Fundamental Physics with Cosmic RaysOUTLINE Cosmic rays in particle physics history SUSY dark matter Ultrahigh energy cosmic rays Supernova neutrinos A few selections from the smorgasbord:physics.bu.edu/neppsr/...CosmicRays_Kate_Scholberg.pdf ·

Kate ScholbergMITNEPPSR 2003

Fundamental Physics with Cosmic Rays

OUTLINE

Cosmic rays in particle physics history

SUSY dark matter

Ultrahigh energy cosmic rays

Supernova neutrinos

A few selections from the smorgasbord:

Introduction to cosmic rays

Relic big bang neutrinos

Questions of Fundamental PhysicsWhat are the elementary particles and their interactions?

Is nature supersymmetric?

What are the neutrino masses and mixings?

Why is there a matter-antimatter asymmetry?

What is the Universe made of, and how did it all come about?

What is the dark matter?

"Cosmic Ray" ≡ "a particle from space"� naturally occurring� various sources (Sun, supernovae, AGN, GRB)

� many species, charged and neutral

� wide energy range

(Are photons CR? Depends...)p, n, A, e±, γ, µ±, ν, ...

Cosmic Ray Primer

PRIMARY CR: directly from outer space (stable, charged component mostly protons)

More terminology:

SECONDARY CR: created in collisions with atmosphere

(c) 1999 K. Bernlohr

(includes muons,short-livedcomponent)

Charged cosmic ray fluxes for different species

Dominatedby protonsup to~ TeV

(compositionless wellknown at higherenergies)

Charged cosmic rays:affected by Earth's dipole magnetic field

Many interesting trapping and bouncing effects...

Low energy primary CR cannot enter geomagnetic field

Cutoff rigidity ~1-10 GeV per nucleon, depending on latitude

Rigidity≡ p/(Ze)

solar windeffects at <~ 1 GeV

Another comment: charged cosmic rays don't point back to where they came from!

Gyromagnetic radius:

R= 3.3 x 1012 p/(ZB) R in cm, E in GeV, B in µG

For Galactic field of 3 µG, R=1012 cm(<0.1 A.U.) for 1 GeV/c proton

R~ diameter of Galaxy at ~ 1019 eV/c

Charged CR follow tangled path, nearly isotropic

Neutral CR (γ,ν) point back to source

Charged Primary Cosmic Ray Energy Spectrum

Sun Supernovae Other sources ???

geo magnetic cutoff

higher energies preferentially escape Galaxy

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SUSYdark matter


Supernova neutrinos




Cosmic rays have figured prominently in the history of particle physics...

Victor Hess, 1912: gold leaf electroscope to 5000 m altitude

First identification of "cosmic radiation"

Years of high drama ensue...

Anderson's discovery of the positron, 1932

Wilsoncloud chamberphoto

The antimatterpredictedby Dirac!

Neddermeyer and Anderson, 1937: discovery of the muon in cloud chamber

"Mesotron": mass intermediate between electron and proton

Late 1940's: Powell and others

Mountaintop observatories and photographic emulsion: discovery of the pion

π→ µ + ν µ → e + ν + ν

Discovery of strangeness: "V particles"

Rochester andButler, 1946

First kaon

The "particle zoo" followed...

Over the next ~40 years,accelerators dominated newdiscoveries in particle physics...

...but, now since the 1990's, cosmic rays have again come tothe forefront as a tool for fundamentalphysics, complementing accelerators!

Cosmic ray physicists mostly focused on understanding sources, composition, propagation, ...

Cosmic rays answer whereaccelerators can't reach...

SUSY dark matter: annihilation signals, direct detection

Ultrahigh energy cosmic rays:exotic matter,Z-bursts,cosmic ν's

Matter-antimatter asymmetry: antimatter searches


Neutrino mass & oscillations:Atmospheric, solar, and supernova ν's

Strange matter, QCD Gravitational waves

Primordial black holes Neutrino astrophysics

OUTLINE


SUSY dark matter


Supernova neutrinos



Relicbig bang neutrinos

Cosmic Ray Spectrum

1 per sq km per century above 1020 eV

extragalacticcomponent

M G T Peta Exa Zetta

Greisen-Zatsepin-Kuzmin (GZK) cutoffCosmic rays with energies greater than 5 x 1019 eV will be absorbed by the Cosmic Microwave Background

p + γ → N + π

Mean free path 50 Mpc at 1020 eV

Galaxy: 20 kpcAndromeda: 0.7 Mpc

But some CR observed above the GZK cutoff...

