1. Yu.V. Stenkin, Beijing'20111 On the PRISMA project and the cosmic ray knee problem Yuri V. Stenkin Institute for Nuclear Res. of RAS, Moscow, Russia

2. Yu.V. Stenkin, Beijing'20112 The Project aims Why PRISMA? PRImary Spectrum Measurement Array The main goal is: TO SOLVE THE “KNEE PROBLEM” Other aims: –cosmic rays spectra and mass composition –cosmic ray sources –applied Geophysical measurements

3. Yu.V. Stenkin, Beijing'20113 History & Motivation Why do we need a new project? 1. The “knee problem” is a milestone of the cosmic ray physics. 2. Very few experiments have been designed specially for that. (KASCADE and Tibet AS  are the best ones). 3. The problem still exists.

4. Yu.V. Stenkin, Beijing'20114 EAS method Direct measuremens

5. Yu.V. Stenkin, Beijing'20115 The “knee problem” The “knee problem” The problem is more than 50-years old! 1. Astrophysical explanation. In 1958 there was published a paper (G.V. Kulikov & G.B. Khristiansen) claiming the knee existence in cosmic ray energy spectrum. They observed a sharp change of slope in EAS size spectrum and proposed a model describing this effect as an evidence of existence of 2 sources of c. r.: Galactic and Metagalactic ones. 2. Nuclear-physical explanation. From the beginning and up to now there exist alternative explanations of this effect by dramatic change of particle interactions at these energies (S.I.Nikolsky, Kazanas & Nikolaidis, A.A.Petrukhin). Very few people know that there exist one more explanation.

6. Yu.V. Stenkin, Beijing'20116 3. Phenomenological explanations The knee in electromagnetic component can be explained by a break of equilibrium between the EAS components at energy of ~ 100 TeV / nucleon when the number of cascading hadrons is close to 1 and 0.

7. Yu.V. Stenkin, Beijing'20117 Depth in atmosphere No of particles From Hayakawa manual on cosmic ray physics EAS components equilibrium Break of equilibrium Break in attenuation “knee” in N e spectrum

8. Yu.V. Stenkin, Beijing'20118 When the break occurs? At E~100 TeV / nucleon For p: ~100 TeV For Fe: ~5 PeV (just the knee region) For details see: Yu. Stenkin, Phys. of Atom. Nucl., 71 (2008), 99 This figures are sequences of : L int = 90 g/cm 2 in air the Earth’s atmosphere thickness =1030 g/ cm 2 (depending on altitude)

9. Yu.V. Stenkin, Beijing'20119 I ~ E -  N х ~ E  I ~ N х -  =/=/ if  has a break then  has a knee  - represents a «linearity of the method» spectrum: Secondary component Primary Secondary methods

10. Yu.V. Stenkin, Beijing'201110 Wide range Narrow range CORSIKA results for Ne inside R=1000 m

11. Yu.V. Stenkin, Beijing'201111 This model predicts: - the knee should occur at almost equal N e - first “knee” should be  ~0.35 at N e ~10 4.8 - second “knee” should be  ~0.4 at N e ~10 6.3 - age parameter s should decrease with N e - attenuation length should increase with N e Therefore, it predicts the position and absolute value of the knee!

12. Yu.V. Stenkin, Beijing'201112

13. Yu.V. Stenkin, Beijing'201113 4. Existing experiments Tibet AS vs KASCADE Both gave many interesting results. BUT, they did not answer the question on the knee origin and thus, the knee problem is still open! Moreover, the problem became even less clear…. (see G. Schatz. Proc. 28th ICRC, Tsukuba, (2003), 97; Yu. Stenkin. Proc. 29th ICRC, Pune (2005), v.6, 621; M.Amenomori et al. Astrophys. J, (2008), v.678, 1165)

14. Yu.V. Stenkin, Beijing'201114 Cosmic Rays from the Knee to the Highest Energies Johannes Blumer, Ralph Engel, and Jorg R. Horandel arXiv:0904.0725v1 [astro-ph.HE] 4 Apr 2009

15. Yu.V. Stenkin, Beijing'201115 A. Haungs, J.Kempa et al.(KASCADE) Report FZKA6105 (1998).  0.4 This is their old but correct paper on my opinion

16. Yu.V. Stenkin, Beijing'201116

17. Yu.V. Stenkin, Beijing'201117 to make a device based on new principles and on novel experimental approaches How the problem could be solved? On my opinion the only way is:

18. Yu.V. Stenkin, Beijing'201118 PRISMA could be the solution PRISMA Prism

19. Yu.V. Stenkin, Beijing'201119 New principles The main EAS component is: hadrons Therefore, let us concentrate mostly on the hadronic component Bun, instead of huge and expensive hadron calorimeter of fixed area, let us make simple, inexpensive and of unlimited area detector. How this could be done?

