7672098
Unitarity in Higher Dimensions and Gauge Unification
Unitarity of the 4d standard model is ensured by the conventional Higgs mechanism with a fundamental spin-0 Higgs boson, responsible for gauge boson mass-generations. On the contrary Kaluza-Klein (KK) compactification of extra spatial dimensions can geometrically realize the gauge boson mass generation without invoking a fundamental Higgs scalar. We reveal that massive gauge boson scattering in the compactified theories is unitary at low energies, and the unitarity violation is {\it delayed} to the intrinsic ultraviolet (UV) scale of the higher dimensional gauge theory. We demonstrate that this is a generic consequence of the ``geometric Higgs mechanism'' (GHM), manifested via Kaluza-Klein equivalence theorem (KK-ET). We further show that the presence of many gauge KK states below the UV cutoff scale imposes strong bounds on the highest KK level (N_KK). Applying these bounds to higher-dimensional SUSY GUTs implies that only a small number of KK states can be used to accelerate gauge coupling unification, and suggests that the GUT scale in the 5d minimal SUSY SU(5) is above 10^{14} GeV.
118551349
New Higgs Inflation in a No-Scale Supersymmetric SU(5) GUT
Higgs inflation is attractive because it identifies the inflaton with the electroweak Higgs boson. In this work, we construct a new class of supersymmetric Higgs inflationary models in the no-scale supergravity with an SU(5) GUT group. Extending the no-scale Kahler potential and SU(5) GUT superpotential, we derive a generic potential for Higgs inflation that includes the quadratic monomial potential and a Starobinsky-type potential as special limits. This type of models can accommodate a wide range of the tensor-to-scalar ratio $r = O(10^{-3}-10^{-1})$, as well as a scalar spectral index $n_s \sim 0.96$.
119248851
General Sum Rules for WW Scattering in Higgsless Models: Equivalence Theorem and Deconstruction Identities
We analyze inelastic 2{yields}2 scattering amplitudes for gauge bosons and Nambu-Goldstone bosons in deconstructed Higgsless models. Using the (KK) equivalence theorem in 4D (5D), we derive a set of general sum rules among the boson masses and multiboson couplings that are valid for arbitrary deconstructed models. Taking the continuum limit, our results naturally include the 5D Higgsless model sum rules for arbitrary 5D geometry and boundary conditions; they also reduce to the elastic sum rules when applied to the special case of elastic scattering. For the case of linear deconstructed Higgsless models, we demonstrate that the sum rules can also be derived from a set of general deconstruction identities and completeness relations. We apply these sum rules to the deconstructed 3-site Higgsless model and its extensions; we show that in 5D ignoring all higher KK modes (n>1) is inconsistent once the inelastic channels become important. Finally, we discuss how our results generalize beyond the case of linear Higgsless models.
73581246
Unitarity of deconstructed five-dimensional Yang–Mills theory
Abstract The low-energy properties of a compactified five-dimensional gauge theory can be reproduced in a four-dimensional theory with a replicated gauge group and an appropriate gauge symmetry breaking pattern. The lightest vector bosons in these “deconstructed” or “remodeled” theories have masses and couplings approximately equal to those of the Kaluza–Klein tower of massive vector states present in a compactified higher-dimensional gauge theory. We analyze the unitarity of low-energy scattering of the massive vector bosons in a deconstructed theory, and examine the relationship between the scale of unitarity violation and the scale of the underlying chiral symmetry breaking dynamics which breaks the replicated gauge groups. As in the case of compactified five-dimensional gauge theories, low-energy unitarity is ensured through an interlacing cancellation among contributions from the tower of massive vector bosons. We show that the behavior of these scattering amplitudes is manifest without such intricate cancellations in the scattering of the would-be Goldstone bosons of the deconstructed theory. Unlike compactified five-dimensional gauge theories, the amplitude for longitudinal vector boson scattering in deconstructed theories does grow with energy, though this effect is suppressed by 1/( N +1), with N +1 being the number of replicated gauge groups.
119518408
New Method for Detecting Charged Scalars at Colliders
We propose a new method for detecting a charged (pseudo)scalar at colliders, based upon the observation that its Yukawa coupling to charm and bottom quarks can be large due to a significant mixing of the top and charm quarks. After analyzing the typical flavor mixing allowed by low energy data in the topcolor and the generic two-Higgs doublet models, we study the physics potential of the Tevatron, LHC, and linear colliders for probing such an $s$-channel charged resonance via the single-top (as well as ${W}^{\ifmmode\pm\else\textpm\fi{}}{h}^{0}$) production. We show that studying its detection at colliders can also provide information on the dynamics of flavor-changing neutral current phenomena.
