55712077
Electroweak production of Z bosons with forward-backward jets at CMS
110691184
Data filtering in the readout of the CMS Electromagnetic Calorimeter
For an efficient data taking, the Electromagnetic Calorimeter data of the CMS experiment must be limited to 10% of the full event size (1MB). Other requirements limit the average data size to 2kB per data acquisition link. These conditions imply a reduction factor of close to twenty on the data collected. The data filtering in the readout of the Electromagnetic Calorimeter detector is discussed. Test beam data are used to study the digital filtering applied in the readout channels and a full detector simulation allows to estimate the energy thresholds to achieve the desired data suppression factor.
122759770
Performance of tau-lepton reconstruction and identification in CMS
The performance of tau-lepton reconstruction and identification algorithms is studied using a data sample of proton-proton collisions at sqrt(s)=7 TeV, corresponding to an integrated luminosity of 36 inverse picobarns collected with the CMS detector at the LHC. The tau leptons that decay into one or three charged hadrons, zero or more short-lived neutral hadrons, and a neutrino are identified using final-state particles reconstructed in the CMS tracker and electromagnetic calorimeter. The reconstruction efficiency of the algorithms is measured using tau leptons produced in Z-boson decays. The tau-lepton misidentification rates for jets and electrons are determined.
208852683
Performance of the CMS Drift Tube Chambers with Cosmic Rays
Studies of the performance of the CMS drift tube barrel muon system are described, with results based on data collected during the CMS Cosmic Run at Four Tesla. For most of these data, the solenoidal magnet was operated with a central field of 3.8 T. The analysis of data from 246 out of a total of 250 chambers indicates a very good muon reconstruction capability, with a coordinate resolution for a single hit of about 260 microns, and a nearly 100% efficiency for the drift tube cells. The resolution of the track direction measured in the bending plane is about 1.8 mrad, and the efficiency to reconstruct a segment in a single chamber is higher than 99%. The CMS simulation of cosmic rays reproduces well the performance of the barrel muon detector.
118571058
Search for the standard model Higgs boson produced in association with a top-quark pair in pp collisions at the LHC
A bstractA search for the standard model Higgs boson produced in association with a top-quark pair is presented using data samples corresponding to an integrated luminosity of 5.0 fb−1 (5.1 fb−1) collected in pp collisions at the center-of-mass energy of 7 TeV (8 TeV). Events are considered where the top-quark pair decays to either one lepton+jets $ \left( {\mathrm{t}\overline{\mathrm{t}}\to \ell \nu \mathrm{q}\overline{\mathrm{q}}\prime \mathrm{b}\overline{\mathrm{b}}} \right) $ or dileptons $ \left( {\mathrm{t}\overline{\mathrm{t}}\to {\ell^{+}}\nu {\ell^{-}}\overline{\nu}\mathrm{b}\overline{\mathrm{b}}} \right) $, ℓ being an electron or a muon. The search is optimized for the decay mode $ \mathrm{H}\to \mathrm{b}\overline{\mathrm{b}} $. The largest background to the $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H} $ signal is top-quark pair production with additional jets. Artificial neural networks are used to discriminate between signal and background events. Combining the results from the 7 TeV and 8 TeV samples, the observed (expected) limit on the cross section for Higgs boson production in association with top-quark pairs for a Higgs boson mass of 125 GeV is 5.8 (5.2) times the standard model expectation.

122098798
Alignment of the CMS muon system with cosmic-ray and beam-halo muons
The CMS muon system has been aligned using cosmic-ray muons collected in 2008 and beam-halo muons from the 2008 LHC circulating beam tests. After alignment, the resolution of the most sensitive coordinate is 80 microns for the relative positions of superlayers in the same barrel chamber and 270 microns for the relative positions of endcap chambers in the same ring structure. The resolution on the position of the central barrel chambers relative to the tracker is comprised between two extreme estimates, 200 and 700 microns, provided by two complementary studies. With minor modifications, the alignment procedures can be applied using muons from LHC collisions, leading to additional significant improvements.
