Search for Large Extra Dimensions via Single Photon plus Missing Energy Final States at ��� s p � 1:96 TeV V. M. Abazov,36 B. Abbott,75 M. Abolins,65 B. S. Acharya,29 M. Adams,51 T. Adams,49 E. Aguilo,6 S. H. Ahn,31 M. Ahsan,59 G. D. Alexeev,36 G. Alkhazov,40 A. Alton,64,* G. Alverson,63 G. A. Alves,2 M. Anastasoaie,35 L. S. Ancu,35 T. Andeen,53 S. Anderson,45 B. Andrieu,17 M. S. Anzelc,53 M. Aoki,50 Y. Arnoud,14 M. Arov,60 M. Arthaud,18 A. Askew,49 B. Åsman,41 A. C. S. Assis Jesus,3 O. Atramentov,49 C. Avila,8 C. Ay,24 F. Badaud,13 A. Baden,61 L. Bagby,50 B. Baldin,50 D. V. Bandurin,59 P. Banerjee,29 S. Banerjee,29 E. Barberis,63 A.-F. Barfuss,15 P. Bargassa,80 P. Baringer,58 J. Barreto,2 J. F. Bartlett,50 U. Bassler,18 D. Bauer,43 S. Beale,6 A. Bean,58 M. Begalli,3 M. Begel,73 C. Belanger-Champagne,41 L. Bellantoni,50 A. Bellavance,50 J. A. Benitez,65 S. B. Beri,27 G. Bernardi,17 R. Bernhard,23 I. Bertram,42 M. Besançon,18 R. Beuselinck,43 V. A. Bezzubov,39 P. C. Bhat,50 V. Bhatnagar,27 C. Biscarat,20 G. Blazey,52 F. Blekman,43 S. Blessing,49 D. Bloch,19 K. Bloom,67 A. Boehnlein,50 D. Boline,62 T. A. Bolton,59 G. Borissov,42 T. Bose,77 A. Brandt,78 R. Brock,65 G. Brooijmans,70 A. Bross,50 D. Brown,81 N. J. Buchanan,49 D. Buchholz,53 M. Buehler,81 V. Buescher,22 V. Bunichev,38 S. Burdin,42,† S. Burke,45 T. H. Burnett,82 C. P. Buszello,43 J. M. Butler,62 P. Calfayan,25 S. Calvet,16 J. Cammin,71 E. Carrera,49 W. Carvalho,3 B. C. K. Casey,50 H. Castilla-Valdez,33 S. Chakrabarti,18 D. Chakraborty,52 K. Chan,6 K. M. Chan,55 A. Chandra,48 F. Charles,19,** E. Cheu,45 F. Chevallier,14 D. K. Cho,62 S. Choi,32 B. Choudhary,28 L. Christofek,77 T. Christoudias,43 S. Cihangir,50 D. Claes,67 Y. Coadou,6 M. Cooke,80 W. E. Cooper,50 M. Corcoran,80 F. Couderc,18 M.-C. Cousinou,15 S. Crépé-Renaudin,14 D. Cutts,77 M. Ćwiok,30 H. da Motta,2 A. Das,45 G. Davies,43 K. De,78 S. J. de Jong,35 E. De La Cruz-Burelo,64 C. De Oliveira Martins,3 J. D. Degenhardt,64 F. Déliot,18 M. Demarteau,50 R. Demina,71 D. Denisov,50 S. P. Denisov,39 S. Desai,50 H. T. Diehl,50 M. Diesburg,50 A. Dominguez,67 H. Dong,72 L. V. Dudko,38 L. Duflot,16 S. R. Dugad,29 D. Duggan,49 A. Duperrin,15 J. Dyer,65 A. Dyshkant,52 M. Eads,67 D. Edmunds,65 J. Ellison,48 V. D. Elvira,50 Y. Enari,77 S. Eno,61 P. Ermolov,38 H. Evans,54 A. Evdokimov,73 V. N. Evdokimov,39 A. V. Ferapontov,59 T. Ferbel,71 F. Fiedler,24 F. Filthaut,35 W. Fisher,50 H. E. Fisk,50 M. Fortner,52 H. Fox,42 S. Fu,50 S. Fuess,50 T. Gadfort,70 C. F. Galea,35 E. Gallas,50 C. Garcia,71 A. Garcia-Bellido,82 V. Gavrilov,37 P. Gay,13 W. Geist,19 D. Gelé,19 C. E. Gerber,51 Y. Gershtein,49 D. Gillberg,6 G. Ginther,71 N. Gollub,41 B. Gómez,8 A. Goussiou,82 P. D. Grannis,72 H. Greenlee,50 Z. D. Greenwood,60 E. M. Gregores,4 G. Grenier,20 Ph. Gris,13 J.