Transcript Diapositiva 1 - Istituto Nazionale di Fisica Nucleare

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
discovered the positron
Blackett
&
Occhialini
1954:
Antimatter Chronology
“antiproton induced” events in cosmic rays (Amaldi)
Spring 1955: Pauli completed the proof of the CPT symmetry
Oct. 1955: Chamberlain, Segré,
discovered the antiproton
Wiegland
and
Ypsilantis
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:
and T
in beta
Telegdi in
Lee, Oheme and Yang proposed the possibility of CP
violation; Wu et al. discovered C and P violation
decay, while Garwin & Lederman and Friedman &
pion and muon decays
1960’s:
Antimatter Chronology
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 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 < 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
extragalactic antimatter
Stecker & Wolfendale 85
mc = 20 GeV
Stecker et al.85
mc = 15 GeV
1979
Balloon data : Positron fraction before 1990
mc=20GeV
Tilka 89
dinamic halo
leaky box
New Generation of Antimatter
Researches in Cosmic Rays
Balloon Flights
Wizard Collaboration
- MASS – 1,2 (89,91)
-TrampSI (93)
- BESS (93, 95, 97, 98, 2000)
- CAPRICE (94, 97, 98)
- Heat (94, 95, 2000)
-  Flight (2003)
- IMAX (96)
- BESS Long duration flights
(2004)
Space experiments
Technology and Physics
 SilEye-1
 SilEye-2
 AMS-01
 NINA-1
 NINA-2
 SilEye-3
 PAMELA
 AGILE
 AMS-02
 GLAST
MIR
MIR
Shuttle
Resurs
MITA
ISS
Resurs
MITA
ISS
Sat.
1995-1997
1997-2001
1998
1998
2000
2002 (April 25)
2003
2003
2006
2006
Caprice
Subnuclear physics techniques in space experiments
– Charge sign and
momentum
– Beta selection
– Z selection
– hadron – electron
discrimination
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
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 =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
•Background from normal
secondary production
•Mass91 data from
XXVI ICRC, OG.1.1.21 , 1999
•Caprice94 data from
Antiproton/proton Ratio
Distortion on the secondary antiproton flux induced by an Extragalactic
Antimatter component
Extragalactic Antimatter
Black Hole evaporation
ApJ , 487, 415, 1997
•Caprice98 data from
BESS 00
ApJ Letters 534, L177, 2000
Kinetic Energy (GeV)
Solar Field Reversal Effect
astro-ph/0109007
Mission in Progress
PAMELA MISSION
Positrons
50 MeV - 270 GeV
Antiprotons 80 MeV – 190 GeV
Limit on antinuclei ~10-8 (He /He)
GF
Mass
Dimensions
cm3
Power Budget
20.5 cm2 sr
470 Kg
120 x 40x45
360W
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.
Resurs-DK1:
TsSKB-Progress Samara
Russia
Mass: 6.7 tons
Orbit: Elliptic
Altitude: 300 - 600 Km
Inclination: 70.4°
Life Time: > 3 years
Launch foreseen in 2005
from Baikonur with Soyuz
TM rocket
2 downlink station:
Moscow and KhantyMamsyisk (Siberia)
Principle of Operation
TOP AC (CAT)
SIDE AC (CAS)
BOTTOM SCINTILLATOR (S4)
TRD
PAMELA DETECTOR
• Threshold detector : signal
from e±, no from p.
TOF
• 9 radiator planes (carbon
fiber) and straws tubes
(4mm diameter) filled with
Xe/CO2 mixture.
• Level 1 trigger
• dE/dx
• Plastic scintillator + PMT
Anticoincidence system
• Plastic scintillator + PMT
• particle identification (up
to 1GeV/c)
TRD
•102 e/p separation (E > 1
GeV/c).
• Defines tracker acceptance
ANTI
TRK
• Energy Resolution for e±
E/E = 15% / E1/2.
• Si-X / W / Si-Y structure
22 W planes
• 16.3 X0 / 0.6 l0
• Time Resolution ~ 70 ps
Si Tracker + magnet
• Permanent magnet B=0.4T
• 6 planes double sided Si
strips 300 m thick
Si-W Calorimeter
• Imaging Calorimeter :
reconstructs shower profile
discriminating e/p
Time-of-flight
• Spatial risolution ~3m
CALO
ND
• MDR = 740 GV/c
Neutron detector
• Extends the energy range
for primary protons and
electrons up to 10 TeV
• 36 3He counters in a
polyetilen moderator
PAMELA Detector
TOF
TRD
Tracker
Calorimeter
Magnet
Distortion of the secondary positron
fraction
induced by a signal from a heavy
neutralino.
Distortion of the secondary antiproton flux induc
by a signal from a heavy Higgsino-like neutralino.
standard
exotic
contribution
Energy (GeV)
Energy (GeV)
Expected data from Pamela for two years of operation are shown in
red.
P.Picozza and A.Morselli,astro-ph/0103117
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 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 cm2 sr
Duration
3 years
Altitude
320 - 390 Km
Inclination
51.7 °
Launching
2006
BESS
ANTARTICA LONG DURATION BALLOON FLIGHT
G.F.
Duration
Altitude
Latitude
Launcing
3000 cm2 sr
20 Days
36 Km
> 70°
2004