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Astroparticle Physics at the
Royal Institute of Technology
Presented by Felix Ryde
Faculty:
Professor Mark Pearce
Docent Felix Ryde
Post Doc:
Announcement for GLAST (see www.particle.kth.se/astro)
Graduate Students:
Cecilia Marini Bettolo (PoGOLite)
Petter Hofverberg (PAMELA)
Mózsi Kiss (PoGOLite)
Laura Rossetto (PAMELA)
Juan Wu (PAMELA)
Astroparticle Physics at KTH
• Research on the high-energy Universe through the study of X- and
gamma-radiation and cosmic rays. The group has actively participated in
experiments measuring different aspects of the cosmic radiation for more
than a decade.
• The fundamental scientific questions addressed concern particle acceleration
and radiation processes in cosmic plasmas, in the galaxy and around compact
objects, and the understanding of dark matter and gamma-ray bursts.
• The focus is on design and development of strategic satellite- and balloonborne instrumentation, and on the analysis and astrophysical interpretation
of the data obtained with these instruments.
Astroparticle Physics at KTH
•PAMELA: Payload for Antimatter Matter Exploration and
Light-nuclei Astrophysics.
•PoGOLite: Polarised Gamma-ray Observer.
•GLAST: Gamma-ray Larger Area Telescope
•Outreach: (SEASA)
• PAMELA
Payload for
Antimatter/Matter
Exploration and
Light-nuclei
Astrophysics
Precision study of charged particles in the cosmic radiation
(antiprotons and positrons)
• Search for dark matter
• Search for antihelium (primoridal antimatter)
• Study of cosmic-ray propagation (light nuclei
and isotopes)
• Study of electron spectrum (local sources?)
• Study solar physics and solar modulation
• Study terrestrial magnetosphere
EM shower containment
Magnetic curvature
(trigger)
‘Spillover’
Design performance
•
Energy range
Maximum
Detectable Rigidity
(MDR)
Particles/3 years
>3x104
•
Antiproton flux
80 MeV - 190 GeV
•
•
•
•
•
•
Positron flux
Electron flux
Proton flux
Electron/positron flux
Light nuclei (up to Z=6)
Antinuclei search
50 MeV – 270 GeV
>3x105
up to 400 GeV
6x106
up to 700 GeV
3x108
up to 2 TeV (from calorimeter)
up to 200 GeV/n He/Be/C:
4 107/4/5
-8
Sensitivity of 3x10 in He-bar/He

Unprecedented statistics and new energy range for cosmic ray physics
 e.g. contemporary antiproton & positron energy, Emax  40 GeV

Simultaneous measurements of many species – constrains secondary production models
1 HEAT-PBAR flight ~ 22.4 days PAMELA data
1 CAPRICE98 flight ~ 3.9 days PAMELA data
PAMELA milestones
• Launch from Baikonur: June 15th 2006, 0800 UTC.
• ‘First light’: June 21st 2006, 0300 UTC.
• Detectors operated as expected after launch
• Different trigger and hardware configurations evaluated
• PAMELA in continuous data-taking mode since
commissioning phase ended on July 11th 2006
• As of ~now:
– > 300 days of data taking (70% live-time)
– ~5.5 TByte of raw data downlinked
– ~610 million triggers recorded and under analysis
-
e-
p
e+ p (He...)
Trigger,
ToF, dE/dx
Anticoincidence
system reduces
background.
+
NB:
e+/p: 103 (1 GeV) → 5.103 (10 GeV)
p’/e-: 5.103 (1 GeV) → <102 (10 GeV)
-
Sign of
charge,
rigidity,
dE/dx
Electron energy,
dE/dx, leptonhadron separation
Signal (SUSY)…
… background
pCR  pISM  p  p  p  p
pCR  pISM     X ;         ;    e    e   
pCR  pISM   0  X ;  0     ;   e   e 
CAPRICE balloon experiment, 1998
AMS-01: space shuttle, 1998
Antiprotons
PAMELA
Secondary
production (upper
and lower limits)
Simon et al. ApJ 499
(1998) 250.
Primary production
from cc annhilation
(m(c) = 964 GeV)
Ullio : astro-ph/9904086
Secondary
production ‘C94
model’ + primary
cc distortion
Secondary
production
(CAPRICE94-based)
Bergström et al. ApJ
526 (1999) 215
Galactic p and He spectra
Z=1
Z=2
~2.76
~2.71
PoGOLite - polarization of soft gamma-rays
DAQ system
• Dimensioned for long duration flights
• No HV supply lines
• Flash ADC recording of all non-zero
waveforms
• Memory stick storage
Attitude control
• Design adapted from HEFT.
• Goal: 5% of F.O.V. = ~0.1 degrees
• 2 star cameras, DGPS, 2 gyroscopes, 2
magnetometers, accelerometer. Axial and
elevation flywheels.
• Star cameras are primary aspect sensors.
Acquires 8th mag. stars in daylight at 40 km.
Measuring polarisation
• Incident  deposits little
energy at Compton site
• ‘Large’ energy deposited
at photoelectric absorption
site
•  from a polarised source
undergo Compton
scattering in a suitable
detector material
•  large energy difference
• Can be distinguished by
simple plastic scintillators
(despite poor intrinsic energy
resolution)
• Higher probability of being
scattered perpendicular
to the electric field vector
(polarisation direction)
Array of plastic
scintillators
• Observed azimuthal
scattering angles are
therefore modulated by
polarisation
Photoelectri
c absorption

