High energycosmic rays Roberta Sparvoli Rome “Tor Vergata”University and INFN, ITALY Nijmegen 2012
Lecture # 1 :outline COSMIC RAY science DIRECT MEASUREMENTS OF CR’S BALLOON EXPERIMENTS
The discovery of cosmicrays • Victor Hess ascended to 5000 m in a balloon in 1912 • ... and noticed that his electroscope discharged more rapidly as altitude increased • Not expected, as background radiation was thought to be terrestrial. Extraterrestrial origin, confirming previous hints by Theodore Wulf and DomenicoPacini Kolhorster 1914
Astroparticlephysics in spaceisperformed by the detection and analysis of the properties of CosmicRays. The primaryCosmicRaysreach the top of the atmosphere, withoutinteracion. The atmosphereactsas a convertor: the interaction of the CR’s with the nuclei in atmosphereproducesshowers of secondaryparticles (secondaryCosmicRays). The primaryradiation can be studieddirectlyonlyabove the terrestrialatmosphere. The primarycosmicradiationisaffected by the effect of the Solar System magneticfields: the Earth’smagneticfield and the Solar magneticfield. Primary and secondary CR’s
Primary cosmic ray ~500 km Smaller detectors but long duration. PAMELA! ~40 km Top of atmosphere Large detectors but short duration. Atmospheric overburden ~5 g/cm2. Almost all data on cosmic antiparticles from here. ~5 km 0 m Ground
Charged component Protons (85%) Nuclei & isotopes (12% He, 1% heavy nuclei) Electrons (2%) Antimatter: antiprotons (p/p~10-4) positrons (e+/e++e-~10-1) antideuterons ? antinuclei ? The composition of CR’s Neutral component Gamma rays Neutrons Neutrinos (not “real” CR) The neutral component points to the source!
How to measurecosmicrays • Directly, E<1014 eV • High Z particles • Antiparticles • Light Nuclei and isotopes • Composition below the knee • Indirectly, E>1014eV • Compositionat the knee • UHECR • (Castellina’s talk)
A B C
Measurementof primary and secondaryCR elements A • Fundamentalquestionsremainunsolved: • GCR sources? • GCR composition? • GCR accelerationsites? • GCR diffusion in the Galaxy? • The effectivepossibility to disentangleexoticsignal from pure secondary production dependsstrongly on the precise knowledge of the parameterswhichregulate the production and diffusionof cosmicrays in the Galaxy.
What do we know up to now? • GCR material ejected in Supernova explosions (Remnants), the best candidate for CR sources from the energetic point of view (not yet the smoking gun…); • GCR accelerated via DSA (First Order Fermi acceleration) mechanism at the shock wave front propagating into the ISM, up to roughly 1015eV; • Power-law energy spectrum expected (E-a); • GCR diffuse in the Galaxy, lose energy, interact, can be reaccelerated, escape from the Galaxy …. Power-law energy spectrum expected (E-(a+d)); • Not much known about extra-Galactic CR.
