Precision Higgs Physics at a Future Linear Collider

Assuming that a Higgs sector is responsible for electroweak symmetry breaking, we attempt to address two important questions: How much better precision are various measurements of Higgs boson properties at a future linear collider than at the LHC? What can a future linear collider do for Higgs physics that the LHC cannot?Comment: 10 pp, 4 eps fig, econf, invited talk at RADCOR 2000 (Carmel, CA, Sept 2000), includes additional comments and citations on multiple Higgs productio

Searching for H -> gamma gamma in weak boson fusion at the LHC

Weak boson fusion is a copious source of intermediate mass Higgs bosons at the LHC, with a rate sigma*B(H -> gamma gamma) of up to 9 fb. The additional very energetic forward jets in these events provide for a unique signature. A parton level analysis of the dominant backgrounds demonstrates that this channel allows the observation of H -> gamma gamma in a low background environment, with modest luminosity.Comment: 12 pages, 4 figures, submitted to Journal of High Energy Physic

A new method for extracting the bottom quark Yukawa coupling at the CERN Large Hadron Collider

We propose a new method for measuring the H -> bb rate at the CERN LHC in a manner which would allow extraction of the b quark Yukawa coupling. Higgs boson production in purely electroweak WHjj events is calculated. The Standard Model signal rate including decays W -> l nu and H -> bb is 11 fb for M_H = 120 GeV. It is possible to suppress the principal backgrounds, Wbbjj and ttjj, to approximately the level of the signal. As the top quark Yukawa coupling does not appear in this process, it promises a reliable extraction of g_Hbb in the context of the Standard Model or some extensions, such as the MSSM.Comment: added background, updated/added references, additional comment

Observing H -> W*W* -> e mu pT(miss) in weak boson fusion with dual forward jet tagging at the LHC

Weak boson fusion promises to be a copious source of intermediate mass Standard Model Higgs bosons at the LHC. The additional very energetic forward jets in these events provide for powerful background suppression tools. We analyze the H -> W^(*)W^(*) -> e mu pTmiss decay mode for a Higgs boson mass in the 130-200 GeV range. A parton level analysis of the dominant backgrounds (production of W pairs, tt~ and Z -> tau tau in association with jets) demonstrates that this channel allows the observation of H -> W^(*)W^(*) in a virtually background-free environment, yielding a significant Higgs boson signal with an integrated luminosity of 5 fb^-1 or less. Weak boson fusion achieves a much better signal to background ratio than inclusive H -> e mu pTmiss and is therefore the most promising search channel in the 130-200 GeV mass range.Comment: 13 pages, 4 PS figs; references updated, top-quark backgrounds corrected in table

TeV resonances in top physics at the LHC

We consider the possibility of studying novel particles at the TeV scale with enhanced couplings to the top quark via top quark pair production at the LHC and VLHC. In particular we discuss the case of neutral scalar and vector resonances associated with a strongly interacting electroweak symmetry breaking sector. We constrain the couplings of these resonances by imposing appropriate partial wave unitarity conditions and known low energy constraints. We evaluate the new physics signals via WW -> tt~ for various models without making approximation for the initial state W bosons, and optimize the acceptance cuts for the signal observation. We conclude that QCD backgrounds overwhelm the signals in both the LHC and a 200 TeV VLHC, making it impossible to study this type of physics in the tt~ channel at those machines.Comment: 15p, add. comments to clarify model, +2 ref., version to appear PR

Probing Neutral Gauge Boson Self-interactions in ZZ Production at Hadron Colliders

A detailed analysis of ZZ production at the upgraded Fermilab Tevatron and the CERN Large Hadron Collider is presented for general ZZZ and ZZ\gamma couplings. Deviations from the Standard Model gauge theory structure for each of these can be parameterized in terms of two form factors which are severely restricted by unitarity at high energy. Achievable limits on these couplings are shown to be a dramatic improvement over the limits currently obtained by e^+e^- experiments.Comment: 36 pages, 15 figures, revte

Breakdown of the Narrow Width Approximation for New Physics

The narrow width approximation is used in high energy physics to reduce the complexity of scattering calculations. It is a fortunate accident that it works so well for the Standard Model, but in general it will fail in the context of new physics. We find numerous examples of significant corrections when the calculation is performed fully off-shell including a finite width, notably from effects from the decay matrix elements. If not taken into account, attempts to reconstruct the Lagrangian of a new physics discovery from data would result in considerable inaccuracies and likely inconsistencies.Comment: 4 p., 3 figs, comments clarified, version to appear in PR

Measurement of electron scattering in aluminum at 1.0 MeV for non-normal incidence, part 1

Electron scattering in aluminum and gold targets at 1.0 MeV for non-normal incidenc

Mixed top-bottom squark production at the LHC

We calculate cross sections for mixed stop-sbottom pair production at the LHC, analogous to single-top production, a weak process involving the W-t(i)-b(j) vertex. While coupling-suppressed relative to QCD same-flavor squark pair production, the signal is distinctive due to heavy-flavor tagging along with a possible same-sign lepton pair in the final state. SUSY backgrounds can often be suppressed many orders of magnitude by taking advantage of distinct kinematic differences from the signal. Measuring the rate of this process would add significant additional information to that gathered from other SUSY processes. If the stop and sbottom mixings can be determined elsewhere, stop-sbottom production would provide for a measurement of the weak squark gauge coupling and super-CKM vertex factor.Comment: typo corrected, comment on W-associated channel added, version to appear in PR