High energy cosmic rays ROBERTA SPARVOLI ROME “TOR VERGATA” UNIVERSITY AND INFN, ITALY Nijmegen 2012

High energy cosmic rays

R O B E R TA S PA RV O L IR O M E “ TO R V E R G ATA ” U N I V E R S I T Y

A N D I N F N , I TA LY

Nijmegen 2012

COSMIC RAY SCIENCE DIRECT MEASUREMENTS OF CR’S

BALLOON EXPERIMENTS

Lecture # 1 : outline

Click to edit Master text styles

• 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 Domenico Pacini

Kolhorster 1914

The discovery of cosmic rays


The CR spectrum


Structures in the CR spectrum


Primary and secondary CR’sAstroparticle physics in space is performed by the detection and analysis of the properties of Cosmic Rays.

The primary Cosmic Rays reach the top of the atmosphere, without interacion. The atmosphere acts as a convertor: the interaction of the CR’s with the nuclei in atmosphere produces showers of secondary particles (secondary Cosmic Rays).

The primary radiation can be studied directly only above the terrestrial atmosphere.

The primary cosmic radiation is affected by the effect of the Solar System magnetic fields: the Earth’s magnetic field and the Solar magnetic field.


0 m

~40 km

~500 km

~5 km

Top of atmosphere

Ground

Primary cosmic ray

Smaller detectors but long duration. PAMELA!

Large detectors but short duration. Atmospheric overburden ~5 g/cm2. Almost all data on cosmic antiparticles from here.


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 measure

cosmic rays Directly, E<1014 eV

• High Z particles• Antiparticles• Light Nuclei and isotopes• Composition below the

knee

Indirectly, E>1014 eV• Composition at the knee• UHECR

(Castellina’s talk)


A

BC


Fundamental questions remain unsolved: GCR sources? GCR composition? GCR acceleration sites? GCR diffusion in the Galaxy?

The effective possibility to disentangle exotic signal from pure secondary production depends strongly on the precise knowledge of the parameters which regulate the production and diffusion of cosmic rays in the Galaxy.

Measurement of primary and secondary CR elementsA


e-


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 1015 eV;

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.


Boron/Carbon ratio

Present situation of the B/C critical ratio:

δ:

0.3

0.45

0.6

0.7

0.85

DIFFERENT diffusion coefficients : K(E)= K0R

Courtesy of F. Donato


Secondaries/primaries i.e. Boron/ Carbon to constrain propagation parameters

D. Maurin, F. Donato R. Taillet and P.Salati ApJ, 555, 585, 2001 [astro-ph/0101231]

F. Donato et.al, ApJ, 563, 172, 2001 [astro-ph/0103150]

AstrophysicB/C

constraints

Nuclear cross

sections!!

B/C Ratio Antiproton flux


Physics around the knee

• 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?

A & B galactic components + extra-galactic Hillas, J.Phys.G 31 (2005) R95-131


High Energy electrons

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).

Purposes of Electron Observations

Cygnus Loop20,000 years2,500 ly

Monogem86,000 years1,000 ly

Vela 10,000 years820 ly

Chandra

ROSAT

・CALET

Vela

近傍ソースの検出-エネルギースペクトル-到来方向の異方性

超新星における衝撃波加速加速機構と拡散過程超新星の頻度、分布

太陽変調

Anisotropy

W=1048 erg/SNI(E)=I0E-α

Ｎ =1/30yrD=D0(E/TeV)0.3

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

Possible Nearby Sources• T< 105 years• L< 1 kpc


The antimatter issue

“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”

Dirac Nobel Speech (1933)

B


Simple Big Bang ModelThe early Universe was a hot expanding plasma with equal number of baryons, antibaryons and photons. In thermal equilibrium the two-ways reaction was:

B + anti-B g + g

As the Universe expands, the density of particles and antiparticles falls, annihilation process ceases, effectively freezing the ratio:

- baryon/photon = antibaryon/photon ~ 10-18. - Annihilation catastrophe.

Instead, in the present real Universe: Baryon/photon (eqv. to BAU) ~ 6 * 10-10 (from direct observ. of light elements & microwave background);Antibaryon/baryon < 10-4.


Sakharov criteria

To account for the predominance of matter over antimatter, Sakharov (1967) pointed out the necessary conditions:

• B violating interactions (otherwise B=0 remains);

• Non-equilibrium situation (otherwise all status remain constant, so B=o remains);

• CP and C violation (otherwise baryon aymmetric processes would be compensated by antibaryon asymmetric ones);

The processes really responsible are not presently understood!

GUT theories ?

(not working)

Bariogenesys (Leptogenesys) ?


What about the observations?Indirect ->

• By measuring the spectrum of the Cosmic Diffuse Gamma emission

• By searching for distortions of the Cosmic Microwave Background

Direct ->• By searching for Antinuclei• By measuring anti-p and e+ energy

spectra


Gamma Evidence for Cosmic Antimatter?