-F. Grivaz,16 A. Grohsjean,25 S. Grünendahl,50 M. W. Grünewald,30 F. Guo,72 J. Guo,72 G. Gutierrez,50 P. Gutierrez,75 A. Haas,70 N. J. Hadley,61 P. Haefner,25 S. Hagopian,49 J. Haley,68 I. Hall,65 R. E. Hall,47 L. Han,7 K. Harder,44 A. Harel,71 R. Harrington,63 J. M. Hauptman,57 R. Hauser,65 J. Hays,43 T. Hebbeker,21 D. Hedin,52 J. G. Hegeman,34 J. M. Heinmiller,51 A. P. Heinson,48 U. Heintz,62 C. Hensel,58 K. Herner,72 G. Hesketh,63 M. D. Hildreth,55 R. Hirosky,81 J. D. Hobbs,72 B. Hoeneisen,12 H. Hoeth,26 M. Hohlfeld,22 S. J. Hong,31 S. Hossain,75 P. Houben,34 Y. Hu,72 Z. Hubacek,10 V. Hynek,9 I. Iashvili,69 R. Illingworth,50 A. S. Ito,50 S. Jabeen,62 M. Jaffré,16 S. Jain,75 K. Jakobs,23 C. Jarvis,61 R. Jesik,43 K. Johns,45 C. Johnson,70 M. Johnson,50 A. Jonckheere,50 P. Jonsson,43 A. Juste,50 E. Kajfasz,15 A. M. Kalinin,36 J. M. Kalk,60 S. Kappler,21 D. Karmanov,38 P. A. Kasper,50 I. Katsanos,70 D. Kau,49 V. Kaushik,78 R. Kehoe,79 S. Kermiche,15 N. Khalatyan,50 A. Khanov,76 A. Kharchilava,69 Y. M. Kharzheev,36 D. Khatidze,70 T. J. Kim,31 M. H. Kirby,53 M. Kirsch,21 B. Klima,50 J. M. Kohli,27 J.-P. Konrath,23 V. M. Korablev,39 A. V. Kozelov,39 J. Kraus,65 D. Krop,54 T. Kuhl,24 A. Kumar,69 A. Kupco,11 T. Kurča,20 J. Kvita,9 F. Lacroix,13 D. Lam,55 S. Lammers,70 G. Landsberg,77 P. Lebrun,20 W. M. Lee,50 A. Leflat,38 J. Lellouch,17 J. Leveque,45 J. Li,78 L. Li,48 Q. Z. Li,50 S. M. Lietti,5 J. G. R. Lima,52 D. Lincoln,50 J. Linnemann,65 V. V. Lipaev,39 R. Lipton,50 Y. Liu,7 Z. Liu,6 A. Lobodenko,40 M. Lokajicek,11 P. Love,42 H. J. Lubatti,82 R. Luna,3 A. L. Lyon,50 A. K. A. Maciel,2 D. Mackin,80 R. J. Madaras,46 P. Mättig,26 C. Magass,21 A. Magerkurth,64 P. K. Mal,82 H. B. Malbouisson,3 S. Malik,67 V. L. Malyshev,36 H. S. Mao,50 Y. Maravin,59 B. Martin,14 R. McCarthy,72 A. Melnitchouk,66 L. Mendoza,8 P. G. Mercadante,5 M. Merkin,38 K. W. Merritt,50 A. Meyer,21 J. Meyer,22,x T. Millet,20 J. Mitrevski,70 J. Molina,3 R. K. Mommsen,44 N. K. Mondal,29 R. W. Moore,6 T. Moulik,58 G. S. Muanza,20 M. Mulders,50 M. Mulhearn,70 O. Mundal,22 L. Mundim,3 E. Nagy,15 M. Naimuddin,50 M. Narain,77 N. A. Naumann,35 H. A. Neal,64 J. P. Negret,8 P. Neustroev,40 H. Nilsen,23 H. Nogima,3 S. F. Novaes,5 T. Nunnemann,25 V. O’Dell,50 D. C. O’Neil,6 G. Obrant,40 C. Ochando,16 D. Onoprienko,59 N. Oshima,50 N. Osman,43 J. Osta,55 R. Otec,10 G. J. Otero y Garzón,50 M. Owen,44 P. Padley,80 M. Pangilinan,77 N. Parashar,56 S.-J. Park,71 S. K. Park,31 J. Parsons,70 R. Partridge,77 N. Parua,54 A. Patwa,73 G. Pawloski,80 B. Penning,23 M. Perfilov,38 K. Peters,44 Y. Peters,26 P. Pétroff,16 M. Petteni,43 R. Piegaia,1 J. Piper,65 M.-A. Pleier,22 P. L. M. Podesta-Lerma,33,‡ V. M. Podstavkov,50 Y. Pogorelov,55 M.-E. Pol,2 P. Polozov,37 B. G. Pope,65 A. V. Popov,39 C. Potter,6 PRL 101, 011601 (2008) P H Y S I C A L R E V I E W L E T T E R S week ending 4 JULY 2008 0031-9007=08=101(1)=011601(7) 011601-1 © 2008 The American Physical Society W. L. Prado da Silva,3 H. B. Prosper,49 S. Protopopescu,73 J. Qian,64 A. Quadt,22,x B. Quinn,66 A. Rakitine,42 M. S. Rangel,2 K. Ranjan,28 P. N. Ratoff,42 P. Renkel,79 S. Reucroft,63 P. Rich,44 J. Rieger,54 M. Rijssenbeek,72 I. Ripp-Baudot,19 F. Rizatdinova,76 S. Robinson,43 R. F. Rodrigues,3 M. Rominsky,75 C. Royon,18 P. Rubinov,50 R. Ruchti,55 G. Safronov,37 G. Sajot,14 A. Sánchez-Hernández,33 M. P. Sanders,17 A. Santoro,3 G. Savage,50 L. Sawyer,60 T. Scanlon,43 D. Schaile,25 R. D. Schamberger,72 Y. Scheglov,40 H. Schellman,53 T. Schliephake,26 C. Schwanenberger,44 A. Schwartzman,68 R. Schwienhorst,65 J. Sekaric,49 H. Severini,75 E. Shabalina,51 M. Shamim,59 V. Shary,18 A. A. Shchukin,39 R. K. Shivpuri,28 V. Siccardi,19 V. Simak,10 V. Sirotenko,50 P. Skubic,75 