Why does a steel (iron alloy) ship float on water, when the density of iron (7.86 g/cm^3) is greater than the density of water?

Professor Aida El-Khadra received her PhD. in 1989 from the University of California, Los Angeles, after receiving her diplom from Freie Universitaet, Berlin, Germany. She held postdoctoral research appointments at Brookhaven National Laboratory, Fermi National Accelerator Laboratory, and the Ohio State Univerity before joining the Illinois faculty in 1995. El-Khadra is a fellow of the American Physical Society, a recipient of the Department of Energy's Outstanding Junior Investigator Award, and a Sloan foundation fellow. In addition, she has a received a number of other research and teaching awards.

Prof. El-Khadra's area of research is theoretical particle physics. Her research focuses on the application of lattice Quantum Chromodynamics (also called the strong interactions) to phenomenologically interesting processes in flavor physics, which are relevant to the experimental effort at the so-called intensity frontier. She is a leader of one of the most successful collaborations working in Lattice Field Theory in the world, the Fermilab Lattice collaboration. Select highlights include the first quantitative determination of the the strong coupling from lattice QCD, a new formulation of heavy quarks on the lattice that is the foundation of many important, phenomenologically relevant lattice calculations, for example, **predictions** of the *D* and *D _{s}* meson decay constants, predictions of the shape of the semileptonic

**Elementary Particle Theory**

The high-energy theory group has a wide variety of research interests. Topics include the top quark, electroweak symmetry breaking, quantum chromodynamics and lattice field theory, standard-model phenomenology, dynamical supersymmetry breaking, duality in supersymmetric field theory and string theory, M theory, and grand unification.

**Standard Model Phenomenology with Lattice QCD**

Quantum chromodynamics (QCD), the theory of the strong interactions, is amenable to perturbative calculations only at high energies. A quantitative understanding of the low-energy behavior of QCD, like the interactions of quarks inside hadrons, requires nonperturbative methods. Lattice field theory offers a systematic approach to solving QCD nonperturbatively. The space-time continuum is replaced by a discrete lattice. Part of our research is concerned with improvements in the formulation of lattice QCD. Other projects deal with applications of lattice QCD to phenomenologically interesting processes that yield insight into the standard model of particle physics.

- Collins Award for Innovative Teaching, COE
- Fellow, American Physical Society
- Center for Advanced Study Accociate
- Frontier Fellow, Fermilab
- Beckman Fellow in the Center for Advanced Study
- Xerox for Faculty Research Award
- A. P. Sloan Foundation Fellow
- DOE Outstanding Junior Investigator Award

