The high-mass spectrum of lepton and photon pairs is sensitive to a broad range of new physics. Examples are extra dimensions and new gauge bosons such as the W' and Z'. Additionally, electron compositeness would result in excited electrons that decay into an electron and a photon. We report the latest results of searches for high-mass dilepton, diphoton, and electron-photon resonances by the CDF and D0 experiments at the Tevatron.
We present searches for pair-production of fourth generation tprime quarks in their decays to Wq. We analyse 4.6 fb-1 and 4.3 fb-1 of data collected by the CDF and D0 detectors, respectively, at the Fermilab Tevatron collider at a centre-of-mass energy of sqrt s = 1.96 TeV. We reconstruct the mass of the heavy quark and perform a two-dimensional-fit to the observed (HT, Mreco) distributions to discriminate the new physics signal from standard model backgrounds. As no significant excess of events is observed, we exclude a fourth-generation tprime quark with a mass below 335 (296) GeV at 95%CL a…
In this report a new search for a narrow-width heavy resonance decaying into top quark pairs (X -> ttbar) in ppbar collisions at sqrt(s)=1.96 TeV has been performed using data collected by the D0 detector at the Fermilab Tevatron collider. The analysis considers ttbar candidate events in the lepton+jets channel using a lifetime tag to identify b-jets and the ttbar invariant mass distribution to search for evidence of resonant production. The analyzed dataset corresponds to an integrated luminosity of approximately 370 pb^-1. Since no evidence for a ttbar resonance X is found, upper limits on s…
We present the status of the Standard Model Higgs boson searches in final states containing τ leptons using data collected from p-pbar collisions at Fermilab Tevatron collider at center-of-mass energy of 1.96 TeV. A summary of the latest results from CDF and D0 collaborations is reported in this paper.
Numerous searches for new phenomena have been carried out using data from proton-antiproton collisions at Fermilab's Tevatron. Final states with leptons give signatures which are relatively unique and generally have small backgrounds. We present many of the latest results from the CDF and D0 collaborations from 0.4-1.2 fb^-1 of data. Topics include supersymmetry, extra gauge bosons, Randall-Sundrum gravitons, excited electrons and neutral, long-lived particles.
We reviewed CDF and D0 searches for R-parity violation supersymmetry in leptons involved final states using up to 344+-21 pb-1 Tevatron Run II data of ppbar collisions at sqrt{s} = 1.96 TeV. All the results were in good agreement with the standard model expectations. No evidence of new physics was observed. However, owing to the improvement on detectors, energy and luminosity from Run I to Run II, the limits for the existence of R-parity violation supersymmetry have been greatly advanced.
Various measurements of the top quark mass in the lepton+jets decay channel of top quark pair production are presented. The measurements are performed on data samples of up to 2.7 fb-1 of integrated luminosity acquired by the CDF and D0 experiments in Run-II of the Tevatron proton-anti-proton collider at a center-of-mass energy of sqrt(s) = 1.96 TeV. The new Tevatron combination using up to 2.8 fb-1 of data results in a preliminary world average mass of the top quark of m_top = 172.4 +- 1.2 GeV. This corresponds to a relative precision of 0.7%.
An overview of recent experimental searches for SUSY particles is presented. These searches are based on data collected by the CDF and the \D0 experiments operating at the Fermilab Tevatron proton-antiproton collider with $\sqrt{s}$ = 1.96 TeV. The review focuses on searches for squarks and gluinos in final states with missing transverse energy and jets. Emphasis will be given to the search for the gluino decaying into a sbottom and $b$ quark with each sbottom decaying into a $b$ quark and a neutralino. This scenario yields events containing 4 $b$-jets and missing transverse energy.
