We present the results of a search for pair production of a new heavy top-like quark t' decaying to a W boson and another quark using the CDF II detector in Run II of the Tevatron proton-antiproton collider. Using a data sample corresponding to 760 pb^-1 of integrated luminosity, we fit the observed spectrum of total transverse energy and reconstructed t' quark mass to a combination of standard model processes and t' pair production. We see no evidence for t' pair production, and we infer a lower limit of 256 GeV/c^2 on the mass of the t' at 95% C.L. assuming standard strong couplings for the t'.
A study of the substructure of jets with transverse momentum greater than 400 GeV/c produced in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron Collider and recorded by the CDF II detector is presented. The distributions of the jet mass, angularity, and planar flow are measured for the first time in a sample with an integrated luminosity of 5.95 fb^-1. The observed substructure for high mass jets is consistent with predictions from perturbative quantum chromodynamics.
We present the first evidence of WW+WZ production with lepton+jets final states at a hadron collider. The data correspond to 1.07 inverse femtobarns of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider in proton-antiproton collisions at sqrt(s)=1.96 TeV. The observed cross section for WW+WZ production is 20.2 +/- 4.5 pb, consistent with the SM prediction of 16.1 +/- 0.9 pb. The probability for background fluctuations to produce an excess equal to or larger than that observed is estimated to be 5.4e-6, corresponding to a significance of 4.4 standard deviatio…
We search for the standard model Higgs boson produced in association with an electroweak vector boson in events with no identified charged leptons, large imbalance in transverse momentum, and two jets where at least one contains a secondary vertex consistent with the decay of b hadrons. We use ~1 fb-1 integrated luminosity of proton-antiproton collisions at s**(1/2)=1.96 TeV recorded by the CDF II experiment at the Tevatron. We find 268 (16) single (double) b-tagged candidate events, where 248 +/- 43 (14.4 +/- 2.7) are expected from standard model background processes. We place 95% confidence …
We present a measurement of the inclusive top quark pair production cross section in \ppbar collisions at (\sqrt{s}=1.96) TeV utilizing data corresponding to an integrated luminosity of \lumi\ collected with the D0 detector at the Fermilab Tevatron Collider. We consider final states containing one high-$p_{T}$ isolated electron or muon and at least two jets, and we perform three analyses: one exploiting specific kinematic features of \ttbar events, the second using $b$-jet identification, and the third using both techniques to separate \ttbar\ signal from background. In the third case, we dete…
We present two measurements of the ttbar production cross section in collisions of protons and antiprotons at sqrt{s}=1.96 TeV. We analyze a dataset of 310+/-20 pb-1 collected with the CDF2 detector. In the first measurement, we select events with six to eight jets, at least one of which having a displaced secondary vertex, little or no missing transverse energy and optimized kinematical criteria consistent with the ttbar all-hadronic decay channel. In the second measurement, we select events with four or more jets, at least one of which having a displaced secondary vertex, high missing transv…
We present a search for new particles whose decays produce two jets (dijets) using proton-antiproton collision data corresponding to an integrated luminosity of 1.13 fb-1 collected with the CDF II detector. The measured dijet mass spectrum is found to be consistent with next-to-leading-order perturbative QCD predictions, and no significant evidence of new particles is found. We set upper limits at the 95% confidence level on cross sections times the branching fraction for the production of new particles decaying into dijets with both jets having a rapidity magnitude |y| < 1. These limits are u…
We present preliminary measurements of $Z/γ^*$+jets, $W+c$ and $Z+b+X$ at the Tevatron, and review recent measurements of vector boson plus inclusive and heavy-flavor jets production. All measurements are in agreement with next-to-leading-order QCD calculations within the experimental and theoretical uncertainties. We also point to comparisons of the production rate and kinematics of the data with several Monte Carlo simulation programs of vector boson + jets processes.
We present a new measurement of the forward-backward asymmetry in ttbar production in ppbar collisions in the lepton+jets channel at D0. We measure asymmetries from two different observables and unfold the data to allow the results to be compared to standard model predictions. For the unfolded asymmetry based on the Delta-y variable, we measure (19.6 +/- 6.5)%, compared with an MC@NLO-based prediction of (5.0 +/- 0.1)%. We also discuss the correlation between the asymmetry and the transverse momentum of the ttbar system.
