1 July 19, 2006M. Woods, SLAC (S. Boogert, RHUL) Collimator design, wakefields (T-480) BPM.
Dark Matter Models - PPD · PDF fileDark Matter Models Stephen West Fellow\Lecturer RHUL and...
Transcript of Dark Matter Models - PPD · PDF fileDark Matter Models Stephen West Fellow\Lecturer RHUL and...
Dark Matter Models
Stephen West
Fellow\Lecturer
RHUL and RAL
and
Introduction
‣ Research Interests‣ Important Experiments
Dark Matter - explaining PAMELA and ATIC‣ Some models to explain data‣ Freeze out‣ Sommerfeld effect
Summary
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Outline
Research Interests
‣ BSM model building‣ Supersymmetry‣ Higgs Physics‣ Neutrino Physics‣ Flavour Physics‣ Extra Dimensions‣ Early Universe Cosmology
✴ Baryogenesis/Leptogenesis
✴ BBN
✴ Dark Matter
Dark matter
‣ At the LHC
‣ Astrophysics Experiments
Evidence for Dark matter:
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Dark Matter
• Cosmological Scales: CMB power spectrum...WMAP
• Galactic Scales: Rotation Curves, expect velocity of stars v(r) ∝ 1/√r but measure flat rotation curves
• Galaxy Cluster Scales: Bullet cluster, other cluster dynamics
!h2dm = 0.1143± 0.0034!
‣ PAMELA ( )‣ ATIC ( )‣ Hess ( )‣ + many more‣ CDMS‣ Zeplin‣ DAMA‣ + many more
Current Data:
Future Data:
Indirect Detection
DirectDetection
}}
!
e±, p±
!!
‣ FERMI/GLAST ( )‣ Icecube ( )‣ LHC?...
e±, p±
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Important Experiments
GCRs high-energy particles flowing into our solar system from far away in the Galaxy.
!
‣ Composition: protons
electronshelium
+ other heavier nuclei
! 90%! 9%
‣ Origins: ✴ Probably accelerated in the blast waves of supernova remnants (SNRs)
✴ Particles/Nuclei bouncing back and forth in magnetic field of the remnants
✴ Some gain enough energy to escape into Galaxy and become GCRs
Galactic Cosmic Rays(GCRs)
! 1%
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‣ Some GCRs observed with energies above max possible energies produced by SNRs
More GCRs
‣ Origins? ✴ Sources outside the Galaxy
✴ Quasars/Pulsars
✴ Exotic new physics: E.G. Dark Matter...
Observed range 1! 1, 000, 000 GeV/n
compared to ESNRmax ! 10, 000 GeV/n
✴ gamma ray bursts
‣ Some cosmic rays are observed above expected rates...
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Payload for Antimatter Matter Exploration and Light nuclei Astrophysics
PAMELA
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neutrondetector
anti-coinci-dence
ma
gn
et
B
X
ZY
proton antiproton
scint. S4
calorimeter~16.3 X
~0.60
Il
trackingsystem
(6 planes)
geometricacceptance
CAT
CAS
CARD
spectrometer
TOF (S1)
TOF (S2)
TOF (S3)
‣ Satellite experiment launched in 2006
‣ Primary goal: measure antimatter component of cosmic rays.
‣ Able to identify positively and negatively charged particles
Payload for Antimatter Matter Exploration and Light nuclei Astrophysics
‣ Measure spectra of antiprotons and positrons
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PAMELA
PAMELA Results:Anti-Proton fraction
PAMELA Collaboration (O. Adriani et al.), Phys.Rev.Lett.102:051101,2009.
kinetic energy (GeV)1 10
210
/pp
-410
-310
IMAX 1992
BESS 2000 HEAT-pbar 2000
CAPRICE 1998
CAPRICE 1994 BESS-polar 2004
MASS 1991
BESS 1995-97
BESS 1999
PAMELA
kinetic energy (GeV)1 10
210
/pp
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4-3
10!
=500MV) !Donato 2001 (D,
=500MV) !Simon 1998 (LBM,
=550MV) !Ptuskin 2006 (PD,
PAMELA
Energy (GeV)
1 10 100
))
-(e!
)+
+(e!
) / (
+(e!
Po
sit
ron
fra
cti
on
0.01
0.02
0.1
0.2
0.3
PAMELA
Energy (GeV)
0.1 1 10 100
))
-(e!
)+
+(e!
) / (
+(e!
Po
sit
ron
fra
cti
on
0.01
0.02
0.1
0.2
0.3
0.4
Muller & Tang 1987
MASS 1989
TS93
HEAT94+95
CAPRICE94
AMS98
HEAT00
Clem & Evenson 2007
PAMELA
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PAMELA Results:Positron fraction
PAMELA Collaboration (O. Adriani et al.), arXiv:0810.4995 [astro-ph]
Advanced Thin Ionization Calorimeter
‣ Balloon experiment collecting data in 2000, 2003 and 2007
‣ Cannot distinguish between and e+e!
‣ Measures total electronic flux ( )in energy range 20-2400 GeV
e! e++
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‣ Also detects protons and heavier nuclei
Striking Results...
ATIC
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ATIC resultsATIC Collaboration (J. Chang et al.), Nature 456:362-365,2008.
Expected energy dependence of background Excess corresponds to 70 out of 210 total
AMS (green stars)
HEAT (open black triangles)
Emulsion chambers (black open diamonds)
BETS (open blue circles)
PPB-BETS (blue crosses)
AMS and HEAT are satellite experimentsBETS and PPB-BETS are balloon experiments
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Explaining the rise...