- A. Bazavov, et al. Kaon semileptonic vector form factor and determination of |V_{us}| using staggered fermions. Phys. Rev. D 87, 073012. (2013)
- Jon A. Bailey, et al. Refining new-physics searches in B->D tau nu decay with lattice QCD. Phys. Rev. Lett. 109, 071802 (2012).
- A. Bazavov, et al. Neutral B-meson mixing from three-flavor lattice QCD: Determination of the SU(3)-breaking ratio xi. Phys. Rev. D86 034503 (2012).
- Jon A. Bailey, et al. Bs -> Ds/B->D Semileptonic Form-Factor Ratios and Their Application to BR(B0s -> mu+ mu-). Phys. Rev. D85, 114502 (2012).
- A. Bazavov, et al. B- and D-meson decay constants from three-flavor lattice QCD. Phys. Rev. D85, 114506 (2012).
- C. Bernard, et al. Tuning Fermilab Heavy Quarks in 2+1 Flavor Lattice QCD with Application to Hyperfine Splittings. Phys. Rev. D83, 034503 (2011).
- T. Burch, et al. Quarkonium mass splittings in three-flavor lattice QCD. Phys. Rev. D 81, 034508 (2010).
- C. Bernard et al. Visualization of semileptonic form factors from lattice QCD. Phys. Rev. D 80, 034026 (2009).
- J. Bailey, et al.Â The B -> pi l nu semileptonic form factor from three-flavor lattice QCD: A model-independent determination of |V(ub)|. Phys. Rev. D 79, 054507 (2009).
- C. Bernard, et al. The Anti-B ---> D* l anti-nu form factor at zero recoil from three-flavor lattice QCD: A Model independent determination of |V(cb)|. Phys. Rev. D
**79**, 014506 (2009). - A. S. Kronfeld, et al. Predictions fromÂ Lattice QCD. Talk given at International Conference on QCD and Hadronic Physics, Beijing, China, 16-20 June 2005; 23rd International Symposium on Lattice Field Field: Lattice 2005, Trinity College, Dublin, Ireland, 25-30 July 2005. Int. J. Mod. Phys. A 21, 713-719 (2006).
- C. Aubin, et al. Charmed-meson decay constants in three-flavor lattice QCD. Phys. Rev. Lett.
**95**, 122002-1-5 (2005). - C. Aubin, et al. Semileptonic decays of
*D*mesons in three-flavor lattice QCD. Phys. Rev. Lett.**94**, 011601-1-5 (2005). - C. T. H. Davies, et al. High-precision lattice QCD confronts experiment. Phys. Rev. Lett.
**92**, 022001-1-5 (2004). - A. X. El-Khadra, A. S. Kronfeld, P. B. Mackenzie, S. M. Ryan, and J. N. Simone. Semileptonic decays B-> pi l nu and D-> pi l nu from lattice QCD . Phys. Rev. D
**64**, 014502-1-18 (2001). - S. Hashimoto, A. X. El-Khadra, A. S. Kronfeld, P. B. Mackenzie, S. M. Ryan, and J. N. Simone. Lattice QCD calculation of
*B*-->*D*lepton anti-neutrino decay form-factors at zero recoil. Phys. Rev. D**61**, 014502 (1999). - B.P.G. Mertens, A.S. Kronfeld, and A.X. El-Khadra. The self energy of massive lattice fermions. Phys. Rev. D
**58**, 034505 (1998). - A.X. El-Khadra, A.S. Kronfeld, P.B. Mackenzie, S.M. Ryan, and J.N. strong>58, 014506-1-10 (1998).
- B. Gough , et al. The light quark masses from lattice gauge theory. Phys. Rev. Lett.
**79**, 1622 (1997). - A. X. El-Khadra, A. Kronfeld, and P. Mackenzie. Massive quarks in lattice QCD. Phys. Rev. D 3933-3957 (1997).
- A.X. El-Khadra, C. Bernard, and A. Soni. Lattice calculation of the semi-leptonic form factor at the endpoint for
*D*-->*K*^{*}. Phys. Rev. D**47**, 998 (1993). - A.X. El-Khadra, G. Hockney, A. Kronfeld, and P. Mackenzie. A determination of the strong coupling constant from the Charmonium spectrum. Phys. Rev. Lett.
