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 matterc) Present experimental observations

• Future developments and prospects

Antimatter Chronology1930: 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 Chronology1954: “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 KL 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 Chronology1960’s: Baryon Symmetric Cosmologies (Klein, Alfven…)

1964: Cronin and Fitch discovered the CP violation in KL 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 - 1960’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.

• 1965 : 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 ~ 10-18. - Annihilation catastrophe.

The present real Universe• Baryon/photon ~ 10-9 . 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 < 10-30 of the mass of the Galaxy. (Kolb and Turner)

• The simple Big Bang model does not work.• 1964: CP Violation in Nature

Sakharov’s Conditionsfor 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 < 10-5 in 10-8 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/9709257

Antimatter/Matter fraction limits

Antimatter/Matter fraction limit:

• In Galactic molecular clouds: f<10-15

• In Galactic Halo: f< 10-10

• 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=20GeVTilka 89

New Generation of AntimatterResearches in Cosmic Rays

Balloon Flights

-- BESS (93, 95, 97, 98, BESS (93, 95, 97, 98,

2000)2000)

-- Heat (94, 95, 2000) Heat (94, 95, 2000)

-- IMAX (96) IMAX (96)

-- BESS Long duration flights BESS Long duration flights

(2004)(2004)

Wizard Collaboration

- - MASS – 1,2 (89,91)MASS – 1,2 (89,91)

--TrampSI (93)TrampSI (93)

-- CAPRICE (94, 97, 98) CAPRICE (94, 97, 98)

-- Flight (2003)Flight (2003)

Space experimentsTechnology and Physics

SilEye-1 MIR 1995-1997SilEye-2 MIR 1997-2001AMS-01 Shuttle 1998NINA-1 Resurs 1998NINA-2 MITA 2000SilEye-3 ISS 2002 (April 25) PAMELA Resurs 2003 AGILE MITA 2003 AMS-02 ISS 2006GLAST Sat. 2006

– Charge sign and momentum

– Beta selection– Z selection– hadron – electron

discrimination

CapriceSubnuclear 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/0109007, PRL in

press)ANTIPROTON IDENTIFICATION PLOTS

HEAT

AMSAlpha Magnetic Spectrometer

STS91 Mission June 2-12, 1998Italy(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 =10-14

• AntiIron/Iron =10-56

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.1.1.21 , 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.1.1.21 , 1999

•Caprice94 data from ApJ , 487, 415, 1997

•Caprice98 data from ApJ Letters 534, L177, 2000

Extragalactic Antimatter

Black Hole evaporation

Ant

ipro

ton/

prot

on R

atio

Kinetic Energy (GeV)

BESS 00

astro-ph/0109007

Solar Field Reversal Effect

Mission in Progress

PAMELA MISSION

Positrons 50 MeV - 270 GeV

Antiprotons 80 MeV – 190 GeV

Limit on antinuclei ~10-8 (He /He)

Electrons 50 MeV – 3TeV

Protons 80 MeV – 700 GeV

Nuclei < 200 GeV/n (Z < 6)

Electron and proton components up to 10 TeV

study of the solar modulation after the 23rd solar cycle maximum.

GF 20.5 cm2 srMass 470 KgDimensions 120 x 40x45 cm3

Power Budget 360W

Resurs-DK1: TsSKB-Progress Samara

RussiaMass: 6.7 tonsOrbit: EllipticAltitude: 300 - 600 KmInclination: 70.4° Life Time: > 3 years Launch foreseen in 2005 from Baikonur with Soyuz TM rocket2 downlink station: Moscow and Khanty-Mamsyisk (Siberia)

Principle of Operation

TOP AC (CAT)

SIDE AC (CAS)

BOTTOM SCINTILLATOR (S4)

TRDTRD

TRD

• Threshold detector : signal from e±, no from p.

• 9 radiator planes (carbon fiber) and straws tubes (4mm diameter) filled with Xe/CO2

mixture.

•102 e/p separation (E > 1 GeV/c).

TRKTRKSi Tracker + magnet

• Permanent magnet B=0.4T

• 6 planes double sided Si strips 300 m thick

• Spatial risolution ~3m

• MDR = 740 GV/c

TOFTOF Time-of-flight

• Level 1 trigger

• particle identification (up to 1GeV/c)

• dE/dx

• Plastic scintillator + PMT

• Time Resolution ~ 70 ps

CALOCALO

Si-W Calorimeter

• Imaging Calorimeter : reconstructs shower profile discriminating e/p

• Energy Resolution for e± E/E = 15% / E1/2.

• Si-X / W / Si-Y structure

22 W planes

• 16.3 X0 / 0.6 l0

ANTIANTIAnticoincidence system

• Defines tracker acceptance

• Plastic scintillator + PMT

NDND

Neutron detector

• Extends the energy range for primary protons and electrons up to 10 TeV

• 36 3He counters in a polyetilen moderator

PAMELA DETECTOR

PAMELA DetectorTOF

CalorimeterMagnet

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/0103117

standard

Energy (GeV)Energy (GeV)

exoticcontribution

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: 320-390 Km

Inclination: 51.7°

p+ up to several TeVp- up to 200 GeVe- up to O( TeV TeV)e+ up to 200 GeVHe,….C up to several TeVanti – He…C up to O( TeV TeV) up to 100 GeVLight Isotopes up to 20 GeVG.F. 5000 cm2 srDuration 3 yearsAltitude 320 - 390 KmInclination 51.7 °Launching 2006

BESS

ANTARTICA LONG DURATION BALLOON FLIGHT

G.F. 3000 cm2 srDuration 20 DaysAltitude 36 KmLatitude > 70°Launcing 2004