Colloquia

Fifty years ago, two astronomers, R. Hanbury Brown and R. Q. Twiss, invented a new method to measure the angular diameter of stars, in spite of the atmospheric fluctuations. Their proposal prompted a hot debate among physicists : how might two particles (photons), emitted independently (at opposite extremities of a star) , behave in a correlated way when detected ? It was only after the development of R Glauber's full quantum analysis that the effect was understood as a two particle quantum interference effect. From a modern perspective, it can be viewed as an early example of the amazing properties of pairs of entangled particles. The effect has now been observed with bosonic and fermionic atoms, stressing its fully quantum character. After putting these experiments in a historical perspective, I will present recent results, and comment on their significance. I will also show how our single atom detection scheme has allowed us to demonstrate the creation of atom pairs by non linear mixing of matter waves. This result paves the way to experiments aiming at probing entanglement in atom pairs..

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A missing energy discovery is possible at the LHC in the first year of running. The origin of such a signal could be any of a huge number of models of supersymmetry, or non-supersymmetric models with extra dimensions or "little Higgs". Recently we have developed a realistic strategy to rapidly narrow the list of candidate theories at, or close to, the moment of discovery. The strategy is based on robust ratios of inclusive counts of simple physics objects. We studied specific cases showing discrimination of look- alike models in simulated data sets that are at least 10 to 100 times smaller than used in previous studies. We discriminate supersymmetry models from non-supersymmetric look-alikes with only 100 pb-1 of simulated data, using combinations of observables that trace back to differences in spin..

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Modern "big science" projects, such as the LHC experiments in physics that are being prepared to run at CERN, embody the distinctive ethos of cooperation and mechanisms of coordination among distributed groups of researchers that are characteristic of 'open science'. Much has been written about the institutions of open science, their supporting social norms, and their effectiveness in generating additions to the stock of reliable knowledge. But from where have these institutions and their supporting ethos come? How robust can we assume them to be in the face of the recent trends for universities and research institutes in some domains of science to seek to appropriate the benefits of new discoveries and inventions by asserting intellectual property claims? A search for the historical origins of the institutions of open science throws some new light on these issues, and the answers may offer some lessons for contemporary science and technology policy-making..

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The human side of doing theoretical physics is explored through stories about the interactions between physicists and about the effects world events can have on scientists' behavior, and even on their interests and style. These stories cluster nicely around certain bigger themes to create an overarching whole. This happens both on account of some interesting narrative structures intrinsic to the science of physics itself and on account of the way physics integrates into the general culture. The stories concern Einstein, Schrödinger, Pauli, Heisenberg, Stueckelberg, Jordan and Fock and also involve some mathematicians like Emmy Noether, Teichmüller and Bers and even the psychologist C.G. Jung..

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A brief overview of the basic elements of the US space and science policy-making apparatus will be presented, focussing on insights into the interactions among the principal organizations, policy-making bodies and individual participants and their respective impact on policy outcomes. Several specific examples will be provided to illustrate the points made, and in the conclusion there will be some observations on current events in the US that may shape the outcome for the near-term future of US space and science policy in several areas..

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Concerns have been expressed from time to time about the safety of new high-energy colliders, and the LHC has been no exception. The LHC Safety Assessment Group (LSAG)(*) was asked last year by the CERN management to review previous LHC safety analyses in light of additional experimental results and theoretical understanding. LSAG confirms, updates and extends previous conclusions that there is no basis for any conceivable threat from the LHC. Indeed, recent theoretical and experimental developments reinforce this conclusion. In this Colloquium, the basic arguments presented by LSAG will be reviewed. Cosmic rays of much higher effective centre-of-mass energies have been bombarding the Earth and other astronomical objects for billions of years, and their continued existence shows that the Earth faces no dangers from exotic objects such as hypothetical microscopic black holes that might be produced by the LHC - as discussed in a detailed paper by Giddings and Mangano(**). Measurements of strange particle production at RHIC constrain severely the possible production of strangelets in heavy-ion collisions at the LHC, which also present no danger - as discussed in an addendum to the LSAG report. On a different note: although the LHC is no danger to the Earth, it may reveal the fate of the Universe by probing the nature of the vacuum(***). (*) J.E., Gian Gudice, Michelangelo Mangano, Igor Tkachev and Urs Wiedemann: arXiv:0806.3414 (**) Steven Giddings and Michelangelo Mangano: arXiv:0806.3381 (***) S. Abel. J.E., J. Jaeckel and V.V. Khoze: arXiv:0807.2601.

