Heavy compact objects
flux limits from Pi of the Sky experiment
Lech Wiktor Piotrowski
RIKEN

2nd DIMS meeting
05.XII.2020

Lech Wiktor Piotrowski

The search for nuclearites

2nd DIMS Meeting

Heavy compact objects
Heavy Compact Objects - hypothetical extremely heavy (and dense) objects of(usually) extremely small size, for example:
Strangelets (microscopic?) / nuclearites (macroscopic?) – hypothetical lumps
of matter consisting of up, down and strange quarks, that could be more stablethat proton/neutron based hadronic matter
Could have been produced in very early universe
Maybe are produced in astrophysical objects (neutron/strange stars)
Rujula & Glashow, Nature, vol. 312, 1984
Could traverse through Solar System and Earth
Could produce light tracks in the atmosphere due adiabatic compression ofairAssumptions: cosmological origin, isotropic flux, “galactic speeds“ of 250km/s
Can be detected in similar manner as meteors

Lech Wiktor Piotrowski

The search for nuclearites

2nd DIMS Meeting

The Pi of the Sky experiment
Closed GRB optical follow-up project consisting of 16+2 cameras monitoring thesky.
FoV: 2 sr

Detection of flashes in the real time

Temporal resolution: ∼ 10s

Fully autonomous operation∼2000-3000 frames/night/camera

Range 12m - 14m

Large data stream: ∼ 0.5 TB/night

Finished operations in 2016
Lech Wiktor Piotrowski

The search for nuclearites

2nd DIMS Meeting90% CL limits on the flux of nuclearites

Flux [cm-2s-1sr-1]

Assumptions like in the paper: isotropic flux from upper hemisphere, 250 km/s
speed
101010101010− 15

10−410−310−210−11Mass [kg]21010− 16− 17− 18− 19− 20MACROMICA10− 2110− 22

SHM dark matter limit
Pi of the Sky

10231024102510261027281010
Mass [GeV/c2]

29L. W. Piotrowski et al., Phys. Rev. Lett. 125, 091101 – Published 28.08.2020
Lech Wiktor Piotrowski

The search for nuclearites

2nd DIMS Meeting

The road to the flux limit
Assuming no detection, 90% CL isotropic flux limit approximation:
Φ90CL (m) =2.3
SE (m) · te · 2π

where te is exposure time of a single frame,◦SE (m) =90XsFoV αm · αm · nα · εSα=0◦

is the detector’s effective area, sFoV αm is FoV surface, αm is detection efficiency
for given zenith angle and mass, nα is the number of frames taken with given
zenith angle, and εS is efficiency of separation from detected events (cuts to fulfil
no-detection).

Lech Wiktor Piotrowski

The search for nuclearites

2nd DIMS Meeting

Detection efficiency
Efficiency of strangelets detection– from simulation of strangelets
on Pi of the Sky sky photographs:
Simulate trimmed (minimalburning altitude) FoV
pyramid for range of masses
and zenith angles – surfaceof walls of the pyramid as
effective area of the detector
Calculate track position andbrightness on the frame:
altitude, distance to thedetector, atmospheric
extinction

Lech Wiktor Piotrowski

The search for nuclearites

2nd DIMS MeetingSeparation efficiency

How well the strangelet tracks can be distinguished from other tracks.
Find real events on the frame
Find cuts that will eliminate all of themFind how much of simulated strangelets the cuts cut

Lech Wiktor Piotrowski

The search for nuclearites

2nd DIMS MeetingData and events statistics
Search for track in archival Pi of the Sky
data:
Initially 337674 10 s frames, 34004
20*10 s summed frames
185258 10 s frames and 22237
20*10 s after frame quality cuts(clouds, tracking errors, horizon,
dusk, down, etc.) = 1766.05 h eq.
for single camera
35870 tracks in frames found by
OpenCV HoughLinesP basedalgorithm, after merging and cuts

Lech Wiktor Piotrowski

The search for nuclearites

2nd DIMS MeetingData and events statistics
Search for track in archival Pi of the Sky
data:
Initially 337674 10 s frames, 34004
20*10 s summed frames

2000

185258 10 s frames and 22237
20*10 s after frame quality cuts(clouds, tracking errors, horizon,dusk, down, etc.) = 1766.05 h eq.
for single camera

1400

35870 tracks in frames found by
OpenCV HoughLinesP basedalgorithm, after merging and cuts

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Automatic categorisation: 33257
satellites or meteors, 2613 others

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The search for nuclearites

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2nd DIMS MeetingData and events statistics
Search for track in archival Pi of the Sky
data:
Initially 337674 10 s frames, 34004
20*10 s summed frames
185258 10 s frames and 22237
20*10 s after frame quality cuts(clouds, tracking errors, horizon,dusk, down, etc.) = 1766.05 h eq.
for single camera
35870 tracks in frames found by
OpenCV HoughLinesP basedalgorithm, after merging and cuts
Automatic categorisation: 33257
satellites or meteors, 2613 others

200200600
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4020

Manual “others” categorisation: 1stiterations – 435 candidates, 2nditeration – 29 candidates

