Antimateria Lezioni di Fisica delle Astroparticelle Piergiorgio Picozza

Dirac Nobel Speech (1933) “We must regard it rather an accident that the Earth and presumably the whole Solar System contains a preponderance of negative electrons and positive protons. It is quite possible that for some of the stars it is the other way about” Earliest example of the interplay of particles physics and cosmology

Antimatter What is the role of matter and antimatter in the early Universe? Is the present Universe baryon-symmetric or baryon asymmetric?

Outlines The antimatter component of cosmic rays: a) Cosmological models b) Antimatter and dark matter c) Present experimental observations Future developments and prospects

Antimatter Chronology 1930: Dirac identified the holes in the energy sea of electrons as protons 1930: Weyl formulated the charge conjungation symmetry C 1931: Dirac accepted the C symmetry as a first principle, and defined positrons” the holes, predicting the existence of the first “antiparticle” 1932:Anderson and independently Blackett & Occhialini discovered the positron

Antimatter Chronology 1954: “antiproton induced” events in cosmic rays (Amaldi) Spring 1955: Pauli completed the proof of the CPT symmetry Oct. 1955:Chamberlain, Segré, Wiegland and Ypsilantis discovered the antiproton May 1956:Lee and Yang suggested the violation of P and C symmetries for weak interactions July 1956: Lederman et al. discovered the K L state Oct. 1956: Piccioni et al. discovered the antineutron Jan. 1957: Lee, Oheme and Yang proposed the possibility of CP and T violation; Wu et al. discovered C and P violation in beta decay, while Garwin & Lederman and Friedman & Telegdi in pion and muon decays

Antimatter Chronology 1960’s: Baryon Symmetric Cosmologies (Klein, Alfven…) 1964:Cronin and Fitch discovered the CP violation in K L decay 1965:Zichichi et al. discovered the antideuteron at CERN, Ting et al. at Brookhaven 1967: Sakharov conditions 1970’s: Baryon Symmetric Cosmologies (Steckher…) 1970’s: gamma ray “evidence” 1979: discovery of antiprotons in cosmic rays (Bogomolov,Golden) 1996:discovery of the first antiatom (antihydrogen) at CERN ???: antinuclei in cosmic rays ( Pamela?, AMS02?)

Antimatter on a Cosmological Scale?

Pre Big-Bang models 1930’s ’s: Universe baryonic symmetric as implied by the rigorous symmetry of the fundamental laws of the nature. Problem of separating M and M on large scale : Discovery of the cosmic background radiation.

Simple Big Bang Model The early Universe was a hot expanding plasma with equal number of baryons, antibaryons and photons. As the Universe expands, the density of particles and antiparticles falls, annihilation process ceases, effectively freezing the ratio: - baryon/photon ~ Annihilation catastrophe. The present real Universe Baryon/photon ~ From microwave background.

Simple Big Bang Model No clear mechanism to separate matter and antimatter. Statistical fluctuation in density to avoid the annihilation catastrophe and provide for regions of matter and antimatter gives: Mobject < of the mass of the Galaxy. (Kolb and Turner) The simple Big Bang model does not work. 1964: CP Violation in Nature

Sakharov’s Conditions for Baryogenesis JETP Lett., 5 (1967) 24 Baryon Number is not conserved. Charge Coniugation Symmetry is not exact. CP is not an exact symmetry. Baryogenesis could have occurred during a period when the Universe was not in thermal equilibrium.

Asymmetric Universe? The Sakarov conditions enable the existence of a baryon-asymmetric Universe, If CP violation is built into the Lagrangian, the sign of violation would be universal. Only matter, as we are. but also: They offer a solution for the separation of matter and antimatter in a baryonic symmetric scenario.

