1. A Complex Detector Array at the Tibet Cosmic Ray Observatory
Zhen Cao
Institute of High Energy Physics, China, Beijing
TeVPA08, Beijing, China, September, 2008

2. Outline Motivation and scientific goals
Tentative design of the detector array
Components and performance
Tentative time schedule
Cost estimates
Conclusion

3. 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 borne measurements and ground based measurements
Searching for Dark Matter galactic sub-structures

4. Aharonian et al., 2006 (astro-ph/0611813)
RXJ at TeV energies
SNR ~1600 years old,
distance of 1kpc.
TeV emission seen by CANGAROO (2000)
HESS observation (since 2003)
~90h live
53 s
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/ )

5. RXJ1713.7-3946 ASCA data: (synchrotron X rays)
Leptonic 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 sIC/sSync a B-2 )
Hadronic model favored
Hadronic model
Still pending:
Hadronic model to be confirmed
Occurence of such objects? (cf scan)

6. 50+ are galactic without absorption Many 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

7. Mrk 421/501 Long term Variability
Mrk 421 by ARGO
Mrk 421 by ASM of RXTE

8. CR spectrum around “knee”
Over 50 yrs, results are unsatisfactory
The best location is at high altitude
Solution is E-spectrum for individual composition

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

10. 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

11. Future plan for a complex of CR+γdetectors
WCD: 4x104m2
μ : 100x400m2
e : x1m2
CT: 28
BD: 1000x1m2
AS+μ:
ARGO: 104m2

12. γ/p discrimination γsurvival rate ~99% Angular resolution 0.5°
Above 60TeV
CR BG-free(10-5)
γsurvival rate ~99%
Angular resolution 0.5°

13. Sensitivities for 100TeV γsky
E-resolution 60%
Without reconstruction

14. Expectation: if HESS sources are in the field of view
HESSJ
Ec=1PeV
Ec=100TeV
YBJ
1km2

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

16. Sensitivities for γsources >500GeV wide FOV scanning for source population
5σper year (24%duty cycle)
for sources like Crab in
the whole field of view
Important
complementary
to each other
5σper 50hrs for a
single source like
Crab

17. Resolution for light and heavy composition μ-content, Xmax and HE (>30TeV) shower particles

18. DICE-type C-telescope for Xmax (expect aΔXmax~50g/cm2)
Very preliminary result
without C-light emitting
angle correction

19. Cost Free high energy (1EeV)extension
Re-Configuration
Tower CT: 16
μ : 100x400m2
Side Trigger CT: 2x4

20. Aperture of HEE Event rate ~25k/yr

21. knee
Second knee
We are here

22. A bridge between balloon measurements and ground base UHECR experiment covering both “knees” with uniform energy scale

23. Dark Matter g-rays from the sub-halos
ARGO sensitivity
LHAASO sensitivity
Reed et al, MNRAS357,82(2004)
source
Then we get the gamma ray flux from the subhalos? The peaks represent the gamma ray flux from different subhalos at different directions. Psi is the angle between the source and the GC. y
g-rays from smooth bkg
sun GC

24. Tentative time schedule
Phase I (a half of the full scale array)
Detector R/D: (test run with small array) 1yr
Detector Producing & deployment: yr
Electronics R/D: yr
Electronics production: yr
DAQ for low energy γdetector array: 4yr
Test operation for 1 year
Phase II (complete the whole array for 3yr)

25. Cost estimates (MUSD) e detector： 3.4 + (2400m2)
μdetector： (40k m2)
= 48.0
C-telescopes： (28 telescopes)
Burst detector: (1k m2)
Water C-detector: (90k m2)
Data management: 4.3
subtotal：
Operational budget: 4.0/yr (for 10yrs)

26. 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

27. Idea from Magic Coll.

28. You are invited to Lhaaso at Lhasa!
Large High Altitude Air Shower Observatory
You are invited to Lhaaso at Lhasa!