P. Slattery,71 D. Smirnov,55 G. R. Snow,67 J. Snow,74 S. Snyder,73 S. Söldner-Rembold,44 L. Sonnenschein,17 A. Sopczak,42 M. Sosebee,78 K. Soustruznik,9 B. Spurlock,78 J. Stark,14 J. Steele,60 V. Stolin,37 D. A. Stoyanova,39 J. Strandberg,64 S. Strandberg,41 M. A. Strang,69 E. Strauss,72 M. Strauss,75 R. Ströhmer,25 D. Strom,53 L. Stutte,50 S. Sumowidagdo,49 P. Svoisky,55 A. Sznajder,3 P. Tamburello,45 A. Tanasijczuk,1 W. Taylor,6 J. Temple,45 B. Tiller,25 F. Tissandier,13 M. Titov,18 V. V. Tokmenin,36 T. Toole,61 I. Torchiani,23 T. Trefzger,24 D. Tsybychev,72 B. Tuchming,18 C. Tully,68 P. M. Tuts,70 R. Unalan,65 L. Uvarov,40 S. Uvarov,40 S. Uzunyan,52 B. Vachon,6 P. J. van den Berg,34 R. Van Kooten,54 W. M. van Leeuwen,34 N. Varelas,51 E. W. Varnes,45 I. A. Vasilyev,39 M. Vaupel,26 P. Verdier,20 L. S. Vertogradov,36 M. Verzocchi,50 F. Villeneuve-Seguier,43 P. Vint,43 P. Vokac,10 E. Von Toerne,59 M. Voutilainen,68,k R. Wagner,68 H. D. Wahl,49 L. Wang,61 M. H. L. S. Wang,50 J. Warchol,55 G. Watts,82 M. Wayne,55 G. Weber,24 M. Weber,50 L. Welty-Rieger,54 A. Wenger,23,{ N. Wermes,22 M. Wetstein,61 A. White,78 D. Wicke,26 G. W. Wilson,58 S. J. Wimpenny,48 M. Wobisch,60 D. R. Wood,63 T. R. Wyatt,44 Y. Xie,77 S. Yacoob,53 R. Yamada,50 M. Yan,61 T. Yasuda,50 Y. A. Yatsunenko,36 K. Yip,73 H. D. Yoo,77 S. W. Youn,53 J. Yu,78 A. Zatserklyaniy,52 C. Zeitnitz,26 T. Zhao,82 B. Zhou,64 J. Zhu,72 M. Zielinski,71 D. Zieminska,54 A. Zieminski,54,** L. Zivkovic,70 V. Zutshi,52 and E. G. Zverev38 (D0 Collaboration) 1Universidad de Buenos Aires, Buenos Aires, Argentina 2LAFEX, Centro Brasileiro de Pesquisas Fı́sicas, Rio de Janeiro, Brazil 3Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil 4Universidade Federal do ABC, Santo André, Brazil 5Instituto de Fı́sica Teórica, Universidade Estadual Paulista, São Paulo, Brazil 6University of Alberta, Edmonton, Alberta, Canada, Simon Fraser University, Burnaby, British Columbia, Canada, York University, Toronto, Ontario, Canada, and McGill University, Montreal, Quebec, Canada 7University of Science and Technology of China, Hefei, People’s Republic of China 8Universidad de los Andes, Bogotá, Colombia 9Center for Particle Physics, Charles University, Prague, Czech Republic 10Czech Technical University, Prague, Czech Republic 11Center for Particle Physics, Institute of Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic 12Universidad San Francisco de Quito, Quito, Ecuador 13LPC, Univ Blaise Pascal, CNRS/IN2P3, Clermont, France 14LPSC, Université Joseph Fourier Grenoble 1, CNRS/IN2P3, Institut National Polytechnique de Grenoble, France 15CPPM, IN2P3/CNRS, Université de la Méditerranée, Marseille, France 16LAL, Univ Paris-Sud, IN2P3/CNRS, Orsay, France 17LPNHE, IN2P3/CNRS, Universités Paris VI and VII, Paris, France 18DAPNIA/Service de Physique des Particules, CEA, Saclay, France 19IPHC, Université Louis Pasteur et Université de Haute Alsace, CNRS/IN2P3, Strasbourg, France 20IPNL, Université Lyon 1, CNRS/IN2P3, Villeurbanne, France and Université de Lyon, Lyon, France 21III. Physikalisches Institut A, RWTH Aachen, Aachen, Germany 22Physikalisches Institut, Universität Bonn, Bonn, Germany 23Physikalisches Institut, Universität Freiburg, Freiburg, Germany 24Institut für