Astroparticle Physics at the Royal Institute of Technology

Faculty:Professor Mark PearceDocent 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)

Presented by Felix Ryde

• 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 balloon-borne instrumentation, and on the analysis and astrophysical interpretation of the data obtained with these instruments.

Astroparticle Physics at KTH

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)

•PAMELAPayload 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

Design performance

• Energy range Particles/3 years

• Antiproton flux 80 MeV - 190 GeV >3x104

• Positron flux 50 MeV – 270 GeV >3x105

• Electron flux up to 400 GeV 6x106

• Proton flux up to 700 GeV 3x108

• Electron/positron flux up to 2 TeV (from calorimeter)

• Light nuclei (up to Z=6) up to 200 GeV/n He/Be/C: 4 107/4/5

• Antinuclei search Sensitivity of 3x10-8 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 data1 CAPRICE98 flight ~ 3.9 days PAMELA data

‘Spillover’Magnetic curvature(trigger) Maximum

Detectable Rigidity (MDR)

EM shower containment

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

Sign of charge, rigidity, dE/dx

Electron energy, dE/dx, lepton-

hadron separation

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)

Signal (SUSY)…

… background

pppppp ISMCR

eeXpp

eXpp

ISMCR

eISMCR

;;

;;00

Antiprotons

Secondary production (upper and lower limits)

Simon et al. ApJ 499 (1998) 250.

Secondary production

(CAPRICE94-based)Bergström et al. ApJ

526 (1999) 215

Primary production from annhilation (m() = 964 GeV)

Secondary production ‘C94 model’ + primary

distortion

PAMELA

Ullio : astro-ph/9904086

AMS-01: space shuttle, 1998

CAPRICE balloon experiment, 1998

Z=1

Z=2

~2.76

~2.71

Galactic p and He spectra

Preliminary !!!

PoGOLite - polarization of soft gamma-raysDAQ 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

• from a polarised source undergo Compton scattering in a suitable detector material

• Higher probability of being scattered perpendicular to the electric field vector (polarisation direction)

• Observed azimuthal scattering angles are therefore modulated by polarisation

• Incident deposits little energy at Compton site

• ‘Large’ energy deposited at photoelectric absorption site

• large energy difference

• Can be distinguished by simple plastic scintillators (despite poor intrinsic energy resolution)

E

Photoelectric absorption

Compton scatter

Array of plastic scintillators

Well-type phoswich detectorA narrow field-of-view and low background instrument

• Pink: Phoswich Detector Cells (total 217units)

• Orange: Side Anti-counter Shield (total 54 BGO)

• Yellow: Neutron Shield (polyethylene)

Phoswich Detector Cell

140cm

Valid event

PoGOLite polarimeter – schematic

60 cm

100 cm

e.g. G L A S T

rtE ˆ,,

PrtE ˆ,ˆ,,

P o G OLite

[10 keV – 300 GeV]

[25 – 80 keV]

• 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

sensitive to the ‘history’ of the photon

SLAC / Stanford- KIPAC

KTH, Stockholm University

Tokyo Institute of Technology, Hiroshima University, ISAS/JAXA, Yamagata University.

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 modelsPolar Cap, Outer Gap Caustic Models +Cyg X-1: reflection component in hard state - Long duration flight+ Her X-1: cyclotron absorption lines.

Engineering flight: 2009 / Science flight: 2010Primary 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

• Engineering flight from Sweden planned for 2009. Long duration Sweden to Canada also proposed.

Pulsar / SNR

Accreting X-ray pulsar

High-mass X-ray binary

GLAST - 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: Principal Investigator:

Peter MichelsonPeter Michelson (Stanford & SLAC)

~270 Members (includes ~90 Affiliated Scientists,37 Postdocs,

and 48 Graduate Students)

Gamma-ray Large Gamma-ray Large Area Space Area Space TelescopeTelescope

GLAST Key Features

Imaging gamma-ray telescope Two GLAST instruments:

LAT (Large Area Telescope): 20 MeV – >300 GeVGBM (GLAST Burst Monitor) 10 keV – 25 MeVLaunch: 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 %.

Large Area Telescope (LAT)

GBM

LAT FoV

GBM FoV

GLAST SensitivityGLAST Sensitivity

•30 times better sensitivity (5x for GRBs)

•Good localization 30’’- 5’ (FOV 2-3 sr)

•Good energy resolution ~10%

• 50 – 150 bursts/year

GLAST Burst Monitor (GBM): 10 keV – 25 MeV Large Area Telescope (LAT): 20 MeV – 300 GeV Launch: early 2008

•Several spectral components?•Self-compton component?•IC ambient rad. field?•IC photospheric radiation? •Ultra relativistic hadrons induce EM cascades through photomeson and photo-pair production

(E > í 2e Ep)

EGRET all years

E>100 MeV

GLAST 1 Year

E>100 MeV

– Tracker: Solid state detector Si-strip pair conversion tracker for gamma-ray detection and direction measurement.

