47 research outputs found
Constraints on the Universal Varying Yukawa Couplings: from SM-like to Fermiophobic
Varying the Standard Model (SM) fermion Yukawa couplings universally by a
generic positive scale factor (), we study the phenomenological fit to
the current available experimental results for the Higgs boson search at hadron
colliders. We point out that the Higgs production cross section and its decay
branching ratio to can be varied oppositely by to make
their product almost invariant. Thus, our scenario and the SM Higgs are
indistinguishable in the inclusive channel. The current
measurements on direct Yukawa coupling strength in the
channel are not precise enough to fix the scale factor . The most
promising is the vector-boson-fusion channel in which the CMS has already
observed possible suppression effect on the Yukawa couplings. Further more, the
global fit of the experimental data can get the optimal value by
introducing a suppression factor on the SM Yukawa couplings.Comment: 16 pages, 12 figures, 5 tables, update analysis is supplemente
Proton Decay and Cosmology Strongly Constrain the Minimal SU(5) Supergravity Model
We present the results of an extensive exploration of the five-dimensional
parameter space of the minimal supergravity model, including the
constraints of a long enough proton lifetime (\tau_p>1\times10^{32}\y) and a
small enough neutralino cosmological relic density ().
We find that the combined effect of these two constraints is quite severe,
although still leaving a small region of parameter space with m_{\tilde
g,\tilde q}<1\TeV. The allowed values of the proton lifetime extend up to
\tau_p\approx1\times10^{33}\y and should be fully explored by the
SuperKamiokande experiment. The proton lifetime cut also entails the following
mass correlations and bounds: m_h\lsim100\GeV,
m_\chi\approx{1\over2}m_{\chi^0_2}\approx0.15\gluino, , and m_\chi<85\,(115)\GeV,
m_{\chi^0_2,\chi^+_1}<165\,(225)\GeV for . Finally,
the {\it combined} proton decay and cosmology constraints predict that if
m_h\gsim75\,(80)\GeV then m_{\chi^+_1}\lsim90\,(110)\GeV for
. Thus, if this model is correct, at least one of
these particles will likely be observed at LEPII.Comment: 11 pages plus 5 figures (not included). CERN-TH.6628/92,
CTP-TAMU-61/92. A condensed version of this paper will appear in the
Proceedings of the XXVI International Conference on High Energy Physics,
Dallas--Texas, August 5--12, 199
New Constraints on Neutralino Dark Matter in the Supersymmetric Standard Model
We investigate the prospects for neutralino dark matter within the
Supersymmetric Standard Model (SSM) including the constraints from universal
soft supersymmetry breaking and radiative breaking of the electroweak symmetry.
The latter is enforced by using the one-loop Higgs effective potential which
automatically gives the one-loop corrected Higgs boson masses. We perform an
exhaustive search of the allowed five-dimensional parameter space and find that
the neutralino relic abundance depends most strongly on the
ratio . For the relic abundance is almost
always much too large, whereas for the opposite occurs. For
there are wide ranges of the remaining parameters for which
. We also determine that m_{\tilde q}\gsim250\GeV and
m_{\tilde l}\gsim100\GeV are necessary in order to possibly achieve
. These lower bounds are much weaker than the corresponding
ones derived previously when radiative breaking was {\it not} enforced.Comment: 12 pages plus 6 figures (not included), CERN-TH.6584/92,
CTP-TAMU-56/92, UAHEP921
CP--odd Correlation in the Decay of Neutral Higgs Boson into , , or
We investigate the possibility of detecting CP--odd angular correlations in
the various decay modes of the neutral Higgs boson including the modes of a
pair, a pair, or a heavy quark pair. It is a natural way to probe
the CP character of the Higgs boson once it is identified. Final state
interactions (i.e. the absorptive decay amplitude) is not required in such
correlations. As an illustrative example we take the fundamental source of the
CP nonconservation to be in the Yukawa couplings of the Higgs boson to the
heavy fermions. A similar correlation in the process is
also proposed. Our analysis of these correlations will be useful for
experiments in future colliders such as LEP II, SSC, LHC or NLC.Comment: 16 pages, plus 8 postscript graphs not posted befor
Precision Electroweak Tests of the Minimal and Flipped SU(5) Supergravity Models
We explore the one-loop electroweak radiative corrections in the minimal
and the no-scale flipped supergravity models via explicit
calculation of vacuum polarization contributions to the
parameters. Experimentally, are obtained from a global fit
to the LEP observables, and measurements. We include -dependent
effects which have been neglected in most previous ``model-independent"
analyses of this type. These effects induce a large systematic negative shift
on for light chargino masses (m_{\chi^\pm_1}\lsim70\GeV).