What are they??

"Bottom up" mechanisms: particles accelerated to high energies

Any observed anisotropy should lead to sources

How? SN can only accelerate up to 1015 eV

Origin in AGN, GRB, magnetars?

Need very large fields,confinedspaces

→ not clear how it works...

"Top-down": source is something exotic, involving new fundamental physics?

e.g. Superheavy (1013-1013 GeV) particles decay to UHE Standard Model particles...

BB relic long-lived dark matter?

No cutoff because Galactic origin

Expect excess toward Galactic center

� Topological defects? � Other exotic primaries?

� Violation of Lorentz invariance?� Strong neutrino interactions?� "Z-bursts"?

uhecrons (light SUSY hadrons), glueballinos,...

Again, we need to look at anisotropy, correlations with objects, spectrum, composition to distinguish the models

Other ideas:

Detection Techniquesobserve gigantic air showers

Requires huge area!

Air Fluorescence: glow of excited N molecules

Air shower array: observe particles on ground

Fly's Eye, Hi-Res, TA

AGASA

1 per sq km per century above 1020 eV

Recent results

Exp'tsdon't agree?

Hi-Res: fluorescenceAGASA: air shower

Is GZKcutoffthere ornot?

The Pierre Auger Experiment

air fluorescence and air shower array

Argentina

3000 km2, expect 50-100 UHE events per year

EUSO for ISS

OWL/Airwatch stereo view satellites

air fluorescence from above to view huge area!

And the farther future: site a detector in space

Summary of UHECR

Nucleons are absorbed by the CMB above ~1020 eV within 50 Mpc...

Observed post-GZK events have a mysterious origin

"Bottom-up": exotic astrophysics"Top-down": exotic physics

Need to characterize anisotropy, spectrum

Gigantic area detectors required...AGASA, Hi-Res→ Auger → EUSO, OWL

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SUSY dark matter


Supernova neutrinos




The DARK MATTER Mystery

Baryonic matter (ordinary stuff) only ~5%!

Non-baryonicdark matter

~25% !!

Many independent measurements� Galactic rotation curves� Gravitational lensing, microlensing� Cosmic microwave background� Large scale structure� Nucleosynthesis� High z redshift surveys

"DARK ENERGY"

One appealing hypothesis toexplain non-baryonic dark matter:

Weakly Interacting Massive Particles (WIMPs) that froze out after the Big Bang

NEUTRALINO χ lightest stable supersymmetric particle

50 GeV/c2< mχ < 3 TeV/c2

accelerator bound (LEP)

cosmological bound

e.g.

Neutralinos couldmake up the Galactic halo

χ

χ

χ

χ

χχ

χ

χχ

χ χ

χ

Local halo density ~ 0.3 GeV cm-3

(but could be clumpy)

Signature of neutralino dark matter:Look for ANNIHILATION PRODUCTS

χχ gauge bosonsquarksleptons

e+

pdγ...

Here, have background of SECONDARIES from CR collisions

⇒ look for ANOMALIESin the energy distribution

"bump in the spectrum"

Look for anomalous POSITRONS

χχ annihilationwould givebump around ~10-100 GeVbackground

from secondaries should be smooth

A hint from a balloon experiment, HEAT? hep-ph/9902162

Bump at ~10 GeV seen with different instruments

Positron fraction vs energy

N

Interpretation in terms of SUSY DMBaltz et al. astro-ph/0109318

Fits require "boost factor" to enhance signal (plausible for clumpy DM)

SUSY parameter space dots represent allowed models

Look for anomalous ANTIPROTONS

In this case, low energiesmay have less background

backgroundfrom secondaries

But:geomagnetic cutoff, solar wind effects

AAlso: antideuterons

Can also look for χχ annihilation via γ-ray products

χχ gauge bosonsquarksleptons

γ's inshowers

hadronize

Continuum emission at ~1/10 mχ

Or, spectral line from direct χχ -> γ's

The Alpha Magnetic Spectrometer for ISS

Sensitivity to charged cosmicrays up to 1 TeV, and γ's 10-100 GeV

Summary of Dark Matter SearchNon-baryonic dark matter (e.g. χ) indirect signature: χχ annihilation products

in >~ 10 GeV range

in ~< 1 GeV range

in 10-100 GeV range from Galactic center, halo

Positrons

Antiprotons

Gamma rays

from Earth center, sun, Galactic center (trapped WIMPs)