We combine searches by the CDF and D0 Collaborations for the associated production of a Higgs boson with a W or Z boson and subsequent decay of the Higgs boson to a bottom-antibottom quark pair. The data, originating from Fermilab Tevatron p-pbar collisions at sqrt{s}=1.96 TeV, correspond to integrated luminosities of up to 9.7 fb^-1. The searches are conducted for a Higgs boson with mass in the range 100-150 GeV/c^2. We observe an excess of events in the data compared with the background predictions, which is most significant in the mass range between 120 and 135 GeV/c^2. The largest local si…
Direct measurements of the trilinear gauge boson couplings by the CDF and D0 collaborations at Fermilab are reviewed. Limits on the anomalous couplings were obtained at a 95 % CL from four diboson production processes: W-gamma production with the subsequent W boson decay to e-nu or mu-nu, WW production with both the W boson decaying to e-nu or mu-nu, WW/WZ production with one of the gauge bosons decaying leptonically and the other gauge boson decaying to two jets, and Z-gamma production with the subsequent Z boson decay to e-e, mu-mu, or nu-nu. Limits were also obtained by a combined fit to W-…
In topcolor assisted technicolor, topgluons are massive gluons which couple mainly to top and bottom quarks. We estimate the mass reach for topgluons decaying to t anti-t at the Tevatron as a function of integrated luminosity. The mass reach for topgluons decreases with increasing topgluon width, and is 1.0 - 1.1 TeV for Run II (2 fb^-1) and 1.3-1.4 TeV for TeV33 (30 fb^-1).
In topcolor assisted technicolor, topgluons are massive gluons which couple mainly to top and bottom quarks. We estimate the mass reach for topgluons decaying to b anti-b at the Tevatron as a function of integrated luminosity. The mass reach for topgluons decreases with increasing topgluon width, and is 0.77 - 0.95 TeV for Run II (2 fb^-1) and 1.0-1.2 TeV for TeV33 (30 fb^-1).
We present a search for neutral supersymmetric Higgs bosons decaying to tau+tau- pairs produced in ppbar collisions at sqrt{s}=1.96 TeV. The data have been collected with the CDF II and D0 detectors at the Tevatron collider at Fermilab (1 fb^-1 of integrated luminosity per experiment). No significant excess above the standard model backgrounds is observed. We set exclusion limits on the Higgs production cross-section times the branching fraction of its decay to tau+tau- pairs for Higgs masses in the range from 90 to 250 GeV/c^2. We also set exclusion limits on MSSM parameters m_A and tan_beta …
We make a Monte Carlo study on compositeness of first generation quarks and leptons using the Drell-Yan distribution in the high dielectron mass region at the Tevatron and LHC energies. The current experimental lower limits on the compositeness scale, Λ, vary from 2.5 to 6.1 TeV. In the present analysis, we assume that there will be no deviation of the dielectron mass spectrum from Standard Model prediction at center of mass energy 2 TeV (Tevatron) and 14 TeV (LHC). We then find that in the LL, RR, RL and LR chirality channels of the quark-electron currents, it is possible to extend the lower …
Recent results obtained by the CDF and D0 collaborations are presented here. These Tevatron Higgs searches look for a Standard Model (SM) Higgs boson decaying into W-boson pairs, with the W-bosons decaying into electron-neutrino or muon neutrino final states. In the mass range of 135 GeV/c2 to 200 Gev/c2, the SM Higgs decays prominently into W-boson pairs. The presented results are based on an integrated luminosity that ranges from 3.0 to 4.2 fb-1. No significant excess over expected background is observed and the 95% CL limits are set for a Standard Model (SM) Higgs boson for different mass h…
The phenomenology of the electroweak symmetry breaking sector is expected to involve resonances decaying preferentially into heavy fermions. Three recent CDF analyses are reviewed and used to constrain Higgs and Technicolor models.