In agreement with previous general arguments, we find that for increasingly
large sparticle masses, the heavy sector of both models rapidly decouples, \ie,
the values for quickly asymptote to the Standard Model
values with a {\it light} Higgs (m_{H_{SM}}\sim100\GeV). Specifically, at
present the CL upper limit on the top-quark mass is m_t\lsim175\GeV in
the no-scale flipped supergravity model. These bounds can be
strengthened for increasing chargino masses in the 50-100\GeV interval. In
particular, for m_t\gsim160\GeV, the Tevatron may be able to probe through
gluino() and squark() production up to m_{\tilde g}\approx
m_{\tilde q}\approx250\GeV, exploring at least half of the parameter space in
this model.Comment: 15 pages,(6 ps figures available upon request), TeX(harvmac),
CTP-TAMU-19/93, ACT-07/9
Higgs-Boson Decay to Four Fermions Including a Single Top Quark Below Threshold
The rare decay modes Higgs four light fermions, and Higgs
single top-quark + three light fermions for , are
presented, and phenomenologically interpreted. The angular correlation between
fermion planes is presented as a test of the spin and intrinsic parity of the
Higgs particle. In Higgs decay to single top, two tree-level graphs contribute
in the standard model (SM); one couples the Higgs to , and
one to t\bar t(\sim g_{top\;yukawa}=m_t/246\GeV). The large Yukawa coupling
for m_t>100\GeV makes the second amplitude competitive or dominant for most
values. Thus the Higgs decay rate to single top directly probes the
SM universal mechanism generating both gauge boson and fermion masses, and
offers a means to infer the Higgs- Yukawa coupling when is kinematically disallowed. We find that the modes at the SSC, and at future high energy,
high luminosity colliders, may be measureable if is not too far above
. We classify non-standard Higgses as gaugeo-phobic, fermio-phobic or
fermio-philic, and discuss the Higgs single top rates for these
classes.Comment: 30 pages, 6 figures (figures available upon request); VAND-TH-93/
Searching for a light Fermiophobic Higgs Boson at the Tevatron
We propose new production mechanisms for light fermiophobic Higgs bosons
() with suppressed couplings to vector bosons () at the Fermilab
Tevatron. These mechanisms (e.g. ) are complementary to the
conventional process , which suffers from a strong suppression of
in realistic models with a . The new mechanisms extend the
coverage at the Tevatron Run II to the larger region, and offer the
possibility of observing new event topologies with up to 4 photons.Comment: 15 pages, including 5 eps-figure
Tevatron and LEP-II Probes of Minimal and String-Motivated Supergravity Models
We explore the ability of the Tevatron to probe Minimal Supersymmetry with
high energy scale boundary conditions motivated by supersymmetry breaking in
the context of supergravity/superstring theory. A number of boundary condition
possibilities are considered: dilaton-like string boundary conditions applied
at the standard GUT unification scale or alternatively at the string scale; and
extreme (``no-scale'') minimal supergravity boundary conditions imposed at the
GUT scale or string scale. For numerous specific cases within each scenario the
sparticle spectra are computed and then fed into ISAJET 7.07 so that explicit
signatures can be examined in detail. We find that, for some of the boundary
condition choices, large regions of parameter space can be explored via
same-sign dilepton and isolated trilepton signals. For other choices, the mass
reach of Tevatron collider experiments is much more limited. We also compare
mass reach of Tevatron experiments with the corresponding reach at LEP 200.Comment: 44 pages, requires phyzzx.tex, tables.tex, full postscript file
including embedded figures available via anonymous ftp at ucdhep.ucdavis.edu
as [anonymous.gunion]bgkp.ps, preprint UCD-94-1
