A Complex Detector Array at the Tibet Cosmic Ray Observatory

Zhen CaoInstitute of High Energy Physics, China, Beijing 100049

TeVPA08, Beijing, China, September, 2008

Outline

• Motivation and scientific goals

• Tentative design of the detector array

• Components and performance

• Tentative time schedule

• Cost estimates

• Conclusion

Motivation & Scientific goals

• TeVγray observation has an opportunity to find CR sources: 60+ sources discovered– 50+ galactic: high energy (>30TeV) is crucial

(high sensitivity and high energy resolution)– Source population & temporal feature are important

(full duty cycle and sufficient sensitivity)

• PeV CR spectra of individual composition– Bridge at high altitude (4300m) between space/balloon b

orne measurements and ground based measurements

• Searching for Dark Matter galactic sub-structures

RXJ1713.7-3946 at TeV energies•SNR ~1600 years old, distance of 1kpc.

• TeV emission seen by CANGAROO (2000)

•HESS observation (since 2003)– ~90h live– 53 – resolved morphology

(1st time at TeV energy):• Shell structure• Strong coincidence with X

map (ASCA)

Unambiguous proof of SNRs shocks as acceleration sites Aharonian et al., 2006 (astro-ph/0611813)

Hadronic model

ASCA data:

(synchrotron X rays)• Fine structures in the radiation

morphology points to B>100µG• If leptonic, X/TeV ratio requires

B~10µG (with IC/Sync B-2 )

Hadronic model favored

RXJ1713.7-3946 Leptonic model

Still pending: Hadronic model to be confirmed Occurence of such objects? (cf scan)

50+ are galactic without absorptionMany SNRs, WRs and OB ass.E-spectra only up to 10TeV

Many varying sources > 0.05ICrab

1.44x10-16ph/cm2s

1.35PeV

Accurate measurements of spectra of γsources are crucial for finding CR sources

Mrk 421/501 Long term Variability

Mrk 421 by ASM of RXTE

Mrk 421 by ARGO

CR spectrum around “knee”• Over 50 yrs, results are

unsatisfactory• The best location is at

high altitude • Solution is E-spectrum for

individual composition

The keys are to lower threshold, making connections with direct measurements & measure spectra up to 100PeV

Tentative design of the complex detector array

Two major components• 1km2 complex array forγrays and CRs >30TeV

– 1 km2 scintillation detector array– 40k m2 μdetector array– 28 C-telescopes– 1k m2 burst detector

• 90k m2 water Cerenkov detector for γ>100GeV

WCD: 4x104m2

μ : 100x400m2

e : 2400x1m2

CT: 28

BD: 1000x1m2

AS+μ:

ARGO: 104m2

Future plan for a complex of CR+γdetectors

γ/p discrimination• Above 60TeV

CR BG-free(10-5)

• γsurvival rate ~99%

• Angular resolution 0.5°

Sensitivities for 100TeV γsky

E-resolution 60%Without reconstruction

HESSJ 1614-518 1616-508 1632-478 1634-472 1702-420 1708-410 1713-381 1745-303 1804-216 1834-0871837-069

Ec=1PeVEc=100TeV

YBJ1km2

Expectation: if HESS sources are in the field of view

Should look for old SNRs (J.Fang&L.Zhang, arXiv:0711.4173 )

Sensitivities for γsources >500GeVwide FOV scanning for source population

5σper year (24%duty cycle)for sources like Crab in the whole field of view

5σper 50hrs for a single source like Crab

Important complementary to each other

Resolution for light and heavy composition

μ-content, Xmax and HE (>30TeV) shower particles

DICE-type C-telescope for Xmax (expect aΔXmax~50g/cm2)

Very preliminary resultwithout C-light emitting angle correction

Cost Free high energy

(1EeV)extension

Tower CT: 16

μ : 100x400m2

Side Trigger CT: 2x4

Re-Configuration

Aperture of HEEEvent rate ~25k/yr

knee Sec

ond

knee

We are here

A bridge between balloon measurements and ground base UHECR experimentcovering both “knees” with uniform energy scale

Dark Matter-rays from the sub-halos

Reed et al, MNRAS357,82(2004)

LHAASO sensitivityLHAASO sensitivity

-rays from smooth bkg-rays from smooth bkg

source

sun GC

ARGO sensitivity

Tentative time schedule

• Phase I (a half of the full scale array)– Detector R/D: (test run with small array) 1yr – Detector Producing & deployment: 3yr– Electronics R/D: 2yr– Electronics production: 2yr– DAQ for low energy γdetector array: 4yr

• Test operation for 1 year• Phase II (complete the whole array for 3yr)

Cost estimates (MUSD)

• e detector ： 3.4 + (2400m2) μdetector ： 44.6 + (40k m2) = 48.0• C-telescopes ： 4.0 (28 telescopes)• Burst detector: 3.0 (1k m2)• Water C-detector: 58.0 (90k m2)• Data management: 4.3

• subtotal ： 117.3

• Operational budget: 4.0/yr (for 10yrs)

Conclusion

• Plan to build a ground based large and complexγ/CR observatory at high altitude (4300m a.s.l.) within 10 years– Complementary to CTA in γastronomy– Unique for CR measurements at Knees– Promising DM detection

• Tentative proposal submitted to CAS (review cycle will start next month)– A separate proposal for R/D is approved (last month)

• Completely open to colleagues on collaborating and optimizing the instruments

Idea from Magic Coll.

You are invited to Lhaaso at Lhasa!

Large High Altitude Air Shower Observatory