– CsI calorimeter: energy measurement.

– Plastic scintillator anti-coincidence shield (ACD): background rejection charged particles.

– Signature of a gamma event: No ACD signal 2 tracks (1 Vertex)*

Detection technique

e+ e– Calorimeter

Particle tracking detectors

Conversion foils

Anticoincidenceshield

e+ e–

Overview of Large Area Telescope

• Precision Si-strip TrackerPrecision 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,

• Hodoscopic CsI CalorimeterHodoscopic 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 DetectorSegmented Anticoincidence Detector

– 89 plastic scintillator tiles. Reject background of charged cosmic rays; segmentation reduces self-veto effects at high energy.

– EGRET: monolithic ACD: self-veto due to backsplash

Calorimeter

Tracker

ACD [surrounds 4x4 array of TKR towers]

Field of View factor 4 Point Spread function factor > 3 effective area ( factor > 5Results in factor > 30 improvement in sensitivity Results in factor > 30 improvement in sensitivity below < 10 GeV, and >100 at higher energies.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

0.01 GeV 0.1 GeV 1 GeV 10 GeV 100 GeV 1 TeV0.01 GeV 0.1 GeV 1 GeV 10 GeV 100 GeV 1 TeV

Gamma Ray Bursts

Unidentified sources

Cosmic ray acceleration:Resolve SNR

Active Galactic NucleiBazars: bulk of luminosity -

EBL: attenuation of AGN spectra -SFH

Dark matter (decay exotic,annihil. LSP neutralinos): large area, low bkg, emission line

Solar flares

Pulsars, cf. PoGO

Strange Quark

Matter ? Quantum Gravity ?

High optical depth: >1 Low optical depth: <1

Photospheric radius: rph = 6*1012 L52 2-3 cm

Composite spectrum of GRB 930131;BATSE, COMPTEL, and EGRET instruments

Bromm & Schaefer 1999

COMPTEL:0.75 – 30 MeV

EGRET:30MeV-30GeV

20keV 200MeV

GRB: Broad band spectral coverageGRB: Broad band spectral coverage

To find out more, we need a broader spectral coverage.

Beyond the 20keV-2MeV band: GRB 941017Beyond the 20keV-2MeV band: GRB 941017Gonzales et al., Nature 2003

BATSE-LAD

EGRET 1-10 MeV

EGRET 10-200 MeV

Non-thermal Band-function

High energy Power-law

constant?

Light curves

Energy Spectra

200 MeVhadrons=> EM cascades(photo-meson and photo-pair prod)

Thermal Photophere, T

Shock Synchrotron, S

Photospheric Comptonization, PHC

Shock pair-dominated Comptonization, C

=L/Mc. 2

See also Lyutikov & Usov (2000) , Drenkhahn & Spruit (2002), Daigne & Mochkovitch (2002), Rees & Mészáros (2004), Pe’er, Mészáros, & Rees (2005)

BATSE

GLAST

Spectral components in the theoretical spectrum:Spectral components in the theoretical spectrum:

ThermalThermal, , photospheric emission (black body)photospheric emission (black body)Mészáros et al. (2000)

”Common” in astro-physics

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 presamplerOperational in ATLASAnalysis of cosmic muons

All 64 sectors in place with electronicsAll 64 sectors in place with electronicsCosmic muon data analysisCosmic muon data analysis

HV status of the ATLAS barrel presampler

KTH shares the responsibility for the presampler.(KTH, Grenoble, Casablanca).(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 Some short circuits in the gaps appeared during and after installation in ATLASand 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 fusesSo 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

Electronics room. Back end read- out electronicsStefan Rydstrom slicing the optical cables.

The whole LiAr calorimeter has been read out

All optical cables connected to the back-end electronics.

HV supplies: (KTH participates)

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 trackertogether 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

23-04-19 43

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)

SUSY at LHC

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 dependenceon 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 DesireGeant4 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 detectoron 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

23-04-19 49

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

Focus on final state -> distinct signature is missing transverse energy (MET)

SUSY at LHC

— Mass and branching fractions model dependent— Cross-sections model independent— gluinos/squarks cascade in complex decay

chains— R-parity conserved: decay chain ends with

lightest SUSY particle (usually neutralino )Cro

ss s

ecti

on

(pb)

Average particle mass (GeV)

10

23-04-19 50

Studying signature with two leptons+jets+missing momentum— ~95% of the background is top quark pair production

SUSY predicting backgrounds (In collaboration with Stockholm

University)

Early measurements need background estimates from data— Our earlier experiences from top quark analyzes at the Tevatron is valuable

Smoking gun of SUSYevents with large missing transverse momentum

23-04-19 51

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

SUSY predicting backgrounds

Use 'all' kinematic informationSolve system of 6 equations

Solution indicates if the event is “top like”Crucial to understand the signal contamination

Work in progress

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.