Search for resonant pair production of neutral long-lived particles decaying to bbbar in ppbar collisions at sqrt(s)=1.96 TeV
aa r X i v : . [ h e p - e x ] J u l FERMILAB-PUB-09-299-E
Search for resonant pair production of neutral long-lived particles decaying to bb in pp collisions at √ s = 1 .
96 TeV
V.M. Abazov , B. Abbott , M. Abolins , B.S. Acharya , M. Adams , T. Adams , E. Aguilo , M. Ahsan ,G.D. Alexeev , G. Alkhazov , A. Alton ,a , G. Alverson , G.A. Alves , L.S. Ancu , T. Andeen , M.S. Anzelc ,M. Aoki , Y. Arnoud , M. Arov , M. Arthaud , A. Askew ,b , B. ˚Asman , O. Atramentov ,b , C. Avila ,J. BackusMayes , F. Badaud , L. Bagby , B. Baldin , D.V. Bandurin , S. Banerjee , E. Barberis ,A.-F. Barfuss , P. Bargassa , P. Baringer , J. Barreto , J.F. Bartlett , U. Bassler , D. Bauer , S. Beale ,A. Bean , M. Begalli , M. Begel , C. Belanger-Champagne , L. Bellantoni , A. Bellavance , J.A. Benitez ,S.B. Beri , G. Bernardi , R. Bernhard , I. Bertram , M. Besan¸con , R. Beuselinck , V.A. Bezzubov ,P.C. Bhat , V. Bhatnagar , G. Blazey , S. Blessing , K. Bloom , A. Boehnlein , D. Boline , T.A. Bolton ,E.E. Boos , G. Borissov , T. Bose , A. Brandt , R. Brock , G. Brooijmans , A. Bross , D. Brown ,X.B. Bu , D. Buchholz , M. Buehler , V. Buescher , V. Bunichev , S. Burdin ,c , T.H. Burnett ,C.P. Buszello , P. Calfayan , B. Calpas , S. Calvet , J. Cammin , M.A. Carrasco-Lizarraga , E. Carrera ,W. Carvalho , B.C.K. Casey , H. Castilla-Valdez , S. Chakrabarti , D. Chakraborty , K.M. Chan ,A. Chandra , E. Cheu , D.K. Cho , S. Choi , B. Choudhary , T. Christoudias , S. Cihangir , D. Claes ,J. Clutter , M. Cooke , W.E. Cooper , M. Corcoran , F. Couderc , M.-C. Cousinou , S. Cr´ep´e-Renaudin ,D. Cutts , M. ´Cwiok , A. Das , G. Davies , K. De , S.J. de Jong , E. De La Cruz-Burelo , K. DeVaughan ,F. D´eliot , M. Demarteau , R. Demina , D. Denisov , S.P. Denisov , S. Desai , H.T. Diehl , M. Diesburg ,A. Dominguez , T. Dorland , A. Dubey , L.V. Dudko , L. Duflot , D. Duggan , A. Duperrin , S. Dutt ,A. Dyshkant , M. Eads , D. Edmunds , J. Ellison , V.D. Elvira , Y. Enari , S. Eno , M. Escalier ,H. Evans , A. Evdokimov , V.N. Evdokimov , G. Facini , A.V. Ferapontov , T. Ferbel , , F. Fiedler ,F. Filthaut , W. Fisher , H.E. Fisk , M. Fortner , H. Fox , S. Fu , S. Fuess , T. Gadfort , C.F. Galea ,A. Garcia-Bellido , V. Gavrilov , P. Gay , W. Geist , W. Geng , , C.E. Gerber , Y. Gershtein ,b ,D. Gillberg , G. Ginther , , B. G´omez , A. Goussiou , P.D. Grannis , S. Greder , H. Greenlee ,Z.D. Greenwood , E.M. Gregores , G. Grenier , Ph. Gris , J.-F. Grivaz , A. Grohsjean , S. Gr¨unendahl ,M.W. Gr¨unewald , F. Guo , J. Guo , G. Gutierrez , P. Gutierrez , A. Haas , P. Haefner , S. Hagopian ,J. Haley , I. Hall , R.E. Hall , L. Han , K. Harder , A. Harel , J.M. Hauptman , J. Hays , T. Hebbeker ,D. Hedin , J.G. Hegeman , A.P. Heinson , U. Heintz , C. Hensel , I. Heredia-De La Cruz , K. Herner ,G. Hesketh , M.D. Hildreth , R. Hirosky , T. Hoang , J.D. Hobbs , B. Hoeneisen , M. Hohlfeld ,S. Hossain , P. Houben , Y. Hu , Z. Hubacek , N. Huske , V. Hynek , I. Iashvili , R. Illingworth , A.S. Ito ,S. Jabeen , M. Jaffr´e , S. Jain , K. Jakobs , D. Jamin , R. Jesik , K. Johns , C. Johnson , M. Johnson ,D. Johnston , A. Jonckheere , P. Jonsson , A. Juste , E. Kajfasz , D. Karmanov , P.A. Kasper ,I. Katsanos , V. Kaushik , R. Kehoe , S. Kermiche , N. Khalatyan , A. Khanov , A. Kharchilava ,Y.N. Kharzheev , D. Khatidze , T.J. Kim , M.H. Kirby , M. Kirsch , B. Klima , J.M. Kohli ,J.