E
Compto
n scatter
Well-type phoswich detector
A narrow field-of-view and low background instrument
Valid event
•
•
•
Pink: Phoswich Detector Cells (total
217units)
Orange: Side Anti-counter Shield (total 54
BGO)
Yellow: Neutron Shield (polyethylene)
140
cm
Phoswich Detector Cell
PoGOLite polarimeter – schematic
60 cm
100 cm
P o G OLite

SLAC / Stanford- KIPAC
KTH, Stockholm
University
E , t , rˆ, Pˆ
Tokyo Institute of Technology,
Hiroshima University, ISAS/JAXA,
Yamagata University.
[25 – 80 keV]
E , t , rˆ
e.g. G L A S T

• Gamma- / X-rays can be characterised by their energy,
direction, time of detection and polarisation
• Polarisation only measured once (OSO-8, 2.6 & 5.2
keV,1976)
• Measuring the polarisation of gamma-rays provides a
powerful diagnostic for source emission mechanisms
• Polarisation can occur through scattering / synchrotron
processes, interactions with a strong magnetic field
[10 keV – 300 GeV]
 sensitive to the ‘history’ of the photon
Polarisation in soft -ray emission
 Synchrotron emission:
 Rotation-powered neutron stars (eg. the Crab pulsar)
 Pulsar wind nebulae (eg. the Crab nebula)
 Jets in active galactic nuclei
 Compton scattering:
 Accreting disk around black holes (eg. Cygnus X-1)
 Propagation in strong magnetic field:
 Highly magnetised neutron stars
Expected polarization is a few % - ~20%
→ Need a very sensitive polarimeter
PoGOLite is optimised for point-like sources
covers 25-80 keV range and
detects 10% pol in 200 mCrab sources
in a 6 hour balloon observation
- PoGOLite 6h flight:
+Crab: distinguish between emission model
Polar Cap, Outer Gap Caustic Models
+Cyg X-1: reflection component in hard stat
- Long duration flight
+ Her X-1: cyclotron absorption lines.
Engineering flight: 2009 / Science flight: 2010
Primary Northern-sky targets (6h)
• Proposed location: NASA Columbia
Scientific Balloon Facility, Palestine,
Texas
• Nominal ~6 hour long maiden flight
• Total payload weight ~1000 kg
• 1.11x106 m3 balloon
• Target altitude ~40 km
Accreting X-ray pulsar
• Engineering flight from Sweden
planned for 2009. Long duration Sweden
to Canada
High-mass
X-ray also proposed.
binary
Pulsar / SNR
GLAST - Large Area Space Telescope
Gamma-ray Large
Area Space
Telescope

