Fluorescence and Cerenkov Fluorescence and Cerenkov photons from air showerphotons from air shower

1/9-10/20031/9-10/2003VHENTW-3VHENTW-3

Palermo, ItalyPalermo, Italy

Ming-Huey A. Huang 黃明輝Department of Physics,

National Taiwan University

1/9/2003 M.A. Huang

ContentsContents

Air shower longitudinal profileFluorescence photon flux simulationCerenkov photonsArrival time of photonsConclusion

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Why need fluorescence and Why need fluorescence and Cerenkov photons ?Cerenkov photons ? Previous simulation require trigger at distance up

to 5~7 km from shower core.– Cerenkov photons density decrease exponentially

outside Cerenkov ring.– Fluorescence photons distribution is more isotropic

Optical detection can not distinguish fluorescence or Cerenkov photons– Trigger time may different ?– How to use trigger time?

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Longitudinal profileLongitudinal profile Tau exit mountain, deca

y, then initiate air shower– decay length ~ d=50 (E/

PeV) m – Assume tau decay to elec

tron– Gaisser-Hillas formula

XXXX

e XXXXNN

max0max

e0max

0max d=50 km

d=5 km

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Common environmentCommon environment

Pressure, density of atmosphere taken from typical value at altitude 2.5 km, Hualalai mountain top.

Density is assumed as constant, valid for near horizontal events.

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Parameters of Parameters of G-H formulaG-H formula

Nmax = E/(1.35 109) Xmax = 550 + 80log(E/1

015) X0 is insensitive and have

large fluctuation, use 5 gm/cm2

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SimulationSimulation

Detection by fluorescence light offers larger solid angle than by Cerenkov lights.

For trial runs: simulate neutrinos from a typical configuration.

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SimulationSimulation

Nph=NegfMirror size 1m2

Angular size for each pixel 0.5ºSimplify geometry to 1-D track on shower-

detector plane. 1-D detector, cover from -80º to +80º

– Just to cover whole track, not the finial design

Emission angle

=90º

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Fluorescence yieldFluorescence yield Y: fluorescence yield Ne: # of secondary particl

es : fluorescence eff. = #/c

m/e q: mean ionization energy 2.2 MeV/

(g/cm2) : density P: pressure T: temperature

i

eff

iii

e

TT

PPERTP

TPqNTPY

0)(10124.0

,

),(,,

Ri : Reflectance/transmittance at wavelength I

Ei : intensity Peff : effective pressure T0: Temperature at STP

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Fluorescence efficiencyFluorescence efficiency

Top : From P. Sokolsky book and many references

Bottom: Data from Bunner’s thesis, used in this simulation.

Quite similar, but small differences

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Geometry factorGeometry factor

Rp: distance covered in each pixel

: emission angle, between line of sight and shower axis

r: distance from detector to shower track in FOV

A: mirror/lens area: scattering length ~ 20km

/

22 4sincos1 re

rAdgf

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Photon number per pixelPhoton number per pixel Threshold = 3 photon per

pixel Even electronics

sensitive to single photo-electron, threshold energy is still high ~ 1016.5 eV

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Difficulty in telescope orientationDifficulty in telescope orientation

Different distribution of shower maximum, a small coverage in azimuth angle could only see a fraction of total energy range.

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Difference between results from Difference between results from Giancarlo’s and Alfred’sGiancarlo’s and Alfred’s

Fluorescence efficiency:– G: 4.5 photons/m/e & A: 2.3 photons/m/e

Shower profile:– G: GIL formula– A: Nmax=E/1.35 (E in GeV)– At above 1019 eV, difference ~2%– At 1015 eV, G is 38% higher

Mirror size– G: 2 meter radius, A: 1m2

)81.0/ln(81.031.0max E

EN

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Comparison:Comparison:Giancarlo’s results is higher by

– Mirror : 12 times larger– Efficiency: 2 times larger– Shower size: 38% larger at 1015 eV

Adapting Giancarlo’s number, the minimum threshold is around 1015 eV– Geometric factor seems OK !

Questions remains!

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Nighttime airglowNighttime airglow

Much complex than previous measurements

Contamination?

Johnston and Broadfoot, 1993, JGR, 98, 21593

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Question: fluorescence efficiencyQuestion: fluorescence efficiency

Wavelength seems O.K. Absolute intensity is different in

Bunner (Alfred’s and Chen’s) and Kakimoton’s

P. Chen’ talk in Workshop of Laboratory Astrophysics, Taipei, 2002.

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Cerenkov light simulationCerenkov light simulation Study photon density and arrival time Use ground array to sample Cerenkov

photons

Cerenkov photons are integrated over whole shower track– Longitudinal profile similar to

fluorescence mode.– Shower start at different altitude, 20,

30, and 40 km.– Shower energy 1014, 1016, 1018 eV

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Simulation of photon arrive timeSimulation of photon arrive time T=0 at injection point, where e Calculate shower longitudinal profile,

produce Cerenkov photons c/n electrons have angular spread

according to multiple scattering Cerenkov photons emit from

electrons directions Calculate photons propagation time

and hit positions at ground.

C

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Fluorescence photon arrival timeFluorescence photon arrival time

Cerenkov photon time + decay time of fluorescence photons (10ns ~ 50ns, depends on wavelength)

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Cerenkov longitudinal profileCerenkov longitudinal profile

Nph=Neexp(-r/ ) is Cerenkov efficiency

• Depend on mean energy and index of refraction

• ~ 203 photons/(g/cm2)/e length in FOV : scattering length ~ 20km

1018 eV

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Arrival time Arrival time

Similar to simulation by Corsika

500ns

500ns

CORSIKA

Fast simulation

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Mean arrival timeMean arrival time

Depends mainly on shower position

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Cerenkov photons Cerenkov photons Arrival timeArrival time

T=0 when first photon hit detector

Time gate for coincidence between two detectors

– in the order of sec.– depends on distance between

detectors and Rp – important tools to reconstruct

event arrival direction and Rp

Photon wave front

Rp

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RMS of arrival time RMS of arrival time

Depend mainly on shower position

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RMS of arrival timeRMS of arrival time Photons from different

part of showers arrive same detector at different time.

cc/n

If electronics can measure the spread of arrival time,

pulse width, it can be correlated to Rp!

