Overview of the main PAMELA physics results Oscar Adriani University of Florence & INFN Firenze 17th Lomonosov Conference Moscow, August 26th, 2015

PAMELA main physics tasks Provide new high precision data about CR primary and secondary fluxes, to put constraints on the current acceleration and diffusion models of cosmic rays in the Galaxy. Search for signatures of exotic processes connected to the Dark Matter problem; Help solving the cosmological problem about the existence of the apparent asymmetry between matter and antimatter; Investigate the heliosphere and Earth magnetosphere.

+ - PAMELA detectors Main requirements: + - 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 Overview of the apparatus PAMELA detectors Main requirements: - high-sensitivity antiparticle identification - precise momentum measurement Spectrometer microstrip silicon tracking system + permanent magnet It provides: - Magnetic rigidity  R = pc/Ze Charge sign Charge value from dE/dx GF: 21.5 cm2 sr Mass: 470 kg Size: 130x70x70 cm3 Power Budget: 360W

PAMELA Payload for Matter/antimatter Exploration and Light-nuclei Astrophysics PAMELA on board of Russian satellite Resurs DK1 Orbital parameters: inclination ~70o ( low energy) altitude ~ 360-600 km (elliptical) – now 500 km (circular) Launch from Baykonur  Launched on 15th June 2006 PAMELA in continuous data-taking mode since then! Recently celebrated 9 years!

PAMELA published results Antiproton flux + antiproton/proton ratio (100 MeV-300 GeV) Positron flux + positron/electron ratio (100 MeV-300 GeV) Electron flux (1 – 500 GeV) Proton and helium flux (1 GeV – 1.2 TeV) B/C ratio (500 MeV – 100 GeV) H and He isotope flux AntiHe/He ratio Proton flux vs. time – solar modulation (electron flux vs. time submitted) Trapped proton and antiproton flux, albedo protons SEP data (13 December 2006 and 17 May 2012 event) Positrons anisotropy (just submitted) Search for strangelets (just submitted)

e-

Absolute fluxes of primary GCRs Protons, helium nuclei, electrons

Proton and Helium Nuclei Spectra & H/He ratio First high-statistics and high-precision measurement over three decades in energy Deviations from single power law (SPL): Spectra gradually soften in the range 30÷230GV Spectral hardening @ R~235GV ~0.2÷0.3 SPL is rejected at 98% CL Origin of the hardening? (e.g. see P. Blasi, arXiv:1312.1590) - At the sources: multi-populations, etc.? - Propagation effects? Clear evidence of different H and He slopes above ~ 10 GV Adriani et al., Science 332 (2011) 6025

Global picture: PAMELA vs AMS-02 proton spectrum Solar modulation 0.988 O. Adriani et al, Phys. Rep. (2014)

Electron Spectrum Solar modulation (ICRC 2013) e- e+ + e-

Secondary cosmic rays Secondaries from homogeneously distributed interstellar matter (light nuclei) Antiparticles (antiprotons, positrons)

Boron and carbon fluxes and B/C Tuning of cosmic-ray propagation models with measurements of secondary/primary flux ratio Modelization of cosmic-ray propagation in the Galaxy Adriani et al., ApJ 791 (2014), 93

Lithium and beryllium fluxes Preliminary Shaded red area: particle slow-down effects (still to be corrected) Shaded grey area: relevant MDR effects for Be (due to saturated clusters) (still to be corrected) No MC corrections Not unfolded Only statistical errors N. Mori & E. Vannuccini et al.: “Measurement of Lithium and Beryllium cosmic-ray abundances by the PAMELA experiment” - CR 08: 01/08/2015

Li/Be Ratio Preliminary No MC corrections Not unfolded Shaded grey area: relevant MDR effects for Be (due to saturated clusters) (Still to be corrected) Preliminary No MC corrections Not unfolded Only statistical errors N. Mori & E. Vannuccini et al.: “Measurement of Lithium and Beryllium cosmic-ray abundances by the PAMELA experiment” - CR 08: 01/08/2015

Hydrogen and helium isotopes Isotopic separation with β (ToF) vs. Rigidity or multiple dE/dx (Calorimeter) vs. rigidity W. Menn et al.: “Measurement of the isotopic composition of hydrogen and helium nuclei in cosmic rays with the PAMELA experiment” - Poster 1 CR: 30/7/2015

