Understanding Cosmic Rays and Searching for Dark Matter with PAMELA
description
Transcript of Understanding Cosmic Rays and Searching for Dark Matter with PAMELA
![Page 1: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/1.jpg)
UNDERSTANDING COSMIC RAYS AND SEARCHING FOR DARK MATTER WITH PAMELA
Roberta Sparvoli for the PAMELA CollaborationUniversity of Rome Tor Vergata and INFN
![Page 2: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/2.jpg)
COSMIC RAYS PRODUCTION MECHANISMS
![Page 3: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/3.jpg)
DARK MATTER SEARCHES
![Page 4: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/4.jpg)
EXPECTED DM SIGNALS
Deviations of the antiparticle spectra wrt secondary production
![Page 5: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/5.jpg)
p-bar, e+
Halo
PAMELA SCIENTIFIC GOALS
![Page 6: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/6.jpg)
PAMELA DESIGN PERFORMANCE
energy range particles in 3 years
Antiprotons 80 MeV ÷190 GeV O(104)Positrons 50 MeV ÷ 270 GeV O(105) Electrons up to 400 GeV O(106)Protons up to 700 GeV O(108)Electrons+positrons up to 2 TeV (from calorimeter)Light Nuclei up to 200 GeV/n He/Be/C: O(107/4/5)Anti-Nuclei search sensitivity of 3x10-8 in anti-He/He
Magnetic curvature & trigger spillover showercontainment
Maximum detectable rigidity (MDR)
![Page 7: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/7.jpg)
PAMELA DETECTORS
GF: 21.5 cm2 sr Mass: 470 kgSize: 130x70x70 cm3
Power Budget: 360W Spectrometer microstrip silicon tracking system + permanent magnetIt provides:
- Magnetic rigidity R = pc/Ze- Charge sign- Charge value from dE/dx
Time-Of-Flightplastic scintillators + PMT:- Trigger- Albedo rejection;- Mass identification up to 1
GeV;- Charge identification from dE/dX.
Electromagnetic calorimeterW/Si sampling (16.3 X0, 0.6 λI) - Discrimination e+ / p, anti-p /
e- (shower topology)- Direct E measurement for e-
Neutron detector36 He3 counters - High-energy e/h discrimination
Main requirements high-sensitivity antiparticle identification and precise momentum measure+ -
![Page 8: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/8.jpg)
THE RESURS DK-1 SPACECRAFT
![Page 9: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/9.jpg)
![Page 10: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/10.jpg)
![Page 11: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/11.jpg)
PAMELA STATUS
Today 1350 days in flight
data taking ~73% live-time
>19 TBytes of raw data downlinked
>2. 109 triggers recorded and under analysis
![Page 12: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/12.jpg)
ANTIPROTON/POSITRON DISCRIMINATION
energy measurement
![Page 13: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/13.jpg)
ANTIPARTICLE SELECTION
e- e+
p, dp
‘Electron’
‘Hadron’
![Page 14: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/14.jpg)
ANTIPROTONS
![Page 15: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/15.jpg)
• Antiproton/proton identification:• rigidity (R) SPE• |Z|=1 (dE/dx vs R) SPE&ToF• b vs R consistent with Mp ToF• p-bar/p separation (charge sign) SPE• p-bar/e- (and p/e+ ) separation CALO
• Dominant background spillover protons:
• finite deflection resolution of the SPE wrong assignment of charge-sign @ high energy
• proton spectrum harder than antiproton p/p-bar increase for increasing energy (103 @1GV 104 @100GV)
Required strong SPE selection
HIGH-ENERGY ANTIPROTON ANALYSIS
![Page 16: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/16.jpg)
PROTON-SPILLOVER BACKGROUND
Electrons: efficiently removed by CALOPions (from interactions in dome) : about 3% in the
pbar sample
![Page 17: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/17.jpg)
PAMELA: ANTIPROTON-TO-PROTON RATIO
PRL 102, 051101 (2009)
![Page 18: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/18.jpg)
PAMELA: ANTIPROTON-TO-PROTON RATIO
PRL 102, 051101 (2009)
![Page 19: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/19.jpg)
ANTIPROTON-TO-PROTON RATIO: NEW DATA
Errors might be underestimated, possible residual spillover-proton contamination
Increased statistics (until Dec. 2008)
![Page 20: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/20.jpg)
• PAMELA
Errorsunderestimated, possible residual spillover-proton contamination
ANTIPROTON FLUXIncreased statistics
![Page 21: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/21.jpg)
POSITRONS
![Page 22: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/22.jpg)
• Electron/positron identification:• rigidity (R) SPE • |Z|=1 (dE/dx=MIP) SPE&ToF• b=1 ToF• e-/e+ separation (charge sign) SPE• e+/p (and e-/p-bar) separation CALO
• Dominant background interacting protons:• fluctuations in hadronic shower development p0 gg might mimic pure em showers
