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Measurement of the polarization of w bosons with large transverse momenta in W+jets events at the LHC

Physical Review Letters 107:2 (2011)

Authors:

S Chatrchyan, V Khachatryan, AM Sirunyan, A Tumasyan, W Adam, T Bergauer, M Dragicevic, J Erö, C Fabjan, M Friedl, R Frühwirth, VM Ghete, J Hammer, S Hänsel, M Hoch, N Hörmann, J Hrubec, M Jeitler, W Kiesenhofer, M Krammer, D Liko, I Mikulec, M Pernicka, H Rohringer, R Schöfbeck, J Strauss, A Taurok, F Teischinger, P Wagner, W Waltenberger, G Walzel, E Widl, CE Wulz, V Mossolov, N Shumeiko, J Suarez Gonzalez, L Benucci, EA De Wolf, X Janssen, J Maes, T Maes, L Mucibello, S Ochesanu, B Roland, R Rougny, M Selvaggi, H Van Haevermaet, P Van Mechelen, N Van Remortel, F Blekman, S Blyweert, J D'Hondt, O Devroede, R Gonzalez Suarez, A Kalogeropoulos, M Maes, W Van Doninck, P Van Mulders, GP Van Onsem, I Villella, O Charaf, B Clerbaux, G De Lentdecker, V Dero, APR Gay, GH Hammad, T Hreus, PE Marage, L Thomas, C Vander Velde, P Vanlaer, V Adler, A Cimmino, S Costantini, M Grunewald, B Klein, J Lellouch, A Marinov, J McCartin, D Ryckbosch, F Thyssen, M Tytgat, L Vanelderen, P Verwilligen, S Walsh, N Zaganidis, S Basegmez, G Bruno, J Caudron, L Ceard, E Cortina Gil, J De Favereau De Jeneret, C Delaere, D Favart, A Giammanco, G Grégoire, J Hollar, V Lemaitre, J Liao, O Militaru

Abstract:

A first measurement of the polarization of W bosons with large transverse momenta in pp collisions is presented. The measurement is based on 36pb⊃-1 of data recorded at √s=7TeV by the CMS detector at the LHC. The left-handed, right-handed, and longitudinal polarization fractions (f L, fR, and f0, respectively) of W bosons with transverse momenta larger than 50GeV are determined by using decays to both electrons and muons. The muon final state yields the most precise measurement: (fL-fR)⊃-=0.240±0.036(stat)±0.031(syst) and f0-=0.183±0.087(stat)±0.123(syst) for negatively charged W bosons and (fL-fR)⊃+=0.310±0.036(stat) ±0.017(syst) and f0+=0.171±0.085(stat)±0.099(syst) for positively charged W bosons. This establishes, for the first time, that W bosons produced in pp collisions with large transverse momenta are predominantly left-handed, as expected in the standard model. © 2011 American Physical Society.
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Search for a W' boson decaying to a muon and a neutrino in pp collisions at √s=7 TeV

Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 701:2 (2011) 160-179

Authors:

S Chatrchyan, V Khachatryan, AM Sirunyan, A Tumasyan, W Adam, T Bergauer, M Dragicevic, J Erö, C Fabjan, M Friedl, R Frühwirth, VM Ghete, J Hammer, S Hänsel, M Hoch, N Hörmann, J Hrubec, M Jeitler, G Kasieczka, W Kiesenhofer, M Krammer, D Liko, I Mikulec, M Pernicka, H Rohringer, R Schöfbeck, J Strauss, F Teischinger, P Wagner, W Waltenberger, G Walzel, E Widl, CE Wulz, V Mossolov, N Shumeiko, J Suarez Gonzalez, L Benucci, EA De Wolf, X Janssen, T Maes, L Mucibello, S Ochesanu, B Roland, R Rougny, M Selvaggi, H Van Haevermaet, P Van Mechelen, N Van Remortel, F Blekman, S Blyweert, J D'Hondt, O Devroede, R Gonzalez Suarez, A Kalogeropoulos, J Maes, M Maes, W Van Doninck, P Van Mulders, GP Van Onsem, I Villella, O Charaf, B Clerbaux, G De Lentdecker, V Dero, APR Gay, GH Hammad, T Hreus, PE Marage, L Thomas, C Vander Velde, P Vanlaer, V Adler, A Cimmino, S Costantini, M Grunewald, B Klein, A Marinov, J Mccartin, D Ryckbosch, F Thyssen, M Tytgat, L Vanelderen, P Verwilligen, S Walsh, N Zaganidis, S Basegmez, G Bruno, J Caudron, L Ceard, E Cortina Gil, J De Favereau De Jeneret, C Delaere, D Favart, A Giammanco, G Grégoire, J Hollar, V Lemaitre, J Liao, O Militaru, S Ovyn

