Sally Dawson - BNL

Sally Dawson
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Sally Dawson
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BNL
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High Energy Physics - Phenomenology (20)
 
High Energy Physics - Experiment (2)

Publications Authored By Sally Dawson

Higgs production from gluon fusion is sensitive to the properties of heavy colored fermions and to the Yukawa couplings, (Y_F M_F)/v, of these particles to the Higgs boson. We compute the two--loop, ${\cal O}((Y_F M_F)^3/v^3)$ contributions of new high mass fermions to Higgs production. In the Standard Model, these contributions are part of the well-known electroweak corrections and are negligible. Read More

The ATLAS and CMS collaborations have recently published new limits on CP conserving anomalous couplings from the $W\gamma$ and $Z\gamma$ production processes. We study the corresponding limits that can be placed on the CP violating anomalous couplings $\kappa_tilde_\gamma$ and $h^1_{\gamma, Z}$ at the LHC. We find that the process $pp --> W\gamma$ at 14 TeV can place the 95% CL limit $|\kappa_tilde_\gamma| <~ 0. Read More

In many new physics scenarios, the particle content of the Standard Model is extended and the Higgs couplings are modified, sometimes without affecting single Higgs production. We analyse two models with additional quarks. In these models, we compute double Higgs production from gluon fusion exactly at leading-order, and present analytical results in the heavy-quark mass ap- proximation. Read More

We consider models with multiple Higgs scalar gauge singlets and the resulting restrictions on the parameters from precision electroweak measurements. In these models, the scalar singlets mix with the SU(2) Higgs doublet, potentially leading to reduced couplings of the scalars to fermions and gauge bosons relative to the Standard Model Higgs boson couplings. Such models can make the Higgs sector difficult to explore at the LHC. Read More

We compute the leading chiral-logarithmic corrections to the S parameter in the four-site Higgsless model. In addition to the usual electroweak gauge bosons of the Standard Model, this model contains two sets of heavy charged and neutral gauge bosons. In the continuum limit, the latter gauge bosons can be identified with the first excited Kaluza-Klein states of the W^\pm and Z bosons of a warped extra-dimensional model with an SU(2)_L \times SU(2)_R \times U(1)_X bulk gauge symmetry. Read More

Electroweak precision data has been extensively used to constrain models containing physics beyond that of the Standard Model. When the model contains Higgs scalars in representations other than SU(2) singlets or doublets, and hence rho not equal to one at tree level, a correct renormalization scheme requires more inputs than the three needed for the Standard Model. We discuss the connection between the renormalization of models with Higgs triplets and the decoupling properties of the models as the mass scale for the scalar triplet field becomes much larger than the electroweak scale. Read More

We present a complete next-to-leading order (NLO) calculation for the total cross section for inclusive Higgs pair production via bottom-quark fusion at the CERN Large Hadron Collider (LHC) in the minimal supersymmetric standard model (MSSM) and the minimal supergravity model (mSUGRA). We emphasize the contributions of squark and gluino loops (SQCD) and the decoupling properties of our results for heavy squark and gluino masses. The enhanced couplings of the b quark to the Higgs bosons in supersymmetric models with large tanb yield large NLO SQCD corrections in some regions of parameter space. Read More

We present a complete next-to-leading order (NLO) calculation for the total cross section of inclusive Higgs pair production via bottom-quark fusion ($b\bar{b} \to hh$) at the CERN Large Hadron Collider (LHC) in the Standard Model. The NLO QCD corrections lead to less dependence on the renormalization scale ($\mu_R$) and the factorization scale ($\mu_F$) than the leading-order (LO) cross section, and they significantly increase the LO cross section. The rate for inclusive Higgs pair production is small in the Standard Model, but can be large in models with enhanced couplings of the $b$ quark to the Higgs bosons. Read More

In this letter, we present our results on a global fit to precision electroweak data in a Higgs triplet model. In models with a triplet Higgs boson, a consistent renormalization scheme differs from that of the Standard Model and the global fit shows that a light Higgs boson with mass of 100-200 GeV is preferred. Triplet Higgs bosons arise in many extensions of the Standard Model, including the left-right model and the Little Higgs models. Read More