Present situation of the B/C critical ratio: Boron/Carbon ratio δ: 0.3 0.45 0.6 0.7 0.85 DIFFERENT diffusioncoefficients : K(E)= K0R Courtesy of F. Donato
Antiproton flux B/C Ratio AstrophysicB/C constraints Nuclear cross sections!! Secondaries/primaries i.e. Boron/ Carbon to constrain propagation parameters F. Donato et.al, ApJ, 563, 172, 2001 [astro-ph/0103150] D. Maurin, F. Donato R. Taillet and P.Salati ApJ, 555, 585, 2001 [astro-ph/0101231]
Continuity from direct measurements to extensive air showers Measurements in the knee region: Normalization of spectrum Composition Energy content Transition from galactic to extragalactic spectrum? Physicsaround the knee
A & B galactic components + extra-galactic Hillas, J.Phys.G 31 (2005) R95-131 B E-G A
The study of primary electrons is especially important because they give information on the nearest sources of cosmic rays. Electrons with energy above 100 MeV rapidly loss their energy due to synchrotron radiation and inverse Compton processes. The discovery of primary electrons with energy above 1012 eV will evidence the existence of cosmic ray sources in the nearby interstellar space (r300 pc). High Energy electrons
Vela 10,000 years 820 ly Chandra Anisotropy ROSAT Cygnus Loop 20,000 years 2,500 ly Monogem 86,000 years 1,000 ly • Possible Nearby Sources • T< 105 years • L< 1 kpc Purposes of Electron Observations Search for the signature of nearby HE electron sources (believed to be SNR) in the electron spectrum above ~ TeV Search for anisotropy in HE electron flux as an effect of the nearby sources. Precise measurement of electron spectrum above 10 GeV to define a model of accele- ration and propagation. Observation of electron spectrum in 1~10 GeV for study of solar modulation W=1048 erg/SN I(E)=I0E-α Ｎ=1/30yr D=D0(E/TeV)0.3
“We must regarditrather an accidentthat the Earth and presumably the whole Solar System contains a preponderance of negative electrons and positive protons. Itisquitepossiblethat for some of the starsitis the other way about” Dirac Nobel Speech (1933) The antimatterissue B
The earlyUniversewas a hot expanding plasma with equalnumber of baryons, antibaryons and photons. In thermalequilibrium the two-ways reactionwas: B + anti-B g + g As the Universeexpands, the density of particles and antiparticlesfalls, annihilationprocessceases, effectivelyfreezing the ratio: - baryon/photon = antibaryon/photon ~ 10-18. - Annihilationcatastrophe. Instead, in the presentrealUniverse: Baryon/photon (eqv. to BAU) ~ 6 * 10-10 (from directobserv. of light elements& microwave background); Antibaryon/baryon < 10-4. Simple Big Bang Model
Sakharovcriteria • To account for the predominance of matter over antimatter, Sakharov (1967) pointed out the necessaryconditions: • B violatinginteractions(otherwise B=0 remains); • Non-equilibriumsituation (otherwiseall status remainconstant, so B=o remains); • CP and C violation(otherwisebaryonaymmetricprocesseswould be compensated by antibaryonasymmetricones); Bariogenesys (Leptogenesys) ? GUT theories? (notworking) The processes really responsible are not presently understood!
Indirect -> By measuring the spectrum of the Cosmic Diffuse Gamma emission By searching for distortions of the CosmicMicrowave Background Direct -> By searching for Antinuclei By measuring anti-p and e+energyspectra Whatabout the observations?
Osservation in the 100 MeV gamma range Leadingprocess: pp0+ ……… Otherprocesses: pp+……… μ+……… e+……… γ1-10 MeV e+e- 0.511 MeV Gamma Evidence for CosmicAntimatter?Steigman 1976, De Rujula 1996, Dolgov 2007
Cosmic Diffuse Gamma P. Sreekumar et al, astroph/9709257
On a wide scale, thereisno evidence for the intense g-ray and X-rayemissionthatwouldfollowannihilation of matter in distantgalaxies with clouds of antimatter: Antimatter/Matterfractionlimit: In Galacticmolecularclouds: f<10-15 In Galactic Halo: f< 10-10 In local clusters of galaxies: f<10-5 Antimatter must be separated from matteratscalesatleastas100 Megaparsec Indirectsearches: antimatter/matterfractionlimits
Antiprotons: DETECTED! secondary production Direct searches: current status • PCR+HISM • PCR+HeISMp + anti-psecondary antiprotons • aCR+HISM • aCR+HeISM Positrons: DETECTED! secondary production • PCR+ ISM • NCR+ISMp+ -> m+ -> e+secondary positrons Anti-nuclei: neverdetected ! Theywould be the realsignature of antistarsbecausetheir production by “spallation” isnegligible
Evidence for the existence of an unseen, “dark”, component in the energydensity of the Universecomes from severalindependentobservationsatdifferentlengthscales: CMB Large Scale Structure Rotationcurves of galaxies SN Ia Galaxy clusters Lensing Bertone, Hooper & Silk, hep-ph/0404175, Bergstrom, hep-ph/0002126, Jungman et al, hep-ph/9506380 Dark Matter searches C
tot = 1.0030.010 m ~ 0.22 [b=0.04] ~ 0.74 Most of matter of non-baryonic nature and therefore “dark” ! The “Concordance Model” of cosmology The “concordance model” of big bang cosmologyattempts to explaincosmicmicrowave backgroundobservations, aswellaslarge scale structureobservations and supernovaeobservations of the acceleratingexpansion of the universe.