Physik, Universität Mainz, Mainz, Germany 25Ludwig-Maximilians-Universität München, München, Germany 26Fachbereich Physik, University of Wuppertal, Wuppertal, Germany 27Panjab University, Chandigarh, India 28Delhi University, Delhi, India 29Tata Institute of Fundamental Research, Mumbai, India 30University College Dublin, Dublin, Ireland 31Korea Detector Laboratory, Korea University, Seoul, Korea PRL 101, 011601 (2008) P H Y S I C A L R E V I E W L E T T E R S week ending 4 JULY 2008 011601-2 32SungKyunKwan University, Suwon, Korea 33CINVESTAV, Mexico City, Mexico 34FOM-Institute NIKHEF and University of Amsterdam/NIKHEF, Amsterdam, The Netherlands 35Radboud University Nijmegen/NIKHEF, Nijmegen, The Netherlands 36Joint Institute for Nuclear Research, Dubna, Russia 37Institute for Theoretical and Experimental Physics, Moscow, Russia 38Moscow State University, Moscow, Russia 39Institute for High Energy Physics, Protvino, Russia 40Petersburg Nuclear Physics Institute, St. Petersburg, Russia 41Lund University, Lund, Sweden, Royal Institute of Technology and Stockholm University, Stockholm, Sweden, and Uppsala University, Uppsala, Sweden 42Lancaster University, Lancaster, United Kingdom 43Imperial College, London, United Kingdom 44University of Manchester, Manchester, United Kingdom 45University of Arizona, Tucson, Arizona 85721, USA 46Lawrence Berkeley National Laboratory and University of California, Berkeley, California 94720, USA 47California State University, Fresno, California 93740, USA 48University of California, Riverside, California 92521, USA 49Florida State University, Tallahassee, Florida 32306, USA 50Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA 51University of Illinois at Chicago, Chicago, Illinois 60607, USA 52Northern Illinois University, DeKalb, Illinois 60115, USA 53Northwestern University, Evanston, Illinois 60208, USA 54Indiana University, Bloomington, Indiana 47405, USA 55University of Notre Dame, Notre Dame, Indiana 46556, USA 56Purdue University Calumet, Hammond, Indiana 46323, USA 57Iowa State University, Ames, Iowa 50011, USA 58University of Kansas, Lawrence, Kansas 66045, USA 59Kansas State University, Manhattan, Kansas 66506, USA 60Louisiana Tech University, Ruston, Louisiana 71272, USA 61University of Maryland, College Park, Maryland 20742, USA 62Boston University, Boston, Massachusetts 02215, USA 63Northeastern University, Boston, Massachusetts 02115, USA 64University of Michigan, Ann Arbor, Michigan 48109, USA 65Michigan State University, East Lansing, Michigan 48824, USA 66University of Mississippi, University, Mississippi 38677, USA 67University of Nebraska, Lincoln, Nebraska 68588, USA 68Princeton University, Princeton, New Jersey 08544, USA 69State University of New York, Buffalo, New York 14260, USA 70Columbia University, New York, New York 10027, USA 71University of Rochester, Rochester, New York 14627, USA 72State University of New York, Stony Brook, New York 11794, USA 73Brookhaven National Laboratory, Upton, New York 11973, USA 74Langston University, Langston, Oklahoma 73050, USA 75University of Oklahoma, Norman, Oklahoma 73019, USA 76Oklahoma State University, Stillwater, Oklahoma 74078, USA 77Brown University, Providence, Rhode Island 02912, USA 78University