Puzzles of Dark Matter Searches

Lecture from course

“Introduction to Cosmoparticle Physics”Presented in University of Liege

Outlines

• Physical reasons for new stable quarks and/or leptons

• Exotic forms of composite dark matter, their cosmological evolution and effects

• Cosmic-ray and accelerator search for charged components of composite dark matter

• Conclusions

Dark Matter – Cosmological Reflection of Microworld Structure

Dark Matter should be present in the modern Universe, and thus is stable on cosmological scale.

This stabilty reflects some Conservation Law, which prohibits DM decay.

Following Noether’s theorem this cosnservation law should correspond to a (nearly) strict symmetry of microworld.

4

Direct search for DM (WIMPs)

CDM can consist of Weakly Interacting Massive Particles (WIMPs).Such particles can be searched by effects of WIMP-nucleus interactions.

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5

Direct search for DM (WIMPs)Minimization of background

• Installation deeply underground

• Radioactively pure materials

• Annual modulationDM does not participate in rotation around GC.

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Direct search for DM (WIMPs)

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DAMA/NaI (7 years) + DAMA/LIBRA (4 years) total exposure: 300555 kg×day = 0.82 ton×yr

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7

Direct search for DM (SIMPs)Rocket experiment XQC.

If DM consists of Strongly Interacting Massive Particles (SIMPs), they could be slowed down by ordinary matter and become insensitive for underground detectors.

Such particles could be searched for in X-cosmic ray experiment XQC, aimed at observation of X-rays and realized during a rocket flight.

XQC experimentdata taking time: ~100s,

material of detector: Si+HgTe,

energy deposit range of sensitivity: 25-1000 eV,

the range being good for extraction of SIMP-nucleus interactions event from background: 25-60 eV.

For scalar XA-interaction

8

Indirect Search for DM (cosmic positrons)

?

Most conservative predictions are used.

?

9

Indirect Search for DM (cosmicpositrons)

vnnn annXXsources σ~=&

Besides “natural” astrophysical origin, CR can originate from annihilationor/and decay of dark matter particles in halo of our Galaxy, or evaporation of PBH.

The excess of high energy positrons detected in experiment PAMELA may be considered as an evidence for indirect effect of dark matter, first predicted by Zeldovich et al (1980).

Dark Matter from Charged Particles?

2P l

P lmM mm

⎛ ⎞= ⎜ ⎟⎝ ⎠

• However, if charged particles are heavy, stable and bound within neutral « atomic » states they can play the role of composite Dark matter.

• Physical models, underlying such scenarios, their problems and nontrivial solutions as well as the possibilities for their test are the subject of the present talk.

By definition Dark Matter is non-luminous, while charged particles are the source of electromagnetic radiation. Therefore, neutral weakly interacting elementary particles are usually considered as Dark Matter candidates. If such neutral particles with mass m are stable, they freeze out in early Universe and form structure of inhomogeneities with the minimal characterstic scale

Components of composite dark matter:

• Tera-fermions E and U of S.L.Glashow’s

• Stable U-quark of 4-th family

• AC « leptons » from almost commutative geometry

• Technibaryons and technileptons from WalkingTechnicolor (WTC)

•Stable U-quarks of 5th family in the approach, unifying spins and charges, by N. Mankoc-Borstnik

Glashow’s tera-fermions

⎟⎟⎠

⎞⎜⎜⎝

⎛EN

⎟⎟⎠

⎞⎜⎜⎝

⎛DU

Very heavy and unstable

m~500 GeV, stable

m~3 TeV, (meta)stable

m~5 TeV, D U +…

SU(3)xSU(2)xSU(2)xU(1)

Tera-fermions (N,E,U,D) W’, Z’, H’, γ and g

106

+ problem of CP-violation in QCD + problem of neutrino mass+ (?) DM as [(UUU)EE] tera-helium (NO!)

6vevvev

UE D

e u d

mm m Sm m m

′= = = =

Cosmological tera-fermion asymmetry

( ) 0.224UUUEE CDMΩ ≡Ω =

0.044bΩ =

• To saturate the observed dark matter of the Universe Glashow assumed tera-U-quark and tera-electron excess generated in the early Universe.