-P. Konrath , A.V. Kozelov , J. Kraus , T. Kuhl , A. Kumar , A. Kupco , T. Kurˇca , V.A. Kuzmin ,J. Kvita , F. Lacroix , D. Lam , S. Lammers , G. Landsberg , P. Lebrun , W.M. Lee , A. Leflat ,J. Lellouch , J. Li , ‡ , L. Li , Q.Z. Li , S.M. Lietti , J.K. Lim , D. Lincoln , J. Linnemann , V.V. Lipaev ,R. Lipton , Y. Liu , Z. Liu , A. Lobodenko , M. Lokajicek , P. Love , H.J. Lubatti , R. Luna-Garcia ,d ,A.L. Lyon , A.K.A. Maciel , D. Mackin , P. M¨attig , R. Maga˜na-Villalba , A. Magerkurth , P.K. Mal ,H.B. Malbouisson , S. Malik , V.L. Malyshev , Y. Maravin , B. Martin , R. McCarthy , C.L. McGivern ,M.M. Meijer , A. Melnitchouk , L. Mendoza , D. Menezes , P.G. Mercadante , M. Merkin , K.W. Merritt ,A. Meyer , J. Meyer , J. Mitrevski , N.K. Mondal , R.W. Moore , T. Moulik , G.S. Muanza , M. Mulhearn ,O. Mundal , L. Mundim , E. Nagy , M. Naimuddin , M. Narain , H.A. Neal , J.P. Negret , P. Neustroev ,H. Nilsen , H. Nogima , S.F. Novaes , T. Nunnemann , G. Obrant , C. Ochando , D. Onoprienko ,J. Orduna , N. Oshima , N. Osman , J. Osta , R. Otec , G.J. Otero y Garz´on , M. Owen , M. Padilla ,P. Padley , M. Pangilinan , N. Parashar , S.-J. Park , S.K. Park , J. Parsons , R. Partridge , N. Parua ,A. Patwa , G. Pawloski , B. Penning , M. Perfilov , K. Peters , Y. Peters , P. P´etroff , R. Piegaia ,J. Piper , M.-A. Pleier , P.L.M. Podesta-Lerma ,e , V.M. Podstavkov , Y. Pogorelov , M.-E. Pol , P. Polozov ,A.V. Popov , W.L. Prado da Silva , S. Protopopescu , J. Qian , A. Quadt , B. Quinn , A. Rakitine ,M.S. Rangel , K. Ranjan , P.N. Ratoff , P. Renkel , P. Rich , M. Rijssenbeek , I. Ripp-Baudot ,F. Rizatdinova , S. Robinson , M. Rominsky , C. Royon , P. Rubinov , R. Ruchti , G. Safronov , G. Sajot ,A. S´anchez-Hern´andez , M.P. Sanders , B. Sanghi , G. Savage , L. Sawyer , T. Scanlon , D. Schaile ,R.D. Schamberger , Y. Scheglov , H. Schellman , T. Schliephake , S. Schlobohm , C. Schwanenberger ,R. Schwienhorst , J. Sekaric , H. Severini , E. Shabalina , M. Shamim , V. Shary , A.A. Shchukin ,R.K. Shivpuri , V. Siccardi , V. Simak , V. Sirotenko , P. Skubic , P. Slattery , D. Smirnov , G.R. Snow ,J. Snow , S. Snyder , S. S¨oldner-Rembold , L. Sonnenschein , A. Sopczak , M. Sosebee , K. Soustruznik ,B. Spurlock , J. Stark , V. Stolin , D.A. Stoyanova , J. Strandberg , M.A. Strang , E. Strauss , M. Strauss ,R. Str¨ohmer , D. Strom , L. Stutte , S. Sumowidagdo , P. Svoisky , M. Takahashi , A. Tanasijczuk ,W. Taylor , B. Tiller , M. Titov , V.V. Tokmenin , I. Torchiani , D. Tsybychev , B. Tuchming , C. Tully ,P.M. Tuts , R. Unalan , L. Uvarov , S. Uvarov , S. Uzunyan , P.J. van den Berg , R. Van Kooten ,W.M. van Leeuwen , N. Varelas , E.W. Varnes , I.A. Vasilyev , P. Verdier , L.S. Vertogradov , M. Verzocchi ,D. Vilanova , P. Vint , P. Vokac , M. Voutilainen ,f , R. Wagner , H.D. Wahl , M.H.L.S. Wang ,J. Warchol , G. Watts , M. Wayne , G. Weber , M. Weber ,g , L. Welty-Rieger , A. Wenger ,h ,M. Wetstein , A. White , D. Wicke , M.R.J. Williams , G.W. Wilson , S.J. Wimpenny , M. Wobisch ,D.R. Wood , T.R. Wyatt , Y. Xie , C. Xu , S. Yacoob , R. Yamada , W.