv: 1406.2980 [Hep-Ex]
+ - + A '→ e e ,μ μ [ prompt]
Dark photon search strategy
e + (e - )
γ
+
+
+
e , μ , π ..
A'
e + , μ+ , π+ ..
-
+
e (e )
~ mm−cm
A'
-
-
-
-
-
e ,μ , π ..
-
e ,μ , π ...
A'= dark photon, either short or long lived.
A' decays to SM final states through kinetic mixing (if allowed by kinematics). Low multiplicity
final states. 2 charged tracks (forming a vertex in the interaction region or a displaced vertex)
and 1 photon.
B. Batell, et al.
Phys. Rev. D 79, 115008
A ' →μ + μA ' → e+ e68
Upper limits to kinetic mixing
BaBar, ArXiv:
BABAR:
ArXiv:1406.2980
1406.2980[Hep-Ex]
[Hep-Ex]
+ + - + - + e ,μ μ [ prompt]
A ' → e e ,μ Aμ'→, e prompt
Many constraints for different
region of the parameter space
from different experiments.
Shown here:
-top left: BaBar ,
-bottom left NA48,
-bottom right CMS (containing
ATLAS)
ATLAS +
CMS:
dark photon
explanation
of (g-2)μ
ruled out for
A' →e+e-
highly
modeldependent!
'
NA48 arXiv:1504.00607
π0 decays
arXiv:1506.00424 [hep-ex]
Long lived, decays to leptons
69
Expected Belle II sensitivity
e + e - →γ A '→ γ e + e - , γ μ + μ - , prompt
Very conservative estimation of Belle II sensitivity to prompt decays of A'
based on BABAR results projected to full Belle 2 luminosity
70
Dark photon decays to light dark matter
See R. Essig et al. JHEP11 (2013) 167.
e + (e - )
γ
χ
e - (e + )
A'
χ
A'= dark photon, χ= dark matter particle (neutral under SU(3)xSU(2)xU(1))
A' decays to dark matter. On-shell or off-shell with different gamma spectrum .
radiative production in e+e- collisions
*
2
only one photon in the final state with E γ =( s−M A ' )/ 2 √ s
No existing limits
Requires high rate single photon trigger, not available in Belle. Belle II will have a single
photon trigger.
71
Dark photon decays to light dark matter
See R. Essig et al. JHEP11 (2013) 167.
e + (e - )
γ
χ
e - (e + )
A'
χ
72
Additional searches for light dark matter
BABAR:
Phys.Rev.Lett.107:021804,20
11 Y (1 S )→ γ( A 0 →)χ χ
BABAR:
arXiv:0808.0017
0
0
Y (3 S)→ γ A , A → χ χ
14.4 fb-1 @ Y(2S)
14.4 fb @ Y(2S)
-1
28.5 fb-1 @
Y(3S)
73
Invisible Y(1S) decays
Y(nS): bound state of a b quark and a b antiquark
2
4
2
BR (Y (1 S )→ν ν̄) 27 G M Y (1 S)
4 2
−4
=
(−1+
sin
θ
)
=4.14×10
W
+ 2 2
3
BR(Y (1 S )→e e )
64 π α
BR (Y (1 S )→ν ν̄)∼9.9×10−6
➔
➔
➔
Low mass dark matter particles however might might play a
role in the decays of Y(1S), having Y(1S)→χχ if kinematic
allowed.
[Phys. Rev. D 80, 115019, 2009]
e + e - →Y (3 S)
↓(4.4%)
Y (3 S)→ π+ π- Y (1 S)
↓
Y (1 S)→invisible
e + e - →Y (2 S )
↓(18.1%)
Y (2 S)→π + π- Y (1 S)
↓
Y (1 S)→invisible
Belle2 Simulation
Y(3S)→π+π-Y(1S),
Y(1S)→ νν
Also, new mediators (Z', A0, h0) or SUSY particles might
enhance Y(1S)→νν(γ).
