343 research outputs found
Search for excited electrons and muons in √s=8 TeV proton–proton collisions with the ATLAS detector
No full textThe ATLAS detector at the Large Hadron Collider is used to search for excited electrons and excited muons in the channel pp → ℓℓ* → ℓℓγ, assuming that excited leptons are produced via contact interactions. The analysis is based on 13 fb[superscript −1] of pp collisions at a centre-of-mass energy of 8 TeV. No evidence for excited leptons is found, and a limit is set at the 95% credibility level on the cross section times branching ratio as a function of the excited-lepton mass m[subscript ℓ*]. For m[subscript ℓ*] ≥ 0.8 TeV, the respective upper limits on σB(ℓ* → ℓγ) are 0.75 and 0.90 fb for the e* and μ* searches. Limits on σB are converted into lower bounds on the compositeness scale Λ. In the special case where Λ = m[subscript ℓ*], excited-electron and excited-muon masses below 2.2 TeV are excluded.United States. Dept. of EnergyNational Science Foundation (U.S.)Brookhaven National Laborator
Measurement of the inclusive isolated prompt photon cross section in pp collisions at √s = 7 TeV with the ATLAS detector
No full text"The inclusive and dijet production cross-sections have been measured for jets containing b-hadrons (b-jets) in proton-proton collisions at a centre-of-mass energy of root s = 7 TeV, using the ATLAS detector at the LHC. The measurements use data corresponding to an integrated luminosity of 34 pb(-1). The b-jets are identified using either a lifetime-based method, where secondary decay vertices of b-hadrons in jets are reconstructed using information from the tracking detectors, or a muon-based method where the presence of a muon is used to identify semileptonic decays of b-hadrons inside jets. The inclusive b-jet cross-section is measured as a function of transverse momentum in the range 20 -dijet cross-section is measured as a function of the dijet invariant mass in the range 110 < m(jj) < 760 GeV, the azimuthal angle difference between the two jets and the angular variable chi in two dijet mass regions. The results are compared with next-to-leading-order QCD predictions. Good agreement is observed between the measured cross-sections and the predictions obtained using POWHEG + Pythia. MC@NLO + Herwig shows good agreement with the measured b (b) over bar -dijet cross-section. However, it does not reproduce the measured inclusive cross-section well, particularly for central b-jets with large transverse momenta. RI Gutierrez, Phillip\/C-1161-2011; Ferrando, James\/A-9192-2012; collins-tooth, christopher\/A-9201-2012; Perrino, Roberto\/B-4633-2010; Laurelli, Paolo\/B-1432-2012; De Cecco, Sandro\/B-1016-2012; Stoicea, Gabriel\/B-6717-2011; branchini, paolo\/A-4857-2011; Wolter, Marcin\/A-7412-2012; Rotaru, Marina\/A-3097-2011; O'Shea, Val\/G-1279-2010; Doyle, Anthony\/C-5889-2009; Buttar, Craig\/D-3706-2011; Pina, Joao \/C-4391-2012; Takai, Helio\/C-3301-2012; St.Denis, Richard\/C-8997-2012; Jones, Roger\/H-5578-2011; Britton, David\/F-2602-2010; Li, Xuefei\/C-3861-2012; Fazio, Salvatore \/G-5156-2010; Smirnova, Lidia\/D-8089-2012; Smirnov, Sergei\/F-1014-2011; Gladilin, Leonid\/B-5226-2011; Barreiro, Fernando\/D-9808-2012; Kramarenko, Victor\/E-1781-2012; Prokoshin, Fedor\/E-2795-2012; Alexa, Calin\/F-6345-2010; Pacheco Pages, Andres\/C-5353-2011; Moorhead, Gareth\/B-6634-2009; Livan, Michele\/D-7531-2012; Petrucci, Fabrizio\/G-8348-2012; Wemans, Andre\/A-6738-2012; Fabbri, Laura\/H-3442-2012; Kurashige, Hisaya\/H-4916-2012; Villa, Mauro\/C-9883-2009; Kuzhir, Polina\/H-8653-2012; Delmastro, Marco\/I-5599-2012
Measurement of the inelastic proton–proton cross-section at √s=7 TeV with the ATLAS Detector