14228967
Bounds on the simplest little Higgs model mass spectrum through Z leptonic decay
We derive the leptonic neutral current in the simplest little Higgs model and compute the contribution of the model to the decay width $Z\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}$. Using the precision electroweak data we obtain a strong lower bound $f\ensuremath{\ge}5.6\text{ }\text{ }\mathrm{TeV}$ at 95% C.L. on the characteristic energy scale of the model. It results in a lower bound for the new gauge bosons ${W}^{\ensuremath{'}\ifmmode\pm\else\textpm\fi{}}$ and ${Z}^{\ensuremath{'}}$ as being ${M}_{{W}^{\ensuremath{'}\ifmmode\pm\else\textpm\fi{}}}\ensuremath{\ge}2.6\text{ }\text{ }\mathrm{TeV}$ and ${M}_{{Z}^{\ensuremath{'}}}\ensuremath{\ge}3.1\text{ }\text{ }\mathrm{TeV}$, respectively. We also present the allowed values of the $k={f}_{1}/{f}_{2}$ which is the parameter relating the two vacuum expectation values of the scalar triplets in the model, and the $\ensuremath{\mu}$ parameter of a quadratic term, involving the triplets, necessary to provide an acceptable mass range for the standard Higgs boson.
118621663
The Landau gauge gluon propagator at zero and finite temperature: accounting for the combined finite lattice spacing and finite volume effects
In the past years a good comprehension of the infrared gluon propagator has been achieved, with a good qualitative agreement between lattice results and Dyson-Schwinger equations. However, lattice simulations have been performed at physical volumes which are close to 20 fm but using a large lattice spacing. The interplay between volume effects and lattice spacing effects has not been investigated. Here we aim to fill this gap and address how the two effects change the gluon propagator in the infrared region. Furthermore, we provide infinite volume extrapolations which take into account the finite volume and finite lattice spacing . We also report on preliminary results for the gluon propagator at finite temperature.
15870244
Landau Gauge Fixing on GPUs and String Tension
CFC,DepartamentodeFisica,FaculdadedeCienciaseTecnologia,UniversidadedeCoimbra,3004-516Coimbra,PortugalWe explore the performance of CUDA in performing Landau gaugeﬁxing in Lattice QCD, using the steepest descent method with Fourieracceleration. The code performance was tested in a Tesla C2070, Fermiarchitecture. Wealsopresentastudyofthestringtensionatﬁnitetemper-atureintheconﬁnedphase. ThestringtensionisextractedfromthecoloraveragedfreeenergyandfromthecolorsingletusingLandaugaugeﬁxing.PACSnumbers: 11.15.Ha;12.38.Gc
56306636
Light composite Higgs from an effective action for technicolor
We compute an effective action for a composite Higgs boson formed by new fermions belonging to a general technicolor non-Abelian gauge theory, using a quite general expression for the fermionic self-energy that depends on a certain parameter ($\ensuremath{\alpha}$), that defines the technicolor theory from the extreme walking behavior up to the one with a standard operator product expansion behavior. We discuss the values of the trilinear and quadrilinear scalar couplings. Our calculation spans all the possible physical possibilities for mass and couplings of the composite system. In the case of extreme walking technicolor theories we verify that it is possible to have a composite Higgs boson with a mass as light as the present experimental limit, contrary to the usual expectation of a heavy mass for the composite Higgs boson. In this case we obtain an upper limit for the Higgs boson mass, (${M}_{H}\ensuremath{\le}\mathcal{O}(700)\text{ }\text{ }\mathrm{GeV}$ for $SU(2{)}_{\mathrm{TC}}$), and the experimental data on the Higgs boson mass constrain $SU(N{)}_{\mathrm{TC}}$ technicolor gauge groups to be smaller than $SU(10{)}_{\mathrm{TC}}$.
209834712
Search for anomalous production of prompt like-sign muon pairs and constraints on physics beyond the standard model with the ATLAS detector
An inclusive search for anomalous production of two prompt, isolated muons with the same electric charge is presented. The search is performed in a data sample corresponding to 1.6 fb(-1) of integr ...