• proton spectrum harder than positron p/e+ increase for increasing energy (103 @1GV 104 @100GV)
Required strong CALO selection
HIGH-ENERGY POSITRON ANALYSISS1
S2
CALOS4
CARD
CAS
CAT
TOFSPE
S3
ND
![Page 23: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/23.jpg)
POSITRON IDENTIFICATION WITH CALO
Identification based on: Shower topology (lateral and longitudinal
profile, shower starting point) Total detected energy (energy-rigidity
match) Analysis key points:
Tuning/check of selection criteria with: test-beam data simulation flight data dE/dx from SPE & neutron
yield from ND Selection of pure proton sample from
flight data (“pre-sampler” method): Background-suppression method Background-estimation method
Final results make NO USE of test-beam and/or simulation calibrations.The measurement is based only on flight datawith the background-estimation method
51 GV positron
80 GV proton
![Page 24: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/24.jpg)
PAMELA: POSITRON FRACTIONNATURE 458, 697, 2009
Solar modulation effects
Anomalous increasing ?
(Moskalenko & Strong 1998) GALPROP code • Plain diffusion
model • Interstellar
spectra
![Page 25: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/25.jpg)
PAMELA: POSITRON FRACTION WRT OTHER EXP’SNATURE 458, 697, 2009
![Page 26: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/26.jpg)
Test Beam Data
ESTIMATED PROTON CONTAMINATION WITH “PRE-SAMPLER” METHOD
![Page 27: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/27.jpg)
Two different analysis methods
POSITRON TO ELECTRON FRACTION: NEW DATA
Factor 2.5 increase in statistics (factor 3 in the highest energy bin)
Data: July 2006 December 2008
“A statistical procedure for the identification of positrons in the PAMELA experiment”, O. Adriani et al., astro-ph, arXiv: 1001.3522v1, in publication on APP !
![Page 28: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/28.jpg)
PRIMARY POSITRON SOURCESDark Matter
e+ yield depend on the dominant decay channel LSPs (SUSY) seem disfavored due to
suppression of e+e- final states low yield (relative to p-bar) soft spectrum from cascade decays
LKPs seem favored because can annihilate directly in e+e- high yield (relative to p-bar) hard spectrum with pronounced cutoff @
MLKP (>300 GeV)
Boost factor required to have a sizable e+ signal NB: constraints from p-bar data!!
Other hypothesys possible and under study (i.e. Minimal DM Model, decaying DM, new gauge bosons, …)
LKP -- M= 300 GeV (Hooper & Profumo 2007)
More than 150 articles claim DM is discovered !M. Cirelli’s talk later …
![Page 29: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/29.jpg)
EXAMPLE: DARK MATTER
![Page 30: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/30.jpg)
PRIMARY POSITRON SOURCESAstrophysical processes Local pulsars are well-known
sites of e+e- pair production (the spinning B of the pulsars strips e- that emit gammas then converting to pairs trapped in the cloud, accelerated and then escaping at the Poles) : they can individually and/or
coherently contribute to the e+e- galactic flux and explain the PAMELA e+ excess (both spectral feature and intensity) No fine tuning required
if one or few nearby pulsars dominate, anisotropy could be detected in the angular distribution possibility to discriminate between
pulsar and DM origin of e+ excess
All pulsars (rate = 3.3 / 100 years)(Hooper, Blasi, Seprico 2008)
![Page 31: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/31.jpg)
EXAMPLE: PULSARS
![Page 32: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/32.jpg)
Revision of standard CR model
o Pairs created also in the acceleration sites (e.g. in old SNRs);
o Distribution of CR sources not homogeneus
(SNRs more in spiral arms)
![Page 33: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/33.jpg)
POSITRONS FROM OLD SNR’SP. BLASI , PRL 103, 051104 (2009)
![Page 34: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/34.jpg)
EXPLANATION WITH SUPERNOVAE REMNANTS
SHAVIV, NAKAR & PIRAN, ASTRO-PH.HE 0902.0376
![Page 35: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/35.jpg)
HOW TO CLARIFY THE MATTER?C
ourtesy of J. Edsjo
![Page 36: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/36.jpg)
ELECTRONS
Any positron source is an electron source too …
![Page 37: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/37.jpg)
RECENT CLAIMS OF (e++e-) EXCESS
FERMI does not confirm the ATIC bumpbut finds an excess wrt conventional diffusive models
g = 3.0
![Page 38: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/38.jpg)
PAMELA ELECTRON (e-) SPECTRUM
![Page 39: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/39.jpg)
PAMELA ELECTRON (e-) SPECTRUM
![Page 40: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/40.jpg)
PAMELA ELECTRON (e-) SPECTRUM
0.02
Additional source?