• The model assumes tera-fermion asymmetry of the Universe, which should be generated together with the observed baryon (and lepton) asymmetry

However, this asymmetry can not suppress primordial antiparticles, as it is the case for antibaryons due to baryon asymmetry

(Ep) catalyzer

• In the expanding Universe no binding or annihilation is complete. Significant fraction of products of incomplete burning remains. In Sinister model they are: (UUU), (UUu), (Uud), [(UUU)E], [(UUu)E], [(Uud)E], as well as tera-positrons and tera-antibaryons

• Glashow’s hope was that at T<25keV all free E bind with protons and (Ep) « atom » plays the role of catalyzer, eliminating all these free species, in reactions like

( ) ( ) ( )( ) ( ) pEEEpE

pEEUUUEpEUUU+→+

+→+++

][][

But this hope can not be realized, since much earlier all the free E are trapped by He

« No go theorem » for -1 charge components

• If composite dark matter particles are « atoms », binding positive P and negative E charges, all the free primordial negative charges E bindwith He-4, as soon as helium is created in SBBN.

• Particles E with electric charge -1 form +1 ion [E He].

• This ion is a form of anomalous hydrogen.

• Its Coulomb barrier prevents effective binding of positively chargedparticles P with E. These positively charged particles, bound withelectrons, become atoms of anomalous istotopes

• Positively charged ion is not formed, if negatively charged particles E have electric charge -2.

4th family from heterotic string phenomenology

• 4th family can follow from heterotic string phenomenology as naturally as SUSY.• GUT group has rank (number of conserved quantities) 6, while SM, which it

must embed, has rank 4. This difference means that new conserved quantities can exist.

• Euler characterics of compact manifold (or orbifold) defines the number of fermion families. This number can be 3, but it also can be 4.

• The difference of the 4th family from the 3 known light generations can be explained by the new conserved quantity, which 4th generation fermions possess.

• If this new quantum number is strictly conserved, the lightest fermion of the 4th generation (4th neutrino, N) should be absolutely stable.

• The next-to-lightest fermion (which is assumed to be U-quark) can decay to N owing to GUT interaction and can have life time, exceeding the age of the Universe.

• If baryon asymmetry in 4th family has negative sign and the excess of anti-U quarks with charge -2/3 is generated in early Universe, composite dark matter from 4th generation can exist and dominate in large scale structure formation.

6E

4-th family

⎟⎟⎠

⎞⎜⎜⎝

⎛EN

⎟⎟⎠

⎞⎜⎜⎝

⎛DU

m~50 GeV, (quasi)stable

100 GeV <m<~1 TeV, E ->N lν,… unstable

220 GeV <m<~1 TeV, U -> N + light fermions Long-living wihout mixing with light generations

220 GeV <m<~1 TeV, D -> U lν,… unstable

Precision measurements of SM parameters admit existence of 4th family, if 4th neutrino has mass around 50 GeV and masses of E, U and D are near their experimental bounds.If U-quark has lifetime, exceeding the age of the Universe, and in the early Universe excess of anti-U quarks is generated, primordial U-matter in the form of ANti-U-Tripple-Ions of Unknown Matter (anutium).

( )UUU UUU−−Δ ≡ can become a -2 charge constituent of composite dark matter

4th neutrino with mass 50 GeV can not be dominant form of dark matter. But even its sparse dark matter component can help to resolve the puzzles of direct and indirect WIMP searches.

Stable neutrino of 4th generation

• For frozen out concentration of massive stable neutrinos decreases as

and reaches minimum at .

• Measurement of the Z-boson width constrains the mass of 4th neutrino by .

• For the allowed range of mass for 4th neutrino, it can not be the dominant form of DM.

MeVm 3>

3−∝ mnn γν2Zmm =

2Zmm >

Excluded Allowed

Condensation of heavy neutrinos in Galaxy

• Motion of collisionless gas in nonstationary field of baryonic matter, contracting owing to dissipation processes, provides effective dissipation and contraction of this gas.

• In result collisionless Dark Matter condences in Galaxy, but it is distributed more steeply, than baryonic matter.

• It gives qualitative explanation for formation of dark matter halo.