No full textA first measurement of the inelastic cross-section is presented for proton-proton collisions at a center of mass energy √ =7 TeV using the ATLAS detector at the Large Hadron Collider. In a dataset corresponding to an integrated luminosity of 20 µb<sup>-1</sup>, events are selected by requiring hits on scintillation counters mounted in the forward region of the detector. An inelastic cross-section of 60.3 ± 2.1 mb is measured for ξ>5x10<sup>-6</sup>, where ξ=M<sup>2</sup><sub>X</sub>/s is calculated from the invariant mass, M<sub>X</sub>, of hadrons selected using the largest rapidity gap in the event. For diffractive events this corresponds to requiring at least one of the dissociation masses to be larger than 15.7 GeV
Constraints on oscillation parameters from appearance and disappearance in NOvA
No full textClick on the DOI link to access the article (may not be free). WSU authors: Meyer, H.; Muether, M.; Solomey, N. The complete list includes: P. Adamson, L. Aliaga, D. Ambrose, N. Anfimov, A. Antoshkin, E. Arrieta-Diaz, K. Augsten, A. Aurisano, C. Backhouse, M. Baird, B. A. Bambah, K. Bays, B. Behera, S. Bending, R. Bernstein, V. Bhatnagar, B. Bhuyan, J. Bian, T. Blackburn, A. Bolshakova, C. Bromberg, J. Brown, G. Brunetti, N. Buchanan, A. Butkevich, V. Bychkov, M. Campbell, E. Catano-Mur, S. Childress, B. C. Choudhary, B. Chowdhury, T. E. Coan, J. A. B. Coelho, M. Colo, J. Cooper, L. Corwin, L. Cremonesi, D. Cronin-Hennessy, G. S. Davies, J. P. Davies, P. F. Derwent, R. Dharmapalan, P. Ding, Z. Djurcic, E. C. Dukes, H. Duyang, S. Edayath, R. Ehrlich, G. J. Feldman, M. J. Frank, M. Gabrielyan, H. R. Gallagher, S. Germani, T. Ghosh, A. Giri, R. A. Gomes, M. C. Goodman, V. Grichine, R. Group, D. Grover, B. Guo, A. Habig, J. Hartnell, R. Hatcher, A. Hatzikoutelis, K. Heller, A. Himmel, A. Holin, J. Hylen, F. Jediny, M. Judah, G. K. Kafka, D. Kalra, S. M. S. Kasahara, S. Kasetti, R. Keloth, L. Kolupaeva, S. Kotelnikov, I. Kourbanis, A. Kreymer, A. Kumar, S. Kurbanov, K. Lang, W. M. Lee, S. Lin, J. Liu, M. Lokajicek, J. Lozier, S. Luchuk, K. Maan, S. Magill, W. A. Mann, M. L. Marshak, K. Matera, V. Matveev, D. P. Méndez, M. D. Messier, H. Meyer, T. Miao, W. H. Miller, S. R. Mishra, R. Mohanta, A. Moren, L. Mualem, M. Muether, S. Mufson, R. Murphy, J. Musser, J. K. Nelson, R. Nichol, E. Niner, A. Norman, T. Nosek, Y. Oksuzian, A. Olshevskiy, T. Olson, J. Paley, P. Pandey, R. B. Patterson, G. Pawloski, D. Pershey, O. Petrova, R. Petti, S. Phan-Budd, R. K. Plunkett, R. Poling, B. Potukuchi, C. Principato, F. Psihas, A. Radovic, R. A. Rameika, B. Rebel, B. Reed, D. Rocco, P. Rojas, V. Ryabov, K. Sachdev, P. Sail, O. Samoylov, M. C. Sanchez, R. Schroeter, J. Sepulveda-Quiroz, P. Shanahan, A. Sheshukov, J. Singh, J. Singh, P. Singh, V. Singh, J. Smolik, N. Solomey, E. Song, A. Sousa, K. Soustruznik, M. Strait, L. Suter, R. L. Talaga, M. C. Tamsett, P. Tas, R. B. Thayyullathil, J. Thomas, X. Tian, S. C. Tognini, J. Tripathi, A. Tsaris, J. Urheim, P. Vahle, J. Vasel, L. Vinton, A. Vold, T. Vrba, B. Wang, M. Wetstein, D. Whittington, S. G. Wojcicki, J. Wolcott, N. Yadav, S. Yang, J. Zalesak, B. Zamorano, and R. Zwaska.Preprint is available in SOAR.Results are reported from an improved measurement of transitions by the NOvA experiment. Using an exposure equivalent to protons-on-target 33 candidates were observed with a background of 8.2±0.8 (syst.). Combined with the latest NOvA disappearance data and external constraints from reactor experiments on the hypothesis of inverted mass hierarchy with , in the lower octant is disfavored at greater than C.L. for all values of .U.S. Department of Energy; the U.S. National Science Foundation; the Department of Science and Technology, India; the European Research Council; the MSMT CR, GA UK, Czech Republic; the RAS, RMES, and RFBR, Russia; CNPq and FAPEG, Brazil; and the State and University of Minnesota. We are grateful for the contributions of the staffs at the University of Minnesota module assembly facility and Ash River Laboratory, Argonne National Laboratory, and Fermilab. Fermilab is operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the U.S. DOE