A measurement of the forward-backward charge asymmetry in top-antitop (t\bar{t}) pair production in proton-antiproton (p\bar{p}) collisions is presented. The asymmetry is measured for different jet multiplicities in the lepton+jets final state on 0.9 fb^{-1} of data collected by the D0 experiment at the Fermilab Tevatron Collider. The result is sensitive to new physics, which is demonstrated by setting an upper limit on t\bar{t} production via heavy neutral gauge bosons (Z^{\prime}).
A comprehensive overview of the latest aspects of jet physics in proton-antiproton collisions at $\sqrt{s}=$1.96 TeV is presented. In particular, measurements of the inclusive jet production, dijet and multi-jet production, and jet substructure studies are discussed.
Measurements of differential photon + c jet and photon + b jet production cross sections are presented using approximately 1 fb-1 of data collected by the D0 detector at the Tevatron proton-antiproton collider at a center-of-mass energy of 1.96 TeV. Isolated photons are selected in the rapidity range |y| < 1.0 and jets selected with rapidities |y| < 0.8. The measurements are compared to next-to-leading order theoretical predictions.
We present an update on the status of the W and Z cross sections in proton-antiproton collisions at 1.96 TeV on behalf of the DZero and CDF collaborations. Preliminary studies of the differential cross sections with different jet multiplicities and as a function of jet transverse energy are also presented.
We present a search for WW and WZ production in final states that contain a charged lepton (electron or muon) and at least two jets, produced in sqrt(s) = 1.96 TeV ppbar collisions at the Fermilab Tevatron, using data corresponding to 1.2 fb-1 of integrated luminosity collected with the CDF II detector. Diboson production in this decay channel has yet to be observed at hadron colliders due to the large single W plus jets background. An artificial neural network has been developed to increase signal sensitivity, as compared with an event selection based on conventional cuts. We set a 95% confid…
A search is performed for heavy Majorana neutrinos (N) decaying into a W boson and a lepton using the CMS detector at the Large Hadron Collider. A signature of two jets and either two same sign electrons or a same sign electron-muon pair is searched for using 19.7 inverse femtobarns of data collected during 2012 in proton-proton collisions at a centre-of-mass energy of 8 TeV. The data are found to be consistent with the expected standard model (SM) background and, in the context of a Type-1 seesaw mechanism, upper limits are set on the cross section times branching fraction for production of h…
Photon plus jet production has been studied by the D0 experiment in Run II of the Fermilab Tevatron Collider at a centre of mass energy of sqrt{s}=1.96 TeV. Measurements of the inclusive photon, inclusive photon plus jet, photon plus heavy flavour jet cross sections and double parton interactions in photon plus three jet events are presented. They are based on integrated luminosities between 0.4 fb$^-1 and 1.0 fb^-1. The results are compared to perturbative QCD calculations in various approximations.
We present a measurement of the $\ttbar$ production cross section in $\ppbar$ collisions at $\sqrt{s}=1.96$ TeV using events containing a high transverse momentum electron or muon, three or more jets, and missing transverse energy. Events consistent with $\ttbar$ decay are found by identifying jets containing candidate heavy-flavor semileptonic decays to muons. The measurement uses a CDF Run II data sample corresponding to $2 \mathrm{fb^{-1}}$ of integrated luminosity. Based on 248 candidate events with three or more jets and an expected background of $79.5\pm5.3$ events, we measure a producti…
The cross section for production of Z bosons with two associated b-jets, and Z decaying to leptons, can be measured at the LHC with about 100 pb-1 of data. We use simulated data to study possible strategies for an early measurement of this process with the CMS detector. The rate and kinematic properties of this final state needs to be well understood because it constitutes a large fraction of the total backgrounds to several of the Higgs discovery channels at the LHC.
