LBL, April 10, 2012 1

Results from the Telescope Array

Experiment

Gordon Thomson

University of Utah

2

Outline

• Introduction

• TA Results:– Spectrum– Composition– Search for anisotropy– Search for photon, neutrino events

• Future projects: TALE, Radar

• Conclusions

3

Cosmic Rays Cover a Wide Energy Range

• At lower energies, spectrum of cosmic rays is almost featureless.

• Only the “knee” at 3x1015 eV • The knee is due to a rigidity-

dependent cutoff, seen in composition.– Kascade experiment: measures

electron and muon components of showers.

– Model dependent, but indicative.– Is it Emax or containment?– Low energy (Ec=3x1017 eV) and

sharp elemental cutoffs limit comes from Emax, rather than containment.

• Learn about galactic sources.• Structure Physics

4

Cosmic Rays Cover a Wide Energy Range

• At lower energies, spectrum of cosmic rays is almost featureless.

• Only the “knee” at 3x1015 eV • The knee is due to a rigidity-

dependent cutoff, seen in composition.– Kascade experiment: measures

electron and muon components of showers.

– Model dependent, but indicative.– Is it Emax or containment?– Low energy (Ec=3x1017 eV) and

sharp elemental cutoffs limit comes from Emax, rather than containment.

• Learn about galactic sources.• Structure Physics

p Fe

5

Has the Fe knee been seen?

• Kascade-Grande Experiment, 2011, measuring electron and muon intensities, may be seeing the Fe end of the Emax transition.

Muon-rich events (high z)

All-particle spectrum

6

Big Change Expected at High Energies

• Expect two spectral features due to interactions between CR protons and CMBR photons.

– GZK cutoff due to pion production.– Dip in spectrum due to e+e- pair

production (the ankle).• Galactic/extragalactic transition.

Galactic (supernova remnants) give heavy composition, extragalactic (AGN’s) give light composition.

• A third spectral feature is seen, second knee.

• Learn about extragalactic sources; and propagation over cosmic distances.

7

A Second Rigidity-Dependent Cycle?

• Galactic magnetic field:– Regular component ~3μG,

follows the spiral arms– Random component ~5μG,

50-100 pc coherence length– Critical energy, where Larmor

radius = coherence length: Ec ~ 1017.5 eV for protons, 1018.9 eV for Fe

– Confinement for galactic particles;

– Exclusion for extragalactic particles

• Galactic – extragalactic transition. Emax Ec

8

A Second Rigidity-dependent Cycle?

• HiRes prototype+MIA hybrid experiment, 1999.

• Best evidence for galactic-extragalactic transition

9

Today’s Issues

• Anisotropy. What are the sources?– The biggest question.– Both galactic and extragalactic magnetic fields get in the way:

the highest energy events are important.

• Composition. Protons, Fe, or what?– How does composition vary with energy?– Disagreement among experiments.

• Spectrum. – There exists an absolute energy calibration: the GZK cutoff

5-6x1019 eV --- if protons. GZK develops in ~50 Mpc.– If heavy nuclei, spallation breaks them up above ~4x1019 eV,

and distances < 50 Mpc.

• Everything talks to composition.

10

Cast of Characters

• Telescope Array (TA) Experiment– Located in Utah.– Largest experiment in northern hemisphere.

• High Resolution Fly’s Eye (HiRes) Experiment– Located in Utah.

• Pierre Auger (PAO) Observatory– Located in Argentina.– Largest experiment.

• Akeno Giant Air Shower Array (AGASA)• Kascade, Kascade-Grande

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Telescope Array CollaborationT Abu-Zayyad1, R Aida2, M Allen1, R Azuma3, E Barcikowski1, JW Belz1, T Benno4, DR Bergman1,

SA Blake1, O Brusova1, R Cady1, BG Cheon6, J Chiba7, M Chikawa4, EJ Cho6, LS Cho8, WR Cho8, F Cohen9,K Doura4, C Ebeling1, H Fujii10, T Fujii11, T Fukuda3, M Fukushima9,22, D Gorbunov12, W Hanlon1, K Hayashi3, Y Hayashi11, N Hayashida9, K Hibino13, K Hiyama9, K Honda2, G Hughes5, T Iguchi3,

D Ikeda9, K Ikuta2, SJJ Innemee5, N Inoue14, T Ishii2, R Ishimori3, D Ivanov5, S Iwamoto2, CCH Jui1, K Kadota15, F Kakimoto3, O Kalashev12, T Kanbe2, H Kang16, K Kasahara17, H Kawai18, S Kawakami11,

