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Strangelets: Who is Looking (and how?)PowerPoint Presentation

Strangelets: Who is Looking (and how?)

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Strangelets: Who is Looking (and how?). Evan Finch Yale University March 29, 2006. Strangelets (Small Lumps of Strange Quark Matter). Roughly equal numbers of u,d,s quarks in a single ‘bag’ of cold hadronic matter.

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Strangelets (Small Lumps of Strange Quark Matter)

Roughly equal numbers of u,d,s quarks in a single ‘bag’ of cold hadronic matter.

That u,d, quark matter is not absolutely stable can be inferred by stability of normal nuclei-but this is not true for u,d,s quark matter.

Strangelet

A=12 (36 quarks)

Z/A = 0.083

Nucleus (12C)

Z=6, A=12

Z/A = 0.5

E. Finch-SQM 2006

Strangelets (Small Lumps of Strange Quark Matter)

Roughly equal numbers of u,d,s quarks in a single ‘bag’ of cold hadronic matter.

Stability can not be calculated in QCD, but is addressed in phenomenological models (MIT Bag Model, Color Flavor Locking…).

For a large part (~half) of available parameter space, these models predict that SQM is absolutely stable in bulk

Values of Bag Constant

J. Madsen, PRL 87 (2001)

Energy per baryon(MeV)

Stable SQM

Strange quark mass (MeV)

E. Finch-SQM 2006

Strangelets (Small Lumps of Strange Quark Matter)

Roughly equal numbers of u,d,s quarks in a single ‘bag’ of cold hadronic matter.

Bag model results with varying ms values

- SQM is less stable for lower baryon number (due curvature energy) for A<~1000
- There are likely significant shell effects at low A.

E/A (MeV)

A

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Strangelets (Small Lumps of Strange Quark Matter)

Roughly equal numbers of u,d,s quarks in a single ‘bag’ of cold hadronic matter.

Potential uses:

New chemistry with ‘nuclei’ (strangelets) up to Z~1000 (A~105)

Very dense matter available…

Terrific QCD laboratory

Strangelets can grow by absorbing neutrons – this is an exothermic reaction (~ 20 MeV photon emission)

New Energy Source

Shaw , Shin, Dalitz, Deasai, Nature, 337, (1989), 436

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Sources of Stable Strangelets?

Relics of Early Universe? (Dark Matter?)

Probably not…

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Sources of Stable Strangelets?

Strange Stars

If SQM in bulk is stable at zero pressure, all pulsars are likely to be strange stars. Collisions in binary systems would lead to a strangelet component of cosmic ray flux…

Experimental limits compiled by R. Klingenberg, SQM ‘00

Flux calculation From J. Madsen, PRD 71,014206

Large uncertainty due to unknowns in input parameters (number of strange star binary systems, fraction of mass ejected, propogation, etc.)

Calculated Flux (m2 yr sr)-1

Baryon Number

E. Finch-SQM 2006

Experimental limits (for given Z values)

Flux (m2 sr yr) -1

Flux predictions from Strange Star collisions

‘Interesting’ events

This level of flux relatively unconstrained experimentally

A

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How to find stable strangelets?

- “Best” way: measure cosmic ray spectrum with high precision spectrometer…AMS aboard the ISS

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How to find stable strangelets?

- “Best” way: measure cosmic ray spectrum with high precision spectrometer…AMS aboard the ISS

- Superconducting Dipole Magnet: BL2=0.86Tm2
- TOF: 4 layers, t=130ps. Measures Z<13.
- Silicon Strip Tracker: 8 double sided layers 8/30 m resolution. Measures Z<25.
- Also Rich, ECAL, TRD

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How to find stable strangelets?

- “Best” way: measure cosmic ray spectrum with high precision spectrometer…AMS aboard the ISS

R~1%

~10%

AMS measurements can easily tell strangelets from normal nuclei over huge energy range (=0.1 up to R=200GeV/c).

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How to find stable strangelets?

- “Best” way: measure cosmic ray spectrum with high precision spectrometer…AMS aboard the ISS

Flux (m2 sr yr) -1

1 event sensitivity in AMS-02

A

Baryon number

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How to find stable strangelets?

- “Best” way: measure cosmic ray spectrum with high precision spectrometer…AMS aboard the ISS

- AMS STATUS:
- AMS scheduled to be fully assembled in 2007 and to arrive at Kennedy Space Center in 2008.
- Then?
- Potential to have launch by vehicles other than shuttle
- Complicated question depending on the space program and ISS utilization

Unclear-depends on NASA decisions about shuttle and ISS programs.

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How to find stable strangelets?