of Texas, Arlington, Texas 76019, USA 79Southern Methodist University, Dallas, Texas 75275, USA 80Rice University, Houston, Texas 77005, USA 81University of Virginia, Charlottesville, Virginia 22901, USA 82University of Washington, Seattle, Washington 98195, USA (Received 14 March 2008; published 30 June 2008) We report on a search for large extra dimensions in a data sample of approximately 1 fb�1 of p �p collisions at ��� s p � 1:96 TeV. We investigate Kaluza-Klein graviton production with a photon and missing transverse energy in the final state. At the 95% C.L. we set limits on the fundamental mass scale MD from 884 to 778 GeV for two to eight extra dimensions. DOI: 10.1103/PhysRevLett.101.011601 PACS numbers: 13.85.Rm, 11.10.Kk, 11.25.Wx PRL 101, 011601 (2008) P H Y S I C A L R E V I E W L E T T E R S week ending 4 JULY 2008 011601-3 http://dx.doi.org/10.1103/PhysRevLett.101.011601 Arkani-Hamed, Dimopoulos, and Dvali (ADD) [1] made the first attempt to solve the hierarchy problem of the standard model (SM) by postulating the existence of n new large extra spatial dimensions (LED). In this ap- proach, the SM particles are confined to a 3-dimensional brane while gravity is diluted in the larger volume. The size of the compactified extra space (R), the effective Planck scale in the 4-dimensional space-time (MPl), and the fundamental Planck scale in the �4� n�-dimensional space-time (MD), are related by the expression M2 Pl � 8�Mn�2 D Rn. Because of the compactification of the extra space, the gravitational field appears as a series of quan- tized energy states, which are referred to as Kaluza-Klein modes. A Kaluza-Klein graviton (GKK) behaves like a massive, noninteracting, stable particle whose direct pro- duction gives an imbalance in the final state momentum as its collider signature. In this Letter we report the results of a search for LED in the final state with a single photon plus missing transverse energy (�� E6 T), using data collected with the D0 detector at the Fermilab Tevatron collider. This signature arises from the process q �q! �GKK, which is studied in detail in [2]. The CDF collaboration carried out a similar search with 87 pb�1 of data, setting 95% C.L. lower limits onMD of 549, 581, and 601 GeV for 4, 6, and 8 extra dimensions, respectively [3]. Searches for LED in other final states have been performed by collaborations at the Tevatron [4,5] and the CERN LEP collider [6]. The background to the �� E6 T signal is dominated by electroweak boson production and noncollision back- ground where muons from the beam halo or cosmic rays undergo bremsstrahlung and produce an energetic photon. The electroweak background is dominated by the pro- cesses Z� �! � ��� �, W ! e� where the electron is misidentified as a photon, W � � where the lepton from the W boson decay is not detected, and W=Z� jet produc- tion where the jet is misidentified as a photon. The D0 detector [7] comprises a central-tracking system with a silicon microstrip tracker (SMT) and a central fiber tracker (CFT), both housed within a 2 T superconducting solenoidal magnet, with designs optimized for tracking and vertexing at j�j< 3 and j�j< 2:5, respectively, where� is the pseudorapidity [8] measured with respect to the