HIGH ENERGY SEMINARS
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The High Energy Seminars are in Room 2165 NPB on Tuesdays & Fridays @ 2:00pm
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| NOVEMBER 24 (TUE) | ||
| Speaker | Sascha Bornhauser Univ. of New Mexico | |
| Title | Prospects for the Detection of Rapidity Gap Events in Squark Pair Production at the LHC | |
| Abstract | The exchange of electroweak gauginos in the t- or u-channel allows squark pair production at hadron colliders without color exchange between the squarks. This can give rise to events where little or no energy is deposited in the detector between the squark decay products. I will talk about the potential for detection of such rapidity gap events at the Large Hadron Collider (LHC). The numerical analysis is divided into two parts. First, the rapidity gap signal is evaluated in a simplified framework at the parton level. The second part covers an analysis with full event simulation using PYTHIA as well as Herwig++, but without detector simulation. The transverse energy deposited between the jets from squark decay is analyzed, as well as the probability of finding a third jet in between the two hardest jets. For the mSUGRA benchmark point SPS1a we find statistically significant evidence for a color singlet exchange contribution. | |
| DECEMBER 1 (TUE) | ||
| Speaker | Rachel Bean Cornell University | |
| Title | Testing gravity on cosmic scales | |
| Abstract | While the properties of gravity, and its consistency with General Relativity (GR), are well tested on solar system scales, within our system and the decay of binary pulsar orbits, they are, by comparison, poorly tested on cosmic scales. This is of particular interest as we try to understand the origins of cosmic acceleration, and whether they are a signature of deviations from GR. Using the latest measurements of the universe's expansion history, twinned with the evolution of large scale structure, we discuss the current constraints on gravity's behavior on the largest scales observable today. | |
| DECEMBER 8 (TUE) | ||
| Speaker | Bo-Sture Skagerstam Norwegian U. Sci. Tech. | |
| Title | Photon Emission Near Superconducting Bodies and Atom Chips | |
| Abstract |
As was already pointed out by E.M. Purcell in 1948, the rate of spontaneous emission of atoms will be modified due to the presence of a dielectric body. Spontaneous emission can be thought of as a physical process, where the emission of a photon is stimulated by vacuum fluctuations. The presence of a medium will change the properties of the vacuum and, hence, also the rate for decay processes. This so called Purcell effect has been one of several central topics in the field of modern experimental cavity quantum electrodynamics. In current investigations and engineering of nano-scale atom microtraps, this issue is also of fundamental importance since such spontaneous emission processes, due to hyperfine spin-flip transitions, have a direct bearing on the stability of atom chips. In the present talk, we give a brief introduction to some of these issues in terms of photon emission due to a magnetic spin-flip transition of a two-level atom in the vicinity of a dielectric body like a normal conducting metal or a superconductor. In the analysis of this physical system one has to address issues like the notion of a photon propagating close to or in a dissipative medium. A simpler but analogues problem is how to quantize a damped harmonic oscillator. For temperatures below the critical temperature of a superconductor, the corresponding spin-flip lifetime can be boosted by almost twenty orders of magnitude as compared to the case of a normal conducting body! This recent finding of ours has opened up the window for the design of new superconductor based atom chips. We also report on some recent work on the related attractive (!) Casimir-Polder force. |
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| DECEMBER 11 (FRI) | ||
| Speaker | Tomislav Prokopec Univ. of Utrecht | |
| Title | The Hubble Effective Potential | |
| Abstract | ||