119496
The Equivalence theorem and its radiative correction - free formulation for all R(xi) gauges
The electroweak equivalence theorem quantitatively connects the physical amplitudes of longitudinal massive gauge bosons to those of the corresponding {ital unphysical} would-be Goldstone bosons. Its precise form depends on both the gauge-fixing condition and the renormalization scheme. Our previous modification-free schemes have applied to a broad class of R{sub {xi}} gauges including the `t Hooft{endash}Feynman gauge but excluding the Landau gauge. In this paper we construct a new renormalization scheme in which the radiative modification factor C{sub mod}{sup a} is equal to unity for all R{sub {xi}} gauges, including both `t Hooft{endash}Feynman and Landau gauges. This scheme makes C{sub mod}{sup a} equal to unity by specifying a convenient subtraction condition for the would-be Goldstone boson wave function renormalization constant Z{sub {phi}{sup a}}. We build the new scheme for both the standard model and the effective Lagrangian formulated electroweak theories (with either linearly or nonlinearly realized symmetry-breaking sector). Based upon these, a new prescription, called the {open_quotes}divided equivalence theorem,{close_quotes} is further proposed for extending the high energy region applicable to the equivalence theorem. {copyright} {ital 1997} {ital The American Physical Society}
55333370
The Annual Modulation Signature for Dark Matter: DAMA/LIBRA-Phase1 Results and Perspectives
The results obtained with the total exposure of 1.04 ton x yr collected by deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. during 7 annual cycles are summarized. The DAMA/LIBRA-phase1 and the former DAMA/NaI data (cumulative exposure 1.33 ton x yr, corresponding to 14 annual cycles) give evidence at 9.3 sigma C.L. for the presence of Dark Matter (DM) particles in the galactic halo, on the basis of the exploited model independent DM annual modulation signature by using highly radiopure NaI(Tl) target. The modulation amplitude of the single-hit events in the (2-6) keV energy interval is (0.0112 +/- 0.0012) cpd/kg/keV; the measured phase is (144 +/- 7) days and the measured period is (0.998 +/- 0.002) yr; values are in a good well in agreement with those expected for DM particles. No systematic or side reactions able to mimic the exploited DM signature have been found or suggested by anyone over more than a decade. Some of the perspectives of the presently running DAMA/LIBRA-phase2 are outlined.
7994047
INVESTIGATION ON LIGHT DARK MATTER
Some extensions of the Standard Model provide Dark Matter candidate particles with sub-GeV mass. These Light Dark Matter particles have been considered for example in Warm Dark Matter scenarios (e.g. the keV scale sterile neutrino, axino or gravitino). Moreover, MeV scale DM candidates have been proposed in supersymmetric models and as source of the 511 keV line from the Galactic center. In this paper the possibility of direct detection of a Light Dark Matter candidate is investigated considering the inelastic scattering processes on the electron or on the nucleus targets. Some theoretical arguments are developed and related phenomenological aspects are discussed. Allowed volumes and regions for the characteristic phenomenological parameters of the considered scenarios are derived from the DAMA/NaI annual modulation data.
122785032
RESULTS AND DEVELOPMENTS WITH LARGE MASS HIGHLY RADIOPURE NaI(Tl) AT LNGS
The low background DAMA/NaI experiment (' 100 kg highly radiopure NaI(Tl)) at the Gran Sasso National Laboratory of the I.N.F.N. had the unique feature to effectively investigate the presence of Dark Matter particle in the galactic halo by exploiting the model independent annual modulation signature. This experiment has collected data over seven annual cycles for a total exposure of more than 10 kg × day and has pointed out at 6.3 σ C.L. a modulation effect satisfying all the many peculiarities of the signature. Neither systematics nor side reactions able to account for the observed effect were found. Several (but still few with respect to the many possibilities) corollary model dependent quests for the candidate particle have also been carried out. At present the second generation DAMA/LIBRA set-up (' 250 kg highly radiopure NaI(Tl)) is in operation. A R&D towards possible ultimate 1 ton NaI(Tl) experiment is also in progress.
118902201
A Telescope to Detect VHE Gamma Ray Sources
123612926
DAMA/LIBRA results and perspectives
The DAMA/LIBRA experiment, running at the Gran Sasso National Laboratory of the I.N.F.N. in Italy, has a sensitive mass of about 250 kg highly radiopure NaI(Tl). It is mainly devoted to the investigation of Dark Matter (DM) particles in the Galactic halo by exploiting the model independent DM annual modulation signature. The present DAMA/LIBRA experiment and the former DAMA/NaI one (the first generation experiment having an exposed mass of about 100 kg) have released so far results corresponding to a total exposure of 1.17 ton × yr over 13 annual cycles. They provide a model independent evidence of the presence of DM particles in the galactic halo at 8.9 � C.L.. A short summary of the obtained results is presented and future perspectives of the experiment mentioned.