![Page 41: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/41.jpg)
PAMELA ELECTRON (e-) SPECTRUM
![Page 42: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/42.jpg)
PAMELA ELECTRON (e+ + e- ) SPECTRUM
![Page 43: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/43.jpg)
PAMELA ALL ELECTRONS HIGH ENERGYVERY PRELIMINARY
Energy measurement done with the calorimeter
![Page 44: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/44.jpg)
PROTONS, HELIUMS, NUCLEI, …
![Page 45: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/45.jpg)
PAMELA PROTON FLUX
![Page 46: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/46.jpg)
PAMELA PROTON FLUX
Hardening of spectrum?
![Page 47: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/47.jpg)
PAMELA HELIUM FLUX
![Page 48: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/48.jpg)
PAMELA HELIUM FLUX
Hardening of spectrum?
![Page 49: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/49.jpg)
PAMELA SECONDARY/PRIMARY NUCLEI RATIOS
Currently collected (data analyzed until Dec. 2008):
120.000 C nuclei 70.000 B nuclei
![Page 50: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/50.jpg)
PAMELA SECONDARY/PRIMARY: B/C
preliminary
![Page 51: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/51.jpg)
PAMELA SECONDARY/PRIMARY: BE/C
![Page 52: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/52.jpg)
PAMELA SECONDARY/PRIMARY: LI/C
![Page 53: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/53.jpg)
C/O RATIO
PreliminaryPreliminary
![Page 54: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/54.jpg)
HELIOSPHERE AND MAGNETOSPHERE
![Page 55: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/55.jpg)
SOLAR MODULATION
![Page 56: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/56.jpg)
LOW ENERGY e+: CHARGE DEPENDENTSOLAR MODULATION EFFECTS
![Page 57: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/57.jpg)
CHARGE-DEPENDENT SOLAR MODULATIONIN THE POSITRON FRACTION
![Page 58: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/58.jpg)
PAMELA ELECTRON-TO-POSITRON RATIO AND THEORETICAL MODELS
U.W. Langner, M.S. Potgieter, Advances in Space Research 34 (2004)
Jointy work with M. Potgieter’s group in South-Africa going on
![Page 59: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/59.jpg)
PHYSICS OF THE MAGNETOSPHERE
Measurements of quasi-trapped electron and positron fluxes with PAMELAJournal of Geophysical Research, 114, A12, pag. A12218, 2009
![Page 60: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/60.jpg)
36 MeV p, 3.5 MeV e-
Pamela World Map: 350 – 650 km alt
PHYSICS OF THE MAGNETOSPHERE
![Page 61: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/61.jpg)
SUBCUTOFF ANTIPROTONS IN SAA
![Page 62: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/62.jpg)
>19
~44
SUMMARY
![Page 63: Understanding Cosmic Rays and Searching for Dark Matter with PAMELA](https://reader036.fdocuments.net/reader036/viewer/2022062520/56815ec9550346895dcd5024/html5/thumbnails/63.jpg)
Interesting features in cosmic ray data seen by PAMELA in last months’ analysis:
Electron flux: spectrum up to ~200 GeV shows spectral features that may point to additional components. Analysis is ongoing to increase the statistics and expand the measurement of the e- spectrum up to ~500 GeV and e+ spectrum up to ~300 GeV (all electrum (e-+ e+) spectrum up to ~1 TV).
Proton and Helium fluxes: hardening of the spectrum at high energies:
Effects of propagation and reacceleration? Harder spectral sources? Possible hadron sources (seen by other experiments as anisotropies?)
Other measurements under study: New antiHe limits Strange matter (particles with high A/Z) Solar flares
SUMMARY