We report a measurement of the fraction of top quark pair events produced via gluon-gluon fusion in $p\bar{p}$ collisions at $\sqrt{s} = 1.96 ~\rm TeV$ in lepton+jets final states using the full RunII data set corresponding to $9.7 ~\rm fb^{-1}$ of integrated luminosity collected by the DØ experiment. We utilize a boosted decision tree to distinguish top quark pair events produced by $q\bar{q}$ annihilation and $gg$ fusion. We perform a template fit to extract the $t\bar{t}$ production fraction via $gg$ fusion and find $f_{gg} = 0.096 \pm 0.039 ~(\rm stat.) ~^{+0.077}_{-0.062} ~(\rm syst.)$.
n this letter we investigate the various processes that can contribute to a final state consisting of a lepton, missing transverse momentum and two jets at Next to Leading Order (NLO) at the Tevatron. In particular we consider the production of W/Z + 2 jets, diboson pairs, single top and the tt process with both fully leptonic and semi-leptonic decays. We present distributions for the invariant mass of the dijet system and normalisations of the various processes, accurate to NLO.
Drell-Yan lepton pairs produced in the process $p \bar{p} \rightarrow \ell^+\ell^- + X$ through an intermediate $γ^*/Z$ boson have an asymmetry in their angular distribution related to the spontaneous symmetry breaking of the electroweak force and the associated mixing of its neutral gauge bosons. The CDF and D0 experiments have measured the effective-leptonic electroweak mixing parameter $\sin^2θ^{\rm lept}_{\rm eff}$ using electron and muon pairs selected from the full Tevatron proton-antiproton data sets collected in 2001-2011, corresponding to 9-10 fb$^{-1}$ of integrated luminosity. The c…
A search is performed for heavy resonances decaying to two long-lived massive neutral particles, each decaying to leptons. The experimental signature is a distinctive topology consisting of a pair of oppositely charged leptons originating at a separated secondary vertex. Events were collected by the CMS detector at the LHC during pp collisions at sqrt(s) = 7 TeV, and selected from data samples corresponding to 4.1 (5.1) inverse femtobarns of integrated luminosity in the electron (muon) channel. No significant excess is observed above standard model expectations, and an upper limit is set with …
We present results of a search for for the anomalous production of events containing a high-transverse momentum charged lepton (electron or muon) and photon, accompanied by missing transverse energy (MET), and/or additional leptons and photons, and jets (X). We use the same kinematic selection criteria as in a previous CDF search, but with a substantially larger data set, 305pb-1, a ppbar collision energy of 1.96 TeV, and the upgraded CDF II detector. We find 42 Lepton + Photon + MET events versus a standard model expectation of 37.3 +- 5.4 events. The level of excess observed in Run I, 16 eve…
We present a search for high-mass resonances decaying into two leptons of different flavor: $eμ$, $eτ$ and $μτ$. These resonances are predicted by several models for Physics Beyond the Standard Model, such as R-parity-violating MSSM. The search is based on 1 ${\rm fb^{-1}}$ of Tevatron Run II data collected with the CDF detector at $\sqrt{s}$ = 1.96 TeV in proton anti-proton collisions.
A search for a standard model Higgs boson decaying into a pair of tau leptons is performed using events recorded by the CMS experiment at the LHC in 2011 and 2012. The dataset corresponds to an integrated luminosity of 4.9 inverse femtobarns at a centre-of-mass energy of 7 TeV and 19.7 inverse femtobarns at 8 TeV. Each tau lepton decays hadronically or leptonically to an electron or a muon, leading to six different final states for the tau-lepton pair, all considered in this analysis. An excess of events is observed over the expected background contributions, with a local significance larger t…
We review the measurements of the top quark mass by the CDF and D-Zero collaborations using Run I data in excess of 100 inverse picobarns. The D-Zero collaboration has recently updated its measurement of the top quark mass in the lepton + jets channel. The world average of the top quark mass from the CDF and D-Zero measurements in the lepton + jets channel now stands at 175.6 +/- 5.5 GeV/c**2.
The search for the Standard Model Higgs boson in the four lepton (electron and muon) final state with the ATLAS detector at the LHC is presented. The analysis strategy and the efficiency for selecting the signal and rejecting the background are discussed, focusing on the performance of the lepton identification that can be achieved with the first data of LHC expected in 2008.
