Session G12: Higgs II

Search for a Higgs Boson in Decays to $WW^{*}$ at CDF

We present a search for Standard Model Higgs production in $p\overline{p}$ collisions at $\sqrt{s} =$~1.96~TeV using approximately 4~fb$^{-1}$ of data collected with the CDF~II detector. We consider the diboson decay channel, $H \rightarrow W W^{\*}$, which is the dominant decay mode for Higgs boson masses above 140~GeV/$c^{2}$. We further require both $W$ bosons to decay leptonically. Both single and associated Higgs production modes are considered. In order to maximize sensitivity, a combined Matrix Element method and Neural Network approach is utilized to distinguish signal from background processes. Cross-section limits are presented for Higgs mass hypothesis between 110~GeV/$c^{2}$ and 200~GeV/$c^{2}$.   

Search for the Higgs Boson in $WW$ Decays Involving Taus in $p\bar{p}$ Collisions at $\sqrt{s}$=1.96 TeV

We present a search for the standard model Higgs boson produced via the $H\to WW^{(*)}$ process in which one of the W's decays to a hadronic tau and the other to a muon at a center-of-mass energy of $\sqrt{s}=$1.96~TeV with the D0 detector at the Fermilab Tevatron collider. A Higgs particle with a mass greater than 140 GeV primarily decays into a pair of W-bosons and the leptonic decay channels of the W provide a clear signature. Additional sensitivity beyond that achieved with electron and muon decays can be achieved by considering tau decays. As well as the inclusion of the full data set, up to 4~fb$^{-1}$, improvements to the sensitivity will be discussed.   

Search for Associated Production of a $W$ and Higgs Boson in the $\tau\nu b\overline{b}$ Final State at CDF

We present results of a search for associated production of $W$ and Higgs bosons based on 2~fb$^{-1}$ of data collected with the CDF~II detector from $p\bar{p}$ collisions at $\sqrt{s}$=1.96~TeV. The search is performed using events with two jets, a hadronically decaying $\tau$ lepton, and missing transverse energy originating from the $H\rightarrow b\bar{b}$ and $W\rightarrow \tau\nu$ decay modes. We present the status of the search focusing on techniques for triggering on and identifying hadronic tau decays.   

Higgs/$ZZ$ searches in the 3 leptons + X channels

The mechanism of spontaneously broken symmetries is one of the key problems in particles physics. Hence understanding the Higgs mechanism, by which the fundamental particles gain mass, is one of the primary goals of the LHC. Another area of great interest is $ZZ$ diboson production. In the Standard Model(SM), the triple neutral gauge couplings ($ZZZ$ and $ZZ\gamma$) are absent and $ZZ$ searches provide a test for any gauge-coupling anomalies and hence possible new physics beyond the SM. Production of $ZZ$ dibosons is an irreducible background for the Higgs production with a 4 lepton decay mode (particularly at high mass). To maximize the sensitivity of Higgs searches, the $3\ell + X$ channels were considered as they have higher a acceptance than the $4\ell$ channel due to inefficiencies in lepton reconstruction. I pursued an exclusive search for the Higgs/$ZZ$ signal in the $3\ell +X$ channel using clustering algorithms for finding unidentified electrons. The motivations for a cluster based algorithm are: 1) no assumption of a cluster width is required 2) the cluster centric based algorithm has greater $\eta$ coverage than the standard electron identification methods and 3) the cluster based algorithm does not split the cluster in the crack regions. The background in the $3\ell+X$ channel is very challenging. In this work, I present a set of selection criteria along with a likelihood method for particle identification to achieve an acceptable signal-over-background.   

Search for Standard Model $H \rightarrow \tau \tau$ Decays using a new $\tau$ identification algorithm

Clean and efficient identification of $\tau$ leptons is required for a number CDF Run~II analyses such as $W \rightarrow \tau \nu$ and $Z \rightarrow \tau \tau$ production cross section measurements, top quark dilepton studies, and searches for both SUSY particles and MSSM Higgs bosons. Improved $\tau$ lepton identificantion can also be used to help improve the sensitivity of standard model Higgs boson searches by increasing the number of final states available to the analyses. We present a new $\tau$ lepton identification method based on a Boosted Decision Tree (BDT) approach, which like other multivariate methods can provide higher selection efficiency as a function of the associated fake rate with respect to what one obtains using a rectangular set of selection criteria. The performance of the new algorithm, which gives an improvement on order of 15\% over the current CDF $\tau$ identification algorithm, will be shown.   

Multivariate techniques for $VH \rightarrow$ MET + $b\overline{b}$ Searches at CDF

We present improved techniques applicable to searches for a Higgs boson in events with missing transverse energy and two b-quark jets at CDF. This sample includes substantial contributions from both $ZH$ and $WH$ final states, as well as substantial backgrounds originating from QCD multi-jets, $t\overline{t}$ production, heavy diboson production, and instrumental backgrounds. Multivariate techniques have been shown to be extremely important in increasing the experimental sensitivity in this channel. We investigate the use of multivariate methods targeted toward rejection of specific backgrounds and how to combine these methods to form a single overall discriminant. We present expected improvements in Higgs search sensitivity using these new techniques.   

Search for a Standard Model Higgs Boson in Events with Missing Transverse Energy and Jets at CDF

We present a search for a standard model Higgs boson produced in association with a $W$ or $Z$ boson in $p\overline{p}$ collisions at 1.96~TeV center of mass energy. The data collected with the CDF~II detector at the Tevatron collider at Fermilab correspond to an integrated luminosity of 2.1 fb$^{-1}$. We invesitgate the scenario where the Higgs boson decays into a $b\overline{b}$ pair and where either the $Z$ decays into neutrinos or the lepton from the $W$-decay escapes detection giving an expected event signature of two b-quark jets, no leptons, and missing transverse energy. We present preliminary results from this search and discuss potential future improvements. A data-driven model of the QCD multi-jet background and advanced analysis techniques used in increasing sensitivity of the search are also discussed.   

CMS Discovery Potential of Standard Model Higgs Boson in the Vector Boson Fusion Process

The discovery potential of standard model Higgs boson in the vector boson fusion process with CMS detector is presented. We use cut-based strategy to establish the baseline reconstruction and the analysis scenario. The neural netwrok technique is used to further increase the discovery potential by studying the complicated correlation among various observables. Dedicated techniques of jet energy correction, missing Et correction, hadronic W and Z reconstruction, and lepton isolation are studied and tuned to maximize S/B in the lepton+MET+multi-jet final states. Data driven strategy is used to control the systematic uncertainty from the measurement of background cross section, various detector level and instrumental effects. The Monte Carlo study shows the 5-sigma discovery for the wide mass range of SM Higgs Boson will be achieved with 1-5 fb-1 of LHC data in the vector boson fusion process.   

Search for Associated Production of $Z$ and Higgs Bosons in the $\mu \mu bb$ Final State in $p\bar{p}$ Collisions at $\sqrt{s}$=1.96 TeV.

We present a search for a low mass standard model Higgs boson produced in association with a $Z$ boson decaying to two muons at a center-of-mass energy of $\sqrt{s}=$1.96~TeV with the D0 detector at the Fermilab Tevatron collider. The search is performed in events containing one or two b-tagged jets with of order 4~fb$^{-1}$ of data. As well as the inclusion of the full data set, recent improvements to the sensitivity will be discussed.