• Due to condensation effects of annihilation in Galaxy can be significant even for subdominant component as 4th neutrino.

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Dark matter

Stable neutrino of 4th generation and cosmic gamma background

• Annihilation in Galaxy of even small fraction of primordial 4th generation neutrinos with mass 50 GeV can provide explanation for the EGRET data from the center of Galaxy and from galactic halo.

Stable neutrino of 4th generation and cosmic ray positrons and antiprotons

• Annihilation in Galaxy of even small fraction of primordial 4th generation neutrinos with mass 50 GeV can provide explanation for the HEAT data on coamic postitrons and BESS data on cosmic antiprotons, as well as it can provide simultaneous explanation for positive and negative results of direct WIMP searches

( ) ( )4UUU He UUU He γ⎡ ⎤+ ⇒ +⎣ ⎦

But it goes only after He is formed at T ~100 keV

( ) 131/ 2 10o He HeR ZZ m cmα −= = ⋅

The size of O-helium is

2 2 2 1.6o He HeI Z Z m MeVαΔ= =

It catalyzes exponential suppression of all the remaining U-baryons with positive charge and causes new types of nuclear transformations

Dominant form of 4th generation darkmatter: O-helium formation

0IT <

O-Helium: alpha particle with zero charge

• O-helium looks like an alpha particle with shielded electric charge. It can closely approach nuclei due to the absence of a Coulomb barrier. For this reason, in the presence of O-helium, the character of SBBN processes can change drastically.

• This transformation can take place if

( ) ( ) ( ) ( ), 4, 2A Z UUU He A Z UUU⎡ ⎤+ → + + +⎣ ⎦

( ) ( ), 4, 2He oM A Z m I M A Z+ − > + +This condition is not valid for stable nuclids, participating in SBBN processes, but unstable tritium gives rise to a chain of O-helium catalyzed nuclear reactions towards heavy nuclides.

OHe catalysis of heavy element production in SBBN

OHe induced tree of transitions

After K-39 the chain of transformations starts to create unstable isotopes and gives rise to an extensive tree of transitions along the table of nuclides

Complicated set of problems

• Successive works by Pospelov (2006) and Kohri, Takayama (2006) revealed the uncertainties even in the roots of this tree.

• The « Bohr orbit » value is claimed as good approximation by Kohri, Takayama, while Pospelov offers reduced value for this binding energy. Then the tree, starting from D is possible.

• The self-consistent treatment assumes the framework, much more complicated, than in SBBN.

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10=⎟⎟⎠

⎞⎜⎜⎝

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O-helium warm dark matter

• Energy and momentum transfer from baryons to O-helium is not effective and O-helium gas decouples from plasma and radiation

• O-helium dark matter starts to dominate

• On scales, smaller than this scale composite nature of O-helium results in suppression of density fluctuations, making O-helium gas more close to warm dark matter

( ) 1b p on v m m tσ <

keVTT od 1=<

eVTRM 1=

Anutium component of cosmic rays

• Galactic cosmic rays destroy O-helium. This can lead to appearance of a free anutium component in cosmic rays.

Such flux can be accessible to PAMELA and AMS-02 experiments

( ) 7104−≤

HeUUU

Rigidity of Anutium component

Difference in rigidity provides discrimination of U-helium and nuclear component

O-helium in Earth

• In the reaction

( ) ( ) ( ) ( ), 4, 2A Z U U U H e A Z U U U⎡ ⎤+ → + + +⎣ ⎦

The final nucleus is formed in the excited [He, M(A, Z)] state, which can rapidly experience αlpha decay, giving rise to (OHe) regeneration and to effective quasi-elastic process of (OHe)-nucleus scattering.

If quasi-elastic channel dominates the in-falling flux sinks down the center of Earth and there should be no more than

235 10or−< ⋅

of anomalous isotopes around us, being below the experimental upper limits for elements with Z ≥ 2.

O-helium experimental search?

• In underground detectors, (OHe) “atoms” are slowed down to thermal energies far below the threshold for direct dark matter detection. However, (OHe) destruction can result in observable effects.

• O-helium gives rise to less than 0.1 of expected background events in XQC experiment, thus avoiding severe constraints on Strongly Interacting Massive Particles (SIMPs), obtained from the results of this experiment.

