ROBERTA SPARVOLI

UNIVERSITY OF ROME “TOR VERGATA”AND INFN

MORIOND 2013: VERY HIGH ENERGY PHENOMENA

IN THE UNIVERSE

Electron/positron ratio & antiproton/proton ratio in

PAMELA and Fermi

Dark Matter searches

Evidence for the existence of an unseen, “dark”, component in the energy density of the Universe comes from several independent observations at different length scales:

Rotation curves of galaxies

Lensing

Large Scale StructureCMB

Galaxy clusters SN Ia

Bertone, Hooper & Silk, hep-ph/0404175, Bergstrom, hep-ph/0002126, Jungman et al, hep-ph/9506380

The “Concordance Model” of cosmology

tot = 1.0030.010

m ~ 0.22 [b=0.04] ~ 0.74

Most of matter of non-baryonic natureand therefore “dark” !

The “concordance model” of big bang cosmology attempts to explain cosmic microwave background observations, as well as large scale structure observations and supernovae observations of the accelerating expansion of the universe.

Different data:WD supernovae• CMB• Matter surveysall agreeat one point

•Kaluza-Klein DM in UED•Kaluza-Klein DM in RS •Axion•Axino•Gravitino•Photino•SM Neutrino•Sterile Neutrino•Sneutrino•Light DM•Little Higgs DM•Wimpzillas•Q-balls•Mirror Matter•Champs (charged DM)•D-matter•Cryptons•Self-interacting•Superweakly interacting•Braneworld DM•Heavy neutrino•NEUTRALINO•Messenger States in GMSB•Branons•Chaplygin Gas•Split SUSY•Primordial Black Holes

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L. Roszkowski

Dark matter candidates

DM candidates: WIMP’s !SUSY particles ?

