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Title: Reflections about EXChALIBUR, the exclusive 4pi detector for EXCLUSIVE measurements of hadronic interactions needed for deeper understanding of QCD Summary: This provocative title is intended to call for the attention, emphasizing the brainstorming nature of this proposal in the spirit of the call for abstracts: "Proposals at all stages of advancement are requested and novel ideas are particularly encouraged." The acronym means: EXClusive HAdron and Lepton Instrument for Basic Universal Research. One is looking for the answer to two questions: Can exclusive experiments help to understand QCD? Is it possible to build complete 4pi detector? One tries to identify the technical limits which could be reachable within 5 to 10 years in the quest for the ideal particle physics detector in the SPS energy range. Content: The aim of this detector is to provide full 4pi coverage which can be assured only by fixed target arrangements, by definition. This proposal is an implicit continuation of large acceptance detectors as NA61/SHINE at SPS and CBM at FAIR, which provide almost full coverage for the forward hemisphere. The proposal intends to build in a not far future a 10th ( "X" ) generation detector applying technologies like: Diamond-TPC, high-grain Silicon calorimetry, GEMs, n-XYTER type read-out technology, interactions in high intensity beam with full online pattern recognition, based on data-driven massively parallel SIMD computing architecture, producing data on the EXA-byte scale per year. One should use as many type of beams as possible: gamma, electron, muon, pion, Kaon, proton, deuteron, alfa, and any heavy ion, which are readily available in the North Area between 10 and 300 GeV with reasonable intensity characteristic to each type of beam particle. The target nuclei also can include any element of the periodic table. We assume the application of small (not exceeding 1 cm ) solid targets. The detector should be able to record and reconstruct in full phase-space particle types: gamma, electron, muon, pion, charged Kaon, Kshort, proton, neutron (together with Klong), deuteron, lambda (ksi, omega minus, etc). What are the physics plusses gained by this miraculous detector? Due to the unsolvability of QCD we don't have explicit solution for any hadron-hadron or lepton-hadron process. Practically all the knowledge in experimental QCD is based on inclusive measurements, which of course gives only the fraction of the possible information. The GENERIC EXCLUSIVITY would give qualitatively new massive amount of information to work out new theoretical approaches. The situation is similar to the Human Genome problem. The first experiments revealed, that the genetic information is coded in the nuclein acids (DNA), inclusive measurement revealed that only 4 amino acids are used in the coding. One can make this "inclusive" measurements by simply breaking the double-helix chain and count the end products. The real understanding of the code came after "exclusive" mapping along the chain, where we are now. Which is, of course, still not the end of the story. An other aspect which calls for this "stamp collecting" exclusive procedure is represented by the GPS example. The GPS idea is perfect for military purposes if one interested in the correct position of the flying warhead. But it became a universal tool for the mankind only after Google made the meticulous work of mapping every street and house in the data base. Why should it be built at SPS? The SPS energy range is full of mysteries which were completely forgotten after the closure of ISR. One can just enumerate few examples: -Myterious transition of inclusive spectra around 80 90 GeV energy from convex to concave form. -Emergence of Cronin-effect in pA interactions is completely unknown: energy, centrality particle type dependence, particle correlations. -Practically no medium or high pT data between beam energies 24 and 200 GeV. -Is there a Critical Point on the AA phase diagram? (Hopefully the YES/NO answer will be given soon by NA61/SHINE experiment, but the finer details calls for deeper studies.) -Is there threshold for Jet-quenching which was observed at RHIC at higher energies? -How the jets are emerging??? -Where are the glueballs, pentaquarks,...? -etc. Due to the fact that in this region the multiplicities are still relatively modest one have more chance to identify characteristic features. Bohr was using the spectral lines of Hydrogen and not the ones of Lead. In short: We should find "the Lyman and Balmer series" for QCD. Due to the fact that QCD is so many times more complicated than QED we need EXA-Bytes instead of the few Bytes of Bohr. The complication is mainly arising from the fact that the hadrons are extended objects in space in contrast to point-like leptons. In this situation one should grab any possibility to collect new information which can provide insight into the space-time evolution of this complex system. The aim of this proposal calls for not an immediate concrete action, but to initiate the discussion for a longer range project which could lead to definite design of a dedicated exclusive experiment in 5 years from now. It is clear, that exclusive experiments have more information than the inclusive ones, what is not clear, is this information enough for a breakthrough. Pessimists can say: There is no such information. But I ask: Please prove it without trying to measure it! If you are interested in more scientific and technical details. please contact: [email protected]