Some Beyond the Standard Model theories predict new particles that decay predominantly into top-antitop quark pairs. A search for top-antitop quark resonances that decay into the lepton plus jets final state is carried out with the ATLAS experiment at the LHC using 14 fb$^{-1}$ of $\sqrt{s}$ = 8 TeV proton-proton collisions. The search considers both cases where all of the final state jets are isolated and where some or all of the top quark decay products are merged into a single jet. Mass exclusion limits at a 95% credibility level are set for two benchmark models, one predicting leptophobic …
We present a measurement of the $\ttbar$ production cross section using $194 \mathrm{pb^{-1}}$ of CDF II data using events with a high transverse momentum electron or muon, three or more jets, and missing transverse energy. The measurement assumes 100% $t\to Wb$ branching fraction. Events consistent with $\ttbar$ decay are found by identifying jets containing heavy flavor semileptonic decays to muons. The dominant backgrounds are evaluated directly from the data. Based on 20 candidate events and an expected background of 9.5$\pm$1.1 events, we measure a production cross section of $5.3\pm3.3^{…
The dynamics of isolated-photon plus one-, two- and three-jet production in $pp$ collisions at a centre-of-mass energy of 8 TeV are studied with the ATLAS detector at the LHC using a data set with an integrated luminosity of 20.2 fb$^{-1}$. Measurements of isolated-photon plus jets cross sections are presented as functions of the photon and jet transverse momenta. The cross sections as functions of the azimuthal angle between the photon and the jets, the azimuthal angle between the jets, the photon-jet invariant mass and the scattering angle in the photon-jet centre-of-mass system are presente…
The DZERO detector is used to study proton-antiproton collisions at the 1800 GeV and 630 GeV center-of-mass energies available at the Fermilab Tevatron. To measure jets, the detector uses a sampling calorimeter composed of uranium and liquid argon as the passive and active media respectively. Understanding the jet energy calibration is not only crucial for precision tests of QCD, but also for the measurement of particle masses and the determination of physics backgrounds associated with new phenomena. This paper describes the energy calibration of jets observed with the DZERO detector at the t…
The properties of high-mass multijet events produced at the Fermilab proton-antiproton collider are compared with leading order QCD matrix element predictions, QCD parton shower Monte Carlo predictions, and the predictions from a model in which events are distributed uniformly over the available multibody phase-space. Multijet distributions corresponding to (4N-4) variables that span the N-body parameter space are found to be well described by the QCD calculations for inclusive three-jet, four-jet, and five-jet events. The agreement between data, QCD Matrix Element calculations, and QCD parton…
We present a search for a narrow-width heavy resonance decaying into top quark pairs X->ttbar in ppbar collisions at sqrt{s}=1.96TeV using approximately 0.9fb^-1 of data collected with the D0 detector at the Fermilab Tevatron Collider. This analysis considers ttbar candidate events in the lepton plus jets channel with at least one identified b jet and uses the ttbar invariant mass distribution to search for evidence of resonant production. We find no evidence for a narrow resonance X decaying to ttbar. Therefore, we set upper limits on sigma*B(X->ttbar) for different hypothesized resonance mas…
We present a measurement of the mass of the top quark from ppbar collisions at 1.96 TeV observed with the Collider Detector at Fermilab (CDF) at the Fermilab Tevatron Run II. The events have the decay signature of ppbar to ttbar in the lepton plus jets channel in which at least one jet is identified as coming from a secondary vertex and therefore a b-hadron. The largest systematic uncertainty, the jet energy scale (JES), is convoluted with the statistical error using an in-situ measurement of the hadronic W boson mass. We calculate a likelihood for each event using leading-order ttbar and W+je…
We present the results of a search for a new heavy top-like quark, tprime, decaying to a W boson and another quark using the CDF II Detector in Run II of the Tevatron ppbar collider. New top-like quarks are predicted in a number of models of new physics. Using a data sample corresponding to 2.8 fb-1 of integrated luminosity we fit the observed spectrum of total transverse energy and reconstructed quark mass to a combination of background plus signal. We see no evidence for tprime production, so use this result to set limits on the tprime tprimebar production cross section times the branching r…
This document presents a search for a $W'$ boson, decaying to a top quark and a $b$ quark in an effective coupling approach, using a multivariate method based on boosted decision trees. It reports exclusion limits on the $W'\rightarrow tb$ cross-section times branching ratio and effective couplings as a function of the $W'$-boson mass. The search covers $W'$-boson masses between 0.5 and 3.0 TeV, for right-handed or left-handed $W'$-boson, with 20.3 fb$^{-1}$ of proton-proton collision data produced by the LHC in 2012, at a center-of-mass energy of 8 TeV and collected by the ATLAS detector.