Neutralino as the CDM candidate

204

103

30201

~~~~HaHaWaBa

• Stable (if R-parity is conserved)• Mass: mc~ 10-1000 GeV• Non-relativistic at decoupling

CDM• Neutral & colourless• Weakly interacting (WIMP)• Good relic density

Linear combination of the neutral gauge bosons B and W3 and the neutral higgsinos H1 and H2. The neutralino is a good candidate because:

SIGNALS from RELIC WIMPs

Direct searches: elastic scattering of a WIMP off detector nuclei

Measure of the recoil energy

Indirect detection: in cosmic radiation signals due to annihilation of accumulated cc in the centre

of celestial bodies (Earth and Sun) neutrino flux

signals due to cc annihilation in the galactic halo neutrinos gamma-rays antiprotons, positrons, antideuterons

For a review, see i.e. Bergstrom hep-ph/0002126

n and g keep directionality can be detected only if emitted from high c density regionsCharged particles diffuse in the galactic halo antimatter searched as rare components in cosmic rays

PAMELAFERMI, AMS

Neutralino annihilation

Production takes place everywhere in the halo!!The presence of neutralino annihilation will destort the positron, antiproton and gamma energy spectrum from purely secondary production

Spectrum deformation

LIGHTEST KALUZA-KLEIN PARTICLE (LKP): B ( 1 )

Another possible scenario: KK Dark Matter

Bosonic Dark Matter:fermionic final states no longer helicity suppressed.e+e- final states directly produced.

As in the neutralino case there are 1-loopprocesses that produces monoenergeticγ γ in the final state.

Kaluza-Klein Dark Matter in e+e-

Direct annihilation of the Lightest Kaluza-Klein particle (LKP) into electron-positron pair in the Galactic halo (Baltz and Hooper, JCAP 7,

2007, and references therein)

e- + e+ yield is estimated to be ~20% per annihilation

Could be a unique opportunity to observe a sharp feature in the electron spectrum (predicted in some models)

First hint of something new:results from ATIC (Nature, 2008)

PAMELA positron fraction (Nature 2009)

FERMI e+ + e- flux (2009)

FERMI All-Electron Spectrum (PRL 2009)

Electrons measured with H.E.S.S.(2009)

PAMELA

Positron fraction

Low energy charge-dependent solar modulation (see tomorrow)

High energy (quite robust) evidence of positron excess above 10 GeV

Adriani et al. , Nature 458 (2009) 607 Adriani et al., AP 34 (2010) 1 (new results)

(Moskalenko & Strong 1998) GALPROP code • Plain diffusion model • Interstellar spectra

Positron fraction

Low energy charge-dependent solar modulation (see tomorrow)

High energy (quite robust) evidence of positron excess above 10 GeV

Adriani et al. , Nature 458 (2009) 607 Adriani et al., AP 34 (2010) 1 (new results)

(Moskalenko & Strong 1998) GALPROP code • Plain diffusion model • Interstellar spectra

New positron fraction data

Using all data till 2010 and multivariate classification algorithms about factor 2 increase in positron statistics respect to published analysis

New positron flux

Antiproton flux

Largest energy range covered so far !

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Antiproton-to-proton ratio

Adriani et al. - PRL 105 (2010) 121101

Largest energy range covered so far !

New antiproton flux –> 400 GeV

Using all data till 2010 and multivariate classification algorithms40% increase in antip respect to published analysis

(Donato et al. 2009)• Diffusion model with convection and reacceleration

• Plain Diffusion Model (Ptuskin 2006)

Antiprotons Consistent with pure secondary production

Positrons Evidence for an excess

A challenging puzzle for CR physicists

Positron-excess interpretations

Dark matter

boost factor required

lepton vs hadron yield must be consistent with p-bar observation

Astrophysical processes

• known processes

• large uncertainties on environmental parameters

(Blasi 2009) e+ (and e-) produced as secondaries in the CR acceleration sites (e.g. SNR)

(Hooper, Blasi and Serpico, 2009) contribution from diffuse mature & nearby young pulsars.

(Cholis et al. 2009) Contribution from DM annihilation.

M. Cirelli et al., Nucl. Phys. B 813 (2009) 1; arXiv: 0809.2409v3

Interpretation: DM

Which DM spectra can fit the data?

DM with and dominant annihilation channel (possible candidate: Wino)

positrons antiprotons

Yes!

No!

Interpretation: DM

Which DM spectra can fit the data?

DM with and dominant annihilation channel (no “natural” SUSY candidate)

Yes!

Yes!

But B≈104

M. Cirelli et al., Nucl. Phys. B 813 (2009) 1; arXiv: 0809.2409v3

positrons antiprotons

Interpretation: DM

DM with and dominant annihilation channel

positrons

Yes!

Yes!

Yes!

M. Cirelli et al., Nucl. Phys. B 813 (2009) 1; arXiv: 0809.2409v3

antiprotons

Interpretation: DMI. Cholis et al. Phys. Rev. D 80 (2009) 123518; arXiv:0811.3641v1

Astrophysical Explanation: secondaries in SNR

P.Blasi et al., PRL 103 (2009) 051104 arXiv:0903.2794

Positrons (and electrons) produced as secondaries in the sources (e.g. SNR) where CRs are accelerated.But also other secondaries are produced: significant increase expected in the p/p and B/C ratios.