20. Yu.V. Stenkin, Beijing'201120 New Methods New method has been developed in our Lab. in 2001. The method is based on thermal neutron “vapour” accompanying EAS Nn =S N n =  E h   h  h   h, where 

21. Yu.V. Stenkin, Beijing'201121 A novel type of detector sensitive to hadrons (to neutrons) has been developed in our Lab. We called it as en-detector

22. Yu.V. Stenkin, Beijing'201122 The detector is almost insensitive to single charged particles. But, it can measure the number N of charged particles if N>5.

23. Yu.V. Stenkin, Beijing'201123 Thermal neutron time distributions Multicom Prototype, BaksanPrisma prototype, Moscow Conclusion: Recorded neutrons can be of 2 types: local or atmospheric

24. Yu.V. Stenkin, Beijing'201124 neutrons vs local density

25. Yu.V. Stenkin, Beijing'201125 en-detector design 6 Li(n,a) 3 H+4.8 MeV 160,000 photons per capture ZnS(Ag) is a unique scin- tillator for heavy particles detection: Scintillator: ZnS(Ag)+ 6 LiF Similar to that using in neutron imaging technique 1 -PE water tank,  =72 cm, h=57 cm 2 -lid  =30 см 3 - 6’’ PMT 4 - scintillator, s=0.35 м 2 5 - reflecting cone

26. Yu.V. Stenkin, Beijing'201126 en-detector design

27. Yu.V. Stenkin, Beijing'201127 2d new method: The Muon Detector (MD) as a 1-layer hadronic calorimeter

28. Yu.V. Stenkin, Beijing'201128 Schematic view of Baksan Muon Detector

29. Yu.V. Stenkin, Beijing'201129 Preliminary Baksan data: hadrons at R=47m

30. Yu.V. Stenkin, Beijing'201130 Schematic view of Baksan Muon Detector 3d new method

31. Yu.V. Stenkin, Beijing'201131 Hadron - neutron correlation in MD

32. Yu.V. Stenkin, Beijing'201132 Carpet: 400*1m 2 en-detectors grid with spacing of 5 m Central muon detector: 400*1m 2 plastic scinillators Muon detector tunnels: 1200*1m 2 plastic scintillators Outer trigger detectors: 4*25*1m 2 plastic scintillators

33. Yu.V. Stenkin, Beijing'201133 LOG10(Ne)= 75(67) Nmu= 612 E0/1TeV= 10015 M=7 x0= -27.53 y0= -18.36 TETA= 21.7 FI= 79.3 Z= 11.98 Km Part_type= 14 M-C simulations. CORSIKA 6.900 + PRISMA array A map of the event: m=10*LOG10(n)

34. Yu.V. Stenkin, Beijing'201134 P, 171 TeV, Ne=10**5.3Fe, 147 TeV, Ne=10**5.2

35. Yu.V. Stenkin, Beijing'201135 Main features: Range in primary energy: from ~10 TeV to ~30 PeV energy resolution: ~ 10 - 20 % angular resolution: ~ 1 o core location:< 2.0 m capability to measure EAS size independently in: e, n and  capability to select AS with equal E/nucleon

36. Yu.V. Stenkin, Beijing'201136 M-C

37. Yu.V. Stenkin, Beijing'201137 P E thr  10 TeV / nucleon

38. Yu.V. Stenkin, Beijing'201138 Neutron time distributions for different primaries

39. Yu.V. Stenkin, Beijing'201139 EAS size distributions in different components

40. Yu.V. Stenkin, Beijing'201140 A prototype of PRISMA (ProtoPrisma) 16 en-detectors Location: on 4th floor inside building in MePhi, Moscow

41. Yu.V. Stenkin, Beijing'201141 NEVOD 11 12 13 14 15 16 In 2011 the array will be enlarged up to 32 - 36 detectors

42. Yu.V. Stenkin, Beijing'201142 The first large EAS recorded by ProtoPrisma

43. Yu.V. Stenkin, Beijing'201143 Geophysical researches 1. Neutron background monitoring 2. Study of the detector response to geophysical events 3. Study of the radon-due tidal waves 4….. 5….. Another advantage of the en-detector is its possibility to measure thermal neutron flux of low intensity and its variations

44. Yu.V. Stenkin, Beijing'201144 Inter correlation coefficients are equal to from 0.87 to 0.95 Neutron array Counting rate stability

45. Yu.V. Stenkin, Beijing'201145

46. Yu.V. Stenkin, Beijing'201146 Location Collaboration Institutions budget high altitude is preferable Tibet would be the best location It depends on:

47. Yu.V. Stenkin, Beijing'201147 Involved Institutions: 1. Institute for Nuclear Research, Moscow 2. MEPhI, Moscow 3. Skobeltsyn Institute, MSU, Moscow 4. 5. To be continued... Both collaborations are open for other participants. We should combine our efforts!

48. Yu.V. Stenkin, Beijing'201148 Thank you! Instead of conclusion