France

IN2P3, CEA/Saclay

Italy

Universities and INFN of Bari, Perugia, Pisa,

Roma Tor Vergata, Trieste, ASI, INAF

Japan

Hiroshima University, ISAS, RIKEN

United States

CSU Sonoma. UC Santa Cruz, Goddard, NRL, OSU,

Stanford (SLAC and HEPL), Washington, St. Louis

Sweden

Royal Institute of Technology (KTH), Stockholm University,

Kalmar University
Principal Investigator:
Peter Michelson (Stanford & SLAC)
~270 Members
(includes ~90 Affiliated Scientists,37 Postdocs,
and 48 Graduate Students)
GLAST Key Features
Large Area
Telescope (LAT)
Imaging gamma-ray telescope
Two GLAST instruments:
LAT (Large Area Telescope): 20 MeV – >300 GeV
GBM (GLAST Burst Monitor) 10 keV – 25 MeV
Launch: February, 2008.
5-year mission (10-year goal)
•
•
•
•
•
•
Large area
Large field of view
Large energy range
Sub-arcmin source localization
Superior deadtime
Energy resolution @ 10 GeV < 6 %.
GBM
GLAST Sensitivity
GLAST Burst Monitor (GBM):
Large Area Telescope (LAT):
10 keV – 25 MeV
20 MeV – 300 GeV
Launch: early 2008
•30 times better sensitivity
(5x for GRBs)
•Good localization 30’’- 5’
(FOV 2-3 sr)
•Good energy resolution ~10%
• 50 – 150 bursts/year
•Several spectral components?
•Self-compton component? (E > í 2e Ep)
•IC ambient rad. field?
•IC photospheric radiation?
•Ultra relativistic hadrons induce EM
cascades through photomeson and
photo-pair production
EGRET all years
E>100 MeV
GLAST 1 Year
E>100 MeV
Detection technique
– Tracker: Solid state detector
Si-strip pair conversion
Anticoincidence
tracker for gamma-ray
shield
detection and direction
measurement.
Conversion foils – CsI calorimeter: energy
measurement.
– Plastic scintillator antiParticle tracking
coincidence shield (ACD):
detectors
background rejection
charged particles.
e+
e–
Calorimeter
– Signature of a gamma
event:
No ACD signal
2 tracks (1 Vertex)*
Overview of Large Area Telescope

