arXiv subjects

Savas Dimopoulos

Publications and source records attributed to Savas Dimopoulos.

65 records · Page 4Linked to original sources

arXiv1996

Sparticle Spectroscopy and Electroweak Symmetry Breaking with Gauge-Mediated Supersymmetry Breaking

The phenomenology associated with gauge-mediated supersymmetry breaking is presented. A renormalization group analysis of the minimal model is performed in which the constraints of radiative electroweak symmetry breaking are imposed. The resulting superpartner and Higgs boson spectra are highly correlated and depend on only a few parameters. Superpartner mass ratios and sum rules are identified which can be tested at future colliders. Some of these relations are logarithmically sensitive to the messenger scale, while others allow gauge-mediation to be distinguished from other schemes for tansmitting supersymmetry breaking. Deviations from the minimal model, such as larger messenger representations and additional contributions to Higgs sector masses, can in some circumstances dramatically modify the low energy spectrum. These modifications include a slepton or Higgsino as the lightest standard model superpartner, or exotic mass relations among the scalars and gauginos. The contribution to $b \to s γ$ and resulting bound on superpartner masses are also presented for the minimal model. Finally, the unique collider signatures of heavy charged particle production, or decay to the Goldstino within a detector are discussed.

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arXiv1996

Phenomenological Implications of Low Energy Supersymmetry Breaking

The experimental signatures for low energy supersymmetry breaking are presented. The lightest standard model superpartner is unstable and decays to its partner plus a Goldstino, $G$. For a supersymmetry breaking scale below a few 1000 TeV this decay can take place within a detector, leading to very distinctive signatures. If a neutralino is the lightest standard model superpartner it decays by $χ_1^0 \to γ+ G$, and if kinematically accessible by $χ_1^0 \to (Z^0, h^0, H^0, A^0) + G$. These decays can give rise to displaced vertices. Alternately, if a slepton is the lightest standard model superpartner it decays by $\tilde{l} \to l + G$. This can be seen as a greater than minimum ionizing charged particle track, possibly with a kink to a minimum ionizing track.

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arXiv1996

Implications of Low Energy Supersymmetry Breaking at the Tevatron

The signatures for low energy supersymmetry breaking at the Tevatron are investigated. It is natural that the lightest standard model superpartner is an electroweak neutralino, which decays to an essentially massless Goldstino and photon, possibly within the detector. In the simplest models of gauge-mediated supersymmetry breaking, the production of right-handed sleptons, neutralinos, and charginos leads to a pair of hard photons accompanied by leptons and/or jets with missing transverse energy. The relatively hard leptons and softer photons of the single $e^+e^- γγ+ \EmissT$ event observed by CDF implies this event is best interpreted as arising from left-handed slepton pair production. In this case the rates for $l^{\pm} γγ+ \EmissT$ and $ γγ+ \EmissT$ are comparable to that for $l^+l^- γγ+ \EmissT$.

hep-ph↗

arXiv1996

Experimental Signatures of Low Energy Gauge Mediated Supersymmetry Breaking

The experimental signatures for gauge mediated supersymmetry breaking are presented. The phenomenology associated with this class of models is distinctive since the gravitino is naturally the LSP. The next lightest supersymmetric particle (NLSP) can be a gaugino, Higgsino, or right handed slepton. Decay of the NLSP to its partner plus the LSP proceeds through the Goldstino component of the gravitino. For a significant range of parameters this decay can take place within the detector, and can be measured as a displaced vertex or kink in a charged particle track. In the case that the NLSP is mostly gaugino, we identify the discovery modes as $e^+e^- \rightarrow γγ+ \Emiss$, and $p \bar{p} \rightarrow l^+ l^- γγ+ \EmissT$. If the NLSP is a right handed slepton the discovery modes are $e^+ e^- \rightarrow l^+ l^- + \Emiss$ and $p \bar{p} \rightarrow l^+ l^- + \EmissT$. An NLSP which is mostly Higgsino is also considered. Finally, these theories can contain scalar particles which mediate sub-millimeter range coherent forces of gravitational strength.