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CERN COLLOQUIUM AND 2008 EPS-CPS LECTURE =================================== The Beijing Electron Positron Collider (BEPC) finished its running July 2005, with great success in both the Tau-Charm physics experiment and the synchrotron radiation light source. The latest Charm physics results from BEPC are reviewed, including the observation of the new resonance of X1835 with a possible explanation of the PPbar bound state. The major upgrade of BEPC into a double ring collider, so called BEPCII, will increase its luminosity by two orders of magnitude. The physics window of BEPCII is mainly the precision measurements in the Charm physics and the search for new phenomena. The construction of BEPCII is finished. The tuning of the storage ring goes smoothly. The synchrotron radiation facility of BEPCII opened to users with high performance since the end of 2006. The new detector BESIII has been moved into the interaction region June, and the joint commissioning started. The non-accelerator experiments in China are promoted with great efforts, including the neutrino physics experiments, the cosmic ray measurements, and the particle astrophysics experiments in Space. The reactor neutrino experiment at Daya Bay could reach the sensitivity of 0.01 on the measurement of the neutrino mixing parameter sin2² θ13. The medium and long term plan of the Chinese particle physics experiments is also discussed..

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The field of solar energy research has reached a level of maturity where truly commercial applications can be envisaged. The fascinating story of one of the first prototypes will be presented. PLEASE NOTE UNUSUAL TIME: The Colloquium will begin at 16:00.

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The talk will be based on his Nobel lecture in 2007..

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In the Standard Model of Particle Physics we are dealing with 28 fundamental constants. In the experiments these constants can be measured, but theoretically they are not understood. I will discuss these constants, which are mostly mass parameters. Astrophysical measurements indicate that the finestructure constant is not a real constant, but depends on time. Grand unification then implies also a time variation of the QCD scale. Thus the masses of the atomic nuclei and the magnetic moments of the nuclei will depend on time. I proposed an experiment, which is currently done by Prof. Haensch in Munich and his group. The first results indicate a time dependence of the QCD scale. I will discuss the theoretical implications..

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Abstract: Technology has had a profound impact on people's lives around the world by tackling challenges in education, health care, research, and economic development. Throughout its history, Intel has been inspired by what technology makes possible. The work taking place at CERN has been a prime motivation to continue enhancing energy-efficient computing power required in the search for the Higgs boson. Can Intel keep pace with computing needs to tackle the world's biggest challenges? Craig Barrett, Chairman of Intel and the United Nations Global Alliance for Information and Communication Technologies and Development, will discuss research currently underway that will help us rise to the challenge, as well as how technology is changing people's lives all over the world. Biography: Craig Barrett became Intel's fourth president in May 1997, chief executive officer in 1998 and chairman of the Board on May 18, 2005. Dr. Barrett also serves as Chairman of the United Nations Global Alliance for Information and Communication Technologies and Development, and is an appointee to the President's Advisory Committee for Trade Policy and Negotiations and to the American Health Information Community. Dr. Barrett joined Intel Corporation in 1974 as a technology development manager. He was named a vice president of the corporation in 1984, promoted to senior vice president in 1987, and executive vice president in 1990. Dr. Barrett was elected to Intel Corporation's Board of Directors in 1992 and was named the company's chief operating officer in 1993. He Dr. Barrett was born Aug. 29, 1939 in San Francisco, California. He attended Stanford University in Palo Alto, California from 1957 to 1964, and received his Bachelor of Science, Master of Science and Ph.D. degrees in Materials Science. After graduation, he joined the faculty of Stanford University in the Department of Materials Science and Engineering, and remained through 1974, rising to the rank of Associate Professor. Dr. Barrett is the author of over 40 technical papers dealing with the influence of microstructure on the properties of materials, and a textbook on materials science, Principles of Engineering Materials..

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In the last fifteen years the irradiation of solid tumours with beams of charged hadrons has seen a spectacular development with more than 55,000 patients treated worldwide with proton beams and about 5,000 patients with carbon ion beams. The first part of the seminar discusses (i) the reasons for using both protons and carbon ions in cancer therapy, (ii) the accelerators used and (iii) to the present status and the future needs of hadron-therapy centres. In the second part the technologies of dose delivery are described emphasising the main challenges of modern radiotherapy, in particular the treatment of moving organs. In this framework the properties of the beams produced by conventional accelerators (cyclotrons and synchrotrons) are compared with the ones due to two novel approaches based on fast cycling machines, as FFAGs and cyclinacs..

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