Neutrinos

OUTLINE


SUSY dark matter


Supernova neutrinos




Core Collapse Supernovae: Copious producers of ν's

Expect ~3 ±1 /century in our Galaxy

The Supernova Neutrino Signal

< 1% in em radiation, k.e., 99% in ν's of all flavors

~1% νe from 'breakout', 99% νν from cooling

Energies: <Eνe > ~ 12 MeV

<Eνe > ~ 15 MeV

<Eνµ,τ

> ~ 18 MeV( )

Deeperν-sphere => hotter ν's

Timescale: prompt after core collapse ∆t~10's of seconds (possible sharp cutoff if BH forms)

�Eb~GMcore

2

Rnstar

~2 × 1053 ergs

Neutrino Luminosity: Generic Features

1 s

50 s

Burrows et al. 1992

very short (ms) νe spike at

shock breakout

cooling →

sum ofν

µ,τ and

anti-ν's

roughlyequalluminosityper flavor

luminositydecreaseover 10'sof seconds

SN1987A

Confirmed baseline model... but still many questions

Type II in LMC (~55 kpc)

Water Cherenkov: IMB Eth~ 29 MeV, 6 kton 8 events

Kam II Eth~ 8.5 MeV, 2.4 kton 11 events

Liquid Scintillator: Baksan Eth~ 10 MeV, 130 ton 3-5 events

Mont Blanc Eth~ 7 MeV, 90 ton 5 events??

What Can We Learn from a Galactic Supernova Neutrino Signal?

NEUTRINO PHYSICS� ν absolute mass from time of flight delay� ν oscillations from spectra (flavor conversion in supernova core, in Earth)

CORE COLLAPSE PHYSICS� explosion mechanism� proto nstar cooling, quark matter� black hole formation

from flavor, energy, time structure of burst

ASTRONOMY FROM EARLY ALERT~hours of warning before visible SN, + some pointing with ν's� progenitor and environment info� unknown early effects?

sin2 2θ

∆m2

10−11

10−10

10−9

10−8

10−7

10−6

10−5

10−4

10−3

10−2

10−1

1

10

10−4

10−3

10−2

10−1

1 �e � �x

��

�

�� e

LSND signal still there: wait for BooNE

Atmospheric signal confirmed by K2K beam suppression + spectrum Solar ν oscillation

confirmed by SNO NC; only LMA now allowed; and now KamLAND confirms with reactor ν's!

Neutrinos: What Do We Now Know?2-flavor oscillation signals

"Standard" 3-flavor picture: Parameters: 2 ∆m2, 3 angles, δ

CP, (2 δ

M)

or

U=1 0 00 C23 S23

0 �S23 C23

C13 0 S13 ei �

0 1 0�S13 ei � 0 C13

C12 S12 0�S12 C12 0

0 0 1

MNSmixingmatrix

∆m12

2

∆m23

2

µτ

ee µ

τ

τ{

{ ∆m12

2

∆m23

2 τ

{

{µ

µ

"Normal" hierarchy "Inverted" hierarchy

Absolute mass scale?

µτ

ee

τ

(solar)

(atm.)

µ

Kinematic limits: mν< 2.2 eV

0νββ limits: <mν> < 0.35 eV

Cosmology (WMAP): mν < 0.23 eV

{

Remaining Questions (that supernova neutrinos might shed light on)

What is the mass hierarchy?

What is Ue3

? Is it non-zero?

or∆m

122

∆m23

2

µτ

ee µ

τ

τ{

{ ∆m12

2

∆m23

2 τ

{

{µ

µ

"Normal" hierarchy "Inverted" hierarchy

µτ

ee

τ

(solar)

(atm.)

µ

What is the absolute mass scale?

Neutrino Absolute Mass:

� energy-dependent time spread � flavor-dependent delay

∆t(E) = 0.515(mν/E)2D

t=0 from black hole collapse? grav wave signal?

