International Journal of Modern Physics A

We explain the orbifold compactification in string models and present a Z_12−I orbifold compactification toward supersymmetric standard models. We also point out an effective R-parity from this string construction. The VEVs of gauge singlets are chosen such that phenomenological constraints are satisfied.

Non-critical String Cosmologies are offered as an alternative to Standard Big Bang Cosmology. The new features encompassed within the dilaton dependent non-critical terms affect the dynamics of the Universeś evolution in an unconventional manner being in agreement with the cosmological data. Non-criticality is responsible for a late transition to acceleration at redshifts z=0.2. The role of the uncoupled rolling dilaton to relic abundance calculations is discussed. The uncoupled rolling dilaton dilutes the neutralino relic densities in supersymmetric theories by factors of ten, relaxing considerably the severe WMAP Dark Matter constraints, while at the same time leaves almost unaffected the baryon density in agreement with primordial Nucleosynthesis.

Certain null singularities in ten dimensional supergravity have natural holographic duals in terms of Matrix Theory and generalizations of the AdS/CFT correspondence. In many situations the holographic duals appear to be well defined in regions where the supergravity develops singularities. We describe some recent progress in this area.

To realize massive pions, we study variations of the holographic model of massless QCD using the brane configuration proposed by Sakai and Sugimoto. We propose deformations which break the chiral symmetry explicitly and compute the mass of the pions and vector mesons. The observed value of the pion mass can be obtained. We also argue a chiral perturbation corresponding to our deformation.

We construct two distinct brane solutions in six dimensional effective field theory models. The CP¹ sigma model and the baby skyrmion realize warped compactification of the extra dimensions for negative bulk cosmological constant. Higher winding number solutions of the baby skyrmion are also presented.

Black hole production at the Large Hadron Collider (LHC) is an interesting consequence of TeV-scale gravity models. The predicted values, or lower limits, for the fundamental Planck scale and number of extra dimensions will depend directly on the accuracy of the black hole production cross-section. We give a range of lower limits on the fundamental Planck scale that could be obtained at LHC energies. In addition, we examine the effects of parton electric charge on black hole production using the trapped-surface approach of general relativity. Accounting for electric charge of the partons could reduce the black hole cross-section by one to four orders of magnitude at the LHC.

Using counterterm subtraction technique we calculate the action and other thermodynamical quantities for the general Kerr–AdS black hole in five dimensions. We show that the resulting thermodynamical quantities do satisfy the first law of thermodynamics upon choosing the non-rotating Einstein space as a boundary. Furthermore, the vacuum energies and conformal anomalies calculated from both sides of the AdS/CFT duality match exactly. Comparing this result to previous known results, one is lead to raise the question: why some choices of the boundary metric produce quantities that do not satisfy the first law? Answering such a question will help us understand the relevance of the AdS vacuum energy on the gravity side.

In the present work, it is shown that the problem of the accelerating expansion of the Universe can be directly solved by applying Einstein geometrization philosophy in a wider geometry. The geometric structure used to fulfil the aim of the work is a version of Absolute Parallelism geometry in which curvature and torsion are simultaneously non vanishing objects. It is shown that, while the energy corresponding to the curvature of space- time gives rise to an attractive force, the energy corresponding to the torsion indicates the presence of a repulsive force. A fine tuning parameter can be adjusted to give the observed phenomena.

Some recent work on the implications of a dilaton in 4d gauge theories are revisited. In part I of this paper we see how an effective dilaton coupling to gauge kinetic term provides a simple attractive mechanism to generate confinement. In particular, we put emphasis on the derivation of confining analytical solutions and look into the problem how dilaton degrees of freedom modify Coulom potential and when a confining phase occurs. In part II, we solve the semi-relativistic wave equation, for Dick interquark potential using the Shifted l-expansion technique (SLET) in the heavy quarkonium sector. The results of this phenomenological analysis proves that these effective theories can be relevant to model quark confinement and may shed some light on confinement mechanism.

I discuss the current status of inflationary cosmology in light of the recent WMAP 3-year data release. The basic predictions of inflation are all supported by the data. Inflation also makes predictions which are have not been well tested by current data but can be by future experiments, most notably a deviation from a scale-invariant power spectrum and the production of primordial gravitational waves. A scale-invariant spectrum is disfavored by current data, but not conclusively. Tensor modes are currently poorly constrained, and slow-roll inflation does not make an unambiguous prediction of the expected amplitude of primordial gravitational waves. A tensor/scalar ratio of r ≃ 0.01 is within reach of near-future measurements.