*69*, 729 (1992). - A.X. El-Khadra, C. Bernard, and A. Soni. Lattice study of semi-leptonic decays of charm mesons into vector mesons. Phys. Rev. D
**45**, 869 (1992). - A. X. El-Khadra, C. Bernard, and A. Soni. Semi-leptonic decays on the lattice: the 0
^{-}to 0^{-}case. Phys. Rev. D**43**, 2140 (1991). - E.D. Freeland, et al. Neutral B mixing from 2+1 flavor lattice QCD. 30th International Symposium on Lattice Field Theory (Lattice 2012). PoS LATTICE2012 (2012) 158 [arXiv:1212.5470].
- A. Bazavov, et al. Two-Point Correlator Fits on HISQ Ensembles. 30th International Symposium on Lattice Field Theory (Lattice 2012). PoS LATTICE2012 (2012) 158 [arXiv:1212.0613].
- Jon A. Bailey, et al. Charm semileptonic decays and |V_{cs(d)}| from heavy clover quarks and 2+1 flavor asqtad staggered ensembles. 30th International Symposium on Lattice Field Theory (Lattice 2012). PoS LATTICE2012 (2012) 272 [arXiv:1211.4964].
- Ran Zhou, et al. Form factors for semi-leptonic B decays. 30th International Symposium on Lattice Field Theory (Lattice 2012). PoS LATTICE2012 (2012) 120 [arXiv:1211.1390].
- E. Gamiz, et al. Kaon semileptonic decay form factors with HISQ valence quarks. 30th International Symposium on Lattice Field Theory (Lattice 2012). PoS LATTICE2012 (2012) 113 [arXiv:1211.0751]
- A. Bazavov, et al. Pseudoscalar meson physics with four dynamical quarks. 30th International Symposium on Lattice Field Theory (Lattice 2012). PoS LATTICE2012 (2012) 159 [arXiv:1210.8431].
- C.M. Bouchard, E.D. Freeland, C. Bernard, A.X. El-Khadra, E. Gamiz, A.S. Kronfeld, J. Laiho, R.S. Van de Water. Neutral B mixing from 2+1 flavor lattice-QCD: the Standard Model and beyond. 29th International Symposium on Lattice Field Theory. PoS LATTICE2011 (2011) 274 [arXiv:1112.5642].
- E. T. Neil, et al. B and D meson decay constants from 2+1 flavor improved staggered simulations. 29th International Symposium on Lattice Field Theory. PoS LATTICE2011 (2011) 320 [arXiv:1112.3978].
- Jon A. Bailey, A. Bazavov, A. X. El-Khadra, Steven Gottlieb, R. D. Jain, A. S. Kronfeld, R. S. Van de Water, R. Zhou. D semileptonic form factors and Ã¢Ë†Â£Vcs(d)Ã¢Ë†Â£ from 2+1 flavor lattice QCD. 29th International Symposium on Lattice Field Theory. PoS LATTICE2011 (2011) 270 [arXiv:1111.5471].
- C. Bernard, C. M. Bouchard, A. X. El-Khadra, E. D. Freeland, E. GÃƒÂ¡miz, A. S. Kronfeld, J. Laiho, R. S. Van de Water. B Mixing in the Standard Model and Beyond: Lattice QCD. Proceedings of the 19th Particles and Nuclei International Conference (PANIC11), Cambridge, MA, U.S.A., July 2011. AIP Conf.Proc. 1441 (2012) 672-674 [arXiv:1111.2968].
- E. Gamiz, C. DeTar, A. X. El-Khadra, A. S. Kronfeld, P. B. Mackenzie, J. Simone. Calculation of K-> pi Form Factors with Nf=2+1 Flavors of Staggered Quarks. 29th International Symposium on Lattice Field Theory. PoS LATTICE2011 (2011) 281 [arXiv:1111.2021].
- Ran Zhou, et al. Form Factors for B to Kll Semileptonic Decay from Three-Flavor Lattice QCD. 29th International Symposium on Lattice Field Theory. PoS LATTICE2011 (2011) 298 [arXiv:1111.0981].
- J. Simone et al. The decay constants f(D/s), f(D+), f(B/s) and f(B) from lattice QCD. 28th International Symposium On Lattice Field Theory. PoS LATTICE2010, 317 (2010).