Abstract:

A new heavy gauge boson, W', decaying to a muon and a neutrino, is searched for in pp collisions at a centre-of-mass energy of 7 TeV. The data, collected with the CMS detector at the LHC, correspond to an integrated luminosity of 36 pb-1. No significant excess of events above the standard model expectation is found in the transverse mass distribution of the muon-neutrino system. Masses below 1.40 TeV are excluded at the 95% confidence level for a sequential standard-model-like W'. The W' mass lower limit increases to 1.58 TeV when the present analysis is combined with the CMS result for the electron channel. © 2011 CERN.
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Measurement of the tt̄ production cross section in pp collisions at √s=7 TeV using the kinematic properties of events with leptons and jets

European Physical Journal C 71:9 (2011) 1-27

Authors:

S Chatrchyan, V Khachatryan, AM Sirunyan, A Tumasyan, W Adam, T Bergauer, M Dragicevic, J Erö, C Fabjan, M Friedl, R Frühwirth, VM Ghete, J Hammer, S Hänsel, M Hoch, N Hörmann, J Hrubec, M Jeitler, W Kiesenhofer, M Krammer, D Liko, I Mikulec, M Pernicka, H Rohringer, R Schöfbeck, J Strauss, A Taurok, F Teischinger, P Wagner, W Waltenberger, G Walzel, E Widl, CE Wulz, V Mossolov, N Shumeiko, J Suarez Gonzalez, S Bansal, L Benucci, EA de Wolf, X Janssen, J Maes, T Maes, L Mucibello, S Ochesanu, B Roland, R Rougny, M Selvaggi, H van Haevermaet, P van Mechelen, N van Remortel, F Blekman, S Blyweert, J D'Hondt, O Devroede, RG Suarez, A Kalogeropoulos, M Maes, W van Doninck, P van Mulders, GP van Onsem, I villella, O Charaf, B Clerbaux, G De Lentdecker, V Dero, APR Gay, GH Hammad, T Hreus, PE Marage, L Thomas, C Vander Velde, P Vanlaer, V Adler, A Cimmino, S Costantini, M Grunewald, B Klein, J Lellouch, A Marinov, J Mccartin, D Ryckbosch, F Thyssen, M Tytgat, L Vanelderen, P Verwilligen, S Walsh, N Zaganidis, S Basegmez, G Bruno, J Caudron, L Ceard, EC Gil, J de Favereau de Jeneret, C Delaere, D Favart, A Giammanco, G Grégoire, J Hollar, V Lemaitre

Abstract:

A measurement of the tt̄ production cross section in proton-proton collisions at a centre-of-mass energy of 7 TeV has been performed at the LHC with the CMS detector. The analysis uses a data sample corresponding to an integrated luminosity of 36 pb-1and is based on the reconstruction of the final state with one isolated, high transverse-momentum electron or muon and three or more hadronic jets. The kinematic properties of the events are used to separate the tt̄ signal from W+jets and QCD multijet background events. The measured cross section is 173+39-32(stat. + syst.) pb, consistent with standard model expectations. © 2011 CERN for the benefit of the CMS collaboration.
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Search for an excess of events with an identical flavour lepton pair and significant missing transverse momentum in √s = TeV proton-proton collisions with the ATLAS detector

European Physical Journal C 71:7 (2011) 1-18

Authors:

