9 research outputs found
QCD corrections to electroweak l nu_l jj and l^+ l^- jj production
The production of W or Z bosons in association with two jets is an important
background to the Higgs boson search in vector-boson fusion at the LHC. The
purely electroweak component of this background is dominated by vector-boson
fusion, which exhibits kinematic distributions very similar to the Higgs boson
signal. We consider the next-to-leading order QCD corrections to the
electroweak production of l nu_l jj and l^+ l^- jj events at the LHC, within
typical vector-boson fusion cuts. We show that the QCD corrections are modest,
increasing the total cross sections by about 10%. Remaining scale uncertainties
are below 2%. A fully-flexible next-to-leading order partonic Monte Carlo
program allows to demonstrate these features for cross sections within typical
vector-boson-fusion acceptance cuts. Modest corrections are also found for
distributions.Comment: 26 pages, 10 figures. PRD final version. One reference corrected,
introduction expande
Jet Production via Strongly-Interacting Color-Singlet Exchange in Collisions
A study of the particle multiplicity between jets with large rapidity
separation has been performed using the D{\O}detector at the Fermilab Tevatron
Collider operating at TeV. A significant excess of
low-multiplicity events is observed above the expectation for color-exchange
processes. The measured fractional excess is , which is consistent with a strongly-interacting
color-singlet (colorless) exchange process and cannot be explained by
electroweak exchange alone. A lower limit of 0.80% (95% C.L.) is obtained on
the fraction of dijet events with color-singlet exchange, independent of the
rapidity gap survival probability.Comment: 15 pages (REVTeX), 3 PS figs (uuencoded/tar compressed, epsf.sty)
Complete postscript available at http://d0sgi0.fnal.gov/d0pubs/journals.html
Submitted to Physical Review Letter
Probing color-singlet exchange in -jet events at the LHC
The purely electroweak process (via -channel or
exchange) provides a copious and fairly clean source of color-singlet exchange
events in collisions at the LHC. A judicious choice of phase-space region
allows the suppression of QCD backgrounds to the level of the signal. The
color-singlet-exchange signal can be distinguished from QCD backgrounds by the
radiation patterns of additional minijets in individual events. A rapidity-gap
trigger at the minijet level substantially enhances the signal versus the
background. Analogous features of weak boson scattering events make -jet
events at the LHC an ideal laboratory for investigation of the soft-jet
activity expected in weak-boson scattering events.Comment: 24 pages (with 7 embedded figures), Revtex, uses epsf.sty.
Z-compressed postscript version also available at
http://phenom.physics.wisc.edu/pub/preprints/1996/madph-96-943.ps.Z or at
ftp://phenom.physics.wisc.edu/pub/preprints/1996/madph-96-943.ps.
A method for identifying H -> tau tau -> e mu pTmiss at the CERN LHC
Weak boson fusion promises to be a copious source of intermediate mass Higgs
bosons at the LHC. The additional very energetic forward jets in these events
provide for powerful background suppression tools. We analyze the subsequent H
-> tau tau -> e mu pTmiss decay for Higgs boson masses in the 100-150 GeV
range. A parton level analysis of the dominant backgrounds demonstrates that
this channel allows the observation of H -> tau tau in a low-background
environment, yielding a significant Higgs boson signal with an integrated
luminosity of order 60 fb^-1 or less, over most of the mass range. We also
restate a No-Lose Theorem for observation of at least one of the CP-even
neutral Higgs bosons in the MSSM, which requires an integrated luminosity of
only 40 fb^-1.Comment: 21 pages, 10 embedded PS figs; additional comments on b-jet veto in
tt~ backgrounds; to be published in Phys Rev
Searching for H --> tau tau in weak boson fusion at the LHC
Weak boson fusion is a copious source of intermediate mass Higgs bosons at
the LHC. The additional very energetic forward jets in these events provide for
powerful background suppression tools. We analyze the decay
mode for the Standard Model Higgs boson. A parton level analysis of the
dominant physics backgrounds (mainly and Drell-Yan production
of 's) and of reducible backgrounds (from jet and
production in association with two jets and subsequent leptonic decays)
demonstrates that this channel allows the observation of in a
low background environment, yielding a significant Higgs signal with an
integrated luminosity of about 30 fb. The weak boson fusion process thus
allows direct measurement of the coupling.Comment: 32 pages, Revtex, uses epsf.sty, 6 postscript figures. Opposite sign
charge requirement for tau candidates added for reducible backgrounds; cuts
for two figures explained more clearly in text; typos correcte
HERA Collider Physics
HERA, the first electron-proton collider, has been delivering luminosity
since 1992. It is the natural extension of an impressive series of fixed-target
lepton-nucleon scattering experiments. The increase of a factor ten in
center-of-mass energy over that available for fixed-target experiments has
allowed the discovery of several important results, such as the large number of
slow partons in the proton, and the sizeable diffractive cross section at large
. Recent data point to a possible deviation from Standard Model
expectations at very high , highlighting the physics potential of HERA for
new effects. The HERA program is currently in a transition period. The first
six years of data taking have primarily elucidated the structure of the proton,
allowed detailed QCD studies and had a strong impact on the understanding of
QCD dynamics. The coming years will bring the era of electroweak studies and
high measurements. This is therefore an appropriate juncture at which to
review HERA results.Comment: 351 pages, 154 figures, submitted to Reviews of Modern Physic
Rapidity gap signals in Higgs production at the SSC
We examine the structure of the underlying event in neutral Higgs production
at the Superconducting-Supercollider (SSC). Gaps, regions of rapidity
containing no soft particle production, can provide a clean signature for
boson fusion to the heavy Higgs. We first examine the physical basis of gap
production and estimate the survival probability of gaps in the minijet model.
Then, using PYTHIA, and HERWIG we compare gap events to pair production
from top decay and fusion. We find that, if experimental problems
can be overcome, gaps should provide a small, but clean, signal for heavy Higgs
production at the SSC.Comment: 24 Latex pages 5 postscript figures available upon request MAD/PH/76
BA-93-3