New antiproton/proton ratio 400 GeV

Overall agreement with models of pure secondary calculations for solar minimum (constraints at low and high energy for DM models!)

The solid line shows a calculation for secondary antiprotons includingan additional antiproton component produced and accelerated at cosmic-ray sources.

Astrophysical Explanation: Pulsars

Are there “standard” astrophysical explanations of the high energy positron data?

Young, nearby pulsars

Not a new idea: Boulares, ApJ 342 (1989), Atoyan et al (1995)

Geminga pulsar

Astrophysical Explanation:Pulsars

Mechanism: the spinning B of the pulsar strips e- that accelerated at the polar cap or at the outer gap emit γ that make production of e± that are trapped in the cloud, further accelerated and later released at τ ~ 105 years.

Young (T < 105 years) and nearby (< 1kpc) If not: too much diffusion, low energy, too low flux.

Geminga: 157 parsecs from Earth and 370,000 years oldB0656+14: 290 parsecs from Earth and 110,000 years

old.

Diffuse mature pulsars

Astrophysical Explanation: Pulsars

H. Yüksak et al., arXiv:0810.2784v2Contributions of e- & e+ from Geminga assuming different distance, age and energetic of the pulsar

diffuse mature &nearby young pulsars Hooper, Blasi, and Serpico arXiv:0810.1527

Mirko Boezio, Innsbruck, 2012/05/29

How to clarify the matter?C

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Positronsvs antiprotons

• Large uncertainties on propagation parameters allows to accommodate an additional component

• A p-bar rise above 200GeV is not excluded

(Donato et al. 2009)• Diffusion model with convection and reacceleration

(Blasi & Serpico 2009) • p-bar produced as secondaries in the CR acceleration sites (e.g. SNR)

consistent with PAMELA positron data

+(Kane et al. 2009)• Annihilation of 180 GeV wino-like neutralino

consistent with PAMELA positron data

(Strong & Moskalenko 1998) GALPROP code

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Theoretical uncertainties on “standard” positron fraction

T. Delahaye et al., Astron.Astrophys. 501 (2009) 821; arXiv: 0809.5268v3

γ = 3.54 γ = 3.34

Flux=A • E-

Electron energy measurements

Two independent ways to determine electron energy:

1.Spectrometer

• Most precise• Non-negligible energy losses (bremsstrahlung) above the spectrometer unfolding

2.Calorimeter

• Gaussian resolution• No energy-loss correction required

• Strong containment requirements smaller statistical sample

spectrometer

calorimeter

Adriani et al. , PRL 106, 201101 (2011)

Electron identification:• Negative curvature in the spectrometer• EM-like interaction pattern in the

calorimeter

Electron absolute flux

Largest energy range covered in any experiment hitherto with no atmospheric overburden

Low energy

• minimum solar activity ( = f 450÷550 GV)

High energy

No significant disagreement with recent ATIC and Fermi data

Softer spectrum consistent with both systematics and growing positron component

Spectrometric measurement

Adriani et al. , PRL 106, 201101 (2011)

e+ +e-

Calorimetric measurements

e-

Flux=A • E -

= 3.18 ± 0.04

PAMELA Electron & Positron Spectra

Flux=A • E-

= 3.18 ±0.04

Flux=A • E-

= 2.70 ±0.15

Preliminary

FERMI OBSERVATORY

PAMELA & FERMI

• Same trend for positrons (increasing with energy)

• Compatible spectral indexes for electrons and positrons :

PAMELA : FERMI:

= 3.18 ± 0.04 for electrons = 3.19 ± 0.07 for electrons = 2.70 ± 0.15 for positrons = 2.77 ± 0.14 for positrons

Conclusions

Electron/Positron data have opened new physics in Cosmic Rays in the last 5 years; ATIC, FERMI, PAMELA measurements all pointed towards an excess.

Evident excess in the electron and positron (and therefore in the all-electron) spectra revealed the presence of a leptonic new source;

The contemporary absence of a hadronic new source, as shown by the PAMELA antiproton data, seems to point towards a astrophysical source rather than to dark matter.

BUT ….

Conclusions

Recent rumors by AMS – not yet supported by an official paper - make us guess that the DM interpretation might play a role again.

“Big news in the search for dark matter may be coming in about two weeks”, Ting said at the annual meeting of the American Association for the Advancement of Science. “That's when the first paper of results from AMS will be submitted to a journal”.

“It will not be a minor paper" Ting said, hinting that the findings were important enough that the scientists rewrote the paper 30 times before they were satisfied with it …

Conclusions

Apart from AMS data, the new CALET mission (Japan-Italy-US) will perform high statistics measurements of electrons up to 10 TeV;

Built around a 30 r.l. calomiter, it will be mounted on the ISS in 2o14;

With its good geometrical factor, it will improve significantly the systematic uncertainties of previous calorimetric measurements.