We present a general overview of recent results in the searches for dark matter and dark energy. We discuss the observation of the collision between two clusters of galaxies, and the impact this has on the relevance of dark matter. We then present the final results from microlensing experiments, which aimed at detecting dark baryonic objects in the halo of our galaxy, and the status of direct searches for WIMPs. We present the evidence for dark energy which initially comes from experiments dedicated to the study of distant type Ia supernovae. The measure of the baryon acoustic oscillation, an independent probe of the evolution of our universe that has recently brought interesting constraints, is finally described.

Inflationary models with a superheavy scale F-term hybrid inflation followed by an intermediate scale modular inflation are considered. The restrictions on the power spectrum of curvature perturbation and the spectral index n_s from the recent data within the power-law cosmological model with cold dark matter and a cosmological constant can be met provided that the number of e-foldings N_HI* suffered by the pivot scale k_* = 0.002/Mpc during hybrid inflation is suitably restricted. The additional e-foldings needed for solving the horizon and flatness problems are generated by modular inflation with a string axion as inflaton. For central values of and n_s, the grand unification scale comes out, in the case of standard hybrid inflation, close to its supersymmetric value M_GUT ≃ 2.86 × 10¹⁶GeV, the relevant coupling constant is relatively large (≈ 0.005 – 0.14), and 10 ≲ N_HI* ≲ 21.7. In the shifted [smooth] hybrid inflation case, the grand unification scale can be identified with M_GUT for N_HI* ≃ 21 [N_HI* ≃ 18].

Moduli with flat or run-away classical potentials are generic in theories based on supersymmetry and extra dimensions. They mix between themselves and with matter fields in kinetic terms and in the nonperturbative superpotentials. As the result, interesting structure appears in the scalar potential which helps to stabilise and trap moduli and leads to multi-field inflation. The new and attractive feature of multi-inflationary setup are isocurvature perturbations which can modify in an interesting way the final spectrum of primordial fluctuations resulting from inflation.

The LHC will have much to say about the mysteries of dark matter, and this talk reviews this potential within the context of supersymmetry (SUSY). The SUSY search reach of CMS and ATLAS is presented, followed by a brief introduction to the methods of SUSY parameter measurement. A representative ATLAS study is then used to explain how the LHC can be used to obtain a measurement of the relic density of a neutralino WIMP candidate. Finally, the prospect of success is considered by looking at different points in the MSSM parameter space.

The production and evolution of cosmological defects are investigated based on the standard particle physics theory such as the electroweak unified model and quantum chromodynamics. In these models, the string type solution can be obtained. Although electroweak strings and pion strings are embedded ones and topologically unstable, they would be stabilized by high temperature plasma and bring various cosmological consequences. Moreover, the production of pion strings may be observed in the LHC experiment.

We show that the Ω_b – Ω_DM coincidence can naturally be explained in a framework where axino is cold dark matter which is predominantly produced in nonthermal processes involving decays of Q-balls formed in Affleck-Dine baryogenesis. In this approach, the similarity of Ω_b and Ω_DM is a direct consequence of the (sub-)GeV scale of the mass of the axino, while the reheating temperature T_R must be low, some 10²GeV, or less.

D-brane realizations of the Standard Model predict extra abelian gauge fields which are superficially anomalous. The anomalies are cancelled via appropriate couplings to axions and Chern-Simons-like couplings. The presence of such couplings has dramatic experimental consequences: a) they provide masses to the anomalous abelian gauge fields (which masses can be of order of a few TeV), b) they provide new contributions to couplings like Z'-¿gammaZ, that may be considerable at LHC. This proceeding is mainely based on hep-th/0605225.

The impact of the brane cosmology on the relic density of non-relativistic stable particles in high and low reheating temperature scenarios is analyzed. We show that, in non-conventional brane cosmology, the dark matter relic density can be enhanced by many order of magnitudes.

I will describe a minimal supersymmetric SU(5) model, in which the adjoint multiplet breaks spontaneously both gauge and supersymmetry. This inevitably leads to intermediate scales, which in turn increase the GUT scale. The dimension 6 proton decay is thus suppressed, while soft terms coming from supergravity typically dominate.