Steigman 1976, De Rujula 1996, Dolgov 2007

Osservation in the 100 MeV gamma range

Leading process:p p 0+ ………

Other processes:p p +……… μ+……… e+……… γ 1-10 MeVe+e- 0.511 MeV


Cosmic Diffuse Gamma

P. Sreekumar et al, astroph/9709257


Indirect searches: antimatter/matter fraction limits

On a wide scale, there is no evidence for the intense g-ray and X-ray emission that would follow annihilation of matter in distant galaxies with clouds of antimatter:

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 100 Megaparsec


Direct searches: current status

PCR+HISM

PCR+HeISM p + anti-p

secondary antiprotonsaCR+HISM

aCR+HeISM

Antiprotons: DETECTED! secondary production

Positrons: DETECTED! secondary production

Anti-nuclei: never detected !They would be the real signature of antistars because their production by “spallation” is negligible

PCR+ ISMNCR+ISM p+ -> m+ -> e+

secondary positrons


Antiproton/proton ratio: before PAMELA


Positron/electron ratio before PAMELA


Antimatter Search


Dark Matter searchesEvidence for the existence of an unseen, “dark”, component in the energy density of the Universe comes from several independent observations at different length scales:

Rotation curves of galaxies

Lensing

Large Scale StructureCMB

Galaxy clusters SN Ia

Bertone, Hooper & Silk, hep-ph/0404175, Bergstrom, hep-ph/0002126, Jungman et al, hep-ph/9506380

C

http://nedwww.ipac.caltech.edu/level5/March02/Plionis/Plionis3_2.html

F:%5CHEAPNET%5CCMB.ppt




The “Concordance Model” of cosmology

tot = 1.0030.010

m ~ 0.22 [b=0.04] ~ 0.74

Most of matter of non-baryonic natureand therefore “dark” !

The “concordance model” of big bang cosmology attempts to explain cosmic microwave background observations, as well as large scale structure observations and supernovae observations of the accelerating expansion of the universe.

Click to edit Master text stylesDifferent data:WD supernovae• CMB• Matter surveysall agreeat one point


•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•Mirror Matter•Champs (charged DM)•D-matter•Cryptons•Self-interacting•Superweakly interacting•Braneworld DM•Heavy neutrino•NEUTRALINO•Messenger States in GMSB•Branons•Chaplygin Gas•Split SUSY•Primordial Black Holes

r

rGMrv

)()(

L. Roszkowski

Dark matter candidates

DM candidates: WIMP’s !SUSY particles ?