Lunar Soil Search

Advantages over terrestrial search: Lunar surface undergoes very little geological mixing and moon has no magnetic fieldgain of ~104 in sensitivity over similar terrestrial search. See talk by Ke Han

Further motivation for search: 2 interesting events found in analysis of AMS-01 data. One was measured as Z=8, A=54±7 and is also too slow to be consistent with the geomagnetic cutoff. Would like to follow up on this event.

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How to find stable strangelets?

Lunar Soil Search

Method: use Yale WNSL tandem accelerator as Atomic Mass Spectrometer, and a combination of stopping foil and Silicon detectors to further suppress background.

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How to find stable strangelets?

Lunar Soil Search

Current status: have made 2 short ‘engineering’ runs, now working to improve transmission through machine

Flux (m2 sr yr) -1

Current Preliminary Limit

AMS-01 interesting event

Goal for Z= 8 (also sensitive to nearby charges)

A

Baryon number

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How to find stable strangelets?

Terrestrial searches (recent and upcoming)

Mueller et. al. (PRL 92, 022501,1994) searched for heavy isotopes of Helium at ~10-8 level using absorption spectroscopy.

Z=2

Flux (m2 sr yr) -1

They believe they can improve by several orders of magnitude. Techniques may also be useful for other elements.

A

Baryon number

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How to find stable strangelets?

Ongoing search by the SLIM experiment (mountaintop array of CR39 detectors) will be provide better sensitivity for SQM as Dark Matter

Terrestrial searches (recent and upcoming)

Flux (m2 sr yr) -1

May also be interpereted as relevant for Strange Star flux if strangelets are very penetrating.

A

See also poster by Xinhua Ma re:upcoming results using L3 cosmic ray triggered events.

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How to find stable strangelets?

Terrestrial searches (recent and upcoming)

- B. Monreal (MIT) is trying to systematically study what best possibilities are for finding terrestrial strangelets (nucl-ex/0506012) relevant to strange star production and has started trying to collect and concentrate various samples for AMS studies.
- Some hopeful possibilities are :
- Metals in stratosphere (concentrations potentially high, but large samples are hard to get)
- Searches among elements with no stable isotopes
- Technetium
- Radon

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How to find stable strangelets?

Terrestrial searches (recent and upcoming)

Seismic events (consistent with epilinear source interpreted as possible strangelet candidate) have been otherwise explained (PRD 73,043511,2006).

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Summary

- SQM stability is still an open question.
- The AMS detector (if launched) will significantly constrain the stability and production from Strange Star Collisions
- Terrestrial, lunar soil searches are active and ongoing and may approach the same level of sensitivity (although for a narrower range of parameter space).

E. Finch-SQM 2006

Sources of Stable Strangelets?

Relics of Early Universe? (Dark Matter?)

Probably not

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Strangelets (Small Lumps of Strange Quark Matter)

Roughly equal numbers of u,d,s quarks in a single ‘bag’ of cold hadronic matter.

Stability can not be calculated in QCD, but is addressed in phenomenological models (MIT Bag Model, Color Flavor Locking…).

For a large part (~half) of available parameter space, these models predict that SQM is absolutely stable in bulk

Energy per baryon number

J. Madsen, hep-ph/9809032

E. Finch-SQM 2006

MIT Bag Model Calculations (Fahri and Jaffe)

For the set of parameters chosen for this plot, strangelets become more stable then normal nuclear matter for A>100.

E/A for nuclear matter

E. Finch-SQM 2006

Potential of Stable Strangelets

New chemistry with ‘nuclei’ (strangelets) up to Z~1000

Very dense matter available…

Terrific QCD laboratory

Strangelets can grow by absorbing neutrons – this is an exothermic reaction (~ 20 MeV photon emission)

New Energy Source

Shaw , Shin, Dalitz, Deasai, Nature, 337, (1989), 436

Strangelets with A>1017 (R> 5 Angtroms) cannot be supported in the surface of the earth (mg ~ 1 eV/angstrom)

Strangelets with M > 2*Msunwill collapse into a blackhole.

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Experiments

- Skylab, TREK: Satellite based Lexan. No events Z>100
- ARIEL-6, HEAO-3. scintillators, cerenkov counters. No events Z>100
- HECRO-81:Saito et al. scintillator, Cerenkov in balloon at 9gm/cm2. 2 Z=14 undercutoff events. A of 110(370) to be above cutoff(mean rigidity). E/A~.45 GeV
- ET event Ichimura et. Al. emulstion chamber in balloon at few g/cm2 but trajectory would have taken it through ~200gm/cm2. Z~30. A measured at 460
- Price monopole. Lexan and emulsions in balloon experiment. Constant ionization through Lexan and low number of delta rays for normal nucleus. One interperetation is Z=45 and mass of 1000-10000
- Centauro (original)
- SLIM: mountaintop Lexan CR detector
- Fossil Tracks (in meteorites)
- Mica: look for tracks traversing 10**7 g/cm2
- Mountaintop. Look for tracks traversing ~600 g/cm2
- Sea Level:tracks traversing 10**3 g/cm2
- Underground: tracks traversing 10**4 g/cm2
- Centauro:1000Tev shower at 500g/cm2, mass~200. Small em component (decay into strange baryons?) and very penetrating (SQM glob which isn’t destroyed by nuclear interactions?)