The Higgs and some of the Standard Model superpartners may have been copiously produced at LEP and the Tevatron without being detected. We study a novel scenario of this type in which the Higgs decays predominantly into a light hidden sector either directly or through light SUSY states. Subsequent cascades increase the multiplicity of hidden sector particles which, after decaying back into the Standard Model, appear in the detector as clusters of collimated leptons known as lepton jets. We identify the relevant collider observables that characterize this scenario, and study a wide range of LEP…
CDF Run II data for the underlying event associated with Drell-Yan lepton pair production are examined as a function of the lepton-pair transverse momentum. The data are compared with a previous analysis on the behavior of the underlying event in high transverse momentum jet production and also with several other QCD Monte-Carlo models. The goal is to provide data that can be used to tune and improve the QCD Monte-Carlo models of the underlying event, which is especially important now in view of the LHC startup.
The CDF and \D0 collaborations have used recent data taken at the Tevatron to perform QCD tests with $W$ and $Z$ bosons decaying leptonically. \D0 measures the production cross section times branching ratio for $W$ and $Z$ bosons. This also gives an indirect measurement of the total width of the $W$ boson: $\gw=2.126\pm0.092 GeV$. CDF reports on a direct measurement of $\gw=2.19\pm0.19 GeV$, in good agreement with the indirect determination and Standard Model predictions. \D0's measurement of the differential $dσ/dp_T$ distribution for $W$ and $Z$ bosons decaying to electrons agrees with the c…
We have analyzed the supersymmetric tri-lepton signals for sparticle searches at the Tevatron in the minimal supersymmetric standard model with general CP phases without generational mixing. The CP phases may affect very strongly the chargino and neutralino mass spectrums and $σ(p\bar{p}\to\tildeχ^-_1\tildeχ^0_2)$ as well as ${\cal B}(\tildeχ^-_1\to\tildeχ^0_1\ell^-ν)$ and ${\cal B}(\tildeχ^0_2\to\tildeχ^0_1\ell^+\ell^-)$. Even under the stringent constraints from the electron electric dipole moment the CP phases can lead to a minimum of the tri-lepton event rate for their non-trivial values.
This Letter presents a search for pair production of heavy down-type quarks decaying via b'->Wt in the lepton + jets channel, as b'b'->WtWt->bbWWWW->lvbbqqqqqq. In addition to requiring exactly one lepton, large missing transverse momentum and at least six jets, the invariant mass of nearby jet pairs is used to identify high transverse momentum W bosons. In data corresponding to an integrated luminosity of 1.04 fb^-1 from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector, a heavy down-type quark with mass less than 480 GeV is excluded at the 95% confidence level.
A search is presented for a singly produced third-generation scalar leptoquark decaying to a $τ$ lepton and a bottom quark. Associated production of a leptoquark and a $τ$ lepton is considered, leading to a final state with a bottom quark and two $τ$ leptons. The search uses proton-proton collision data at a center-of-mass energy of 13 TeV recorded with the CMS detector, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Upper limits are set at 95% confidence level on the production cross section of the third-generation scalar leptoquarks as a function of their mass. From a compariso…
Hadronically decaying tau leptons are of prime importance in numerous physics analyses in ATLAS. The spectrum of the possible applications of hadronically decaying tau leptons reaches from Standard Model measurements, including Higgs searches, to searches for physics beyond the Standard Model. The basic principles behind the sophisticated tau reconstruction and identification techniques, which are specifically designed to identify hadronically decaying taus and reject various background processes, are delineated here along with current data-driven estimates of their respective performance.
A search for heavy leptons decaying to a $Z$ boson and an electron or a muon is presented. The search is based on $pp$ collision data taken at $\sqrt{s}=8$ TeV by the ATLAS experiment at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb$^{-1}$. Three high-transverse-momentum electrons or muons are selected, with two of them required to be consistent with originating from a $Z$ boson decay. No significant excess above Standard Model background predictions is observed, and 95% confidence level limits on the production cross section of high-mass trilepton resona…
The presence of tau leptons in the final state is an important signature in many Higgs boson and SUSY searches. With the ATLAS detector, hadronically decaying tau leptons can be reconstructed in a wide range of transverse energies. The reconstruction algorithm for hadronically decaying tau leptons is explained and the performance of tau lepton identification is shown. Particularly important is the discrimination of hadronically decaying tau leptons against overwhelming backgrounds from QCD jets.
