We search for pair production of supersymmetric top quarks (~t_1), followed by R-parity violating decay ~t_1 -> tau b with a branching ratio beta, using 322 pb^-1 of ppbar collisions at sqrt{s}=1.96 TeV collected by the CDF II detector at Fermilab. Two candidate events pass our final selection criteria, consistent with the standard model expectation. We set upper limits on the cross section sigma(~t_1 ~tbar_1)*beta^2 as a function of the stop mass m(~t_1). Assuming beta=1, we set a 95% confidence level limit m(~t_1)>153 GeV/c^2. The limits are also applicable to the case of a third generation scalar leptoquark (LQ_3) decaying LQ_3 -> tau b.
We present a search for tau sneutrino production using the Tevatron ppbar collision data collected with the CDF II detector and corresponding to an integrated luminosity of 1 fb^-1. We focus on the scenarios predicted by the R-parity violating (RPV) supersymmetric models in which tau sneutrinos decay to two charged leptons of different flavor. With the data consistent with the standard model expectations, we set the upper limits on sigma(ppbar -> tau sneutrino)*BR(tau sneutrino ->emu,mutau,etau) and use these results to constrain the RPV couplings as a function of tau sneutrino mass.
We present a search for the production of neutral Higgs bosons phi decaying into tau+tau- final states in ppbar collisions at a center-of-mass energy of 1.96 TeV. The data, corresponding to an integrated luminosity of approximately 1 fb-1, were collected by the D0 experiment at the Fermilab Tevatron Collider. Limits on the production cross section times branching ratio are set. The results are interpreted in the minimal supersymmetric standard model yielding limits that are the most stringent to date at hadron colliders.
We describe a general search for resonances decaying to a neutral e-mu final state in ppbar collisions at a center-of-mass energy of 1.96 TeV. Using a data sample representing 344 pb^-1 of integrated luminosity recorded by the CDF-II experiment, we compare Standard Model predictions with the number of observed events for invariant masses between 50 and 800 GeV/c^2. Finding no significant excess (5 events observed vs. 7.7 +/- 0.8 expected for e-mu invariant masses > 100 GeV/c^2), we set limits on sneutrino and Z' masses as functions of lepton family number violating couplings.
We present a measurement of the cross section for Z boson production times the branching fraction to tau lepton pairs sigma(ppbar -> Z + X) Br(Z -> tau+ tau-) in proton-antiproton collisions at center of mass energy 1.96 TeV. The measurement is performed in the channel in which one tau lepton decays into a muon and neutrinos, and the other tau lepton decays hadronically or into an electron and neutrinos. The data sample corresponds to an integrated luminosity of 1.0 inverse fb collected with the D0 detector at the Fermilab Tevatron Collider. The sample contains 1511 candidate events with an es…
Using data corresponding to an integrated luminosity of 1.3 fb^-1, we observe a narrow mass state decaying into Upsilon(1S)+gamma, where the Upsilon(1S) meson is detected by its decay into a pair of oppositely charged muons, and the photon is identified through its conversion into an electron-positron pair. The significance of this observation is 5.6 standard deviations. The mass of the state is centered at 10.551 \pm 0.014 (stat.) \pm 0.017 (syst.) GeV/c^2, which is consistent with that of the state recently observed by the ATLAS Collaboration.
