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 3P1^3P_1 Quarkonium

We analyse inclusive photoproduction of polarized $^3P_1$ 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 $v$, 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 $v$ 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 3PJ^3P_J Quarkonium

The functions of the gluon fragmentation into $^3P_J$ quarkonium are calculated to order $\alpha_s^2$. 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 $P$-wave quarkonia, is treated correctly in the case of fragmentation functions. The obtained fragmentation functions satisfy explicitly at the order of $\alpha_s^2$ the Altarelli-Parisi equation and when $z\rightarrow 0$ they behave as $z^{-1}$ 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 b→sγb\to s\gamma and μ→eγ\mu\to e\gamma in supersymmetric SO(10) grand unification

We compare the branching ratios for $b\rightarrow s\gamma$ and $\mu\rightarrow e\gamma$ 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 $\tan\beta =2$ and the other one with large $\tan\beta$ having third generation Yukawa coupling unification at the GUT scale. \newline\indent We show that for small $\tan\beta$ the branching ratio constraints allow only a smaller region of parameter space for $\mu>0$ compared to $\mu<0$ for gluino mass \alt 500 GeV. With large $\tan\beta$, we find acceptable regions of parameter space with \left|\mu \right|\alt 1 TeV only for $\mu<0$. The dominant constraint on large $\tan\beta$ with $\mu >0$ parameter space is found to be given by the $b\rightarrow s\gamma$ branching ratio, while for large $\tan\beta$ with $\mu <0$ it is found to be given by the $\mu\rightarrow e\gamma$ branching ratio. In many of these acceptable regions, we find that the $\mu\rightarrow e\gamma$ 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 $b\rightarrow s\gamma$ can not be ignored in some regions of parameter space, especially for large $\tan\beta$ 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 $b-\tau$ 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