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Some AMS details…

- AMS Magnet (ETH-Zurich) superconductor NbTi stabilized by Cu, Al. Cooled by superfluid He connected by thermal bus bar.
- TRD (MIT): fleece radiator, straw tube detector with Xe:CO2 gas
- Tracker(INFN Perugia) Si sensors ~7x4 cm with pitch 27,100u. 8 planes (1-2-2-2-1) w/ laser alignment
- TOF(INFN Bologna)8-8-8-10 scintillator slats (2 planes top,2 bottom)
- RICH(INFN Bologna) Aerogel radiator, 680 multianode(4x4) phototubes. Resolution 0.1%
- ECAL(INFN-Pisa) Lead-scintillator 648x648x166mm. 9 Superlayers alternate directions of fibers. PMT covers 9x9mm

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Color-flavor locked strangelets (J. Madsen)

Predicts CFL strangelets have lower E/A than ‘normal’ strangelets, giving a charge/mass relation of Z~0.3A2/3

(“normal” bag model strangelets have Z~.1A for A<<1000

Z~8A1/3 for A>>1000

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AMS-01

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AMS-01

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AMS-01

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R/bg vs bg for Z>2for (top) undercutoff and (bottom) overcutoff

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International Participation in AMS

FINLAND

RUSSIA

HELSINKI UNIV.

UNIV. OF TURKU

I.K.I.

ITEP

KURCHATOV INST.

MOSCOW STATE UNIV.

DENMARK

UNIV. OF AARHUS

NETHERLANDS

GERMANY

ESA-ESTEC

NIKHEF

NLR

RWTH-I

RWTH-III

MAX-PLANK INST.

UNIV. OF KARLSRUHE

KOREA

USA

EWHA

KYUNGPOOK NAT.UNIV.

A&M FLORIDA UNIV.

JOHNS HOPKINS UNIV.

MIT - CAMBRIDGE

NASA GODDARD SPACE FLIGHT CENTER

NASA JOHNSON SPACE CENTER

UNIV. OF MARYLAND-DEPRT OF PHYSICS

UNIV. OF MARYLAND-E.W.S. S.CENTER

YALE UNIV. - NEW HAVEN

FRANCE

ROMANIA

CHINA

BISEE (Beijing)

IEE (Beijing)

IHEP (Beijing)

SJTU (Shanghai)

SEU (Nanjing)

SYSU (Guangzhou)

SDU (Jinan)

GAM MONTPELLIER

LAPP ANNECY

LPSC GRENOBLE

ISS

UNIV. OF BUCHAREST

SWITZERLAND

ETH-ZURICH

UNIV. OF GENEVA

TAIWAN

SPAIN

CIEMAT - MADRID

I.A.C. CANARIAS.

ITALY

ACAD. SINICA (Taiwan)

CSIST (Taiwan)

NCU (Chung Li)

NCKU (Tainan)

NCTU (Hsinchu)

NSPO (Hsinchu)

ASI

CARSO TRIESTE

IROE FLORENCE

INFN & UNIV. OF BOLOGNA

INFN & UNIV. OF MILANO

INFN & UNIV. OF PERUGIA

INFN & UNIV. OF PISA

INFN & UNIV. OF ROMA

INFN & UNIV. OF SIENA

MEXICO

UNAM

PORTUGAL

LAB. OF INSTRUM. LISBON

16 Countries, 56 Institutes, 500 Physicists

~ 95% of AMS is constructed in Europe and Asia

Supported by ministries of science/education/energy,

space agencies, local goverments and universities

Y96673-05_1Commitment

Strange Quark Matter

The existence of hadronic states with more than three quarks is allowed in QCD. The stability of such quark matter has been studied with lattice QCD and phenomenological bag models, but is not well constrained by theory.

Quark Matter

Strange Quark Matter

Energy Level

Strange Quark Mass

There is additional stability from reduced Coulomb repulsion. SQM is expected to have low Z/A

The addition of strange quarks to the system allows the quarks to be in lower energy states despite the additional mass penalty.

E. Finch-SQM 2006

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