We present the results of a search for doubly-charged Higgs bosons (H+/-+/-) decaying to dileptons using ~240/pb of ppbar collision data collected by the CDF II experiment at the Fermilab Tevatron. In our search region, given by same-sign dilepton mass m_ll' > 80 GeV/c^2 (100 GeV/c^2 for dielectron channel), we observe no evidence for doubly-charged Higgs production. We set limits on sigma (ppbar --> H++H-- --> l+l+l-l-) as a function of the mass of the doubly-charged Higgs boson and the chirality of its couplings. Assuming exclusive same-sign dilepton decays, we derive lower mass limits on H+…
We present a search for a narrow scalar or vector resonance decaying into Zgamma with a subsequent Z decay into a pair of electrons or muons. The data for this search were collected with the D0 detector at the Fermilab Tevatron ppbar collider at a center of mass energy sqrt(s) = 1.96 TeV. Using 1.1 (1.0) fb-1 of data, we observe 49 (50) candidate events in the electron (muon) channel, in good agreement with the standard model prediction. From the combination of both channels, we derive 95% C.L. upper limits on the cross section times branching fraction (sigma x B) into Zgamma. These limits ran…
We present a search for pair production of doubly-charged Higgs bosons in the processes qqbar to H++H-- decaying through H++/-- to tau tau, muon tau, muon muon. The search is performed in ppbar collisions at a center-of-mass energy of sqrt{s}=1.96 TeV using an integrated luminosity of 7.0 fb-1 collected by the D0 experiment at the Fermilab Tevatron Collider. The results are used to set 95% C.L. limits on the pair production cross section of doubly-charged Higgs bosons and on their mass for different H++/-- branching fractions. Models predicting different H++/-- decays are investigated. Assumin…
We report on a first search for production of the lightest neutral CP-even Higgs boson (h) in the next-to-minimal supersymmetric standard model, where h decays to a pair of neutral pseudoscalar Higgs bosons (a), using 4.2/fb of data recorded with the D0 detector at Fermilab. The a bosons are required to either both decay to mu^+mu^- or one to mu^+mu^- and the other to tau^+tau^-. No significant signal is observed, and we set limits on its production as functions of M_a and M_h.
We report on a first search for resonant pair production of neutral long-lived particles (NLLP) which each decay to a bbbar pair, using 3.6 fb^-1 of data recorded with the D0 detector at the Fermilab Tevatron collider. We search for pairs of displaced vertices in the tracking detector at radii in the range 1.6--20 cm from the beam axis. No significant excess is observed above background, and upper limits are set on the production rate in a hidden-valley benchmark model for a range of Higgs boson masses and NLLP masses and lifetimes.
We describe a search for production of a charged Higgs boson, q \bar{q'} -> H^+, reconstructed in the t\bar{b} final state in the mass range 180 <= M_{H^+} <= 300 GeV. The search was undertaken at the Fermilab Tevatron collider with a center-of-mass energy sqrt{s} = 1.96 TeV and uses 0.9 fb^{-1} of data collected with the D0 detector. We find no evidence for charged Higgs boson production and set upper limits on the production cross section in the Types I, II and III two-Higgs-doublet models (2HDMs). An excluded region in the (M_{H^+},tanβ) plane for Type I 2HDM is presented.
Using data from 2.9/fb of integrated luminosity collected with the CDF II detector at the Tevatron, we search for resonances decaying into a pair of on-shell gauge bosons, WW or WZ, where one W decays into an electron and a neutrino, and the other boson decays into two jets. We observed no statistically significant excess above the expected standard model background, and we set cross section limits at 95% confidence level on G*(Randall-Sundrum graviton), Z', and W' bosons. By comparing these limits to theoretical cross sections, mass exclusion regions for the three particles are derived. The m…
We present the results of a search for new particles decaying to tau pairs using the data corresponding to an integrated luminosity of 195 pb^-1 collected from March 2002 to September 2003 with the CDF detector at the Tevatron. Hypothetical particles, such as Zprime and MSSM Higgs bosons can potentially produce the tau pair final state. We discuss the method of tau identification, and show the signal acceptance versus new particle mass. The low-mass region, dominated by Z -> tau tau, is used as a control region. In the high-mass region, we expect 2.8 +/- 0.5 events from known background source…
We report results from a search for neutral Higgs bosons produced in association with b quarks using data recorded by the D0 experiment at the Fermilab Tevatron Collider and corresponding to an integrated luminosity of 7.3 fb-1. This production mode can be enhanced in several extensions of the standard model (SM) such as in its minimal supersymmetric extension (MSSM) at high tanBeta. We search for Higgs bosons decaying to tau pairs with one tau decaying to a muon and neutrinos and the other to hadrons. The data are found to be consistent with SM expectations, and we set upper limits on the cro…
We measure the Lambda_b^0 lifetime in the fully reconstructed decay Lambda_b^0 -> J/psi Lambda^0 using 10.4 fb^-1 of ppbar collisions collected with the D0 detector at sqrt(s)=1.96 TeV. The lifetime of the topologically similar decay channel B^0 -> J/psi K^0_S is also measured. We obtain tau(Lambda_b^0) = 1.303 +- 0.075 (stat.) +- 0.035 (syst.) ps and tau(B^0) = 1.508 +- 0.025 (stat.) +- 0.043 (syst.) ps. Using these measurements, we determine the lifetime ratio of tau(Lambda_b^0)/tau(B^0) = 0.864 +- 0.052 (stat.) +- 0.033 (syst.).