-C. Yang , T. Yasuda ,Y.A. Yatsunenko , Z. Ye , H. Yin , K. Yip , H.D. Yoo , S.W. Youn , J. Yu , C. Zeitnitz , S. Zelitch ,T. Zhao , B. Zhou , J. Zhu , M. Zielinski , D. Zieminska , L. Zivkovic , V. Zutshi , and E.G. Zverev (The DØ Collaboration) Universidad de Buenos Aires, Buenos Aires, Argentina LAFEX, Centro Brasileiro de Pesquisas F´ısicas, Rio de Janeiro, Brazil Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil Universidade Federal do ABC, Santo Andr´e, Brazil Instituto de F´ısica Te´orica, Universidade Estadual Paulista, S˜ao Paulo, Brazil University of Alberta, Edmonton, Alberta, Canada; Simon Fraser University,Burnaby, British Columbia, Canada; York University, Toronto,Ontario, Canada and McGill University, Montreal, Quebec, Canada University of Science and Technology of China, Hefei, People’s Republic of China Universidad de los Andes, Bogot´a, Colombia Center for Particle Physics, Charles University,Faculty of Mathematics and Physics, Prague, Czech Republic Czech Technical University in Prague, Prague, Czech Republic Center for Particle Physics, Institute of Physics,Academy of Sciences of the Czech Republic, Prague, Czech Republic Universidad San Francisco de Quito, Quito, Ecuador LPC, Universit´e Blaise Pascal, CNRS/IN2P3, Clermont, France LPSC, Universit´e Joseph Fourier Grenoble 1, CNRS/IN2P3,Institut National Polytechnique de Grenoble, Grenoble, France CPPM, Aix-Marseille Universit´e, CNRS/IN2P3, Marseille, France LAL, Universit´e Paris-Sud, IN2P3/CNRS, Orsay, France LPNHE, IN2P3/CNRS, Universit´es Paris VI and VII, Paris, France CEA, Irfu, SPP, Saclay, France IPHC, Universit´e de Strasbourg, CNRS/IN2P3, Strasbourg, France IPNL, Universit´e Lyon 1, CNRS/IN2P3, Villeurbanne, France and Universit´e de Lyon, Lyon, France III. Physikalisches Institut A, RWTH Aachen University, Aachen, Germany Physikalisches Institut, Universit¨at Bonn, Bonn, Germany Physikalisches Institut, Universit¨at Freiburg, Freiburg, Germany II. Physikalisches Institut, Georg-August-Universit¨at G¨ottingen, G¨ottingen, Germany Institut f¨ur Physik, Universit¨at Mainz, Mainz, Germany Ludwig-Maximilians-Universit¨at M¨unchen, M¨unchen, Germany Fachbereich Physik, University of Wuppertal, Wuppertal, Germany Panjab University, Chandigarh, India Delhi University, Delhi, India Tata Institute of Fundamental Research, Mumbai, India University College Dublin, Dublin, Ireland Korea Detector Laboratory, Korea University, Seoul, Korea SungKyunKwan University, Suwon, Korea CINVESTAV, Mexico City, Mexico FOM-Institute NIKHEF and University of Amsterdam/NIKHEF, Amsterdam, The Netherlands Radboud University Nijmegen/NIKHEF, Nijmegen, The Netherlands Joint Institute for Nuclear Research, Dubna, Russia Institute for Theoretical and Experimental Physics, Moscow, Russia Moscow State University, Moscow, Russia Institute for High Energy Physics, Protvino, Russia Petersburg Nuclear Physics Institute, St. Petersburg, Russia Stockholm University, Stockholm, Sweden, and Uppsala University, Uppsala, Sweden Lancaster University, Lancaster, United Kingdom Imperial College, London, United Kingdom University of Manchester, Manchester, United Kingdom University of Arizona, Tucson, Arizona 85721, USA California State University, Fresno, California 93740, USA University of California, Riverside, California 92521, USA Florida State University, Tallahassee, Florida 32306, USA Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA University of Illinois at Chicago, Chicago, Illinois 60607, USA Northern Illinois University, DeKalb, Illinois 60115, USA Northwestern University, Evanston, Illinois 60208, USA Indiana University, Bloomington, Indiana 47405, USA University of Notre Dame, Notre Dame, Indiana 46556, USA Purdue University Calumet, Hammond, Indiana 46323, USA Iowa State University, Ames, Iowa 50011, USA University of Kansas, Lawrence, Kansas 66045, USA Kansas State University, Manhattan, Kansas 66506, USA Louisiana Tech University, Ruston, Louisiana 71272, USA University of Maryland, College Park, Maryland 20742, USA Boston University, Boston, Massachusetts 02215, USA Northeastern University, Boston, Massachusetts 02115, USA University of Michigan, Ann Arbor, Michigan 48109, USA Michigan State University, East Lansing, Michigan 48824, USA University of Mississippi, University, Mississippi 38677, USA University of Nebraska, Lincoln, Nebraska 68588, USA Princeton University, Princeton, New Jersey 08544, USA State University of New York, Buffalo, New York 14260, USA Columbia University, New York, New York 10027, USA University of Rochester, Rochester, New York 14627, USA State University of New York, Stony Brook, New York 11794, USA Brookhaven National Laboratory, Upton, New York 11973, USA Langston University, Langston, Oklahoma 73050, USA University of Oklahoma, Norman, Oklahoma 73019, USA Oklahoma State University, Stillwater, Oklahoma 74078, USA Brown University, Providence, Rhode Island 02912, USA University of Texas, Arlington, Texas 76019, USA Southern Methodist University, Dallas, Texas 75275, USA Rice University, Houston, Texas 77005, USA University of Virginia, Charlottesville, Virginia 22901, USA and University of Washington, Seattle, Washington 98195, USA (Dated: June 9, 2009)We report on a first search for resonant pair production of neutral long-lived particles (NLLP)which each decay to a bb pair, using 3.6 fb − of data recorded with the D0 detector at the FermilabTevatron collider. We search for pairs of displaced vertices in the tracking detector at radii in therange 1.6–20 cm from the beam axis. No significant excess is observed above background, and upperlimits are set on the production rate in a hidden-valley benchmark model for a range of Higgs bosonmasses and NLLP masses and lifetimes. PACS numbers: 12.60.Fr, 14.80.Cp
A class of hidden-valley (HV) models [1] predicts anew, confining gauge group that is weakly coupled to thestandard model (SM), leading to the production of HVparticles (v-particles). The details of v-particle decay de- pend on the specific model, but the HV quarks alwayshadronize due to confinement producing “v-hadrons”that can be long-lived. One particular model used asa benchmark for this search is the SM Higgs boson ( H )mixing with a HV Higgs boson that gives mass to v-particles. The SM Higgs boson could then decay di-rectly to v-hadrons through this mixing with a substan-tial branching fraction [2]. These v-hadrons may couplepreferentially to heavy SM particles, such as b quarks,due to helicity suppression. The result is a striking ex-perimental signature of highly displaced secondary ver-tices (SV) with a large number of attached tracks fromthe b quark decays. Direct searches at the CERN LEPcollider have excluded a Higgs boson decaying to b ¯ b or τ ¯ τ with M H < . bb , only the mostgeneral LEP limit is relevant, M H >
81 GeV, for anyHiggs boson radiating off a Z boson [4]. Cosmologicalconstraints require that one of the light v-hadrons havea lifetime ≪ b quark pair, using the D0 detector [5] at theFermilab Tevatron pp collider. The b quarks are requiredin order to provide a high transverse momentum ( p T )muon for triggering with high efficiency. The data werecollected from April 2002 to August 2008 and correspondto an integrated luminosity of 3.6 fb − at √ s = 1 .
96 TeV.The D0 central tracking detector comprises a silicon mi-crostrip tracker (SMT) and a central fiber tracker (CFT),both located within a 2 T superconducting solenoidalmagnet. The SMT, extending from a radius of ≈ ≈
10 cm, has a six-barrel longitudinal structure, eachwith a set of four layers arranged axially around thebeam pipe, and interspersed with 16 radial disks. TheCFT, extending from a radius of ≈
20 cm to ≈
50 cm, haseight thin coaxial barrels, each supporting two doubletsof overlapping scintillating fibers. Secondary vertices arereconstructed by combining charged particle tracks foundin the tracking detector, which effectively limits the anal-ysis to NLLP decays occurring within a maximum radiusof 20 cm, well within the tracker volume. We also excludevertex radii less than 1.6 cm since the background fromheavy flavor production is large in that region. Knownsources of SVs other than heavy-flavor include decays in-flight of light particles, inelastic interactions of particleswith nuclei of detector material, and photon conversions.Vertices may also be mimicked by pattern recognitionerrors. pythia [6] is used to simulate signal and backgroundevents, which are then passed through a full geant gg → H process is generated, the Higgs boson is forced to decayto a pair of long-lived A bosons (a heavy, neutral scalar,representing a v-hadron), and each A boson is forced todecay to a pair of b quarks. The Higgs boson mass ( M H )is varied from 90 to 200 GeV, the v-hadron mass ( m HV ) X (cm)-10 -5 0 5 10 Y ( c m ) -10-50510 110 SV per 0.0016 cm -1 , 3.6 fbOD FIG. 1: Material map in the plane transverse to the beam-line, generated using SVs with three attached tracks, in eventspassing the initial selection. The structure of the silicon de-tector and supports are clearly seen. from 15 to 40 GeV and the average v-hadron proper de-cay length ( L d = cτ ) from 2.5 cm to 10 cm. For back-ground, inclusive pp multijet events are generated. Ap-proximately one hundred thousand Monte Carlo (MC)events for each signal sample and ten million events ofmultijet background are generated and are overlaid withdata to simulate detector noise and pile-up effects fromadditional pp interactions.At least two jets with a cone radius of 0.5 [8] are re-quired, each with p T >
10 GeV. And at least one muonis required with p T > R < . R = p (∆ φ ) + (∆ η ) with φ being the azimuthal angle and η the pseudorapidity.The muon requirement is more efficient for signal thanbackground due to the presence of a b → µ or b → c → µ decay from at least one of the four b quarks, and is alsorequired for an accurate measurement of the trigger ef-ficiency. Primary vertices (PVs) are reconstructed byclustering tracks and correspond to pp interaction lo-cations. To ensure good SV reconstruction, we furtherrequire fewer than four PVs be reconstructed and thatthe selected PV with the largest P i log p iT , summed overall vertex tracks i , be located within | z | <
35 cm and r < x and y are the horizontal and verticalcomponents of the distance r with respect to the beamaxis, and z is the distance along the beam axis from thecenter of the detector. An initial selection requires thateach event has at least one SV with 2D decay length fromthe PV in the plane transverse to the beam ( L xyd ) largerthan 1 cm and decay length significance (decay lengthdivided by its uncertainty) greater than five. The mo-mentum of the SV, reconstructed from the vectorial sumof the momenta of its associated tracks, must point awayfrom the PV to reduce combinatoric background. SVs arereconstructed using a track selection so as to efficientlycombine the b and ¯ b decay products of each v-hadron intoa single SV. Approximately 50 million data events satisfythese requirements, dominated by dijet and heavy-flavorproduction.To maximize the discovery potential of this analysis weuse an OR of all triggers. The most frequently fired trig-gers that make up the dataset passing the initial selectioninvolve a muon and jet at the first trigger level and re-finements of these objects at higher levels. The overalltrigger OR efficiency is estimated by first measuring theefficiency for a single trigger per data collection periodusing known muon and jet trigger efficiencies. Then thenumber of events fired by that single trigger is comparedto the total number of data events passing the OR ofall triggers, as a function of sensitive variables, such asmuon p T , jet p T , jet angles, etc. No significant depen-dence is found, except on jet p T , thus the overall triggerOR efficiency is modeled as a function of jet p T .Further selections are optimized by maximizing the ex-pected signal significance ( S/ √ S + B ), where B and S are the number of MC background and signal events,respectively. The heavy-flavor background, mainly b hadrons with cτ ≈ L xyd > π , protons, etc.) with detector material, suchas silicon sensors, cables, etc., are the major source ofbackground. In order to quantify the material regions,we construct a map of SV density in data, using SV withtrack multiplicity of three, in the xy (see Fig. 1) and rz projections. SVs that occur in regions of high SVdensity are then removed. After this “pre-selection” isperformed, the multijet background MC sample is nor-malized to the data (see Table I). Finally, at least twoSVs are required in each event, and they are required tohave ∆ R ( SV , SV > TABLE I: Summary of event selections, showing the remain-ing background, data, and signal events (for M H =120 GeVand L d =5 cm) after each selection. Background is normalizedto data after pre-selection. N bkgd N data m HV = m HV =15 GeV 40 GeVProduced - - 2712 2712Initial selection - 4.9 ×
235 173Trigger - 4.9 ×
174 77SV L xyd > ×
153 66SV mult. ≥ ×
72 25SV density 6.0 × ×
60 15Num. SV ≥ Min(SV1,SV2) Mass (GeV)0 2 4 6 8 10 E ve n t s / . G e V -2 -1 -1 , 3.6 fbOD Data Bkgd Signal FIG. 2: The minimum mass of the two SVs, for data,background MC, and signal MC with M H =120 GeV, m HV =15 GeV, and L d =5 cm. The hatched region showsthe uncertainty on the background MC. Max(SV1,SV2) Collinearity0.97 0.98 0.99 1 E ve n t s / . -2 -1 -1 , 3.6 fbOD Data Bkgd Signal FIG. 3: The maximum collinearity of the two SVs, fordata, background MC, and signal MC with M H =120 GeV, m HV =40 GeV, and L d =5 cm. The hatched region shows theuncertainty on the background MC. multijet background simulation of the SV invariant massand SV collinearity distributions to data. The events af-ter pre-selection are divided into two distinct sets: thefirst contains events with only one SV (1SV), whereasthe second contains events with at least two SVs (2SV).Since the signal content of the 1SV set is expected to be < m HV <
20 GeV, a requirement on the minimum SVmass in an event > < σ ( H + X ) × BR( H → HV HV ) × BR ( HV → bb ) using amodified frequentist method [11], which includes all sys-tematic uncertainties on signal acceptance, background,and luminosity. Depending on the signal parameters,Higgs boson production about 1–10 times the SM crosssection is excluded, if the Higgs boson always decays toa pair of long-lived v-hadrons decaying only to bb (seeFig. 4). These results also provide the first constraintson pair-produced NLLPs decaying to b jets in the radialrange of 1.6–20 cm at a hadron collider.We thank the staffs at Fermilab and collaboratinginstitutions, and acknowledge support from the DOE (GeV) H M
80 100 120 140 160 180 200 bb ) ( pb ) fi ( H V BR · H V H V ) fi BR ( H · ( H + X ) s -1 =5 cm d =15 GeV, L HV m -1 , 3.6 fbOD Observed limitExpected limitTheory (GeV) H M
80 100 120 140 160 180 200 bb ) ( pb ) fi ( H V BR · H V H V ) fi BR ( H · ( H + X ) s -1 =5 cm d =40 GeV, L HV m -1 , 3.6 fbOD Observed limitExpected limitTheoryDecay length (cm) bb ) ( pb ) fi ( H V BR · H V H V ) fi BR ( H · ( H + X ) s =15 GeV HV =120 GeV, m H M -1 , 3.6 fbOD Observed limitExpected limitSM Higgs FIG. 4: The expected and observed 95% C.L. limitson σ ( H + X ) × BR( H → HV HV ) × BR ( HV → bb ) for each M H studied, m HV = 15, 40 GeV, and various values of v-hadron L d . The green band shows the ± H → HV HV ) and BR( HV → bb ). (color online) and NSF (USA); CEA and CNRS/IN2P3 (France);FASI, Rosatom and RFBR (Russia); CNPq, FAPERJ,FAPESP and FUNDUNESP (Brazil); DAE and DST (In-dia); Colciencias (Colombia); CONACyT (Mexico); KRFand KOSEF (Korea); CONICET and UBACyT (Ar-gentina); FOM (The Netherlands); STFC and the RoyalSociety (United Kingdom); MSMT and GACR (Czech TABLE II: Results for each simulated signal: the numbers of background, signal, and data events after all selections, overallsignal efficiency, SM Higgs production rate, and observed and expected 95% C.L. upper limits on the signal cross section. M H m HV L d N bkgd ± stat ± sys N sig ± stat ± sys N data Efficiency SM Higgs (pb) Limit obs. [exp.] (pb)90 GeV 15 GeV 5 cm 4 . ± . ± . . ± . ± . . ± . ± . . ± . ± . . ± . ± . . ± . ± . . ± . ± . . ± . ± . . ± . ± . . ± . ± . . ± . ± .
02 0 . ± . ± .
03 1 0.003% 2.0 67 [51]120 GeV 40 GeV 5 cm 0 . ± . ± .
02 0 . ± . ± .
06 1 0.01% 1.1 16 [12]200 GeV 40 GeV 5 cm 0 . ± . ± .
02 0 . ± . ± .
02 1 0.03% 0.2 6.5 [5.1]
Republic); CRC Program, CFI, NSERC and WestGridProject (Canada); BMBF and DFG (Germany); SFI (Ire-land); The Swedish Research Council (Sweden); CAS andCNSF (China); and the Alexander von Humboldt Foun-dation (Germany). [a] Visitor from Augustana College, Sioux Falls, SD, USA.[b] Visitor from Rutgers University, Piscataway, NJ, USA.[c] Visitor from The University of Liverpool, Liverpool, UK.[d] Visitor from Centro de Investigacion en Computacion -IPN, Mexico City, Mexico.[e] Visitor from ECFM, Universidad Autonoma de Sinaloa,Culiac´an, Mexico.[f] Visitor from Helsinki Institute of Physics, Helsinki, Fin-land.[g] Visitor from Universit¨at Bern, Bern, Switzerland.[h] Visitor from Universit¨at Z¨urich, Z¨urich, Switzerland. [ ‡ ] Deceased.[1] M. J. Strassler and K. M. Zurek, Phys. Lett. B , 374(2007).[2] M. J. Strassler and K. M. Zurek, Phys. Lett. B , 263(2008).[3] R. Barate et al. , Phys. Lett. B , 61 (2003).[4] S. Chang, R. Dermisek, J. F. Gunion, and N. Weiner,Ann. Rev. Nucl. Part. Sci. , 75 (2008).[5] D0 Collaboration, V. Abazov et al. , Nucl. Instrum. Meth-ods Phys. Res. A. , 463 (2006).[6] T. Sj¨ostrand et al. , Comput. Phys. Commun. , 238(2001).[7] R. Brun and F. Carminati, CERN Program Library LongWriteup W5013, 1993 (unpublished).[8] G. C. Blazey et al. , arXiv:hep-ex/0005012 (2000).[9] T. Andeen et al. , FERMILAB-TM-2365 (2007).[10] D. de Florian and M. Grazzini, Phys. Lett. B , 291(2009).[11] T. Junk, Nucl. Instrum. Methods A.434