Recent results of searches for new phenomena using data collected in Run I by the CDF and D0 experiments are presented. D0 set limits for top squarks decaying into b+l+sneutrino significantly beyond the reach of previous analyses in this channel (m_stop>140GeV at 95% C.L. for m_snu=45GeV). CDF exclude top squarks decaying into b+tau for masses below 111GeV. In addition, D0 have analyzed photon and electron pair production to search for effects of large extra dimensions. No evidence is found, resulting in limits on the effective Planck scale of 1.1 TeV. Finally, D0 have used a model-independent…
We present a study of rates and kinematical properties of lepton pairs contained in central jets with transverse energy E_T > 15 GeV that are produced at the Fermilab Tevatron collider. We compare the data to a QCD prediction based on the HERWIG and QQ Monte Carlo generator programs.We find that the data are poorly described by the simulation, in which sequential semileptonic decays of single b quarks (b --> l c X with c --> l s X) are the major source of such lepton pairs.
A search for high-mass resonances decaying into tau-lepton pairs is performed using a data sample of pp collisions at sqrt(s) = 7 TeV. The data were collected with the CMS detector at the LHC and correspond to an integrated luminosity of 4.9 inverse femtobarns. The number of observed events is in agreement with the standard model prediction. An upper limit on the product of the resonance cross section and branching fraction into tau-lepton pairs is calculated as a function of the resonance mass. Using the sequential standard model resonance Z'(SSM) and the superstring-inspired E(6) model with …
A search for the standard model Higgs boson decaying to W+W- in pp collisions at sqrt(s) = 7 TeV is reported. The data are collected at the LHC with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. The W+W- candidates are selected in events with two charged leptons and large missing transverse energy. No significant excess of events above the standard model background expectations is observed, and upper limits on the Higgs boson production relative to the standard model Higgs expectation are derived. The standard model Higgs boson is excluded in the mass …
An overview of latest top quark pair production cross-sections measured at the Tevatron is given. These measurements have been carried out in the dilepton, lepton+jets and all-jets channels with an integrated luminosity of about 1fb-1. The measurements are consistent with NNLO calculations.
A search for pair production of third-generation scalar leptoquarks decaying into a top quark and a $τ$-lepton is presented. The search is based on a dataset of $pp$ collisions at $\sqrt{s}=13$ TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb$^{-1}$. Events are selected if they have one light lepton (electron or muon) and at least one hadronically decaying $τ$-lepton, or at least two light leptons. In addition, two or more jets, at least one of which must be identified as containing $b$-hadrons, are required. Si…
A search for supersymmetric partners of quarks is performed in the topology of multijet events accompanied by at least one tau lepton decaying hadronically and large missing transverse energy. Approximately 1 fb-1 of ppbar collision data from the Fermilab Tevatron Collider at a center of mass energy of 1.96 TeV recorded by the D0 detector is analyzed. Results are combined with the previously published D0 inclusive search for squarks and gluinos. No evidence of physics beyond the standard model is found and lower limits on the squark mass up to 410 GeV are derived in the framework of minimal su…
The ATLAS detector at the LHC is used to search for high-mass states, such as heavy charged gauge bosons (W'), decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of pp collisions at a centre-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.7 fb-1. No excess beyond Standard Model expectations is observed. A W' with Sequential Standard Model couplings is excluded at the 95% credibility level for masses up to 2.55 TeV. Excited chiral bosons (W*) with equivalent coupling strength are excluded for masses up to 2.42 TeV.
The ATLAS detector at the LHC is used to search for high-mass states, such as heavy charged gauge bosons (W'), decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 1.04 fb^-1. No excess beyond Standard Model expectations is observed. A W' with Sequential Standard Model couplings is excluded at the 95% confidence level for masses up to 2.15 TeV.
