Constraints to dark matter and cosmic ray propagation by the pamela space experiment
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Constraints to Dark Matter and cosmic ray propagation by the PAMELA space experiment. Roberta Sparvoli University of Rome ”Tor Vergata” and INFN. Everything starts with …. Evaporation of primordial black holes. Anti-nucleosyntesis. WIMP dark-matter annihilation in the galactic halo.

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Constraints to Dark Matter and cosmic ray propagation by the PAMELA space experiment

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Constraints to dark matter and cosmic ray propagation by the pamela space experiment

Constraints to Dark Matter and cosmic ray propagation by the PAMELA space experiment

Roberta Sparvoli

University of Rome ”Tor Vergata”

and INFN


Constraints to dark matter and cosmic ray propagation by the pamela space experiment

Everything starts with …

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


And various ideas of theoretical interpretations

Evaporation of primordial black holes

Anti-nucleosyntesis

WIMP dark-matter annihilation in the galactic halo

Background:

CR interaction with ISM

CR + ISM  p-bar + …

and various ideas of theoretical interpretations

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


Constraints to dark matter and cosmic ray propagation by the pamela space experiment

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


Constraints to dark matter and cosmic ray propagation by the pamela space experiment

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


Cr antimatter

Charge-dependent solar modulation

Solar polarity reversal 1999/2000

Asaoka Y. Et al. 2002

Positron excess?

?

?

¯

+

  • CR + ISM  p-bar + …

  • Propagation dominated by nuclear interactions

  • Kinematical threshold: Eth~5.6 for the reaction

CR antimatter

Experimental scenario before PAMELA

WHAT DO WE NEED TO BETTER UNDERSTAND ?

Measurements at higher energies

Better knowledge of background

High statistics

Continuous monitoring of solar modulation

Long Duration Flights

Positrons

Antiprotons

___ Moskalenko & Strong 1998

  • CR + ISM  p± + x m± + x  e± + x

  • CR + ISM  p0 + x gg e±

  • Propagation dominated by energy losses

  • (inverse Compton & synchrotron radiation)

  • Local origin (@100GeV 90% from <2kpc)

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


Pamela pre history

PAMELA pre-history

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


The pamela collaboration

Italy

CNR, Florence

Bari

Florence

Frascati

Naples

Rome

Trieste

Russia

Moscow

St. Petersburg

Germany

Sweden

Siegen

KTH, Stockholm

The PAMELA collaboration

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


Pamela scientific goals

PAMELA Scientific goals

Halo

p-bar, e+

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


Pamela design performance

PAMELA design performance

Maximum detectable rigidity (MDR)

energy rangeparticles in 3 years

Antiprotons80 MeV ÷190 GeV O(104)

Positrons50 MeV ÷ 270 GeVO(105)

Electrons up to 400 GeVO(106)

Protonsup to 700 GeVO(108)

Electrons+positronsup to 2 TeV (from calorimeter)

LightNuclei up to 200 GeV/n He/Be/C:O(107/4/5)

Anti-Nuclei searchsensitivity of 3x10-8 in anti-He/He

Magnetic curvature & trigger

spillover

shower

containment

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


Pamela detectors

PAMELA detectors

Main requirements  high-sensitivity antiparticle identification and precise momentum measure

+ -

  • Time-Of-Flight

  • plastic scintillators + PMT:

  • Trigger

  • Albedo rejection;

  • Mass identification up to 1 GeV;

  • - Charge identification from dE/dX.

  • Electromagnetic calorimeter

  • W/Si sampling (16.3 X0, 0.6 λI)

  • Discrimination e+ / p, anti-p / e-

  • (shower topology)

  • Direct E measurement for e-

  • Neutron detector

  • 36 He3 counters

  • High-energy e/h discrimination

GF: 21.5 cm2 sr Mass: 470 kg

Size: 130x70x70 cm3

Power Budget: 360W

  • Spectrometer

  • microstrip silicon tracking system+ permanent magnet

  • It provides:

    • - Magnetic rigidity R = pc/Ze

    • Charge sign

    • Charge value from dE/dx

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


The resurs dk 1 spacecraft

The Resurs DK-1 spacecraft

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


Constraints to dark matter and cosmic ray propagation by the pamela space experiment

