549 research outputs found
The Search for Higgs particles at high-energy colliders: Past, Present and Future
I briefly review the Higgs sector in the Standard Model and its minimal
Supersymmetric extension, the MSSM. After summarizing the properties of the
Higgs bosons and the present experimental constraints, I will discuss the
prospects for discovering these particle at the upgraded Tevatron, the LHC and
a high-energy linear collider. The possibility of studying the
properties of the Higgs particles will be then summarized.Comment: 28 pages, latex, 15 figures, talk at WHEPP VII, Allahabad, Indi
Higgs Physics at Future Colliders: recent theoretical developments
I review the physics of the Higgs sector in the Standard Model and its
minimal supersymmetric extension, the MSSM. I will discuss the prospects for
discovering the Higgs particles at the upgraded Tevatron, at the Large Hadron
Collider, and at a future high--energy linear collider with
centre--of--mass energy in the 350--800 GeV range, as well as the possibilities
for studying their fundamental properties. Some emphasis will be put on the
theoretical developments which occurred in the last two years.Comment: 20 pages, latex, 12 figures. Talk given at PASCOS 2003 (Bombay,
India
Three-body decays of sleptons in models with non-universal Higgs masses
We compute the three-body decays of charged sleptons and sneutrinos into
other sleptons. These decays are of particular interest in SUSY-breaking models
with non-universal Higgs mass parameters, where the left-chiral sleptons can be
lighter than the right-chiral ones, and lighter than the lightest neutralino.
We present the formulas for the three-body decay widths together with a
numerical analysis in the context of gaugino-mediated SUSY breaking with a
gravitino LSP.Comment: Version published in JHEP. See http://cern.ch/kraml/papers/ for
high-res figure
Constraining General Two Higgs Doublet Models by the Evolution of Yukawa Couplings
We study how general two Higgs doublet models can be constrained by
considering their properties under renormalization group evolution of the
Yukawa couplings. We take into account both the appearance of a Landau pole as
well as off-diagonal Yukawa couplings leading to flavour changing neutral
currents in violation with experimental constraints at the electroweak scale.
We find that the latter condition can be used to limit the amount of Z2
symmetry breaking allowed in a given model.Comment: 28 pages, 10 figures, added discussion of evolution from high to low
scales, to be published in JHE
Higgs production with large transverse momentum in hadronic collisions at next-to-leading order
Inclusive associated production of a light Higgs boson (m_H < m_t) with one
jet in pp collisions is studied in next-to-leading order QCD. Transverse
momentum (p_T < 30 GeV) and rapidity distributions of the Higgs boson are
calculated for the LHC in the large top-quark mass limit. It is pointed out
that, as much as in the case of inclusive Higgs production, the K-factor of
this process is large (~1.6) and depends weakly on the kinematics in a wide
range of transverse momentum and rapidity intervals. Our result confirms
previous suggestions that the production channel p+p -> H+jet ->
gamma+gamma+jet gives a measurable signal for Higgs production at the LHC in
the mass range 100-140 GeV, crucial also for the ultimate test of the Minimal
Supersymmetric Standard Model.Comment: 7 pages, 3 eps figures include
Natural Little Hierarchy from a Partially Goldstone Twin Higgs
We construct a simple theory in which the fine-tuning of the standard model
is significantly reduced. Radiative corrections to the quadratic part of the
scalar potential are constrained to be symmetric under a global U(4) x U(4)'
symmetry due to a discrete Z_2 "twin" parity, while the quartic part does not
possess this symmetry. As a consequence, when the global symmetry is broken the
Higgs fields emerge as light pseudo-Goldstone bosons, but with sizable quartic
self-interactions. This structure allows the cutoff scale, \Lambda, to be
raised to the multi-TeV region without significant fine-tuning. In the minimal
version of the theory, the amount of fine-tuning is about 15% for \Lambda = 5
TeV, while it is about 30% in an extended model. This provides a solution to
the little hierarchy problem. In the minimal model, the "visible" particle
content is exactly that of the two Higgs doublet standard model, while the
extended model also contains extra vector-like fermions with masses ~(1-2)TeV.