After a short introduction about the flavour problem and the MFV hypothesis, we discuss B_u → τν and other low-energy observables in the framework of the MSSM with MFV, large tanβ, and heavy squarks . This scenario naturally satisfies all the electroweak precision constraints and, in the case of not too heavy slepton sector , can also easily accommodate the (g − 2)_μ anomaly. Within this framework, non-standard effects could possibly be detected in the near future in a few low-energy flavour-violating observables, such as , , , and . The possibility to further constrain this scenario using dark-matter constraints is also briefly discussed.

Talk based on work entitled “Yukawa textures, new physics and nondecoupling,” done in collaboration with G. C. Branco and J. I. Silva-Marcos, arXiv:hep-ph/0612252, to appear in Phys. Rev. D. In this work we pointed out that New Physics can play an important rôle in rescuing some of the Yukawa texture zero ansätze which would otherwise be eliminated by the recent, more precise measurements of V_CKM. We have shown that the presence of an isosinglet vector-like quark which mixes with standard quarks, can render viable a particularly interesting four texture zero Yukawa ansatz. The crucial point is the nondecoupling of the effects of the isosinglet quark, even for arbitrary large values of its mass.

The complementarity between the quark and lepton mixing matrices is shown to provide robust predictions. We obtain these predictions by first showing that the matrix V_M, product of the quark (CKM) and lepton (PMNS) mixing matrices, may have a zero (1,3) entry which is favored by experimental data.

We obtain that any theoretical model with a vanishing (1,3) entry of V_M that is in agreement with quark data, solar, and atmospheric mixing angle leads to . This value is consistent with the present 90% CL experimental upper limit. We also investigate the prediction on the lepton phases. We show that the actual evidence, under the only assumption that the correlation matrix V_M product of CKM and PMNS has a zero in the entry (1, 3), gives us a prediction for the three CP-violating invariants J, S₁, and S₂. A better determination of the lepton mixing angles will give stronger prediction for the CP-violating invariants in the lepton sector. These will be tested in the next generation experiments. Finally we compute the effect of non diagonal neutrino mass in l_i → l_jγ in SUSY theories with non trivial Quark-Lepton complementarity and a flavor symmetry. The Quark-Lepton complementarity and the flavor symmetry strongly constrain the theory and we obtain a clear prediction for the contribution to μ → eγ and the τ decays τ → eγ and τ → μγ. If the Dirac neutrino Yukawa couplings are degenerate but the low energy neutrino masses are not degenerate, then the lepton decays are related among them by the V_M entries. On the other hand, if the Dirac neutrino Yukawa couplings are hierarchical or the low energy neutrino masses are degenerate, then the prediction for the lepton decays comes from the CKM hierarchy.

We conduct a detailed analysis of the phenomenology of two predictive see-saw scenarios which lead to the Quark-Lepton Complementarity relation θ₁₂+θ_C = π/4. The neutrino mixing observables and their correlations, neutrinoless double beta decay, lepton flavor violating decays such as μ → eγ and leptogenesis are discussed. The features which allow to distinguish the scenarios are identified.

We present the phenomenology of the low scale U(1)_B–L extension of the standard model and its implications at LHC. We show that this model provides a natural explanation for the presence of three right-handed neutrinos and can naturally account the observed neutrino masses and mixing. We study the decay and production of the extra gauge boson and the SM singlet scalar (heavy Higgs) predicted in this type of models. We find that the cross sections of the SM-like Higgs production are reduced by ~ 20% – 30%, while its decay branching ratios remain intact. The extra Higgs has relatively small cross sections and the branching ratios of Z′ → l⁺l⁻ are of order ~ 20% compared to ~ 3% of the SM results.

In this talk, we investigate the implications of R-parity violating (RPV) operators in a model with family symmetry ¹. Family symmetry can determine the form of RPV operators as well as the Yukawa matrices. We consider a concrete model with non-abelian discrete symmetry Q₆, which has only three RPV trilinear operators with no baryon number violating terms. We find that ratios of decay rates of the lepton flavor violating processes are fixed thanks to the family symmetry, predicting .

Prospects for SUSY discoveries and measurements at future colliders LHC and ILC are discussed. The problem of reconstructing the underlying theory and SUSY breaking mechanism is also addressed.

Searches for the Higgs bosons of the Minimal Supersymmetric Standard Model are discussed at the LHC in the CMS and ATLAS experiments. Results are presented for the scenario which maximizes the mass of the lighter scalar Higgs boson. Low integrated luminosity is assumed.

We review some of the key 2006 measurements constraining the Unitarity Triangle and probing New Physics at B factory experiments BELLE and BABAR.