Neutralino as the CDM candidate 2

04103

30201

~~~~HaHaWaBa

• Stable (if R-parity is conserved)• Mass: mc~ 10-1000 GeV• Non-relativistic at decoupling

CDM• Neutral & colourless• Weakly interacting (WIMP)• Good relic density

Linear combination of the neutral gauge bosons B and W3 and the neutral higgsinos H1 and H2. The neutralino is a good candidate because:


SIGNALS from RELIC WIMPs

Direct searches: elastic scattering of a WIMP off detector nuclei

Measure of the recoil energy

Indirect detection: in cosmic radiation signals due to annihilation of accumulated cc 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

For a review, see i.e. Bergstrom hep-ph/0002126

n and g keep directionality can be detected only if emitted from high c density regionsCharged particles diffuse in the galactic halo antimatter searched as rare components in cosmic rays

Neutralino annihilation

Production takes place everywhere in the halo!!The presence of neutralino annihilation will destort the positron, antiproton and gamma energy spectrum from purely secondary production


Spectrum deformation

Another possible scenario: KK Dark Matter

LIGHTEST KALUZA-KLEIN PARTICLE (LKP): B ( 1 )

Bosonic Dark Matter:fermionic final states no longer helicity suppressed.e+e- final states directly produced.

As in the neutralino case there are 1-loopprocesses that produces monoenergeticγ γ in the final state.


Kaluza-Klein Dark Matter in e+e-

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)


DIRECT MEASUREMENTS OF

HIGH ENERGY COSMIC RAYS


Main physics research lines

According to the physics line, different platforms and detections techniques have

been adopted.


Stratospheric balloons


The antimatter balloon flights: overviewAim of the activity is the detection of antimatter and dark matter

signals 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 flights started from New Mexico or Canada, with different geomagnetic cut-offs to optimize the investigation of different energy regions. The flights lasted about 20 hours. 4 flights from the HEAT collaboration: 2 HEAT-e+, in 1994 and 1995, and 2 HEAT-pbar flights, in 2000 and 2002


CAPRICE-94

• Charge sign and momentum determination;

• Beta selection• Z selection• hadron –

electron discrimination


Results from MASS/TrampSI/CAPRICE/HEAT: Positrons & antiprotons

Highest energetic points available from balloons

Excess ??


The BESS programThe BESS program had 11 successful flight campaigns since 1993 up to 2008. Aim of the program is to search for antimatter (antip, antiD) and to provide high precision p, He, m spectra.

A modification of the BESS instrument, BESS-Polar, is similar in design to previous BESS instruments, but is completely new with an ultra-thin magnet and configured to minimize the amount of material in the cosmic ray beam, so as to allow the lowest energy measurements of antiprotons.

BESS-Polar has the largest geometry factor of any balloon-borne magnet spectrometer currently flying (0.3 m2-sr).

BESSCollaboration

The Universityof Tokyo

High Energy AcceleratorResearch Organization(KEK)

University of Maryland

Kobe University

Institute of Space andAstronautical Science/JAXA

National Aeronautical andSpace AdministrationGoddard Space Flight Center

University of Denver(Since June 2005)

BESS Collaboration

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 measurementR,b --> m = ZeR 1/b2-1

dE/dx --> Z

BESS Detector

JET/IDCRigidity

TOFb, dE/dx

√

Long duration flights of total 38 days with two circles around the Pole

BESS-Polar I and II


52BESS-Polar II Antiproton

Spectrum Compared with BESS’95+’97: x 14 statistics at < 1

GeV

Flux peak consistent at 2 GeV

Spectral shape different at low energies.

Ref. for BESS’95+’97: S. Orito et al. PRL, Vol. 84, No, 6, 2000

ICRC2011. BESS highlight

BESS-Polar II results - generally consistent

with secondary p-bar - calculations under

solar minimum conditions.

- NO low energy enhnacement due to PBH


Limits on antimatter (antiHe and antiD)

100 t

imes

imp

rove

men

t


CREAM – Overview Aim is the study of CR from 1012 to 5x1014 eV, from proton to Iron, by means of a series of Ultra Long Duration Balloon (ULDB) flights from Antarctica.

6 flights up to now: 2004, 2005, 2007, 2008, 2009, 2010.

The instrument is composed by a sampling tungsten/scintillating fibers calorimeter (20 r.l.), preceded by a graphite target with layers of scintillating fibers for trigger and track reconstruction, a TRD for heavy nuclei, and a timing-based segmented charge device. A fundamental aspect of the instrument is the capability to obtain simultaneous measurements of energy and charge for a sub-sample of nuclei by calorimeter and TRD, thus allowing an inter-calibration in flight of the energy.

http://www.wff.nasa.gov/~uldb/


The CREAM instrument

Collecting power: 300 m2-sr-day for proton and helium, 600 m2-sr-day nuclei


Protons and heliums

Heavier elements: hardening


Advanced Thin Ionization Calorimeter (ATIC)The ATIC balloon flight

program measures the cosmic ray spectra of nuclei: 1 < Z < 26 between 1011 eV and 1014 eV.

ATIC has had three successful long-duration balloon (LDB) flights launched from McMurdo Station, Antarctica in 2000, 2002 and 2007.

ATIC COLLABORATION:Institute for Physical Science and Technology, University of Maryland, College Park, MD, USAMarshall Space Flight Center, Huntsville, AL, USASkobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow, RussiaPurple Mountain Observatory, Chinese Academy of Sciences, ChinaMax Planck Institute for Solar System Research, Katlenburg-Lindau, GermanyDepartment of Physics, Southern University, Baton Rouge, LA, USADepartment of Physics and Astronomy, Louisiana State University, Baton Rouge, LA, USADepartment of Physics, University of Maryland, College Park, MD, USA

http://www.srl.caltech.edu/personnel/dick/cos_encyc.html

http://atic.phys.lsu.edu/aticweb/definitions.htm%23Electron%20Volts


ATIC Instrument Details


Protons and heliums

The ATIC “bump” in the all-electron spectrum


TRACER and TIGER

TRACER balloon flights


TRACER 2 flights data:POWER_LAW fit above 20 GeV/n:

CR energy spectra



B/C ratioGALPROP fit with reacceleration:

GALPROP fit without reacceleration:

Leaky Box:


TIGER and SuperTIGER balloon flightsSuper-TIGER builds on the smaller Trans-Iron Galactic Element

Recorder (TIGER), flown twice on balloons in Antarctica in Dec. 2001 and 2003.TIGER yielded a total of 50 days of data and producing measurements of elemental abundances of the elements 31Ga, 32Ge, and 34Se, and an upper-limit on the abundance of 33As.

Excellent charge resolution in the 10≤Z≤38 charge range.

SUPERTIGER: 30≤Z≤42


It is known by ACE_CRIS data that the abundance of 22Ne points towardsa contribution from outflow of massive starts (Wolf-Rayet stars).TIGER and SuperTIGER search for the enrichments of hevy elements expected from nucleosynthesis in massive stars.


TIGER 1 and 2 combined results


Documents

High energy cosmic rays ROBERTA SPARVOLI ROME “TOR VERGATA” UNIVERSITY AND INFN, ITALY Nijmegen 2012