We present the results of a search for standard model Higgs boson production with decay to WW*, identified through the leptonic final states e+ e- nubar nu ,e mu nubar nu and mu+ mu- nubbar nu. This search uses 360 pb-1 of data collected from p pbar collisions at sqrt{s} = 1.96 TeV by the upgraded Collider Detector at Fermilab (CDF II). We observe no signal excess and set 95% confidence level upper limits on the production cross section times branching ratio for the Higgs boson to WW* or any new scalar particle with similar decay products. These upper limits range from 5.5 to 3.2 pb for Higgs …
We present a measurement of the ttbar production cross section multiplied by the branching ratio to tau lepton decaying semihadronically plus jets, at a center of mass energy sqrt{s}=1.96 TeV using 1 fb^(-1) of integrated luminosity collected with the D0 detector. Assuming a top quark mass of 170 GeV, we measure sigma_ttb * BR=0.60^{+0.23}_{-0.22} (stat) ^{+0.15}_{-0.14} (syst) +/- 0.04\;(lumi) pb. In addition, we extract the ttbar production cross section using the ttbar->tau+jets topology, with the result sigma_ttbar = 6.9_{-1.2}^{+1.2} (stat)_{-0.7}^{+0.8} (syst) \pm 0.4 (lumi) pb. These fi…
We present a search for the production of neutral Higgs bosons decaying into tautau pairs in ppbar collisions at a center-of-mass energy of 1.96 TeV. The data, corresponding to an integrated luminosity of 5.4 fb-1, were collected by the D0 experiment at the Fermilab Tevatron Collider. We set upper limits at the 95% C.L. on the product of production cross section and branching ratio for a scalar resonance decaying into tautau pairs, and we then interpret these limits as limits on the production of Higgs bosons in the minimal supersymmetric standard model (MSSM) and as constraints in the MSSM pa…
We report on a search for the pair production of scalar leptoquarks, $LQ$, using 191 pb$^{-1}$ of proton-antiproton collision data recorded by the CDF experiment during Run II of the Tevatron. The leptoquarks are sought via their decay into a neutrino and quark yielding missing transverse energy and several jets of large transverse energy. No evidence for leptoquark production is observed, and limits are set on $σ(p\bar p\to LQ\bar{LQ} X \to ν\barνq\bar q X)$. Using a next-to-leading order theoretical prediction of the cross section for scalar leptoquark production, we exclude first-generation…
We present the result of a search for a massive color-octet vector particle, (e.g. a massive gluon) decaying to a pair of top quarks in proton-antiproton collisions with a center-of-mass energy of 1.96 TeV. This search is based on 1.9 fb$^{-1}$ of data collected using the CDF detector during Run II of the Tevatron at Fermilab. We study $t\bar{t}$ events in the lepton+jets channel with at least one $b$-tagged jet. A massive gluon is characterized by its mass, decay width, and the strength of its coupling to quarks. These parameters are determined according to the observed invariant mass distrib…
We present the results of a search for pair production of scalar top quarks in an R-parity violating supersymmetry scenario in 106 pb-1 of ppbar collisions at $\sqrt{s} = 1.8$ TeV collected by the Collider Detector at Fermilab. In this mode each scalar top quark decays into a tau lepton and a b quark. We search for events with two tau's, one decaying leptonically (e or mu) and one decaying hadronically, and two jets. No candidate events pass our final selection criteria. We set a 95% confidence level lower limit on the scalar top quark mass at 122 GeV/c2 for Br (stop-> tau + b) = 1.
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 $\ttbar$ differential cross section with respect to the $\ttbar$ invariant mass, dSigma/dMttbar, in $\ppbar$ collisions at $\sqrt{s}=1.96$ TeV using an integrated luminosity of $2.7\invfb$ collected by the CDF II experiment. The $\ttbar$ invariant mass spectrum is sensitive to a variety of exotic particles decaying into $\ttbar$ pairs. The result is consistent with the standard model expectation, as modeled by \texttt{PYTHIA} with \texttt{CTEQ5L} parton distribution functions.