‣ Nearby astrophysical objects e.g. Pulsars
‣ Dark Matter
arXiv:0804.0220 See e.g.arXiv:0812.4457arXiv:0810.1527 Hooper et al.
Büsching et al.
Profumo
Seems possible to explain PAMELA and ATIC with pulsars
✴ Annihilations✴ Decays ! ! 1026sDM
DM
SM
SMDM
SM
SM
Many refs for dark matter, see e.g. Ref list in
Profumo arXiv:0812.4457
Decaying dark matter
‣ Candidates:
Lifetime ! ! ! 1026s
Decays have restricted branching fractions:
BHAD < 0.1
✴ Gravitino
✴ “Hidden sector” particle
✴ Maybe others...✴ Composite particles
Several ideas along these lines in literature
Annihilating dark matter
1) Annihilations rates must be large to account for large PAMELA and ATIC signals need boosts
✴ A problem for standard thermal dark matter
2) Annihilations must not produce too many hadrons
✴ Annihilation products usually include both hadrons and lepton
3) Annihilations must not produce too many photons
✴ Strong limits exist on photon signals
✴ Photons produced at wide range of frequencies for charged decay products
problem for standard thermal dark matter
Particle in thermal eq. present abundance:
neq ! (m/T )3/2e!m/T
However, if species freezes out i.e. ! < H
at temp T such that m/T ! 25
Can have significant relic abundance today
!
Using Boltzmann equations we get
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1) Annihilations rates must be large-
Kolb & Turner, `90
!dmh2 ! O(10!27 " 10!28)#!v$ GeV !2
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But we know that !dmh2 = 0.1143± 0.0034
This is weak scale interaction with weak scale mass particle
! WIMPThis fixes !!v"
sets the size of annihilations of DM particles as a function of DM velocity
!
!! A way out !! Change how !!v" depends on velocity
!dmh2 ! O(10!27 " 10!28)#!v$ GeV !2
! "!v# = (10!26 $ 10!27)GeV !2
Normally
The Sommerfeld Effect
‣ Heavy DM moving at small (relative) velocity
‣ Exchange of scalar (or vector) state
enhancement in annihilation cross section
(Sommerfeld; Hisano et al, Strumia et al...)
‣Corresponds to summation of
diagrams Only significant for s-wave
! (AM barrier)
!v = a + bv2
!
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!v ! 1vr
DM
DM
March-Russell, West, Cumberbatch, Hooper.
The Sommerfeld Effect‣ Calculation formed in terms on non-rel two body
QM problem with a potential
‣ Equivalent to distorted Born-wave approximation common in nuclear physics.
‣ Including the effect (to a good approximation)
! = R!l=0tree
‣ Full calculation of R can be involved
‣ For a Yukawa potential R cannot be solved analytically
‣ Can be enhancement or suppression for vector exchange
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Calculating R
‣ Scalar “rungs on the ladder”states can be then
‣ The Schrödinger equation for two DM particle state
‣ Enhancement factor R = |!(0)/!(!)|2
‣ Outgoing B.C
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! 1mdm
d2!
dr2+ V ! = K! K = mdmv2V = ! !2
8"re!mn
‣ Introduce the following term!
2n"dm"dm
! ! !dm!dm
!!(!)/!(!) = imdmv
Coulomb limit‣ Analytic form for R in limit
‣ Small limit
What about ?! != 0
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y = !2/4vR =y
1! e!y
v
R ! !2
4v
! ! mn/mdm = 0
!1 0 1 2 3 4 5 6
0.0
0.5
1.0
1.5
2.0
Log!""##
Log!""$#
Contours in R
! ! 0.2
3 10 30 1003001000
Enhancement for ! != 0
Freeze out
!! FO
FO
!/" > 1!/" > 1
Need
Indirect detection
! ! 10!3 " 10!5
!ID
ID ID23
! ! mn/mdm
! = "2/8#
! ! 2
0
2
4
6
0.0
0.5
1.0
1.5
0
500
1000
3D Version
R
Log[!/"]
Log[!/"]
500
1000
0
0
0.5
1.51.0
2
4
6
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March-Russell, West.
1) Annihilations rates must be large -Alternatives
‣ Could consider non-thermal dark matter
✴ Late decaying particles
✴ Another interesting idea later
‣ Over densities - No. annihilation
✴ Regions of high density
✴ Near Black Holes?
✴ Naturally occurring clumps?
! !2dm
2) Annihilations must not produce too many hadrons
‣ Leptophilic models
✴ Need to introduce extra quantum numbers
✴ Can introduce two dark matter states and have inelastic scattering
‣ Kinematic tricks and extra symmetries
✴ dark matter only talks to leptons due to symmetries
DM
DM
!µ, e
µ, e
! possible to reconcile DAMA with other direct detection experiments
✴ Particle can generate Sommerfeld enhancement
!
(Arkani-Hamed et al...)
Fox, Poppitz, arXiv:0811.0399
3) Annihilations must not produce too many photons
‣ All annihilations with charged states can produce photons
✴ Boosting annihilation rates into means we produce more photons
e±
✴ Measurements of Cosmic diffuse background radiation tightly constrain scenarios
Summry‣ PAMELA and ATIC inspired a lot of model building
‣ If DM is the answer, need large boosts to annihilation cross sections
‣ Several ways to generate boost factors but all have restrictions and constraints
‣ PAMELA and ATIC data have inspired a lot of unusual and compelling new ideas - many more to come...
‣ Maybe explained by astrophysics
✴ Exciting times ahead