Strangelets from space

Jes Madsen University 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 –CurvatureA1/3 B = (145MeV)4 vs. (165MeV)4 CFL-strangelets

Madsen, PRL 87 (2001) 172003 Strangelets have low Z/A Heiselberg, PRD 48 (1993) 1418 [Ordinary strangelets]

Madsen, PRL 87 (2001) 172003 [CFL] 0.3A2/3 8A1/3 Nuclei 0.5A 0.1A Strangelet charge

• ”Ordinary” 2 1/3 Z = 8 m150 A (A>>1000) 2 Z = 0.1 m150 A (A<<1000) • Color-flavor locked 2/3 Z = 0.3 m150 A • 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 cluster mergers [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 interesting as 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 interesting as 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)=1020eV Stecker/Olinto (2000) Hillas-plot for E(max)=1020eV

Strangelet Z=104 Why are strangelets interesting as 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 A Low Z/A Eliminating the GZK-cutoff

a) Photo-pion production cut-off at γ π ≈ mπ / E2.7K 20 Ephoto-pion ≈ γ π Amp ≈ 10 eVA b) Photo-disintegration at γ dis ≈ 10MeV / E2.7K 19 Ephoto-dis ≈ γ dis Amp ≈ 10 eVA c) Photo-pair-production above γ pair ≈ 2me / E2.7K 18 Ephoto-pair ≈ γ pair Amp ≈ 10 eVA − dE / dt ∝ Z 2 A−1 small for low Z / A Measuring strangelets at 1-1000 GeV

Find low Z/A cosmic rays with high precision equipment in space => AMS-02

Alpha Magnetic Spectrometer AMS-02 International Space Station 2007—2010 (2012)

PURPOSE

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

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 if mass 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 flux Z=8, A=138 [CFL]

Flux (per [year GV sqm sterad]) Source

Interstellar

Solar System

Madsen (2004) PRELIMINARY

Rigidity (GV) Cosmic strangelet flux Z=8, A=138 [CFL]

Flux above R (per [year Interstellar sqm sterad]) Solar System

Source

Madsen (2004) PRELIMINARY

Rigidity (GV) Total CFL-strangelet flux Total flux (per [year sqm sterad]) No geomagnetic cutoff

Interstellar

Solar System

Madsen (2004) PRELIMINARY

Z Total CFL-strangelet flux

Total flux (per [year sqm sterad]) No geomagnetic cutoff

Interstellar

Solar System

Madsen (2004) PRELIMINARY

A 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