We have measured the differential cross section for the inclusive production of psi(2S) mesons decaying to mu^{+} mu^{-1} that were produced in prompt or B-decay processes from ppbar collisions at 1.96 TeV. These measurements have been made using a data set from an integrated luminosity of 1.1 fb^{-1} collected by the CDF II detector at Fermilab. For events with transverse momentum p_{T} (psi(2S)) > 2 GeV/c and rapidity |y(psi(2S))| < 0.6 we measure the integrated inclusive cross section sigma(ppbar -> psi(2S)X) Br(psi(2S) -> mu^{+} mu^{-}) to be 3.29 +- 0.04(stat.) +- 0.32(syst.) nb.
We report on a search for charge-1/3 third-generation leptoquarks (LQ) produced in ppbar collisions at sqrt(s)=1.96 TeV using the D0 detector at Fermilab. Third generation leptoquarks are assumed to be produced in pairs and to decay to a tau neutrino and a b quark with branching fraction B. We place upper limits on sigma(ppbar->LQLQbar)*B^2 as a function of the leptoquark mass M_{LQ}. Assuming B=1, we exclude at the 95% confidence level third-generation scalar leptoquarks with M_{LQ} < 229 GeV.
Inclusive jet cross sections in Z/gamma^* events, with Z/gamma^* decaying into an electron-positron pair, are measured as a function of jet transverse momentum and jet multiplicity in ppbar collisions at sqrt{s} = 1.96 TeV with the upgraded Collider Detector at Fermilab in Run II, based on an integrated luminosity of 1.7 fb^-1. The measurements cover the rapidity region | yjet | < 2.1 and the transverse momentum range ptjet > 30 GeV/c. Next-to-leading order perturbative QCD predictions are in good agreement with the measured cross sections.
A search for leptoquarks has been performed in 310 pb-1 of data from ppbar collisions at a center-of-mass energy of 1.96 TeV, collected by the D0 detector at the Fermilab Tevatron Collider. The topology analyzed consists of acoplanar jets with missing transverse energy. The data show good agreement with standard model expectations, and a lower mass limit of 136 GeV has been set at the 95% C.L. for a scalar leptoquark decaying exclusively into a quark and a neutrino.
Inclusive jet cross sections in Z/γ^* events, with Z/γ^* decaying into an electron-positron pair, are measured as a function of jet transverse momentum and jet multiplicity in ppbar collisions at sqrt{s} = 1.96 TeV with the upgraded Collider Detector at Fermilab in Run II, based on an integrated luminosity of 2.5 fb-1. The measurements cover the rapidity region |yjet | < 2.1 and the transverse momentum range ptjet > 30 GeV/c. Next-to-leading order perturbative QCD predictions are in good agreement with the measured cross sections.
We report the results of a search for R parity violating (RPV) interactions leading to the production of supersymmetric sneutrinos decaying into emu final states using 5.3 fb^-1 of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. Having observed no evidence for production of emu resonances, we set direct bounds on the RPV couplings lambda^'_311 and lambda_312 as a function of sneutrino mass.
We present a search for hypothetical vector-like quarks in ppbar collisions at sqrt(s) = 1.96 TeV. The data were collected by the D0 detector at the Fermilab Tevatron Collider and correspond to an integrated luminosity of 5.4 fb^(-1). We select events with a final state composed of a W or Z boson and a jet consistent with a heavy object decay. We observe no significant excess in comparison to the background prediction and set limits on production cross sections for vector-like quarks decaying to W+jet and Z+jet. These are the most stringent mass limits for electroweak single vector-like quark …
We report the results of a search for a heavy neutral gauge boson Z' decaying into the dielectron final state using data corresponding to an integrated luminosity of 5.4 fb-1 collected by the D0 experiment at the Fermilab Tevatron Collider. No significant excess above the standard model prediction is observed in the dielectron invariant-mass spectrum. We set 95% C.L. upper limits on σ(ppbar -> Z') X BR(Z' -> ee) depending on the dielectron invariant mass. These cross section limits are used to determine lower mass limits for Z' bosons in a variety of models with standard model couplings and va…
We report on a search for narrow-width particles decaying to a top and antitop quark pair. The data set used in the analysis corresponds to an integrated luminosity of 680 pb^{-1} collected with the Collider Detector at Fermilab in Run II. We present 95% confidence level upper limits on the cross section times branching ratio. Assuming a specific topcolor-assisted technicolor production model, the leptophobic Z' with width Γ_{Z'}=0.012M_{Z'}, we exclude the mass range M_{Z'} < 725 GeV/c^2 at the 95% confidence level.