A Symmetric Universe The sign of CP violation needs non have been universal if it arises from spontaneous symmetry breaking. When the CP violation occurred in the early Universe, it is possible there may have occurred domains of space dominated by matter and other dominated by antimatter. (Brown, Stecker and Sato). Inflation might lead to domains of astronomical dimension. (Sato)

Some conclusions The theory needed to support a Baryon Asymmetric Universe is not complete Our present understanding does not forbid Baryon Symmetry The observed M - M Asymmetry M/M < in of the Universe could be a LOCAL phenomenon

Observations Indirect. By measuring: The distortion of the CBR spectrum The spectrum of the Cosmic Diffuse Gamma (GDG) Direct: By searching for Antinuclei By measuring p and e + energy spectra

Gamma Evidence for Cosmic Antimatter? Steigman 1976, De Rujula 1996 Osservation in the 100 MeV gamma range Assumptions: Matter and antimatter well mixed Leading process: p p  0 + ……. 

Cosmic Diffuse Gamma Background P. Sreekumar et al, astroph/

Antimatter/Matter fraction limits Antimatter/Matter fraction limit: In Galactic molecular clouds: f< In Galactic Halo: f< In local clusters of galaxies: f<10 -5 Antimatter must be separated from matter at scales at least as 20 Megaparsec

New limits Supercluster of Galaxies: f<10 -3,10 -4 Wolfendale Cohen, De Rujula and Glashow: the signal expected from annihilation near boundaries of regions of matter and antimatter exceeds observational limits, unless the matter domain we inhabit is virtually the entire visible universe.

Cosmic Radiation? Observation of cosmic radiation hold out the possibility of directly observing a particle of antimatter which has escaped as a cosmic rayy from a distant antigalaxy, traversed intergalactic space filled by turbulent magnetic field, entered the Milky Way against the galactic wind and found its way to the Earth. High energy particle or antinuclei

Balloon data : Antiproton/proton ratio before 1990 m  =  20 GeV Stecker et al.85 extragalactic antimatter Stecker & Wolfendale 85 m  =  15 GeV 1979

Balloon data : Positron fraction before 1990 leaky box dinamic halo m  =20GeV Tilka 89

New Generation of Antimatter Researches in Cosmic Rays

Balloon Flights - BESS (93, 95, 97, 98, 2000) - Heat (94, 95, 2000) - IMAX (96) - BESS Long duration flights (2004) Wizard Collaboration - MASS – 1,2 (89,91) - TrampSI (93) - CAPRICE (94, 97, 98) -  Flight (2003)

Space experiments Technology and Physics SilEye-1MIR SilEye-2 MIR AMS-01Shuttle 1998 NINA-1 Resurs 1998 NINA-2MITA 2000 SilEye-3 ISS 2002 (April 25)  PAMELAResurs 2003  AGILE MITA 2003  AMS-02 ISS 2006  GLAST Sat. 2006

–Charge sign and momentum –Beta selection –Z selection –hadron – electron discrimination Caprice Subnuclear physics techniques in space experiments SUPER CONDUCTING MAGNET

Antiprotons

Positron

BASIC STRUCTURE of BESS

Particle identification (p selection) (Y.Asaoka and Y.Shikaze et al., astro-ph/ , PRL in press) ANTIPROTON IDENTIFICATION PLOTS

HEAT

AMS Alpha Magnetic Spectrometer STS91 Mission June 2-12, 1998 Italy(INFN), China, Germany, Finland, France, Switzerland, Taiwan, US

Search for Heavy Antinuclei Gamma ray observations place strong limitations on antimatter in our Galaxy and in the local cluster of galaxies within 20 Mpc and further. High-energy Antinuclei from antimatter domains beyond the gamma limits. Antihelium/Helium from cosmic ray collision = AntiIron/Iron = Necessity of an excellent identification capability

ANTIMATTER LIMITS

ANTIPROTRON

Antiprotons sources Secondary production by inelastic scattering on ISM Extragalactic sources Primordial black holes produced very early in the hot Big-Bang Annihilation or decaying of dark matter remnants in the halo of our Galaxy

Distortion on the secondary antiproton flux induced by an Extragalactic Antimatter component Background from normal secondary production Mass91 data from XXVI ICRC, OG , 1999 Caprice94 data from ApJ, 487, 415, 1997 Caprice98 data from ApJ Letters 534, L177, 2000 Extragalactic Antimatter Black Hole evaporation