G Aad, B Abbott, J Abdallah, AA Abdelalim, A Abdesselam, O Abdinov, B Abi, M Abolins, H Abramowicz, H Abreu, E Acerbi, BS Acharya, DL Adams, TN Addy, J Adelman, M Aderholz, S Adomeit, P Adragna, T Adye, S Aefsky, JA Aguilar-Saavedra, M Aharrouche, SP Ahlen, F Ahles, A Ahmad, M Ahsan, G Aielli, T Akdogan, TPA Åkesson, G Akimoto, AV Akimov, A Akiyama, MS Alam, MA Alam, S Albrand, M Aleksa, IN Aleksandrov, F Alessandria, C Alexa, G Alexander, G Alexandre, T Alexopoulos, M Alhroob, M Aliev, G Alimonti, J Alison, M Aliyev, PP Allport, SE Allwood-Spiers, J Almond, A Aloisio, R Alon, A Alonso, MG Alviggi, K Amako, P Amaral, C Amelung, VV Ammosov, A Amorim, G Amorós, N Amram, C Anastopoulos, T Andeen, CF Anders, KJ Anderson, A Andreazza, V Andrei, ML Andrieux, XS Anduaga, A Angerami, F Anghinolfi, N Anjos, A Annovi, A Antonaki, M Antonelli, S Antonelli, A Antonov, J Antos, F Anulli, S Aoun, L Aperio Bella, R Apolle, G Arabidze, I Aracena, Y Arai, ATH Arce, JP Archambault, S Arfaoui, JF Arguin, E Arik, M Arik, AJ Armbruster, O Arnaez, C Arnault, A Artamonov, G Artoni, D Arutinov, S Asai, R Asfandiyarov, S Ask

Abstract:

Results are presented of a search for particles decaying into final states with significant missing transverse momentum and exactly two identical flavour leptons (e, μ) of opposite charge in √s = TeV collisions at the Large Hadron Collider. This channel is particularly sensitive to supersymmetric particle cascade decays producing flavour correlated lepton pairs. Flavour uncorrelated backgrounds are subtracted using a sample of opposite flavour lepton pair events. Observation of an excess beyond Standard Model expectations following this subtraction procedure would offer one of the best routes to measuring the masses of supersymmetric particles. In a data sample corresponding to an integrated luminosity of 35 pb-1 no such excess is observed. Model-independent limits are set on the contribution to these final states from supersymmetry and are used to exclude regions of a phenomenological supersymmetric parameter space. © 2011 CERN for the benefit of the ATLAS collaboration.
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Search for contact interactions in dimuon events from pp collisions at √s=7TeV with the ATLAS detector

Physical Review D - Particles, Fields, Gravitation and Cosmology 84:1 (2011)

Authors:

G Aad, B Abbott, J Abdallah, AA Abdelalim, A Abdesselam, O Abdinov, B Abi, M Abolins, H Abramowicz, H Abreu, E Acerbi, BS Acharya, DL Adams, TN Addy, J Adelman, M Aderholz, S Adomeit, P Adragna, T Adye, S Aefsky, JA Aguilar-Saavedra, M Aharrouche, SP Ahlen, F Ahles, A Ahmad, M Ahsan, G Aielli, T Akdogan, TPA Åkesson, G Akimoto, AV Akimov, A Akiyama, MS Alam, MA Alam, S Albrand, M Aleksa, IN Aleksandrov, F Alessandria, C Alexa, G Alexander, G Alexandre, T Alexopoulos, M Alhroob, M Aliev, G Alimonti, J Alison, M Aliyev, PP Allport, SE Allwood-Spiers, J Almond, A Aloisio, R Alon, A Alonso, MG Alviggi, K Amako, P Amaral, C Amelung, VV Ammosov, A Amorim, G Amorós, N Amram, C Anastopoulos, T Andeen, CF Anders, KJ Anderson, A Andreazza, V Andrei, ML Andrieux, XS Anduaga, A Angerami, F Anghinolfi, N Anjos, A Annovi, A Antonaki, M Antonelli, S Antonelli, A Antonov, J Antos, F Anulli, S Aoun, L Aperio Bella, R Apolle, G Arabidze, I Aracena, Y Arai, ATH Arce, JP Archambault, S Arfaoui, JF Arguin, E Arik, M Arik, AJ Armbruster, O Arnaez, C Arnault, A Artamonov, G Artoni, D Arutinov, S Asai, R Asfandiyarov, S Ask

Abstract:

A search for contact interactions has been performed using dimuon events recorded with the ATLAS detector in proton-proton collisions at √s=7TeV. The data sample corresponds to an integrated luminosity of 42pb-1. No significant deviation from the standard model is observed in the dimuon mass spectrum, allowing the following 95% C.L. limits to be set on the energy scale of contact interactions: Λ>4.9TeV (4.5 TeV) for constructive (destructive) interference in the left-left isoscalar compositeness model. These limits are the most stringent to date for μμqq contact interactions. 2011 American Physical Society.
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