- C. Bouchard, A.X. El-Khadra, E.D. Freeland, E. Gamiz, A.S. Kronfeld. B^0_s and B^0 Mixing in the Standard Model and Beyond: A Progress Report. 28th International Symposium On Lattice Field Theory. PoS LATTICE2010, 299 (2010).
- J.A. Bailey et al. Semileptonic decays of K and D mesons in 2+1 flavor QCD. 28th International Symposium On Lattice Field Theory. PoS LATTICE2010, 306 (2010).
- J.A. Bailey et al. B -> D* l nu at zero recoil: an update. 28th International Symposium On Lattice Field Theory. PoS LATTICE2010, 311 (2010).
- A. Bazavov et al. The Ds and D+ Leptonic Decay Constants from Lattice QCD. XXVIIth Intl. Symposium on Lattice Field Theory. PoS LAT2009, 249 (2009).
- J. A. Bailey et al. Progress on charm semileptonic form factors from 2+1 flavor lattice QCD. XXVIIth Intl. Symposium on Lattice Field Theory. PoS LAT2009, 250 (2009).
- R. T. Evans, E. Gamiz, A. El-Khadra and A. Kronfeld. B-Bbar Mixing and Matching with Fermilab Heavy Quarks. XXVIIth Intl. Symposium on Lattice Field Theory. PoS Lat2009, 245 (2009).
- T. Burch et al. Quarkonium mass splittings with Fermilab heavy quarks and 2+1 flavors of improved staggered sea quarks. XXVIIth Intl. Symposium on Lattice Field Theory. PoS Lat2009, 115 (2009).
- C. Bernard et al. B and D Meson Decay Constants. XXVIth Intl. Symposium on Lattice Field Theory. PoS LATTICE2008,
**278**(2008). e-Print: arXiv:0904.1895 - R.T. Evans, E. Gamiz and A.X. El-Khadra, XXVIth Intl. Symposium on Lattice Field Theory. PoS (LATTICE 2008),
**052**(2008). - A.X. El-Khadra. Weak charm decays with lattice QCD. Proc. of
*Intl. Workshop on Charm Physics (Charm 2007)*, Ithaca, New York, 5-8 Aug 2007, ECONF, e-print: arXiv:0711.1616. http://www.slac.stanford.edu/econf/C070805 - C. Bernard, et al. The decay constants fB and fD+ from three-flavor lattice QCD.
*XXVth Intl. Symposium on Lattice Field Theory*, Proc. of Science LATTICE2007, PoS LAT2007,**370**(2007). - R.T. Evans, E. Gamiz, A.X. El-Khadra, M. Di Pierro. A Determination of the
*B*^{0}_{s}and*B*^{0}_{d}mixing parameters in 2+1 lattice QCD,*XXVth Intl. Symposium on Lattice Field Theory*, 30 July - 4 Aug 2007, Regensburg, Germany, Proc. of Science LATTICE2007,**354**(2007). - A.X. El-Khadra, E. Gamiz, A.S. Kronfeld, M.A. Nobes. Perturbative matching of heavy-light currents at one-loop. Proc. of Science LATTICE2007,
**242**(2007). - S. Gottlieb, et al. Update on onium masses with three flavors of dynamical quarks,
*XXIVth Intl. Symp. on Lattice Field Theory*, July 23-28, 2006, Tucson, Arizona. PoS LAT2006,**175**(2006). - C. Bernard, et al. The decay constants
*f*_{B+}and*f*_{D+}from three-flavor lattice QCD, XXIVth Intl. Symp. on Lattice Field Theory, July 23-28, 2006, Tucson, Arizona . PoS LAT2006,**094**(2006). - R. T. Evans, A. El-Khadra, and M. Di Pierro. A study of the
*B*– ¯_{s}*B*mass and width difference in 2+1 flavor lattice QCD,_{s}*XXIVth Intl. Symp. on Lattice Field Theory*, July 23-28, 2006, Tucson, Arizona. PoS LAT2006,**081**(2006). - A. S. Kronfeld, et al. Predictions from Lattice QCD. Talk given at International Conference on QCD and Hadronic Physics, Beijing, China, 16-20 June 2005; 23rd International Symposium on Lattice Field Field: Lattice 2005, Trinity College, Dublin, Ireland, 25-30 July 2005. PoS LAT2005