Search for resonances decaying into top-quark pairs using fully hadronic decays in pp collisions with ATLAS at root s=7 TeV
No full textContains fulltext :
111244.pdf (Publisher’s version ) (Open Access
Search for top quark decays t → qH with H → γγ using the ATLAS detector
No full textA search is performed for flavour-changing neutral currents in the decay of a top quark to an up-type (c, u) quark and a Higgs boson, where the Higgs boson decays to two photons. The proton-proton collision data set used corresponds to 4.7 fb-1 at √ = 7TeV and 20.3fb-1 at √ = 8TeV collected by the ATLAS experiment at the LHC. Top quark pair events are searched for in which one top quark decays to qH and the other decays to bW. Both the hadronic and the leptonic decay modes of the W boson are used. No significant signal is observed and an upper limit is set on the t → qH branching ratio of 0.79 at the 95% confidence level. The corresponding limit on the tqH coupling combination λtcH 2 + λtuH 2 is 0.17
The SU(3)-invariant sector of new maximal supergravity
No full textWe investigate the SU(3)-invariant sector of the one-parameter family of SO(8) gauged maximal supergravities that has been recently discovered. To this end, we construct the N = 2 truncation of this theory and analyse its full vacuum structure. The number of critical point is doubled and includes new N = 0 and N = 1 branches. We numerically exhibit the parameter dependence of the location and cosmological constant of all extrema. Moreover, we provide their analytic expressions for cases of special interest. Finally, while the mass spectra are found to be parameter independent in most cases, we show that the novel non-supersymmetric branch with SU(3) invariance provides the first counterexample to this.
Performance of jet substructure techniques for large-R jets in proton-proton collisions at root s=7 TeV using the ATLAS detector
No full textThis paper presents the application of a variety of techniques to study jet substructure. The performance of various modified jet algorithms, or jet grooming techniques, for several jet types and event topologies is investigated for jets with transverse momentum larger than 300 GeV. Properties of jets subjected to the mass-drop filtering, trimming, and pruning algorithms are found to have a reduced sensitivity to multiple proton-proton interactions, are more stable at high luminosity and improve the physics potential of searches for heavy boosted objects. Studies of the expected discrimination power of jet mass and jet substructure observables in searches for new physics are also presented. Event samples enriched in boosted W and Z bosons and top-quark pairs are used to study both the individual jet invariant mass scales and the efficacy of algorithms to tag boosted hadronic objects. The analyses presented use the full 2011 ATLAS dataset, corresponding to an integrated luminosity of 4.7 +/- 0.1 fb(-1) from proton-proton collisions produced by the Large Hadron Collider at a centre-of-mass energy of root s = 7 TeV
Search for a heavy top-quark partner in final states with two leptons with the ATLAS detector at the LHC
No full textContains fulltext :
103720.pdf (Publisher’s version ) (Open Access
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