0− 20− 400

Lech Wiktor Piotrowski

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The search for nuclearites

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2nd DIMS MeetingData and events statistics
Search for track in archival Pi of the Sky
data:
Initially 337674 10 s frames, 34004
20*10 s summed frames
185258 10 s frames and 22237
20*10 s after frame quality cuts(clouds, tracking errors, horizon,dusk, down, etc.) = 1766.05 h eq.
for single camera
35870 tracks in frames found by
OpenCV HoughLinesP basedalgorithm, after merging and cuts
Automatic categorisation: 33257
satellites or meteors, 2613 others

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Y0806040
20Manual “others” categorisation: 1stiterations – 435 candidates, 2nd
iteration – 29 candidates
After cat. sat. cut: 20 candidates
Lech Wiktor Piotrowski

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The search for nuclearites

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2nd DIMS MeetingSeparation efficiency
The easiest, very drastic (but controversial) cut:simulation

104

real103102

10110− 1050010001500

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Track length [pixels]

Compatible with “maximum gap” method, but I could not find a good statisticalmethod for this cut.
Lech Wiktor Piotrowski

The search for nuclearites

2nd DIMS MeetingSeparation efficiency

Separation efficiency

The easiest, very drastic (but controversial) cut:
0.8Obs. zenith angle [deg]
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210Mass [kg]Compatible with “maximum gap” method, but I could not find a good statisticalmethod for this cut.
Lech Wiktor Piotrowski

The search for nuclearites

2nd DIMS Meeting

Longest candidate

Probably a satellite – flat start and flat top
0500

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∆Signal [ADU]

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Lech Wiktor Piotrowski

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The search for nuclearites

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Position [pixel]

2nd DIMS MeetingSeparation efficiency

Flux [cm-2s-1sr-1]

Removes all “candidates”, leaves above 50% for heavy masses

10101010101010− 1410−410−310−210−11

Mass [kg]21010− 15− 16− 17− 18− 19MACROSLIMANTARESMICA
SHM dark matter limit
Pi of the Sky− 2010− 2110− 22102310241025

10261027281010
Mass [GeV/c2]

29

SLIM and ANTARES limits removed in the paper – requested by reviewers.
Lech Wiktor Piotrowski

The search for nuclearites

2nd DIMS MeetingFlux [cm-2s-1sr-1]

The assumptions of the original paper
101010101010− 1510−410−310−210−11

Mass [kg]21010− 16− 17− 18− 19− 20MACROMICA10− 2110− 22

SHM dark matter limit
Pi of the Sky

10231024

1025

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1027281010Mass [GeV/c2]

29

Why isotropic shower of cosmological strangelets of speed 250 km/s?
“chaotic velocities characteristic of the Sun’s galactic rotation”
Due to the movement of Sun in the galaxy, direction would be highly
unisotropic
Non uniform, non-gaussian (?) speed distribution modulated by Earth’smovement, etc., somewhat similar to dark matter
Nuclearites have a mass spectrum!
Maybe not cosmological at all?
Extragalactic – most likely isotropic (short GRBs, etc.)
Gal. neutron stars, strange stars mergers/explosions, etc. – v? distribution?
Lech Wiktor Piotrowski

The search for nuclearites

2nd DIMS MeetingDirectional flux

Flux [cm-2s-1]

Perhaps more plausible ideas for cosmological strangelets:
A “sea” of immobile strangelets
A “dipol” of strangelets having all possible Keplerian orbits around the centreof the galaxy convolved with Sun’s/Earth’s movement
Some more complicated speed/direction distribution, like WIMPs isothermal
Mass [kg]sphere101010101010− 1110−410−310−210−1110102− 12− 13− 14− 15− 1610− 17101010− 18− 19− 2010231024102510261027281010
Mass [GeV/c2]

29A “sea” of immobile strangelets – a starting point for specific sources distribution
Lech Wiktor Piotrowski

The search for nuclearites

2nd DIMS MeetingEfficiency vs speed
Strangelets’ luminosity ∝ v 3)
Detection efficiency  ∝ v 2

Detection efficiency

Signal deposited in pixel ∝ t ∝ 1/v
10.8

Mass [kg]0.0001
0.01
1100

0.6

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050

Lech Wiktor Piotrowski

100150200250300350

The search for nuclearites

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Strangelet speed [km/s]
2nd DIMS MeetingBeyond nuclearites and dark matter
Heavy compact objects:
magnetised nuclearites – ∼ 1e9
mass shift – real constraints on DM
Q-balls – <1.5 ng SECS, > SENS
magnetic monopoles
fermionic exotic compact stars
primordial black holes...
...and their remnants
mirror matter
Fermi balls
electroweak symmetric dark matterballs
anti-quark nuggets

Almost all objects with mass spectrum

axion quark nuggets

Objects taken mainly from:
Burdin et al., Non-collider searches for stablemassive particles, Physics Reports 582, 2015

six-flavour quark matternon-strange quark matter*
Lech Wiktor Piotrowski

The search for nuclearites

2nd DIMS MeetingStrange events

Lech Wiktor Piotrowski

The search for nuclearites

2nd DIMS Meeting