S Kawana14, E Kido9, BG Kim19, HB Kim6, JH Kim6, JH Kim20, A Kitsugi9, K Kobayashi7, H Koers21, Y Kondo9, V Kuzmin12, YJ Kwon8, JH Lim16, SI Lim19, S Machida3, K Martens22, J Martineau1, T Matsuda10,

T Matsuyama11, JN Matthews1, M Minamino11, K Miyata7, H Miyauchi11, Y Murano3, T Nakamura23, SW Nam19, T Nonaka9, S Ogio11, M Ohnishi9, H Ohoka9, T Okuda11, A Oshima11, S Ozawa17, IH Park19,

D Rodriguez1, SY Roh20, G Rubtsov12, D Ryu20, H Sagawa9, N Sakurai9, LM Scott5, PD Shah1, T Shibata9, H Shimodaira9, BK Shin6, JD Smith1, P Sokolsky1, TJ Sonley1, RW Springer1, BT Stokes5, SR Stratton5,

S Suzuki10, Y Takahashi9, M Takeda9, A Taketa9, M Takita9, Y Tameda3, H Tanaka11, K Tanaka24, M Tanaka10, JR Thomas1, SB Thomas1, GB Thomson1, P Tinyakov12,21, I Tkachev12, H Tokuno9, T Tomida2,

R Torii9, S Troitsky12, Y Tsunesada3, Y Tsuyuguchi2, Y Uchihori25, S Udo13, H Ukai2, B Van Klaveren1, Y Wada14, M Wood1, T Yamakawa9, Y Yamakawa9, H Yamaoka10, J Yang19, S Yoshida18, H Yoshii26, Z Zundel1

1University of Utah, 2University of Yamanashi, 3Tokyo Institute of Technology, 4Kinki University, 5Rutgers University, 6Hanyang University, 7Tokyo University of Science, 8Yonsei University,

9Institute for Cosmic Ray Research, University of Tokyo, 10Institute of Particle and Nuclear Studies, KEK, 11Osaka City University, 12Institute for Nuclear Research of the Russian Academy of Sciences,

13Kanagawa University, 14Saitama University, 15Tokyo City University, 16Pusan National University, 17Waseda University, 18Chiba University 19Ewha Womans University, 20Chungnam National University,

21University Libre de Bruxelles, 22University of Tokyo, 23Kochi University, 24Hiroshima City University, 25National Institute of Radiological Science, Japan, 26Ehime University

U.S., Japan, Korea, Russia, Belgium

12

TA is a Hybrid Experiment

• TA is in Millard Co., Utah, 2 hours drive from SLC.

• SD: 507 scintillation counters, 1.2 km spacing, scintillator area= 3 sq. m., two layers.

• FD: 3 sites, each covers 120° az., 3°-31° elev.

• ~3.8 years of data have been collected.

1313

Long Ridge Black Rock Mesa

Middle DrumRefurbishedfrom HiRes

~30km New FDs

6.8 m2 ~1 m2

14 cameras/station256 PMTs/camera

5.2 m2

TA Fluorescence Detectors

Observation started Dec. 2007

Observation started Nov. 2007

Observation started Jun. 2007

256 PMTs/cameraHAMAMATSU R9508

FOV~15x18deg12 cameras/station

14

Typical Fluorescence Event

Black Rock Event Display

Monocular timing fit Reconstructed Shower Profile

Fluorescence

Direct (Cerenkov)

Rayleigh scatt.

Aerosol scatt.

15

TA Surface Detector

• Powered by solar cells; radio readout.

• Self-calibration using single muons.

• In operation since March, 2008.

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r = 800m

Typical surface detector event

Lateral Density Distribution Fit

Geometry Fit (modified Linsley)

Fit with AGASA LDF

• S(800): Primary Energy • Zenith attenuation by MC

(not by CIC).

2008/Jun/25 - 19:45:52.588670 UTC

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Stereo and Hybrid Observation

• Many events are seen by several detectors.– FD mono has ~5° angular resolution.– Add SD information (hybrid reconstruction) ~0.5°

resolution.– Stereo FD resolution ~0.5°

• Need stereo or hybrid for composition analysis.

• Independent operation until 2010.• Hybrid trigger is in operation now.

18

Cosmic Ray Spectrum

• Status: the GZK cutoff was first observed by HiRes; Auger sees it also.

• The ankle shows up clearly in both spectra.

19

TA Spectrum (Measured by the Surface Detector)

• 3 years of data, 10997 events.