Different data: WD supernovae CMB Mattersurveys allagree atonepoint
Dark matter candidates • 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 • MirrorMatter • Champs (charged DM) • D-matter • Cryptons • Self-interacting • Superweaklyinteracting • Braneworld DM • Heavy neutrino • NEUTRALINO • Messenger States in GMSB • Branons • Chaplygin Gas • Split SUSY • Primordial Black Holes L. Roszkowski
Neutralino as the CDM candidate Linear combination of the neutralgaugebosonsB and W3 and the neutralhiggsinosH1 and H2. The neutralinois a good candidate because: • Stable (if R-parity is conserved) • Mass: mc~ 10-1000 GeV • Non-relativistic at decoupling CDM • Neutral & colourless • Weakly interacting (WIMP) • Good relic density
SIGNALS from RELIC WIMPs For a review, see i.e. Bergstrom hep-ph/0002126 • Direct searches:elasticscattering of a WIMP off detector nuclei • Measure of the recoilenergy Indirect detection:in cosmic radiation • signals due to annihilation of accumulatedcc 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 n and gkeepdirectionality can be detectedonlyifemitted from high cdensityregions Chargedparticles diffuse in the galactichalo antimattersearchedas rare components in cosmicrays
Neutralino annihilation Production takes place everywhere in the halo!! The presence of neutralino annihilation willdestort the positron, antiproton and gamma energyspectrumfrompurelysecondary production
Another possible scenario: KK Dark Matter Bosonic Dark Matter: fermionic final states no longer helicity suppressed. e+e- final states directly produced. Lightest Kaluza-Klein Particle (LKP): B(1) As in the neutralino case there are 1-loop processes that produces monoenergetic γ γ in the final state.
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) Kaluza-Klein Dark Matter in e+e-
DIRECT MEASUREMENTS OF HIGH ENERGY COSMIC RAYS
Mainphysicsresearchlines According to the physics line, different platforms and detections techniques have been adopted.
The antimatter balloon flights: overview Aim of the activityis the detection of antimatter and dark mattersignals in CR nei RC (antiprotons, positrons, antinuclei) for energies from hundreds of MeV to about 30 GeV, and measurements of primary CR from hundreds of MeV to about 300 GeV. 6 flights from the WIZARD collaboration: MASS89, MASS91, TRAMP-SI, CAPRICE 94, 97, 08. The flightsstarted from New Mexico or Canada, with differentgeomagneticcut-offs to optimize the investigation of differentenergyregions. The flightslastedabout 20 hours. 4 flights from the HEAT collaboration: 2 HEAT-e+, in 1994 and 1995, and 2 HEAT-pbarflights, in 2000 and 2002
Charge sign and momentum determination; • Beta selection • Z selection • hadron – electron discrimination CAPRICE-94
Results from MASS/TrampSI/CAPRICE/HEAT: Positrons& antiprotons Excess ?? Highestenergeticpointsavailable from balloons
The BESS program The BESS programhad11 successfulflightcampaignssince1993 up to 2008. Aim of the programisto search for antimatter (antip, antiD) and to provide high precisionp, He, mspectra. A modification of the BESS instrument, BESS-Polar, issimilar in design to previous BESS instruments, butiscompletely new with an ultra-thinmagnet and configured to minimize the amount of material in the cosmicraybeam, so as to allow the lowestenergymeasurements of antiprotons. BESS-Polarhas the largestgeometryfactor of any balloon-bornemagnetspectrometercurrentlyflying (0.3 m2-sr).
High Energy Accelerator Research Organization(KEK) The University of Tokyo Kobe University Institute of Space and Astronautical Science/JAXA BESS Collaboration National Aeronautical and Space Administration Goddard Space Flight Center BESS Collaboration University of Maryland University of Denver (Since June 2005)
BESS Detector JET/IDC Rigidity Rigidity measurement SC Solenoid (L=1m, B=1T) Min. material (4.7g/cm2) Uniform field Large acceptance Central tracker Drift chambers (Jet/IDC) d ~200 mm Z, m measurement R,b --> m = ZeR1/b2-1 dE/dx --> Z TOF b, dE/dx √