We describe a search for the standard model Higgs boson with a mass of 105 GeV/c^2 to 145 GeV/c^2 in data corresponding to an integrated luminosity of approximately 450 pb^{-1} collected with the D0 detector at the Fermilab Tevatron ppbar collider at a center-of-mass energy of 1.96 TeV. The Higgs boson is required to be produced in association with a Z boson, and the Z boson is required to decay to either electrons or muons with the Higgs boson decaying to a bbbar pair. The data are well described by the expected background, leading to 95% confidence level cross section upper limits sigma(\ppb…
A direct measurement of the total decay width of the W boson G_W is presented using 350 pb-1 of data from ppbar collisions at sqrt(s) = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. The width is determined by normalizing predicted signal and background distributions to 230185 W candidates decaying to enu and munu in the transverse-mass region 50 < M_T < 90 GeV and then fitting the predicted shape to 6055 events in the high-M_T region, 90 < M_T < 200 GeV. The result is G_W = 2032 +/- 45 (stat.) +/- 57 (syst.) MeV, consistent with the standard model expectation.
We present a measurement of the top quark pair production cross section in ppbar collisions at \sqrt{s}=1.96 TeV using approximately 1 fb^{-1} of data collected with the D0 detector. We consider decay channels containing two high pt charged leptons where one lepton is identified as an electron or a muon while the other lepton can be an electron, a muon or a hadronically decaying tau lepton. For a mass of the top quark of 170 GeV, the measured cross section is 7.5 +1.0-1.0 (stat) +0.7-0.6 (syst) +0.6-0.5 (lumi) pb. Using lepton+tau events only, we measure: σ_ttbar \times B(ttbar to ltau bbbar) …
Preliminary measurements of the cross-section for the processes ppbar --> W --> mu nu, e nu; ppbar --> Z --> mu mu, e e, tau tau from the D0 detector are presented. Integrated luminosities for these data samples are 96 pb-1 for W --> mu nu, 177.3 pb-1 for W --> e nu and Z --> e e, 148pb-1 for Z --> mu mu and 207 pb-1 for Z --> tau tau. A measurement of the muon charge asymmetry from W boson decays (integrated luminosity 230 pb-1) and Z/gamma* --> e e inclusive differential cross section as a function of boson rapidity (integrated luminosity 337 pb-1) are presented as well. The results are in g…
The article describes the identification of hadronically decaying tau leptons in ppbar collisions at 1.96 TeV collected by the DZero detector at the Fermilab Tevatron. After a brief description of the motivations and the challenges of considering tau leptons in high energy hadronic collisions, details of the tau reconstruction and identification will be discussed. The challenges associated for tau energy measurements in an hadronic environment will be presented including approaches to deal with such measurements.
