Anapole moment of the lightest neutralino in the cMSSM

We study the anapole moment of the lightest neutralino in the constrained Minimal Supersymmetric Standard Model (cMSSM). The electromagnetic anapole is the only allowed electromagnetic form factor for Majorana fermions, such as the neutralino. Since the neutralino is the LSP in many versions of the MSSM and therefore a candidate for dark matter, its characterization through its electromagnetic properties is important both for particle physics and for cosmology. We perform a scan in the parameter space of the cMSSM and find that the anapole moment is different from zero albeit very small ($< 10^{-3}$ GeV$^{-2}$). Combined with experimental constraints like the Higgs mass and the DM relic density, the allowed region of parameter space lies within the reach of future direct DM searches. Thus, the anapole moment could be used as a complementary constraint when studying the parameter space of the cMSSM and other similar models.Comment: 22 pages, 13 figures. arXiv admin note: substantial text overlap with arXiv:1206.505

From Veltman's conditions to Finite Unification

First we review Veltman's suggestion to attack the naturalness problem in the Standard model by requiring absence of quadratic divergences and the resulting mass formula. Then we emphasise the influence of Veltman's suggestion in strengthening the belief that supersymmetry is the natural playground for solving the problem of quadratic divergences. Going further, we recall few sporadic suggestions concerning the cancellation of the logarithmic divergences too, which in the framework of supersymmetry has led to the construction of all-loop Finite Theories with the use of the idea of reduction of couplings. Eventually, we concentrate on a specific Finite Unified Theory and its successful predictions for the top and Higgs mass, among others, and the prospects of its final justification in future collider searches.Comment: 27 pages, 4 figures; Invited contribution to the special volume of Acta Physical Polonica to honour the memory of Martinus Veltma

B-L Model with S3{\bf S}_{3} Symmetry: Nearest Neighbor Interaction Textures and Broken μ↔τ\mu\leftrightarrow\tau Symmetry

We make a scalar extension of the B-L gauge model where the ${\bf S}_{3}$ non-abelian discrete group drives mainly the Yukawa sector. Motived by the large and small hierarchies among the quark and active neutrino masses respectively, the quark and lepton families are not treated on the same footing under the assignment of the discrete group. As a consequence, the Nearest Neighbor Interactions (NNI) textures appear in the quark sector, leading to the CKM mixing matrix, whereas in the lepton sector, a soft breaking of the $\mu \leftrightarrow \tau$ symmetry in the effective neutrino mass that comes from type I see-saw mechanism, provides a non-maximal atmospheric angle and a non-zero reactor angle.Comment: 20 pages, 6 figures. Improved version and scalar discussion extended and references added. Version published in EPJ

Entropy considerations in constraining the mSUGRA parameter space

We explore the use of two criteria to constraint the allowed parameter space in mSUGRA models. Both criteria are based in the calculation of the present density of neutralinos as dark matter in the Universe. The first one is the usual ``abundance'' criterion which is used to calculate the relic density after the ``freeze-out'' era. To compute the relic density we used the numerical public code micrOMEGAs. The second criterion applies the microcanonical definition of entropy to a weakly interacting and self-gravitating gas evaluating then the change in the entropy per particle of this gas between the ``freeze-out'' era and present day virialized structures. An ``entropy-consistency'' criterion emerges by comparing theoretical and empirical estimates of this entropy. The main objective of our work is to determine for which regions of the parameter space in the mSUGRA model are both criteria consistent with the 2$\sigma$ bounds according to WMAP for the relic density: $0.0945<\Omega_{CDM}h^2<0.1287$. As a first result, we found that for $A_0=0$, sgn$\mu=+$, small values of tan$\beta$ are not favored; only for tan$\beta\simeq50$ are both criteria significantly consistent.Comment: 5 pages, 1 figure. To appear in the Proceedings of X Mexican Workshop on Particles and Fields, Morelia Michoac\'an, M\'exico, November 7-12, 200

Probing Unified Theories with Reduced Couplings at Future Hadron Colliders

The search for renormalization group invariant relations among parameters to all orders in perturbation theory constitutes the basis of the reduction of couplings concept. Reduction of couplings can be achieved in certain $N=1$ supersymmetric Grand Unified Theories and few of them can become even finite at all loops. We review the basic idea, the tools that have been developed as well as the resulting theories in which successful reduction of couplings has been achieved so far. These include: (i) a reduced version of the minimal $N = 1$ $SU(5)$ model, (ii) an all-loop finite $N = 1$ $SU(5)$ model, (iii) a two-loop finite $N = 1$ $SU(3)^3$ model and finally (vi) a reduced version of the Minimal Supersymmetric Standard Model. In this paper we present a number of benchmark scenarios for each model and investigate their observability at existing and future hadron colliders. The heavy supersymmetric spectra featured by each of the above models are found to be beyond the reach of the 14 TeV HL-LHC. It is also found that the reduced version of the MSSM is already ruled out by the LHC searches for heavy neutral MSSM Higgs bosons. In turn the discovery potential of the 100 TeV FCC-hh is investigated and found that large parts of the predicted spectrum of these models can be tested, but the higher mass regions are beyond the reach even of the FCC-hh.Comment: 30 pages, 9 figures; references added, typos corrected, CDM arguments added in sections 3,5,6,7 and

Axial Couplings on the World-Line

We construct a world-line representation for the fermionic one-loop effective action with axial and also vector, scalar, and pseudo-scalar couplings. We use this expression to compute a few selected scattering amplitudes. These allow us to verify that our method yields the same results as standard field theory. In particular, we are able to reproduce the chiral anomaly. Our starting point is the second-order formulation for the Dirac fermion. We translate the second order expressions into a world-line action.Comment: 12 pages, LaTeX 2e with array and epsf packages, Postscript figures. Submitted to Phys. Lett. B. Minor corrections, fixed a number of typo

Perturbative Unification of Soft Supersymmetry--Breaking Terms

Perturbative unification of soft supersymmetry--breaking (SSB) parameters is proposed in Gauge-Yukawa unified models. The method, which can be applied in any finite order in perturbation theory, consists in searching for renormalization group invariant relations among the SSB parameters, which are consistent with perturbative renormalizability. For the minimal Gauge-Yukawa unified model based on $SU(5)$ we find that the low energy SSB sector contains a single arbitrary parameter, the unified gaugino mass. Within a certain approximation we find that the model predicts a superpartner spectrum which is consistent with the experimental data.Comment: 14 page

Gauge-Yukawa Unification in Asymptotically Non-free Theories

We study asymptotically non-free gauge theories and search for renormalization group invariant (i.e. technically natural) relations among the couplings which lead to successful gauge-Yukawa unification. To be definite, we consider a supersymmetric model based on $SU(4)\times SU(2)_{R}\times SU(2)_{L}$. It is found that among the couplings of the model, which can be expressed in this way by a single one in the lowest order approximation, are the tree gauge couplings and the Yukawa coupling of the third generation. The corrections to the lowest order results are computed, and we find that the predictions on the low energy parameters resulting from those relations are in agreement with the measurements at LEP and Tevatron for a certain range of supersymmetry breaking scale.Comment: 15 pages, MPI-Ph/94-46, HD-THEP-94-33, NTUA.12/94, KANAZAWA-94-1

Yukawa Couplings for the Spinning Particle and the World Line Formalism

We construct the world-line action for a Dirac particle coupled to a classical scalar or pseudo-scalar background field. This action can be used to compute loop diagrams and the effective action in the Yukawa model using the world-line path-integral formalism for spinning particles.Comment: 10 pages Latex, two uuencoded postscript figures. Note added at the en