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arXiv1995

Dynamical Relaxation of the Supersymmetric CP Violating Phases

A supersymmetric generalization of the Peccei-Quinn mechanism is proposed in which two U(1) CP violating phases of the supersymmetric standard model are promoted to dynamical variables. This amounts to postulating the existence of spontaneously broken global symmetries in the supersymmetry breaking sector. The vacuum can then relax near a CP conserving point. As a consequence the strong CP and supersymmetric CP problems may be solved by similar mechanisms.

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arXiv1995

Superfield Derivation of the Low-Energy Effective Theory of Softly Broken Supersymmetry

We analyze the soft supersymmetry breaking parameters obtained in grand unified theories after integrating out the heavy GUT-states. The superfield formalism greatly simplifies the calculations and allows us to derive the low-energy effective theory in the general case of non-universal and non-proportional soft terms by means of a few Feynman diagrams. We find new contributions not considered before. We discuss the implications for the destabilization of the gauge hierarchy, flavor violating processes and the non-unification of sparticle masses in unified theories.

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arXiv1995

The Supersymmetric Flavor Problem

The supersymmetric $SU(3)\times SU(2)\times U(1)$ theory with minimal particle content and general soft supersymmetry breaking terms has 110 physical parameters in its flavor sector: 30 masses, 39 real mixing angles and 41 phases. The absence of an experimental indication for the plethora of new parameters places severe constraints on theories posessing Planck or GUT-mass particles and suggests that theories of flavor conflict with naturalness. We illustrate the problem by studying the processes $μ\rightarrow e + γ$ and $K^0 - \bar{K}^0$ mixing which are very sensitive probes of Planckian physics: a single Planck mass particle coupled to the electron or the muon with a Yukawa coupling comparable to the gauge coupling typically leads to a rate for $μ\rightarrow e + γ$ exceeding the present experimental limits. A possible solution is that the messengers which transmit supersymmetry breaking to the ordinary particles are much lighter than $M_{\rm Planck}$.

hep-ph↗

arXiv1995

NON-UNIFIED SPARTICLE AND PARTICLE MASSES IN UNIFIED THEORIES.

We give examples of minimal extensions of the simplest SU(5) SUSY-GUT in which all squarks and sleptons of a family have different tree level masses at the unification scale. This phenomenon is general; it occurs when the quarks and leptons are the light remnants of a theory which contains extra heavy families at the unification scale. The examples have interesting relations between Yukawa couplings: In one model the ratio of the top to bottom Yukawas is as large as $\simeq 3$, partly accounting for the large $m_t /m_b$. Another gives $m_b/m_τ$ between 2/3 and 1; this relaxes the strict bounds on the top mass and neutrino properties that come from $b$--$τ$ unification. Still another allows $ m_s/m_μ$ to be between 1/6 and 1 and evades the potentially problematic GUT relation of $m_s=m_μ$. The final example has horizontal sparticle splittings in spite of the existence of horizontal symmetries.

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arXiv1994

Supersymmetric Unification

The measured value of the weak mixing angle is, at present, the only precise experimental indication for physics beyond the Standard Model. It points in the direction of Unified Theories with Supersymmetric particles at accessible energies. We recall the ideas that led to the construction of these theories in 1981.

hep-ph↗

arXiv1992

Precise predictions for mt, Vcb and tan

The fermion mass and mixing angle predictions of a recently proposed framework are investigated for large b and $τ$ Yukawa couplings. A new allowed region of parameters is found for this large $\tan β$ case. The two predictions which are substantially altered, $m_t$ and $\tan β$, are displayed, including the dependence on the inputs $|V_{cb}|$, $m_c$, $m_b$ and $α_s$. A simple restriction on this framework yields an additional prediction, for $|V_{cb}|$. If the b,t, and $τ$ Yukawas are equal at the GUT scale then $|\Vcb|$ is predicted and the top quark mass is constrained to lie in the range $\mt = 179. \pm 4.$ GeV.

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arXiv1992

Predictions for neutral K and B meson physics

Using supersymmetric grand unified theories, we have recently invented a framework which allows the prediction of three quark masses, two of the parameters of the Kobayashi-Maskawa matrix and tan $β$, the ratio of the two vevs. These predictions are used to calculate $ε$ and $ε'$ in the kaon system, B meson mass mixing and the size of CP asymmetries in the decays of neutral B mesons to explicit final states of given CP.

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