Anti He/He and search for Strange Quark Matter No antiHe detected in a sample of 6.330.000 events with |Z|>=2,from 0.6 to 600 GV. Widest energy range ever reached Accepted by PRL No anomalous A/Z particle has been found (for Z <8 ) in the rigidity range 1 < R < 1.0 x 103 GV and mass range 4 < A < 1.2 x 105 Upper limit as a function of Baryon Number (A) set

PAMELA Antiparticle Results: Antiprotons O. Adriani et al, PRL 102 (2009) 051101; PRL 105 (2010) 121101; Phys. Rep. (2014). Secondary production calculations

Positron fraction M. Aguilar et al, PRL 110, 2013 Good agreement with FERMI and AMS data

Positron flux Clear evidence  The positron fraction increase is due to an harder positron spectrum and not to a softer electron one. Adriani et al. , PRL 111 (2013) 081102 Solar modulation In the highest bin a lower limit has been estimated with 90% confidence level, due to a possible overestimation of the proton contamination.

Positron-excess interpretations Contribution from DM annihilation. A primary positron source is certainly necessary! 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 Contribution from diffuse mature & nearby young pulsars. e+ (and e-) produced as secondaries in the CR acceleration sites (e.g. SNR)

Search for anisotropy in the positron data Submitted to AP 1489 positroni, 20673 e+ + e- 450000 protoni Significance maps for backtraced positrons in the 10 GV <R<200 GV, over the following angular scales: 10◦, 30◦, 60◦, 90◦. The significance has been computed using the protons measured as the isotropic reference sample No evidence of positrons anisotropy in PAMELA data

Cosmic rays in the heliosphere

Effect of solar activity on CR fluxes Neutron Monitor count (Data from http://cosmicrays.oulu.fi ) Effect of solar activity on CR fluxes PAMELA Cycle 23 Cycle 24 O. Adriani et al., ApJ 765 (2013), 91; M. S. Potgieter et al., Sol. Phys. (2014), 289 protons electrons increasing fluxes Decreasing solar activity PAMELA covers one solar cycle

Solar modulation: electron spectra The ratios as a function of energy between the measured half-years (e−) fluxes from January 2007 till December 2009 and the measured fluxes for the period July-November 2006 overlaid with the corresponding computed spectra (solid lines). The error bars are the quadratic sum of the statistical and systematic errors. Abbiamo provato a sovraimporre al plot di e-/e+ sotto 3 GeV ad curve di Potgieter di letteratura (Langner and Potgieter, 2004). Il risultato è in figura emeno_su_epiu_potgieter.png. Devi guardare la curva continua (A-). La corrispondenza degli andamenti è un buon punto di partenza ma ci sono margini di miglioramento considerato ad esempio che le condizioni del tilt angle del modello sono quelle del minimo solare generico, ma nel periodo in cui i dati sono stati accumulati (2006 - 2008 per quel plot) il tilt angle era circa 30°. Ci sono poi sempre le altre fonti di incertezza sul modello. C'è anche la figura della frazione di positroni. Il modello di Moskalenko tiene conto della modulazione solare ma non della charge dependence, quello della Grimani invece ne tiene conto ma in modo fenomenologico (non risolve l'equazione di trasporto ma si lascia 'guidare' da dati precedenti...mi devo rivedere i dettagli). Poi è da ricordare quello che si diceva a ottobre scorso a Villa Olmo riguardo alla possibilità di implementare in futuro in collaborazione con i sud africani la charge dependence nei modelli di trasporto più usati al momento (ricordo giusto?).  Adriani et al., submitted to ApJ

SEP events (SEP from Dec. 13, 2006) Adriani et al. - ApJ 742 102, 2011

Preliminary PAMELA SEP Spectra Completing the spectrum PAMELA bridges the gap between low energy space-based and ground-‐based measurements to obtain a complete spectrum Flux 100 MeV 1 GeV Proton Energy E. Christian et al.: “Unseen GLEs (Ground Level Events)”- SH01: 30/07/2015

Cosmic rays in the magnetosphere

Sorry, I have no time!!!! Cosmic rays in the magnetosphere

PAMELA overall results All particles PAMELA results Results span 4 decades in energy and 13 in fluxes

Summary and conclusions (1) PAMELA has been in orbit and studying cosmic rays for almost 9 years. Its operation time will continue until end 2015, possibly until end of current solar cycle. Antiproton energy spectrum and ratio  Measured up to ~300 GeV. No significant deviations from secondary production expectations. High energy positron fraction (>10 GeV)  Measured up to ~300 GeV. Increases significantly (and unexpectedly!) with energy.  Primary source? Positron flux -> Consistent with a new primary source. Anisotropy studies: no evidence of anisotropy. AntiHe/He ratio: broader energy range ever achieved.

