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Coherent radio pulses from high energy showers: A blooming field In the memory of a brilliantly original mind Enrique Zas Instituto Galego de Fisica de Altas Enerxias & Universidad de Santiago de Compostela 1 Coherent radio pulses

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Coherent radio pulses from high energy showers: A blooming field

EZ Heidelberg 2018 Coherent radio pulses from high energy showers

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Enrique Zas

Instituto Galego de Fisica de Altas Enerxias & Universidad de Santiago de Compostela

In the memory of a brilliantly original mind

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Particles radiate (or induce radiation Cerenkov)

  • Radiation adds coherently for low enough frequencies
  • Power of coherent radiation scales with (shower particles)2
  • Showers have lots of particles => Interesting for UHE!

Interference effects give rich diffraction patterns

  • Shower could be fully visualized if sufficiently well sampled !!

(amplitude & phases in every direction)

Signal: contributions from many (all) shower stages

  • Reduced fluctuations => good observable

Antennas: cheap Radio detection: high duty cycle Main difficulty: dealing with noise

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58 J. Jelley 58 extend Cherenkov to radio 61 G. Askary’an excess Q=∆q 65 In air: high ν 65 J. Jelley 8 “mechanisms” (ICRC65)

  • Enhanced Cherenkov(Askary’an)
  • Dipole Cherenkov
  • Synchrotron radiation
  • Transition radiation
  • Coulomb field bremsstrahlung
  • Induction (by nearby charges)
  • Molecular transitions
  • Reflections of continuous waves (Doppler shifted)

67-70 Air: e+e- separation in BGeo dominant (Th & exp) 75 decline of field, steep ldf, storm interference … 90 ν detection: full calculations in ice (ZHS)

New initiatives radio telescopes, air showers, ice, salt …

00 Lab measurements Air showers 1st generation LOPES, CODALEMA, ANITA (GHz) 10 Full simulations (ZHS algorithm + MC) 2nd generation LOFAR, AERA, Tunka-Rex (E,Xmax) 20 Ambitious plans: GRAND, AugerRadio, phased arrays …

Complex some are limiting cases

  • f given situations

but it is all in Maxwell’s laws!

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Calculations are key: Based on simple solution

Maxwell’s Equations in transverse gauge The transverse current is the divergenceless component (the transverse projection at large distances) Well known solution, Vector potential A gives us the radiated field

Delta of Retarded time with

nc = με

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Solve for simple case (constant speed)

t1 t2 v v=0

position

δt=t2-t1

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Organize t and t’ and massage

vδt

θ Fraunhofer approximation

i.e.

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Substitute into solution for A

Divergence at Cherenkov angle? NO!! We formally get derivative of Theta funciton Limit Note A proportional to TRACKLENGTH CHERENKOV Radiation

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Vector potential E-field

Time

Field single track: Time domain

“Decceleration” “Acceleration”

[J. Alvarez Muniz, A. Romero-Wolf, E.Z., PRD 81, 123009 (2010)]

NOTE: “Acceleration” with a grain of salt Limit of large δt gives Cerenkov radiation (by medium) Terms of adjacent sub-tracks give large cancellations

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) ( 1 1 ) (

) ( ) (

v k i e v e R i E

t v k i phase

  • verall

i

  

 

⋅ − − =

⋅ − ⊥ −

ω ω ω

δ ω

[ ]

t n t n t v ω θ β ω θ β δ ) cos 1 ( ) cos 1 ( sin − −

⊥

trackl klength

if ω=0

  • r θ=θc
  • r δt=0

t v δ

⊥

(Fraunhofer limit)

Fourier transform => ZHS

State -o f-the -art: simulatio ns AI RE S / CORSI K A + Zas-Halze n-Stane v alg o rithm (c lassic al e le c tro mag ne tism)

[E.Z., F. Halzen, T. Stanev PRD45 (1992) 386]

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Askary’an effect: excess charge

G.A. Askaryan

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  • J. A-M, A. RW, E

. Z, PRD 81, 123009 (2010)