**206**, Int. J. Mod. Phys. A**21**, 713-719 (2006). - T. Chupp, A. El-Khadra and S. Prell. Fundamental symmetries and CKM summary of the parallel sessions,
*Proc. of the 9th Intersections of Particle and Nuclear Physics Conference: CIPAN2006*(Rio Grande, Puerto Rico, May 2006). AIP Conf. Proc.**870**, 139 (2006). - P. B. Mackenzie, et al.
*B*and*D*meson semileptonic decays in three-flavor lattice QCD.*Proc. of the XXIIIrd intl. Symp. on Lattice Field Theory*, Dublin, Ireland, July 25-30, 2005 Proc. of Science**207**, 1-6 (2005). - S. Gottlieb, et al. Onium masses with three flavors of dynamical quarks.
*Proc. of the XXIIIrd intl. Symp. on Lattice Field Theory*, Dublin, Ireland, July 25-30, 2005 Proc. of Science**203**, 1-6 (2005). - A. S. Kronfeld, et al. Predictions from Lattice QCD.
*Proc. of the Intl. Conf. on QCD and Hadronic Physics*, Beijing, China, June 16-20, 2005. Proc. of Science**206**, 1-6 (2005). - M. Okamoto, et al. Semileptonic
*D*--> π/*K*and*B*--> π/*D*decays in 2+1 flavor lattice QCD.*Proc. of the 22*, Batavia, IL, June 21-26, 2004, eds. G. Bodwin , E. Eichten, D. Holmgren, and A.X. El-Khadra, Nucl. Phys. B (Proc. Suppl.)^{nd}Intl. Symp. on Lattice Field Theory 2004**140**, 461-463 (2005). - J. N. Simone, et al. Leptonic Decay Constants
*f*and_{Ds}*f*in Three Flavor Lattice QCD._{D}*Proc. of the 22*, Batavia, IL, June 21-26, 2004, eds. G. Bodwin, E. Eichten, D. Holmgren, and A.X. El-Khadra, Nucl. Phys. B (Proc. Suppl.)^{nd}Intl. Symp. on Lattice Field Theory 2004**140**, 443-445 ( 2005). - M. di Pierro, A.X. El-Khadra, S. Gottlieb, A.S. Kronfeld, P.B. Mackenzie, M. Okamoto, M.B. Oktay, and J.N. Simone. www.fermiqcd.net.
*21*, Tsukuba, Ibaraki, July 15-19, 2003 Nucl. Phys. B (Proc. Suppl.)^{st}Intl. Symp. on Lattice Field Theory (LATTICE 2003)**129-130**, 832-834 (2004). - M.B. Oktay, A.X. El-Khadra, A.S. Kronfeld, and P.B. Mackenzie. A more improved lattice action for heavy quarks.
*Proc. of the 21*, Tsukuba, Ibaraki, July 15-19, 2003 Nucl. Phys. B (Proc. Suppl.)^{st}Intl. Symp. on Lattice Field Theory (LATTICE 2003)**129-130**, 349-351 (2004). - M. di Pierro, A.X. El-Khadra, S. Gottlieb, A.S. Kronfeld, P.B. Mackenzie, D.P. Menscher, M.B. Oktay, M. Okamoto, and J.N. Simone. Properties of charmonium in lattice QCD with 2+1 flavors of improved staggered sea quarks.
*Proc. of the 21*, Tsukuba, Ibaraki, July 15-19, 2003 Nucl. Phys. B (Proc. Suppl.)^{st}Intl. Symp. on Lattice Field Theory (LATTICE 2003)**129-130**, 340-342 (2004). - M. Okamoto, M. di Pierro, A.X. El-Khadra, S. Gottlieb, A.S. Kronfeld, P.B. Mackenzie, D.P. Menscher, M.B. Oktay, and J.N. Simone. Semileptonic decays of
*D*mesons in unquenched lattice QCD.*Proc. of the 21*, Tsukuba, Ibaraki, July 15-19, 2003 Nucl. Phys. B (Proc. Suppl.)^{st}Intl. Symp. on Lattice Field Theory (LATTICE 2003)**129-130**, 334-336 (2004). - M. di Pierro, A.X. El-Khadra, S. Gottlieb, A.S. Kronfeld, P.B. Mackenzie, D.P. Menscher, M.B. Oktay, M. Okamoto, and J.N. Simone.
*D*spectrum and leptonic decays with Fermilab heavy quarks and improved staggered light quarks._{s}*Proc. of the 21*, Tsukuba, Ibaraki, July 15-19, 2003 Nucl. Phys. B (Proc. Suppl.)^{st}Intl. Symp. on Lattice Field Theory (LATTICE 2003)**129-130**, 328-330 (2004).

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**Email**

axk@illinois.edu

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