Homepage of Yevgeny Kats

and welcome! I do research in theoretical high-energy physics. I am interested in a broad range of topics, and especially the phenomenology of particle physics beyond the Standard Model. At present my main focus is studies relevant to collider physics (because the LHC is running and collecting more and more data!). I am currently a postdoc in the New High Energy Theory Center at Rutgers University. Previously, I was a graduate student at the Center for the Fundamental Laws of Nature, in the Department of Physics at Harvard University, where I received my Ph.D. in May 2010. You may also find me on Facebook. Reach me by email at any time: Recent research topics Characterizing new colored particles using their QCD bound states In any extension of the Standard Model with pair-produced colored particles, they would sometimes form a QCD bound state with each other when produced close to threshold. As long as they have no unsuppressed 2-body decays, the bound particles will typically annihilate into a pair of Standard Model particles rather than decay in their usual way. Such processes give rise to resonances in the invariant mass distributions of the annihilation products, which often include easily measurable objects such as isolated photons or leptons (even when the usual decays of these particles do not contain such objects). These signals can provide detailed information about the properties of the new particles. This approach is very general and to a large extent model-independent: it retains its full power regardless of how obscure the usual decay signatures of the particles might be. In the most recent work, we have shown how the mass, spin, electric charge, color representation and additional properties of the new particles can be determined unambiguously by combining information from the dijet, photon+jet, diphoton and dilepton channels of the bound states annihilation. We have also derived limits on new colored particles based on the non-observation of such signals so far at the 7 TeV LHC.     Probing Colored Particles with Photons, Leptons, and Jets     Yevgeny Kats and Matthew J. Strassler     arXiv:1204.1119 [hep-ph] In an earlier work, we compared the bound state signals coming from the superpartners in the MSSM with those from the level-1 KK modes in a theory of universal extra dimensions (UED). We have shown how, when these signals are observable, they can be used for distinguishing between the two scenarios.     Distinguishing spins at the LHC using bound state signals     Dilani Kahawala and Yevgeny Kats     arXiv:1103.3503 [hep-ph] [JHEP 09 (2011) 099] Implications of results from colliders on theoretical models Measurements and new physics searches from the Tevatron and the LHC can be re-used for studying the viability of various other hypothetical new physics scenarios. This can be done reliably by a careful simulation of all the crucial ingredients of the physical process, the detector response and the analysis done in the original experimental studies. In a recent work we have surveyed multiple representative slices of the parameter space of supersymmetry, broken via gauge mediation. Using the (almost) complete set of analyses based on 1/fb of LHC data we derived limits on the superpartner masses in the various scenarios. In several cases we suggested ways in which the reach of the LHC searches could be improved. Among our most interesting results are constraints, or the possibility to constrain, scenarios with direct production of sbottoms or stops, or electroweak production.     The status of GMSB after 1/fb at the LHC     Yevgeny Kats, Patrick Meade, Matthew Reece, and David Shih     arXiv:1110.6444 [hep-ph] [JHEP 02 (2012) 115] In a previous work, we have studied the possibility for the stop to be very light, even lighter than the top, in the scenario where it is the NLSP that decays to a W, b and gravitino. Based on Tevatron and LHC top-quark cross section measurements in various channels and searches in top-like samples, we have found that the stop could still be as light as 150 GeV.     