The construction of the ILC tangential to Tevatron ring will give opportunity to investigate electron-proton, positron-proton, electron-antiproton, positron-antiproton interactions at 1 TeV center of mass energy. The analysis of the lepton-hadron collisions in these energy region is very important both for understanding of strong interaction dynamics and for adequate interpretation of future LHC and VLHC data. In addition, ILC-Tevatron collider will provide a possibility to realize photon-hadron collisions in the same energy region using Compton backscattered laser photon off ILC electron beam…
We present the results of searches for the Standard Model Higgs boson decaying predominantly to WW pairs, at a center-of-mass energy of sqrt(s)=1.96 TeV, using up to 8.2 fb^{-1} of data collected with the CDF and D0 detectors at the Fermilab Tevatron collider. The analysis techniques and the various channels considered are discussed. These searches result in exclusions across the Higgs mass range of 156.5<mH<173.7 GeV for CDF and 161<mH<170 GeV for D0.
A search for heavy narrow resonances decaying into four-lepton final states from cascade decays of a Z' boson has been performed using proton-proton collision data at sqrt(s) = 8 TeV collected by the CMS experiment, corresponding to an integrated luminosity of 19.7 inverse femtobarns. No excess of events over the standard model background expectation is observed. Upper limits for a benchmark model on the product of cross section and branching fraction for the production of these heavy narrow resonances are presented. The limit excludes leptophobic Z' bosons with masses below 2.5 TeV within the…
A search is performed in proton-proton collisions at sqrt(s) = 8 TeV for exotic particles decaying via WZ to fully leptonic final states with electrons, muons, and neutrinos. The data set corresponds to an integrated luminosity of 19.5 inverse femtobarns. No significant excess is observed above the expected standard model background. Upper bounds at 95% confidence level are set on the production cross section of a W' boson as predicted by an extended gauge model, and on the W'WZ coupling. The expected and observed mass limits for a W' boson, as predicted by this model, are 1.55 and 1.47 TeV, r…
A search is performed for a new resonance decaying into a lighter resonance and a Z boson. Two channels are studied, targeting the decay of the lighter resonance into either a pair of oppositely charged tau leptons or a b b-bar pair. The Z boson is identified via its decays to electrons or muons. The search exploits data collected by the CMS experiment at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.8 inverse femtobarns. No significant deviations are observed from the standard model expectation and limits are set on production cross sections and parameters …
A search for neutral Higgs bosons in the minimal supersymmetric extension of the standard model (MSSM) decaying to tau-lepton pairs in pp collisions is performed, using events recorded by the CMS experiment at the LHC. The dataset corresponds to an integrated luminosity of 24.6 inverse femtobarns, with 4.9 inverse femtobarns at 7 TeV and 19.7 inverse femtobarns at 8 TeV. To enhance the sensitivity to neutral MSSM Higgs bosons, the search includes the case where the Higgs boson is produced in association with a b-quark jet. No excess is observed in the tau-lepton-pair invariant mass spectrum. E…
Searches for the direct electroweak production of supersymmetric charginos, neutralinos, and sleptons in a variety of signatures with leptons and W, Z, and Higgs bosons are presented. Results are based on a sample of proton-proton collision data collected at center-of-mass energy sqrt(s) = 8 TeV with the CMS detector in 2012, corresponding to an integrated luminosity of 19.5 inverse femtobarns. The observed event rates are in agreement with expectations from the standard model. These results probe charginos and neutralinos with masses up to 720 GeV, and sleptons up to 260 GeV, depending on the…
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${^2}$.