This paper presents a search for a new heavy particle produced in association with a top or antitop quark. Two models in which the new heavy particle is a color singlet or a color triplet are considered, decaying respectively to tbarq or tq, leading to a resonance within the ttbar + jets signature. The full 2011 ATLAS pp collision dataset from the LHC (4.7 fb-1) is used to search for ttbar events produced in association with jets, in which one of the W bosons from the top quarks decays leptonically and the other decays hadronically. The data are consistent with the Standard Model expectation, …
Results are presented for the inclusive jet cross section versus jet transverse energy in proton-antiproton collisions at center of mass energy 1.8 TeV as measured by the CDF and D0 detectors at Fermilab's Tevatron collider. The data are compared to next-to-leading order QCD predictions using different input parton distribution functions. The ratio of inclusive jet cross sections at center of mass energy 0.63 TeV and center of mass energy 1.8 TeV, versus jet x_T, is also presented and compared to QCD predictions.
Double-parton scattering is investigated using events with a Z boson and jets. The Z boson is reconstructed using only the dimuon channel. The measurements are performed with proton-proton collision data recorded by the CMS experiment at the LHC at $\sqrt{s} =$ 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$ collected in the year 2016. Differential cross sections of Z + $\geq$ 1 jet and Z + $\geq$ 2 jets are measured with transverse momentum of the jets above 20 GeV and pseudorapidity $|η|$ $\lt$ 2.4. Several distributions with sensitivity to double-parton scattering effect…
We present a comprehensive analysis of inclusive W(\to eν)+n-jet (n\geq 1,2,3,4) production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV at the Tevatron collider using a 3.7 fb^{-1} dataset collected by the D0 detector. Differential cross sections are presented as a function of the jet rapidities (y), lepton transverse momentum (p_T) and pseudorapidity (η), the scalar sum of the transverse energies of the W boson and all jets (H_T), leading dijet p_T and invariant mass, dijet rapidity separations for a variety of jet pairings for p_T-ordered and angular-ordered jets, …
Vector boson scattering and anomalous quartic couplings in final states with $\ellν$qq or $\ell\ell$qq plus jets using proton-proton collisions at $\sqrt{s}$ = 13 TeV
EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)（欧洲核子研究组织（CERN））
We have compared the proton and antiproton angular distributions in 117 million Xi-minus -> Lambda + pi-minus -> proton + pi-minus + pi-minus and 41 million anti-Xi-minus -> anti-Lamba + pi-plus -> antiproton + pi-plus + pi-plus decays using a subset of the data from the HyperCP experiment (E871) at Fermilab. We find no evidence of CP violation, with the direct-CP-violating parameter $A_{ΞΛ} = \frac{α_Ξα_Λ - \barα_Ξ\barα_Λ}{α_Ξα_Λ + \barα_Ξ\barα_Λ} = [0.0+/-5.1(stat)+/-4.4(syst)]{\times}10^{-4}$.