Summary and conclusions (2) H and He absolute fluxes  Measured up to ~1.2 TV. Complex spectral structures observed (spectral hardening at ~200 GV). H and He isotope fluxes and ratio -> most complete measurements so far. Electron (e-) absolute flux Measured up to ~600 GeV. Possible deviations from standard scenario, not inconsistent with an additional electron component. B/C ratio and absolute fluxes up to 100 GeV/n. Solar physics: measurement of modulated fluxes and solar-flare particle spectra Physics of the magnetosphere: first measurement of trapped antiproton flux and detailed measurement of trapped proton flux. Other studies and forthcoming results: Primary and secondary-nuclei abundance (up to Oxygen), Solar modulation (long-term flux variation and charge-dependent effects), Solar events: several new events under study.

Backup slides

PAMELA & AMS (and Fermi) Electron (e-) Spectrum Solar modulation R. Munini et al.: “Solar modulation of galactic cosmic rays electrons and positrons over the 23rd solar minimum with the PAMELA experiment”- SH 07: 04/08/2015

Electron energy measurements Two independent ways to determine electron energy: Spectrometer Most precise Non-negligible energy losses (bremsstrahlung) above the spectrometer  unfolding Calorimeter Gaussian resolution No energy-loss correction required Strong containment requirements Adriani et al. , PRL 106 (2011) 201101 spectrometer calorimeter Electron identification: Negative curvature in the spectrometer EM-like interaction pattern in the calorimeter

Search for solar neutrons Solar neutrons can be produced by any solar event. PAMELA Neutron Detector (ND) is sensitive to neutrons fluxes coming from Sun. Search of ND counts increasing after SEP event in comparison with counts during 1 orbit before the event. Two events under study: December 13rd 2006 June 7th 2011

New article about trapped protons Differential fluxes are reported as a function of the first adiabatic invariant M, for sample values of K and L∗ invariants (equatorial region). While spectral shapes are in a good qualitative agreement, measured flux intensities result to be up to about an order of magnitude lower with respect to model predictions, depending on the phase-space region. O. Adriani et al. ApJ 799, 1, L4 (2015)

Light Nuclei and Isotopes Tuning of cosmic-ray propagation models with measurements of secondary/primary flux ratio 2H/1H and 3He/4He are complementary to B/C measurements in constraining propagation models (Coste et al., A&A 539 (2012) A88)

Boron and carbon fluxes and B/C Tracking performance: σx = 14 μm, σy = 19 μm MDR = 250 GV Modelization of cosmic-ray propagation in the Galaxy Adriani et al., ApJ 791 (2014), 93

South-Atlantic Anomaly (SAA) 39

South-Atlantic Anomaly (SAA) SAA morphology Latitude Altitude Longitude Neutron rate SAA 40

Geomagnetically trapped antiprotons First measurement of p-bar trapped in the inner belt 29 p-bars discovered in SAA and traced back to mirror points p-bar flux exceeds GRC flux by 3 orders of magnitude, as expected by models O. Adriani et al., ApJL 737 (2011), L29

The PAMELA collaboration Bari Florence Frascati Italy: Trieste Naples Rome CNR, Florence Moscow St. Petersburg Russia: Germany: Siegen Sweden: KTH, Stockholm

Global picture: PAMELA vs AMS-02 helium nuclei spectrum Solar modulation 1.036

Lithium and Beryllium Isotopes β (ToF) vs. Rigidity or Multiple dE/dx (Calorimeter) vs. rigidity Lithium Beryllium Ratio 7Li / 6Li 7Be / (9Be + 10Be) W. Menn et al. : “Lithium and Beryllium Isotopes in the PAMELA experiment” - CR08:01/08/2015

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 Other hypotheses possible and under study (i.e. Minimal DM Model, decaying DM, new gauge bosons, …) Astrophysical processes Local pulsars are well-known sites of e+e- pair production:  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 LKP -- M= 300 GeV (Hooper & Profumo 2009) More than 150 articles claim DM is discovered !

Searching for a positron excess in the direction of the sun Submitted to AP No evidence of positron excess in the direction of the sun

Completing the spectrum PAMELA bridges the gap below ACE, GOES and many others and above the Neutron Monitors to obtain a complete spectrum 2012 January 27th 2012 January 23rd 2012 March 7th 2012 May 17th