Electroweak precision data have been extensively used to constrain models containing physics beyond that of the Standard Model. When the model contains Higgs scalars in representations other than singlets or doublets, and hence rho not equal to 1 at tree level, a correct renormalization scheme requires more inputs than the three commonly used for the Standard Model case. In such cases, the one loop electroweak results cannot be split into a Standard Model contribution plus a piece which vanishes as the scale of new physics becomes much larger than M_W. Read More

We present in this talk the one-loop electroweak precision constraints in the Littlest Higgs model, including the logarithmically enhanced contributions from both fermion and scalar loops. We find the one-loop contributions are comparable to the tree level corrections in some regions of parameter space. A low cutoff scale is allowed for a non-zero triplet VEV. Read More

We discuss the physics motivations for building a 500 - 1 TeV electron-positron linear collider. The state of the art collider technologies and the physics-driven machine parameters are discussed. A survey of some of the phenomena well suited to study at a linear collider are described, including Higgs bosons, supersymmetry, other extensions to the Standard Model, and cosmology. Read More

We perform a one-loop analysis of the rho parameter in the Littlest Higgs model, including the logarithmically enhanced contributions from both fermion and scalar loops. We find the one-loop contributions are comparable to the tree level corrections in some regions of parameter space. The fermion loop contribution dominates in the low cutoff scale f region. Read More

2002Aug
Affiliations: 1Brookhaven National Laboratory, 2University of Texas, 3University of Oklahoma

The prospects for the discovery of neutral Higgs bosons (phi^0 = H^0, h^0, A^0) produced with bottom quarks via Higgs decays into muon pairs (pp --> b b-bar phi^0 --> b b-bar mu mu-bar +X) at the CERN LHC are investigated in the minimal supersymmetric model. The complete physics background from the production of b b-bar mu mu-bar, b b-bar W^+ W^- (including t t-bar) and jj mu mu-bar, j = g, u, d, s, c in the Standard Model is calculated with realistic acceptance cuts. This discovery mode has a simple production mechanism from gg --> b b-bar phi^0 with its cross section proportional to 1/cos^2(beta) and could provide an opportunity to measure tan(beta) and the b b-bar phi^0 couplings. Read More

We discuss the relevance of the associated production of a Higgs boson with a pair of top-antitop quarks at both the LHC and a future high energy e^+e^- collider. Read More

1999Jun
Affiliations: 1Florida State University, 2Brookhaven National Laboratory, 3Florida State University

The cross section for the reaction $e^+e^- \to t\bar{t} H$ depends sensitively on the top quark Yukwawa coupling $\lambda_t$. We calculate the rate for $t\bar{t}H$ production, followed by the decay $H\to b\bar{b}$, for a Standard Model Higgs boson with 100 < m_H <130 GeV. We interface with ISAJET to generate QCD radiation, hadronization and particle decays. Read More

We compute the O(alpha_s) QCD corrections to the inclusive process e^+e^- --> t \bar t h. Although the total rate is small, it has a distinctive experimental signature and can potentially be used to measure the top quark-Higgs boson Yukawa coupling. The QCD corrections increase the rate by a factor of roughly 1. Read More

A basic introduction to the physics of the Standard Model Higgs boson is given. We discuss Higgs boson production in $e^+e^-$ and hadronic collisions and survey search techniques at future accelerators. The Higgs bosons of the minimal SUSY model are briefly considered. Read More

Errata are given for "The Higgs Hunter's Guide". These errata should be applied to the second printing of the book, dated 1991. The second printing has already corrected numerous errors and misprints contained in the originally published 1990 edition. Read More

We discuss the ${\cal O}(\alpha_s)$ QCD radiative corrections to Higgs boson production in the limit in which the top quark is much heavier than the Higgs boson. The subleading corrections, of ${\cal O} (\alpha_s M_H^2/M_{\rm top}^2)$, are presented for the decay $H\rightarrow \gamma\gamma$ and shown to be small. Read More