We report a search for single top quark production with the CDF II detector using 2.1 fb-1 of integrated luminosity of pbar p collisions at sqrt{s}=1.96 TeV. The data selected consist of events characterized by large energy imbalance in the transverse plane and hadronic jets, and no identified electrons and muons, so the sample is enriched in W -> tau nu decays. In order to suppress backgrounds, additional kinematic and topological requirements are imposed through a neural network, and at least one of the jets must be identified as a b-quark jet. We measure an excess of signal-like events in a…
We describe a measurement of the top quark mass from events produced in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV, using the Collider Detector at Fermilab. We identify top-antitop candidates where both W bosons from the top quarks decay into leptons (electron, muon, or tau plus neutrino) from a data sample of 360 inverse picobarns. The top quark mass is reconstructed in each event separately by three different methods, which draw upon simulated distributions of the neutrino pseudorapidity, top-antitop longitudinal momentum, or neutrino azimuthal angle in order to extr…
This thesis presents the evidence, at 3.08 sigma, for the associate production of massive vector bosons (W and Z) in a final state with one lepton, MET and HF-tagged jets, measured with the complete CDF II dataset (9.4fb^-1 of data). The signals, both inclusive diboson production and WW vs WZ/ZZ separately, were extracted from the invariant mass distribution, M_inv(jet1,jet2), of single and double HF-tagged jet pairs. For single-tagged events the b quark vs c quark discrimination was obtained by using a bi-dimensional distribution M_inv(jet1,jet2) vs a flavor-serapator NN. The results, consist…
Jets plus missing transverse energy is one of the main search channels for new physics at the LHC. A major limitation lies in our understanding of QCD backgrounds. Using jet merging we can describe the number of jets in typical background channels in terms of a staircase scaling, including theory uncertainties. The scaling parameter depends on the particles in the final state and on cuts applied. Measuring the staircase scaling will allow us to also predict the effective mass for Standard Model backgrounds. Based on both observables we propose an analysis strategy avoiding model specific cuts …
A search is presented for the pair production of heavy vector-like $B$ quarks, primarily targeting $B$ quark decays into a $W$ boson and a top quark. The search is based on $36.1$ $fb^{-1}$ of $pp$ collisions at $\sqrt{s}$ = 13 TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. Data are analysed in the lepton-plus-jets final state, characterised by a high-transverse-momentum isolated electron or muon, large missing transverse momentum, and multiple jets, of which at least one is $b$-tagged. No significant deviation from the Standard Model expectation is ob…
We present a direct measurement of the mass difference between top and antitop quarks (dm) in lepton+jets top-antitop final states using the "matrix element" method. The purity of the lepton+jets sample is enhanced for top-antitop events by identifying at least one of the jet as originating from a b quark. The analyzed data correspond to 3.6 fb-1 of proton-antiproton collisions at 1.96 TeV acquired by D0 in Run II of the Fermilab Tevatron Collider. The combination of the e+jets and mu+jets channels yields dm = 0.8 +/- 1.8 (stat) +/- 0.5 (syst) GeV, which is in agreement with the standard model…
We present measurements of the differential cross section $dσ/dp_{T}^γ$ for the associated production of a $c$-quark jet and an isolated photon with rapidity $|y^γ|< 1.0$ and transverse momentum $30 < p_{T}^γ < 300$ GeV. The $c$-quark jets are required to have $|y^{jet}| < 1.5$ and $p_{T}^{jet} >15$ GeV. The ratio of differential cross sections for photon+ c and photon+ b production as a function of $p_{T}^γ$ is also presented. The results are based on data corresponding to an integrated luminosity of 8.7 fb$^{-1}$ recorded with the D0 detector at the Fermilab Tevatron $p\bar{p}$ Collider at $…
A search for pair production of a scalar partner of the top quark in events with four or more jets plus missing transverse momentum is presented. An analysis of 36.1 fb$^{-1}$ of $\sqrt{s}$=13 TeV proton-proton collisions collected using the ATLAS detector at the LHC yields no significant excess over the expected Standard Model background. To interpret the results a simplified supersymmetric model is used where the top squark is assumed to decay via $\tilde{t}_1 \rightarrow t^{(*)} \tildeχ^0_1$ and $\tilde{t}_1\rightarrow b\tildeχ^\pm_1 \rightarrow b W^{(*)} \tildeχ^0_1$, where $\tildeχ^0_1$ (…
We present a next-to-leading order calculation of Higgs boson production plus one and two jets via gluon fusion interfaced to shower Monte Carlo programs, implemented according to the POWHEG method. For this implementation we have used a new interface of the POWHEG BOX with MadGraph4, that generates the codes for generic Born and real processes automatically. The virtual corrections have been taken from the MCFM code. We carry out a simple phenomenological study of our generators, comparing them among each other and with fixed next-to-leading order results.