It implies development of specific strategy for direct experimental search for O-helium.

Superfluid He-3 search for O-helium

• Superfluid He-3 detectors are sensitive to energy release above 1 keV. If not slowed down in atmosphere O-helium from halo, falling down the Earth, causes energy release of 6 keV.

• Even a few g existing device in CRTBT-Grenoble can be sensitive and exclude heavy O-helium, leaving an allowed range of U-quark masses, accessible to search in cosmic rays and at LHC and Tevatron

OHe solution for puzzles of direct DM search

• OHe equilibrium concentration in the matter of DAMA detector is maintained for less than an hour

• The process

is possible, in which only a few keV energy is released. Other inelastic processes are suppressed

• Annual modulations in inelastic processes, induced by OHe in matter. No signal of WIMP-like recoil

• Signal in DAMA detector is not accompanied by processes with large energy release. This signal corresponds to a formation of anomalous isotopes with binding energy of few keV

( )[ ] γ+⇒+ ZAOHeZAOHe ,),(

Formation of OHe-nucleus bound system

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2α=

( )rmrggV A

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Due to exponential tail of nuclear Yukawa force OHe is attracted by nucleus. At the distance of order of the size of OHe Coulomb barrier is switched on. If He emits a photon, OHe forms a bound system with nucleus with binding energy of few KeV.

oA rR +

31

ARA ∝ AgA ∝ The depth of the well is maximal for A~10-20

γ

Few keV Level in OHe-nucleus system

• The problem is reduced to a quantum mechanical problem of finding energy level of OHe bound state in the spherically symmetric potential well, formed by Yukawa attraction and Coulomb barrier for He nucleus component of OHe in vicinity of a nucleus.

• We are close to obtain numerical solution for this problem.

O-helium Universe?

• The proposed scenario is the minimal for composite dark matter. It assumes only the existence of a heavy stable U-quark and of an anti-U excess generated in the early Universe to saturate the modern dark matter density. Most of its signatures are determined by the nontrivial application of known physics. It might be too simple and too pronounced to be real. With respect to nuclear transformations, O-helium looks like the “philosopher’s stone,” the alchemist’s dream. That might be the main reason why it cannot exist.

• However, its exciting properties put us in mind of Voltaire: “Se O-helium n’existai pas, il faudrai l’inventer.”

More Examples: AC-model

Mass of AC-leptons has « geometric origin ». Experimental constraint We take m=100GeV

Their charge is not fixed and is chosen +-2 from the above cosmological arguments. Their absolute stability can be protected by a strictly conserved new U(1) charge, which

they possess.In the early Universe formation of AC-atoms is inevitably accompanied by a fraction of

charged leptons, remaining free.

100A Cm m m GeV= = >

+ follows from unification of General Relativity and gauge symmetries on the basis of almost commutative (AC) geometry (Alain Connes)

+ DM (AC ) “atoms”

Extension of Standard model by two new doubly charged « leptons »

They are leptons, since they possess only γ and Z (and new, y-) interactions

2S

Form neutral atoms (AC, O-helium,….)-> composite dark matter candidates!

More Examples: WTC-model

The ideas of Technicolor are revived with the use of SU(2) group for “walking” (not running ) TC gauge constant. U and D techniquarks transform under the adjoint representation of an SU(2) technicolor gauge group. The chiral condensate of the techniquarks breaks the electroweak symmetry. There are nine Goldstone bosons emerging from the symmetry breaking. Three of them are eaten by the W and the Z bosons. The remaining six Goldstone bosons (UU, UD, DD and their corresponding antiparticles) are technibaryons and corresponding anti-technibaryons. The electric charges of UU, UD, and DD are given in general by y+1, y, and y-1 respectively, where y is an arbitrary real number.To cancel the Witten global anomaly model requires in addition the existence of a fourth family of leptons ( and ).

Charged techniparticles

• If y=1, and UU is the lightest it has charge +2, while its stable antiparticle has charge -2.

• In addition for y = 1, the electric charges of and are respectively -1 and -2.

• If TB is conserved, is main constituent of composite dark matter.

• If L’ is conserved, composite dark matter is provided by

• Their mixture if both the technilepton number L’ and are TB conserved.

Techniparticle excess

• The advantage of WTC framework is that it provides definite relationship between baryon asymmetry and techniparticle excess.

Here are statistical factors in equilibrium relationship between, TB, B, L and L’

The equilibrium is maintained by electroweak SU(2) sphalerons and similar relationship can hold true for any SU(2) dublets (like U quarks of 4th family or stable quarks of 5th family)

Relationship between TB and B

• L’=0, T*=150 GeV=0.1; 1; 4/3; 2; 3

• L’=0, T*=150, 200, 250 GeV

Relationship between TB, L’ and B

• x denotes the fraction of dark matter given by the technibaryon

• TB<0, L’>0 – two types of -2 charged techniparticles.

The case TB>0, L’>0 (TB<0, L’<0 ) gives an interesting possibility of (-2 +2) atom-like WIMPs, similar to AC model. For TB>L’ (TB<L’) no problem of free +2 charges

A WTC Universe?

• Even minimal, WTC model gives a wide variety of possibilities for composite dark matter scenario.

• It provides relationship between baryon asymmetry and dark matter.

• It makes possible nearly WDM (techni-O-helium) or mixed WDM+CDM scenarios

• Techni-O-helium is necessary (and even dominant) element of such scenarios

A solution for cosmic positron excess?

• If both antitechnibaryons and antitechnileptons are present, CDMS results constrain WIMP-like component to contribute no more than 1% of total DM density.

• Decays of positively charged with a lifetime of about and mass 300-400 GeV can explain the excess of cosmic positrons, observed by PAMELA

++ζ

( )UU

( )[ ]UU++ζ

++++ ⇒ lWζs2410

Invisble decay of Higgs boson H -> NN

Search for unstable quarks and leptons of new families are well elaborated.

Search for stable particles at LHC

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+0.6

GeV

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νe

)( +Λ U

)( 0/+M

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{ }0~uU

{ }−duU ~~~

{ }+dU~

{ }−dU~

{ }+sU~

{ }−sU~

{ } 0/~~~ −qsU

{ } 0/+Usq

{ }0~uU

8%

40%

40%

12%

~1%

Yields of U-hadrons in ATLAS

Possible signature of stable U hadrons Particle transformation during propagation through

the detector material

This signature is substantially different from that of R-hadrons

S. Helman, D. Milstead, M. Ramstedt, ATL-COM-PHYS-2005-065

Muon detector

ID&EC&HC

U-hadron does not change charge (+) after 1-3 nuclear interaction lengths (being in form of baryon)

U-hadron changes its charge (0 -) during propagation through the detectors (being in form of meson)

−− ↔ /0/0 ~~ MM

++ Λ→Λ UU++ Λ→ UM /0

−− →Λ /0~~ MU

,...~~ /0 π+→+Λ −− MNU

,...~~ /0/0 NMNM +↔+ −−

,...~ NNU ++Λ→ −

,.../0 NNMNU ++→+Λ ++

,.../0/0 NMNM +↔+ ++

,...π+Λ→ +U

{ }−sU~{ } { }+↔ UsuUsd 0

U-baryon will be converted into U-meson

U-mesons will experience inter-conversion

U-baryon will not be converted

U-mesons will experience inter-conversion and convert to U-baryon

Strange U-hadrons will get the form

and

suppressed

suppressed

“+” - 60%

“0” - 40%

“-” - 60%

“0” - 40%

LHC discovery potential for components of composite dark matter

• In the context of composite dark matter search for new (meta)stable quarks and leptons acquires the meaning of crucial test for its basic constituents

• The level of abscissa axis corresponds to the minimal level of LHC sensitivity during 1year of operation

Conclusions• New stable quarks and leptons can appear in extensions of Standard Model.

•Composite dark matter and its basic constituentsare not excluded either by experimental, or by cosmological arguments and are the challenge for cosmic ray and accelerator search

• Small fraction or even dominant part of composite dark matter can be in the form of O-helium, catalyzing new form of nuclear transformation

• The test for composite dark matter is possible in cosmoparticle physics analysis of its signatures and experimental search for stable charged particles in cosmic rays and at accelerators.