Data di Pubblicazione:
2012
Abstract:
The first observation of the Z boson decaying to four leptons in proton-proton collisions is presented. The analyzed data set corresponds to an integrated luminosity of 5.02 fb−1 at √s=7 TeV collected by the CMS detector at the Large Hadron Collider. A pronounced resonance peak, with a statistical significance of 9.7 σ, is observed in the distribution of the invariant mass of four leptons (electrons and/or muons) with mass and width consistent with expectations for Z boson decays. The branching fraction and cross section reported here are defined by phase space restrictions on the leptons, namely, 80 < m_4ℓ < 100 GeV, where m_4ℓ is the invariant mass of the four leptons, and m_ℓℓ > 4 GeV for all pairs of leptons, where m_ℓℓ is the two-lepton invariant mass. The measured branching fraction is B(Z→4ℓ)=(4.2+0.9−0.8(stat.)±0.2(syst.))×10−6 and agrees with the standard model prediction of 4.45×10−6. The measured cross section times branching fraction is σ(pp→Z)B(Z→4ℓ)=112+23−20(stat.)+7−5(syst.)+3−2(lumi.) fb, also consistent with the standard model prediction of 120 fb. The four-lepton mass peak arising from Z → 4ℓ decays provides a calibration channel for the Higgs boson search in the H → ZZ → 4ℓ decay mode.
Tipologia CRIS:
03A-Articolo su Rivista
Keywords:
CMS; LHC
Elenco autori:
S. Chatrchyan;V. Khachatryan;A. M. Sirunyan;A. Tumasyan;W. Adam;E. Aguilo;T. Bergauer;M. Dragicevic;J. Erö;C. Fabjan;M. Friedl;R. Frühwirth;V. M. Ghete;J. Hammer;N. Hörmann;J. Hrubec;M. Jeitler;W. Kiesenhofer;V. Knünz;M. Krammer;D. Liko;I. Mikulec;M. Pernicka;B. Rahbaran;C. Rohringer;H. Rohringer;R. Schöfbeck;J. Strauss;A. Taurok;P. Wagner;W. Waltenberger;G. Walzel;E. Widl;C.-E. Wulz;V. Mossolov;N. Shumeiko;J. Suarez Gonzalez;S. Bansal;T. Cornelis;E. A. Wolf;X. Janssen;S. Luyckx;L. Mucibello;S. Ochesanu;B. Roland;R. Rougny;M. Selvaggi;Z. Staykova;H. Haevermaet;P. Mechelen;N. Remortel;A. Spilbeeck;F. Blekman;S. Blyweert;J. D’Hondt;R. Gonzalez Suarez;A. Kalogeropoulos;M. Maes;A. Olbrechts;W. Doninck;P. Mulders;G. P. Onsem;I. Villella;B. Clerbaux;G. Lentdecker;V. Dero;A. P. R. Gay;T. Hreus;A. Léonard;P. E. Marage;A. Mohammadi;T. Reis;L. Thomas;C. Vander Velde;P. Vanlaer;J. Wang;V. Adler;K. Beernaert;A. Cimmino;S. Costantini;G. Garcia;M. Grunewald;B. Klein;J. Lellouch;A. Marinov;J. Mccartin;A.A. Ocampo Rios;D. Ryckbosch;N. Strobbe;F. Thyssen;M. Tytgat;P. Verwilligen;S. Walsh;E. Yazgan;N. Zaganidis;S. Basegmez;G. Bruno;R. Castello;L. Ceard;C. Delaere;T. Pree;D. Favart;L. Forthomme;A. Giammanco;J. Hollar;V. Lemaitre;J. Liao;O. Militaru;C. Nuttens;D. Pagano;A. Pin;K. Piotrzkowski;N. Schul;J. M. Vizan