We report the results of a search for pair production of scalar bottom quarks (sbottom) and scalar third-generation leptoquarks in 5.2 fb-1 of ppbar collisions at the D0 experiment of the Fermilab Tevatron Collider. Scalar bottom quarks are assumed to decay to a neutralino and a $b$ quark, and we set 95% C.L. lower limits on their production in the (m_sbottom, m_neutralino) mass plane such as m_sbottom>247 GeV for m_neutralino=0 and m_neutralino>110 GeV for 160<m_sbottom<200 GeV. The leptoquarks are assumed to decay to a tau neutrino and a $b$ quark, and we set a 95% C.L. lower limit of 247 Ge…
We report on a search for the process $p\bar{p}\to γ+W/Z$ with $W/Z\to q\bar{q}$ in events containing two jets and a photon at the center-of-mass energy $\sqrt{s}=1.96$ TeV, using 184 pb$^{-1}$ of data collected by the CDF II detector. A neural network event selection has been developed to optimize the rejection of the large QCD production background; it is shown that this method gives a significant improvement in both signal-to-noise ratio and signal sensitivity, as compared with an event selection based on conventional cuts. An upper limit is presented for the $γ+W/Z$ production cross sectio…
We present a search for a new heavy charged vector boson $W^\prime$ decaying to an electron-neutrino pair in $p\bar{p}$ collisions at a center-of-mass energy of $1.96\unit{TeV}$. The data were collected with the CDF II detector and correspond to an integrated luminosity of $5.3\unit{fb}^{-1}$. No significant excess above the standard model expectation is observed and we set upper limits on $σ\cdot{\cal B}(W^\prime\to eν)$. Assuming standard model couplings to fermions and the neutrino from the $W^\prime$ boson decay to be light, we exclude a $W^\prime$ boson with mass less than $1.12\unit{TeV/…
We present the results of a search for the production of an excited state of the electron, e*, in proton-antiproton collisions at sqrt(s) = 1.96 TeV. The data were collected with the D0 experiment at the Fermilab Tevatron Collider and correspond to an integrated luminosity of approximately 1 fb^-1. We search for e* in the process ppbar -> e* e, with the e* subsequently decaying to an electron plus photon. No excess above the standard model background is observed. Interpreting our data in the context of a model that describes e* production by four-fermion contact interactions and e* decay via e…
In this paper we report a measurement of the ttbar production cross section in ppbar collisions at sqrt(s)=1.96 TeV using data corresponding to an integrated luminosity of 2.2fb-1 collected with the CDF II detector at the Tevatron accelerator. We select events with significant missing transverse energy and high jet multiplicity. This measurement vetoes the presence of explicitly identified electrons and muons, thus enhancing the tau contribution of ttbar decays. Signal events are discriminated from the background using a neural network, and heavy flavor jets are identified by a secondary-verte…
We report on a study of the dijet invariant-mass distribution in events with one identified lepton, a significant imbalance in the total event transverse momentum, and two jets. This distribution is sensitive to the possible production of a new particle in association with a $W$ boson, where the boson decays leptonically. We use the full data set of proton-antiproton collisions at 1.96 TeV center-of-mass energy collected by the Collider Detector at the Fermilab Tevatron and corresponding to an integrated luminosity of 8.9 fb$^{-1}$. The data are found to be consistent with standard-model expec…
This Letter presents a search for high-mass resonances decaying into tau+tau- final states using proton-proton collisions at sqrt(s) = 7 TeV produced by the Large Hadron Collider. The data were recorded with the ATLAS detector and correspond to an integrated luminosity of 4.6 inverse femtobarns. No statistically significant excess above the Standard Model expectation is observed; 95% credibility upper limits are set on the cross section times branching fraction of Z' resonances decaying into tau+tau- pairs as a function of the resonance mass. As a result, Z' bosons of the Sequential Standard M…
We report two measurements of the top quark mass M_top using the CDF II detector at the Fermilab Tevatron in a 318 pb^-1 data sample observed in the lepton + jets final state. One method uses an event-based likelihood technique resulting in M_top = 173.2 +2.6/-2.4 (stat.) +/- 3.2 (syst.) GeV/c^2 or 173.2 +4.1/-4.0 GeV/c^2. The second method reconstructs a top quark mass in each event using the measured invariant mass of the hadronically decaying W boson to constrain the jet energy scale to obtain a value for M_top of 173.5 +3.7/-3.6 (stat.) +/- 1.3 (syst.) GeV/c^2 or 173.5 +3.9/-3.8 GeV/c^2. W…
We have searched for third generation leptoquarks (LQ3) using 1.05 inverse femtobarns of data collected with the D0 detector at the Fermilab Tevatron Collider operating at sqrt(s)=1.96 TeV. We set a 95% C.L. lower limit of 210 GeV on the mass of a scalar LQ3 state decaying solely to a b quark and a tau lepton.
A search for a heavy scalar boson H decaying into a pair of lighter standard-model-like 125 GeV Higgs bosons h and a search for a heavy pseudoscalar boson A decaying into a Z and an h boson are presented. The searches are performed on a data set corresponding to an integrated luminosity of 19.7 inverse femtobarns of pp collision data at a centre-of-mass energy of 8 TeV, collected by CMS in 2012. A final state consisting of two tau leptons and two b jets is used to search for the H to hh decay. A final state consisting of two tau leptons from the h boson decay, and two additional leptons from t…
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.