J(z,t) = v Q(z) δ(z - vt) A(to bs, θ) ≈ v Q(ζ) / R

Vector potential

E(to bs, θ) = d A(to bs, θ)/ d to bs

Electric field ζ → Retardation + time-compression:

F ro m z to time to bs (θ –d e pe nd e nt)

to b s = z(1 - nc o sθ)/ c + t0 to b s = t0 @ θc

Unidimensional current

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Interesting for neutrino detection e showers & hadronic debris separate (LPM) Flavor tagging : νe Measure y (energy transfer to hadrons)

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νe + N → e + jet

E(νe) = 10 EeV E(hadron jet) = 2 EeV E(electron) = 8 EeV

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Pulseahead of time!

Path difference

θ > θc

Emission out of phase L path difference =λ => diffraction minimum like in a single slit L ~ slit width

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The slit diffraction analogy

If current is “thin”:

∫

∝

ikz

e z dzQ R i E ) ( ) ( ω ω 

c n k ω θ) cos 1 ( − =

FT with

θc

Great scaling properties: reduced fluctuations

integrated emission (“calorimetric”)

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Esh (TeV)

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Esh (TeV)

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Esh (TeV)

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Path difference = d sinθc

θc

Blow up of shower front In Cherenkov direction: d sinθ= λ Interference minimum at lower λ(higher frequency)

d

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Why is the atmosphere so different?

Opposite charges cancel!!

The Cherenkov angle is small ~ 10

J┴ = Q v┴ ~ 0.2Nec sin θ ~ 0.003 Nec (Askary’an) B → transverse current ~ v┴drift ~ qB┴/ρ ~ 0.04c J┴ = Q v┴drift ~ 0.04 Nec (geomagnetic) often dominant

Depends on sin(α) [angle between shower axis and B field]

  • O. Scholten et al. ApP29(2008)94
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Jgeo

B

Sho we raxis

v

Ge o mag ne tic Askaryan

Polarization of two components is different

However new complex issues: Loss of symmetry (mixed patterns) There is a varying refractive index There is curvature of the atmosphere …

F ro m e xc e ss c harg e

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Lessons from experiments

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Many activities pursued

>89 On Moon from Earth: GLUE, ATCA, LUNASKA, LOFAR … >96 In Ice: Rice, ARA, ARIANNA … >00 On “lab”: SLAC (Silica Sand, Salt, Ice, Air+B), Utah (ARAcalTA) … >03 In air: LOPES, CODALEMA, AERA, LOFAR, Tunka-Rex… >03 In ice from air: ANITA … >10 in air microwave: MIDAS, CROME, EASIER, MAYBE ...

R.D. Dagkesamanskii, I.M. Zheleznykh, Sov. Phys. JETP Lett. 50(1989)259 …

  • P. Gorham, D. Saltzberg et al. PRL86(2001)2802 …
  • P. Gorham, et al. PRL96(20006)171101

D.Ardouin; H. Falcke …

  • G. Frichter; D.Besson; D. Seckel; …
  • P. Privitera; A. Lettessier-Selvon; R. Smida; V. Verzi, …
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Xmax reliably measured!

Buitnik, S. et al. Nature 531 (2016) 70

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Energy in radio is an excellent energy estimator!

The Pierre AugerCollaboration, PRL 116, 241101 (2016); PRD 93 122005 (2016)

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36 km high

ν

14 events CR detected! Why GHz radiation?

  • P. Gorham, et al. PRL105(2010)151101
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Path difference = d sinθc

θc

Blow up of shower front At θc coherence up to the GHz in spite of scale factor!!

d

Diameter 1000 times larger BUT θc VERY small

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Insight from time delays

Antarctica proton 1019 eV

Observer at position such that shower center (0,0) is viewed viewed at Cherenkov angle

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Alvarez-Muñiz, et al. PRD 86 (2012) 12300

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Blow up of central region

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Different spectra as we get away from Cher angle