• We use a new analysis method.– Must cut out SD events with bad resolution.

Must calculate aperture by Monte Carlo technique.

– This is an important part of UHECR technique, and must be done accurately.

– We use HEP methods for this purpose.

20

SD Monte Carlo• Simulate the data exactly as it exists.

– Start with previously measured spectrum and composition.

– Use Corsika/QGSJet events (solve “thinning” problem).

– Throw with isotropic distribution.– Simulate trigger, front-end electronics, DAQ.

• Write out the MC events in same format as data.

• Analyze the MC with the same programs used for data.

• Test with data/MC comparison plots.

21

How to Use Corsika Events

• Use 10-6 – thinned CORSIKA QGSJET-II proton showers that are de-thinned in order to restore information in the tail of the shower.

• De-thinning procedure is validated by comparing results with un-thinned CORSIKA showers, obtained by running CORSIKA in parallel

• We fully simulate the SD response, including actual FADC traces

De-thinned

10-6 thinning

Distance from Core, [km]

VEM

/ C

ou

nte

r

ThinnedNo thinning

De-thinnedNo thinning

RMS

Mean

22

Dethinning Technique

• Change each Corsika “output particle” of weight w to w particles; distribute in space and time.

• Time distribution agrees with unthinned Corsika showers.

23

Fitting results

• Fitting procedures are derived solely from the data

Tim

e fi

t re

sid

ual over

sig

ma

Counter signal, [VEM/m2]

DATA

24

Fitting results• Fitting procedures are

derived solely from the data

• Same analysis is applied to MC

• Fit results are compared between data and MC

• MC fits the same way as the data.

• Consistency for both time fits and LDF fits.

• Corsika/QGSJet-II and data have same lateral distributions!T

ime fi

t re

sid

ual over

sig

ma

Counter signal, [VEM/m2]

DATA

MC

25

Data/MC Comparisons

Azimuth angleZenith angle

26

Data/MC Comparisons

Core Position (E-W) Core Position (N-S)

27

Data/MC Comparisons

LDF χ2/dof Counter pulse height

28

Data/MC Comparisons

S800Energy

29

First Estimate of Energy

• Energy table is constructed from the MC

• First estimation of the event energy is done by interpolating between S800 vs sec(θ) lines

30

Energy Scale

• SD and FD energy estimations disagree

• FD estimate possesses less model-dependence

• Set SD energy scale to FD energy scale using well-reconstructed events from all 3 FD detectors

• 27% renormalization.

31

Acceptance

32

SD Energy Spectrum:Broken Power Law Fit

GZK: pion photoproduction Ankle: e+e- production

33

SD Energy Spectrum:GZK Feature

34

SD Energy Spectrum:Integral Flux E1/2 Measurement

E1/2 = 1019.69 eV

Berezinsky et al. predict 1019.72 eV

35

Comparison with theoretical model

• Assume constant density of sources, calculate the “modification factor” due to propagation; compare with HiRes and TA data.

36

SD Energy Spectrum:Comparison

● TA SD

▼ HiRes-II

▲ HiRes-I

37

SD Energy Spectrum:Comparison

● TA SD

■ Auger 2008 (PRL) +20%

▲ Auger 2011 (ICRC) +20%

38

Fluorescence Detector (FD) Monocular Spectrum

• For FD (mono, hybrid, stereo) measurements, the aperture depends significantly on energy. Must calculate it by Monte Carlo technique.

• This is an important part of UHECR technique, and must be done accurately.

• We use HEP methods for this purpose.

39

MC Method• Simulate the data exactly as it exists.

– Start with previously measured spectrum and composition.

– Use Corsika/QGSJet events.– Throw with isotropic distribution.– Include atmospheric scattering.– Simulate trigger, front-end electronics, DAQ.

• Write out the MC events in same format as data.

• Analyze the MC with the same programs used for data.

• Test with data/MC comparison plots.• This method works.

40

DATA/MC Comparisons

Rp Zenith angle

41

FD and SD Energy Spectra:

42

Composition from Xmax

Depth [g/cm2]

Num

ber o

f cha

rged

par

ticle

Shower longitudinal developmentShower longitudinal development

XmaxXmax

• Shower longitudinal development depends on primary particle type.

• FD observes shower development directly.• Xmax is the most efficient parameter for

determining primary particle type.

• Shower longitudinal development depends on primary particle type.

