A double parton scattering background to Higgs boson production at the LHC

The experimental capability of recognizing the presence of b quarks in complex hadronic final states has addressed the attention towards final states with b\bar{b} pairs for observing the production of the Higgs boson at the LHC, in the intermediate Higgs mass range.We point out that double parton scattering processes are going to represent a sizeable background to the process.Comment: 9 pages, 2 figure

Standard Model Higgs Physics at a 4 TeV Upgraded Tevatron

We compute an array of Standard Model Higgs boson (\hsm) signals and backgrounds for a possible upgrade of the Tevatron to E_{\rm cm}=4\tev. Taking \mt\geq 140\gev, and assuming a total accumulated luminosity of L=30\fbi, we find that a Standard Model Higgs boson with \mhsm\lsim 110\gev could almost certainly be detected using the \wpm\hsm\rta l\nu b\anti b mode. A Higgs boson with mass between \sim 120\gev and \sim 140\gev or above \sim 230-250\gev almost certainly would not be seen. A Higgs boson with \mhsm\sim 150\gev or 200\lsim\mhsm\lsim 230-250\gev has a decent chance of being detected in the ZZ\rta 4l mode. There would also be some possibility of discovering the \hsm in the WW\rta l\nu jj mode for 150\lsim\mhsm\lsim 200\gev. Finally, hints of an event excess in the WW\rta ll \nu\nu mode due to the \hsm might emerge for 140\lsim\mhsm\lsim 180\gev. Given the difficult nature of the Higgs boson signals for \mhsm values beyond the reach of LEP-200, and the discontinuous \mhsm range that could potentially be probed, justification of an upgrade of the Tevatron to 4\tev on the basis of its potential for Standard Model Higgs boson discovery would seem inappropriate.Comment: 21 pages; requires phyzzx.tex and tables.tex; full postscript file including embedded figures available via anonymous ftp at ucdhep.ucdavis.edu as [anonymous.gunion]4tev.ps, preprint UCD-94-1

Anomalous Higgs Couplings

We review the effects of new effective interactions on the Higgs boson phenomenology. New physics in the electroweak bosonic sector is expected to induce additional interactions between the Higgs doublet field and the electroweak gauge bosons leading to anomalous Higgs couplings as well as to anomalous gauge-boson self-interactions. Using a linearly realized $SU(2)_L \times U(1)_Y$ invariant effective Lagrangian to describe the bosonic sector of the Standard Model, we review the effects of the new effective interactions on the Higgs boson production rates and decay modes. We summarize the results from searches for the new Higgs signatures induced by the anomalous interactions in order to constrain the scale of new physics in particular at CERN LEP and Fermilab Te vatron colliders.Comment: 35 pages, latex using epsfig.sty psfig.sty and axodraw.sty, 16 postscript figure

QCD and Yukawa corrections to single-top-quark production via q qbar -> t bbar

We calculate the O(alpha_s) and O(alpha_W m_t^2/M_W^2) corrections to the production of a single top quark via the weak process q qbar -> t bbar at the Fermilab Tevatron and the CERN Large Hadron Collider. An accurate calculation of the cross section is necessary in order to extract |V_tb| from experiment.Comment: LaTeX, 13 pages, replaced with version to appear in Phys. Rev.

Ultrafast modulation of the chemical potential in BaFe2As2 by coherent phonons

Time- and angle-resolved extreme ultraviolet photoemission spectroscopy is used to study the electronic structure dynamics in BaFe2As2 around the high-symmetry points Γ and M. A global oscillation of the Fermi level at the frequency of the A1g(As) phonon mode is observed. It is argued that this behavior reflects a modulation of the effective chemical potential in the photoexcited surface region that arises from the high sensitivity of the band structure near the Fermi level to the A1g(As) phonon mode combined with a low electron diffusivity perpendicular to the layers. The results establish a novel way to tune the electronic properties of iron pnictides: coherent control of the effective chemical potential. The results further suggest that the equilibration time for the effective chemical potential needs to be considered in the ultrafast electronic structure dynamics of materials with weak interlayer coupling. © 2014 American Physical Society

Window on Higgs Boson: Fourth Generation b′b^\prime Decays Revisited

Direct and indirect searches of the Higgs boson suggest that 113 GeV $\lesssim m_H \lesssim$ 170 GeV is likely. With the LEP era over and the Tevatron Run II search via $p\bar p \to WH+X$ arduous, we revisit a case where $WH$ or $ZH +$ jets could arise via strong $b^\prime\bar b^\prime$ pair production. In contrast to 10 years ago, the tight electroweak constraint on $t^\prime$--$b^\prime$ (hence $t^\prime$--$t$) splitting reduces FCNC $b^\prime\to bZ$, $bH$ rates, making $b^\prime\to cW$ naturally competitive. Such a "cocktail solution" is precisely the mix that could evade the CDF search for $b^\prime\to bZ$, and the $b^\prime$ may well be lurking below the top. In light of the Higgs program, this two-in-one strategy should be pursued.Comment: 4 pages, RevTex, 4 eps figures, One more figure, version to be published in Phys. Rev.

P Pbar to T Tbar H: A Discovery mode for the Higgs boson at the Tevatron

The production of a Standard Model Higgs boson in association with a top quark pair at the upcoming high luminosity run (15 inverse fb integrated luminosity) of the Fermilab Tevatron (root s = 2.0 TeV) is revisited. For Higgs masses below 140 GeV we demonstrate that the production cross section times branching ratio for H->B Bbar decays yields a significant number of events and that this mode is competitive with and complementary to the searches using P Pbar -> WH, ZH associated production. For higher mass Higgs bosons the H -> W+ W- decays are more difficult but have the potential to provide a few spectacular events.Comment: 10 pages, Latex, RevTex, 3 ps figures: Updated reconstruction efficiency and figure

A Higgs or Not a Higgs? What to Do if You Discover a New Scalar Particle

We show how to systematically analyze what may be inferred should a new scalar particle be discovered in collider experiments. Our approach is systematic in the sense that we perform the analysis in a manner which minimizes apriori theoretical assumptions as to the nature of the scalar particle. For instance, we do not immediately make the common assumption that a new scalar particle is a Higgs boson, and so must interact with a strength proportional to the mass of the particles with which it couples. We show how to compare different observables, and so to develop a decision tree from which the nature of the new particle may be discerned. We define several categories of models, which summarize the kinds of distinctions which the first experiments can make.Comment: 66 pages, 14 figures, version to appear in International Journal of Mod. Phys.