geo- metrical center of the detector. The central preshower system (CPS) is located in front of a liquid-argon–uranium calorimeter and consists of three layers of scintillating strips, providing precise measurement of electromagnetic (EM) shower positions. The calorimeter has a central section (CC) covering j�j � 1:1, and two end sections (EC) that extend coverage to j�j � 4:2 [9]. Each part contains an EM section closest to the interaction region followed by fine and coarse hadronic sections. The EM section has four longitudinal layers and transverse segmen- tation of 0:1� 0:1 in �-� space (where � is the azimuthal angle), with the exception of the third layer, where it is 0:05� 0:05. Additionally, scintillators between the CC and EC cryostats provide sampling of developing showers for 1:1< j�j< 1:4. The outer muon system, covering j�j< 2, consists of a layer of tracking detectors and scin- tillation trigger counters in front of 1.8 T iron toroids, followed by two similar layers after the toroids. The data in this analysis were recorded using triggers requiring at least one energy cluster in the EM section of the calorime- ter with transverse momentum pT > 20 GeV. The triggers are almost 100% efficient to select signal events. This set of data corresponds to an integrated luminosity of 1:05 0:06 fb�1 [10]. We identify a reconstructed calorimeter cluster as a photon when it satisfies the following requirements: (i) at least 90% of the energy is deposited in the EM section of the calorimeter; (ii) the calorimeter isolation variable I � Etot�0:4� � Eem�0:2��=Eem�0:2� is less than 0.07, where Etot�0:4� denotes the total energy deposited in the calo- rimeter in a cone of radius R � ��������������������������������� ����2 � ����2 p � 0:4, and Eem�0:2� is the EM energy in a cone of radius R � 0:2; (iii) the track isolation variable, defined as the scalar sum of the transverse momenta of all tracks that originate from the interaction vertex in an annulus of 0:05 90 GeV, at least one recon- structed interaction vertex consistent with the measured direction of the photon (see below), and E6 T > 70 GeV. Additionally, in order to avoid large E6 T due to mismeasure- ment of jet energy, we require no jets with pT > 15 GeV. The reduction of the signal efficiency due to the jet veto on initial state radiation has been estimated using PYTHIA [12] to be about 9%. The applied E6 T requirement guarantees negligible multijet background in the final candidate sam- ple while being almost fully efficient for signal selection. We reject events with reconstructed muons and with cosmic ray muons identified using the timing of the signal in the muon scintillation counters or by the presence of a characteristic pattern of hits in the muon drift chambers that is aligned with the reconstructed photon. In order to further reject events with leptons that leave a distinguish- able signature in the tracker but that are not reconstructed in the other subsystems of the detector, we impose a requirement on the pT of any isolated track not to be PRL 101, 011601 (2008) P H Y S I C A L R E V I E W L E T T E R S week ending 4 JULY 2008 011601-4 greater than 6.5 GeV. A track is considered to be isolated if the ratio between the scalar sum of the