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


Constraints to dark matter and cosmic ray propagation by the pamela space experiment

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


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

PAMELA milestones

Main antenna in NTsOMZ

Trigger rate* ~ 25 Hz

Fraction of live time* ~ 75%

Event size (compressed mode) ~ 5kB

25 Hz x 5 kB/ev ~ 10 GB/day

(*outside radiation belts)

  • Today 1212 days in flight

  • >14 TBytes of raw data downlinked

  • >109 triggers recorded and under analysis

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


Antiproton positron discrimination

Antiproton/positron discrimination

energy measurement

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


Antiparticle selection

e-

e+

‘Electron’

‘Hadron’

p, d

p

Antiparticle selection

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


Antiprotons

Antiprotons

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


High energy antiproton analysis

High-energy antiproton analysis

  • Analyzed data July 2006 – February 2008 (~500 days)

  • Collected triggers ~108

  • Identified ~ 10 106 protons and ~ 1 103 antiprotons between 1.5 and 100 GeV ( 100 p-bar above 20 GeV )

  • 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

 Roberta Sparvoli  October 8th, 2009  Como (Italy)


Proton spillover background

Proton-spillover background

  • Electrons: efficiently removed by CALO

  • Pions (from interactions in dome) : about 3% in the pbar sample

  •  Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Pamela antiproton to proton ratio

    PAMELA: Antiproton-to-proton ratio

    PRL 102, 051101 (2009)

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Pamela antiproton to proton ratio1

    PAMELA: Antiproton-to-proton ratio

    PRL 102, 051101 (2009)

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Constraints to dark matter and cosmic ray propagation by the pamela space experiment

    PAMELA: Antiproton-to-proton ratioNew (preliminary) data !

    Full statistics

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Pamela antiproton flux preliminary

    PAMELA: Antiproton flux preliminary

    • PAMELA

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Positrons

    Positrons

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    High energy positron analysis

    S1

    CARD

    CAT

    S2

    TOF

    SPE

    CAS

    S3

    CALO

    S4

    ND

    High-energy positron analysis

    • Analyzed data July 2006 – February 2008 (~500 days)

    • Collected triggers ~108

    • Identified ~ 150 103 electrons and ~ 9 103 positrons between 1.5 and 100 GeV (180 positrons above 20 GeV)

    • 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 ggmight mimic pure em showers

      • proton spectrum harder than positron  p/e+ increase for increasing energy (103 @1GV 104 @100GV)

    •  Required strong CALO selection

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Positron identification with calo

    Positron identification with CALO

    51 GV positron

    • 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

    80 GV proton

    Final results make NO USE of test-beam and/or simulation calibrations.

    The measurement is based only on flight data

    with the background-estimation method

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Particle selection after total energy cut and starting point of the shower

    Particle selection after total energy cut and starting point of the shower

    e+

    e -

    (anti p)

    p

    +

    -

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Pamela positron fraction

    PAMELA: Positron fraction

    NATURE 458, 697, 2009

    • (Moskalenko & Strong 1998)

    • GALPROP code

    • Plain diffusion model

    • Interstellar spectra

    Solar modulation effects

    Anomalous increasing ?

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Constraints to dark matter and cosmic ray propagation by the pamela space experiment

    PAMELA: Positron fraction wrt other exp’s

    NATURE 458, 697, 2009

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Different statistical approaches for the bkg

    Different statistical approaches for the bkg

    Data: July 2006  December 2008

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    New data systematic error

    New data + systematic error

    In publication

    on APP !

    Data: July 2006  December 2008

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Pamela antimatter data

    PAMELA antimatter data:

    Do we have any antimatter excess in CRs?

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Antiproton to proton ratio secondary production models

    ~20%

    • NB!

    • Solar modulation

    • Nuclear cross-section

    Antiproton-to-proton ratioSecondary Production Models

    CR + ISM  p-bar + …

     Uncertainty band related to propagation parameters (~10% @10 GeV)

     Additional uncertainty of ~25% due to production cs should be considered !!