Distortion on the secondary antiproton flux induced by an Extragalactic Antimatter component Background from normal secondary production Mass91 data from XXVI ICRC, OG , 1999 Caprice94 data from ApJ, 487, 415, 1997 Caprice98 data from ApJ Letters 534, L177, 2000 Extragalactic Antimatter Black Hole evaporation Antiproton/proton Ratio Kinetic Energy (GeV) BESS 00

astro-ph/ Solar Field Reversal Effect

Mission in Progress

PAMELA MISSION Positrons50 MeV GeV Antiprotons80 MeV – 190 GeV Limit on antinuclei ~10 -8 (He /He) Electrons50 MeV – 3TeV Protons80 MeV – 700 GeV Nuclei< 200 GeV/n (Z < 6) Electron and proton components up to 10 TeV study of the solar modulation after the 23 rd solar cycle maximum. GF 20.5 cm 2 sr Mass 470 Kg Dimensions 120 x 40x45 cm 3 Power Budget 360W

Resurs-DK1: TsSKB-Progress Samara Russia Mass: 6.7 tons Orbit: Elliptic Altitude: Km Inclination: 70.4° Life Time: > 3 years Launch foreseen in 2005 from Baikonur with Soyuz TM rocket 2 downlink station: Moscow and Khanty- Mamsyisk (Siberia)

Principle of Operation TOP AC (CAT) SIDE AC (CAS) BOTTOM SCINTILLATOR (S4)

TRD TRD Threshold detector : signal from e ±, no from p. 9 radiator planes (carbon fiber) and straws tubes (4mm diameter) filled with Xe/CO 2 mixture e/p separation (E > 1 GeV/c). TRK Si Tracker + magnet Permanent magnet B=0.4T 6 planes double sided Si strips 300  m thick Spatial risolution ~3  m MDR = 740 GV/c TOF Time-of-flight Level 1 trigger particle identification (up to 1GeV/c) dE/dx Plastic scintillator + PMT Time Resolution ~ 70 ps CALO Si-W Calorimeter Imaging Calorimeter : reconstructs shower profile discriminating e/p Energy Resolution for e ±  E/E = 15% / E 1/2. Si-X / W / Si-Y structure 22 W planes 16.3 X 0 / 0.6 l 0 ANTI Anticoincidence system Defines tracker acceptance Plastic scintillator + PMT ND Neutron detector Extends the energy range for primary protons and electrons up to 10 TeV 36 3 He counters in a polyetilen moderator PAMELA DETECTOR

PAMELA Detector TOF Calorimeter Magnet TRD Tracker

Expected data from Pamela for two years of operation are shown in red. Distortion of the secondary positron fraction induced by a signal from a heavy neutralino. Distortion of the secondary antiproton flux induced by a signal from a heavy Higgsino-like neutralino. P.Picozza and A.Morselli,astro-ph/ standard Energy (GeV) exotic contribution

ANTIMATTER LIMITS

PAMELA MISSION INFN ( Trieste, Florence, LNF, Roma II, Naples, Bari) KTH Stockholm (Sweden) University of Siegen (Germany) MEPHI and Lebedev, Moscow (Russia) FIAN, St Petersburg (Russia) NASA GSFC, Greenbelt (USA) NMSU, Las Cruces (USA)

AMS Altitude: Km Inclination: 51.7°

p + up to several TeV p - up to 200 GeV e - up to O( TeV TeV) e + up to 200 GeV He,….C up to several TeV anti – He…C up to O( TeV TeV)  up to 100 GeV Light Isotopes up to 20 GeV G.F.5000 cm 2 sr Duration 3 years Altitude Km Inclination 51.7 ° Launching 2006

BESS ANTARTICA LONG DURATION BALLOON FLIGHT G.F.3000 cm 2 sr Duration20 Days Altitude36 Km Latitude > 70° Launcing2004