[Phys. Rev. D 81, 054025, 2010]
In absence of new physics enhancement, Belle2 should be
able to observe the SM Y(1S)→νν
~ 900 MeV available for Pπ π
2
2
M Y (3 S ) =10.355 GeV /c , M Y (2 S )=10.023GeV / c , M Y (1 S )=9.460 GeV /c
~ 540 MeV available for P π π
2
74
Invisible Y(1S) decays
2
4
27 G M Y (1 S)
BR (Y (1 S )→ν ν̄)
4 2 2
−4
=
(−1+
sin
θ
)
=4.14×10
W
3
BR(Y (1 S )→e + e - )
64 π2 α 2
BR (Y (1 S )→ν ν̄)∼9.9×10−6
➔
➔
➔
Low mass dark matter particles however might might play a
role in the decays of Y(1S), having Y(1S)→χχ if kinematic
allowed.
[Phys. Rev. D 80, 115019, 2009]
Also, new mediators (Z', A0, h0) or SUSY particles might
enhance Y(1S)→νν(γ).
[Phys. Rev. D 81, 054025, 2010]
e + e - →Y (3 S)
↓(4.4%)
Y (3 S)→ π+ π- Y (1 S)
↓
Y (1 S)→invisible
e + e - →Y (2 S )
↓(18.1%)
Y (2 S)→π + π- Y (1 S)
↓
Y (1 S)→invisible
Belle2 Simulation
Y(3S)→π+π-Y(1S),
Y(1S)→ νν
In absence of new physics enhancement, Belle2 should be
able to observe the SM Y(1S)→νν
A signal of Y(1S)→invisible is an excess of events
over the background in the Mr distribution at a mass
equivalent to that of the Y(1S) (9.460 GeV/c2)
2
r
M =s+ M π π −2 √ s E
+
-
CMS
+ π π
75
Invisible Y(1S) decays
[belle]: http://arxiv.org/abs/hep-ex/0611041
(1 week running @ Y(3S))
2.9 fb-1 @ Y(3S)
[babar]: http://arxiv.org/abs/0908.2840
(2 months running @ Y(3S))
28.5 fb-1 @ Y(3S)
76
Invisible Y(1S) decays
[belle]: http://arxiv.org/abs/hep-ex/0611041
(1 week running @ Y(3S))
2.9 fb-1 @ Y(3S)
[babar]: http://arxiv.org/abs/0908.2840
(2 months running @ Y(3S))
28.5 fb-1 @ Y(3S)
Irreducible peaking background when final states go undetected (i.e. detector supports,
beampipe etc.) in the process Y (3 S)→ π+ π- Y (1 S),Y (1S )→undetected f . s .
77
Invisible Y(1S) decays: background
Belle2 Simulation
Y(3S)→π+π-Y(1S),
Y(1S)→ μ μ (along the
beampipe, invisible)
[belle]: http://arxiv.org/abs/hep-ex/0611041
+ -
[babar]:
http://arxiv.org/abs/0908.2840
Irreducible peaking background when final states go undetected (i.e. detector supports,
beampipe etc.) in the process Y (3 S)→ π+ π- Y (1 S),Y (1S )→undetected f . s .
78
Invisible Y(1S) decays
[belle]: http://arxiv.org/abs/hep-ex/0611041
(1 week running @ Y(3S))
2.9 fb-1 @ Y(3S)
[babar]: http://arxiv.org/abs/0908.2840
(2 months running @ Y(3S))
28.5 fb-1 @ Y(3S)
No signal was observed over the expected background and upper limits have been
obtained: BR(Y→νν) < 3x10-4 (BaBar) and BR(Y→νν) < 3.0x10-3(Belle).
At Belle 2 one would expect to collect >200fb-1 of data @ Y(3S) (ongoing discussion for
Y(2S) data taking and trigger) allowing one to reconstruct between 30 and 300 events,
79
assuming 10-5 (SM)<BR(Y→invisible)< 10-4 (NP) and Belle efficiencies.
