3 $^{38}$Queen Mary, University of London, London, E1 4NS, United Kingdom $^{39}$University of London, Royal Holloway and Bedford New College, Egham, Surrey TW20 0EX, United Kingdom $^{40}$University of Louisville, Louisville, Kentucky 40292, USA $^{41}$Johannes Gutenberg-Universit¨ at Mainz, Institut f¨ ur Kernphysik, D-55099 Mainz, Germany $^{42}$University of Manchester, Manchester M13 9PL, United Kingdom $^{43}$University of Maryland, College Park, Maryland 20742, USA $^{44}$University of Massachusetts, Amherst, Massachusetts 01003, USA $^{45}$Massachusetts Institute of Technology, Laboratory for Nuclear Science, Cambridge, Massachusetts 02139, USA $^{46}$McGill University, Montr´ eal, Qu´ ebec, Canada H3A 2T8 $^{47}$INFN Sezione di Milano $^{a}$; Dipartimento di Fisica, Universit` a di Milano $^{b}$, I-20133 Milano, Italy $^{48}$University of Mississippi, University, Mississippi 38677, USA $^{49}$Universit´ e de Montr´ eal, Physique des Particules, Montr´ eal, Qu´ ebec, Canada H3C 3J7 $^{50}$INFN Sezione di Napoli $^{a}$; Dipartimento di Scienze Fisiche, Universit` a di Napoli Federico II $^{b}$, I-80126 Napoli, Italy $^{51}$NIKHEF, National Institute for Nuclear Physics and High Energy Physics, NL-1009 DB Amsterdam, The Netherlands $^{52}$University of Notre Dame, Notre Dame, Indiana 46556, USA $^{53}$Ohio State University, Columbus, Ohio 43210, USA $^{54}$University of Oregon, Eugene, Oregon 97403, USA $^{55}$INFN Sezione di Padova $^{a}$; Dipartimento di Fisica, Universit` a di Padova $^{b}$, I-35131 Padova, Italy $^{56}$Laboratoire de Physique Nucl´ eaire et de Hautes Energies, IN2P3/CNRS, Universit´ e Pierre et Marie Curie-Paris6, Universit´ e Denis Diderot-Paris7, F-75252 Paris, France $^{57}$INFN Sezione di Perugia $^{a}$; Dipartimento di Fisica, Universit` a di Perugia $^{b}$, I-06100 Perugia, Italy $^{58}$INFN Sezione di Pisa $^{a}$; Dipartimento di Fisica, Universit` a di Pisa $^{b}$; Scuola Normale Superiore di Pisa$^{c}$, I-56127 Pisa, Italy $^{59}$Princeton University, Princeton, New Jersey 08544, USA $^{60}$INFN Sezione di Roma $^{a}$; Dipartimento di Fisica, Universit` a di Roma La Sapienza $^{b}$, I-00185 Roma, Italy $^{61}$Universit¨ at Rostock, D-18051 Rostock, Germany $^{62}$Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, United Kingdom $^{63}$CEA, Irfu, SPP, Centre de Saclay, F-91191 Gif-sur-Yvette, France $^{64}$SLAC National Accelerator Laboratory, Stanford, California 94309 USA $^{65}$University of South Carolina, Columbia, South Carolina 29208, USA $^{66}$Stanford University, Stanford, California 94305-4060, USA $^{67}$State University of New York, Albany, New York 12222, USA $^{68}$Tel Aviv University, School of Physics and Astronomy, Tel Aviv, 69978, Israel $^{69}$University of Tennessee, Knoxville, Tennessee 37996, USA $^{70}$University of Texas at Austin, Austin, Texas 78712, USA $^{71}$University of Texas at Dallas, Richardson, Texas 75083, USA $^{72}$INFN Sezione di Torino $^{a}$; Dipartimento di Fisica Sperimentale, Universit` a di Torino $^{b}$, I-10125 Torino, Italy $^{73}$INFN Sezione di Trieste $^{a}$; Dipartimento di Fisica, Universit` a di Trieste $^{b}$, I-34127 Trieste, Italy $^{74}$IFIC, Universitat de Valencia-CSIC, E-46071 Valencia, Spain $^{75}$University of Victoria, Victoria, British Columbia, Canada V8W 3P6 $^{76}$Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom $^{77}$University of Wisconsin, Madison, Wisconsin 53706, USA Charged lepton flavor violating processes are unobservable in the standard model, but they are predicted to be enhanced in several extensions to the standard model, including supersymmetry and models with leptoquarks or compositeness. We present a search for such processes in a sample of 99 × 10 6 Υ (2 S ) decays and 117 × 10 6 Υ (3 S ) decays collected with the B A B AR detector. We place upper limits on the branching fractions B ( Υ ( nS ) → e $^{±}$τ $^{∓}$) and B ( Υ ( nS ) → µ $^{±}$τ $^{∓}$) ( n = 2 , 3) at the 10 − 6 level and use these results to place lower limits of order 1 TeV on the mass scale of charged lepton flavor violating effective operators. PACS numbers: 11.30.Hv, 13.20.Gd, 14.40.Nd In the original formulation of the standard model (SM) in which neutrinos are massless, lepton flavor is an ac- cidentally conserved quantum number. The extension of the SM to include neutrino masses introduces os- cillations between the neutrino flavors, which violate this conservation law. However, SM processes involv- ing charged lepton flavor violation (CLFV) remain un- observable because they are suppressed by the quantity (Δ m 2 $_{ν}$/M 2 $_{W}$) 2 < ∼ 10 − 48 [1–3]. Here Δ m 2 ν is the difference between the squared masses of neutrinos of different fla- vor and M$_{W}$ is the charged weak vector boson mass. Hence CLFV represents an unambiguous signature of