3,900 research outputs found
Neutrino Mass, Dark Matter, and Leptogenesis
It is proposed that dark matter is the origin of neutrino mass, thereby
linking inexorably two undisputed (and seemingly unrelated) pieces of evidence
for physics beyond the Standard Model. Leptogenesis at the TeV scale may also
be possible, as well as a measurable contribution to the muon anomalous
magnetic moment.Comment: 7 pages, 2 figure
Inclusive Photoproduction of Polarized Quarkonium
We analyse inclusive photoproduction of polarized quarkonium in the
framework of QCD. To separate nonperturbative and perturbative parts in the
density matrix of the produced quarkonium we use a method , which is equivalent
to the diagramatic expansion widely used in analysing deeply inelastic
scatterings. A systematic expansion in a small velocity , with which a heavy
quark moves inside the quarkonium in its rest frame, is performed for the
nonperturbative parts, and they are expressed as matrix elements in
nonrelativistic QCD. At the leading order of there are four matrix elements
representing nonperturbative physics. The perturbative parts are calculated at
the leading order of coupling constants. Some numerical results, especially,
numerical results for HERA are given.Comment: 19 pages+7 Figures as one compressed and encoded postcript fil
Calculating Fragmentation Functions from Definitions
Fragmentation functions for hadrons composed of heavy quarks are calculated
directly from the definitions given by Collins and Soper and are compared with
those calculated in another way. A new fragmentaion function for a P-wave meson
is also obtained and the singularity arising at the leading order is discussed.Comment: Preptint UM-P-94/01, 12 pages, 2 pages with Figures can be sent on
request. Using Plain Te
Gluon Fragmentation into Quarkonium
The functions of the gluon fragmentation into quarkonium are
calculated to order . With the recent progress in analysing
quarkonium systems in QCD we show explicitly how the socalled divergence in the
limit of the zero-binding energy, which is related to -wave quarkonia, is
treated correctly in the case of fragmentation functions. The obtained
fragmentation functions satisfy explicitly at the order of the
Altarelli-Parisi equation and when they behave as as
expected. Some comments on the previous results are made.Comment: Type-errors in the text and equations are eliminated. Several
sentences are added in Sect.4. The file is compressed and uuencoded (E-Mail
contact [email protected]
Mutual cosideration of and in supersymmetric SO(10) grand unification
We compare the branching ratios for and
in terms of constraining the parameter space in
supersymmetric SO(10) grand unification models where supersymmetry is broken
softly near the Planck scale by generationally symmetric operators. We observe
two general cases. One with small and the other one with large
having third generation Yukawa coupling unification at the GUT
scale. \newline\indent We show that for small the branching ratio
constraints allow only a smaller region of parameter space for compared
to for gluino mass \alt 500 GeV.
With large , we find acceptable regions of parameter space with
\left|\mu \right|\alt 1 TeV only for . The dominant constraint on
large with parameter space is found to be given by the
branching ratio, while for large with it is found to be given by the branching ratio. In
many of these acceptable regions, we find that the
branching ratio is predicted to be within one order of magnitude of its current
experimental bound. We also show that the usually neglected gluino mediated
diagrams in can not be ignored in some regions of
parameter space, especially for large scenarios when the gluino
mass is near its lower experimental bound.Comment: 14 pages (Latex), 4 PS figs (uuencoded, epsf.tex), slight
modification in text, as to appear in Physics Letters
Effects of an intermediate scale in SUSY grand unification
We discuss the production of lepton flavor violation and EDMs and the
viability of the unification hypothesis in SUSY grand unification with
an intermediate gauge symmetry breaking scale.Comment: 3 pages (Latex, esprc2.sty used), talk given at 4th International
Conference on Supersymmetry (SUSY '96, College Park, MD, May 29 - June 1,
1996
Dark Scalar Doublets and Neutrino Tribimaximal Mixing from A_4 Symmetry
In the context of A_4 symmetry, neutrino tribimaximal mixing is achieved
through the breaking of A_4 to Z_3 (Z_2) in the charged-lepton (neutrino)
sector respectively. The implied vacuum misalignment of the (1,1,1) and (1,0,0)
directions in A_4 space is a difficult technical problem, and cannot be treated
without many auxiliary fields and symmetries (and perhaps extra dimensions). It
is pointed out here that an alternative scenario exists with A_4 alone and no
redundant fields, if neutrino masses are "scotogenic", i.e. radiatively induced
by dark scalar doublets as recently proposed.Comment: 8 pages, 2 figures, 1 reference and 1 paragraph adde
Tri-bimaximal Neutrino Mixing and Quark Masses from a Discrete Flavour Symmetry
We build a supersymmetric model of quark and lepton masses based on the
discrete flavour symmetry group T', the double covering of A_4. In the lepton
sector our model is practically indistinguishable from recent models based on
A_4 and, in particular, it predicts a nearly tri-bimaximal mixing, in good
agreement with present data. In the quark sector a realistic pattern of masses
and mixing angles is obtained by exploiting the doublet representations of T',
not available in A_4. To this purpose, the flavour symmetry T' should be broken
spontaneously along appropriate directions in flavour space. In this paper we
fully discuss the related vacuum alignment problem, both at the leading order
and by accounting for small effects coming from higher-order corrections. As a
result we get the relations: \sqrt{m_d/m_s}\approx |V_{us}| and
\sqrt{m_d/m_s}\approx |V_{td}/V_{ts}|.Comment: 27 pages, 1 figure; minor correction
SU(5) Completion of the Dark Scalar Doublet Model of Radiative Neutrino Mass
Adding a second scalar doublet (eta^+,eta^0) and three neutral singlet
fermions N_{1,2,3} to the Standard Model of particle interactions with a new
Z_2 symmetry, it has been shown that eta^0_R or eta^0_I is a good dark-matter
candidate and seesaw neutrino masses are generated radiatively. A minimal
extension of this new idea is proposed to allow for its SU(5) completion.
Supersymmetric unification is then possible, and leptoquarks of a special kind
are predicted at the TeV scale.Comment: 6 pages, 2 figures, 1 tabl
Revelations of the E_6/U(1)_N Model: Two-Loop Neutrino Mass and Dark Matter
The E_6/U(1)_N gauge extension of the Supersymmetric Standard Model, first
proposed by Ma, is shown to have exactly the requisite ingredients to realize
the important new idea that dark matter is the origin of neutrino mass. With
the implementation of a discrete Z_2 X Z_2 symmetry, and particle content given
by three {27} representations of E_6, neutrino masses are naturally generated
in two loops, with candidates of dark matter in the loops. All particles of
this model are expected to be at or below the TeV scale, allowing them to be
observable at the LHC.Comment: 10 pages, 3 figure
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