This paper reports inclusive and differential measurements of the $t\bar{t}$ charge asymmetry $A_{\textrm{C}}$ in 20.3 fb$^{-1}$ of $\sqrt{s} = 8$ TeV $pp$ collisions recorded by the ATLAS experiment at the Large Hadron Collider at CERN. Three differential measurements are performed as a function of the invariant mass, transverse momentum and longitudinal boost of the $t\bar{t}$ system. The $t\bar{t}$ pairs are selected in the single-lepton channels ($e$ or $μ$) with at least four jets, and a likelihood fit is used to reconstruct the $t\bar{t}$ event kinematics. A Bayesian unfolding procedure …
We report a measurement of the top quark mass, m_t, obtained from ppbar collisions at sqrt(s) = 1.96 TeV at the Fermilab Tevatron using the CDF II detector. We analyze a sample corresponding to an integrated luminosity of 1.9 fb^-1. We select events with an electron or muon, large missing transverse energy, and exactly four high-energy jets in the central region of the detector, at least one of which is tagged as coming from a b quark. We calculate a signal likelihood using a matrix element integration method, with effective propagators to take into account assumptions on event kinematics. Our…
A search for new particles that decay into top quark pairs (ttbar) is performed with the ATLAS experiment at the LHC using an integrated luminosity of 4.7 fb^-1 of proton-proton (pp) collision data collected at a center-of-mass energy sqrt(s)=7 TeV. In the ttbar --> WbWb decay, the lepton plus jets final state is used, where one W boson decays leptonically and the other hadronically. The ttbar system is reconstructed using both small-radius and large-radius jets, the latter being supplemented by a jet substructure analysis. A search for local excesses in the number of data events compared to t…
A search for new heavy particles that decay into top-quark pairs is performed using data collected from proton-proton collisions at a centre-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. The integrated luminosity of the data sample is 36.1 fb$^{-1}$. Events consistent with top-quark pair production are selected by requiring a single isolated charged lepton, missing transverse momentum and jet activity compatible with a hadronic top-quark decay. Jets identified as likely to contain $b$-hadrons are required to reduce the background from other Standard Model process…
We present results on dijet production via hard color-singlet exchange in proton-antiproton collisions at root-s = 630 GeV and 1800 GeV using the DZero detector. The fraction of dijet events produced via color-singlet exchange is measured as a function of jet transverse energy, separation in pseudorapidity between the two highest transverse energy jets, and proton-antiproton center-of-mass energy. The results are consistent with a color-singlet fraction that increases with an increasing fraction of quark-initiated processes and inconsistent with two-gluon models for the hard color-singlet.
Within the 3-3-1 model framework, we consider the production and decay of fermionic leptoquarks into a striking experimental signature at the LHC: a narrow resonance at the $b$ jet plus same-sign dileptons channel. The data already accumulated by the LHC collaborations may hide a large number of events associated to the production and decay of such exotic quarks, allowing one to investigate large portions of the parameters space of the model. The observation or not of such events would shed light on the construction of models presenting heavy exotic quarks.
We present a measurement of the mass of the top quark from proton-antiproton collisions recorded at the CDF experiment in Run II of the Fermilab Tevatron. We analyze events from the single lepton plus jets final state ($t\bar t\to W^+bW^-\bar b\to lνb q \bar q'\bar b$). The top quark mass is extracted using a direct calculation of the probability density that each event corresponds to the $t\bar t$ final state. The probability is a function of both the mass of the top quark and the energy scale of the calorimeter jets, which is constrained {\it in situ} by the hadronic $W$ boson mass. Using 16…
The cross section for photon production in association with at least one jet containing a $b$-quark hadron has been measured in proton antiproton collisions at $\sqrt{s}=1.96$ TeV. The analysis uses a data sample corresponding to an integrated luminosity of 340 pb$^{-1}$ collected with the CDF II detector. Both the differential cross section as a function of photon transverse energy $E_T^γ$, $d σ$($p \overline{p} \to γ+ \geq 1 b$-jet)/$d E_T^γ$ and the total cross section $σ$($p \overline{p} \to γ+ \geq 1 b$-jet; $E_T^γ> 20$ GeV) are measured. Comparisons to a next-to-leading order prediction …
