arXiv subjects

Yasaman Farzan

Publications and source records attributed to Yasaman Farzan.

78 records · Page 5Linked to original sources

arXiv2006

Reconciling large CP-violating phases with bounds on the electric dipole moments in the MSSM

The possibility of cancelation between different contributions to d_e, d_n and d_{Hg} has been reconsidered with special emphasis on the region that is phenomenologically interesting (intermediate values of \tan βand sub-TeV sfermion masses). It is found that in the range favored by electroweak baryogenesis (\it i.e., |μ|\simeq M_1 or |μ|\simeq M_2), \sin [θ_μ+θ_{M_1}]\sim 1 can be compatible with the EDM bounds even for slepton masses below 500 GeV. Such large values of the phases promise a successful electroweak baryogenesis. The possibility of large CP-odd effects at linear collider has also been discussed.

hep-ph↗

arXiv2005

On Effects of the Large Neutrino B-Term on Low Energy Physics

To embed the seesaw mechanism in the MSSM, two or three right-handed neutrino supermultiplets, $N_i$, have to be added to the model. In this framework, the supersymmetry breaking potential will include a new term called neutrino $B$-term: $MB_ν\tilde{N} \tilde{N}/2$. In this talk, we present a toy model that generates a large neutrino $B$-term keeping other supersymmetry breaking parameters small. We then review the consequences of having a large neutrino $B$-term on the electroweak symmetry breaking parameters and electric dipole moments (EDMs) of elementary particles.

hep-ph↗

arXiv2005

Effects of the neutrino B-term on the Higgs mass parameters and electroweak symmetry breaking

To embed the seesaw mechanism in the MSSM, two or three right-handed neutrino supermultiplets, $N_i$, have to be added to the model. In the presence of these new superfields, the soft supersymmetry breaking potential includes a lepton number violating mass term which is known as the neutrino $B$-term, $M B_ν\tilde{N}\tilde{N}/2$. In this paper, we study the effects of $B_ν$ on the Higgs mass parameters. Using the condition for the electroweak symmetry breaking, we derive an upper bound on $B_ν$ which is two orders of magnitude stronger than the previous bounds. We also propose a simple model in which it is natural to have large values of $B_ν$ while the rest of the supersymmetry breaking terms are at the TeV scale or smaller.

hep-ph↗

arXiv2004

The Contribution from Neutrino Yukawa Couplings to Lepton Electric Dipole Moments

To explain the observed neutrino masses through the seesaw mechanism, a supersymmetric generalization of the Standard Model should include heavy right-handed neutrino supermultiplets. Then the neutrino Yukawa couplings can induce CP violation in the lepton sector. In this paper, we compute the contribution of these CP violating terms to lepton electric dipole moments. We introduce a new formalism that makes use of supersymmetry to expose the GIM cancellations. In the region of small tan beta, we find a different result from that given previously by Ellis, Hisano, Raidal, and Shimizu. We confirm the structure found by this group, but with a much smaller overall coefficient. In the region of large tan beta, we recompute the leading term that has been identified by Masina and confirm her result.We discuss the implications of these results for constraints on the neutrino Yukawa couplings.

hep-ph↗

arXiv2004

Effects of the Neutrino B-term on Slepton Mixing and Electric Dipole Moments

The supersymmetric standard model with right-handed neutrino supermultiplets generically contains a soft supersymmetry breaking mass term: $δL ={1 \over 2} B_νM\tildeν_R \tilde ν_R$. We call this operator the "neutrino $B$-term". We show that the neutrino $B$-term can give the dominant effects from the neutrino sector to lepton flavor violating processes and to lepton electric dipole moments.

hep-ph↗

arXiv2003

Bounds on the Coupling of the Majoron to Light Neutrinos from Supernova Cooling

We explore the role of Majoron ($J$) emission in the supernova cooling process, as a source of upper bound on neutrino-Majoron coupling. We show that the strongest upper bound on the coupling to $ν_e$ comes from the $ν_eν_e \to J $ process in the core of a supernova. We also find bounds on diagonal couplings of the Majoron to $ν_{μ(τ)}ν_{μ(τ)}$ and on off-diagonal $ν_e ν_{μ(τ)}$ couplings in various regions of the parameter space. We discuss the evaluation of the cross-section for four-particle interactions ($νν\to JJ$ and $νJ \to νJ$). We show that these are typically dominated by three-particle sub-processes and do not give new independent constraints.

hep-ph↗