Time gate for individual detector– Depend on Rp– Could be as large as 20

0 ns (Rp<5km).

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Conclusion on arrival timeConclusion on arrival time

Arrival time is critical for :– requirement for electronics design– event reconstruction

• Still need more works in reconstruction programsFor two detectors separated by 1km

– Gate time for one detector: RMS of arrival time ~ 200ns at Rp = 3km

– Coincidence time between detectors: ~ 1 s

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Fluorescence + CerenkovFluorescence + Cerenkov

For events near shower core, small Rp, detected photons are combination of Cerenkov photons and fluorescence photons– Need to combined two simulation– Need to separate two photons in reconstruction.

For events with large Rp and large energy, fluorescence photons is as important as Cerenkov photons.

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ConclusionConclusion

Photons are photons, no need to exclude fluorescence or Cerenkov photons.– Near PeV, Cerenkov photons flux is higher– Near EeV, both signals are strong, fluorescence mode h

ave larger acceptance. Dream detector:

– Detect both Cerenkov and fluorescence photons• Best way to take advantage of all signals.• Difficult to design electronics and trigger.

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On-going and future projectsOn-going and future projects

Simulation:– Fluorescence + Cerenkov photons– Reconstruction– Parameters form stereo observation by two

detectorsTheoretical side:

e & via W resonance – Energy resolution

Detector Design ConceptDetector Design Concept

1/10/2003Ming-Huey A. Huang 黃明輝

Department of Physics, National Taiwan University

1/9/2003 M.A. Huang

ContentsContents

Sensitivity and Event rateRequirements on detector designMulti-mirrors approachSite issues

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Expected performanceExpected performance

Target volume: better than the design goal of IceCube ~ 1 km3 at E > 1015 eV

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New flux New flux sensitivitysensitivity

0.3event/year/half decade of energy– Similar to single e

vent sensitivity (SES)

Great chance to see AGN and TD

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Sensitivity and Event RateSensitivity and Event RateEvent Rate

0.01.02.03.04.05.06.07.0

1.00E+13

1.00E+14

1.00E+15

1.00E+16

1.00E+17

1.00E+18

1.00E+19

Neutrino Energy

Even

r Rate

(#/yr

)

Sensitivity : 1 event/yr/half decade of energy A=R R2=(2 /1 )R1

Total Rate in 1014 ~ 1018 = 12.2 events/yr (include 10% duty time) Assuming detection efficiency 0.3-0.7, R~ 4-8 events/year

Sensitivity and Sigl flux

1.00E-021.00E-011.00E+001.00E+011.00E+021.00E+031.00E+04

1.00E+13

1.00E+14

1.00E+15

1.00E+16

1.00E+17

1.00E+18

1.00E+19

Neutrino Energy

flux*

E2̂

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Requirements on detector Requirements on detector

Field of view 12º135º30 photons in 1 m2 mirror/lenspixel size ~ 0.5ºTrigger condition

– 2 pixels triggered with 2 photo-electrons• combined efficiency

(reflectance/transmission/quantum efficiency) ~ 4/30 ~ 0.13

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Lateral profile of Cerenkov photonsLateral profile of Cerenkov photons

• Similar profile for showers produced by e– and • Cerenkov ring distance ~ (L-Rmax)Tan c

• Outside ring, photon density ~ exponential decay• Detector can trigger far away from Cerenkov ring

1018 eV

1016 eV

1014 eV

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Optical systemOptical system

Technical difficulty:– Odd shape field of view 12º135º, difficult to

covered by a single mirror or lens– F value!

Constraints:– Palermo: 290 8x8 MAPMT– Budget– Construction time/complexity

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Solution: multiple telescopesSolution: multiple telescopes

Connecting several small telescopes to cover full FOV

Each unit can be modified from existing models and available technologies.

Options: – 4 Fresnel lens telescopes,

each cover 12º36º • Similar to Shimizu’s EUSO

prototype

– 11 Reflective telescopes, each cover 12º12º

• Similar to HiRes (16º16º)

Divide and Conquer

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Advantages and DisadvantagesAdvantages and Disadvantages

The good All technologies available! Modularized design

– easy construction schedule– operation start from first

module, early start! Chance to learn from first

module, easy to modify.

The bad Complexities in

calibration and installation– Can not be avoid and can

be done!

The Ugly Environmental impact

– larger building

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Example: 11 modules Example: 11 modules

Top view

Side view

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F problemF problem

Large FOV and small pixel size F < 1– Very difficult in optical design– loss effective collection area at large

off axis angle. Can be manipulated by light guide

– Also kill the dead-space problem– Light guide can match curved focal

surface. MAPMT array

Light guide

Lens/Mirror

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Site requirementsSite requirements

Detector housing– Two 48 feet container for 11 reflective mirrors

• one for telescopes and one for electronics and others– One 48 feet container for 3-4 Fresnel lens

Power – Solar and wind

Communication

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Some issues related to siteSome issues related to site

Is Hawaii the only site available?– Worry about inversion layer of Hualalai site– Site survey of White mountain, CA?

Need long term weather information– Pressure, temperature, wind speed, humidity, ...– Cloud height, visibility (aerosol contents …)

On-site background measurement