Fermilab operates the world's most intense antiproton source, now exclusively dedicated to serving the needs of the Tevatron Collider. The anticipated 2009 shutdown of the Tevatron presents the opportunity for a world-leading low- and medium-energy antiproton program. We summarize the status of the Fermilab antiproton facility and review physics topics for which a future experiment could make the world's best measurements.

The physics program of LHCb concerns the study of CP violation in the B system, including more precise determination of the CKM matrix parameters and in particular the determination of φ_s The search for new physics which could manifest itself indirectly will be a high priority. The main advantages of LHCb over the B factories are the access to the B_s system and very large B production rates. In addition, LHCb is a dedicated B physics experiment with excellent vertexing and particle identification capabilities. It is currently setting up its detector in its allocated LHC interaction region and is foreseen to be ready for data taking in November 2007 for the pilot run.

I summarize the observables constraining the mixing complex and present a new calculation of the element of the decay matrix. enters the prediction of the width difference ΔΓ_s, for which we obtain , if no new physics enters mixing. Applying our formulae to Tevatron data we find a deviation of the mixing phase φ_s from its Standard Model value by 2 standard deviations. I stress that present data do not give any information on the sign of ΔΓ_s.

By employing the QCD factorization approach, we calculated the new physics contributions to the two-body charmless hadronic decays B → M₁M₂ (M_i refers to light pseudo-scalar or vector light mesons) in the minimal supergravity (mSUGRA) model. In this talk we present the major numerical results and phenomenological discussions about these eighty decay channels.

We review the CP violation in the semileptonic |ΔS| = 1 τ-decays in supersymmetric extensions of the standard model (SM). We show that Within SUSY models with conserved R parity, the CP asymmetry of τ → kπν is below the current experimental limits, although it is enhanced by several order of magnitude than the SM results. We also study the impact of the lepton violation terms in SUSY models with R parity violation. We show that the CP asymmetry of τ-decay is enhanced significantly and the current experimental limits obtained by CLEO collaborations can be easily accommodated.

One loop mediated charged Higgs bosons decays H^± → W^±V, V = Z, γ are studied in the Minimal Supersymmetric Standard Model (MSSM) with and without CP violating phases. We evaluate the MSSM contributions to these processes taking into account B → X_sγ constraint as well as experimental constraints on the MSSM parameters. In the MSSM, we found that in the intermediate range of tan β ≲ 10 and for large A_t and large μ, where the lightest top squark becomes very light and hence non-decoupled, the branching ratio of H^± → W^±Z can be of the order 10⁻³ while the branching ratio of H^± → W^±γ is of the order 10⁻⁵. We found also that the CP violating phases of soft SUSY parameters can modify the branching ratio by about one order of magnitude. We also show that MSSM with CP violating phases lead to CP-violating asymmetry in the decays H⁺ → W⁺V and H⁻ → W⁻V. Such CP asymmetry can be rather large and can reach 80% in some region of parameter space.

The damping rates of ultrasoft quarks are determined in the context of next-to-leading order hard-thermal-loop summed perturbation of high-temperature QCD. Three types of divergent behavior are encountered: infrared, light-cone and at specific points determined by the gluon energies. Only the infrared divergence persists and is logarithmic.

I present here a concise review of the experimental results obtained at the Relativistic Heavy Ion Collider (RHIC), which shed light on the hot and dense quark gluon matter produced at these high temperature and density conditions.

Finite Unified Theories (FUTs) are N=1 supersymmetric Grand Unified Theories, which can be made all-loop finite, both in the gauge and Yukawa couplings and in the soft supersymmetry breaking sector. This remarkable property, based on the reduction of couplings at the quantum level, provides a drastic reduction in the number of free parameters, which in turn leads to predictions for the top and bottom quark masses, as well as predictions for the Higgs boson mass and the supersymmetric spectrum. Here we examine the predictions of two SU(5) FUTs, taking into account a number of theoretical and experimental constraints. We show how the phenomenological constraints can discriminate among the two models, and we give also the above mentioned predictions for the model that complies with all the constraints.

A new morphological boundary detection approach is used to separate the signal from the background in the Standard Model Higgs boson search at LHC. Based on mathematical concepts, this method consists of a fast computation of probabilistic density functions of events and a smoothing using a combination of dilatation and erosion operators. In a binary search approach, the performances are improved and the results compare favourably with other multivariate analysis.

We point out the production of the charginos and neutralinos in electron-electron process in several supersymmetric models, in order to show that the International Linear Collider can discover double charged charginos if these particles really exist in nature.