We present the results of a search for the production of an excited state of the muon, mu*, in proton antiproton collisions at sqrt s = 1.96 TeV. The data have been collected with the D0 experiment at the Fermilab Tevatron Collider and correspond to an integrated luminosity of approximately 380 pb^-1. We search for mu* in the process p pbar -> mu* mu, with the mu* subsequently decaying to a muon plus photon. No excess above the standard model expectation is observed in data. Interpreting our data in the context of a model that describes mu* production by four-fermion contact interactions and m…
We report results from a search for neutral Higgs bosons decaying to tau pairs produced in association with a b-quark in 1.2/fb of data taken from June 2006 to August 2007 with the D0 detector at Fermi National Accelerator Laboratory. The final state includes a muon, hadronically decaying tau and jet identified as coming from a $b$-quark. We set cross section times branching ratio limits on production of such neutral Higgs bosons in the mass range from 90 GeV/c^2 to 160 GeV/c^2. Exclusion limits are set at the 95% Confidence Level for several supersymmetric scenarios.
We present a search for neutral supersymmetric Higgs bosons decaying to tau pairs produced in p-pbar collisions at sqrt(s) = 1.96 TeV. The data, corresponding to 310 pb^(-1) integrated luminosity, were collected with the CDF II detector at the Tevatron collider at Fermilab. No significant excess above the standard model backgrounds is observed. We set exclusion limits on the production cross section times branching fraction to tau pairs for Higgs masses in the range from 90 to 250 GeV/c^2.
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…
This letter presents the results of a search for a heavy particle decaying into an e mu, e tau, or mu tau final state in pp collisions at sqrt(s) = 7 TeV. The data were recorded with the ATLAS detector at the LHC during 2011 and correspond to an integrated luminosity of 4.6/fb. No significant excess above the Standard Model expectation is observed, and exclusions at 95% confidence level are placed on the cross section times branching ratio for the production of an R-parity-violating supersymmetric tau sneutrino. These results considerably extend constraints from Tevatron experiments.
We present a search for the standard model Higgs boson using hadronically decaying tau leptons, in 1 inverse femtobarn of data collected with the D0 detector at the Fermilab Tevatron ppbar collider. We select two final states: tau plus missing transverse energy and b jets, and tau+ tau- plus jets. These final states are sensitive to a combination of associated W/Z boson plus Higgs boson, vector boson fusion and gluon-gluon fusion production processes. The observed ratio of the combined limit on the Higgs production cross section at the 95% C.L. to the standard model expectation is 29 for a Hig…
Observation is made of rapidity-alignment of K+K- and ppbar pairs which results from their asymmetric orientation in rapidity, with respect to the direction from primary quark to antiquark. The K+K- and ppbar data are consistent with predictions from the fragmentation string model. However, the ppbar data strongly disagree with the conventional implementation of the cluster model. The non-perturbative process of `gluon splitting to diquarks' has to be incorporated into the cluster model for it to agree with the data. Local conservation of p_T between particles nearby in rapidity (i.e., p_T com…
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.
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 …
A search for neutral MSSM Higgs bosons in pp collisions at the LHC at a center-of-mass energy of 7 TeV is presented. The results are based on a data sample corresponding to an integrated luminosity of 36 inverse picobarns recorded by the CMS experiment. The search uses decays of the Higgs bosons to tau pairs. No excess is observed in the tau-pair invariant-mass spectrum. The resulting upper limits on the Higgs boson production cross section times branching fraction to tau pairs, as a function of the pseudoscalar Higgs boson mass, yield stringent new bounds in the MSSM parameter space.
A search for neutral Higgs bosons decaying to pairs of tau leptons with the ATLAS detector at the LHC is presented. The analysis is based on proton-proton collisions at a center-of-mass energy of 7 TeV, recorded in 2010 and corresponding to an integrated luminosity of 36 pb^-1. After signal selection, 276 events are observed in this data sample. The observed number of events is consistent with the total expected background of 269 +/- 36 events. Exclusion limits at the 95% confidence level are derived for the production cross section of a generic Higgs boson phi as a function of the Higgs boson…