At the LHC, our minimal model may appear exactly as the two Higgs doublet
standard model, and new physics responsible for cutting off the divergences of
the Higgs mass-squared parameter may not be discovered. Several possible
processes that may be used to discriminate our model from the simple two Higgs
doublet model are discussed for the LHC and for a linear collider.Comment: 22 page
Constraints on the MSSM from the Higgs Sector - A pMSSM Study of Higgs Searches, Bs -> mu+ mu- and Dark Matter Direct Detection
We discuss the constraints on Supersymmetry in the Higgs sector arising from
LHC searches, rare B decays and dark matter direct detection experiments. We
show that constraints derived on the mass of the lightest h0 and the CP-odd A0
bosons from these searches are covering a broader fraction of the SUSY
parameter space compared to searches for strongly interacting supersymmetric
particle partners. We discuss the implications of a mass determination in the
range 123 < Mh < 127 GeV, inspired by the intriguing hints reported by the
ATLAS and CMS collaborations, as well as those of a non-observation of the
lightest Higgs boson on MSSM scenarios not excluded at the end of 2012 by LHC
and direct dark matter searches and their implications on LHC SUSY searches.Comment: 11 pages, 12 figures. v3 increased scan statistics and parameter
range, added Higgs rate constraints, text and references reviewed, to appear
on Eur. Phys. J.
One-Loop QCD Mass Effects in the Production of Polarized Bottom and Top Quarks
The analytic expressions for the production cross sections of polarized
bottom and top quarks in annihilation are explicitly derived at the
one-loop order of strong interactions. Chirality-violating mass effects will
reduce the longitudinal spin polarization for the light quark pairs by an
amount of , when one properly considers the massless limit for the final
quarks. Numerical estimates of longitudinal spin polarization effects in the
processes and are presented.Comment: 17 p. (5 figs available upon request), LaTeX, MZ-TH/93-30, RAL/93-81,
FTUV/93-4
Higgs and Z boson decays into light gluinos
We calculate the decay rate of scalar and pseudoscalar Higgs bosons into a
pair of gluinos, within the Minimal Supersymmetric Standard Model. In the
theoretically and experimentally allowed light gluino window, \mg \sim 3--5
GeV, gluino pairs can completely dominate the decays of the light scalar Higgs
boson and play a prominent role in the decay of the pseudoscalar Higgs boson.
This would alter the limits obtained from decays on the lightest CP--even
and CP--odd Higgs bosons, and could jeopardize the search for these Higgs
particles at future hadron colliders. In contrast, the branching ratio for the
two--body decay of bosons into pairs of light gluinos is less than 0.1\%.Comment: Latex file, 16 pages of text. 8 uufiled postscript figures included.
Compressed postscript version with figures available by anonymous ftp at
ftp://phenom.physics.wisc.edu/pub/preprints/current/madph-94-853.ps.
Next-to-next-to-leading logarithmic corrections at small transverse momentum in hadronic collisions
We study the region of small transverse momenta in qqbar- and gg-initiated
processes with no colored particle detected in the final state. We present the
universal expression of the O(alpha_s^2) logarithmically enhanced contributions
up to next-to-next-to-leading logarithmic accuracy. From there we extract the
coefficients that allow the resummation of the large logarithmic contributions.
We find that the coefficient known in the literature as B^{(2)} is process
dependent, since it receives a hard contamination from the one loop correction
to the leading order subprocess. We present the general result of B^{(2)} for
both quark and gluon channels. In particular, in the case of Higgs production,
this result will be relevant to improve the matching between resummed
predictions and fixed order calculations.Comment: LaTeX, 8 pages. Few typos corrected, particularly Eq.(25). Two
references added, to be published in PR
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