    No evidence for any antiproton excess

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Positron fraction secondary production models

    Positron fractionSecondary Production Models

    CR + ISM  p± + … m± + …  e± + …

    CR + ISM  p0 + … gg e±

    • Increasing positron fraction only if

    • ge- gp > 0.6

    • unlikely

      (Serpico 2008)

    Quite robust evidence for a positron excess

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Primary positron sources

    Primary positron sources

    Dark 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 !

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Example dark matter

    Example: dark matter

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Primary positron sources1

    Primary positron sources

    Astrophysical 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)

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Example pulsars

    Example: pulsars

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Explanation with supernovae remnants shaviz and al astro ph he 0902 0376

    Explanation with supernovae remnantsShaviz and al. astro-ph.HE0902.0376

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Positrons from old snr s p blasi 0903 2794

    Positrons from old SNR’sP. Blasi 0903.2794

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Constraints to dark matter and cosmic ray propagation by the pamela space experiment

    Standard Positron Fraction

    Theoretical Uncertainties

    γ = 3.54

    γ = 3.34

    Need for high statistics CR measurements

    T. Delahaye et al., arXiv: 0809.5268v3

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Electrons

    Electrons

    Any positron source is an electron source too …

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Recent claims of e e excess

    Recent claims of (e++e-) excess

    g = 3.0

    FERMI does not confirm the ATIC bump

    but finds an excess wrt conventional diffusive models

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Pamela electron flux measurements

    PAMELA electron flux measurements

    Key points wrt other experiments (ATIC, HESS, FERMI) :

    • Combination of CALO and SPECTROMETER allow energy self- calibration in flight no dependence on ground calibrations or MC simulations

    • Very deep CALO (16 X0)  containment of the shower maximum beyond 1 TeV

    • Neutron detector help proton rejection, especially at high energy

    • No atmospheric contamination

    • Possibility to disentangle electrons from positrons

      But ..

    • Smaller acceptance  lower statistics

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Constraints to dark matter and cosmic ray propagation by the pamela space experiment

    PAMELA electron flux

    preliminary

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Constraints to dark matter and cosmic ray propagation by the pamela space experiment

    PAMELA electron flux wrt other exp’s

    preliminary

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Constraints to dark matter and cosmic ray propagation by the pamela space experiment

    PAMELA electron flux

    preliminary

    Data ready by the end of the year

    Primary source ???

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Protons nuclei

    Protons, nuclei, …

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Galactic protons and helium fluxes

    Galactic protons and Helium fluxes

    preliminary

    p

    He

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Pamela proton and helium fluxes

    PAMELA proton and helium fluxes

    preliminary

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Proton flux compared to prev exp s

    Proton flux compared to prev. exp’s

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Pamela secondary primary nuclei ratios

    PAMELA secondary/primary nuclei ratios

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Pamela secondary primary nuclei ratios1

    PAMELA secondary/primary nuclei ratios

    preliminary

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Solar modulation

    Solar modulation

    Interstellar spectrum

    PAMELA

    Ground neutron monitor

    sun-spot number

    (statistical errors only)

    Increasing

    GCR flux

    July 2006

    August 2007

    February 2008

    Decreasing

    solar activity

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Solar modulation1

    Solar modulation

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Low energy e charge dependent solar modulation effects

    Low energy e+: charge dependentsolar modulation effects

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Charge dependent solar modulation

    Charge dependent solar modulation

    +

    ¯

    A > 0

    Positive particles

    A < 0

    Preliminary!!

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Summary

    Summary

    ~40

    14

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


    Summary1

    PAMELA positron fraction alone insufficient to understand the origin of positron excess

    Additional experimental data will be provided by PAMELA:

    e+ fraction @ higher energy (up to 300 GeV)

    individual e- and e+ spectra

    anisotropy (…maybe)

    high energy e++e- spectrum (up to 2 TV)

    Complementary information from:

    gamma rays

    neutrinos

    Summary

    PAMELA mission extended to end 2011 !

    It will be possible to constrain further the nature of DM and models of cosmic ray propagation in the Galaxy.

     Roberta Sparvoli  October 8th, 2009  Como (Italy)


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