transverse momenta of all tracks that originate from the interaction vertex in an annulus of 0:1 884, 864, 836, 820, 797, 797, and 778 GeV for n � 2, 3, 4, 5, 6, 7 and 8 extra dimensions, respectively. Table II and Fig. 3 summarize the results for the limit calculations. To conclude, we have conducted a search for LED in the �� E6 T channel, finding no evidence for their presence. We have set limits on the fundamental Planck scale, sig- nificantly improving results of previous searches. TABLE II. Summary of limit calculations. n Signal efficiency Observed (expected) cross section limit (fb) Observed (expected) limit (GeV) 2 0:49 0:04 27.6 (23.4) 884 (921) 3 0:48 0:04 24.5 (22.7) 864 (877) 4 0:47 0:04 25.0 (22.8) 836 (848) 5 0:43 0:04 25.0 (24.8) 820 (821) 6 0:50 0:05 25.4 (22.3) 797 (810) 7 0:49 0:04 24.0 (23.1) 797 (801) 8 0:52 0:05 24.2 (21.9) 778 (786) Number of Extra Dimensions 2 3 4 5 6 7 8 [ T eV ] D M 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 expected limit observed limit limit-1CDF 87 pb LEP combined limit -1DØ, 1.05 fb FIG. 3 (color online). Expected and observed lower limits on MD for LED in the �� E6 T final state. CDF limits with 87 pb�1 of data [3], and the LEP combined limits [6] are also shown. PRL 101, 011601 (2008) P H Y S I C A L R E V I E W L E T T E R S week ending 4 JULY 2008 011601-6 We thank Stephen Mrenna for his help with generating MC signal events, the staffs at Fermilab and collaborating institutions, and acknowledge support from the DOE and NSF (USA); CEA and No. CNRS/IN2P3 (France); FASI, Rosatom and RFBR (Russia); CNPq, FAPERJ, FAPESP and FUNDUNESP (Brazil); DAE and DST (India); Colciencias (Colombia); CONACyT (Mexico); KRF and KOSEF (Korea); CONICET and UBACyT (Argentina); FOM (The Netherlands); STFC (United Kingdom); MSMT and GACR (Czech Republic); CRC Program, CFI, NSERC and WestGrid Project (Canada); BMBF and DFG (Germany); SFI (Ireland); The Swedish Research Council (Sweden); CAS and CNSF (China); and the Alexander von Humboldt Foundation. *Visitor from Augustana College, Sioux Falls, SD, USA. †Visitor from The University of Liverpool, Liverpool, United Kingdom. ‡Visitor from ICN-UNAM, Mexico City, Mexico. xVisitor from II. Physikalisches Institut, Georg-August- University, Göttingen, Germany. kVisitor from Helsinki Institute of Physics, Helsinki, Finland. {Visitor from Universität Zürich, Zürich, Switzerland. **Deceased. [1] N. Arkani-Hamed, S. Dimopoulos, and G. Dvali, Phys. Lett. B 429, 263 (1998). [2] G. Guidice, R. Rattazzi, and J. Wells, Nucl. Phys. B544, 3 (1999). [3] D. Acosta et al. (CDF Collaboration), Phys. Rev. Lett. 89, 281801 (2002). [4] B. Abbott et al. (D0 Collaboration), Phys. Rev. Lett. 86, 1156 (2001); 90, 251802 (2003); ibid.95, 161602 (2005). [5] D. Acosta et al. (CDF Collaboration), Phys. Rev. Lett. 92, 121802 (2004). [6] LEP Exotica Working Group, URL: http://lepexotica.web. cern.ch/LEPEXOTICA/notes/2004-03/ed_note_final .ps.gz, and references therein. [7] V. M. Abazov et al. (D0 Collaboration), Nucl. Instrum. Methods Phys. Res., Sect. A 565, 463 (2006). [8] Pseudorapidity is defined as� ln tan��=2��, where � is the angle between the particle and the proton beam direction. [9] S. 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