Strangelets from space

Jes MadsenUniversity of Aarhus, Denmark

Strangelets from space

• What are strangelets ?• Why are they interesting as ultra-high

energy cosmic rays ?• Could a significant cosmic strangelet flux

exist and be measured ?• A strangelet search with the Alpha

Magnetic Spectrometer (AMS-02) on the International Space Station .

”Ordinary” strangelets• Witten; Farhi & Jaffe…• Madsen, PRD 50 (1994)

3328• B=(145 MeV)4

• ms=50,100,…300MeV• Shell-model vs. liquid

drop model – Bulk A– Surface tension A2/3

– Curvature A1/3

B = (145MeV)4 vs. (165MeV)4

CFL-strangelets

Madsen, PRL 87 (2001) 172003

Strangelets have low Z/A

8A1/3

0.1A

Heiselberg, PRD 48 (1993) 1418 [Ordinary strangelets]

0.3A2/3Madsen, PRL 87 (2001) 172003 [CFL]

Nuclei0.5A

Strangelet charge• ”Ordinary”

Z = 8 m1502 A1/3 (A>>1000)

Z = 0.1 m1502 A (A<<1000)

• Color-flavor lockedZ = 0.3 m150 A2/3

• Vacuum polarisation dominates at high A => lower Z[Madsen & Larsen, PRL 90

(2003) 121102]

Cronin, Gaisser & Swordy (1997)

Detection of UHECR’s(Anchordoqui et al. Int.J.Mod.Phys.A18 (2003) 2229

Is there a GZK-cutoff ?

Abbasi et al. (High Resolution Fly’s Eye Collaboration), PRL 92 (2004) 151101

Plausible sources for UHECR’s(Anchordoqui et al. Int.J.Mod.Phys.A18 (2003) 2229

• Supernovae explosions [147, 148].• Large scale Galactic wind termination shocks [149].• Pulsars (neutron stars) [150].• Active galactic nuclei (AGNs) [151].• BL Lacertae (BL Lac) – a sub-class of AGN [152, 153].• Spinning supermassive black holes associated with presently inactive quasar

remnants[154, 155]• Large scale motions and the related shock waves resulting from structure formation

in the Universe [157] such as accretion flow onto galaxy clusters and clustermergers [158, 159].

• Relativistic jets and “hot-spots” produced by powerful radiogalaxies. [161, 162, 163]. • The electrostatic polarization fields that arise in plasmoids produced in planetoid

impacts onto neutron star magnetospheres [166].• Magnetars – pulsars with dipole magnetic fields approaching ∼ 1015 G [167, 168,

169]– appear also as serious candidates [170, 171].• Starburst galaxies [172, 173, 174].• MHD winds of newly formed strongly magnetized neutron stars [175].• Gamma ray burst (GRB) fireballs [176, 177, 178, 179].• Strangelets, stable lumps of quark matter, accelerated in astrophysical environments

[180].• Hostile aliens with a big CR gun [181].

Why are strangelets interestingas ultra-high energy cosmic rays?

Madsen & Larsen, PRL 90 (2003) 121102

1. Avoids the acceleration problem of ordinary UHECR candidates

2. Avoids the GZK cut-off from interaction with 2.7K cosmic microwave background

Why are strangelets interestingas ultra-high energy cosmic rays?

Madsen & Larsen, PRL 90 (2003) 121102∝

1. ZSTRANGELET >> ZNUCLEUS possible⇓

Better acceleration in known sources (EMAX = RMAX Z; RMAX magn.field x size)

Rigidity R = p/Z (= E/Z if relativistic)

∝

Hillas-plot for E(max)=1020eVStecker/Olinto (2000)

Hillas-plot for E(max)=1020eV

StrangeletZ=104

Why are strangelets interestingas ultra-high energy cosmic rays?

Madsen & Larsen, PRL 90 (2003) 121102

2. Less susceptible to GZK-cut-off from high-Lorentz-factor interactions with 2.7K CMB-photons because of

High ALow Z/A

Eliminating the GZK-cutoff

AZAZdtdE /low for small / 12 −∝−

a) Photo-pion production cut-off at

b) Photo-disintegration at

c) Photo-pair-production above

AAmE p eV1020pion-photo ≈≈ πγ

KE 7.2dis /MeV10≈γ

KEm 7.2/ππγ ≈

Ke Em 7.2pair /2≈γ

AAmE p eV1019disdis-photo ≈≈ γ

AAmE p eV1018pairpair-photo ≈≈ γ

Measuring strangelets at 1-1000 GeV

Find low Z/A cosmic rays withhigh precision equipment in space

=>

AMS-02

Alpha Magnetic SpectrometerAMS-02

PURPOSE

•Cosmic rays•Antimatter (anti-He)•Dark matter•Strangelets

International Space Station 2007—2010 (2012)

Choutko (MIT)

Strangelets from strange star binary collisions

• 1 binary ”neutron star” collision per 10.000 years in our Galaxy

• Release of 10-6 solar masses per collision• Basic assumptions:

– SQM absolutely stable!– All mass released as strangelets with mass A

(fluxes for mass A give lower limit of flux ifmass spectrum of masses below A)

Strangelet propagation

• Acceleration in supernova shocks etc– Source-flux powerlaw in rigidity

• Diffusion in galactic magnetic field• Energy loss from ionization of interstellar

medium and pion production• Spallation from collision with nuclei• Escape from galaxy• Reacceleration from passing shocks

Cosmic strangelet fluxZ=8, A=138 [CFL]

Rigidity (GV)

Flux (per [year GV sqm sterad]) Source

Interstellar

Solar System

Madsen (2004) PRELIMINARY

Cosmic strangelet fluxZ=8, A=138 [CFL]

Flux above R(per [yearsqm sterad])

Rigidity (GV)

Source

Interstellar

Solar System

Madsen (2004) PRELIMINARY

Total CFL-strangelet fluxTotal flux(per [yearsqm sterad])

Z

Interstellar

Solar System

Madsen (2004) PRELIMINARY

No geomagnetic cutoff

Total CFL-strangelet fluxTotal flux(per [yearsqm sterad])

A

Interstellar

Solar System

Madsen (2004) PRELIMINARY

No geomagnetic cutoff

Conclusions

• Strangelets have low Z/A• CFL and non-CFL strangelets differ wrt. Z• Experimental verification/falsification of

– Strangelet existence• Realistic from AMS-02 [2007/8-2010]• Possible from lunar soil search experiment

[Sandweiss et al. (Yale); Fisher et al. (MIT); Madsen (Aarhus) 2004]

– (A,Z)-relation (CFL or ordinary)• Optimistic, but not impossible from AMS-02 or

perhaps lunar soil search