The Large High Altitude Air Shower Observatory LHAASO

Science case for LHAASO – Survey of the γ-ray sky above 100 Ge. V – – Wide FOV and high duty cycle Observation of transient sources Extended sources / diffuse emission / halos Study cosmic accelerators and high-energy phenomena – Search for cosmic-ray origin among galactic gamma-ray sources – Gamma spectra at high energies – Visibility for hadronic origin and charged particle acceleration – Measurement of cosmic rays above 30 Te. V – Bridge between direct and indirect measurements – Unprecedented statistics for anisotropy studies in the knee region – New Physics and other studies – Dark matter – Quantum gravity

HE γ-ray detection Fermi (0. 1 -300 Ge. V) High duty cycle Large field of view BUT Limitated energy HESS, MAGIC, VERITAS, CTA 100 Ge. V- 30 Te. V Good p-γ separation Good angular resolution BUT Low duty cycle and Limited fov (4°) MILAGRO, ARGO, HAWC 1 -100 Te. V High duty cycle Large field of view BUT Lower rejection power and low angular resolution

Identification of hadronic emission To identify an hadronic emission: - Fermi: 100 Me. V-few Ge. V, difficult to interpret (low energy/space resolutions, geometry, jet composition, boost factors…) - Above 50 -100 Te. V, leptonic emission suppressed by Klein-Nishina absorption => clear identification - Graal: detection of HE neutrino SNR IC 443

Experimental strategy • Gamma-ray source survey: Water Cherenkov Detector Array (WCDA) with a total active area of 90000 m 2 • High-energy end of the gamma spectra: Particle detector array with an effective area of 1 km 2 (KM 2 A) including an array of 1200 muon detectors (MD) with 940 000 m 2 active area and an array of 5000 scintillators (ED) (allows to reject hadronic shower background) • Cosmic-ray spectra and composition: 24 wide FOV Cherenkov telescope array (WFCA) and high threshold core detector array (SCDA) with an effective area of 5000 m 2. Accurate measurement of composition by combining information from KM 2 A

Survey of gamma sources Calculation is based on a one-year observation of the Crab for detection at 5 σ level. IACT for 50 h exposure

SED, morphology Sky survey, extended, transient ARGO Area AS+MD HAWC LHAASO CTA 1 km 2 10 km 2 0. 1 -0. 5 0. 05 100/104 100 >90% 10% 2 2 0. 015 0. 06 0. 01 0. 3 30% 15% 6, 500 m 2 50000 m 2 22500 m 2 θ(deg) 0. 2 -0. 5 BG rejection power Duty Cycle FOV (sr) @1 Te. V 104 >90% 2 2 0. 55 Sensitivity @100 (c. u. ) Te. V Energy resolution 0. 2 -0. 5 0. 25 30% >50%

Main drawbacks • Located in the Northern hemisphere while CTA will be in the South (for the first phase) • No so clear science case for extragalactic sources (strong attenuation with EBL). Very close horizon.

Prospects of CR Physics • 30 Te. V - 10 Pe. V – Energy scale – Knees for H, He, … – Anisotropy • 10 Pe. V - 100 Pe. V – Composition – Energy spectrum: knee of Fe • 100 Pe. V - 2 Ee. V – Spectrum bending and composition changing – Transition from galactic to extra-galactic

Back tracking of cosmic accelerators by CR CEN A Auger: Arrival direction compared to AGN catalogue VGV • At low energies, significant anisotropies in arrival direction (dipoles and higher order multipoles) have been observed • At the highest energies, above 55 Ee. V, some correlations with nearby extragalactic matter have been found but no clear identification of sources Origin of cosmic rays is still an open question!

Complementary to CTA LHAASO: Continuous, wide field of view survey (need only one year to detect all Fermi sources at Te. Vs and at 1%Crab) CTA: Detailed source morphology studies LHAASO: Study of extended sources LHAASO: Higher energies than CTA =>hadron processes LHAASO: Source variability monitoring

LHAASO layout Central detector array for cosmic rays 90 km 2 gamma ray survey telescope 1 Mm 2 surface EAS detector array

LHAASO observatory 24 Wide FOV air Cherenkov image Telescopes. 400 burst detectors for high energy secondary particles near the core of air showers LHAASO Layout in 1 km 2 at 4300 m a. s. l. 90 km 2 Water Cherenkov Detector array. Each one has a size of HAWC 6100 scintillator detectors and 1200 μ-detectors form an array covering 1 km 2

Status • LHAASO has been included in the roadmap of the infrastructure construction for basic science in a short term, (5 years). Total 16 projects are included. • LHAASO is also mentioned in the European roadmap for Astroparticle Physics. • Site selected • Technology that used in LHAASO are currently tested with engineering arrays at scales of 1%-10% of the full project • Steps ahead: environment impact evaluation, feasibility reviewing, TDR reviewing • “Pre-LHAASO” project LAWCA consisting of one single water Cherenkov chamber of 220 mx 110 m to be built side-by-side with the ARGO-YBJ RPC array is under construction.

The formal proposal is sent to CCDR, the review on the proposal is expected to be finished in 2014 and completed in 2018 HAWC Construction Uncertain! could be 12 m from now or earlier

Collaboration • ~80 Chinese scientists • • • France: IPNO + OMEGA (Letter of Intend) Italia: mainly participants in ARGO Russia: collaborators from TUNKA

Conclusion • A ground based large and complex γ/CR observatory at high altitude (4300 m a. s. l. ) within 5~6 years – γ astronomy: all sky survey and spectroscopy – Unique for CR measurements at the knees – Useful for exploring for new physics • • Site is decided Management structure is established The construction is scheduled to start in next year Forming the Collaboration