40 research outputs found
CP Violation in Fourth Generation Quark Decays
We show that, if a fourth generation is discovered at the Tevatron or LHC,
one could study CP violation in b' \to s decays. Asymmetries could reach 30%
for b'\to sZ for m_{b'} \lesssim 350 GeV, while it could be greater than 50%
for b'\to s\gamma and extend to higher m_{b'}. Branching ratios are
10^{-3}--10^{-5}, and CPV measurement requires tagging. Once measured, however,
the CPV phase can be extracted with little theoretical uncertainty.Comment: 4 pages, 7 eps figure
h\to \gamma \gamma In Inert Higgs Doublet Model
Motivated by the recent result reported from LHC on the di-photon search for
a Standard Model (SM) Higgs-like boson. We discuss the implications of this
possible signal in the framework of the Inert Higgs Doublet Model (IHDM),
taking into account previous limits from Higgs searches at LEP, the Tevatron
and the LHC as well as constraints from unitarity, vacuum stability and
electroweak precision tests. We show that the charged Higgs contributions can
interfere constructively or destructively with the W gauge bosons loops leading
to enhancement or suppression of the di-photon rate with respect to SM rate. We
show also that the invisible decay of the Higgs, if open, could affect the
total width of the SM Higgs boson and therefore suppress the di-photon rate.Comment: 15 pages, added reference
Third generation sfermions decays into Z and W gauge bosons: full one-loop analysis
The complete one-loop radiative corrections to third generation scalar
fermions into gauge bosons Z and W^\pm is considered. We focus on \wt{f}_2 \to
Z \wt{f}_1 and \wt{f}_i \to W^\pm \wt{f'}_j (f,f'=t,b). We include both
SUSY-QCD, QED and full electroweak corrections. It is found that the
electroweak corrections can be of the same order as the SUSY-QCD corrections.
The two sets of corrections interfere destructively in some region of parameter
space. The full one loop correction can reach 10% in some SUGRA scenario, while
in model independent analysis like general MSSM, the one loop correction can
reach 20% for large \tan\beta and large trilinear soft breaking terms A_b.Comment: Latex file, 18 pages, 8 figures, version to appear in PR
Probing triple Higgs couplings of the Two Higgs Doublet Model at Linear Collider
We study double Higgs production at the future Linear Collider in the
framework of the Two Higgs Doublet Models through the following channels:
, . All these
processes are sensitive to triple Higgs couplings. Hence observations of them
provide information on the triple Higgs couplings that help reconstructing the
scalar potential. We also discuss the double Higgs-strahlung in the decoupling limit where mimics the SM Higgs boson. The
processes and are also discussed
in the fermiophobic limit where distinctive signatures such as ,
and are expected in the Type-I Two Higgs Doublet
Model.Comment: 21 pages and 9 figures; one figure and some discussions added,
version to appear in PR
Sums over Graphs and Integration over Discrete Groupoids
We show that sums over graphs such as appear in the theory of Feynman
diagrams can be seen as integrals over discrete groupoids. From this point of
view, basic combinatorial formulas of the theory of Feynman diagrams can be
interpreted as pull-back or push-forward formulas for integrals over suitable
groupoids.Comment: 27 pages, 4 eps figures; LaTeX2e; uses Xy-Pic. Some ambiguities
fixed, and several proofs simplifie
Radiative corrections to scalar-fermion pair production in high energy e+e- collisions
We study the one-loop radiative corrections to pair production of the
supersymmetric scalar partners of the standard fermions in e+e- annihilation.
Both electroweak and SUSY-QCD corrections are considered. Applications are for
production of scalar fermions of the third generation, e^+e^-\to \wt{f}_i
\wt{f}_j^* (i,j=1,2), , as well as for production of scalar
quarks of the first and second generation. Effects on integrated cross sections
are discussed and also the one-loop induced forward-backward asymmetries are
studied. It is found that at low energy, \sqrt{s}\approx 500 \to 1000 GeV, the
corrections are dominated by the QCD contributions, At high energy,
TeV, the electroweak box diagrams give a substantial
contribution and even dominate in some regions of parameters space. The purely
loop-induced forward-backward asymmetry can reach values of several per cent.Comment: 23 pages, latex, 13 figure
Developing countries and neglected diseases: challenges and perspectives
It is now commonly admitted that the so-called (most) neglected tropical diseases have been given little attention. According to World Health Organization, neglected diseases are hidden diseases as they affect almost exclusively extremely poor populations living in remote areas beyond the reach of health service. The European Parliament recognised that, to our shame, Neglected Diseases have not received the attention they deserve from EU actions. In the Millennium Development Goals they were given very little attention and mentioned just as other disease. Investing in drugs for these diseases is thought to be not marketable or profitable. However, despite their low mortality, neglected diseases are causing severe and permanent disabilities and deformities affecting approximately 1 billion people in the world, yielding more than 20 millions of Disability Adjusted Life Years (56.6 million according to Lancet's revised estimates) and important socio-economic losses. Urgent pragmatic and efficient measures are needed both at international and national levels
Window on Higgs Boson: Fourth Generation Decays Revisited
Direct and indirect searches of the Higgs boson suggest that 113 GeV
170 GeV is likely. With the LEP era over and the
Tevatron Run II search via arduous, we revisit a case where
or jets could arise via strong pair
production. In contrast to 10 years ago, the tight electroweak constraint on
-- (hence --) splitting reduces FCNC
, rates, making naturally competitive.
Such a "cocktail solution" is precisely the mix that could evade the CDF search
for , and the 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.
CP-odd A^0 production at e^+e^- colliders in MSSM with CP violating phases
We study the production of a heavy CP-odd boson in association with a
photon and a Z boson as well as the
single production of via in the MSSM
with CP violating phases. In the case of , we show
that the squark contribution, which vanishes in the MSSM with real parameters,
turns out to be sizeable in presence of CP violating phases in the soft SUSY
parameters. For in both the 2HDM and MSSM
with real parameters, the cross section does not reach observable rates at a
NLC. It is found that with a large CP violating phase for , cross sections
of the order 0.1 fb are attainable for all the processes ,
and .Comment: 12 pages, latex, 7 eps figures. One new figure, new discussion arroud
it. Version to appear in Phys. Rev.
Higgs boson enhancement effects on squark-pair production at the LHC
We study the Higgs boson effects on third-generation squark-pair production
in proton-proton collision at the CERN Large Hadron Collider (LHC), including
\Stop \Stop^*, \Stop\Sbot^*, and \Sbot \Sbot^*. We found that substantial
enhancement can be obtained through s-channel exchanges of Higgs bosons at
large , at which the enhancement mainly comes from , , and initial states. We compute the complete set of electroweak
(EW) contributions to all production channels. This completes previous
computations in the literature. We found that the EW contributions can be
significant and can reach up to 25% in more general scenarios and at the
resonance of the heavy Higgs boson. The size of Higgs enhancement is comparable
or even higher than the PDF uncertainties and so must be included in any
reliable analysis. A full analytical computation of all the EW contributions is
presented.Comment: 23 pages, 7 figures, 1 tabl