A search for heavy resonances that decay to tau lepton pairs is performed using proton-proton collisions at sqrt(s) = 13 TeV. The data were collected with the CMS detector at the CERN LHC and correspond to an integrated luminosity of 2.2 inverse femtobarns. The observations are in agreement with standard model predictions. An upper limit at 95% confidence level on the product of the production cross section and branching fraction into tau lepton pairs is calculated as a function of the resonance mass. For the sequential standard model, the presence of Z' bosons decaying into tau lepton pairs i…
Several models of physics beyond the Standard Model predict neutral particles that decay into final states consisting of collimated jets of light leptons and hadrons (so-called "lepton jets"). These particles can also be long-lived with decay length comparable to, or even larger than, the LHC detectors' linear dimensions. This paper presents the results of a search for lepton jets in proton--proton collisions at the centre-of-mass energy of $\sqrt{s}$ = 8 TeV in a sample of 20.3 fb$^{-1}$ collected during 2012 with the ATLAS detector at the LHC. Limits on models predicting Higgs boson decays t…
We present a study of top quark polarization in $t \overline{t}$ events produced in $p \overline{p}$ collisions at $\sqrt{s}=1.96$ TeV. Data correspond to 9.7 fb$^{-1}$ collected with the D0 detector at the Tevatron. We use final states containing a lepton and at least three jets. The polarization is measured using the distribution of leptons along the beam and helicity axes, and the axis normal to the production plane. This is the first measurement of top quark polarization at the Tevatron in $\ell$+jets final states, and first measurement of transverse polarization in $t \overline{t}$ produc…
A search for a new high-mass resonance decaying to a tau lepton and a neutrino is reported. The analysis uses proton-proton collision data collected by the CMS experiment at the LHC at $\sqrt{s} =$ 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The search utilizes hadronically decaying tau leptons. No excess in the event yield is observed at high transverse masses of the $τ$ and missing transverse momentum. An interpretation of results within the sequential standard model excludes W' boson masses below 4.0 TeV at 95% confidence level. Existing limits are also improved on …
We present a more detailed account of our study (hep-ph/9903238) for the supersymmetry reach of the Tevatron in channels with isolated leptons and identified tau jets. We review the theoretical motivations for expecting such signatures, and describe the relevant parameter space in the minimal supergravity and the minimal gauge-mediated models. With explicit Monte Carlo simulations we then show that for certain parameter ranges, channels with two leptons and one tau jet offer a better reach in Run II than the clean trilepton signal. We emphasize than improving on tau ID is an important prerequi…
The most recent results of the top-quark mass measurements at the Tevatron at Fermilab are presented. Data were collected in proton-antiproton collisions at sqrt{s}=1.96 TeV by the CDF and D0 experiments. Top quark mass measurements in the lepton+jets, dilepton and alljet final states as well as their combination and the extraction of the mass from the cross-section measurement are presented.
A measurement of the cross section of top quark pair production in proton-proton collisions recorded with the ATLAS detector at the LHC at a centre-of-mass energy of 7 TeV is reported. The data sample used corresponds to an integrated luminosity of 2.05 fb^-1. Events with an isolated electron or muon and a tau lepton decaying hadronically are used. In addition, a large missing transverse momentum and two or more energetic jets are required. At least one of the jets must be identified as originating from a b quark. The measured cross section, sigma_ttbar = 186+/- 13 (stat) +/- 20 (syst) +/- 7 (…
Searching for vector-like leptons decaying into an electron and missing transverse energy in e$^{+}$e$^{-}$ collisions with $\sqrt{s} = 240$ GeV at the FCC-ee
Centre for Theoretical Physics, The British University in Egypt（埃及英国大学理论物理中心）
This paper describes the trigger and offline reconstruction, identification and energy calibration algorithms for hadronic decays of tau leptons employed for the data collected from $pp$ collisions in 2012 with the ATLAS detector at the LHC center-of-mass energy $\sqrt{\mathrm{s}} = 8$ TeV. The performance of these algorithms is measured in most cases with $Z$ decays to tau leptons using the full 2012 dataset, corresponding to an integrated luminosity of 20.3 fb$^{-1}$. An uncertainty on the offline reconstructed tau energy scale of $2-4$%, depending on transverse energy and pseudorapidity, is…