• Precision Si-strip Tracker
–
18 XY tracking planes. Single-sided
silicon strip detectors (228 mm pitch)
Measure the photon direction; gamma
ID.
–
EGRET: spark chamber, large dead time,
Tracker
• Hodoscopic CsI Calorimeter
–
Array of 1536 CsI(Tl) crystals in 8 layers.
Measure the photon energy; image the
shower.
–
EGRET: monolithic calorimeter: no
imaging and decreased resolution
• Segmented Anticoincidence Detector
–
–
e+
ACD
[surrounds
4x4 array of
TKR towers]
e–
89 plastic scintillator tiles. Reject
background of charged cosmic rays; Field of View
factor 4
segmentation reduces self-veto effects
Point Spread function factor > 3
at high energy.
effective area (
factor > 5
EGRET: monolithic ACD: self-veto due
to backsplash
Calorimeter
Results in factor > 30 improvement in sensitivity
below < 10 GeV, and >100 at higher energies.
Much smaller dead time factor ~4,000
No expendables
GLAST science menu:
Universe is largely transparent at LAT energies:
high-z and cosmic accelerators
Active Galactic Nuclei
Bazars: bulk of luminosity - 
EBL: attenuation of AGN spectra -SFH
Unidentified
sources
Cosmic ray acceleration:
Resolve SNR
Solar flares
Pulsars, cf.
PoGO
Quantum Strange Quark
Gravity ?
Matter ?
Gamma Ray Bursts
0.01 GeV
0.1 GeV
1 GeV
10 GeV
100 GeV
Dark matter
(decay exotic
annihil. LSP neutralinos):
large area,
1 TeV low bkg, emission line
High optical depth: >1
Low optical depth: <1
Photospheric radius: rph = 6*1012 L52 G2-3 cm
GRB: Broad band spectral coverage
To find out more, we need a broader spectral coverage.
Composite spectrum of GRB 930131;
BATSE, COMPTEL, and EGRET instruments
COMPTEL:
0.75 – 30 MeV
EGRET:
30MeV-30GeV
20keV
200MeV
Bromm & Schaefer 1999
Beyond the 20keV-2MeV band: GRB 941017
Gonzales et al., Nature 2003
Non-thermal Band-function
Light curves
BATSE-LAD
EGRET 1-10 MeV
Energy Spectra
High energy
Power-law
constant?
EGRET 10-200 MeV
hadrons=> EM cascades
(photo-meson and photo-pair prod)
200 MeV
Spectral components in the theoretical spectrum:
Thermal, photospheric emission (black body)
Thermal Photophere, T
Photospheric Comptonization, PHC
Mészáros et al. (2000)
. 2
=L/Mc
”Common”
in astrophysics
Shock Synchrotron, S
GLAST
BATSE
Shock pair-dominated Comptonization, C
See also Lyutikov & Usov (2000) , Drenkhahn & Spruit (2002), Daigne & Mochkovitch (2002),
Rees & Mészáros (2004), Pe’er, Mészáros, & Rees (2005)
Experimental Particle Physics @ KTH
KTH ATLAS group:
Bengt Lund-Jensen (Prof)
Stefan Rydström (Electronics engineer)
Karl-Johan Grahn (PhD student)
Mohamed Gouighri (Guest PhD student)
Per Hansson (PhD student)
Space radiation:
Christer Fuglesang (Aff. Prof)
Oscar Larsson (Dipl. Student)
Barrel presampler
Operational in ATLAS
Analysis of cosmic muons
All 64 sectors in place with electronics
Cosmic muon data analysis
HV status of the ATLAS barrel presampler
KTH shares the responsibility for the presampler.
(KTH, Grenoble, Casablanca).
The presampler is constructed by assembling anode
and cathode electrodes to form ~2 mm wide gaps of
liquid argon.
Some short circuits in the gaps appeared during
and after installation in ATLAS.These shorts are
assumed to be due to dust between the electrodes.
A short circuit results in one side of a group of
anodes being inactive, giving only half the signal in
32 readout channels, i.e. increaing the noise.
Standard electromagnetism also works in particle
physics experiments:
• By discharging a high voltage capacitor over the short
circuit the dust can be destroyed.
• In worst case thin copper lines on the anode
electrodes work as a fuses
So far we believe that we have burnt the dust rather
than the copper lines.
Presently there are 3 short circuits (out of 79616 cells), all reappering some time after
the burning campaign made in October 2006..
Optical cables for the Liquid Argon calorimeters
• Delivered, spliced and tested
ectronics room.
ack end read- out electronics
efan Rydstrom slicing the optical
ables.
he whole LiAr calorimeter has
een read out
HV supplies: (KTH participates)
All optical cables connected to
the back-end electronics.
problems with week components solved
by modifications. All modules retrofitted.
Working as expected.
Remaining modules of new type will be
delivered by end of September
Hadronic calibration
• Goal: Improving calorimeter resolution and linearity for hadronically
showering particles by applying relevant weightings and corrections.
• Activities
– Comparison of beam test data (pion data) with Geant4 Monte Carlo.
Dependence on hadronic physics lists.
– Improvements in liquid argon calorimeter simulation, e.g. saturation effect
for heavily ionizing particles.
– Investigation of weighting schemes exploiting layer correlations. Based on