Garcia;N. Beliy;T. Caebergs;E. Daubie;G. H. Hammad;G. A. Alves;M. Correa Martins Junior;D. Jesus Damiao;T. Martins;M. E. Pol;M. H. G. Souza;W. L. Aldá Júnior;W. Carvalho;A. Custódio;E. M. Costa;C. Oliveira Martins;S. Fonseca Souza;D. Matos Figueiredo;L. Mundim;H. Nogima;V. Oguri;W. L. Prado Silva;A. Santoro;L. Soares Jorge;A. Sznajder;C. A. Bernardes;F. A. Dias;T. R. Fernandez Perez Tomei;E. M. Gregores;C. Lagana;F. Marinho;P. G. Mercadante;S. F. Novaes;Sandra S. Padula;V. Genchev;P. Iaydjiev;S. Piperov;M. Rodozov;S. Stoykova;G. Sultanov;V. Tcholakov;R. Trayanov;M. Vutova;A. Dimitrov;R. Hadjiiska;V. Kozhuharov;L. Litov;B. Pavlov;P. Petkov;J. G. Bian;G. M. Chen;H. S. Chen;C. H. Jiang;D. Liang;S. Liang;X. Meng;J. Tao;J. Wang;X. Wang;Z. Wang;H. Xiao;M. Xu;J. Zang;Z. Zhang;C. Asawatangtrakuldee;Y. Ban;S. Guo;Y. Guo;W. Li;S. Liu;Y. Mao;S. J. Qian;H. Teng;D. Wang;L. Zhang;B. Zhu;W. Zou;C. Avila;J. P. Gomez;B. Gomez Moreno;A. F. Osorio Oliveros;J. C. Sanabria;N. Godinovic;D. Lelas;R. Plestina;D. Polic;I. Puljak;Z. Antunovic;M. Kovac;V. Brigljevic;S. Duric;K. Kadija;J. Luetic;S. Morovic;A. Attikis;M. Galanti;G. Mavromanolakis;J. Mousa;C. Nicolaou;F. Ptochos;P. A. Razis;M. Finger;M. Finger;Y. Assran;S. Elgammal;A. Ellithi Kamel;M. A. Mahmoud;A. Radi;M. Kadastik;M. Müntel;M. Raidal;L. Rebane;A. Tiko;P. Eerola;G. Fedi;M. Voutilainen;J. Härkönen;A. Heikkinen;V. Karimäki;R. Kinnunen;M. J. Kortelainen;T. Lampén;K. Lassila-Perini;S. Lehti;T. Lindén;P. Luukka;T. Mäenpää;T. Peltola;E. Tuominen;J. Tuominiemi;E. Tuovinen;D. Ungaro;L. Wendland;K. Banzuzi;A. Karjalainen;A. Korpela;T. Tuuva;M. Besancon;S. Choudhury;M. Dejardin;D. Denegri;B. Fabbro;J. L. Faure;F. Ferri;S. Ganjour;A. Givernaud;P. Gras;G. Hamel Monchenault;P. Jarry;E. Locci;J. Malcles;L. Millischer;A. Nayak;J. Rander;A. Rosowsky;I. Shreyber;M. Titov;S. Baffioni;F. Beaudette;L. Benhabib;L. Bianchini;M. Bluj;C. Broutin;P. Busson;C. Charlot;N. Daci;T. Dahms;L. Dobrzynski;R. Granier Cassagnac;M. Haguenauer;P. Miné;C. Mironov;M. Nguyen;C. Ochando;P. Paganini;D. Sabes;R. Salerno;Y. Sirois;C. Veelken;A. Zabi;J.-L. Agram;J. Andrea;D. Bloch;D. Bodin;J.-M. Brom;M. Cardaci;E. C. Chabert;C. Collard;E. Conte;F. Drouhin;C. Ferro;J.-C. Fontaine;D. Gelé;U. Goerlach;P. Juillot;A.-C. Bihan;P. Hove;F. Fassi;D. Mercier;S. Beauceron;N. Beaupere;O. Bondu;G.
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