• FD observes shower development directly.• Xmax is the most efficient parameter for

determining primary particle type.HiResHiRes

AugerAuger

PRL.104.161101 (2010)

PRL.104.091101 (2010)

43

TA FD Stereo Composition

• Measure xmax for Black Rock/Long Ridge FD stereo events

• Create simulated event set

• Apply exactly the same procedure as with the data

• This measurement is independent of HiRes and Auger.

44

Data/MC Comparison QGSJETIIProtonIron

Zenith Azimuth Rp

Xcore Ycore Psi

45

Data/MC Comparison QGSJETIIProtonIron

Track length # of P.E. # of PMT

Likelihood Xstart Xend

46

Prediction of <Xmax>, directly from CORSIKA

47

Prediction of <Xmax>, Reconstructed

These rails which include acceptance and reconstruction bias can be compared with data

48

Energy vs <Xmax>

49

Xmax distribution (1018-20eV)

QGSJET-II QGSJET01 SIBYLLProtonIron

Preliminary Preliminary Preliminary

50

Xmax dist. QGSJET-II18.2 < logE < 18.4 18.4 < logE < 18.6

18.6 < logE < 18.8 18.8 < logE < 19.0

Preliminary Preliminary

Preliminary Preliminary

51

Xmax dist. QGSJET-II19.0 < logE < 19.2 19.2 < logE < 19.4

19.4 < logE < 19.6 19.6 < logE < 19.8

Preliminary Preliminary

Preliminary Preliminary

52

Xmax dist. : KS Test

95% C.L.

Preliminary

53

Simple Tests There exist simple tests (not

dominated by systematics) to check composition results; e.g., zenith angle

comparison plots.

protons

iron

HiRes fluorescence detector TA surface detector

54

Search for AGN Correlations• Auger found correlations

with AGN’s with (57 EeV, 3.1°,0.018). 14 events scanned + 13 event test sample appeared in Science article; 2.9σ chance probability.

• Later Auger data (71, 19, 16) show no significant correlations.

• HiRes data (13, 2, 3) show no significant correlations.

• TA data (20, 8, 5) show no significant correlations.

TA AGN Correlations

55

Search for Correlations with Local Large Scale Structure

METHOD• The flux distribution over the sky is calculated from the actual

distribution of galaxies (2MASS XSCz catalog, T. Jarrett, private communication)

• 110 000 galaxies at distances from 5 Mpc to 250 Mpc are included• The flux from beyond 250 Mpc is taken uniform• Proton primaries are assumed• All interaction and redshift losses are accounted for• Gaussian smearing is applied with the angular size treated as a free

parameter. At small angles, this mimics the deflections in magnetic field and finite angular resolution.

• The predicted flux is compared to the data by the flux sampling test

56

Data, and ModelsE > 10 EeV E > 40 EeV

E > 57 EeV

(smearing angle = 6°)

57

Results of K-S Test

58

Add Galactic Magnetic Field

59

Flux Map and K-S Plot

60

Search for Photons and Neutrinos

Photons:

Use curvature of shower front.

Neutrinos:

Use old/new shower discriminant: number of muon peaks in FADC trace.

61

TA Low Energy Extension (TALE)

• A lot of physics was skipped in the push to observe the GZK cutoff. Study the 1016 and 1017 eV decades with a hybrid detector.– End of the rigidity-dependent cutoff that starts with the

knee (at 3x1015 eV).– The second knee– The galactic-extragalactic transition

• Need to observe from 3x1016 eV to 3x1020 eV all in one experiment. That is TA and TALE.

62

TALE FD

• Add 10 telescopes at the Middle Drum site, looking from 31°-59° in elevation.

• Operate in conjunction with the TA Middle Drum FD.

• Together cover 1016.5 < E < 1020.5 eV

TALE hybrid events per year

TAmirrors

TALEmirrors

63

TALE Infill Array

• Add infill array (400m and 600m spacings) for hybrid and stand-alone observation.

• Also add counters to build out main TA SD array (1200m separation).

• 105 counters in all.

Events per year

64

R&D on Radar Detection of Cosmic

Ray Showers• Rates at the highest

energies are too low need bigger experiments.

• Bistatic radar detection:– Remote sensing– Inexpensive– 100% duty cycle

“chirp”Chirp detection by matched filters (0db above noise)

65

Conclusions

• The Telescope Array (TA) Experiment is collecting data in the northern hemisphere.

• TA is a LARGE experiment which has excellent control of systematic uncertainties.

• SD mono, FD mono, stereo, hybrid, hybrid-stereo analyses are all ongoing.

• Important TA spectrum, composition, and anisotropy results are being presented. With more to come.

• TA is a discovery experiment.