principal component analysis of energy deposited in the different
calorimeter samplings, which capture properties of shower development.
– Dead material corrections. Correct for e.g. energy loss in cryostat between
liquid argon and tile calorimeters.
Hadronic Calibration in the ATLAS Barrel
Combined Beam Test
• Allows us to validate calibration procedures
on real data in a controlled environment.
• Data taken fall 2004, analysis still ongoing.
• All the sub detectors of the ATLAS barrel
region
– inner tracker
– liquid argon electromagnetic
calorimeter
– tile hadronic calorimeter
– muon tracker
together on at the H8
SPS beam line at CERN.
• Electrons/positrons, pions,
protons, energies 1–320 GeV
Dead material corrections applied to Monte Carlo and test beam
data
SUSY at LHC
Mass and branching fractions of the various SUSY particlea are model
dependent, (e.g. ways to break SUSY (GMSB,mSugra,etc,..))
Gluino and squark production dominates at LHC
R-parity conserved: complex cascade decay chains end with lightest SUSY
particle (usually neutralino)
Focus on final state -> distinct signature is missing transverse energy (MET)
2017-05-05
43
Desire (Dose Estimation by Simulation of the ISS Radiation Environment)
Work by Tore Ersmark
(left after PhD for a private company)
Idea: Use Geant4 for particle transport
through the space station and
especially the Columbus module in
order to estimate the radiation dose for
astronauts
Dose rate dependence
on geometry
• Simulation results are dependent
on level of detail of Geant4
geometry models
• Studied using three versions of
Columbus geometry models with
different level of detail
• C1 – Very simple, mass of 4400
kg, 10 volumes
• C3 – The most detailed model,
correct total mass of 16750 kg,
750 volumes
• C2 – Simplified version of C3,
23 volumes
Dose rate dependence on geometry
•
Increasing shielding thickness 
– Decreasing trapped proton dose
rate
– Increasing or constant GalacticCR
proton dose rate
– Increased amount of shielding
may be harmful in some cases!
•
Similar results for C2 and C3 
– C3 detail unnecessary in this case
•
C3I1 model used in studies
Continuation beyond Desire
Geant4 not perfect: Heavy ion models are only valid up to C.
Ion-nuclei interaction models only valid for < 10GeV/N.
Need to compare simulations and data.
Data available from the Sileye3/Alteino detector
on board ISS.
• 8 silicon detector planes 8x8 cm2 (380 μm thick)
• each plane is divided in 32 strips with 2.5mm pitch
• trigger is provided by two scintillators
Now: diploma work to analyze
data and compare with simple
Geant4 model
FIN
SUSY at LHC
Many (more or less conventional) ways to break SUSY (GMSB,mSugra,etc,..)
—
mSugra – hidden sector at GUT scale explicitly breaks susy -> 5 parameters
(m0,m1/2,A0,mu,tanBeta)
Gluino and squark production dominates at LHC
Cross section (pb)
—
—
—
—
Mass and branching fractions model dependent
Cross-sections model independent
gluinos/squarks cascade in complex decay
chains
R-parity conserved: decay chain ends with
0
lightest SUSY particle (usually neutralino 1 )
Average particle mass (GeV)
Focus on final state -> distinct signature is missing transverse energy (MET)
2017-05-05
49
SUSY predicting backgrounds (In collaboration with Stockholm
University)
Studying
signature with two leptons+jets+missing momentum
—
~95% of the background is top quark pair production
Smoking gun of SUSY
events with large missing
transverse momentum
Early measurements need background estimates from data
—
Our earlier experiences from top quark analyzes at the Tevatron is valuable
2017-05-05
50
SUSY predicting backgrounds
Developing methods to predict the top quark background from data
—
~95% of the background is top quark pair production
Isolate top quark pair events in data
—
Allows for a data-driven estimation of e.g. missing momentum
Use 'all' kinematic information
Solve system of 6 equations
Solution indicates if the event is “top like”
Crucial to understand the signal
contamination
2017-05-05
51
Summary
•
PoGOLite stands to open a new observation window on sources
such as rotation-powered pulsars and accreting black holes
through a measurement of the polarisation of soft gamma rays
(25-80 keV).
•
Well-type Phoswich detectors are used to significantly reduce
aperture and cosmic ray backgrounds.
•
A prototype Phoswich system and waveform sampling
electronics has been tested with photon and proton beams and
the design and simulation validated.
•
Construction of flight hardware is currently in progress
•
Engineering flight proposed for 2009 from Sweden. Maiden
science flight from USA proposed for 2010.
•
Long duration flights and flights of opportunity (GLAST,
SWIFT) will extend the rich scientific program.