A Minimal Four-Family Supergravity Model
We investigate the phenomenology of minimal four-family MSSM supergravity
theories containing an additional generation of heavy fermions along with their
superpartners. We demand: gauge coupling constant unification at high energy
scales; perturbative values for all Yukawa couplings for energy scales \leq
\mgut; radiative electroweak symmetry breaking via renormalization group
evolution; and a neutral LSP. The perturbative constraints imply a light
fourth-family quark and lepton spectrum, and \tanb\lsim 3. The lightest
CP-even Higgs mass is increased. Fourth-family Yukawa coupling contributions to
the evolution of scalar masses lead to unexpected mass hierarchies; \eg\ the
\staupone is generally the lightest slepton and the lightest squark is the
\wt\bpr_1. A significant lower bound is placed on the gluino mass by the
requirement that the \staupone not be the LSP. Sleptons of the first two
families are much more massive compared to the LSP and other neutralinos and
charginos than in the three-family models, and could easily lie beyond the
reach of a \sqrt s=500\gev \epem collider. Relations between slepton masses
and gaugino masses are shown to be very sensitive to the presence of a fourth
generation. The most important near-future experimental probes of the
four-family models are reviewed. A scenario with \mt\sim\mw and t\rta {\wt
t_1}\cnone is shown to be inconsistent with universal soft-SUSY-breaking
boundary conditions. Full four-family evolution of is shown to lead
to a significant enhancement in inclusive jet and di-jet spectra at Tevatron
energies when all sparticle masses are near their lower bounds.Comment: 56 pages, requires phyzzx.tex, tables.tex, figures not included, full
postscript files including figures via anonymous ftp at
ftp://ucdhep.ucdavis.edu/gunion/ , get 4gen.ps, 4gen_figs1to12.ps, and
4gen_figs13to19.p
Outcomes of elective surgery undertaken in independent sector treatment centres and NHS providers in England: audit of patient outcomes in surgery.
OBJECTIVE: To compare characteristics of patients and outcomes after elective surgery in independent sector treatment centres (ISTCs) and NHS providers. DESIGN: Follow-up study with outcomes reported by patients three to six months after surgery. SETTING: 25 ISTCs and 72 NHS providers in England. Population Consecutive patients undergoing hip or knee replacement (5671 in ISTCs and 14,292 in NHS), inguinal hernia repair (640 and 2023, respectively), or surgery for varicose veins (248 and 1336, respectively). MAIN OUTCOMES: Symptoms and disability reported by patients (Oxford hip and knee scores on a 48 point scale; Aberdeen varicose vein questionnaire) and quality of life (EuroQol EQ-5D score). RESULTS: Patients in ISTCs were healthier than those in NHS providers, had less severe preoperative symptoms, and were more affluent, though the differences were small. With adjustment, patients undergoing joint replacements in NHS providers had poorer outcomes: difference of -1.7 (95% confidence interval -2.5 to -0.9) on the Oxford hip score and -0.9 (-1.6 to -0.2) on the Oxford knee score. They more often reported complications: odds ratio 1.3 (95% confidence interval 1.1 to 1.5) for hip and 1.4 (1.2 to 1.6) for knee. There were no significant differences in outcomes after surgery for hernia or varicose veins, except that NHS patients more often reported poor results after hernia repair (1.4, 1.0 to 1.9) and additional surgery after varicose vein surgery (2.8, 1.2 to 6.8). CONCLUSION: Patients undergoing surgery in ISTCs were slightly healthier and had less severe conditions than those undergoing surgery in NHS providers. Some outcomes were better in ISTCs, but differences were small compared with the impact ISTCs could have on the provision of elective services