Session B8: Higgs Detection I

Search for Higgs Bosons decaying to diphoton final states at D0

We present a search for a new particle decaying to two photons, such as the Standard Model Higgs boson, using 7.5~fb$^{-1}$ of integrated luminosity collected by the D0 detector at the Tevatron from July 2002 to July 2010. No evidence is observed and so limits on the production cross section times the branching ratio as a function of hypothetical particle mass are set at 95\% confidence level.   

A novel technique for Higgs mass estimation in leptonic $H\rightarrow WW$ decays

One of the most important Higgs search channels at the Tevatron and LHC is the $H\rightarrow WW\rightarrow\ell\nu \ell\nu$ final state. Due to the un-reconstructed neutrinos in this decay, the Higgs mass cannot be directly reconstructed. This presentation will outline a novel technique to estimate the Higgs mass in $H\rightarrow WW\rightarrow\ell\nu \ell\nu$ decays, which is applicable in Higgs searches at both the Tevatron and LHC.   

Search for a standard model Higgs boson in the $H$ $\rightarrow$ $WW$ $\rightarrow$ $l$$\nu$$jj$ final state at CDF

We present a search for standard model Higgs boson production in $p \bar{p}$ collisions at a center-of-mass energy of $\sqrt{s} = 1.96$~TeV. For this analysis, we use data collected with the CDF~II detector. We consider $H$ decay into two $W$ bosons where one $W$ decays into a lepton plus a neutrino and the other decays into two quark jets. This is the dominant decay mode for a Higgs with mass larger than 135~GeV/$c^{2}$. This decay mode has an important kinematic feature in that the $W$ bosons have a spin correlation originating from the spin of Higgs which is zero. We employ a likelihood method with variables such as the angle between the lepton and an up-type jet to separate signals from backgrounds.   

Search for a Low-mass Higgs boson in the radiative decay $\Upsilon(1S)\to\gamma A^0$, $A^0\to \tau^+ \tau^-$ at {\sc BaBar}

The Higgs boson is a scalar elementary particle predicted by the Higgs mechanism, which explains the origin of mass of fundamental particles. The discovery of the Higgs boson would would be key to unlocking the mystery of mass. The Next-to-Minimal Supersymmetric Standard Model (NMSSM) predicts the existence of a light scalar CP-odd Higgs boson in the mass range of 0-10 GeV. The primary objective of the present analysis is to search for a light Higgs boson $A^0$ produced via $b\bar b$ annihilation in the decay of $\Upsilon(1S)$. We search for the decay $\Upsilon(2S)\to\pi^+\pi^-\Upsilon(1S),\Upsilon(1S)\to\gamma A^0,\ A^0\to\tau^+\tau^-$ in the {\sc BaBar} dataset by combining variables that describe the decays of interest into two multi-variate discriminants, which help separate signal events from unwanted backgrounds.   

Searches for $ZZ$ and Higgs to $ZZ$ production at CDF

We present measurements of the $ZZ$ diboson cross section using data collected by the CDF II experiment in both the four lepton and two lepton plus two neutrino final states. In addition, the same datasets are used to search for standard model Higgs boson production for the case where the Higgs decays to a pair of $Z$ bosons. The Higgs search in these decay channels can be combined with the current Higgs searches and improve existing limits from the high mass region down to about 140 GeV/c$^2$.   

Search for Higgs Bosons decaying to dilepton plus dijet final states via $H\rightarrow ZZ\rightarrow\ell\ell jj$ at D0

A search for the standard model Higgs boson was performed where the Higgs decays via H$\rightarrow ZZ \rightarrow \ell\ell jj$ with the D0 detector at the Fermilab Tevatron collider with 4.2~fb$^{-1}$ of data. Events are selected with at least two reconstructed jets and a Z candidate reconstructed from the two leptons. A boosted decision tree was trained to distinguish between signal and background events. This channel becomes significantly important for a Higgs with a mass higher than 180~GeV.   

Application of expert discriminants to searches for a standard model Higgs boson in the missing transverse energy plus two $b$-quark final state at CDF

We present a search for the associated production of a $W$ or $Z$ boson and a standard model Higgs boson, where the final state consists of a large amount of missing transverse energy and two jets consistent with the decay of the Higgs boson ($H \rightarrow bb$). This channel is among the most sensitive for Higgs masses below 135 GeV/c$^2$. In the context of this search, we explore the use of expert discriminants, multivariate discriminants trained to distinguish the signal processes from individual backgrounds, and various methods for combining them into a final discriminant to improve the overall search sensitivity.   

Search for the standard model Higgs boson produced in association with top quarks at CDF

We present a preliminary search for the standard model Higgs boson produced in association with a top quark pair using the CDF II detector at the Fermilab Tevatron in 5.1 fb$^{-1}$ of data. We consider events which have only one identified charged lepton, an imbalance in transverse momentum, and at least five jets, where at least two of these jets are consistent with originating from the decay of a $B$ hadron. Using a neural network technique, we place preliminary 95\% confidence level upper limits on the $ttH$ production cross section for a range of Higgs boson masses. Further efforts to improve the sensitivity of our search through increased signal acceptance and additional background discrimination are also described.   

Search for associated production of a standard model Higgs boson and a $t\bar{t}$ pair in the missing transverse energy plus jets final state at CDF

We present a search for a standard model Higgs boson produced in association with a top and anti-top quark pair using 5.7 fb$^{-1}$ of 1.96 TeV $p\bar{p}$ collisions from the Fermilab Tevatron collected with the CDF II detector. We select events that have large missing transverse energy and at least five jets, two or more of which are tagged as originating from $b$-quarks. We exclude events containing any high energy leptons to avoid events used in other Higgs searches at CDF. Although the cross section of the final state is much smaller than that of Higgs production in the dominant search channels, the event topology is distinct, making it an interesting channel to study. This measurement complements other searches for the Higgs boson and it can easily be combined with these other search results to improve overall Tevatron sensitivity to a standard model Higgs boson.