Look for:

Expect time of flight delay

SN1987A: mν< 20 eV for ν

e

...no longer relevant?

Example: νe signal for black hole cutoff

Beacom et al. hep-ph/9806311

Current detectors: ~few eV level limits possible, at best

energy-dependent delay for ν

e

Neutrino Oscillations, Mass Hierarchy

⇒ compare NC, νe, ν

e rates and spectra

Perhaps more promising:

Energies: <Eνe > ~ 12 MeV

<Eνe > ~ 15 MeV

<Eνµ,τ

> ~ 18 MeV( )

Flavor-energy hierarchy is robust

Flavor transformations in stellar matter ⇒ spectral distortion e.g. expect hot ν

e or ν

e

Also: matter effects in Earth can modify signal

Some signatures

� νe in neutronization peak

completely transformed� hard ν

e during cooling

� Earth matter effects for νe

Some SN model-dependence...

Sensitivity to |Ue3

|2 as low as 10-4 to 10-5

� νe in neutronization peak

partly transformed� hard ν

e during cooling

� Earth matter effects for νe

}}

Normalhierarchy

Invertedhierarchy

(assuming LMA, |Ue3

|2 relatively

large, 3-flavor picture)

Supernova Neutrino DetectorsNeed ~ 1kton for ~100 interactions

Must have bg rate << rate in burst

Also want: � Timing� Energy resolution� Pointing� Flavor sensitivity (neutral current)

Detector Types

� Scintillator CnH

2n

�

Water Cherenkov H

2O

� Heavy Water D2O

� Long string water Cherenkov H2O

� 'High Z' Pb, Fe

Example: Super-Kamiokande Mozumi, Japan

50 kton of water(32 kton inner + outer detector)Now resumed operation after 2001 accident

νe + p e+ + n

νe + 16,18O 16,18F + e-

νx + 16O ν

x +

16O*

νx + e- → ν

x + e-

νe + 16O 16N + e+

7000

53005060

200

Pointing: ~4o at 8.5 kpc

Events expected for collapse at 8.5 kpc, > 5 MeV:

(5-10 from breakout)

Summary of Types of SN Neutrino Detectors

� Primary sensitivity is to νe, NC for heavy water, high Z

� Pointing for water Cherenkov, heavy water, argon� All real-time except radiochemical� All have energy resolution except long string, radiochemical

Distance for 90% CL detection, 1/month threshold

Far side of GalaxyLMC

Andromeda

Detector Mass (kton)

Dis

tan

ce s

ensi

tivi

ty (

kpc)

λ=0.01 Hz/kton

λ=0.001 Hz/kton

λ=0.0001 Hz/kton

0

200

400

600

800

1000

1200

0 100 200 300 400 500 600

Distancesensitivitydepends on:

� Mass� Background rate λ

Eth~ 5 MeV

∆T = 10 s

Summary of Future SN Neutrino Detectors

Galactic sensitivity

ExtraGalactic

Summary of Supernova Neutrinos

A Galactic core collapse will yielda vast quantity ofinformation...

� Neutrino absolute mass: few eV sensitivity from time of flight delay (not better than lab?) � Oscillation info: mass hierarchy, θ

13

from spectral distortion, Earth matter effect

Many detectors with Galactic sensitivity online now... next generation extra-Galactic?

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SUSY dark matter


Supernova neutrinos




Relic neutrinos which froze out after the Big Bang, t ~ 1 sec

Expect T=1.95 K, sub-eV ! Nonrelativistic? Number density 113/cm3 per family

Very very very hard to detect...

A experimental Holy Grail...

One idea: Z-bursts

Ultra-high energy neutrinos interact with relic BB ν background at Z-pole ⇒ produce UHE CR

Eres

= MZ

2/2mν= 4.2 x 1021 eV (m

ν/1 eV)

SummaryCosmic rays have a venerable history, and are in vogue again!

The next progress in fundamental physics may come from a non-standard approach...

Sumptuous dining ahead!

Documents

Fundamental Physics with Cosmic RaysOUTLINE Cosmic rays in particle physics history SUSY dark matter Ultrahigh energy cosmic rays Supernova neutrinos A few selections from the smorgasbord:physics.bu.edu/neppsr/...CosmicRays_Kate_Scholberg.pdf ·