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Chatrchyan, S.,Khachatryan, V.,Sirunyan, A. M.,Tumasyan, A.,Adam, W.,Aguilo, E.,Bergauer, T.,Dragicevic, M.,Erö,, J.,Fabjan, C.,Friedl, M.,Frü,hwirth, R.,Ghete, V. M.,Hammer, J.,Hö,rmann, Springer-Verlag 2012 The European physical journal. C, Particles and fi Vol.72 No.12
<P>A measurement is presented of the relative prompt production rate of <I>χ</I><SUB>c2</SUB> and <I>χ</I><SUB>c1</SUB> with 4.6 fb<SUP>−1</SUP> of data collected by the CMS experiment at the LHC in pp collisions at [FORMULA OMISSION]. The two states are measured via their radiative decays <I>χ</I><SUB>c</SUB>→J/<I>ψ</I>+<I>γ</I>, with the photon converting into an e<SUP>+</SUP>e<SUP>−</SUP> pair for J/<I>ψ</I> rapidity |<I>y</I>(J/<I>ψ</I>)|<1.0 and photon transverse momentum <I>p</I><SUB>T</SUB>(<I>γ</I>)>0.5 GeV/<I>c</I>. The measurement is given for six intervals of <I>p</I><SUB>T</SUB>(J/<I>ψ</I>) between 7 and 25 GeV/<I>c</I>. The results are compared to theoretical predictions.</P>
Search for charged Higgs bosons in top quark decays
DO Collaboration,Abazov, V.M.,Abbott, B.,Abolins, M.,Acharya, B.S.,Adams, M.,Adams, T.,Aguilo, E.,Ahsan, M.,Alexeev, G.D.,Alkhazov, G.,Alton, A.,Alverson, G.,Alves, G.A.,Ancu, L.S.,Anzelc, M.S.,Aoki, North-Holland Pub. Co 2009 Physics letters: B Vol.682 No.3
We present a search for charged Higgs bosons in top quark decays. We analyze the e+jets, μ+jets, ee, eμ, μμ, τe and τμ final states from top quark pair production events, using data from about 1 fb<SUP>-1</SUP> of integrated luminosity recorded by the DO experiment at the Fermilab Tevatron Collider. We consider different scenarios of possible charged Higgs boson decays, one where the charged Higgs boson decays purely hadronically into a charm and a strange quark, another where it decays into a τ lepton and a τ neutrino and a third one where both decays appear. We extract limits on the branching ratio B(t->H<SUP>+</SUP>b) for all these models. We use two methods, one where the tt@? production cross section is fixed, and one where the cross section is fitted simultaneously with B(t->H<SUP>+</SUP>b). Based on the extracted limits, we exclude regions in the charged Higgs boson mass and tanβ parameter space for different scenarios of the minimal supersymmetric standard model.
Zγ production and limits on anomalous ZZγ and Zγγ couplings in pp@? collisions at s=1.96 TeV
DO Collaboration,Abazov, V.M.,Abbott, B.,Abolins, M.,Acharya, B.S.,Adams, M.,Adams, T.,Aguilo, E.,Ahn, S.H.,Ahsan, M.,Alexeev, G.D.,Alkhazov, G.,Alton, A.,Alverson, G.,Alves, G.A.,Anastasoaie, M.,Ancu North-Holland Pub. Co 2007 Physics letters: B Vol.653 No.5
We present a study of eeγ and μμγ events using 1109 (1009) pb<SUP>-1</SUP> of data in the electron (muon) channel, respectively. These data were collected with the DO detector at the Fermilab Tevatron pp@? collider at s=1.96 TeV. Having observed 453 (515) candidates in the eeγ (μμγ) final state, we measure the Zγ production cross section for a photon with transverse energy E<SUB>T</SUB>>7 GeV, separation between the photon and leptons ΔR<SUB>@</SUB>?<SUB>&</SUB>gamma;>0.7, and invariant mass of the di-lepton pair M<SUB>@</SUB>?<SUB>@</SUB>?>30 GeV/c<SUP>2</SUP>, to be 4.96+/-0.30(stat.+syst.)+/-0.30(lumi.) pb, in agreement with the Standard Model prediction of 4.74+/-0.22 pb. This is the most precise Zγ cross section measurement at a hadron collider. We set limits on anomalous trilinear Zγγ and ZZγ gauge boson couplings of -0.085<h<SUB>30</SUB><SUP>&</SUP>gamma;<0.084, -0.0053<h<SUB>40</SUB><SUP>&</SUP>gamma;<0.0054 and -0.083<h<SUB>30</SUB><SUP>Z</SUP><0.082, -0.0053<h<SUB>40</SUB><SUP>Z</SUP><0.0054 at the 95% C.L. for the form-factor scale Λ=1.2 TeV.
