Universidad Iberoamericana Ciudad de México

About: Universidad Iberoamericana Ciudad de México is a education organization based out in Mexico City, Mexico. It is known for research contribution in the topics: Large Hadron Collider & Standard Model. The organization has 2259 authors who have published 3981 publications receiving 109298 citations.

Search for heavy neutrinos and WR bosons with right-handed couplings in a left-right symmetric model in pp collisions at √s=7 TeV

Abstract: Results are presented from a search for heavy, right-handed muon neutrinos, Nμ, and right-handed WR bosons, which arise in the left-right symmetric extensions of the standard model. The analysis is based on a 5.0 fb-1 sample of proton-proton collisions at a center-of-mass energy of 7 TeV, collected by the CMS detector at the Large Hadron Collider. No evidence is observed for an excess of events over the standard model expectation. For models with exact left-right symmetry, heavy right-handed neutrinos are excluded at 95% confidence level for a range of neutrino masses below the WR mass, dependent on the value of MWR. The excluded region in the two-dimensional (MWR, MNμ) mass plane extends to MWR=2.5 TeV.

Search for exclusive or semi-exclusive gamma gamma production and observation of exclusive and semi-exclusive e(+)e(-) production in pp collisions at root s=7 TeV

Abstract: A search for exclusive or semi-exclusive γγ production, pp → p^(*) + γγ + p^(*) (where p^* stands for a diffractively-dissociated proton), and the observation of exclusive and semi-exclusive e^+e^− production, pp → p^(*) + e^+e^− + p^(*), in proton-proton collisions at s√=7 TeV, are presented. The analysis is based on a data sample corresponding to an integrated luminosity of 36 pb^(−1) recorded by the CMS experiment at the LHC at low instantaneous luminosities. Candidate γγ or e^+e^− events are selected by requiring the presence of two photons or a positron and an electron, each with transverse energy E_T > 5.5 GeV and pseudorapidity |η| < 2.5, and no other particles in the region |η| < 5.2. No exclusive or semi-exclusive diphoton candidates are found in the data. An upper limit on the cross section for the reaction pp → p^(*) + γγ + p^(*), within the above kinematic selections, is set at 1.18 pb at 95% confidence level. Seventeen exclusive or semi-exclusive dielectron candidates are observed, with an estimated background of 0.85 ± 0.28 (stat.) events, in agreement with the QED-based prediction of 16.3 ± 1.3 (syst.) events.

Measurement of BB̄ angular correlations based on secondary vertex reconstruction at √s = 7 TeV

Abstract: A measurement of the angular correlations between beauty and anti-beauty hadrons (B B-bar) produced in pp collisions at a centre-of-mass energy of 7 TeV at the CERN LHC is presented, probing for the first time the region of small angular separation. The B hadrons are identified by the presence of displaced secondary vertices from their decays. The B hadron angular separation is reconstructed from the decay vertices and the primary-interaction vertex. The differential B B-bar production cross section, measured from a data sample collected by CMS and corresponding to an integrated luminosity of 3.1 inverse picobarns, shows that a sizable fraction of the B B-bar pairs are produced with small opening angles. These studies provide a test of QCD and further insight into the dynamics of b b-bar production.

Search for fractionally charged particles in pp collisions at s√=7 TeV

Abstract: A search is presented for free heavy long-lived fractionally charged particles produced in pp collisions at √s=7 TeV. The data sample was recorded by the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb-1. Candidate fractionally charged particles are identified by selecting tracks with associated low charge measurements in the silicon tracking detector. Observations are found to be consistent with expectations for background processes. The results of the search are used to set upper limits on the cross section for pair production of fractionally charged, massive spin-1/2 particles that are neutral under SU(3)C and SU(2)L. We exclude at 95% confidence level such particles with electric charge ±2e/3 with masses below 310 GeV, and those with charge ±e/3 with masses below 140 GeV.

Measurement of branching ratio and Bs0 lifetime in the decay Bs0→J/ψf0(980) at CDF

Abstract: We present a study of Bs0 decays to the CP-odd final state J/ψ f0(980) with J/ψ → µ+µ- and f0(980) → π+π-. Using pp collision data with an integrated luminosity of 3.8 fb-1 collected by the CDF II detector at the Tevatron we measure a Bs0 lifetime of τ(B0s → J/ψ f0(980)) = 1.70-0.11+0.12(stat) ± 0.03(syst) ps. This is the first measurement of the Bs0} lifetime in a decay to a CP eigenstate and corresponds in the standard model to the lifetime of the heavy Bs0 eigenstate. We also measure the product of branching fractions of B0s → J/ψ f0(980) and f0(980) → π+π- relative to the product of branching fractions of B0s → J/ψφ and φ→K+K- to be Rf0/ψ = 0.257 ± 0.020(stat) ± 0.014(syst), which is the most precise determination of this quantity to date.