Invisible Y(1S) decays
2
4
27 G M Y (1 S)
BR (Y (1 S )→ν ν̄)
4 2 2
−4
=
(−1+
sin
θ
)
=4.14×10
W
3
BR(Y (1 S )→e + e - )
64 π2 α 2
BR (Y (1 S )→ν ν̄)∼9.9×10−6
➔
➔
➔
Low mass dark matter particles however might might play a
role in the decays of Y(1S), having Y(1S)→χχ if kinematic
allowed.
[Phys. Rev. D 80, 115019, 2009]
Also, new mediators (Z', A0, h0) or SUSY particles might
enhance Y(1S)→νν(γ).
[Phys. Rev. D 81, 054025, 2010]
e + e - →Y (3 S)
↓(4.4%)
Y (3 S)→ π+ π- Y (1 S)
↓
Y (1 S)→invisible
e + e - →Y (2 S )
↓(18.1%)
Y (2 S)→π + π- Y (1 S)
↓
Y (1 S)→invisible
Belle2 Simulation
Y(3S)→π+π-Y(1S),
Y(1S)→ νν
In absence of new physics enhancement, Belle2 should be
able to strongly constrain the SM Y(1S)→νν
No signal was observed over the expected background and upper
limits have been obtained: BR(Y→νν) < 3x10-4 (BaBar) and
BR(Y→νν) < 3.0x10-3(Belle).
If we collect >200fb-1 of data @ Y(3S) [Y(2S)] we should reconstruct
between 30 and 300 [~200 and ~2000] events , assuming
10-5 (SM)<BRY→invisible< 10-4 (NP) and εtot=10%.
80
Theory work is needed in order to
connect direct and indirect searches of
dark matter.
➔
➔
Shown here Y(1S) →γχχ vs. direct
searches.
Similar studies have performed also
for dark photon dark matter (see for
example J. Pradler et al.
arXiv:1412.8378)
Direct detection
DM: The Synergy Between Theory, Direct and Collider Searches
χ
SM
χ
SM
ArXiv:
1511.03728
1404.6599
Theory work is needed in order to
connect direct and indirect searches of
dark matter.
➔
➔
Shown here Y(1S) →γχχ vs. direct
searches.
Similar studies have performed also
for dark photon dark matter (see for
example J. Pradler et al.
arXiv:1412.8378)
Direct detection
DM: The Synergy Between Theory, Direct and Collider Searches
χ
SM
χ
SM
ArXiv:
1511.03728
1404.6599
DARKY(1S)
SECTOR
invisible
SEARCHES
decays:AT
signal
THE and
BELLE
background
2 EXPERIMENT
+ -
A '→l l
prompt/ displaced
J / ψ→invisible (+ γ)
*0
0
D →D A'
A ' →e + e -
Y (1 S )→invisible
DARK
SECTOR
Y (1 S )→invisible+ γ
B→invisible (+ γ)
A '→ χ χ
Y (3 S)→invisible + γ
83
Belle II Detector Elements
KL and muon detector:
Resistive Plate Counter (barrel outer layers)
Scintillator + WLSF + MPPC (end-caps ,
inner 2 barrel layers)
EM Calorimeter:
CsI(Tl), waveform sampling (barrel)
Pure CsI** + waveform sampling (end-caps)
Particle Identification
electrons (7GeV)
Time-of-Propagation counter (barrel)
Prox. focusing Aerogel RICH (fwd)
Beryllium beam pipe
2cm diameter
Vertex Detector
2 layers DEPFET + 4 layers DSSD
positrons
(4GeV)
Central Drift Chamber
He(50%):C2H6(50%), small cells, long
lever arm, fast electronics
84
Latest SUPER-KEKB Luminosity Profile
ab-1
Belle/KEKB recorded ~1000 fb-1 . Now
change units on y-axis to ab-1
cm-2s-1
year
Assumes full operation funding profile
85
Belle II Experiment Commissioning Timeline
2018
Full Belle II detector
os
ity
2017 (BEAST II)
Collision tuning starts w/ partial
Belle detector (no VXD)
2016 Autumn
Roll-in
Pe
ak
lu
m
in
February 2016 (BEAST I)
SuperKEKB beam commissioning
w/o collisions
Ongoing now very successfully
86
87