We study Higgs boson plus two high energy jets production at the LHC in the kinematics where the two jets are well separated in rapidity. The partonic processes are dominated by the t-channel weak boson fusion (WBF) and gluon fusion (GF) contributions. We derive the associated QCD resummation formalism for the correlation analysis where the total transverse momentum q_\perp of the Higgs boson and two jets is small. Because of different color structures, the resummation results lead to distinguished behaviors: the WBF contribution peaks at relative low q_\perp while all GF channel contributions…
We present a search for the pair-production of a non-standard-model strongly-interacting particle that decays to a pair of quarks or gluons, leading to a final state with four hadronic jets. We consider both non-resonant production via an intermediate gluon as well as resonant production via a distinct non-standard-model intermediate strongly-interacting particle. We use data collected by the CDF experiment in proton-antiproton collisions at $\sqrt{s}=1.96$ TeV corresponding to an integrated luminosity of 6.6 fb$^{-1}$. We find the data to be consistent with standard model predictions. We repo…
A search for new charged massive gauge bosons, $W^\prime$, is performed with the ATLAS detector at the LHC. Data were collected in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV and correspond to an integrated luminosity of 36.1 $\textrm{fb}^{-1}$. This analysis searches for $W^\prime$ bosons in the $W^\prime \rightarrow t\bar{b}$ decay channel in final states with an electron or muon plus jets. The search covers resonance masses between 0.5 and 5.0 TeV and considers right-handed $W^\prime$ bosons. No significant deviation from the Standard Model (SM) expectation is…
A search is presented for production of a heavy up-type quark (t') together with its antiparticle, assuming a significant branching ratio for subsequent decay into a W boson and a b quark. The search is based on 4.7 fb^-1 of pp collisions at sqrt(s)=7 TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. Data are analyzed in the lepton+jets final state, characterized by a high-transverse-momentum isolated electron or muon, large missing transverse momentum and at least three jets. The analysis strategy relies on the substantial boost of the W bosons in the t't'bar sig…
The latest top quark mass measurements by the CDF and DØ~ experiments are presented here. The mass has been determined in the dilepton ($\ttbar \to eμ,ee,μμ$ + jets +$\met$) and lepton plus jets ($\ttbar \to e$ or $μ$ + jets +$\met$) final states. The most accurate single result from lepton plus jets channel is 173.5$^{+3.7}_{-3.6}$(stat. + Jet Energy Scale Systematic)$\pm1.3$(syst.) ~GeV/c$^{2}$, which is better than the combined CDF and DØ~ Run~I average. A preliminary and unofficial average of the best experimental Run~II results gives $M_{top}$ = $172.7\pm3.5$ GeV/c${^2}$.
This report describes a measurement of the top quark mass, M_{top}, with the dynamical likelihood method (DLM) using the CDF II detector at the Fermilab Tevatron. The Tevatron produces top/anti-top pairs in protons and anti-protons collisions at a center-of-mass energy of 1.96 TeV. The data sample used in this analysis was accumulated from March 2002 through August 2004, which corresponds to an integrated luminosity of 318 pb^{-1}. We use the top/anti-top candidates in the ``lepton+jets'' decay channel, requiring at least one jet identified as a b quark by finding a displaced secondary vertex.…
A search for pair production of vector-like quarks, both up-type ($T$) and down-type ($B$), as well as for four-top-quark production, is presented. The search is based on $pp$ collisions at $\sqrt{s}=8$ TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider and corresponding to an integrated luminosity of 20.3 fb$^{-1}$. Data are analysed in the lepton-plus-jets final state, characterised by an isolated electron or muon with high transverse momentum, large missing transverse momentum and multiple jets. Dedicated analyses are performed targeting three cases: a $T$ quark …
We show that the signature of two boosted $W$-jets plus large missing energy is very promising to probe heavy charged resonances ($X^\pm$) through the process of $pp\to X^+X^-\to W^+W^- X^0 X^0$ where $X^0$ denotes dark matter candidate. The hadronic decay mode of the $W$ boson is considered to maximize the number of signal events. When the mass split between $X^\pm$ and $X^0$ is large, one has to utilize the jet-substructure technique to analyze the boosted $W$-jet. For illustration we consider the process of chargino pair production at the LHC, i.e., $pp\to χ_1^+χ^-_1 \to W^+W^-χ_1^0χ_1^0$, …
Extra scalar fields are common in beyond Standard Model (SM) new physics, and they may mix with the 125 GeV SM-like Higgs boson discovered at the LHC. This fact suggests possible discovery channels for these new scalar fields with their decay modes involving the 125 GeV Higgs boson. In this work, we explore the LHC search potential of the heavy CP-even Higgs boson H in the two-Higgs-doublet model. We focus on the channel of H decaying to a pair of light CP-even Higgs bosons h, with two h's decaying to two b jets and diphoton sequentially. This channel is particularly involved when the relevant…