Light stop NLSPs at the Tevatron and LHC     Yevgeny Kats and David Shih     arXiv:1106.0030 [hep-ph] [JHEP 08 (2011) 049] Unparticle physics The term "unparticle physics" refers to an extension of the Standard Model that contains a hidden sector that is conformally invariant (or one that effectively becomes conformal at an infrared fixed point). If the anomalous dimensions are far from an integer, the excitations of the conformal sector produced in collisions of Standard Model particles cannot be described in terms of particles. In our work, we studied how to describe and compute processes generated by the self-interactions of the unparticle sector, whose physics is encoded in higher correlation functions of the CFT. We argued that the production of "unparticle stuff" in Standard Model-initiated processes involving unparticle self-interactions can be decomposed using the conformal partial wave expansion into a sum over contributions from the production of various kinds of unparticle stuff, corresponding to the various primary conformal operators in the CFT, often different from those to which the standard model couples directly. We discussed inclusive and exclusive techniques for computing these processes. We have exemplified our methods by computing the effects of self-interactions in the 2D Thirring model which is exactly solvable.     Unparticle self-interactions     Howard Georgi and Yevgeny Kats     arXiv:0904.1962 [hep-ph] [JHEP 02 (2010) 065] In another context, we have analyzed a more general but still exactly solvable 2D model, the Sommerfield model, that is a theory of a massless fermion coupled to a massive vector boson which flows to the Thirring model at low energies. There we could see in detail how the production of the unparticle stuff from ordinary particles proceeds between the high-energy particle-like behavior of the unparticle sector and the low-energy unparticle behavior. It is well-known that in ordinary QCD, the short-distance perturbative physics of quarks and gluons turns into the physics of hadrons at large distances. We found that analogously to QCD there is a massive "hadron" in the spectrum of the Sommerfield model, but in sharp contrast with QCD there is also the unparticle stuff.     Unparticle Example in 2D     Howard Georgi and Yevgeny Kats     arXiv:0805.3953 [hep-ph] [Phys. Rev. Lett. 101 (2008) 131603] Shear viscosity in strongly-coupled theories via AdS/CFT Strongly-coupled large-N CFTs are accessible via the AdS/CFT correspondence. We studied how the shear viscosity of such a theory (at finite temperature) is affected by R-squared corrections to the AdS action. We presented an example of a 4D theory in which the conjectured lower bound on the viscosity-to-entropy ratio, 1/4π, is violated by 1/N corrections. The existence of such examples may be relevant to the QCD quark-gluon plasma whose η/s is close to 1/4π.     Effect of curvature squared corrections in AdS on the viscosity of the dual gauge theory     Yevgeny Kats and Pavel Petrov     arXiv:0712.0743 [hep-th] [JHEP 01 (2009) 044] Education 2010 Ph.D. in Physics, High Energy Theory Group, Harvard University Advisors: Nima Arkani-Hamed and Howard Georgi Thesis: "Physics of Conformal Field Theories" 2004 M.Sc. in Physics (Summa Cum Laude), Bar-Ilan University, Israel Pursued in parallel with military service. Advisor: Lior Klein Thesis: "Extraordinary Hall Effect in SrRuO3" 2001 B.Sc. in Physics and Computer Science (Summa Cum Laude), Bar-Ilan University, Israel 1998 Handesaim High School (affiliated to Tel Aviv University at the time) and HEMDA Publications High energy theory (2006 - present)   [INSPIRE]     Probing Colored Particles with Photons, Leptons, and Jets     Yevgeny Kats and Matthew J. Strassler     arXiv:1204.1119 [hep-ph]     The status of GMSB after 1/fb at the LHC     Yevgeny Kats, Patrick Meade, Matthew Reece, and David Shih     arXiv:1110.6444 [hep-ph] [JHEP 02 (2012) 115]     Light stop NLSPs at the Tevatron and LHC     Yevgeny Kats and David Shih     arXiv:1106.0030 [hep-ph] [JHEP 08 (2011) 049]     Distinguishing spins at the LHC using bound state signals     Dilani Kahawala and Yevgeny Kats     arXiv:1103.3503 [hep-ph] [JHEP 09 (2011) 099]     Annihilation decays of bound states at the LHC     Yevgeny Kats and Matthew D. Schwartz     arXiv:0912.0526 [hep-ph] [JHEP 04 (2010) 016]     Unparticle self-interactions     Howard Georgi and Yevgeny Kats     arXiv:0904.1962 [hep-ph] [JHEP 02 (2010) 065]     Unparticle Example in 2D     Howard Georgi and Yevgeny Kats     arXiv:0805.3953 [hep-ph] [Phys. Rev. Lett. 101 (2008) 131603]     Effect of curvature squared corrections in AdS on the viscosity of the dual gauge theory     Yevgeny Kats and Pavel Petrov     arXiv:0712.0743 [hep-th] [JHEP 01 (2009) 044]     Higher-order corrections to mass-charge relation of extremal black holes     Yevgeny Kats, Lubos Motl, and Megha Padi     arXiv:hep-th/0606100 [JHEP 12 (2007) 068] Condensed matter theory (2001)     Frenet algorithm for simulations of fluctuating continuous elastic filaments     Yevgeny Kats, David A. Kessler, and Yitzhak Rabin     Phys. Rev. E 65 (2002) 020801(R) [arXiv:cond-mat/0108038] Condensed matter experiment (1999-2004)     M. Sc. Thesis: Extraordinary Hall effect in SrRuO3     Department of Physics, Bar-Ilan University (2004). Advisor: Lior Klein.     Large anisotropy in the paramagnetic susceptibility of SrRuO3 films     Y. Kats, I. Genish, L. Klein, J. W. Reiner, and M. R. Beasley     Phys. Rev. B 71, 100403(R) (2005) [arXiv:cond-mat/0311341]     Testing the Berry phase model for extraordinary Hall effect in SrRuO3     Y. Kats, I. Genish, L. Klein, J. W. Reiner, and M. R. Beasley     Phys. Rev. B 70, 180407(R) (2004) [arXiv:cond-mat/0405645]     Paramagnetic anisotropic magnetoresistance in thin films of SrRuO3     I. Genish, Y. Kats, L. Klein, J. W. Reiner, and M. R. Beasley     in Proceedings of 9th Joint MMM-Intermag Conference, J. Appl. Phys. 95, 6681 (2004)     [arXiv:cond-mat/0311343]     Local measurements of magnetization reversal in thin films of SrRuO3     I. Genish, Y. Kats, L. Klein, J. W. Reiner, and M. R. Beasley     in Proceedings of SCM2004, Phys. Stat. Sol. (c) 1, 3440 (2004)     Magnetoresistance scaling in BaRuO3     S. Levy, Y. Kats, M. K. Lee, C. B. Eom, and L. Klein     in Proceedings of SCES2001, Physica B 312-313, 795 (2002)     Can fractional power-law conductivity explain the deviations from Matthiessen's rule in SrRuO3?     Y. Kats and L. Klein     in Proceedings of SCES2001, Physica B 312-313, 793 (2002)     Negative deviations from Matthiessen's rule in SrRuO3 and CaRuO3     L. Klein, Y. Kats, N. Wiser, M. Konczykowski, J. W. Reiner, T. H. Geballe, M. R. Beasley, and A. Kapitulnik     Europhys. Lett. 55, 532 (2001) [arXiv:cond-mat/0011376]     Magnetic resistivity in SrRuO3 and the ferromagnetic phase transition     Y. Kats, L. Klein, J. W. Reiner, T. H. Geballe, M. R. Beasley, and A. Kapitulnik     Phys. Rev. B 63, 054435 (2001)     Domain wall resistivity in SrRuO3: the influence of domain walls spacing     L. Klein, Y. Kats, A. F. Marshall, J. W. Reiner, T. H. Geballe, M. R. Beasley, and A. Kapitulnik     in Proceedings of ICM2000, J. Magn. Magn. Mater. 226, 780 (2001)     Domain wall resistivity in SrRuO3     L. Klein, Y. Kats, A. F. Marshall, J. W. Reiner, T. H. Geballe, M. R. Beasley, and A. Kapitulnik     Phys. Rev. Lett. 84, 6090 (2000) [arXiv:cond-mat/9912404] Teaching experience I have served as a Teaching Fellow in the following courses at Harvard: Physics 15b Introductory Electromagnetism Spring 2006 | Lecturers: Nima Arkani-Hamed and Markus Greiner Spring 2010 | Lecturer: Masahiro Morii awarded Certificate of Distinction in Teaching in Spring 2006 Physics 16 Mechanics and Special Relativity Fall 2005 and Fall 2007 | Lecturer: Howard Georgi awarded Certificate of Distinction in Teaching in Fall 2007 Physics 151 Mechanics Fall 2006 | Lecturer: Arthur Jaffe awarded Certificate of Distinction in Teaching Physics 253c   Quantum Field Theory III Spring 2008 | Lecturer: Howard Georgi And at Harvard Summer School: Physics 1a       Principles of Physics Summer 2005 and Summer 2006 | Lecturer: John Wills Other All the links to the IPhO — a website about physics olympiads. If you're a past IPhO participant, you're welcome to add your page to my collection.