Inner cone ψ=0.70 ψ=0.620 ψ=0.550 ψ=0.480 ψ=0.40 ψ=0.330 ψ=0.250 ψ=0.180 ψ=0.110

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Inner cone ψ=0.70 ψ=0.620 ψ=0.550 ψ=0.480 ψ=0.40 ψ=0.330 ψ=0.250 ψ=0.180 ψ=0.110

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Inner cone ψ=0.70 ψ=0.620 ψ=0.550 ψ=0.480 ψ=0.40 ψ=0.330 ψ=0.250 ψ=0.180 ψ=0.110

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Excellent scaling with energy

Inner cone ψ=0.70 ψ=0.620 ψ=0.550 ψ=0.480 ψ=0.40 ψ=0.330 ψ=0.250 ψ=0.180 ψ=0.110

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  • H. Schoorlemmeret al. Astropart.Phys. 77 (2016) 32-43
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Gorham et al. PRL117(16)071101 Gorham et al. PRL121(18)161102

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A Romero-Wolf et al. ArXiv:1811.07261

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The future is Big and Bright

URGENT need to explore the PeV to EeV neutrino region

In Ice experiments -> Phased Array, NGR

(Next Generation Radio Array)

In Air from Ice experiments -> EVA, GRAND In Air: Auger, SKA, GRAND (neurinos & CR)

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A.G. Vieregg, K. Bechtol, A. Romero-Wolf; JCAP 1602 (2016) no.02, 005

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G ra nd35 (2.4 km 2) 2018 G ra nd300 (135 km 2) 2020 1016.5- 1018eV G ra nd10K (104 km 2) 2025 G ra nd200K (2 105 km 2) 2035?

  • J. Alvarez-Muñiz et al ArXiv:1810.09994
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J.HörandelUHECR, Paris 2018

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Thank You

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There has been much progress in radio Manyinitiatives are being pursued explored Ambitiousplanstargetingphysicsare quite advanced Surely new ones are bound to crop up The future is wide open

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What have we been looking for?

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Energy in radio correlated with shower energy

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(SquareKilometerArray)

MID Frequency ApertureArray LOW Frequency ApertureArray

  • world’s largest radio telescope
  • 1 km2 of total collecting area
  • thousands of antennas
  • to be built in Australia &

South Africa

  • broad scientific goals:

astronomical& cosmological obs.

  • “phased array": can observe

multiple regions of sky simultaneously!!

  • Moon proposed to be observed at

differentfrequency bands:

  • SKA-LOW (100 – 750 MHz)
  • SKA-MID (350 – 1760 MHz)
  • can also detect UHECRs
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Why is the atmosphere so different?

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Path difference = w cos θc

θc

Further blow up of front

w

Interference from late and early particles within shower front Often 2ndorder

Shower front thickness and curvature play the limiting role

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proton shower of energy 1019 eV in Antarctica at Cherenkov angle

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Is the picture Complete?

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Reflection

  • Earth’s curvature
  • Roughness

Refractive Index

  • Ray’s curvature
  • Variability
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Events can be reconstructed from single location!!

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The future is wide open

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toroidal reflector feed array @ focus

  • Concept: Turn an entire super pressure

balloon into the antenna !!

Similar sensitivity to full, 3 y

  • f ground-based arrays

G o rha m e t a l. APP 35, 242 (2011)

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Coherent radio detection: ν- experiments

Natural transparent media

 ICE:

 Antarctica

 RICE (array buried)  ANITA (balloon)

 Greenland

 FORTE (satellite)  SALT:  Domes explored  SALSA  MOON REGOLITH:

 Radiotelescopes

 GLUE

 Radiotelecope array

 LUNASKA (ska)  ATMOSPHERE:

 Antenna array

 LOFAR

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Askary’an effect confirmed: SLAC

P.Gorham, D.Saltzberg et al. PRL (2000)

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Coherence! |E| α Esh |E(ω)| spectral agreement

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  • Radio Technique has an enormous potential

 To detect highest energy events  To get detail about showers  To cover large surfaces

  • It is my opinion (and others) that radio could

provide the next step in the search for UHE radiation

  • There are many projects under consideration
  • It is worth investing on them (lot work to do)

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Summary and conclusion: