Observation of the associated production of a single top quark and a W boson in pp collisions at sqrt[s] = 8 TeV

The first observation of the associated production of a single top quark and a W boson is presented. The analysis is based on a data set corresponding to an integrated luminosity of 12.2 fb(-1) of proton-proton collisions at sqrt[s] = 8 TeV recorded by the CMS experiment at the LHC. Events with two leptons and a jet originating from a b quark are selected. A multivariate analysis based on kinematic and topological properties is used to separate the signal from the dominant tt background. An excess consistent with the signal hypothesis is observed, with a significance which corresponds to 6.1 standard deviations above a background-only hypothesis. The measured production cross section is 23.4 ± 5.4 pb, in agreement with the standard model prediction.

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Probing color coherence effects in pp collisions at [Formula: see text]

A study of color coherence effects in pp collisions at a center-of-mass energy of 7[Formula: see text] is presented. The data used in the analysis were collected in 2010 with the CMS detector at the LHC and correspond to an integrated luminosity of 36 pb[Formula: see text]. Events are selected that contain at least three jets and where the two jets with the largest transverse momentum exhibit a back-to-back topology. The measured angular correlation between the second- and third-leading jet is shown to be sensitive to color coherence effects, and is compared to the predictions of Monte Carlo models with various implementations of color coherence. None of the models describe the data satisfactorily.

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Linn S, Markowitz P, Martinez G, Rodriguez JL, Adams T, Askew A, Bochenek J, Chen J, Diamond B, Gleyzer SV, Haas J, Hagopian S, Hagopian V, Johnson KF, Prosper H, Veeraraghavan V, Weinberg M, Baarmand MM, Dorney B, Hohlmann M, Kalakhety H, Yumiceva F, Adams MR, Apanasevich L, Bazterra VE, Betts RR, Bucinskaite I, Callner J, Cavanaugh R, Evdokimov O, Gauthier L, Gerber CE, Hofman DJ, Khalatyan S, Kurt P, Lacroix F, Moon DH, O’Brien C, Silkworth C, Strom D, Turner P, Varelas N, Akgun U, Albayrak EA, Bilki B, Clarida W, Dilsiz K, Duru F, Griffiths S, Merlo JP, Mermerkaya H, Mestvirishvili A, Moeller A, Nachtman J, Newsom CR, Ogul H, Onel Y, Ozok F, Sen S, Tan P, Tiras E, Wetzel J, Yetkin T, Yi K, Barnett BA, Blumenfeld B, Bolognesi S, Giurgiu G, Gritsan AV, Hu G, Maksimovic P, Martin C, Swartz M, Whitbeck A, Baringer P, Bean A, Benelli G, Kenny RP, Murray M, Noonan D, Sanders S, Stringer R, Wood JS, Barfuss AF, Chakaberia I, Ivanov A, Khalil S, Makouski M, Maravin Y, Shrestha S, Svintradze I, Gronberg J, Lange D, Rebassoo F, Wright D, Baden A, Calvert B, Eno SC, Gomez JA, Hadley NJ, Kellogg RG, Kolberg T, Lu Y, Marionneau M, Mignerey AC, Pedro K, Peterman A, Skuja A, Temple J, Tonjes MB, Tonwar SC, Apyan A, Bauer G, Busza W, Cali IA, Chan M, Di Matteo L, Dutta V, Gomez Ceballos G, Goncharov M, Gulhan D, Kim Y, Klute M, Lai YS, Levin A, Luckey PD, Ma T, Nahn S, Paus C, Ralph D, Roland C, Roland G, Stephans GSF, Stöckli F, Sumorok K, Velicanu D, Wolf R, Wyslouch B, Yang M, Yilmaz Y, Yoon AS, Zanetti M, Zhukova V, Dahmes B, De Benedetti A, Franzoni G, Gude A, Haupt J, Kao SC, Klapoetke K, Kubota Y, Mans J, Pastika N, Rusack R, Sasseville M, Singovsky A, Tambe N, Turkewitz J, Acosta JG, Cremaldi LM, Kroeger R, Oliveros S, Perera L, Rahmat R, Sanders DA, Summers D, Avdeeva E, Bloom K, Bose S, Claes DR, Dominguez A, Eads M, Suarez RG, Keller J, Kravchenko I, Lazo-Flores J, Malik S, Meier F, Snow GR, Dolen J, Godshalk A, Iashvili I, Jain S, Kharchilava A, Kumar A, Rappoccio S, Wan Z, Alverson G, Barberis E, Baumgartel D, Chasco M, Haley J, Massironi A, Nash D, Orimoto T, Trocino D, Wood D, Zhang J, Anastassov A, Hahn KA, Kubik A, Lusito L, Mucia N, Odell N, Pollack B, Pozdnyakov A, Schmitt M, Stoynev S, Sung K, Velasco M, Won S, Berry D, Brinkerhoff A, Chan KM, Hildreth M, Jessop C, Karmgard DJ, Kolb J, Lannon K, Luo W, Lynch S, Marinelli N, Morse DM, Pearson T, Planer M, Ruchti R, Slaunwhite J, Valls N, Wayne M, Wolf M, Antonelli L, Bylsma B, Durkin LS, Hill C, Hughes R, Kotov K, Ling TY, Puigh D, Rodenburg M, Smith G, Vuosalo C, Winer BL, Wolfe H, Berry E, Elmer P, Halyo V, Hebda P, Hegeman J, Hunt A, Jindal P, Koay SA, Lujan P, Marlow D, Medvedeva T, Mooney M, Olsen J, Piroué P, Quan X, Raval A, Saka H, Stickland D, Tully C, Werner JS, Zenz SC, Zuranski A, Brownson E, Lopez A, Mendez H, Ramirez Vargas JE, Alagoz E, Benedetti D, Bolla G, Bortoletto D, De Mattia M, Everett A, Hu Z, Jones M, Jung K, Koybasi O, Kress M, Leonardo N, Lopes Pegna D, Maroussov V, Merkel P, Miller DH, Neumeister N, Shipsey I, Silvers D, Svyatkovskiy A, Vidal Marono M, Wang F, Xie W, Xu L, Yoo HD, Zablocki J, Zheng Y, Guragain S, Parashar N, Adair A, Akgun B, Ecklund KM, Geurts FJM, Padley BP, Redjimi R, Roberts J, Zabel J, Betchart B, Bodek A, Covarelli R, de Barbaro P, Demina R, Eshaq Y, Ferbel T, Garcia-Bellido A, Goldenzweig P, Han J, Harel A, Miner DC, Petrillo G, Vishnevskiy D, Zielinski M, Bhatti A, Ciesielski R, Demortier L, Goulianos K, Lungu G, Malik S, Mesropian C, Arora S, Barker A, Chou JP, Contreras-Campana C, Contreras-Campana E, Duggan D, Ferencek D, Gershtein Y, Gray R, Halkiadakis E, Hidas D, Lath A, Panwalkar S, Park M, Patel R, Rekovic V, Robles J, Salur S, Schnetzer S, Seitz C, Somalwar S, Stone R, Thomas S, Thomassen P, Walker M, Cerizza G, Hollingsworth M, Rose K, Spanier S, Yang ZC, York A, Bouhali O, Eusebi R, Flanagan W, Gilmore J, Kamon T, Khotilovich V, Montalvo R, Osipenkov I, Pakhotin Y, Perloff A, Roe J, Safonov A, Sakuma T, Suarez I, Tatarinov A, Toback D, Akchurin N, Cowden C, Damgov J, Dragoiu C, Dudero PR, Jeong C, Kovitanggoon K, Lee SW, Libeiro T, Volobouev I, Appelt E, Delannoy AG, Greene S, Gurrola A, Johns W, Maguire C, Melo A, Sharma M, Sheldon P, Snook B, Tuo S, Velkovska J, Arenton MW, Boutle S, Cox B, Francis B, Goodell J, Hirosky R, Ledovskoy A, Lin C, Neu C, Wood J, Gollapinni S, Harr R, Karchin PE, Don CKK, Lamichhane P, Sakharov A, Belknap DA, Borrello L, Carlsmith D, Cepeda M, Dasu S, Friis E, Grothe M, Hall-Wilton R, Herndon M, Hervé A, Klabbers P, Klukas J, Lanaro A, Loveless R, Mohapatra A, Mozer MU, Ojalvo I, Pierro GA, Polese G, Ross I, Savin A, Smith WH, Swanson J. Study of the production of charged pions, kaons, and protons in pPb collisions at [Formula: see text]5.02[Formula: see text]

Spectra of identified charged hadrons are measured in pPb collisions with the CMS detector at the LHC at [Formula: see text]. Charged pions, kaons, and protons in the transverse-momentum range [Formula: see text]-1.7[Formula: see text] and laboratory rapidity [Formula: see text] are identified via their energy loss in the silicon tracker. The average [Formula: see text] increases with particle mass and the charged multiplicity of the event. The increase of the average [Formula: see text] with charged multiplicity is greater for heavier hadrons. Comparisons to Monte Carlo event generators reveal that Epos Lhc, which incorporates additional hydrodynamic evolution of the created system, is able to reproduce most of the data features, unlike Hijing and Ampt. The [Formula: see text] spectra and integrated yields are also compared to those measured in pp and PbPb collisions at various energies. The average transverse momentum and particle ratio measurements indicate that particle production at LHC energies is strongly correlated with event particle multiplicity.

Measurement of inclusive W and Z boson production cross sections in pp collisions at sqrt[s] = 8 TeV

A measurement of total and fiducial inclusive W and Z boson production cross sections in pp collisions at sqrt[s] = 8 TeV is presented. Electron and muon final states are analyzed in a data sample collected with the CMS detector corresponding to an integrated luminosity of 18.2 ± 0.5 pb(-1). The measured total inclusive cross sections times branching fractions are σ(pp → WX)×B(W → ℓν) = 12.21 ± 0.03(stat) ± 0.24(syst) ± 0.32(lum) nb and σ(pp → ZX) × B(Z → ℓ+ℓ-) = 1.15 ± 0.01(stat) ± 0.02(syst) ± 0.03(lum) nb for the dilepton mass in the range of 60-120 GeV. The measured values agree with next-to-next-to-leading-order QCD cross section calculations. Ratios of cross sections are reported with a precision of 2%. This is the first measurement of inclusive W and Z boson production in proton-proton collisions at sqrt[s] = 8 TeV.

Measurements of tt spin correlations and top-quark polarization using dilepton final states in pp collisions at sqrt[s]=7 TeV

Spin correlations and polarization in the top quark-antiquark system are measured using dilepton final states produced in pp collisions at the LHC at sqrt[s]=7  TeV. The data correspond to an integrated luminosity of 5.0  fb(-1) collected with the CMS detector. The measurements are performed using events with two oppositely charged leptons (electrons or muons), a significant imbalance in transverse momentum, and two or more jets, where at least one of the jets is identified as originating from a b quark. The spin correlations and polarization are measured through asymmetries in angular distributions of the two selected leptons, unfolded to the parton level. All measurements are found to be in agreement with predictions of the standard model.

Search for top-quark partners with charge 5/3 in the same-sign dilepton final state

A search for the production of heavy partners of the top quark with charge 5/3 is performed in events with a pair of same-sign leptons. The data sample corresponds to an integrated luminosity of 19.5 fb(-1) and was collected at sqrt[s] = 8 TeV by the CMS experiment. No significant excess is observed in the data above the expected background, and the existence of top-quark partners with masses below 800 GeV is excluded at a 95% confidence level, assuming they decay exclusively to tW. This is the first limit on these particles from the LHC, and it is significantly more restrictive than previous limits.

Search for flavor-changing neutral currents in top-quark decays t → Zq in pp collisions at sqrt[s] = 8 TeV

A search for flavor-changing neutral currents in top-quark decays t → Zq is performed in events produced from the decay chain tt → Zq+Wb, where both vector bosons decay leptonically, producing a final state with three leptons (electrons or muons). A data set collected with the CMS detector at the LHC is used, corresponding to an integrated luminosity of 19.7 fb(-1) of proton-proton collisions at a center-of-mass energy of 8 TeV. No excess is seen in the observed number of events relative to the standard model prediction; thus, no evidence for flavor-changing neutral currents in top-quark decays is found. A combination with a previous search at 7 TeV excludes a t → Zq branching fraction greater than 0.05% at the 95% confidence level.

Search for top squark and Higgsino production using diphoton Higgs boson decays

Results are presented of a search for a "natural" supersymmetry scenario with gauge mediated symmetry breaking. It is assumed that only the supersymmetric partners of the top quark (the top squark) and the Higgs boson (Higgsino) are accessible. Events are examined in which there are two photons forming a Higgs boson candidate, and at least two b-quark jets. In 19.7  fb-1 of proton-proton collision data at s=8  TeV, recorded in the CMS experiment, no evidence of a signal is found and lower limits at the 95% confidence level are set, excluding the top squark mass below 360 to 410 GeV, depending on the Higgsino mass.

John J, Sulak L, Alimena J, Bhattacharya S, Christopher G, Cutts D, Demiragli Z, Ferapontov A, Garabedian A, Heintz U, Jabeen S, Kukartsev G, Laird E, Landsberg G, Luk M, Narain M, Segala M, Sinthuprasith T, Speer T, Breedon R, Breto G, Calderon De La Barca Sanchez M, Chauhan S, Chertok M, Conway J, Conway R, Cox PT, Erbacher R, Gardner M, Houtz R, Ko W, Kopecky A, Lander R, Mall O, Miceli T, Nelson R, Pellett D, Ricci-Tam F, Rutherford B, Searle M, Smith J, Squires M, Tripathi M, Wilbur S, Yohay R, Andreev V, Cline D, Cousins R, Erhan S, Everaerts P, Farrell C, Felcini M, Hauser J, Ignatenko M, Jarvis C, Rakness G, Schlein P, Takasugi E, Traczyk P, Valuev V, Weber M, Babb J, Clare R, Dinardo ME, Ellison J, Gary JW, Hanson G, Liu H, Long OR, Luthra A, Nguyen H, Paramesvaran S, Sturdy J, Sumowidagdo S, Wilken R, Wimpenny S, Andrews W, Branson JG, Cerati GB, Cittolin S, Evans D, Holzner A, Kelley R, Lebourgeois M, Letts J, Macneill I, Mangano B, Padhi S, Palmer C, Petrucciani G, Pieri M, Sani M, Sharma V, Simon S, Sudano E, Tadel M, Tu Y, Vartak A, Wasserbaech S, Würthwein F, Yagil A, Yoo J, Barge D, Bellan R, Campagnari C, D’Alfonso M, Danielson T, Flowers K, Geffert P, George C, Golf F, Incandela J, Justus C, Kalavase P, Kovalskyi D, Krutelyov V, Lowette S, naVillalba RM, Mccoll N, Pavlunin V, Ribnik J, Richman J, Rossin R, Stuart D, To W, West C, Apresyan A, Bornheim A, Bunn J, Chen Y, Di Marco E, Duarte J, Kcira D, Ma Y, Mott A, Newman HB, Rogan C, Spiropulu M, Timciuc V, Veverka J, Wilkinson R, Xie S, Yang Y, Zhu RY, Azzolini V, Calamba A, Carroll R, Ferguson T, Iiyama Y, Jang DW, Liu YF, Paulini M, Russ J, Vogel H, Vorobiev I, Cumalat JP, Drell BR, Ford WT, Gaz A, Luiggi Lopez E, Nauenberg U, Smith JG, Stenson K, Ulmer KA, Wagner SR, Alexander J, Chatterjee A, Eggert N, Gibbons LK, Hopkins W, Khukhunaishvili A, Kreis B, Mirman N, Nicolas Kaufman G, Patterson JR, Ryd A, Salvati E, Sun W, Teo WD, Thom J, Thompson J, Tucker J, Weng Y, Winstrom L, Wittich P, Winn D, Abdullin S, Albrow M, Anderson J, Apollinari G, Bauerdick LAT, Beretvas A, Berryhill J, Bhat PC, Burkett K, Butler JN, Chetluru V, Cheung HWK, Chlebana F, Cihangir S, Elvira VD, Fisk I, Freeman J, Gao Y, Gottschalk E, Gray L, Green D, Gutsche O, Hare D, Harris RM, Hirschauer J, Hooberman B, Jindariani S, Johnson M, Joshi U, Klima B, Kunori S, Kwan S, Leonidopoulos C, Linacre J, Lincoln D, Lipton R, Lykken J, Maeshima K, Marraffino JM, Martinez Outschoorn VI, Maruyama S, Mason D, McBride P, Mishra K, Mrenna S, Musienko Y, Newman-Holmes C, O’Dell V, Prokofyev O, Ratnikova N, Sexton-Kennedy E, Sharma S, Spalding WJ, Spiegel L, Taylor L, Tkaczyk S, Tran NV, Uplegger L, Vaandering EW, Vidal R, Whitmore J, Wu W, Yang F, Yun JC, Acosta D, Avery P, Bourilkov D, Chen M, Cheng T, Das S, De Gruttola M, Di Giovanni GP, Dobur D, Drozdetskiy A, Field RD, Fisher M, Fu Y, Furic IK, Hugon J, Kim B, Konigsberg J, Korytov A, Kropivnitskaya A, Kypreos T, Low JF, Matchev K, Milenovic P, Mitselmakher G, Muniz L, Remington R, Rinkevicius A, Skhirtladze N, Snowball M, Yelton J, Zakaria M, Gaultney V, Hewamanage S, Lebolo LM, Linn S, Markowitz P, Martinez G, Rodriguez JL, Adams T, Askew A, Bochenek J, Chen J, Diamond B, Gleyzer SV, Haas J, Hagopian S, Hagopian V, Johnson KF, Prosper H, Veeraraghavan V, Weinberg M, Baarmand MM, Dorney B, Hohlmann M, Kalakhety H, Yumiceva F, Adams MR, Apanasevich L, Bazterra VE, Betts RR, Bucinskaite I, Callner J, Cavanaugh R, Evdokimov O, Gauthier L, Gerber CE, Hofman DJ, Khalatyan S, Kurt P, Lacroix F, Moon DH, O’Brien C, Silkworth C, Strom D, Turner P, Varelas N, Akgun U, Albayrak EA, Bilki B, Clarida W, Dilsiz K, Duru F, Griffiths S, Merlo JP, Mermerkaya H, Mestvirishvili A, Moeller A, Nachtman J, Newsom CR, Ogul H, Onel Y, Ozok F, Sen S, Tan P, Tiras E, Wetzel J, Yetkin T, Yi K, Barnett BA, Blumenfeld B, Bolognesi S, Fehling D, Giurgiu G, Gritsan AV, Guo ZJ, Hu G, Maksimovic P, Swartz M, Whitbeck A, Baringer P, Bean A, Benelli G, Kenny III RP, Murray M, Noonan D, Sanders S, Stringer R, Wood JS, Barfuss AF, Chakaberia I, Ivanov A, Khalil S, Makouski M, Maravin Y, Shrestha S, Svintradze I, Gronberg J, Lange D, Rebassoo F, Wright D, Baden A, Calvert B, Eno SC, Gomez JA, Hadley NJ, Kellogg RG, Kolberg T, Lu Y, Marionneau M, Mignerey AC, Pedro K, Peterman A, Skuja A, Temple J, Tonjes MB, Tonwar SC, Apyan A, Bauer G, Busza W, Butz E, Cali IA, Chan M, Dutta V, Gomez Ceballos G, Goncharov M, Kim Y, Klute M, Lai YS, Levin A, Luckey PD, Ma T, Nahn S, Paus C, Ralph D, Roland C, Roland G, Stephans GSF, Stöckli F, Sumorok K, Sung K, Velicanu D, Wolf R, Wyslouch B, Yang M, Yilmaz Y, Yoon AS, Zanetti M, Zhukova V, Dahmes B, De Benedetti A, Franzoni G, Gude A, Haupt J, Kao SC, Klapoetke K, Kubota Y, Mans J, Pastika N, Rusack R, Sasseville M, Singovsky A, Tambe N, Turkewitz J, Cremaldi LM, Kroeger R, Perera L, Rahmat R, Sanders DA, Summers D, Avdeeva E, Bloom K, Bose S, Claes DR, Dominguez A, Eads M, Gonzalez Suarez R, Keller J, Kravchenko I, Lazo-Flores J, Malik S, Meier F, Snow GR, Dolen J, Godshalk A, Iashvili I, Jain S, Kharchilava A, Kumar A, Rappoccio S, Wan Z, Alverson G, Barberis E, Baumgartel D, Chasco M, Haley J, Massironi A, Nash D, Orimoto T, Trocino D, Wood D, Zhang J, Anastassov A, Hahn KA, Kubik A, Lusito L, Mucia N, Odell N, Pollack B, Pozdnyakov A, Schmitt M, Stoynev S, Velasco M, Won S, Berry D, Brinkerhoff A, Chan KM, Hildreth M, Jessop C, Karmgard DJ, Kolb J, Lannon K, Luo W, Lynch S, Marinelli N, Morse DM, Pearson T, Planer M, Ruchti R, Slaunwhite J, Valls N, Wayne M, Wolf M, Antonelli L, Bylsma B, Durkin LS, Hill C, Hughes R, Kotov K, Ling TY, Puigh D, Rodenburg M, Smith G, Vuosalo C, Williams G, Winer BL, Wolfe H, Berry E, Elmer P, Halyo V, Hebda P, Hegeman J, Hunt A, Jindal P, Koay SA, Lopes Pegna D, Lujan P, Marlow D, Medvedeva T, Mooney M, Olsen J, Piroué P, Quan X, Raval A, Saka H, Stickland D, Tully C, Werner JS, Zenz SC, Zuranski A, Brownson E, Lopez A, Mendez H, Ramirez Vargas JE, Alagoz E, Benedetti D, Bolla G, Bortoletto D, De Mattia M, Everett A, Hu Z, Jones M, Jung K, Koybasi O, Kress M, Leonardo N, Maroussov V, Merkel P, Miller DH, Neumeister N, Shipsey I, Silvers D, Svyatkovskiy A, Vidal Marono M, Wang F, Xu L, Yoo HD, Zablocki J, Zheng Y, Guragain S, Parashar N, Adair A, Akgun B, Ecklund KM, Geurts FJM, Li W, Padley BP, Redjimi R, Roberts J, Zabel J, Betchart B, Bodek A, Covarelli R, De Barbaro P, Demina R, Eshaq Y, Ferbel T, Garcia-Bellido A, Goldenzweig P, Han J, Harel A, Miner DC, Petrillo G, Vishnevskiy D, Zielinski M, Bhatti A, Ciesielski R, Demortier L, Goulianos K, Lungu G, Malik S, Mesropian C, Arora S, Barker A, Chou JP, Contreras-Campana C, Contreras-Campana E, Duggan D, Ferencek D, Gershtein Y, Gray R, Halkiadakis E, Hidas D, Lath A, Panwalkar S, Park M, Patel R, Rekovic V, Robles J, Rose K, Salur S, Schnetzer S, Seitz C, Somalwar S, Stone R, Thomas S, Walker M, Cerizza G, Hollingsworth M, Spanier S, Yang ZC, York A, Bouhali O, Eusebi R, Flanagan W, Gilmore J, Kamon T, Khotilovich V, Montalvo R, Osipenkov I, Pakhotin Y, Perloff A, Roe J, Safonov A, Sakuma T, Suarez I, Tatarinov A, Toback D, Akchurin N, Damgov J, Dragoiu C, Dudero PR, Jeong C, Kovitanggoon K, Lee SW, Libeiro T, Volobouev I, Appelt E, Delannoy AG, Greene S, Gurrola A, Johns W, Maguire C, Mao Y, Melo A, Sharma M, Sheldon P, Snook B, Tuo S, Velkovska J, Arenton MW, Boutle S, Cox B, Francis B, Goodell J, Hirosky R, Ledovskoy A, Lin C, Neu C, Wood J, Gollapinni S, Harr R, Karchin PE, Kottachchi Kankanamge Don C, Lamichhane P, Sakharov A, Anderson M, Belknap DA, Borrello L, Carlsmith D, Cepeda M, Dasu S, Friis E, Grogg KS, Grothe M, Hall-Wilton R, Herndon M, Hervé A, Kaadze K, Klabbers P, Klukas J, Lanaro A, Lazaridis C, Loveless R, Mohapatra A, Mozer MU, Ojalvo I, Pierro GA, Ross I, Savin A, Smith WH, Swanson J. Measurement of the top-quark mass in all-jets [Formula: see text] events in pp collisions at [Formula: see text] TeV

The mass of the top quark is measured using a sample of [Formula: see text] candidate events with at least six jets in the final state. The sample is selected from data collected with the CMS detector in pp collisions at [Formula: see text] TeV in 2011 and corresponds to an integrated luminosity of 3.54 [Formula: see text]. The mass is reconstructed for each event employing a kinematic fit of the jets to a [Formula: see text] hypothesis. The top-quark mass is measured to be [Formula: see text] GeV. A combination with previously published measurements in other decay modes by CMS yields a mass of [Formula: see text] GeV.

Dual energy CT myelography after lumbar osteosynthesis

PURPOSE

The purpose of this study was to evaluate the benefits of CT myelography in the DE technique in patients with lumbar osteosynthesis.

MATERIALS AND METHODS

In 30 patients a DE-CT scan of the spine with tube voltages of 80 kV and 140 kV was performed and a virtual monochromatic series of 120 kV was generated after intrathecal contrast injection. The impact of metal artifacts on the spinal canal and the spinal foramina was evaluated. The visualization of nerve roots was compared between a VRT series of the dural sac and conventional myelography.

RESULTS

With tube voltages of 140 kV, the artifacts were least pronounced. As no overlay disturbance was present, VRT visualization of the nerve roots was more reliable than conventional myelography.

CONCLUSION

In patients after osteosynthesis, CT in the DE technique provides minimal artifact disturbance using a tube voltage of 140 kV. "Virtual myelography" seems to be superior to conventional myelography for the evaluation of nerve roots. This could reduce additional conventional radiography, may shorten the entire examination and radiation time and diminish unnecessary painful movements for the patient.

Jet and underlying event properties as a function of charged-particle multiplicity in proton-proton collisions at [Formula: see text]

Characteristics of multi-particle production in proton-proton collisions at [Formula: see text] are studied as a function of the charged-particle multiplicity, Nch. The produced particles are separated into two classes: those belonging to jets and those belonging to the underlying event. Charged particles are measured with pseudorapidity |η|<2.4 and transverse momentum pT>0.25 GeV/c. Jets are reconstructed from charged-particles only and required to have pT>5 GeV/c. The distributions of jet pT, average pT of charged particles belonging to the underlying event or to jets, jet rates, and jet shapes are presented as functions of Nch and compared to the predictions of the pythia and herwig event generators. Predictions without multi-parton interactions fail completely to describe the Nch-dependence observed in the data. For increasing Nch, pythia systematically predicts higher jet rates and harder pT spectra than seen in the data, whereas herwig shows the opposite trends. At the highest multiplicity, the data-model agreement is worse for most observables, indicating the need for further tuning and/or new model ingredients.

Search for top squarks in R-parity-violating supersymmetry using three or more leptons and b-tagged jets

A search for anomalous production of events with three or more isolated leptons and bottom-quark jets produced in pp collisions at √s=8 TeV is presented. The analysis is based on a data sample corresponding to an integrated luminosity of 19.5 fb(-1) collected by the CMS experiment at the LHC in 2012. No excess above the standard model expectations is observed. The results are interpreted in the context of supersymmetric models with signatures that have low missing transverse energy arising from light top-squark pair production with R-parity-violating decays of the lightest supersymmetric particle. In two models with different R-parity-violating couplings, top squarks are excluded below masses of 1020 GeV and 820 GeV when the lightest supersymmetric particle has a mass of 200 GeV.

Searches for new physics using the tt¯ invariant mass distribution in pp collisions at √s=8 TeV

Searches for anomalous top quark-antiquark production are presented, based on pp collisions at √s=8 TeV. The data, corresponding to an integrated luminosity of 19.7 fb(-1), were collected with the CMS detector at the LHC. The observed tt¯ invariant mass spectrum is found to be compatible with the standard model prediction. Limits on the production cross section times branching fraction probe, for the first time, a region of parameter space for certain models of new physics not yet constrained by precision measurements.

Bayesian Approach for Inconsistent Information

In engineering situations, we usually have a large amount of prior knowledge that needs to be taken into account when processing data. Traditionally, the Bayesian approach is used to process data in the presence of prior knowledge. Sometimes, when we apply the traditional Bayesian techniques to engineering data, we get inconsistencies between the data and prior knowledge. These inconsistencies are usually caused by the fact that in the traditional approach, we assume that we know the exact sample values, that the prior distribution is exactly known, etc. In reality, the data is imprecise due to measurement errors, the prior knowledge is only approximately known, etc. So, a natural way to deal with the seemingly inconsistent information is to take this imprecision into account in the Bayesian approach - e.g., by using fuzzy techniques. In this paper, we describe several possible scenarios for fuzzifying the Bayesian approach. Particular attention is paid to the interaction between the estimated imprecise parameters. In this paper, to implement the corresponding fuzzy versions of the Bayesian formulas, we use straightforward computations of the related expression - which makes our computations reasonably time-consuming. Computations in the traditional (non-fuzzy) Bayesian approach are much faster - because they use algorithmically efficient reformulations of the Bayesian formulas. We expect that similar reformulations of the fuzzy Bayesian formulas will also drastically decrease the computation time and thus, enhance the practical use of the proposed methods.

Search for supersymmetry in hadronic final states with missing transverse energy using the variables αT and b-quark multiplicity in pp collisions at [Formula: see text]

An inclusive search for supersymmetric processes that produce final states with jets and missing transverse energy is performed in pp collisions at a centre-of-mass energy of 8 TeV. The data sample corresponds to an integrated luminosity of 11.7 fb-1 collected by the CMS experiment at the LHC. In this search, a dimensionless kinematic variable, αT, is used to discriminate between events with genuine and misreconstructed missing transverse energy. The search is based on an examination of the number of reconstructed jets per event, the scalar sum of transverse energies of these jets, and the number of these jets identified as originating from bottom quarks. No significant excess of events over the standard model expectation is found. Exclusion limits are set in the parameter space of simplified models, with a special emphasis on both compressed-spectrum scenarios and direct or gluino-induced production of third-generation squarks. For the case of gluino-mediated squark production, gluino masses up to 950-1125 GeV are excluded depending on the assumed model. For the direct pair-production of squarks, masses up to 450 GeV are excluded for a single light first- or second-generation squark, increasing to 600 GeV for bottom squarks.

Measurement of the Bs(0)→μ+ μ- branching fraction and search for B(0)→μ+ μ- with the CMS experiment

Results are presented from a search for the rare decays Bs(0)→μ+ μ- and B(0)→μ+ μ- in pp collisions at sqrt[s]=7 and 8 TeV, with data samples corresponding to integrated luminosities of 5 and 20  fb(-1), respectively, collected by the CMS experiment at the LHC. An unbinned maximum-likelihood fit to the dimuon invariant mass distribution gives a branching fraction B(Bs(0)→μ+ μ-)=(3.0(-0.9)(+1.0))×10(-9), where the uncertainty includes both statistical and systematic contributions. An excess of Bs(0)→μ+ μ- events with respect to background is observed with a significance of 4.3 standard deviations. For the decay B(0)→μ+ μ- an upper limit of B(B(0)→μ+ μ-)<1.1×10(-9) at the 95% confidence level is determined. Both results are in agreement with the expectations from the standard model.

Inclusive search for supersymmetry using razor variables in pp collisions at √s=7 TeV

An inclusive search is presented for new heavy particle pairs produced in √s=7 TeV proton-proton collisions at the LHC using 4.7±0.1 fb(-1) of integrated luminosity. The selected events are analyzed in the 2D razor space of M(R), an event-by-event indicator of the heavy particle mass scale, and R, a dimensionless variable related to the missing transverse energy. The third-generation sector is probed using the event heavy-flavor content. The search is sensitive to generic supersymmetry models with minimal assumptions about the superpartner decay chains. No excess is observed in the number of events beyond that predicted by the standard model. Exclusion limits are derived in the CMSSM framework as well as for simplified models. Within the CMSSM parameter space considered, gluino masses up to 800 GeV and squark masses up to 1.35 TeV are excluded at 95% confidence level depending on the model parameters. The direct production of pairs of top or bottom squarks is excluded for masses as high as 400 GeV.

Search for physics beyond the standard model in events with τ leptons, jets, and large transverse momentum imbalance in pp collisions at [Formula: see text]

A search for physics beyond the standard model is performed with events having one or more hadronically decaying τ leptons, highly energetic jets, and large transverse momentum imbalance. The data sample corresponds to an integrated luminosity of 4.98 fb-1 of proton-proton collisions at [Formula: see text] collected with the CMS detector at the LHC in 2011. The number of observed events is consistent with predictions for standard model processes. Lower limits on the mass of the gluino in supersymmetric models are determined.

Measurement of masses in the [Formula: see text] system by kinematic endpoints in pp collisions at [Formula: see text]

A simultaneous measurement of the top-quark, W-boson, and neutrino masses is reported for [Formula: see text] events selected in the dilepton final state from a data sample corresponding to an integrated luminosity of 5.0 fb-1 collected by the CMS experiment in pp collisions at [Formula: see text]. The analysis is based on endpoint determinations in kinematic distributions. When the neutrino and W-boson masses are constrained to their world-average values, a top-quark mass value of [Formula: see text] is obtained. When such constraints are not used, the three particle masses are obtained in a simultaneous fit. In this unconstrained mode the study serves as a test of mass determination methods that may be used in beyond standard model physics scenarios where several masses in a decay chain may be unknown and undetected particles lead to underconstrained kinematics.