A combined search for the standard model Higgs boson at s=1.96 TeV
DO Collaboration,Abazov, V.M.,Abbott, B.,Abolins, M.,Acharya, B.S.,Adams, M.,Adams, T.,Aguilo, E.,Ahn, S.H.,Ahsan, M.,Alexeev, G.D.,Alkhazov, G.,Alton, A.,Alverson, G.,Alves, G.A.,Anastasoaie, M.,Ancu North-Holland Pub. Co 2008 Physics letters: B Vol.663 No.1
We present new results of the search for WH->@?νbb@? production in pp@? collisions at a center-of-mass energy of s=1.96 TeV, based on a dataset with integrated luminosity of 0.44 fb<SUP>-1</SUP>. We combine these new results with previously published searches by the D0 collaboration, for WH and ZH production analyzed in the E@?<SUB>T</SUB>bb@? final state, for ZH (->@?<SUP>+</SUP>@?<SUP>-</SUP>bb@?) production, for WH (->WWW) production, and for H (->WW) direct production. No signal-like excess is observed either in the WH analysis or in the combination of all D0 Higgs boson analyses. We set 95% C.L. (expected) upper limits on σ(pp@?->WH)xB(H->bb@?) ranging from 1.6 (2.2) pb to 1.9 (3.3) pb for Higgs boson masses between 105 and 145 GeV, to be compared to the theoretical prediction of 0.13 pb for a Standard Model (SM) Higgs boson with mass m<SUB>H</SUB>=115 GeV. After combination with the other D0 Higgs boson searches, we obtain for m<SUB>H</SUB>=115 GeV an observed (expected) limit 8.5 (12.1) times higher than the SM predicted Higgs boson production cross section. For m<SUB>H</SUB>=160 GeV, the corresponding observed (expected) ratio is 10.2 (9.0).
Abazov, V. M.,Abbott, B.,Abolins, M.,Acharya, B. S.,Adams, M.,Adams, T.,Aguilo, E.,Ahn, S. H.,Ahsan, M.,Alexeev, G. D.,Alkhazov, G.,Alton, A.,Alverson, G.,Alves, G. A.,Anastasoaie, M.,Ancu, L. S.,Ande American Physical Society 2008 Physical review letters Vol.100 No.10
<P>We present a measurement of the shape of the Z/gamma* boson transverse momentum (q(T)) distribution in pp --> Z/gamma* --> e(+)e(-) + X events at a center-of-mass energy of 1.96 TeV using 0.98 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron collider. The data are found to be consistent with the resummation prediction at low q(T), but above the perturbative QCD calculation in the region of q(T)>30 GeV/c. Using events with q(T)<30 GeV/c, we extract the value of g(2), one of the nonperturbative parameters for the resummation calculation. Data at large boson rapidity y are compared with the prediction of resummation and with alternative models that employ a resummed form factor with modifications in the small Bjorken x region of the proton wave function.</P>
Studies of jet mass in dijet and W/Z + jet events
Chatrchyan, S.,Khachatryan, V.,Sirunyan, A. M.,Tumasyan, A.,Adam, W.,Aguilo, E.,Bergauer, T.,Dragicevic, M.,Erö,, J.,Fabjan, C.,Friedl, M.,Frü,hwirth, R.,Ghete, V. M.,Hö,rmann, N.,Hrubec, Springer-Verlag 2013 Journal of high energy physics Vol.2013 No.5
Chatrchyan, S.,Khachatryan, V.,Sirunyan, A. M.,Tumasyan, A.,Adam, W.,Aguilo, E.,Bergauer, T.,Dragicevic, M.,Erö,, J.,Fabjan, C.,Friedl, M.,Frü,hwirth, R.,Ghete, V. M.,Hammer, J.,Hö,rmann, Springer-Verlag 2013 Journal of high energy physics Vol.2013 No.5
<P>A measurement is presented of the t (t) over bar production cross section (sigma(t (t) over bar)) in proton-proton collisions at a centre-of-mass energy of 7 TeV, in the all-jet final state that contains at least six jets, two of which are tagged as originating from b quarks. The data correspond to an integrated luminosity of 3.54 fb(-1), collected with the CMS detector at the LHC. The cross section is determined through an unbinned maximum likelihood fit of background and t (t) over bar signal to the reconstructed mass spectrum of t (t) over bar candidates in the data, in which events are subjected to a kinematic fit assuming a t (t) over bar -> W(+)bW(-)(b) over bar -> 6 jets hypothesis. The measurement yields sigma(t (t) over bar) = 139 +/- 10 (stat.) +/- 26 (syst.) +/- 3 (lum.) pb, a result consistent with those obtained in other t (t) over bar decay channels, as well as with predictions of the standard model.</P>